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
2000-08-02
2004-08-17
Wyrozebski, Katarzyna (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, C524S398000, C524S413000, C524S435000, C524S431000
Reexamination Certificate
active
06777479
ABSTRACT:
BACKGROUND OF INVENTION
MXD6 is a commercially available partially-aromatic nylon prepared from adipic acid and meta-xylene diamine, and is also available as a copolyamide with comonomers including isophthalic acid. MXD6 and copolyamides are preferred barrier materials for use in multilayer PET bottles due to their similar processing conditions and rheology to PET and due to their improved resistance to delamination from PET compared to EVOH. However, their use is limited because bottles comprising MXD6 as a blend or as one or more discrete layers with, for example, PET have insufficient barrier for packaging highly oxygen sensitive food and/or are not recyclable in processes established for mono-layer PET bottles due to the large amount of MXD6 that is required.
Platelet particles have been incorporated to improve the passive oxygen barrier of MXD6; however, relatively large amounts of the MXD6-platelet particle composite are still needed to achieve the desired oxygen barrier and, therefore, the bottles are still difficult, if not impossible to recycle.
Certain transition metal catalysts have been added to MXD6 to impart oxygen scavenging capability (active barrier), which greatly reduces the amount of MXD6 needed. However, most food and beverage products require high gas barrier properties to more than just oxygen. For example, beer bottles require high oxygen barrier to protect the beer and require high carbon dioxide barrier to contain the desired carbon dioxide within the package. Active scavenger approaches often fall short of meeting the barrier requirements other than or require the use of such a large amount of oxygen scavenging MXD6 that the bottles are difficult or impossible to recycle.
PRIOR ART
U.S. Pat. No. 4,739,007 discloses composite materials comprising a polyamide matrix and a dispersed layered silicate material that is incorporated during polymerization and imparts high mechanical strength and excellent high temperature properties.
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 to impart improved modulus to the polymer composite.
PCT application WO 93/11190 discloses nylon composites comprising a layered silicate material that has been treated first with certain organic ammonium compounds then with certain silane compounds and incorporated by melt blending.
US 97124103 discloses polymer composites comprising a layered silicate material that has been treated first with certain organic ammonium compounds then with an expanding agent and incorporated by synthesis or by melt blending.
U.S. Pat. Nos. 5,021,515 and 5,034,252 disclose high barrier containers comprising mixtures of PET and nylon comprising a transition metal oxygen scavenging catalyst. U.S. Pat. No. 5,077,111 discloses recyclable multilayer preforms and bottles comprising a total of 1-8 wt % of MXD6 comprising a cobalt salt that catalyzes oxygen scavenging. This patent suggests that when the total content of MXD6 is less than or equal to the preferred amount of 4 wt % that the bottles are recyclable. In practice, however, it has been found that bottles comprising less than about 4 wt % of MXD6 have insufficient barrier to carbon dioxide to meet the preferred barrier requirements for packaging products that require high gas barrier to oxygen plus one or more other gasses, such as beer. Beer brewing companies have published their preferred gas barrier requirements—see for example Norm Nieder “Is Plastic Ready for Beer,” Proceeding of the 3
rd
International Conference on Rigid Polyester Packaging Innovations for Food and Beverages, NovaPak Americas '98. Those requirements include less than 10% loss of carbon dioxide from 2.8-3.0 volumes for about 105-120 days. Bottles prepared as described in the above US patents must comprise more than about 4.5 wt % MXD6 to meet this requirement. Because such large amounts of MXD6 are required, true recyclability is problematical and/or the preferred gas barrier properties are not achieved, which restricts the applications to short term use, such as promotional and stadium events.
DESCRIPTION OF THE INVENTION
This invention relates to polymer-platelet particle composites composed of at least one polymer resin and platelet particles uniformly dispersed therein and products produced from said composite. More specifically, this invention relates to a polymer-platelet particle composite comprised of at least one polyamide resin, at least one oxygen scavenging catalyst, and at least one layered silicate material. Typically, the layered silicate material is treated to enhance dispersibility into the composite. The present invention further relates to a process for forming polymer-platelet particle composites comprising mixing the oxygen scavenging catalyst with the layered silicate material and organic cation to bind the organic cation and oxygen scavenging catalyst to said layered silicate material to form an organoclay and incorporating the organoclay into a polymer. The polymer-platelet particle composites produced according to the present invention are especially useful for preparing clear bottles and film that are recyclable, exhibit improved active gas barrier properties to oxygen, and exhibit improved passive barrier to other gasses. By virtue of their high gas barrier properties, polymer-platelet particle composites produced according to the present invention can be used in relatively minor amounts as either a blend or a very thin layer with PET and related copolymers, either virgin or post consumer recycled, and this low concentration of polymer-platelet particle composite provides the unique combination of good oxygen gas barrier protection, good carbon dioxide barrier retention, and recyclability.
Platelet Particles
The polymer-platelet particle composites of the present invention comprise up to about 30 weight percent, preferably less than about 20 weight percent, of certain platelet particles derived from at least one layered silicate material which has been modified with at least one ammonium compound. The amount of platelet particles is determined by measuring the residual ash of the polymer-platelet particle compositions when treated in accordance with ASTM D5630-94, which is incorporated herein by reference. The gas barrier improvement increases with increasing concentration of platelet particles in the composite. While amounts of platelet particles as low as about 0.01 percent provide improved barrier (especially when well dispersed and ordered), compositions having at least about 0.5 weight percent of the platelet particles are preferred because they display desirable improvements in gas permeability.
Preferred layered silicate materials employed in the invention include any solid material having at least some inorganic anionic atoms, ions, or chemical groups arranged in generally planar layers in the solid state, wherein the spacing between at least some of the generally planar layers are capable of being increased, swelled, or separated by the insertion of inorganic or organic materials there between. Generally layered silicate materials are a dense agglomeration of platelet particles which are closely stacked together like cards. The platelet particles of the present invention have a thickness of less than about 2 nm and a diameter in the range of about 10 to about 5000 nm. For the purposes of this invention, such measurements refer only to the platelet particle and not to the ammonium compounds or any additional dispersing aids and treatment compounds which might be used. Suitable layered silicate material are free flowing powders having a cation exchange capacity between about 0.3 and about 3 meq/g and preferably between about 0.8 and about 1.5 meqg
Bagrodia Shriram
Bernard Linda Gail
Clauberg Horst
Cyr Michael John
Gilmer John Walker
Carmen Dennis V.
Eastman Chemical Company
Graves, Jr. Bernard J.
Wyrozebski Katarzyna
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