Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-07-12
2003-01-21
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S231000, C525S238000, C525S241000, C428S332000, C428S338000, C428S339000
Reexamination Certificate
active
06509419
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to novel polymer blends for manufacturing breathable and environmentally stable water weakenable disposable films, fibers and articles and the methods for making those blends. Particularly, the present invention relates to breathable, environmentally stable water weakenable polymer blends capable of imparting breathable and environmentally stable water weakenable films, fibers, and articles with improved stability and enhanced strength when exposed to environmental conditions of increased humidity and elevated temperature.
BACKGROUND OF THE INVENTION
Disposable products are a great convenience and provide the benefit of one time, sanitary use. Such products can be useful for applications including, but not limited to, personal care items, diapers and training pants, feminine care products, adult incontinence products, hospital garments, wound care products, hospital bed linens, surgical fabrics, medical fabrics, and the like. However, there is concern about the disposal of these products because of traditional disposal methods. For instance, incineration of these products is not desirable because of increasing concerns about air quality, and the costs and difficulties associated with separating these products from other disposed, non-incineratable articles. Dumping of these products is also undesirable due to limited landfill space and increasing land cost. Consequently, there is a need for disposable products which may be quickly and conveniently disposed of by means other than dumping or incineration.
It has been proposed to dispose of these products in municipal and private sewage systems. Ideally, these products could be discarded by means of water and, for example, would be water weakenable and flushable in conventional sewage systems. Articles suited for disposal in sewage systems that can be flushed down conventional toilets are termed “flushable.” Disposal by flushing provides the additional benefit of providing a simple, convenient and sanitary means of disposal. However, all disposable products, and especially flushable products, must have sufficient strength to perform under the conditions in which they will be used. Thus, it is desirable for disposable products to withstand the elevated temperature and increased humidity conditions encountered during use, yet lose integrity upon contact with water such as, for example, in a toilet.
It is also desirable that these disposable products are breathable in order to increase the level of comfort of the consumers of these products. Many disposable articles are not designed for the comfort of the user. Many of these articles use thermoplastic polymers which do not have high water vapor transmission rates and therefore do not have good breathability. In the case of many disposable products, breathability is especially desirable in order to avoid the build-up of perspiration. By increasing the breathability of the films that comprise these products, the skin wellness of the user is also increased. It is desirable for the water vapor to pass through the film and move away from the skin rather than becoming trapped against the skin where it can cause possible rashes or other skin maladies. However, it would not be desirable for the film to disintegrate when exposed to the water vapor. Therefore, it is desirable for the article to be comprised of a breathable material which has mechanical integrity when it is dry, yet it is readily water weakenable upon immersion in water. Furthermore, it is highly desirable if the film demonstrates the stability and strength to withstand the environmental conditions of elevated temperature and increased humidity that are often experienced in many end-use situations, such as, for instance, in the use of personal care products.
Polyethylene oxide (PEO) is a commercially available thermoplastic water-soluble resin that is desirable for disposable applications. It is also desirable as a component material for flushable applications, due to its unique interaction with water and body fluids. PEO, which is represented by the following formula:
—(CH
2
CH
2
O)
n
—
can be produced from the ring opening polymerization of the ethylene oxide,
Because of its water-responsive properties, PEO is desirable for flushable applications. However, commercially available PEO resins are very sensitive to high humidity and elevated temperature environments which limits its use in many disposable products.
Because of today's global market, it is necessary to manufacture, ship and store product components, and end-use products all over the world, encompassing a multitude of climatic conditions. PEO films dramatically lose strength and rigidity when the humidity is above about 65% Relative Humidity (RH) and at temperatures of between about 35-55° C. because of the resulting increased moisture absorption. As a result, PEO films experience more failure and tear more easily during manufacturing and storage under these conditions of increased humidity and elevated temperatures. Especially noticeable are stress induced environmentally accelerated cracking and tearing which increases as the material ages.
These environmentally induced failures significantly limit the flexibility needed to manufacture, distribute, and sell disposable, flushable products. The film used for flushable products is usually folded, rolled or bent and then stored in warehouses until the end-use product is scheduled to be manufactured. The most cost effective storage space is generally not environmentally controlled and is subject to elevated temperatures and increased humidity. Such an environment accelerates the cracking and tearing of PEO films which often makes the films unsuitable for manufacture.
Shipping and storage of finished products can also cause environmentally induced tearing and cracking when the end use products are exposed to increased humidity and elevated temperature during shipment throughout the world and storage in distribution warehouses in various climates. Controlling the shipping and storage environment would significantly increase the cost of distribution.
Products that were subjected to increased humidity and elevated temperatures may also experience a higher incidence of failure during use causing consumer dissatisfaction. Furthermore, these problems all increase with aging of the product, limiting the length of time products could be stored before sale. These environmentally induced failures significantly limit the application of PEO, especially as a component of flushable products, because elevated temperature and increased humidity are often experienced during the manufacture, distribution and use of such products and result in performance failure.
Many have attempted to overcome these difficulties. The current state of the art includes disposable articles consisting of a liquid impermeable, vapor permeable film consisting of a crystallizable, stretched polyolefin-based film and a rattle-reducing additive which is poly(ethylene oxide). However, these liquid impermeable, vapor permeable films require at least one nucleating agent which is described as talc or calcium carbonate. Further, stretching is required to generate porosity and hence breathability and subsequent leaching of the rattle-reducing agent is desired. These are also coated, transparent plastic articles that may consist of poly(ethylene oxide). An inorganic, protective coating is applied as a separate layer over the transparent plastic article to improve surface hardness, increase stretch resistance, and facilitate non-fogging. The inorganic, protective coating can comprise various metal oxides. However, the coating forms a separate, discrete, glass-like layer from the transparent plastic article and the resulting coating and articles are not breathable or flushable.
Multilayered or coated recording sheets are available for electrostatic printing processes. The recording sheets consist of a base sheet with an anti-static layer, which can be made from poly(ethylene oxide). The recording sheets consis
Balogh Bridget A.
Topolkaraev Vasily A.
Kilpatrick & Stockton LLP
Kimberly--Clark Worldwide, Inc.
Nutter Nathan M.
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