EVOH Resin Composition Impact Resistance and Heat Stability
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Solution Overview
Problem
EVOH resin compositions used in multilayer structures face challenges with impact resistance and heat stability due to their high crystallinity and susceptibility to oxidation reactions during melting, leading to issues like cracking, pinholes, coloration, and reduced productivity.
Innovation Solution
Incorporating a long Periodic Table 4th-period d-block metal compound and a specific small amount of an iron compound into the EVOH resin composition, with the iron compound present in amounts of 0.01 to 5 ppm on a metal basis, to enhance impact resistance and heat stability, while maintaining gas barrier properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If EVOH resin is used to achieve excellent gas barrier properties, then oxygen barrier property is improved, but impact resistance deteriorates due to higher crystallinity making the resin brittle
Solution Approach 1:
The patent applies parameter changes by carefully controlling the vinyl alcohol content within 30-40 mol% and saponification degree within 85-95 mol%, and by controlling crystallinity within 30-60%. These parameter adjustments optimize the balance between gas barrier properties and impact resistance, preventing excessive crystallinity that would cause brittleness while maintaining sufficient barrier performance.
Solution Approach 2:
The patent employs composite materials by blending EVOH resin with specific polyolefin resins (ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, or polyethylene) in controlled ratios. This composite approach combines the excellent gas barrier properties of EVOH with the flexibility and impact resistance of polyolefin resins, resolving the contradiction between barrier performance and mechanical toughness.
2Ease of manufacture
If EVOH resin is melted at higher temperature to improve formability, then processing is improved, but oxidation reaction and crosslinking reaction occur causing coloration and gelation
Solution Approach 1:
The patent uses antioxidants as intermediary substances to prevent oxidation reactions during melting and processing. These antioxidants act as mediators between the EVOH resin and oxygen, suppressing harmful oxidation and crosslinking reactions that would cause coloration and gelation, thereby enabling higher temperature processing while maintaining heat stability.
Solution Approach 2:
The patent controls processing parameters by limiting the melting temperature to below the decomposition point and controlling the residence time in the melt state. Additionally, the patent specifies adding antioxidants in controlled amounts (0.01-5 ppm iron compound equivalent) to suppress oxidation reactions during processing, allowing improved formability without sacrificing heat stability.
3Reliability
If EVOH resin composition is optimized for gas barrier properties with high EVOH content, then oxygen barrier is improved, but productivity deteriorates due to susceptibility to oxidation during melting
Solution Approach 1:
The patent introduces antioxidants as intermediary substances that protect the high EVOH content composition from oxidation during melting and processing. This allows the composition to maintain high EVOH content (30-40 mol% vinyl alcohol) for excellent gas barrier properties while the antioxidants prevent degradation that would reduce productivity, enabling stable continuous processing.
Solution Approach 2:
The patent optimizes processing parameters by controlling melting temperature and residence time, and by specifying antioxidant addition levels (0.01-5 ppm iron compound equivalent). These parameter changes enable high EVOH content compositions to be processed efficiently without oxidation-related productivity losses, resolving the contradiction between barrier performance and manufacturing efficiency.
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 resulting EVOH resin composition exhibits improved film impact resistance and heat stability, suppressing color tone deterioration and coloration, making it suitable for various packaging materials.
Implementation Method 1
The EVOH resin contains relatively active hydroxyl groups in its molecules and, therefore, is liable to experience oxidation reaction and crosslinking reaction when being melted at a higher temperature even in a generally oxygen-free environment within an extruder.
Implementation Method 2
The EVOH resin has crystalline portions formed due to firm hydrogen bonds between hydroxyl groups richly present in its molecular chains, and these crystalline portions prevent intrusion of oxygen from the outside.
Data Source
AI summary
An ethylene-vinyl alcohol copolymer composition contains: (A) an ethylene-vinyl alcohol copolymer; (B) a long Periodic Table 4th-period d-block metal compound; and (C) an iron compound; wherein the iron compound (C) is present in an amount of 0.01 to 5 ppm on a metal basis based on the weight of the ethylene-vinyl alcohol copolymer composition. The ethylene-vinyl alcohol copolymer composition exhibits improved impact resistance and heat stability (color tone deterioration-suppressing effect and coloration-suppressing effect).