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
1999-12-01
2002-07-09
Cain, Edward J. (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...
C524S447000, C501S148000
Reexamination Certificate
active
06417262
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to a nanocomposite comprising at least one high barrier amorphous matrix polymer resin, preferably amorphous polyamide, and a clay material uniformly dispersed therein. This invention also relates to articles produced from the nanocomposite and a process for producing the nanocomposite.
BACKGROUND OF THE INVENTION
Thermoplastic materials are being increasingly used in the packaging of beverages and perishable foods. Plastics are often the material of choice for food and beverage packaging because of their clarity, flexibility, toughness, high gas barrier, light weight, processability and high gloss.
Many high barrier semi-crystalline polyamides exist and one, the polyamide based on m-xylylenediamine and adipic acid, is commercially available from Mitsubishi Gas and Chemical Company under the name MXD6. These crystalline polymers have been found to possess high barrier to oxygen and carbon dioxide. Polyamides such as the one based on m-xylylenediamine and adipic acid have found utility in packaging oxygen sensitive foodstuffs, especially as the center layer in a tri-layer stretch blow molded container or a tri-layer extruded film.
Amorphous polyamides have been prepared and proposed as polymers for food packaging, offering improved resistance to whitening or hazing upon exposure to moisture, as described in U.S. Pat. Nos. 5,028,462 and 4,983,719, and offering improved physical properties, as described in U.S. Patent 4,018,746. However, these patents do not disclose or suggest incorporating a clay material into such amorphous polyamide to improve the barrier of the polyamide or an article made therefrom. Further, these patents do not disclose or suggest that haze would be reduced in a composite comprising a clay material and an amorphous polyamide.
The principle of utilizing a layered clay to enhance or improve the properties of a polymer matrix in which the clay has been dispersed is well established. U.S. Pat. No. 4,739,007 describes the use of a composite material comprising a polyamide matrix and well-dispersed silicate layers exhibiting high mechanical strength and excellent high temperature properties. Additional publications describing polymer nanocomposites comprising a polyamide matrix and dispersed layers of silicate include U.S. Pat. No. 4,810,734; German Patent 3808623;
J. Inclusion Phenomena
5, (1987), 473-485;
Clay Minerals,
23, (1988) 27;
Polymer Preprints,
32, (April 1991), 65-66; and
Polymer Preprints,
28, (August 1987), 447-448.
Multilayer materials for packaging are known for film, bottles, and other containers. Multilayer injection molded preforms described, for example, in European Patent Application 0 278 403 A2 and U.S. Pat. No. 4,398,642, contain an outer thermoplastic layer to impart excellent overall properties to the material and an inner layer of thermoplastic resin possessing excellent gas-barrier properties. Molded containers produced from these multilayer preforms have potential advantages in regards to handling, safety, and the cost of production. However, processing multilayer containers usually involves additional and time-consuming steps.
It is often desirable to include a dispersed clay in an inner or center layer of a multilayer article comprising a high barrier polyamide such as the one based on m-xylylenediamine and adipic acid. The use of these clays in matrix polymers of the inner layer a multilayer container may reduce the haze of multilayer structures and improve the appearance of oriented films and molded articles, including bottles.
However, clay particles in a nylon-6 nanocomposite, for example, induce crystallization, as described in U.S. Pat. No. 5,385,776. Without being bound by any particular theory, it is believed that the polymer/clay nanocomposite on processing, such as stretching or orientation of the films, leads to very high levels of haze from crystallization of the matrix polymer around the dispersed particles which renders the polymer nanocomposites undesirable for food packaging application. This crystallization phenomena can even lead to void and hole formation in the polymer films, which destroys the usefulness of these compositions in barrier applications.
Thus, there remains a need in the art for an amorphous polyamide nanocomposite having reduced haze. There is also a need for oriented monolayer and/or multilayer structures comprising this amorphous polyamide nanocomposite. Moreover, there is a need for a process capable of introducing clay material having substantially separated platelet particles to an amorphous polyamide to produce a nanocomposite having improved barrier properties and good clarity.
SUMMARY OF THE INVENTION
The invention relates generally to amorphous high barrier polyamides, and more particularly to polyamide nanocomposites comprising a high barrier amorphous polyamide and a clay material. These amorphous polyamides show unexpected resistance to haze formation, crystallization, and other defect formation in the presence of dispersed, treated or organically modified clays when undergoing orientation and other film processing steps.
As embodied and broadly described herein, this invention, in one embodiment, relates to a polyamide-clay nanocomposite comprising (a) an amorphous matrix polyamide comprising (i) a residue of a dicarboxylic acid component comprising at least two diacids and (ii) a residue of a diamine component, and (b) a layered clay material, wherein the layered clay material is dispersed in the matrix polyamide.
In another embodiment, this invention relates to a polyamide-clay nanocomposite comprising (a) an amorphous matrix polyamide comprising (i) a residue of a dicarboxylic acid component comprising at least two diacids and (ii) a residue of a diamine component, and (b) a layered clay material, wherein the layered clay material is dispersed in an amorphous matrix polyamide-compatible oligomeric resin and wherein the clay-oligomer resin dispersion is incorporated into the matrix polyamide.
In yet another embodiment, this invention relates to a process for preparing an amorphous polyamide-clay nanocomposite comprising the steps of: (i) melt mixing a clay material with a matrix polymer-compatible oligomeric resin to form an oligomeric resin-clay composite, and (ii) mixing the oligomeric resin-clay composite with a high molecular weight amorphous matrix polyamide comprising (i) a residue of a dicarboxylic acid component comprising at least two diacids and (ii) a residue of a diamine component, thereby increasing the molecular weight of the oligomeric resin-clay composite and producing a nanocomposite material.
In yet another embodiment, this invention relates to a process for preparing an amorphous polyamide-clay nanocomposite comprising the steps of: (a) adding a clay material to a mixture of (i) a dicarboxylic acid component comprising at least two diacids and (ii) a diamine component of an amorphous polyamide, and (b) conducting the polycondensation polymerization of components (i) and (ii) in the presence of the clay material.
Additional advantages of the invention will be set forth in part in the detailed description, including the figures, which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory of preferred embodiments of the invention, and are not restrictive of the invention, as claimed.
DETAILED DESCRIPTION OF THE INVENTION
The present invention may be understood more readily by reference to the following detailed description of the invention and the examples provided therein. It is to be understood that this invention is not limited to the specific components, articles, processes and/or conditions described, as these may, of course, vary. It is also to be understood tha
Bagrodia Shriram
Connell Gary Wayne
Gilmer John Walker
Lan Tie
Matayabas, Jr. James Christopher
Cain Edward J.
Eastman Chemical Company
Graves, Jr. Bernard J.
Lee Katarzyna W.
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