MXPA00000853A - Large polyester containers and method for making same - Google Patents

Abstract

The present application relates to a large molded polyester container weighing greater than about 200, and preferably between about 200 and about 800 grams. Specifically, the present application relates to polyester containers having a volume of several gallons. In one embodiment the container is a bottle formed from a diacid component comprising up to about 96.5 mol%therephthalic acid or naphtalene dicarboxylic acid and a glycol component, wherein said polyester possesses an IV of about 0.75 to about 0.85.

Description

LARGE POLYESTER CONTAINERS AND METHOD OF MAKING THEM DESCRIPTION OF THE INVENTION This application claims the benefit of United States Provisional Application No., Serial No. 60 / 053,717 filed July 25, 1997. The present invention relates to polystyrene compositions suitable for making highly expanded blow molded containers (1-10 gallons). A process for making large containers is also described. The standard PET bottle polymer typically has an intrinsic viscosity or IV in the range of 0.76 to 0.84 dl / g. Modification of the copolymer (acid or glycol) has been used to lower the crystallization ratio and extend the processed window by injection molding. Standard PET bottle polymers with copolymer modification typically have between 0% and 6% IPA modification, or 0% and 3% CHDM modification to reduce the crystallization ratio and allow the production of clear preforms weighing up to 100 grams . The processing equipment and technology have been developed to produce blow molded bottles of expansion that weigh over 800 grams specifically for the volume supplied to the bottled water market. The use of blow molding technology provides advantages in the production performance and the final quality of the bottle thread. However, this equipment has been limited to the use of amorphous resins, such as polycarbonate, to maintain the desired clarity in the preforms and bottles. The use of a crystallizable polyester, such as PET, in an expansion blow molding application can give important advantages when compared to the use of an amorphous polymer. Specifically, the crystallizable polyester can be oriented, or mechanically expanded to give dramatically improved mechanical properties and breaking strength to reduce the weight of the bottle. Using the standard PET bottle polymer formulations in these large vessels, however, results in either the formation of crystalline turbidity in the areas of bottle thickness, or narrow window processing during the production of preforms and bottles. The present invention relates to a highly expanded 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 more than about two gallons to about 10 gallons. The specific containers of the present invention are formed of polyesters formed of a diacid component comprising above about 96.5% terephthalic acid or naphthalenedicarboxylic acid and a glycol component, wherein the polyester has an IV of about 0.75 to about 0.85. The described polyesters have improved crystallization and expansion characteristics. The compositions of the present invention generally possess an IV of from about 0.75 to about 0.85 and a modification of the copolymer of about 3.5 mole% above about 20 mole%. More specifically, the compositions of the present invention comprise copolymer modifications from about 4 mol% to about 10 mol% CHDM; about 6 mol% to about 17 mol% of _IPA and mixtures thereof (greater than that of the standard PET bottle polymer). The net effects were a PET bottle polymer with significantly reduced crystallization ratio, increased expansion ratios, and otherwise acceptable processing performance. It will be understood that the desired crystallization and expansion characteristics can be obtained utilizing any combination of IV and modification, such as high IV, and modification of lower or lower IV polymer and high polymer modification.

