Reduced crystallinity polyethylene oxide with intercalated clay

Details Reduced crystallinity polyethylene oxide with intercalated clay Reduced crystallinity polyethylene oxide with intercalated clay

2000-07-17

2003-04-29

Toomer, Cephia D. (Department: 1714)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

At least one aryl ring which is part of a fused or bridged...

Reexamination Certificate

active

06555610

ABSTRACT:

FIELD OF THE INVENTION
This invention relates in general to a method for rendering polyethylene oxide to a material of reduced crystallinity. More specifically, this invention relates to a method of forming a polymer composite comprising mixing smectite clay and polyvinyl pyrrolidone to form a first dispersion of intercalated clay, mixing said dispersion with polyethylene oxide to form a second dispersion, flowing said second dispersion into ketone so as to flocculate a polymer composite, and recovering said flocculate.
BACKGROUND OF THE INVENTION
Polymers find a wide range of applications for use as films and coatings. In many instances, these films or coatings must be transparent. In addition to the transparency issue, these films or coatings should be able to be manufactured at a low cost and with as simple procedure as possible. For many polymers, transparent coatings or films can be generated but require melt extrusion or expensive organic solvents. It is preferable to be able to generate materials, which can be formulated using aqueous based systems. However, at high polymer concentration (greater than or equal to 50 weight %), many of these aqueous soluble/dispersible polymers will show significant crystallization upon drying, rendering the resultant films or coatings hazy due to light scattering from the crystallites in the polymeric film.
Polyethylene oxide polymers are high molecular weight water-soluble polymers with a wide variety of applications. Some of these applications are detailed in product brochures of Union Carbide for their Polyox water-soluble resins. According to such product literature, polyethylene oxide can be used as binders for pigments, fillers, metal powders, and ceramics with application in battery electrodes, cathode ray tubes, and fluorescent lamps. The strong hydrogen bonding affinity of polyethylene oxide accounts for its association with various polar compounds, such as phenolic resins, mineral acids, halogens, ureas, lignin sulfonic acids, and poly carboxylic acids. These novel complexes can be discrete chemical entities with unique properties with application in batteries, microencapsulated inks, slow release bacteriostats, water soluble adhesives, etc. Polyethylene oxide can form water-retentive gels with application as absorbent pads and diapers. Polyethylene oxide can be used as emollient in cosmetic and hair products. Most importantly, polyethylene oxide can be formed into flexible films both by thermoplastic processing and casting techniques, providing wide latitude of applications. As thermoplastics, these films are readily calendered, extruded, molded, or cast. Sheets and films of polyethylene oxide can be oriented to develop high strength. Polyethylene oxide films are inherently flexible and tough, and resistant to most oils and greases. Polyethylene oxide can be used alone or blended with a wide variety of other polymers such as polyethylene, polystyrene, polycaprolactone, ethylene vinyl acetate, nylon, etc. In packaging, polyethylene oxide can be used to provide heat-sealability, hot melt adhesion, improved resistance to humidity, lubricity, controlled release, bio-degradability, and non-toxicity. However, as noted in the product literature, polyethylene oxide, particularly the higher molecular weight grades, retains a very high degree of crystalline character at temperatures far above the melting point. This retained crystallinity renders these materials unsuitable in applications requiring transparency for aesthetic or optical reasons.
Additional applications of polyethylene oxide include U.S. Pat. No. 5,143,071 which describes the formation of non-stringy adhesive hydrophilic gels using polyethylene oxide and water or polyvinyl pyrrolidone, and may have a water-soluble electrolyte added to provide conductive non-stringy adhesive materials for medical electrodes. To make effective, these polymeric mixtures must be cross-linked using exposure to radiant energy, then remain tacky such that the adhesive can adhere to a subject's skin without discomfort.
U.S. Pat. No. 5,866,292 describes a liquid developer composition with a copolymer, where a charged liquid developer is comprised of a nonpolar liquid, thermoplastic resin particles, pigment, a charge director, and a charge control agent comprised of a polyethylene oxide:polypropylene oxide blend in a solid form.
A resin for paper making is described in U.S. Pat. No. 5,866,669. Sulfonated phenol-formaldehyde is combined with polyethylene oxide to yield a paper, which has long life and improves the yield of fine fiber and filler reducing the water treatment waste load. Another polyethylene oxide application for paper manufacture is described in U.S. Pat. No. 5,578,168 where polyethylene oxide is dispersed with a salt to form a suspension with at least 15% polyethylene oxide by weight. The said suspension prevents the loss of fiber fines during paper manufacture and resists viscosity loss.
A thermoplastic composition is described in U.S. Pat. No. 6,010,971 where polyethylene oxide is mixed with a multicarboxylic acid (ex: adipic acid). Such a material can be extruded into fibers and formed into a nonwoven structure and may be used for disposable absorbent products intended for the absorption of fluids such as body fluids. A similar application can be found in U.S. Pat. No. 5,916,969 where polyethylene oxide is blended with polyolefins for disposable absorbent articles such as a diaper or feminine pad. Such a material can be produced only under melt conditions.
U.S. Pat. No. 5,618,316 describes an invention to provide an intraocular lens having improved biocompatibility achieved by applying a polyethylene oxide coating to the lens surface through covalent bonding.
U.S. Pat. No. 5,589,545 describes molded polymer blends which become lubricious when exposed to water with end uses in personal care articles, e.g., lubricious strips for razors, and in medical articles, e.g., catheters.
U.S. Pat. No. 5,011,814 describes a dye-receiving element for thermal dye transfer including a support having on one side thereof a polymeric dye image-receiving layer and on the other side thereof a backing layer made from a mixture of PEO and submicrometer colloidal inorganic particles.
U.S. Pat. No. 5,674,578 describes water soluble/dispersible multilayered film of high interlayer adhesive strength and collection pouches formed therefrom, with high load bearing capacity but easily disposable.
In the literature, examples are provided where PEO is blended with clay materials for the purpose of obtaining enhanced properties such as modulus. Lerner and coworkers (Chem. Mater., (1993), 5, p. 835; Elect. Acta, (1995), 40, p. 2245) described the generation of polyethylene oxide and Na-montmorillonite clay nanocomposites where the polyethylene oxide and clay were added to water. After 24 hours of stirring, followed by vacuum drying, they were able to successfully intercalate PEO into the clay lattice up to 30 wt. % polyethylene oxide. However, at polyethylene oxide levels greater than 30 wt. %, crystalline polyethylene oxide was observed. Giannelis and coworkers (Adv. Mater., (1995), 7, p. 154), working on polymer electrolyte nanocomposites, observed similar intercalation effects when they worked with polyethylene oxide and Na or Li exchanged silicate clays. In their materials preparation, montmorillonite clay (28 wt. %) was mixed with PEO and annealed for 6 hours at 80° C. Before annealing, crystalline polyethylene oxide was observed to be present in the sample. After the long annealing time, the crystalline PEO was not observed indicating that it had intercalated inside the clay. Like Lerner, Giannelis found that at a higher clay level, 40 wt. %, crystalline polyethylene oxide was present that did not intercalate the clay. A method of making clay-polyethylene oxide nanocomposites using acetonitrile as the solvent is described by Schmidt-Rohr and coworkers (Macromol., (1999), 32, P. 6718). They, like Giannelis, also found that when polyethylene oxide is at a 40 wt.% level in the nanocomposite, excess cryst

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