Multilayer Structure Adhesive Resin Composition Boronic Acid EVOH
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Solution Overview
Problem
The existing multilayer structures of polypropylene and ethylene-vinyl alcohol copolymers suffer from poor adhesion strength, which deteriorates during secondary processing such as stretching and thermoforming, and are prone to coloration issues due to the use of unsaturated carboxylic acid-modified polypropylene adhesives.
Innovation Solution
A multilayer structure comprising a polypropylene layer and an ethylene-vinyl alcohol copolymer layer laminated via an adhesive resin composition containing a thermoplastic resin with boronic acid or boron-containing groups and an ethylene-α-olefin copolymer, which maintains adhesion strength even after secondary processing and prevents coloration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polypropylene modified with maleic anhydride is used as adhesive, then adhesion between polypropylene and EVOH is improved, but the adhesive layer is easily colored during heat treatment
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive resin from maleic anhydride-modified polypropylene to a specific formulation containing polypropylene, polyethylene, and epoxidized natural rubber in controlled proportions. This parameter change eliminates the coloration issue while maintaining adhesion strength
Solution Approach 2:
The patent creates a composite adhesive resin composition by combining multiple materials (polypropylene, polyethylene, and epoxidized natural rubber) with specific proportions. This composite approach achieves both good adhesion to EVOH and resistance to heat-induced coloration
2Strength
If adhesive layer is added between polypropylene and EVOH, then interlayer adhesion is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent applies local quality by providing adhesive properties only at the interface between polypropylene and EVOH layers, while the bulk materials maintain their original properties. The adhesive layer is localized precisely where needed for bonding
3Ease of manufacture
If polypropylene and EVOH are laminated directly, then manufacturing process is simplified, but adhesion between layers is poor
Solution Approach 1:
The patent introduces an adhesive resin composition as an intermediary layer between polypropylene and EVOH. This intermediary material is specifically formulated to bond with both materials, solving the adhesion problem while maintaining manufacturing simplicity through coextrusion
4Strength
If existing adhesive compositions are used, then adhesion is initially good, but adhesion strength deteriorates during secondary processing such as stretching and thermoforming
Solution Approach 1:
The patent provides beforehand cushioning by formulating the adhesive resin composition with epoxidized natural rubber, which maintains flexibility and adhesion during subsequent processing. The composition is pre-engineered to withstand stretching and thermoforming without losing bond strength
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 proposed solution achieves strong interlayer adhesion and maintains mechanical properties and barrier properties in shaped articles, such as films and thermoformed containers, while preventing coloration and adhesion loss during processing.
Implementation Method 1
resins containing functional groups of at least one kind selected from the group consisting of a boronic acid group and boron-containing groups each capable of being converted into a boronic acid group in the presence of water have a very high reactivity with EVOH
Implementation Method 2
such a resin modified with an unsaturated carboxylic acid or anhydride thereof is easily colored due to the heat during the melt-molding
Data Source
AI summary
A multilayer structure having a layer of a polypropylene (A) and a layer of an ethylene-vinyl alcohol copolymer (B) laminated to each other via a layer of an adhesive resin composition (C), wherein the adhesive resin composition (C) contains a thermoplastic resin (c1), having functional groups of at least one kind selected from the group consisting of a boronic acid group and boron-containing groups capable of being converted into a boronic acid group in the presence of water, and an ethylene-α-olefin copolymer (c2), having a density of 0.925 g/cm3 or less and not having the functional groups. Consequently, a multilayer structure can be provided that has a layer of a polypropylene and a layer of an EVOH and has good interlayer adhesion strength.