Polyolefin Nanocomposite Materials
Publication Date: 2004-Nov-17
The IP.com Prior Art Database
A polymer composition including at least one polymer and at least one unmodified clay exfoliated in the polymer. A method of making a polymer composition with an unmodified, exfoliated clay therein.
POLYOLEFIN NANOCOMPOSITE MATERIALS
FIELD OF THE INVENTION
This invention relates to polyolefin nanocomposite materials and methods for making polyolefin nanocomposite materials.
BACKGROUND OF THE INVENTION
Polymer nanocomposites are a class of plastics that have nanometer-sized clay particles dispersed in the polymer matrix. One commonly used clay is montmorillonite, a layered alumino-silicate whose individual layers measure on the order of one nanometer (10-9 meter) thick and over a micron in width and length. Thus, the montmorillonite particles have a very high aspect ratio. In addition, the individual layers of the clay particles are separated by counter ions. The electrostatic interaction of the counter ions and the net negative charges within the clay platelets act to hold together the individual layers of the clay particles. Thus, the electrostatic interaction between the individual platelets and the counter ions results in stacks of platelets, or the layered structures, that are held tightly together.
One effect of the electrostatic interaction is that clays are naturally hydrophilic and are expected to be poorly suited for mixing and interacting with most polymer matrices. Past attempts to improve the miscibility of clays with polymer matrices have sought to modify the clay structure to make it more compatible with the polymer matrix. One such method is modification by the ion exchange of the sodium cations with another cation such as quaternary ammonium ions with long alkyl chains. Another approach is to use ion-dipole interaction to assist in compatibilization of the clay with the polymer matrix. Also, surface modification can be used to decrease the interlayer attraction of the clay platelets, allowing easier intercalation or exfoliation of the platelets in the polymer.
But processes that purify or modify the clay complicate the manufacturing process and add to the cost of the clay and the cost of polymer-clay composite materials. It would be beneficial if clays could be used in polymer composite materials without resorting to surface modification.
SUMMARY OF THE INVENTION
To meet at least one of the needs described above, a polymer composition including at least one polymer and at least one unmodified clay wherein the clay is exfoliated in the polymer is provided. In some embodiments, the polymer is an alpha-olefin polymer, such as a polyethylene homopolymer or interpolymer, a polypropylene homopolymer or interpolymer, or a polystyrene polymer. In some embodiments, the polyethylene is a linear low density polyethylene. In other embodiments, the polymer is a substantially linear alpha-olefin polymer.
 Suitable unmodified clays include, but are not limited to, biophilite, kaolinite, dickalite, talc clays, smectite clays, vermiculite clays, micas, and, brittle micas. Some useful smectite clays include montmorillonite, sodium montmorillonite, bidelite, saponite, hectorite, and fluorom...