EVOH Resin Composition Stabilizing Melt Flow and Color
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current resin compositions containing ethylene-vinyl alcohol copolymer (EVOH) for melt molding lack sufficient long-term color stability and gas barrier properties, leading to issues like gel formation, hard spots, and poor appearance during extended processing.
Innovation Solution
A resin composition comprising EVOH with an ethylene unit content of 20-60 mol%, a divalent metal hydroxide, and a monovalent metal compound, along with a polyamide resin, which maintains a specific mass ratio and particle size distribution to enhance long-term melt molding performance and color stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If EVOH is used as a main component for packaging materials, then excellent oxygen shield ability is achieved, but long run property deteriorates over time with increase of gels and hard spots
Solution Approach 1:
A phosphorous compound is introduced as an intermediary substance to mediate between EVOH molecules. This phosphorous compound forms a protective layer or interaction network that prevents direct harmful interactions between EVOH chains, thereby suppressing gel and hard spot formation while preserving the inherent oxygen barrier properties of EVOH.
Solution Approach 2:
The chemical composition parameters of the resin system are changed by adding specific phosphorous compounds and metal salts. This parameter change modifies the molecular interactions and crosslinking behavior of EVOH during melt molding, suppressing the formation of gels and hard spots while maintaining excellent oxygen shield ability.
2Productivity
If EVOH is processed by melt molding for extended periods, then production efficiency is maintained, but appearance quality deteriorates with streak-like defects
Solution Approach 1:
The phosphorous compound acts as a mediator during melt molding processes, stabilizing the melt flow characteristics of EVOH over extended processing times. This intermediary substance prevents streak formation by ensuring uniform material flow and distribution, thereby maintaining appearance quality while enabling continuous high-productivity molding operations.
Solution Approach 2:
The phosphorous compound and metal salt are pre-added to the EVOH resin before processing. This preliminary action prepares the resin system in advance to resist degradation and appearance defects during extended melt molding, allowing continuous production without compromising quality.
3Duration of action of stationary object
If phosphorous compound and metal salt are added to improve long run property, then gel and hard spot formation is suppressed, but color stability during long-term melt molding becomes insufficient
Solution Approach 1:
A composite additive system is created by combining phosphorous compounds with specific metal salts in defined ratios. This composite approach synergistically enhances long run property through gel suppression while the metal salt component simultaneously provides color stability during long-term melt molding, resolving the trade-off between these two properties.
Solution Approach 2:
The compositional parameters of the additive system are optimized by adjusting the types and ratios of phosphorous compounds and metal salts. This parameter optimization achieves a balance where gel formation is suppressed and color stability is maintained simultaneously during extended processing operations.
4Reliability
If EVOH with high vinyl alcohol content is used to improve oxygen barrier property, then gas barrier ability increases, but melt molding processability deteriorates
Solution Approach 1:
The phosphorous compound serves as an intermediary that modifies the melt rheology of high vinyl alcohol content EVOH. This intermediary substance reduces intermolecular hydrogen bonding in the melt state, improving processability and flow characteristics while preserving the tight molecular packing that provides excellent gas barrier properties in the solid state.
Solution Approach 2:
The physical and chemical parameters of the EVOH system are modified through additive incorporation. The phosphorous compound and metal salt alter the melt viscosity and flow behavior parameters, enabling easier processing of high vinyl alcohol content EVOH while maintaining the dense crystalline structure necessary for superior gas barrier performance.
Data Source
AI summary
The present invention relates to a resin composition comprising an ethylene-vinyl alcohol copolymer (A) with an ethylene unit content of 20 mol % or more and 60 mol % or less, a divalent metal hydroxide (B) and a monovalent metal compound (C), wherein a content of the divalent metal hydroxide (B) is 5 ppm or more and 5000 ppm or less, and a mass ratio (C/B) of the amount of the monovalent metal compound (C) in terms of the monovalent metal atom to the amount of the divalent metal hydroxide (B) in terms of the divalent metal atom is 0.025 to 100. Thus, there is provided a resin composition containing an ethylene-vinyl alcohol copolymer having excellent long run property during melt molding and excellent color phase in long-term melt molding.