Polyesters with optimized crystallization and expansion characteristics have been shown to possess the processing characteristics needed to make 5 gallons, PET blow molded expansion bottles with excellent physical properties and acceptable bottle appearance (clarity). The decreased crystallization ratio results in the ability for thick-walled preforms of clear injection molding at the desired processing conditions. The high expansion ratios result in a sufficient orientation to give the bottles excellent physical properties, even at the temperatures of blow molding of compressed air necessary to avoid the formation of crystalline turbidity during the process of molding by insufflation of compressed air for larger containers, greater than about 200, preferably greater than about 600 grams. ~~ Any polyester composition that is suitable for making a bottle can be used as long as the appropriate amount of modification of the copolymer is present. Examples of suitable polyesters include poly (ethylene terephthalate), poly (ethylene naphthalenedicarboxylate), which comprise about 4 mol% to about 10 mol% CHDM, or about 6 mol% to about 17 mol% IPA. and mixtures thereof. Polyester compositions suitable for the present invention may also contain above about 50% mol of modifying dibasic acids and / or glycols other than CHDM and IPA, and more preferably above about 20% and more preferably above 10% by mol . The modifying dibasic acids may contain from about 2 to about 40 carbon atoms, and preferably include aromatic dicarboxylic acids which preferably have 8 to 14 carbon atoms, aliphatic dicarboxylic acids, which preferably have 4 to 12 carbon atoms, or cycloaliphatic dicarboxylic acids which preferably have 8 to 12 carbon atoms. Examples of dicarboxylic acids to be included with terephthalic acid are: italic acid, naphthalene-2,6-dicarboxylic acid, cyclohexanedicarboxylic acid, cyclohexanediacetic acid, diphenyl-4,4'-dicarboxylic acid, succinic acid, glutaric acid, adipic acid, acid azelaic, sebacic acid and the like. Examples of dicarboxylic acids to be included with naphthalenedicarboxylic acid are: terephthalic acid, italic acid, naphthalene-2-dicarboxylic acid, cyclohexanedicarboxylic acid, cyclohexanediacetic acid, diphenyl-4-dicarboxylic acid, succinic acid, glutaric acid, adipic acid, acid azelaic, sebacic acid, and the like. The polyesters can 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 about 10 to about 94 mol% ethylene glycol. The glycol component can be further modified with the modification of glycol component including, but 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, propan-1,3-diol, butan-1,4-diol, pentan-1,5-diol, hexan-1,6-diol, 3-methylpentanediol- (2, 4) , 2-methylpen tandiol- (1, 4), 2, 2, 4-trimethylpentan-diol- (1, 3), 2-ethylhexan-diol- (1, 3), 2, 2-diethylpropan-diol- ( 1, 3), hexanediol- (1, 3), 1,4-di (hydroxyethoxy) -benzene, 2,2-bis- (4-hydroxy-clohexyl) -propane, 2,4-dihydroxy-1, 3, 3-tetramethyl-cyclobutane, 2,2-bis- (3-hydroxyethoxyphenyl) -propane, and 2,2-bis- (4-hydroxypropoxyphenyl) -propane. The polyesters can be prepared from two or more of the above diols. The resin may also contain small amounts of trifunctional or tetxaJLunctional comonomers, such as trimellitic anhydride, trimethylolpropane, pyromellitic dianhydride, pentaerythritol, and another polyester that forms psylla acids or polyols generally known in the art.

