Multilayer Structure Preventing Blister Formation in High Humidity
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Solution Overview
Problem
Multilayer films containing EVOH resin with drying agents suffer from blister formation and loss of gas-barrier properties when exposed to high humidity, affecting their appearance and functionality.
Innovation Solution
A multilayer structure with a laminated unit of polyamide resin layers sandwiching a saponified ethylene-vinyl ester copolymer layer containing a hydrate-forming drying agent, where the polyamide resin layers have 20-60% amide bonds and the drying agent is present in a 50/50 to 1/99 weight ratio, is used to prevent blister formation and maintain gas-barrier properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a drying agent is added to the EVOH resin composition to maintain gas-barrier properties, then gas-barrier property is improved, but waterdrop formation occurs at the interface causing blistering and appearance degradation
Solution Approach 1:
The patent introduces an adhesive resin layer as an intermediary between the EVOH resin composition layer containing the drying agent and the polyolefin layer. This adhesive layer acts as a mediator that prevents direct contact between the drying agent and the polyolefin layer, thereby preventing waterdrop formation and blistering while maintaining the gas-barrier properties provided by the drying agent in the EVOH layer.
Solution Approach 2:
The patent segments the multilayer film structure into distinct functional layers: an EVOH resin composition layer containing the drying agent for gas-barrier properties, an adhesive resin layer to prevent waterdrop formation, and a polyolefin layer for hydrophobic protection. This segmentation allows each layer to perform its specific function without interfering with others, resolving the contradiction between maintaining gas-barrier properties and preventing appearance degradation.
2Object-affected harmful factors
If polyolefin layers are used as outer surface layers to provide hydrophobicity, then moisture permeation is reduced, but adhesiveness to EVOH resin layer is poor requiring additional adhesive layers
Solution Approach 1:
The patent combines the adhesive function with the polyolefin layer by using an adhesive resin that is based on polyolefin or a copolymer containing polyolefin as a main component. This merging of adhesive and hydrophobic functions into a single layer reduces the number of separate layers needed while maintaining both the moisture barrier and adhesion to the EVOH resin composition layer.
3Strength
If adhesive resin layer is added to improve bonding between polyolefin and EVOH resin, then adhesiveness is improved, but the multilayer structure becomes more complex
Solution Approach 1:
The adhesive resin layer is designed to perform multiple functions: it provides adhesion between the polyolefin layer and EVOH resin composition layer, prevents waterdrop formation by blocking the interface, and maintains the overall structural integrity. This multi-functionality reduces the need for additional separate layers, thereby limiting the increase in structural complexity while improving adhesiveness.
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 structure effectively suppresses waterdrop formation and maintains excellent appearance and gas-barrier properties even under high humidity conditions, making it suitable for wrapping films and food containers.
Implementation Method 1
the drying agent is capable of forming hydrate crystal by moisture absorption
Data Source
AI summary
An object of the present invention is to provide a multilayer structure securing excellent appearance even after being left in high humidity environment regardless that the multilayer structure comprises a resin composition layer containing a drying agent. The multilayer structure comprises a laminated unit (β/α/β) wherein polyamide resin layers (β) are integrally laminated on both faces of a resin composition layer (α) containing (A) saponified ethylene-vinyl ester copolymer and (B) drying agent.