Free-Radical Polymerization Primer Layer for Color Control

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Solution Overview

Problem

Free-radical polymerization methods using copper compounds often result in color formation, which is undesirable for aesthetic and functional reasons, and are prone to oxygen inhibition, leading to tacky surfaces in applications like acrylic structural adhesives and liquid optically clear adhesives.

Innovation Solution

Incorporating an organic peroxide and optional beta-diketone compound in a solid primer layer on a substrate to initiate free-radical polymerization of curable compositions containing a free-radically polymerizable compound, a quaternary ammonium halide, and a polyvalent metal compound, thereby improving shelf life and reducing the need for copper and halide content.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If copper compounds are used to initiate free-radical polymerization, then polymerization speed is improved, but color formation occurs which is undesirable for aesthetic and functional reasons

Engineering Contradiction:

Improvepolymerization speedVSAvoidcolor formation

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent extracts the harmful copper compound from the curable composition itself and relocates it to a separate primer layer applied to the substrate. This separation allows the curable composition to remain free of copper compounds during storage, preventing color formation, while still enabling copper-mediated polymerization when applied to the primed substrate.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The primer layer acts as an intermediary carrier that contains the copper compound and transfers it to the curable composition during application. The primer layer mediates between the need for copper-initiated polymerization and the need to avoid copper-induced color formation in the final cured product.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If copper compounds are included in curable compositions, then free-radical polymerization is effective, but shelf life is shortened due to spontaneous reactivity

Engineering Contradiction:

Improvepolymerization effectivenessVSAvoidshelf life

Core Design Contradiction:

ProductivityVSDuration of action of stationary object

Solution Approach 1:

The patent segments the copper compound from the curable composition into a separate primer layer. This segmentation prevents spontaneous interaction between copper compounds and the curable composition during storage, thereby extending shelf life, while maintaining polymerization effectiveness when the two components are brought into contact during application.

Inventive Principle:

Principle #1Segmentation

3Productivity

If halide salts are used in free-radical polymerization systems, then polymerization is activated, but corrosion of surfaces occurs due to halide content

Engineering Contradiction:

Improvepolymerization activationVSAvoidsurface corrosion

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent extracts halide salts from the curable composition and relocates them to the primer layer. This separation eliminates the source of halide-induced corrosion from the curable composition, protecting metal and other sensitive surfaces while maintaining polymerization activation through the primer layer's halide content.

Inventive Principle:

Principle #2Taking out (Extraction)

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

This approach enhances the shelf life of curable compositions, improves aesthetics by reducing color formation, and minimizes corrosion risks by reducing polyvalent metal ion content, while ensuring complete curing and maintaining adhesion.

Implementation Method 1

initiation of free-radical polymerization occurs, thereby at least partially curing the curable composition

Methodology Applied

Scientific EffectFree-radical polymerization:

Implementation Method 2

including an organic peroxide and optional beta-diketone compound in a solid primer layer on a substrate to which the curable composition is to be bonded. When the components of the curable composition contact the organic peroxide and optional beta-diketone in the solid primer layer initiation of free-radical polymerization occurs

Methodology Applied

Scientific EffectPeroxide decomposition:

Data Source

PatentEP3201238B1Free-radical polymerization methods and articles thereby

Publication Date: 2022.02.23 3M INNOVATIVE PROPERTIES CO

Figure 1

AI summary

A method of curing a curable composition includes contacting the free-radically curable composition with the solid primer layer thereby causing at least partial curing of the curable composition. The solid primer layer includes a binder material, optional beta-dicarbonyl compound, and an organic peroxide. The curable composition includes at least one free-radically polymerizable compound, a polyvalent metal compound, and a quaternary ammonium halide. The method can be used for adhesive bonding of substrates and preparation of various articles.