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
2002-05-14
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...
C524S446000, C524S447000, C501S148000
Reexamination Certificate
active
06387996
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to polymer-clay nanocomposites having improved gas permeability comprising a clay material intercalated with a mixture of organic cations and a polymer. This invention further relates to intercalates, exfoliates, nanocomposites, and articles produced from the intercalates, exfoliates, and nanocomposites; and processes for preparing the intercalates, exfoliates and nanocomposites, and articles.
BACKGROUND OF THE INVENTION
There is much interest in layered clay-based polymer nanocomposites because of the improved properties exhibited by the nanocomposites. It is desirable to maximize delamination of the layered clay material into individual platelet particles in order to maximize some property improvements, including barrier (gas permeability) improvements, and to minimize deleterious effects on some properties including elongation-at-break. Ideally, the clay material is exfoliated into platelet particles with a thickness of less than about 20 nm in order to achieve clarity that is comparable to the clay-free polymer. To date, the only polymer/clay nanocomposites that meet this expectation are prepared by incorporation of organically treated clays during synthesis of the polymer from monomer. It is widely known, however, that the amount of clay that can be admixed in a polymer and still exhibit exfoliation of the layered clay is limited and some mechanical properties, such as elongation-at-break, are often reduced considerably upon the addition of the clay.
Researchers recognized the value of inventing melt-compounding processes that provide exfoliated clay composites. Namely, melt-compounding processes provide more versatility of polymer choice and clay loading and the potential for cost savings. However, with many polymer/clay mixtures, the melt compounding processes explored to date do not provide sufficient exfoliation of the platelet particles.
Polyesters such as poly(ethylene terephthalate) (PET) are widely used in bottles and containers which are used for carbonated beverages, fruit juices, and certain foods. Useful polyesters have high inherent viscosity (I.V.), which allows polyesters to be formed into parisons and subsequently molded into containers. Because of the limited barrier properties to oxygen, carbon dioxide and the like, PET containers are not generally used for products requiring long shelf life. For example, oxygen transmission into PET bottles which contain beer, wine and certain food products causes these products to spoil. There have been attempts to improve the barrier properties of PET containers by the use of multilayer structures comprising one or more barrier layers and one or more structural layers of PET. However, multilayer structures have not found wide use and are not suitable for use as a container for beer due to the high cost, the large thickness of the barrier layer required, and poor adhesion of the barrier layer to the structural layer.
There are many examples in the patent literature of polymer/clay nanocomposites prepared from monomers and treated clays. For example, U.S. Pat. No. 4,739,007 discloses the preparation of Nylon-6/clay nanocomposites from caprolactam and alkyl ammonium-treated montmorillonite. U.S. Pat. No. 4,889,885 describes the polymerization of various vinyl monomers such as methyl methacrylate and isoprene in the presence of sodium montmorillonite.
Some patents describe the blending of up to 60 weight percent of intercalated clay materials with a wide range of polymers including polyamides, polyesters, polyurethanes, polycarbonates, polyolefins, vinyl polymers, thermosetting resins and the like. Such high loadings with modified clays are impractical and useless with most polymers because the melt viscosities of the blends increase so much that they cannot be molded.
WO 93/04117 discloses a wide range of polymers melt blended with up to 60 weight percent of dispersed platelet particles. WO 93/04118 discloses nanocomposite materials of a melt processable polymer and up to 60 weight percent of a clay that is intercalated with organic onium salts. The use of clays intercalated with a mixture of onium ions is not contemplated or disclosed.
U.S. Pat. No. 5,552,469 describes the preparation of intercalates derived from certain clays and water soluble polymers such as polyvinyl pyrrolidone, polyvinyl alcohol, and polyacrylic acid. The use of clays intercalated with organic cations is specifically excluded.
JP Kokai patent no. 9-176461 discloses polyester bottles wherein the polyester contains unmodified sodium montmorillonite. Incorporation of the clay into the polyester by melt compounding is disclosed; however, the use of clays intercalated with a mixture of organic cations is neither contemplated nor disclosed.
Clays intercalated with a mixture of organic cations, typically onium ions, are used as rheology modifiers for certain coating applications; however, their use in polymer/clay nanocomposites has been neither contemplated nor disclosed. The following references are of interest with regard to chemically modified organoclay (clay/organic cation intercalate) materials: U.S. Pat. Nos. 4,472,538; 4,546,126; 4,676,929; 4,739,007; 4,777,206; 4,810,734; 4,889,885; 4,894,411; 5,091,462; 5,102,948; 5,153,062; 5,164,440; 5,164,460; 5,248,720; 5,382,650; 5,385,776; 5,414,042; 5,552,469; WO Pat. Application Nos. 93/04117; 93/04118; 93/11190; 94/11430; 95/06090; 95/14733; D. J. Greenland, J. Colloid Sci. 18, 647 (1963); Y. Sugahara et al., J. Ceramic Society of Japan 100, 413 (1992); P. B. Messersmith et al., J. Polymer Sci.: Polymer Chem., 33, 1047 (1995); C. O. Oriakhi et al., J. Mater. Chem. 6, 103(1996).
Therefore, as shown above, a need still exists for a polymer nanocomposite comprising a clay material and articles produced therefrom that have improved barrier properties.
SUMMARY OF THE INVENTION
It has been found that clays intercalated with a mixture of organic cations, preferably onium ions, are useful for the preparation by a melt compounding process of a polymer/clay nanocomposite with sufficient exfoliation and molecular weight for improved properties and clarity for commercial applications, including film, bottles, and containers. The polymer nanocomposite of this invention is particularly useful for forming packages that have improved gas barrier properties. Containers made from these polymer composite materials are ideally suited for protecting consumable products, such as foodstuffs, soft drinks, and medicines.
This invention also seeks to provide a cost-effective method for producing barrier layers with sufficient oxygen barrier and clarity for wide spread applications as multilayer bottles and containers, including beer bottles.
In accordance with the purpose(s) of this invention, as embodied and broadly described herein, this invention, in one embodiment, relates to a polymer-clay nanocomposite having an improved gas permeability comprising (i) a melt-processible matrix polymer, and incorporated therein (ii) a layered clay material intercalated with a mixture of at least two organic cations.
In another embodiment, this invention relates to a process for preparing a polymer-clay nanocomposite comprising (i) preparing an intercalated layered clay material by reacting a swellable layered clay material with a mixture of at least two organic cations, and (ii) incorporating the intercalated clay material in a matrix polymer by melt processing the matrix polymer with the intercalated clay.
In yet another embodiment, this invention relates to a process for preparing a polymer-clay nanocomposite having an improved gas permeability comprising the steps of: (i) preparing an intercalated layered clay material by reacting a swellable layered clay material with a mixture of at least two organic cations, (ii) adding the clay material to components for forming a polymer, and (iii) conducting the polycondensation polymerization of the components in the presence of the clay material.
Additional advantages of the invention will be set forth in part in the detailed description
Barbee Robert Boyd
Gilmer John Walker
Lan Tie
Matayabas, Jr. James Christopher
AMCOL International Corporation
Cain Edward J.
Marshall Gerstein & Borun
W-Lee Katarzyna
LandOfFree
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