Multilayer Polyester Container Composition for Recycled Clarity

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Solution Overview

Problem

Existing multilayer polyester containers with polyamide layers suffer from yellowing during recycling, leading to reduced commodity value and transparency issues in recycled polyester.

Innovation Solution

A multilayer container design incorporating a polyester layer with phenolic and phosphorus-based antioxidants, along with an optional aldehyde catcher, to suppress yellowing and enhance transparency in recycled polyester.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a polyamide layer is added to improve gas barrier properties, then gas barrier performance is improved, but yellowing occurs during recycling

Engineering Contradiction:

Improvegas barrier propertiesVSAvoidyellowing

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A polyester layer containing antioxidant (A) and phosphorus-based antioxidant (B) is introduced as an intermediary between the polyamide layer and the external environment. This intermediary layer protects the polyamide layer from thermal and oxidative degradation during recycling, preventing yellowing while maintaining the gas barrier function of the polyamide layer.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention creates a composite multilayer structure combining polyester and polyamide materials with specific antioxidant additives. The polyester layer contains both phenolic antioxidant (A) and phosphorus-based antioxidant (B) in optimized ratios to provide comprehensive protection against yellowing during recycling while maintaining compatibility with the polyamide layer.

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If antioxidant is added to suppress yellowing, then yellowing is reduced, but transparency of recycled polyester deteriorates

Engineering Contradiction:

ImproveyellowingVSAvoidtransparency

Core Design Contradiction:

Object-affected harmful factorsVSIllumination intensity

Solution Approach 1:

The invention optimizes the concentration parameters of antioxidants in the polyester layer, maintaining the total content of antioxidants (A) and (B) within 0.01 to 0.10 mass%. This precise parameter control ensures sufficient yellowing suppression while preventing excessive antioxidant accumulation that would cause haze and reduce transparency in the recycled polyester.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The antioxidant protection is localized specifically to the polyester layer through melt-mixing during container formation, rather than being uniformly distributed throughout the entire multilayer structure. This local concentration of antioxidants in the polyester layer provides effective yellowing suppression while minimizing their presence in the final recycled polyester product, thereby maintaining transparency.

Inventive Principle:

Principle #3Local quality

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 multilayer container effectively prevents yellowing and maintains transparency in recycled polyester, improving its colorlessness and recyclability.

Implementation Method 1

yellowing due to thermal history is prone to proceed in a multilayer polyester container with a polyamide layer... addition of an antioxidant to the container... phenolic antioxidant and a phosphorus-based antioxidant can solve the above-mentioned problems

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

a phenolic antioxidant and a phosphorus-based antioxidant... total content of the phenolic antioxidant (A), the phosphorus-based antioxidant (B) and the aldehyde catcher (C) in the polyester layer is from 0.05 to 0.22 mass%

Methodology Applied

Scientific EffectFree radical scavenging: Absorption (physical)

Data Source

PatentEP4685063A1Multilayered container and method for producing recycled polyester

Publication Date: 2026.01.28 MITSUBISHI GAS CHEM CO INC

AI summary

A multilayer container includes: a polyester layer containing a polyester resin (X), a phenolic antioxidant (A), and a phosphorus-based antioxidant (B); or a polyester layer containing a polyester resin (X), a phenolic antioxidant (A), a phosphorus-based antioxidant (B), and an aldehyde catcher (C); and a polyamide layer containing a polyamide resin (Y). A total content of the phenolic antioxidant (A), the phosphorus-based antioxidant (B), and the aldehyde catcher (C) in the polyester layer is from 0.05 to 0.22 mass%, and the phosphorus-based antioxidant (B) is a compound having a pentaerythritol skeleton and an aromatic ring.