Multilayer EVOH Film for Agricultural Storage Bags
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Solution Overview
Problem
Conventional storage bags for agricultural products lack sufficient oxygen barrier properties and mechanical strength, particularly in applications like silobags, where high gas barrier properties and bubble stability are crucial for long-term preservation and handling of grain.
Innovation Solution
A multilayer article comprising an EVOH resin composition with a blend of ethylene-vinyl alcohol copolymer, unmodified ethylene-α-olefin copolymer, and acid-modified ethylene-α-olefin copolymer, with specific mass ratios and a core-layer structure, providing enhanced oxygen barrier, tear strength, and bubble stability during blown film extrusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyethylene resin is used for storage bags, then mechanical strength is improved, but oxygen barrier properties deteriorate
Solution Approach 1:
The patent uses a multilayer composite structure where the EVOH layer provides oxygen barrier properties and the polyethylene layer provides mechanical strength. This composite approach allows each layer to contribute its superior properties, resolving the contradiction between oxygen barrier performance and mechanical strength that cannot be achieved with a single material.
2Reliability
If polyethylene film thickness is increased to improve gas barrier properties, then oxygen barrier properties are improved, but bubble stability during extrusion deteriorates
Solution Approach 1:
Instead of increasing polyethylene thickness, the patent introduces an EVOH layer specifically for gas barrier properties. The EVOH layer has superior oxygen barrier properties at much thinner dimensions, allowing the polyethylene layers to maintain their original thickness and thus preserve bubble stability during extrusion.
3Reliability
If polyamide-based resins are used instead of polyethylene, then gas barrier properties are improved, but long-term preservation effect and mold inhibition deteriorate
Solution Approach 1:
The patent replaces polyamide with a multilayer composite containing EVOH. The EVOH layer provides superior gas barrier properties (8000 times better than polyethylene and 50 times better than polyamide), while the polyethylene layers maintain the structural integrity and long-term preservation capabilities including mold inhibition that polyamide lacks.
4Reliability
If EVOH is used for storage bags, then oxygen barrier properties are improved, but bubble stability during extrusion and tear strength deteriorate
Solution Approach 1:
The patent creates a multilayer composite where the EVOH layer (providing oxygen barrier) is sandwiched between polyethylene layers (providing mechanical strength and tear resistance). The adhesive layers ensure strong bonding between layers. This composite structure allows the thin EVOH layer to provide superior oxygen barrier properties without compromising the overall tear strength of the storage bag.
5Reliability
If conventional EVOH is used, then oxygen barrier properties are improved, but bubble stability during blown film manufacturing deteriorates
Solution Approach 1:
The patent uses a multilayer composite structure where the conventional EVOH layer is combined with polyethylene layers. The polyethylene layers provide bubble stability during blown film manufacturing, allowing the EVOH layer to maintain its superior oxygen barrier properties without suffering from the bubble stability issues that plague conventional EVOH processing.
Data Source
AI summary
A multilayer article having at least one layer of an ethylene vinyl alcohol (EVOH) resin composition comprising of an ethylene-vinyl alcohol copolymer, an unmodified ethylene-α-olefin copolymer and acid modified ethylene-α-olefin copolymer as described below, which is suitable for use in making (or as) a storage bag for agricultural products, food, drink, pharmaceutical, cosmetic, industrial chemical, detergent products.