Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2002-06-05
2004-03-23
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C428S357000, C428S402000, C428S403000, C428S480000, C524S107000, C524S110000, C536S103000
Reexamination Certificate
active
06709746
ABSTRACT:
FIELD OF THE INVENTION
Container structures can comprise an oriented thermoplastic polyester resin material. Such resins can be a source of reactive organic materials that can be eluted from the packaging into, for example, a food material held within the container. Such reactive materials, including an aldehyde material, can result in undesirable off-odors or off-flavors in a food, or off-taste in water or beverage drink. The invention relates to polyester pellet or chip coated with active materials that can prevent the formation of or scavenge the organic material during preform and bottle manufacturing methods. The invention further relates to the polyester preform comprising thermoplastic polyester and, dispersed in the thermoplastic resin, an active material that can act to prevent the formation of or scavenge volatile organic components. Lastly, the invention relates to a thermoplastic beverage container and methods of making the chip, preform or container.
BACKGROUND OF THE INVENTION
Polyethylene terephthalate (PET) packaging materials in the form of film, shaped containers, bottles, etc. have been known. Further, rigid, or semi-rigid, thermoplastic beverage containers have been made from preforms that are in turn molded from pellets or chips etc. Biaxially oriented blow molded thermoformed polyester beverage containers are disclosed in J. Agranoff (Ed) Modern Plastics, Encyclopedia, Vol. 16, No. 10A, P. (84) pp. 192-194. These beverage containers are typically made from a polyester, a product of a condensation polymerization. The polyester is typically made by reacting a dihydroxy compound and a diacid compound in a condensation reaction with a metallic catalyst. Dihydroxy compounds such as ethylene glycol, 1,4-butane diol, 1,4-cyclohexane diol and other diol can be copolymerized with an organic diacid compound or lower diester thereof such diacid. Such diacidic reactants include terephthalic acid, 2,6-naphthalene dicarboxylic acid, methyl diester thereof, etc. The condensation/polymerization reaction occurs between the dicarboxylic acid, or a dimethyl ester thereof and the glycol material in a heat driven metal catalyzed reaction that releases water or methanol as a reaction by-product leaving, a high molecular weight polyester material. Bulk resin is formed as a convenient flake, chip or pellet adapted for future thermal processing. Bulk polyester material can be injection blow molded directly into a container. Alternately, the polyester can be formed into an intermediate preform that can then be introduced into a blow-molding machine. The polyester is heated and blown to an appropriate shape and volume for a beverage container. The preform can be a single layer material, a bilayer or a multilayer preform.
Metallic catalysts are used to promote a polymerization reaction between diacid material and the dihydroxy compound. At the beginning of the melt phase, ethylene glycol, terephthalic acid, or ester thereof, and metallic catalysts are added to the reactor vessel. Various catalysts are known in the art to be suitable for the transesterification step. Salts of organic acids with bivalent metals (e.g. manganese, zinc, cobalt or calcium acetate) are preferably used as—direct esterification or trans-esterification catalysts, which in themselves also catalyze the polycondensation reaction. Antimony, germanium and titanium compounds are preferably used as polycondensate catalysts. Catalysts that may be used include organic and inorganic compounds of one or more metals alone or in combination with the above-described antimony, also including germanium and titanium. Suitable forms of antimony can be used, including inorganic antimony oxides, and organic compounds of antimony, such as antimony acetate, antimony oxalate, antimony glycoxide, antimony butoxide, and antimony dibutoxide. Antimony-containing compounds are currently in widespread commercial use as catalysts that provide a desirable combination of high reaction rate and low color formation. Titanium may be chosen from the group consisting of the following organic titanates and titanium complexes: titanium oxalate, titanium acetate, titanium butylate, titanium benzoate, titanium isoproprylate, and potassium titanyl oxalate. Organic titanates are not generally used in commercial production. At the end of the melt phase, after polymerization is complete and molecular weight is maximized, the product is pelletized. The pellets are treated in solid-state polycondensation to increase intrinsic viscosity in order to obtain bottle resin of sufficient strength. The catalysts typically comprise metallic divalent or trivalent cations. The treatment of polyester materials containing such catalysts can result in byproduct formation. Such byproduct can comprise reactive organic materials such as an aldehyde material, commonly analyzed as acetaldehyde. The formation of acetaldehyde materials can cause off odor or off taste in the beverage and can provide a yellowish cast to the plastic at high concentrations. Polyester manufacturers have added phosphorus-based additives as metal stabilizers to reduce acetaldehyde formation. Many attempts to reduce aldehyde formation have also caused problems. Antimony present as Sb
+1
, Sb
+2
and Sb
+3
in the polyester as catalyst residues from manufacture can be reduced to antimony metal, Sb
0
, by the additives used to prevent aldehyde formation or scavenge such materials. Formation of metallic antimony can cause a gray or black appearance to the plastic from the dispersed, finely divided metallic residue.
The high molecular weight thermoplastic polyester can contain a large variety of relatively low molecular weight compound, (i.e.) a molecular weight substantially less than 500 grams per mole as a result of the catalytic mechanism discussed above or from other sources. These compounds can be extractable into food, water or the beverage within the container. These beverage extractable materials typically comprise impurities in feed streams of the diol or diacid used in making the polyester. Further, the extractable materials can comprise by-products of the polymerization reaction, the preform molding process or the thermoforming blow molding process. The extractable materials can comprise reaction byproduct materials including formaldehyde, formic acid, acetaldehyde, acetic acid, 1,4-dioxane, 2-methyl-1,3-dioxolane, and other organic reactive aldehyde, ketone and acid products. Further, the extractable materials can contain residual diester, diol or diacid materials including methanol, ethylene glycol, terephthalic acid, dimethyl terephthalic, 2,6-naphthalene dicarboxylic acid and esters or ethers thereof. Relatively low molecular weight (compared to the polyester resin) oligomeric linear or cyclic diesters, triesters or higher esters made by reacting one mole of ethylene glycol with one mole of terephthalic acid may be present. These relatively low molecular oligomers can comprise two or more moles of diol combined with two or more moles of diacid. Schiono,
Journal of Polymer Science: Polymer Chemistry Edition
, Vol. 17, pp. 4123-4127 (1979), John Wiley & Sons, Inc. discusses the separation and identification of PET impurities comprising poly(ethylene terephthalate) oligomers by gel permeation chromatography. Bartl et al., “Supercritical Fluid Extraction and Chromatography for the Determination of Oligomers and Poly(ethylene terephthalate) Films”,
Analytical Chemistry
, Vol. 63, No. 20, Oct. 15, 1991, pp. 2371-2377, discusses experimental supercritical fluid procedures for separation and identification of a lower oligomer impurity from polyethylene terephthalate films.
Foods or beverages containing these soluble/extractables derived from the container, can have a perceived off-taste, a changed taste or even, in some cases, reduced taste when consumed by a sensitive consumer. The extractable compounds can add to or interfere with the perception of either an aroma note or a flavor note from the beverage material. Additionally, some substantial concern exists with respect to th
Beaverson Neil J.
Huang Xiaoyan
Lawonn Phillip
Wood Willard E.
Arteva North America S.á.r.l.
Chen Vivian
Merchant & Gould P.C.
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