Low Migration UV-Curable Inkjet Inks for Food Packaging

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Solution Overview

Problem

Existing UV-curable inkjet fluids struggle to achieve low viscosity and low migration potential when cured in ambient air, failing to meet regulatory requirements for food packaging applications, particularly due to high levels of unreacted monomers and photoinitiators leading to contamination issues.

Innovation Solution

The use of low molecular weight, non-polymeric, difunctional or trifunctional photoinitiators with molecular weights below 500 amu, comprising at least 80% of the total photoinitiator content, in combination with a blend of difunctional monomers exceeding 50% of the polymerizable components, to formulate UV-curable inkjet compositions that minimize migratable species below regulatory limits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If polymeric photoinitiators are used to reduce migration potential, then the molecular weight increases which reduces migration, but the viscosity increases making the ink incompatible with newer printheads

Engineering Contradiction:

Improvemigration potentialVSAvoidviscosity

Core Design Contradiction:

Object-affected harmful factorsVSWeight of moving object

Solution Approach 1:

The patent changes the molecular weight parameter of photoinitiators from high (polymeric) to low (below 500 amu) while compensating with functional group optimization (difunctional or trifunctional) to maintain low migration potential without increasing viscosity, making the ink compatible with newer printheads

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite photoinitiator system combining low molecular weight photoinitiators with specific monomer blends (difunctional and trifunctional monomers) to achieve both low viscosity and low migration potential simultaneously

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If conventional UV-curable inkjet fluids are used, then pigmentation can be achieved, but the level of migratables exceeds regulatory limits for food packaging

Engineering Contradiction:

Improvepigmentation levelVSAvoidmigratable species

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The patent changes the chemical composition parameters by selecting specific low molecular weight photoinitiators and monomer types that produce minimal migratable species upon curing, while maintaining adequate pigmentation levels for food packaging applications

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses low molecular weight photoinitiators that completely decompose during UV curing to generate radicals, leaving no residual photoinitiator fragments that could migrate, unlike polymeric photoinitiators that may leave residual chains

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Object-affected harmful factors

If high molecular weight photoinitiators are used to reduce migration, then migration potential decreases, but the ink viscosity increases reducing compatibility with inkjet printheads

Engineering Contradiction:

Improvemigration levelVSAvoidprinthead compatibility

Core Design Contradiction:

Object-affected harmful factorsVSEase of operation

Solution Approach 1:

The patent optimizes the molecular weight parameter to be below 500 amu, which is the critical threshold for both low viscosity (printhead compatibility) and low migration potential, representing a precise parameter optimization

Inventive Principle:

Principle #35Parameter changes

4Productivity

If the ink is cured in ambient air, then the curing process is simpler and faster, but oxygen inhibition reduces cure completeness increasing migratable species

Engineering Contradiction:

Improvecuring speedVSAvoidunreacted monomers

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent uses low molecular weight photoinitiators that generate highly reactive radicals capable of overcoming oxygen inhibition quickly, completing polymerization before oxygen can diffuse in and inhibit the reaction, thus enabling effective air curing

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent creates a composite curing system combining specific photoinitiators with monomer blends that have appropriate reactivity to overcome oxygen inhibition and achieve complete curing in ambient air conditions

Inventive Principle:

Principle #40Composite materials

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 enables the production of low viscosity, pigmented inkjet inks with acceptable pigmentation levels, achieving migratable levels below 10 ppb, suitable for food packaging applications, and compatible with newer printheads, while ensuring minimal contamination and efficient curing under commercially acceptable UV-doses.

Implementation Method 1

a free radical UV-curable composition

Methodology Applied

Scientific EffectPhotopolymerisation: Photopolymerisation

Data Source

PatentEP2956488B1Low migration energy curable inks

Publication Date: 2021.04.14 SUN CHEMICAL CORP

Figure 1

AI summary

Discslosed is a composition such as a pigmented free radical UV-curable inkjet liquid composition for the printing of food packaging materials, which when cured in ambient air produces minimal contamination of the foodstuff. This composition uses non- polymeric photoinitiators having molecular weights less than 500 amu that migrate at levels below the specified SML (specific migration limit).