Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2001-04-23
2004-01-06
Wilson, D. R. (Department: 1713)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S374000, C442S201000, C525S064000, C525S187000, C525S194000
Reexamination Certificate
active
06673446
ABSTRACT:
TECHNICAL FIELD
This invention relates to flushable fiber compositions. In a more specific aspect, this invention relates to flushable fiber compositions comprising modified polypropylene and modified poly(ethylene oxide). This invention also relates to a process for making such fiber compositions.
BACKGROUND OF THE INVENTION
Personal care products (such as diapers, sanitary napkins and adult incontinence garments) 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 film 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 personal care product. Commonly used film materials include plastic materials such as polyethylene films and the like.
Although such personal care products are relatively inexpensive, sanitary and easy to use, the proper disposal of a soiled product is not without 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 water disposal technologies while still delivering the performance which consumers have come to expect and demand. 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 film material (which normally does not disintegrate in water) tends to plug toilets and sewer pipes. Therefore, although undesirable, a person must separate the barrier film material from the absorbent article prior to flushing.
In addition to the disposable article, the packaging in which the article is distributed is often 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 article contained in the packaging. Although this packaging may be safely stored with other refuse for commercial disposal, the packaging is preferably disposed of together within the toilet with the discarded disposable article. However, where such packaging is composed of a water resistant material, plugging of the drains to the toilet may result.
In an effort to overcome these deficiencies, two methods have been utilized in the industry. The first method is for hydrophilic materials to be treated with a hydrophobic material to impart the desired water resistant properties to the hydrophilic materials.
The second method has been to modify a water resistant polymer. One of the more useful ways of modifying polymers involves blending 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, a greater number of blends are phase separated and generally exhibit poor mechanical compatibility. Phase separated blends can exhibit physical and mechanical compatibility where the polymer compositions are similar (for example, polyolefins 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.
Due to its unique interaction with water and body fluids, poly(ethylene oxide) is being considered as a component material for flushable products and fibers. Poly(ethylene oxide) is a commercially available water-soluble polymer that can be produced from the ring opening polymerization of ethylene oxide. Because of its water-soluble properties, poly(ethylene oxide) is desirable for flushable applications. However, there is a dilemma in utilizing poly(ethylene oxide) in flushable applications. Poly(ethylene oxide) resins of low molecular weights, (for example, 200,000 g/mol.) have desirable melt viscosity and melt pressure properties for extrusion processing but cannot be melt processed into fibers due to their low melt elasticities and low melt strengths. Poly(ethylene oxide) melt extruded from the spinning plates on fiber spinning lines resists drawing and is easily broken. Poly(ethylene oxide) resins of higher molecular weights, (for example, greater than 1,000,000 g/mol) have melt viscosities that are too high for melt processes for fiber-spinning. These factors make conventional poly(ethylene oxide) not processable for fiber making by conventional melt extrusion processes.
Poly(ethylene oxide) resins do not form fibers using conventional melt fiber-making processes. For purposes of this application, the term “fiber” refers to filaments or threads or filament-like or thread-like structures with diameters of about 100 microns or less. Conventional poly(ethylene oxide) resins can only be melt processed into strands with diameters in the range of several millimeters. Therefore, poly(ethylene oxide) compositions with appropriate melt elasticities and melt strengths are desired.
In the personal care product industry, flushable meltspun fibers are desired for commercial viability and ease of disposal. Poly(ethylene oxide) fibers have been produced by a solution casting process. However, the prior art has failed to melt process poly(ethylene oxide) fibers using conventional fiber making techniques such as melt spinning. Melt processing techniques are more desirable than solution casting because melt processing techniques are more efficient and economical. Melt processing of fibers is needed for commercial viability. Prior art poly(ethylene oxide) compositions cannot be extruded into the melt with adequate melt strength and elasticity to allow attenuation of fibers. Presently, fibers cannot be produced from conventional poly(ethylene oxide) compositions by melt spinning. Currently available poly(ethylene oxide) resins are not practical for melt extrusion into fibers and for incorporation into personal care products.
There is a need for water-responsive and flushable fibers for use in flushable personal care products, such as flushable diapers, feminine pads, pantiliners, child training pants and adult incontinence pads and briefs.
There is also a need to have flushable fibers comprising a polyolefin and a water-soluble polymer, especially poly(ethylene oxide). In addition to reducing material costs, the presence of a polyolefin in the flushable fiber composition improves melt processability. Many polyolefins can be melt spun into fibers in the prior art. However, no compositions comprising a blend of a polyolefin and poly(ethylene oxide) can be melt spun into fibers by the prior art because of poor melt spinning processability, especially poor melt strength, and poor melt extensibility.
In fiber extrusion processes, such as spunbond and meltblown processes, the presence of poly(ethylene oxide) in the flushable fiber composition contributes to the water-sensitivity and flushability of the composition.
This invention provides new and useful polymer blend compositions comprising a polyolefin and poly(ethylene oxide) and a process for making water-responsive fiber for use in flushable personal care products.
SUMMARY OF THE INVENTION
Briefly described, the present invention provides fiber compositions which can be used in flushable personal care products. More specifically, this invention provides such compositions which are comprised of modified polypropylene and modified poly(ethylene oxide). These fibers have good ductility with a tensile strain-at-break value which is higher than such value for the polypropylene used in these compositions and substantially higher than the poly(ethylene oxide) used in the fiber compositions of this invention.
The present invention also provides a reactive blending process for the manufacture of such fiber compositions in which polypropylene and poly(ethylene oxide) are modified with a pol
Schertz David M.
Wang James H.
Kimberly--Clark Worldwide, Inc.
Wilson D. R.
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