Curable Inkjet Inks for Food Packaging Curing Speed and Odor
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Solution Overview
Problem
Current curable inkjet inks face challenges in achieving high curing speed and complete curing while minimizing unpleasant odors and extractables, particularly in food packaging applications, where traditional methods either result in incomplete curing or leave behind volatile monomers that can cause odors.
Innovation Solution
The development of a specific composition for inkjet inks that includes a balanced mixture of polymerizable compounds with acrylate groups, photoinitiators, and surfactants, optimized to achieve rapid and complete curing with reduced volatile extractables, using a free radical curable liquid formulation that includes specific ratios of monofunctional, difunctional, and trifunctional acrylates, along with diffusion-hindered photoinitiators to prevent monomer retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If free radical polymerization is used for curing inkjet inks, then curing speed is improved, but the cured image layer contains more extractables (unreacted monomers) causing unpleasant odors
Solution Approach 1:
The patent changes the chemical parameters of the polymerization system by using cationic polymerization instead of free radical polymerization, and further optimizes by using multifunctional monomers with specific functional groups (epoxide, oxetane, cyclic carbonate) to achieve complete curing with minimal extractables, resolving the contradiction between curing speed and extractable content
Solution Approach 2:
The patent employs composite curing systems combining multiple monomer types (epoxide, oxetane, cyclic carbonate) with complementary polymerization characteristics to achieve both rapid curing and complete reaction, minimizing unreacted monomers while maintaining high curing speed
2Object-generated harmful factors
If cationic polymerization is used for curing inkjet inks, then complete curing is achieved with fewer extractables, but the polymerization process is slower
Solution Approach 1:
The patent optimizes cationic polymerization by selecting specific multifunctional monomers and photoinitiator systems that enhance reaction kinetics, achieving both complete curing and improved polymerization speed through parameter optimization of the cationic system
Solution Approach 2:
The patent uses multifunctional monomers that can participate in multiple polymerization reactions simultaneously, allowing the system to achieve complete curing through multiple pathways while maintaining fast reaction rates, making the cationic system as effective as free radical systems
3Ease of manufacture
If low molecular weight monomers are used in curable inkjet inks, then the ink viscosity remains low for jetting, but the cured layer contains more extractables
Solution Approach 1:
The patent changes the molecular weight parameter of the monomers by using high functionality monomers ( trifunctional, tetrafunctional) instead of low molecular weight monomers, achieving complete curing that eliminates extractables while the high functionality compensates for the increased molecular weight to maintain crosslinking efficiency
Solution Approach 2:
The patent creates a composite monomer system combining different functionality levels and types (epoxide, oxetane, cyclic carbonate) that work synergistically to achieve complete polymerization, ensuring no extractables remain while maintaining appropriate ink rheology for jetting
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 results in inkjet inks that exhibit improved adhesion, complete curing, and minimal unpleasant odors without the need for deodorizers, making them suitable for food and toy applications with low levels of extractables, thus enhancing their safety and performance.
Implementation Method 1
The curable liquid or ink is preferably a radiation curable inkjet liquid, and most preferably a UV radiation curable inkjet liquid... at least one photoinitiator... The polymerizable composition consists essentially of: a) 25-100 wt % of one or more polymerizable compounds A having at least one acrylate group
Data Source
AI summary
A free radical curable liquid for inkjet printing of food packaging materials includes no initiator or otherwise one or more initiators selected from the group consisting of non-polymeric di- or multifunctional initiators, oligomeric initiators, polymeric initiators, and polymerizable initiators; wherein the polymerizable composition of the liquid consists of: a) 25-100 wt % of one or more polymerizable compounds A having at least one acrylate group G1 and at least one second ethylenically unsaturated polymerizable functional group G2 different from the group G1; b) 0-55 wt % of one or more polymerizable compounds B selected from the group consisting of monofunctional acrylates and difunctional acrylates; and c) 0-55 wt % of one or more polymerizable compounds C selected from the group consisting of trifunctional acrylates, tetrafunctional acrylates, pentafunctional acrylates and hexafunctional acrylates.