Polyester Composition for Beverage Containers
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Solution Overview
Problem
Polyester compositions that improve one of the key properties such as natural stretch ratio, crystallization rate, or fill injection rate often detrimentally affect the remaining properties, making it challenging to achieve desirable injection molding properties while maintaining good crystallization rates and natural stretch ratio characteristics, particularly in the production of beverage containers.
Innovation Solution
A polyester composition comprising at least 90 mol % terephthalic acid residues and 90 mol % ethylene glycol residues, with additional diethylene glycol and hydroxyl comonomer residues, achieving a molar ratio of total comonomer residues to diethylene glycol residues of 1.3:1.0 or greater, and an intrinsic viscosity between 0.40 dL/g and 0.77 dL/g, which reduces diethylene glycol content and minimizes acetaldehyde residual, enhancing injection molding efficiency and product quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the crystallization rate is slowed to maintain clarity and reduce crystallinity in preforms, then transparency is improved, but the fill injection rate deteriorates due to higher intrinsic viscosity requirements
Solution Approach 1:
The patent applies parameter changes by precisely controlling the intrinsic viscosity within 0.60-0.75 dL/g and limiting diethylene glycol content to 1.5-2.5 mol%, while maintaining specific comonomer ratios. This optimized parameter range allows the polymer to achieve both slow crystallization (for transparency) and adequate fill injection rate (for productivity), resolving the contradiction between clarity and production efficiency
Solution Approach 2:
The patent uses composite material composition by incorporating multiple comonomers (cyclohexanedimethanol, 1,4-cyclohexanedicarboxylic acid, and diethylene glycol) in specific proportions alongside ethylene glycol and terephthalic acid. This composite approach creates a polymer with balanced properties: the comonomers modify crystallization behavior for transparency while the controlled viscosity ensures adequate fill injection rate
2Productivity
If the intrinsic viscosity is reduced to improve fill injection rate and reduce injection pressure, then manufacturing cost is improved, but the natural stretch ratio deteriorates
Solution Approach 1:
The patent optimizes the intrinsic viscosity parameter to a specific range of 0.60-0.75 dL/g, which is higher than the minimum needed for fill injection but lower than conventional values. This controlled parameter change maintains adequate fill injection rate while preserving the natural stretch ratio through balanced polymer chain structure and comonomer composition
3Productivity
If diethylene glycol content is reduced to improve injection molding properties and reduce acetaldehyde residual, then injection molding efficiency is improved, but the natural stretch ratio may be affected
Solution Approach 1:
The patent controls diethylene glycol content within 1.5-2.5 mol%, which is a moderate reduction from conventional levels. This parameter optimization reduces acetaldehyde residual and improves injection molding efficiency while the compensating effect of comonomers (cyclohexanedimethanol and 1,4-cyclohexanedicarboxylic acid) maintains the natural stretch ratio through modified polymer chain flexibility and intermolecular interactions
Data Source
AI summary
Polyester compositions having desirable injection molding properties and that retain good crystallization rates and natural stretch ratio characteristics are described. These polyesters are suitable for the manufacture of beverage containers, bulk continuous filaments, and other articles that can benefit from such improved properties.