EVOH Polyester Resin Composition Thermal Degradation

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Solution Overview

Problem

Resin compositions containing ethylene-vinyl alcohol copolymer (EVOH) and thermoplastic polyester or polyalkylene ether unit-containing polymers tend to undergo thermal degradation and coloration during melt kneading and melt forming, leading to reduced flexibility and performance in packaging applications.

Innovation Solution

Incorporating a specific small amount of sorbic acid ester into the resin composition, ranging from 0.00001 to 10 ppm, along with EVOH and a polyester resin, to suppress thermal degradation and coloration, while maintaining heat stability and flexibility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If EVOH is blended with soft resin to improve flexibility, then flexibility is improved, but thermal degradation and coloration occur during melt processing

Engineering Contradiction:

ImproveflexibilityVSAvoidthermal degradation and coloration

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a specific additive system comprising phosphoric acid (0.01-5 wt%) and a carboxylic acid (0.01-5 wt%) as intermediary substances that mediate between the EVOH and polyester resin during melt processing. This additive system suppresses thermal degradation and coloration reactions while allowing the flexibility benefits of polyester resin blending to be realized. The additives act as heat stabilizers and color stabilizers during the melt kneading and forming processes.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent optimizes specific processing parameters including the weight ratio of EVOH to polyester resin (95:5 to 50:50), the precise amounts of phosphoric acid and carboxylic acid additives, and melt processing temperatures. By controlling these parameters within specific ranges, the patent achieves both flexibility and suppression of thermal degradation during melt processing.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If EVOH composition is optimized for gas barrier properties, then oxygen barrier property is improved, but brittleness increases due to high crystallinity

Engineering Contradiction:

Improveoxygen barrier propertyVSAvoidbrittleness

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent creates a composite material system combining EVOH (providing oxygen barrier properties) with polyester resin (providing flexibility). The specific composition range (EVOH 50-95 wt%, polyester resin 5-50 wt%) creates a composite that balances the high crystallinity-induced brittleness of pure EVOH with the flexibility of polyester resin, while maintaining excellent oxygen barrier properties through the EVOH component.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentEP3715414B1Resin composition, melt-forming material, multilayer structure, and liquid packaging material

Publication Date: 2023.04.26 MITSUBISHI CHEM CORP

AI summary

A resin composition contains: (A) an ethylene-vinyl alcohol copolymer, (B) a polyester resin, and (C) a sorbic acid ester; wherein the sorbic acid ester (C) is present in an amount of 0.00001 to 10 ppm based on the weight of the resin composition. The resin composition exhibits excellent thermal degradation resistance reduced susceptibility to coloration.