Amorphous Polyamide Barrier Layer Prevents White Opacity
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Solution Overview
Problem
Synthetic resin containers, such as PET bottles, exhibit white opacity in non-stretched parts due to crystallization of the gas barrier layer, particularly when stored for long periods, affecting their appearance and barrier properties.
Innovation Solution
A synthetic resin container with a barrier layer composed of amorphous polyamides having meta-xylene isophthalamide and hexamethylene isophthalamide structures, with a peak crystallization temperature between 150 °C and 170 °C, is used to prevent white opacity, maintaining high barrier properties over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gas barrier layer is laminated on PET base layers to prevent gas permeation, then barrier properties are improved, but white opacity is generated in non-stretched parts during long-term storage
Solution Approach 1:
The patent changes the crystallization temperature parameter of the gas barrier layer from below 150°C to 170°C or higher by selecting specific polyamide materials (PA6, PA66, PA11, PA12) and adjusting their composition ratios. This parameter change prevents crystallization-induced white opacity in non-stretched parts during long-term storage while maintaining the gas barrier function.
Solution Approach 2:
The patent uses composite material structure with base layers made of PET and a gas barrier layer made of specific polyamide materials laminated thereon. The composite structure combines the mechanical properties of PET with the high barrier properties of polyamide, while the specific polyamide selection prevents white opacity formation.
2Reliability
If polyamide MXD6 is used as the gas barrier layer material, then barrier properties are improved, but crystallization occurs at lower temperatures causing white opacity
Solution Approach 1:
The patent changes the crystallization temperature parameter by selecting polyamide materials with higher crystallization temperatures (PA6, PA66, PA11, PA12) instead of polyamide MXD6. These materials have crystallization temperatures of 170°C or higher, preventing crystallization-induced white opacity during long-term storage at ambient temperatures.
Solution Approach 2:
The patent replaces polyamide MXD6 with more common and cost-effective polyamide materials (PA6, PA66, PA11, PA12) that achieve the same or better performance. These materials are widely available, easier to process, and provide superior long-term storage stability without white opacity formation.
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 solution effectively suppresses white opacity in non-stretched parts, ensuring the container maintains good appearance and gas barrier properties even after long-term storage, with the amorphous polyamide content rate between 15 and 25 weight percentage.
Implementation Method 1
the white opacity is caused by crystallization of MXD6. It is considered that the crystallization of MXD6 is enhanced by decrease in glass transition temperature and crystallization temperature caused by increase in moisture content of MXD6
Implementation Method 2
the generation of the white opacity in the non-stretched part may be suppressed by increasing crystallization temperature of at least the gas barrier layer
Data Source
Figure 1
AI summary
There is provided a synthetic resin container product with high barrier properties, in which white opacity is not generated in the non-stretched part in spite of a long-term storage of the product. A PET bottle comprises base layers 11 composed of PET and a barrier layer 12 with lower gas permeability than that of the base layers 11. The barrier layer 12 contains an amorphous polyamide having meta-xylene isophthalamide structure and hexamethylene isophthalamide structure. As the amorphous polyamide, a copolyamide of a copolymer of meta-xylene diamine and isophthalic acid (MXDI) and a copolymer of hexamethylene diamine and isophthalic acid (6I) is used and the content rate of the amorphous polyamide in the barrier layer 12 is 15 weight percentage or more and 25 weight percentage or less.