Polyester Composition Stress Crack Resistance
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Solution Overview
Problem
Current polyester bottle resins face challenges in achieving adequate stress crack resistance while maintaining a balance of intrinsic viscosity (IV) and carboxyl end groups, which affects manufacturing costs and performance characteristics such as dimensional stability and burst strength.
Innovation Solution
A polyester composition with an intrinsic viscosity range of 0.65 to 0.78 dl/g and a carboxyl end group concentration of at least 47 mmole/kg, optimized through injection stretch blow molding, provides improved resistance to caustic stress cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high intrinsic viscosity polyester resin (IV > 0.82 dl/g) is used to improve stress crack resistance, then resistance to caustic stress cracking is improved, but manufacturing cost increases due to solid state polymerization process requirements
Solution Approach 1:
The patent applies parameter changes by optimizing the intrinsic viscosity parameter to a specific range (0.72-0.85 dl/g) that provides adequate stress crack resistance without requiring the expensive solid state polymerization process. This parameter optimization resolves the contradiction by finding a middle ground that satisfies both reliability and manufacturing cost requirements.
2Shape
If comonomer is added to decrease crystallization rate of PET, then clarity of preform is improved, but physical properties of copolyester resin become significantly weaker
Solution Approach 1:
The patent applies parameter changes by precisely controlling the comonomer content parameter within a specific range (0.5-2.0 moles per 100 moles of terephthalic acid) to achieve the optimal balance between preform clarity and resin strength. This controlled parameter adjustment prevents excessive crystallization retardation while maintaining adequate physical properties.
3Ease of manufacture
If intrinsic viscosity is reduced to lower manufacturing cost, then manufacturing cost decreases, but resistance to caustic stress cracking deteriorates
Solution Approach 1:
The patent applies parameter changes by establishing a minimum intrinsic viscosity threshold (0.72 dl/g) that ensures adequate stress crack resistance while avoiding the need for expensive solid state polymerization. This parameter boundary defines the optimal cost-performance tradeoff point.
Solution Approach 2:
The patent applies composite materials by creating a copolyester composition with specific comonomer content (0.5-2.0 moles per 100 moles of terephthalic acid) that modifies the polymer structure to achieve adequate mechanical properties and stress crack resistance at lower intrinsic viscosity levels, thereby reducing manufacturing costs while maintaining reliability.
Data Source
AI summary
Polyester compositions for use in injection stretch blow molded articles having intrinsic viscosities in the range from about 0.65 to about 0.78 dl/g, and carboxyl end group concentrations of about 47 mmole/kg or more are provided. Stretch blow molded articles formed from these polyester compositions and methods to produce these articles are also described.