Multilayer Film Recyclability via Polyamide Removal
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Solution Overview
Problem
Multilayer films with a polyamide layer face challenges in recycling due to poor compatibility with polyolefin, leading to uneven layer thickness and instability in film appearance and quality during the recycling process, and the removal of the polyamide layer results in issues with mechanical strength and recyclability.
Innovation Solution
A multilayer film configuration with a polyolefin layer, an adhesive resin layer, and an ethylene-vinyl alcohol copolymer resin composition layer, where the EVOH resin composition layer contains 60% by mass of EVOH resin, a hydrophobic plasticizer, and is free from Nylon 6, with specific ethylene-unit content and saponification degree, and a phosphoric acid compound, to enhance recyclability and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a polyamide layer is included in the laminated film to improve mechanical strength and oxygen barrier, then the film has excellent mechanical strength and gas barrier properties, but the film cannot be uniformly mixed with polyolefin during recycling and forms hard spots due to chemical reaction
Solution Approach 1:
The patent removes the polyamide layer from the laminated film structure, retaining only the polyolefin and EVOH layers. This extraction eliminates the incompatibility issue between polyamide and polyolefin during recycling, preventing hard spot formation while maintaining the necessary mechanical strength and barrier properties through the optimized remaining layer structure.
Solution Approach 2:
The patent creates a composite laminated film structure consisting of polyolefin and EVOH layers without polyamide. This composite structure achieves both recyclability and functional performance by carefully selecting compatible materials that can be uniformly mixed during recycling while maintaining mechanical strength and oxygen barrier properties.
2Manufacturing precision
If the thickness of the EVOH resin composition layer is reduced to improve appearance, then the film appearance deteriorates less, but the resin pressure of the extruder becomes unstable
Solution Approach 1:
The patent optimizes the thickness ratio of the EVOH resin composition layer to within a specific range (5-20% of total film thickness) and controls the ethylene-unit content (20-60 mol%) and saponification degree (90-100 mol%). These parameter changes balance the competing requirements: sufficient EVOH layer thickness for appearance quality while maintaining thin enough thickness for stable resin pressure during extrusion.
3Manufacturing precision
If an additive is added to solve the film appearance problem, then the film appearance improves, but the resin pressure of the extruder becomes unstable depending on the type and amount of additive
Solution Approach 1:
The patent eliminates the need for additional additives by optimizing the inherent properties of the EVOH resin composition itself. By controlling the ethylene-unit content and saponification degree within specific ranges, the film achieves good appearance quality without requiring external additives that would destabilize resin pressure, thus avoiding the trade-off between appearance improvement and pressure stability.
Data Source
AI summary
The present disclosure provides a multilayer film having a polyolefin layer (A), an adhesive resin layer (B), and an ethylene-vinyl alcohol copolymer resin composition layer (C).