Polyamide-Polyester Blend Haze Reduction via Interfacial Mediator
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current polyester-polyamide blends used in packaging for oxygen-sensitive products like foods 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 material.
Innovation Solution
A polymer composition with a polyamide like MXD6, where the amino to carboxyl end group ratio is less than 0.10, combined with an interfacial tension reducing agent such as lithium sulfoisophthalate, is used to reduce the size of polyamide domains and improve dispersion in the polyester matrix, maintaining low haze and high barrier properties even after stretching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyamide is blended into polyester to improve oxygen barrier, then oxygen barrier property is improved, but haze increases when stretched
Solution Approach 1:
A compatibilizer is introduced as an intermediary substance between the polyamide and polyester phases. The compatibilizer has affinity for both polymers, reducing interfacial tension and stabilizing the dispersion. This prevents polyamide domain enlargement during stretching while maintaining the oxygen barrier benefit of the polyamide-polyester blend.
Solution Approach 2:
The invention changes the chemical parameters of the polymer system by controlling the amino to carboxyl end group ratio of the polyamide (less than 0.10) and adjusting the molecular weight and structure of the compatibilizer. These parameter changes optimize the dispersion stability and domain size control during the stretching process, preventing haze while preserving barrier properties.
2Strength
If stretch ratio is increased to improve packaging strength, then mechanical strength is improved, but haze increases due to domain enlargement
Solution Approach 1:
The compatibilizer acts as a mediator that decouples the relationship between stretching and domain enlargement. By stabilizing the polyamide-polyester interface, the compatibilizer allows the polymer matrix to be stretched for strength without causing significant domain growth in the dispersed polyamide phase, thus maintaining low haze.
Solution Approach 2:
The compatibilizer is incorporated into the polymer blend before stretching occurs. This preliminary stabilization of the dispersion prevents the harmful effect (haze) from manifesting during the stretching process, allowing high stretch ratios to be achieved without domain enlargement.
3Ease of manufacture
If monolayer construction is used to reduce cost, then manufacturing cost is reduced, but aesthetic properties deteriorate due to haze
Solution Approach 1:
The compatibilizer enables the use of a single-layer monolayer construction by stabilizing the dispersion of polyamide in polyester. This eliminates the need for multiple layers while maintaining aesthetic properties (low haze), thus reducing manufacturing cost without sacrificing appearance.
Solution Approach 2:
By optimizing the polyamide end group ratio and compatibilizer characteristics, the invention achieves low haze in a single-layer construction. This parameter optimization allows the monolayer to perform both the barrier function and aesthetic function that would otherwise require multiple layers.
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 oxygen barrier in stretched packaging, allowing for higher stretch ratios without increasing haze, thus enhancing the aesthetic and functional properties of the packaging material.
Implementation Method 1
an interfacial tension reducing agent which reduces the interfacial tension between the polyamide and the polyester
Implementation Method 2
the size of enough domains are greater than the minimum wavelength of visible light (approximately 400nm) resulting in increased light scattering
Data Source
Figure 1
Figure 2
Figure 3
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.