Highly useful naphthalenedicarboxylic acids include 2,6, 1,4- 1,5- or 2,7-isomers, but 1,2-, 1,3-, 1,6-, 1,7-, 1 , 8-, 2,3-, 2,4-, 2,5- and / or 2, 8-isomers can also be used. The dibasic acids can be used in acid form or as their esters such as dimethyl esters for example. The polyesters of this invention are readily prepared using polycondensation reaction conditions well known in the art. Typical polyesterification catalysts that may be used include titanium alkoxides, dibutyltin dilaurate, and antimony oxide or antimony triacetate, used separately or in combination, optionally with zinc, manganese, or magnesium acetates or benzoates and / or Other catalyzed materials are well known to those skilled in the art. The phosphorus and cobalt compounds may also optionally be present. Although it is preferred to use continuous polycondensation reactors, batch reactors operated in series can also be used. Other components such as nucleating agents, branching agents, colorants, pigments, fillers, antioxidants, ultraviolet light and heat stabilizers, impact modifiers, improved superheating aids, crystallization aids, additives to reduce acetaldehyde and the like can be used if desired and to extend them, without deteriorating the objectives of the present invention. The bottles of the present invention are produced using an expansion blow molding process. The blow molding of expansion is achieved in two distinct stages; first, the polyester is melted in an extruder and injected into a mold that forms a parison; Second, the preform is then blown into the final shape of the bottle. The actual blowing of the preform can occur at a slightly earlier temperature - at the glass transition temperature of the polyester. In a "single stage" the preform of the SBM process is transferred from the injection molding directly to a blow molding station; during the transferred time, the preform cools to the proper blow molding temperature. In a "second stage" the SBM process preform is made from the injection mold and then maintained at ambient temperatures for a long enough time to achieve a temperature consistent with the fate of the preforms; and then, in a separate process, it is superheated to the proper blow molding temperature before being blown in the shape of the bottle. The specific type of process used is determined by the volume of production, or the desired production ratio for a specific application; and the design of the machine and capabilities. It is well known that polyesters exhibit a dramatic improvement in physical properties when mechanically dilating or orienting. During the SBM process with a crystallizable polymer, this mechanical expansion occurs when the preform is blow molded into the final bottle shape. The preform design and SBM processing conditions are used to impart the desired level of mechanical expansion (expansion ratio) to the side walls of the bottle and base; and this determines many of the physical properties of the bottle. These physical properties are generally more improved over those found in containers that have not been mechanically oriented, such as those made of an amorphous polymer. Flat expansion ratios ranging from approximately 11 to 13 are commonly used in polyester bottles that require excellent physical properties, and are considered standard practices in the industry. To gain the advantages of increased mechanical orientation and to reduce raw material costs, bottle manufacturers and equipment suppliers are made to investigate methods and equipment to produce large SBM containers in sizes ranging from 1 to 10 gallons. Nevertheless, the tendency of the standard PET bottle polymer to form crystalline turbidity during the -mold injection of thick-wall preforms, and the tendency to form crystalline turbidity at high blow molding temperatures needs to achieve the desired expansion ratios during the Blow molding of large containers have limited use of PET in these large SBM applications. Bottle producers have been forced to use amorphous polymers, such as psicabbonate, in the SBM process, which results in significantly high raw material costs and small or no increase in typical physical properties derived from mechanical orientation. - Efforts to produce very large containers using blow molding expansion processes have been hampered not only by the crystallization characteristics, but also by the expansion characteristics of the PET formulas and their effect on processing. To make a very large PET container, the preform can be designed with the correct range of dimensions that allow the production of a bottle with the desired material distribution and thickness, and also gives an acceptably wide processing window in the molding stages by injection and blow molding. The PET preform can be to have a "natural expansion ratio", or NSR at a given blow molding temperature,; to the point at which PET is self-leveling and "plastic deformation hardening" The expansion follows the NSR at a blow molding temperature given that it imparts improved physical properties, but much expansion causes a loss of clarity and delamination (typically called pearlescence). , or point of pearl.) The PET expansion characteristics are highly dependent on several resin factors, mainly: IV (molecular weight) and copolymer content.In general, as the IV decreases and the copolymer content increases the NSR and the temperature at which the pearlescence is increased.When increasing the NSR or PET for use in large SMB vessels, it is then possible to achieve adequate material distribution and mechanical orientation at a lower blow molding temperature that could expected with standard PET bottle polymers, this results in the ability to use preforms optimally designed and to avoid the formation of crystalline turbidity during the blow molding process for large SMB containers. The polyesters of the present invention exhibit superior crystallization (reduced crystallization ratio, turbidity formation, etc.) and expansion characteristics (high natural expansion ratio, increased free blowing volume, etc.), which allows (or increases) ~ window processing) for the production of large expansion blow molding (mechanically oriented), PET bottles using blow molding expansion equipment (SBM) or SMB equipment technology. The bottles of the present invention exhibit increased clarity, improved physical properties, and improved processability that allows the production of large containers. Large bottles that have surprisingly good physical properties and clarity are also described. Accordingly, the present invention further relates to containers that are made of polyesters formed by balancing the IV with the copolyester modification and preferably, comprising an Iv of from about 0.75 to about 0.85 dl / g and about 3.5% by weight of about 20 mol% of the copolymer modification. The bottles of the present invention exhibit surprisingly good physical properties and the desired level of clarity, as well as improved processing characteristics and yield yield. The reduction of the crystallization ratio allows the use of crystallizable polyesters in the production of extremely large containers in the expansion blow molding equipment; which results in an opportunity to improve the physical properties by increasing the mechanical expansion, or orientation, while maintaining the clarity of the desired container. The modification of the increased copolymer will not only decrease the crystallization ratio, but also increase the natural expansion ratio at lower blow molding temperatures. This increase in natural expansion ratio is important to optimize the preform design for good material distribution and acceptable orientation, while maintaining the blow molding temperature quite low to avoid crystalline cloud formation during the molding step. blown-production. Specifically, the present invention relates to a large container that is crystallized and biaxially oriented, such as by force molding and formed from the polyester described above. The present invention further relates to a process for forming large containers comprising providing a polyester having the composition defined above, a tangential expansion ratio at 212 ° F of more than about 5.0 and an average crystallization time sufficient for molding by injection a thick-walled preform without the formation of crystalline turbidity. The process further comprises the step of blowing blow-molding the preform under suitable conditions to form the bottle without forming crystalline turbidity during the blow-molding step.

