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
2000-06-14
2003-04-15
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...
C524S186000, C501S148000
Reexamination Certificate
active
06548587
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to a polymer-clay composition having improved gas permeability comprising a clay material and at least one organic cation. More particularly, this invention relates to a polyamide composition comprising layered clay material modified with an alkoxylated onium compound. This invention further relates to articles produced from the composition, and a process for preparing the composition.
BACKGROUND OF THE INVENTION
Polymer-platelet particle composites have received much attention lately due to their potential to improve polymer properties, including gas barrier, heat deflection temperature, and modulus.
U.S. Pat. No. 4,739,007 discloses composite materials comprising a polyamide matrix and a well dispersed, layered silicate material that is incorporated during polymerization and imparts high mechanical strength and excellent high temperature properties.
U.S. Pat. No. 5,385,776 discloses composite materials comprising a Nylon-6 matrix and a minor amount of a layered silicate material that is incorporated during melt extrusion and imparts rapid nucleation of the polyamide into the gamma crystal structure thereby improving modulus and resistance to plasticization by water.
U.S. Pat. No. 4,810,734 discloses nylon composites comprising a layered silicate material that has been treated with certain organic ammonium compounds and incorporated by synthesis using a dispersing aid.
PCT application WO 93/04117 discloses composite materials comprising a polyamide matrix and a layered silicate material that has been modified with certain primary or secondary organic ammonium compounds incorporated during melt extrusion and impart improved modulus to the polymer composite.
PCT application WO 93/11190 discloses Nylon composites comprising a layered silicate material that may optionally contain certain organic ammonium compounds, WHICH ARE TREATED WITH certain silane compounds and incorporated by melt blending.
Journal of Applied Polymer Science
, Vol. 71 (1999), pg. 1139-1146, discloses the rapid crystallization of composite materials comprising a polyethylene terephthalate (“PET”) matrix and an undisclosed clay material.
PCT application WO 98/29499 discloses high molecular weight polyester-platelet particle composites prepared by solid state polymerization of precursor composites prepared by incorporation of treated layered silicate materials by synthesis and by melt compounding. The use of alkoxylated ammonium compounds to pretreat the layered silicate is specifically disclosed.
PCT application WO 99/02593 discloses polyester composites comprising layered silicate materials that are treated with at least one polyalkoxylated ammonium salt comprising alkoxy ligands with greater than 5 alkyl oxide repeat units.
PCT application WO 96/08526 discloses thermoset epoxy resin composites comprising a mica-type layered silicate that is treated with tallow bis(2-hydroxyethyl)methyl ammonium salts.
Additional publications describing polymer nanocomposites comprising a polyamide matrix and dispersed layers of silicate include 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.
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. Pat. No. 4,018,746. However, these patents do not disclose or suggest incorporation of a clay material into such amorphous polyamide to improve the barrier propertis 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.
It has been found that polymer-platelet particle composites of both polyethylene terephthalate (“PET”) and polyamides often exhibit rapid crystallization, which has been attributed to nucleation of the polymer matrix by the platelet particles. Clay particles in a nylon-6 nanocomposite, for example, induce crystallization, as described in U.S. Pat. No. 5,385,776. This can be an advantage for applications involving opaque, crystalline molded parts, as well as for imparting improved heat resistance and modulus to the parts. Examples of such opaque crystalline composites are the nylon composites disclosed in U.S. Pat. Nos. 5,385,776 and 4,739,007, and the PET composites discussed
in Journal of Applied Polymer Science
, Vol. 71 (1999), pg. 1139-1146.
However, rapid crystallization of polymer-clay composites is not always desirable, especially applications including, but not limited to, profile extrusion, extrusion blow molding, stretch blow molding, film extrusion, and blown film, and other applications where optical clarity of the composite is desired, and especially in two step molding applications. The rapid crystallization of prior art polymer-clay composites makes it difficult, if not impossible, to obtain clear multilayer preforms and/or blow molded containers and bottles, wherein the ability to further process an initially formed article is important. Rapid crystallization greatly reduces the available processing window when prior art polymer-clay composites are employed in conjunction with PET in the molding of clear plastic bottles.
Multilayer materials for packaging are known for film, bottles, and other containers. Multilayer injection molded preforms described, for example, in European Patent Application No. 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.
Therefore, there remains a need in the art for improving the gas barrier properties of polyamide composite materials, without adversely affecting their rheological properties and processability in conjunction with PET. There also remains a need in the art for an amorphous polyamide nanocomposite having good clarity and reduced haze. It is, therefore, desirable to significantly improve the barrier properties of polyamides using nanocomposite technology without markedly increasing their crystallization rate.
SUMMARY OF THE INVENTION
In accordance with the purpose(s) of this invention, as embodied and broadly described herein, this invention relates to composite compositions comprising polyamide polymers or copolymers, and certain layered clay materials, having alkoxylated “onium” cations associated therewith.
In another embodiment, this invention relates to processes for preparing the compositions, involving the steps of treating a layered clay material with at least one salt having certain alkoxylated “onium”, to form a treated layered clay material, then mixing the treated layered clay material with a polymer composition comprising at least one polyamide polymer or copolymer.
Additional advantages of the invention will be set forth in part in the detailed description, 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 processes a
Bagrodia Shriram
Bernard Linda Gail
Gilmer John Walker
Lan Tie
Matayabas, Jr. James Christopher
Cain Edward J.
Deveau Todd
Haley Jacqueline
Troutman Sanders LLP
University of South Carolina Research Foundation
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