Functionalized EVA Crosslinked Layer Adhesion

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Solution Overview

Problem

Polyester films face challenges in achieving good adhesion with ethylene vinyl acetate (EVA) copolymers due to lack of adhesion with polyester substrates, and the use of polyvinylidene chloride (PVDC) as a primer is limited by regulatory concerns and potential shortages.

Innovation Solution

A method is developed to create a composite film with a biaxially oriented polyethylene terephthalate substrate and a crosslinked layer formed by reacting functionalized ethylene vinyl acetate copolymers with organic crosslinkers like melamine, which enhances adhesion strength between the substrate and the crosslinked layer, achieving adhesion strengths of at least 177g/cm.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If PVDC is used as a primer layer to enhance adhesion of EVA copolymers on polyester, then adhesion strength is improved, but regulatory restrictions and material shortages occur

Engineering Contradiction:
Improveadhesion strengthVSAvoidmaterial availability
Core Design Contradiction:
StrengthVSReliability

Solution Approach 1:

The patent replaces the problematic PVDC primer with a functionalized EVA copolymer crosslinked layer that achieves comparable adhesion strength. The functionalized EVA copolymer contains multiple COOH groups per molecule that react with organic crosslinkers (melamine, isocyanates, carbodiimides, etc.) to form a durable crosslinked network providing strong adhesion to polyester substrates without the regulatory and availability issues of PVDC.

Inventive Principle:
Principle #27Cheap short-living objects (Disposable)

2Strength

If PVDC is used as a primer layer to enhance adhesion of EVA copolymers on polyester, then adhesion strength is improved, but regulatory restrictions occur

Engineering Contradiction:
Improveadhesion strengthVSAvoidregulatory restrictions
Core Design Contradiction:
StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the problematic PVDC primer with a functionalized EVA copolymer crosslinked layer that achieves comparable adhesion strength. The functionalized EVA copolymer contains multiple COOH groups per molecule that react with organic crosslinkers (melamine, isocyanates, carbodiimides, etc.) to form a durable crosslinked network providing strong adhesion to polyester substrates without the regulatory and availability issues of PVDC.

Inventive Principle:
Principle #27Cheap short-living objects (Disposable)

3Strength

If a crosslinked layer is formed by reacting functionalized EVA copolymer with organic crosslinker, then adhesion strength is improved, but process complexity increases

Engineering Contradiction:
Improveadhesion strengthVSAvoidprocess complexity
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The patent employs a functionalized EVA copolymer that already contains multiple COOH groups per molecule incorporated during polymer synthesis. This preliminary functionalization eliminates the need for separate grafting or modification steps, allowing direct crosslinking with organic crosslinkers to form the adhesion-enhancing layer on polyester substrates.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent utilizes chemical crosslinking reactions between the COOH groups of functionalized EVA copolymer and organic crosslinkers (melamine, isocyanates, carbodiimides, etc.) to transform the polymer structure from linear to crosslinked network. This parameter change in molecular architecture dramatically improves adhesion strength while maintaining processability through solution coating methods.

Inventive Principle:
Principle #35Parameter changes

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 method provides a robust adhesion strength of at least 177g/cm between the polyester substrate and the crosslinked layer, enabling effective heat sealing and bonding with various materials, including non-heat sealable polyesters, while avoiding the limitations of PVDC.

Implementation Method 1

a crosslinked layer on a surface thereof, wherein the crosslinked layer comprises a reaction product of a) a functionalized ethylene vinyl acetate copolymer comprising multiple COOH groups per molecule; and b) an organic crosslinker comprising multiple reactive groups per molecule, wherein the organic crosslinker is a melamine, said reactive groups being reactive with the COOH groups

Methodology Applied
Scientific EffectChemical Bonding: Chemical Bonding

Data Source

PatentEP3186304B1Film coating composition and method
Publication Date: 2021.01.27 MYLAR SPECIALTY FILMS U S LLP

AI summary

A composite film includes a polyester film substrate layer and a crosslinked layer on a surface thereof, wherein the crosslinked layer includes a reaction product of a) a functionalized ethylene vinyl acetate copolymer including multiple COOH groups or multiple alcoholic OH groups per molecule; and b) an organic crosslinker including multiple reactive groups per molecule, the reactive groups being reactive with the COOH or alcoholic OH groups; wherein the adhesion strength between the substrate layer and the crosslinked layer is at least 177g/cm (450g/inch). A method of joining the composite film, optionally further including a heat-sealable polymer layer on the crosslinked layer, to a container or a self-supporting film, includes contacting the crosslinked layer or the heat-sealable polymer layer with the container or the self- supporting film or under heat sealing conditions.