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
1999-06-07
2001-04-10
Seidleck, James J. (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...
C525S060000, C525S061000, C525S064000, C525S071000
Reexamination Certificate
active
06214933
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to compositions comprising a blend of polyolefin and poly(ethylene oxide) having inverse phase morphology and methods of making such inverse phase compositions.
BACKGROUND OF THE INVENTION
There are a wide variety of disposable plastic articles of manufacture in use today. Because of their low cost and convenience, they are very popular and have a high consumer demand. However, many of these articles are not degradable or easily disposed of. Consequently, they have caused and continue to cause a waste disposal problem.
Personal care products, such as diapers, sanitary napkins, adult incontinence garments, and the like are generally constructed from a number of different components and materials. Such articles typically have some portion, usually the backing layer, liner, or baffle that is composed of a film constructed from a liquid repellent material. This repellent material is appropriately constructed to minimize or prevent the exuding of the absorbed liquid from the article and to obtain greater utilization of the absorbent capacity of the product. The liquid repellent film commonly used includes plastic materials such as polyethylene films and the like.
Although such products are relatively inexpensive, sanitary and easy to use, disposal of a product once soiled is not without its problems. An ideal disposal method for such products would be to use municipal sewage treatment and private residential septic systems. Products suited for disposal in sewage systems can be flushed down a convenient toilet and are termed “flushable.” While flushing such articles would be convenient, the liquid repellent material which normally does not disintegrate in water tends to plug toilets and sewer pipes. It therefore becomes necessary, although undesirable, to separate the barrier film material from the absorbent article prior to flushing.
In an attempt to overcome the flushability problem of a water-resistant film the prior art has modified the water-resistant polymer. One of the more useful ways of modifying polymers involves blending them with other polymers of different structures and properties. In a few cases, polymer blend combinations are thermodynamically miscible and exhibit mechanical compatibility. However, by far a greater number of blends are phase separated and generally exhibit poor mechanical compatibility. Phase separated blends can in some cases exhibit mechanical compatibility where the polymer compositions are similar, for example, polyolefin blended with other similar polyolefins, or where interfacial agents are added to improve the compatibility at the interface between the constituents of the polymer blend.
Polymer blends of polyolefins and poly(ethylene oxide) are melt processible but exhibit very poor mechanical compatibility. This poor mechanical compatibility is particularly manifested in blends having greater than 50 weight percent of polyolefin. Generally the film is not affected by water since typically the majority phase, i.e. polyolefin, will surround and encapsulate the minority phase, i.e. the poly(ethylene oxide). The encapsulation of the poly(ethylene oxide) effectively prevents any degradability and/or flushability advantage that would be acquired by using poly(ethylene oxide).
In view of the problems of the prior art, it remains highly desirable to provide water-degradable compositions comprising poly(ethylene oxide) incorporating greater amounts of lower cost polyolefin(s) while maintaining or at least not significantly decreasing the water responsiveness of the composition. Advantageously, such compositions can be used to manufacture flushable films and flushable fibers at lower cost. These films and fibers can be used as components in personal care products that are designed to be flushed down conventional toilets. Additionally, the unique water related properties of the compositions described herein compositions make the compositions desirable for the manufacture of filter membranes.
SUMMARY OF THE INVENTION
Briefly, the present invention provides for compositions comprising a volume of poly(ethylene oxide) and a greater volume of polyolefin relative to the volume of poly(ethylene oxide) wherein the compositions exhibit an inverse phase morphology. As used herein “inverse phase morphology” means that the volumetric majority constituent, which normally would be expected to form the continuous phase in the composition, is the dispersed phase and the volumetric minority constituent forms the continuous phase in which the volumetric majority constituent is dispersed. Inverse phase polyolefin and poly(ethylene oxide) compositions are desirable because they have improved water responsiveness and water dispersibility compared to compositions comprising the same relative amounts of the aforementioned polymers that do not have inverse phase morphology described above.
The compositions of the present invention lose a substantial amount of mass when exposed to water. Consequently, films, fibers and articles manufactured from the compositions of the present invention exhibit a significant decrease in the their mechanical properties when exposed to water compared to the dry mechanical properties prior to exposure to water. The compositions of the present invention are substantially water degradable and may be used to produce flushable films, fibers and articles. Significantly, films, fibers and articles can be produced which incorporate greater amounts of essentially water-insoluble polyolefins relative to amount of water-soluble poly(ethylene oxide) while remaining water-degradable and flushable. Thus, flushable articles such as diapers and feminine pads can be manufactured with smaller amounts water-soluble and water-responsive resins, at lower cost.
REFERENCES:
patent: 5912076 (1999-06-01), Wang et al.
Schertz David M.
Wang James H.
Asinovsky Olga
Kilpatrick & Stockton LLP
Kimberly--Clark Worldwide, Inc.
Seidleck James J.
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