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
2000-04-19
2001-07-03
Woodward, Ana (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...
C525S187000
Reexamination Certificate
active
06255386
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to blends comprising a polyolefin and poly(ethylene oxide) and a method of making blends. In one embodiment, the invention relates to blends having up to about 85 weight percent of a modified polyethylene or a modified polypropylene and a modified poly(ethylene oxide) and a method of making the modified polyolefin and modified poly(ethylene oxide) blend using a single step, reactive extrusion process.
BACKGROUND OF THE INVENTION
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 a portion, usually the backing layer, liner, or baffle constructed of a liquid repellent film material. This repellent material is appropriately constructed to minimize or prevent the exudation 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 such a product once soiled is not without its problems. With greater interest being placed in protecting the environment today, there is a need to develop materials that are more compatible with the existing and developing waste disposal technologies while still delivering performance consumers have come to expect. An ideal disposal alternative 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 that 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 addition to the article itself, typically the packaging in which the disposable article is distributed is also made from a water-resistant material. Water resistivity is necessary to prevent the degradation of the packaging from environmental conditions and to protect the disposable articles therein. Although this packaging may be safely stored with other refuse for commercial disposal, and especially in the case of individual packaging of the products, it is often more convenient to dispose of the packaging in the toilet with the discarded disposable article. However, in the cases where such packaging is composed of a water-resistant material, plugging of the drains to the toilet typically results.
In an effort to overcome these deficiencies, two methodologies have been utilized. The first is for hydrophilic materials to be treated with a hydrophobic material to impart the desired water-resistant properties to the material.
The second method has been to modify a 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 physical and 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 physical and 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 manifested in the mechanical property profile of the blends relative to the properties of the unblended constituents.
In view of the problems of the prior art, it remains highly desirable to provide a water responsive material. Such blends could be used for making flushable barrier films, extrusion applications and injected molded articles.
SUMMARY OF THE INVENTION
Briefly, one aspect of the present invention provides for a modified polyolefin and modified poly(ethylene oxide) blend composition. The blend composition is composed of from about 1 weight percent to about 85 weight percent of a modified polyolefin and from about 99 weight percent to about 15 weight percent of a modified poly(ethylene oxide). The modified polyolefin and modified poly(ethylene oxide) have grafted thereto from about 1 weight percent to about 30 weight percent, based on the weight of the polyolefin and poly(ethylene oxide), of a monomer.
Another aspect of the invention provides for a method of making the modified polyolefin and modified poly(ethylene oxide) blend composition. The method provides a single pass, melt reactive extrusion modification of the polyolefin and poly(ethylene oxide). This single step process affords significant advantages over a two step process where the polyolefin is first modified by grafting a monomer onto the polyolefin backbone which is then re-extruded with the poly(ethylene oxide). A few of the advantages include cost savings, reduced polymer degradation and greater uniformity in the final product. Specifically, the method of preparing the blend of modified polyolefin and modified poly(ethylene oxide) using a single pass, melt reactive extruder comprises melting the polyolefin and poly(ethylene oxide) in the extruder and adding to the polyolefin and poly(ethylene oxide) blend a monomer and a sufficient amount of a free radical initiator to graft from about 1 weight percent to about 100 weight percent of the monomer onto the polyolefin and poly(ethylene oxide).
It is an object of the invention to provide a blend composition comprising a modified polyolefin and modified poly(ethylene oxide). More specifically, it is an object of the invention to provide a blend composition comprising a modified polyethylene or modified polypropylene and modified poly(ethylene oxide).
Another object of the invention is to provide a method of making a modified polyolefin and modified poly(ethylene oxide) blend composition using a single pass reactive extruder.
As used herein “reactive extrusion” is the use of chemical reactions during polymer extrusion to form desired products. Free radical initiator, crosslinking agents, and other reactive additives can be injected into the extruder to cause such reactions.
DETAILED DESCRIPTION OF THE INVENTION
The mechanical and visual compatibility of blends of polyolefins and poly(ethylene oxide) is very poor. However, it has unexpectedly been found that polyolefins and poly(ethylene oxide) can be modified with one or more monomers, such that materials made from blends having upwards of about 85 weight percent of a modified polyolefin and as little as 15 weight percent of a modified poly(ethylene oxide) are water responsive. More specifically, it has been found that blends of polyolefins and poly(ethylene oxide), when grafted with a polar, vinyl monomer during reactive extrusion imparts water responsiveness to films and thermoplastic articles made therefrom. Accordingly, one aspect of the invention is for a composition of matter comprising a polymer blend having from about 1 weight percent to about 85 weight percent of a modified polyolefin and from about 99 weight percent to about 15 weight percent of a modified poly(ethylene oxide). Preferably, the blend comprises from about 30 weight percent to about 85 weight percent of a modified polyolefin and from about 70 weight percent to about 15 weight percent of modified poly(ethylene oxide). More preferably, the blend comprises from about 55 weight percent to about 85 weight percent of a modified polyolefin and from about 45 weight percent to about 15 weight percent of modified poly(ethylene oxide).
The amount of monomer added to the blend of polyolefin and poly(eth
Schertz David Michael
Wang James Hongxue
Kilpatrick & Stockton LLP
Kimberly--Clark Worldwide, Inc.
Woodward Ana
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