Waterborne Coating Curing via Sequential UV and Electron Beam

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Solution Overview

Problem

Conventional coating curing methods using UV radiation face limitations in scratch resistance, hardness, and pigmentation, with UV curing requiring hazardous isocyanates and being unsuitable for thicker coatings, while EB curing is costly and requires inert conditions.

Innovation Solution

A method involving a waterborne coating with a photoinitiator and pigment concentration of 2.0% to 68.7%, cured first with UV radiation and then with EB, which reduces the need for nitrogen during EB curing and enhances scratch resistance, hardness, and hiding power.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If UV radiation curing is used, then curing speed is improved, but scratch resistance and hardness are insufficient

Engineering Contradiction:

Improvecuring speedVSAvoidscratch resistance

Core Design Contradiction:

ProductivityVSStrength

Solution Approach 1:

The patent combines UV radiation curing and electron beam (EB) curing into a sequential two-stage process. UV curing is applied first to achieve rapid initial curing, followed by EB curing to enhance crosslinking density and mechanical properties. This merging of two curing methods resolves the contradiction by leveraging the speed advantage of UV curing while obtaining the superior hardness and scratch resistance from EB curing.

Inventive Principle:

Principle #5Merging (Combining)

2Strength

If isocyanate hardener is added to improve adhesion, then adhesion is improved, but hazardous materials are introduced

Engineering Contradiction:

ImproveadhesionVSAvoidhazardous materials

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent extracts and eliminates isocyanate hardener from the coating formulation by utilizing electron beam curing as an alternative crosslinking mechanism. EB curing generates radicals that enable crosslinking without requiring isocyanates, thereby maintaining adhesion performance while removing the hazardous material from the system.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent substitutes the chemical crosslinking mechanism (isocyanate-based) with a physical radiation-based mechanism (electron beam). This replacement eliminates the need for hazardous chemical hardeners while achieving the same or superior crosslinking and adhesion results through radiation-induced radical formation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Manufacturing precision

If UV curing is used for transparent coatings, then curing effectiveness is improved, but penetration through thicker coatings is limited

Engineering Contradiction:

Improvecuring effectivenessVSAvoidcoating thickness

Core Design Contradiction:

Manufacturing precisionVSLength of stationary object

Solution Approach 1:

The patent transitions from surface-limited UV curing to volumetric EB curing by utilizing electron beam penetration capabilities. Electron beams can penetrate deeper into the coating substrate, enabling uniform crosslinking throughout the entire coating thickness rather than being restricted to the surface layer, thus resolving the depth limitation of UV curing.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

4Volume of moving object

If EB curing is used to eliminate photoinitiators, then coating penetration is improved, but nitrogen inertization costs increase

Engineering Contradiction:

Improvecoating penetrationVSAvoidnitrogen consumption

Core Design Contradiction:

Volume of moving objectVSQuantity of substance

Solution Approach 1:

The patent applies partial EB curing instead of complete EB curing, using it only as a finishing step after UV curing. This partial application of EB curing provides sufficient additional crosslinking to achieve the desired penetration and mechanical properties without requiring prolonged EB exposure, thereby reducing nitrogen consumption and operational costs while maintaining the penetration advantages.

Inventive Principle:

Principle #16Partial or excessive action

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 method improves scratch resistance, hardness, adhesion, and hiding power while reducing costs by minimizing nitrogen consumption and equipment needs, and provides better performance properties compared to traditional methods.

Implementation Method 1

curing the waterborne coating using UV radiation

Methodology Applied

Scientific EffectPhotopolymerisation: Photopolymerisation

Implementation Method 2

curing the waterborne coating using EB radiation

Methodology Applied

Scientific EffectElectron beam curing: Electron Beam

Data Source

PatentUS20240207892A1Method of curing a waterborne coating

Publication Date: 2024.06.27 SWIMC LLC

AI summary

Provided herein is a method of curing a waterborne coating comprising: (1) preparing a waterborne coating comprising: (a) at least one photoinitiator and (b) at least one pigment, wherein the pigment volume concentration of the waterborne coating is 2.0% to 68.7%; (2) curing the waterborne coating using UV radiation; and (3) curing the waterborne coating using EB. The method may further comprise the step of drying the waterborne coating prior to curing the waterborne coating using UV radiation. Also described is a waterborne coating prepared from the method described herein and an article to which the waterborne coating is applied.