Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
1998-06-29
2001-10-30
Pyon, Harold (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S036920, C528S271000, C528S272000
Reexamination Certificate
active
06309718
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to polyester compositions suitable for making large (1-10 gallon) stretch blow molded containers. A process for making large containers is also disclosed.
BACKGROUND OF THE INVENTION
Standard PET bottle polymer typically has an intrinsic viscosity, or IV in the range of 0.76 to 0.84 dl/g. Copolymer modification (acid or glycol) has been used to decrease the crystallization rate and widen the injection molding processing window. Standard PET bottle polymers with copolymer modification typically have between 0% and 6% IPA modification, or 0% and 3% CHDM modification in order to reduce the crystallization rate and allow the production of clear preforms weighing up to 100 grams.
Processing equipment and technology have been developed to produce stretch blow molded bottles weighing up to 800 grams specifically for the bulk delivered bottled water market. The use of stretch blow molding technology provides advantages in production output and bottle thread finish quality. However, this equipment has been limited to the use of amorphous resins, such as polycarbonate, in order to maintain the desired clarity in the preforms and bottles.
The use of a crystallizable polyester, such as PET, in a stretch blow molded application can give important advantages when compared to the use of an amorphous polymer. Specifically, the crystallizable polyester can be oriented, or mechanically stretched to give dramatically improved mechanical properties and crack resistance at reduced bottle weight. Using standard PET bottle polymer formulations in these large containers, however, results in the either the formation of crystalline haze in the thicker areas of the bottle, or a very narrow processing window during the production of the preforms and bottles.
DESCRIPTION OF THE INVENTION
The present invention relates to large stretch blow molded polyester containers, generally weighing between about 200 and about 800 grams. The containers of the present invention are generally capable of holding several gallons, specifically from about one to about 10 gallons, and preferably from greater than about two gallons to about 10 gallons. Specifically containers of the present invention are formed from polyesters formed from a diacid component comprising up to about 96.5 mol % terephthalic acid or naphthalene dicarboxylic acid and a glycol component, wherein said polyester possesses an IV of about 0.75 to about 0.85. The disclosed polyesters have improved crystallization and stretching characteristics.
The compositions of the present invention generally possess an IV of about 0.75 to about 0.85 and copolymer modification of about about 3.5 mol % up to about 20 mol %. More specifically, the compositions of the present invention comprise copolymer modifications of about 4 mol % to about 10 mol % CHDM; about 6 mol % to about 17 mol % IPA and mixtures thereof (higher than that of standard PET bottle polymer). The net effect was a PET bottle polymer with significantly reduced crystallization rate, increased stretch ratios, and otherwise acceptable processing performance. It should be understood that the desired crystallization and stretching characteristics can be obtained using any combination of IV and modification, such as higher IV and lower copolymer modification or lower IV and higher copolymer modification.
Polyesters with optimized crystallization and stretching characteristics have been shown to possess the processing characteristics necessary to make 5 gallon, stretch blow molded PET bottles with excellent physical properties and acceptable bottle appearance (clarity). The decreased crystallization rate results in the ability to injection mold clear thick-walled preforms at the desired processing conditions. The higher stretch ratios result in enough orientation to give the bottles excellent physical properties, even at the lower blow molding temperatures necessary for avoiding the formation of crystalline haze during the blow molding process for large, greater than about 200, preferably greater than about 600 gram containers.
Any polyester composition which is suitable for making a bottle may be utilized so long as the appropriate amount of copolymer modification is present. Examples of suitable polyesters include poly(ethylene terephthalate), poly(ethylene naphthalenedicarboxylate) comprising about 4 mol % to about 10 mol % CHDM, or about 6 mol % to about 17 mol % IPA, and mixtures thereof. The polyester compositions suitable for the present invention may also containing up to about 50 mol % of modifying dibasic acids and/or glycols other than CHDM and IPA, and more preferably up to about 20% and most preferably up to about 10 mol %. Modifying dibasic acids may contain from about 2 to about 40 carbon atoms, and preferably include aromatic dicarboxylic acids preferably having 8 to 14 carbon atoms, aliphatic dicarboxylic acids preferably having 4 to 12 carbon atoms, or cycloaliphatic dicarboxylic acids preferably having 8 to 12 carbon atoms. Examples of dicarboxylic acids to be included with terephthalic acid are: phthalic acid, naphthalene-2,6-dicarboxylic acid, cyclohexanedicarboxylic acid, cyclohexanediacetic acid, diphenyl-4,4′-dicarboxylic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and the like. Examples of dicarboxylic acids to be included with naphthalenedicarboxylic acid are: terephthalic acid, phthalic acid, naphtbalene-2,-dicarboxylic acid, cyclohexanedicarboxylic acid, cyclohexanediacetic acid, diphenyl-4,4′-dicarboxylic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and the like. Polyesters may be prepared from two or more of the above dicarboxylic acids.
The glycol component of the present invention comprises about 4 mol % to about 10 mol % CHDM and from about 10 to about 94 mol % ethylene glycol. The glycol component may be further modified with additional modifying glycol components which include, but are not limited to cycloaliphatic diols preferably having 6 to 20 carbon atoms or aliphatic diols preferably having 3 to 20 carbon atoms. Examples of such diols include diethylene glycol, triethylene glycol, propane-1,3-diol, butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol, 3-methylpentanediol-(2,4), 2-methylpentanediol-(1,4), 2,2,4-trimethylpentane-diol-(1,3), 2-ethylhexanediol-(1,3), 2,2-diethylpropane-diol-(1,3), hexanediol-(1,3), 1,4-di-(hydroxyethoxy)-benze, 2,2-bis-(4-hydroxycyclohexyl)-propane, 2,4-dihydroxy-1,1,3,3-tetramethyl-cyclobutane, 2,2-bis-(3-hydroxyethoxyphenyl)-propane, and 2,2-bis4-hydroxypropoxyphenyl)-propane. Polyesters may be prepared from two or more of the above diols.
The resin may also contain small amounts of trifunctional or tetrafunctional comonomers such as trimellitic anhydride, trimethylolpropane, pyromellitic dianhydride, pentaerythritol, and other polyester forming polyacids or polyols generally known in the art.
Highly useful naphthalenedicarboxylic acids include the 2,6-, 1,4-, 1,5-, or 2,7-isomers but the 1,2-. 1.3-, 1,6-, 1,7-, 1,8-, 2,3-, 2,4-, 2,5-, and/or 2,8-isom may also be used.
The dibasic acids may be used in acid form or as their esters such as the dimethyl esters for example.
The polyesters of this invention are readily prepared using polycondensation reaction conditions well known in the art. Typical polyesterification catalysts which may be used include titanium alkoxides, dibutyl tin dilaurate, and antimony oxide or antimony triacetate, used separately or in combination, optionally with zinc, manganese, or magnesium acetates or benzoates and/or other such catalyst materials as are well known to those skilled in the art. Phosphorus and cobalt compounds may also optionally be present. Although we prefer to use continuous polycondensation reactors, batch reactors operated in series may also be used.
Other components such as nucleating agents, branching agents, colorants, pigments, fillers, antioxidants, ultraviolet light and heat stabilizers, impact modifiers, reheat improving aids, crystallization aids, acetaldehyde
Eastman Chemical Company
Graves, Jr. Bernard J.
Harding Karen A.
Nolan Sandra M.
Pyon Harold
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