Polyester-Polyamide Blend Haze Reduction via Refractive Index Matching
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Solution Overview
Problem
Current polyester-polyamide blends used in packaging for oxygen-sensitive products like food and beverages suffer from unacceptable haze when stretched, due to the enlargement of polyamide domains, which affects the aesthetic and barrier properties of the packaging.
Innovation Solution
A polymer composition comprising a crystallizable polyester and a polyamide with a specific interfacial tension reducing agent, such as lithium sulfoisophthalate, is used to reduce the size of polyamide domains, maintaining low haze and color even when stretched, by adjusting the amino to carboxyl end group ratio and relative viscosity of the polyamide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyamide is blended into polyester to create oxygen barrier properties, then gas barrier performance is improved, but haze increases when the material is stretched
Solution Approach 1:
The patent changes the chemical composition parameters of the polyester by incorporating specific comonomers (cycloaliphatic diol, aromatic diacid, or carboxylate group-containing comonomer) to modify the refractive index match with polyamide domains. This parameter change reduces light scattering at the polyester-polyamide interface, thereby reducing haze while maintaining the oxygen barrier properties provided by the polyamide dispersion.
Solution Approach 2:
The patent creates a composite material system consisting of polyester matrix blended with polyamide domains. By carefully selecting and combining specific comonomers with the polyester, the invention optimizes the optical properties of the composite to reduce haze while preserving the functional benefits of polyamide dispersion for oxygen barrier performance.
2Shape
If stretch ratio is increased to improve container shape and fit, then container quality is improved, but haze increases due to domain enlargement
Solution Approach 1:
The patent modifies the optical parameters of the polyester matrix through comonomer selection to achieve refractive index matching with polyamide domains. This parameter change ensures that even when domains are enlarged during stretching, light scattering is minimized, allowing high stretch ratios to be applied without significant haze increase, thereby improving container shape and fit.
3Reliability
If polyamide domain size is increased to improve barrier properties, then oxygen barrier performance is improved, but light scattering increases causing haze
Solution Approach 1:
The patent changes the refractive index parameter of the polyester matrix by incorporating specific comonomers. This parameter change reduces the refractive index difference between the polyester matrix and polyamide domains, thereby minimizing light scattering and haze even when polyamide domains are present at sizes that provide effective oxygen barrier properties.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The composition achieves a low haze and improved aesthetic appearance in stretched packaging while maintaining effective oxygen barrier properties, allowing for higher stretch ratios without visible light interference.
Implementation Method 1
a specific interfacial tension reducing agent, such as lithium sulfoisophthalate, is used to reduce the size of polyamide domains
Implementation Method 2
Orientation enlarges the size of MXD6 domains so that the size of enough domains are greater than the minimum wavelength of visible light (approximately 400 nm) resulting in increased light scattering
Data Source
AI summary
A polymer composition, stretched and unstretched articles and processes to make stretched and unstretched articles from that composition are set forth wherein the composition comprises a blend of a polyamide wherein the amino to carboxyl end group ratio of the polyamide polymer is less than 1.0 when the relative viscosity of the polyamide polymer is less than 2.0, and less than 0.30 when the relative viscosity is in the range of 2.0 to 2.3 and less than 0.20 when the relative viscosity is greater than 2.3, a crystallizable polyester and an interfacial tension reducing agent.