Claims (12)

1. CLAIMS 1. A polyester container blow molded, clear, weighing more than about 200 grams characterized in that the polyester is formed of poly (ethylene terephthalate), or poly (ethylene naphthalenedicarboxylate), comprising about 4% by weight. mol to about 10 mol% CHDM, or about 6 mol% to about 17 mol% IPA, or mixtures thereof, wherein the polyester has an IV of from about 0.75 to about 0.85. The container according to claim 1, characterized in that the diacid further comprises up to about 50 mol% of the dibasic acid modifiers other than IPA. 3. The container according to claim 1, characterized in that the diacid further comprises up to about 20 mol% of the dibasic acid modifiers other than IPA. 4. The container according to claim 1, characterized in that the diacid further comprises up to about 10 mol% of dibasic acid modifiers other than IPA. The container according to claim 2, characterized in that the dibasic acid-modifier is selected from the group consisting of aromatic dicarboxylic acids having 8 to 14 carbon atoms, aliphatic dicarboxylic acids having from 4 to 12 carbon atoms, or cycloaliphatic dicarboxylic acids having from 8 to 12 carbon atoms. 6. The container according to claim 5, characterized in that the modified dibasic acid is selected from the group consisting of phthalic acid, terephthalic acid, naphthalene-2,6-dicarboxylic acid, cyclohexanedicarboxylic acid, cyclohexanediacetic acid, diphenyl-4 acid , 4'-dicarboxylic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid and mixtures thereof. The container according to claim 1, characterized in that the glycol component further comprises modifying glycols selected from the group consisting of cycloaliphatic diols having 6 to 20 atoms or aliphatic diols having 3 to 20 carbon atoms. The container according to claim 7, characterized in that the modifying glycol is selected from the group consisting of diethylene glycol, triethylene glycol, propan-1,3-diol, butan-1,4-diol, pentan-1,5-diol , hexan-1, 6-diol, 3-methylpentanediol- (2, 4), 2-methyl-pentanediol- (1, 4), 2, 2, 4-trimethylpentan-diol (1, 3), 2-ethyl- hexandiol- (1, 3), 2, 2-diethylpropan-diol- (1, 3), hexanediol- (1,3), 1,4-di- (hydroxyethoxy) -benzene, 2, 2-bis (4- hydroxyl-cyclohexyl) -propane, 2,4-dihydroxy-1,3,3-tetramethyl-cyclobutane, 2,2-bis- (3-hydroxyethoxyphenyl) -propane, 2, 2-bis (-4- hydroxy-poxyphenyl) -propane and mixtures thereof. 9. A method comprising forming a preform of between about 200 and about 800 grams of a polyester formed from poly (ethylene terephthalate) or poly (ethylene naphthalate carboxylate) comprising about 4 mol% to about 10 mol% of CHDM, or about 6 mole% to about 17% mole of "IPA, or mixtures thereof, wherein the polyester has an IV of from about 0.75 to about 0.85, and blow molding of preform expansion into A container 10. The method according to claim 9, characterized in that the glycol component further comprises ethylene glycol 11. The method according to claim 10, characterized in that the diacid further comprises up to about 50% mol of acids ^ dibasic modifiers other than IPA 12. The method according to claim 19, characterized in that the glycol component also comprises modified glycols. selected from the group consisting of cycloaliphatic diols having 6 to 20 carbon atoms or aliphatic diols having 3 to 20 carbon atoms.