UV-Curable Ink Photodecomposition Reduction via Organic Acid

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing UV-curable ink and coating compositions using cleavage-type photoinitiators generate significant amounts of photodecomposition products like aldehydes and ketones during the curing process, which can migrate and contaminate packaged products, particularly in food packaging applications, where low migration of contaminants is crucial.

Innovation Solution

Incorporating organic acids such as phosphoric acid, sulphonic acid, or their derivatives into the UV-curable ink and coating compositions to reduce the amount of photodecomposition products produced by cleavage-type photoinitiators during the UV-curing process, thereby minimizing contamination risks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If cleavage type photoinitiators are used in UV-curable compositions, then the curing efficiency is improved, but the amount of photodecomposition products (aldehydes, ketones) generated increases causing contamination

Engineering Contradiction:

Improvecuring efficiencyVSAvoidphotodecomposition products

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The patent applies the principle of converting harm into benefit by using the photodecomposition products (aldehydes and ketones) generated by cleavage type photoinitiators not as contaminants but as in-situ photoacid generators. These decomposition products initiate cationic polymerization of cyclic monomers, transforming the harmful byproducts into useful initiators that drive the curing process and reduce residual monomers.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Ease of operation

If high amounts of monofunctional monomers are used to achieve low viscosity and good printability, then the ease of operation is improved, but the amount of residual uncured monomers increases causing migration and contamination

Engineering Contradiction:

ImproveprintabilityVSAvoidresidual monomers

Core Design Contradiction:

Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The patent applies parameter changes by incorporating cyclic monomers with ring strains of 20-30 kcal/mol (such as oxiranes, oxetanes, cyclobutanones, and cyclopropanecarboxylates) into the composition. These high-ring-strain monomers undergo rapid cationic polymerization that consumes residual monofunctional monomers and achieves complete curing, thereby reducing residual monomer content below detectable levels while maintaining good printability.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If dual cure compositions with both free radical and cationic photoinitiators are used, then the completeness of curing is improved, but the amount of monofunctional monomers must be high which increases migration risk

Engineering Contradiction:

Improvecuring completenessVSAvoidmigratable contaminants

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent merges the free radical and cationic curing mechanisms into a single integrated system. Cleavage type photoinitiators generate free radicals for initial polymerization while simultaneously producing photodecomposition products that act as photoacid generators for cationic polymerization. This unified dual-cure approach achieves complete curing without requiring high levels of monofunctional monomers, thereby eliminating migration issues.

Inventive Principle:

Principle #5Merging (Combining)

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 inclusion of organic acids significantly reduces the generation of aldehyde and ketone photodecomposition products by up to 90%, enhancing the safety and environmental friendliness of UV-curable ink and coating applications by minimizing contamination risks in sensitive printing and coating applications.

Implementation Method 1

cleavage type photoinitiators (also known as type I photoinitiators) are used, photodecomposition products are generated during UV-curing

Methodology Applied

Scientific EffectPhotodecomposition: Photodissociation

Implementation Method 2

the amount of certain photodecomposition products (e.g. aldehyde) produced by a cleavage type photoinitiator during UV-cure of the ink or coating compositions is reduced by incorporation of an acid into the compositions

Methodology Applied

Scientific EffectChemical reaction inhibition:

Data Source

PatentEP3774360B1UV-curable compositions comprising cleavage type photoinitiators

Publication Date: 2024.01.10 SUN CHEMICAL CORP

AI summary

The present invention is drawn to UV-curable ink and coating compositions comprising cleavage type photoinitiators and acids. The acids may be inorganic or organic acids, or acids generated by a photoacid generator during UV-cure. Incorporation of the acids into the UV-curable ink and coating compositions results in a reduction of migratable photodecomposition products that are produced by cleavage type photoinitiators during UV-cure. The ink and coating compositions are particularly useful for use in applications that require low migration of low molecular weight materials, such as, for example, food packaging.