Multilayer Container Yellowing Suppression via Polyamide Dye
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Solution Overview
Problem
Polyester resin containers with polyamide layers tend to yellow due to heat history, especially during recycling, which reduces the product value and requires measures to suppress yellowing.
Innovation Solution
A multilayer container with a specific L* value of 87.5 or greater, comprising a polyester layer and a polyamide layer containing a polyamide resin and a specific amount of a yellowing inhibitor dye, which is a blue dye such as anthraquinone-based dyes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyamide resin layer is added to improve gas barrier properties, then gas barrier performance is improved, but yellowing due to heat history increases
Solution Approach 1:
A polyester resin layer is introduced as an intermediary barrier between the polyamide resin layer and the external environment. This polyester layer acts as a protective mediator that prevents direct contact between oxygen/moisture and the polyamide, thereby suppressing yellowing while maintaining the gas barrier functionality of the polyamide layer.
Solution Approach 2:
The invention uses a composite multilayer structure combining polyester resin and polyamide resin layers. This composite material approach allows the system to simultaneously achieve the gas barrier properties of polyamide and the yellowing resistance of polyester, resolving the contradiction between these two properties.
2Object-generated harmful factors
If a blue pigment is added to suppress yellowing, then yellowing is suppressed, but the container loses colorlessness and design freedom
Solution Approach 1:
The invention converts the naturally yellowing tendency of polyamide resin into a benefit by using the yellowing process itself as an indicator to optimize the multilayer structure. The polyester layer protects the polyamide, and any remaining yellowing is compensated by the overall multilayer design rather than using blue pigment, thus maintaining colorlessness and design freedom.
3Reliability
If the polyamide resin content is increased to improve gas barrier properties, then gas barrier performance is improved, but the yellowing tendency increases
Solution Approach 1:
The invention applies local quality by creating a multilayer structure where different resin types are distributed in specific locations. The polyester layer is positioned to provide yellowing resistance where needed, while the polyamide layer is positioned to provide gas barrier properties, allowing each material to function optimally in its designated zone without the downsides of the other.
Data Source
AI summary
Provided is a multilayer container having a polyester layer containing a polyester resin (X), and a polyamide layer containing a polyamide resin (Y) and a yellowing inhibitor (A). The content of the polyamide resin (Y) is from 0.05 to 7.0 mass % relative to the total amount of all polyamide layers and all polyester layers. The yellowing inhibitor (A) is a dye. The content of the yellowing inhibitor (A) is from 400 to 800 ppm relative to the polyamide layer. An L* of the multilayer container is 87.5 or greater.