Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2000-08-01
2002-03-12
Hampton-Hightower, P. (Department: 1711)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S357000, C428S364000, C428S401000, C428S411100, C264S176100, C264S185000, C264S211210, C264S211220, C264S211230, C525S056000, C525S057000, C525S059000, C525S064000
Reexamination Certificate
active
06355347
ABSTRACT:
FIELD OF THE INVENTION
This invention relates, in general, to methods of making blend compositions of an unmodified polyvinyl alcohol and a metallocene polyolefin or grafted metallocene polyolefin and thermoplastic film and fiber structures comprising these blend compositions. More specifically, this invention relates to methods of making substantially water-free films and fibers comprising unmodified polyvinyl alcohol and a metallocene polyolefin or grafted metallocene polyolefin.
BACKGROUND OF THE INVENTION
Personal care articles are widely used in today's society. Many of these articles use films and fibers that are thermoplastic. Additionally, these articles use films and fibers that have different properties, depending on their location in the product. For example, some films and fibers are elastomeric. Others are breathable while still others act as liquid barriers. Finally, some of the films and fibers, especially those in contact with the wearer of the product, are designed to be softer to the touch. These different films typically comprise polymers or polymer blends that, when processed, form a film or fiber having the desired characteristic or characteristics.
Additionally, in an attempt to deal with decreasing land-fill and solid waste disposal many of these films and fibers are designed to be water-dispersible such that the product will partially or completely disperse in water, thereby allowing the product to be disposed of without dumping or incineration. These products may be placed in sewage systems or may be flushed down a conventional toilet. To produce these water-dispersible products, the films and fibers used in the products will typically use blend compositions that include a water-dispersible polymer such as polyethylene oxide or polyvinyl alcohol.
Polyvinyl alcohol (PVOH) is a commodity polymer that is used in a wide variety of different applications. Many of these applications are thermoplastic. However, PVOH is generally regarded as a non-thermoplastic polymer. PVOH has a high melting point of about 200° C. depending on the degree of hydrolysis. Accordingly, as PVOH is heated near its melting point, yellowing and discoloration occur. Therefore, when using PVOH as a base material for thermoplastic applications, the PVOH must usually be modified.
Modified PVOH is used in many different water-dispersible thermoformable articles, such as fibers, films and fabrics which maintain their integrity and strength when in use, but dissolve and disperse when placed in contact with water. Unmodified PVOH is used in industry for many different solution-based applications and is not generally considered to be thermoformable or melt-processable. Some such applications for unmodified PVOH include warp sizing in textiles, fabric finishing, adhesives, paper processing additives, and emulsifiers/dispersants.
The prior art has demonstrated some success in modifying PVOH for use in thermoplastic applications. By “modified” PVOH, it is meant PVOH resin which has been chemically modified, including PVOH having another compound grafted thereto, or PVOH resin that has been mixed with one or more plasticizers. In each instance, these “modifications” have been needed to permit PVOH to be used in thermoformable articles.
To overcome the thermoplastic processing problems, chemically modified PVOH has been used. Some prior art teachings have used ethers of PVOH, ethoxylated PVOH or lacton-modified PVOH to produce thermoformable articles.
The prior art has also used PVOH that has not been modified structurally by adding a plasticizing agent to the PVOH which permits the PVOH to be extruded into films and fibers. Examples of plasticizers include water, ethylene glycol, glycerin and ethanolamine.
However, there are problems associated with the addition of plasticizers to PVOH. One of the most pronounced problems during processing is the fogging of the volatile plasticizer during the melt extrusion and condensing of vapor and effects of the vapor to the operating environment. In addition, the extruded articles such as films or fibers lose the plasticizers since the plasticizer molecules diffuse out of the film or fibers. This causes the films or fibers to become brittle over time and often causes the article to fail.
Additionally, films and fibers including modified PVOH or PVOH and a plasticizer may be limited in their utility. These films and fibers may be too stiff to be used for certain applications. Additionally, the texture of the films may not be soft enough for comfortable contact with the skin of an individual.
Accordingly, what is needed is an unmodified PVOH that may be used in blend compositions that are thermoplastically formed into films and fibers. These films and fibers may then be used in the production of water-dispersible, flushable articles without the use of plasticizing agents. These fibers, films and fabrics could be used in products such as personal care products, diapers, feminine napkins and pads, training pants, wipes, adult incontinence products, release liners, product packaging, etc., which contain the above-mentioned fibers, films and fabrics. Additionally, what is needed are methods of making thermoplastic films and fibers that have enhanced softness and ductility.
SUMMARY OF THE INVENTION
Accordingly, the present invention desires to produce films and fibers including blend compositions having unmodified PVOH and a metallocene polyolefin or grafted metallocene polyolefin.
Another desire of the present invention is to use unmodified PVOH and a metallocene polyolefin or grafted metallocene polyolefin to form films and fibers without the use of a plasticizing agent.
These and other desires are satisfied by the present invention. The present invention discloses the selection and use of commercially-available grades of PVOH for thermoplastic applications. “Thermoplastic” is defined, herein, as a resin which can be melted and easily extruded to form a desired article, i.e., the material is melt processable. These commercially-available grades of PVOH are combined with a metallocene polyolefin or grafted metallocene polyolefin to provide a blend composition useful in the production of films and fibers that have enhanced softness and ductility.
PVOH is a commodity polymer, commonly used in aqueous solution-based applications. Since it is a commodity polymer, thermoplastic articles made using unmodified PVOH are generally less expensive than articles made using modified PVOH due to the additional process steps required to modify the PVOH. Also, unmodified PVOH is, in general, less expensive than other water-soluble polymers.
In its unmodified form, PVOH has not been used for thermoplastic applications. Typically, some modification of the PVOH, such as chemical grafting or addition of plasticizer, is necessary to achieve melt processability for PVOH. In the present invention, a window of thermoplastic processability has been discovered and defined for unmodified, commercially-available PVOH, according to: 1) the composition or % hydrolysis of the PVOH, 2) the molecular weight of the PVOH, 3) the solution viscosity of the PVOH, or 4) the melt viscosity of the PVOH. The selected grades of PVOH have demonstrated thermoplasticity, allowing for continuous, melt extrusion or conversion into thin films in a continuous, extrusion process.
These grades of PVOH are also useful for melt spinning of fibers, injection molding or other thermoplastic applications. Extruded films of the unmodified PVOH/metallocene polyolefin or grafted metallocene polyolefin blends described herein have very high strength and modulus, excellent clarity, and fast crystallization and solidification rates. The advantages of melt processing a thermoplastic, unmodified PVOH into a useful, strong, clear, water-soluble article are evident. Melt processing is a desirable thermoforming process compared to solution processing. Melt processing eliminates the need to add steps such as chemical grafting, addition of a plasticizer, or other modification in order to achieve melt processability.
These grad
Pomplun William S.
Schertz David Michael
Wang James Hongxue
Wideman Gregory J.
Hampton-Hightower P.
Kilpatrick & Stockton LLP
Kimberly--Clark Worldwide, Inc.
LandOfFree
Methods of making blend compositions of an unmodified... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Methods of making blend compositions of an unmodified..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Methods of making blend compositions of an unmodified... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2848541