Curable Ink Composition for Food Packaging Odor Reduction
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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 free radical curable inks that includes a balanced mixture of polymerizable compounds with acrylate and ethylenically unsaturated functional groups, along with diffusion-hindered photoinitiators, to enhance curing speed, adhesion, and reduce volatile extractables, eliminating the need for deodorizers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional UV-curable inks with low molecular weight photoinitiators and monomers are used, then the ink can be easily formulated and applied, but the cured layer contains high levels of extractables and unpleasant odors
Solution Approach 1:
The patent changes the molecular weight parameter of the photoinitiator from low molecular weight to high molecular weight (polymeric photoinitiators with Mn ≥ 1000 g/mol), which fundamentally alters the extractability and odor characteristics of the cured ink layer while maintaining formulation feasibility
Solution Approach 2:
The patent uses composite photoinitiator systems combining polymeric photoinitiators with dendritic polymeric co-initiators, creating a multi-component system that reduces extractables through the synergistic effect of high molecular weight components that are less prone to migration and extraction
2Object-generated harmful factors
If polymerizable oligomers or crosslinkable polymers are used instead of low molecular weight monomers, then extractables are reduced, but the ink viscosity increases beyond inkjet printing limitations
Solution Approach 1:
The patent segments the polymerizable compounds into two functional categories: compounds A with acrylate groups that provide low viscosity and good jetting properties, and compounds B with ethylenically unsaturated groups that contribute to curing and crosslinking. This segmentation allows each component to fulfill its specific function without compromising the other property
Solution Approach 2:
The patent carefully controls the molecular weight and functional group parameters of the polymerizable compounds to maintain viscosity within inkjet printing limits (typically < 20 cP at jetting temperature) while ensuring sufficient reactivity for complete curing. The specific parameter range for compound A (200-1000 g/mol) and compound B (300-800 g/mol) is optimized to balance these competing requirements
3Speed
If free radical polymerization is used for curing, then high curing speed is achieved, but incomplete curing leaves unreacted monomers that cause odors
Solution Approach 1:
The patent employs a composite photoinitiator system with polymeric photoinitiators and dendritic polymeric co-initiators that work synergistically to achieve both rapid curing initiation and complete polymerization conversion, eliminating unreacted monomers that cause odors while maintaining high curing speed
Solution Approach 2:
The dendritic polymeric co-initiator acts as an intermediary that facilitates complete polymerization by providing multiple co-initiating functional groups that enhance the efficiency and completeness of the free radical polymerization process, ensuring no unreacted monomers remain to cause odors
4Object-generated harmful factors
If cationic polymerization is used instead of free radical polymerization, then complete curing with fewer extractables is achieved, but the curing speed is significantly slower
Solution Approach 1:
The patent replaces the slow cationic polymerization mechanism with a free radical polymerization mechanism using polymeric photoinitiators, which provides both the high curing speed of free radical processes and the complete curing characteristics needed to minimize extractables, effectively substituting one polymerization mechanism for another more suitable one
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 solution achieves improved complete curing, reduced unpleasant odors, and low extractables, making the inkjet inks suitable for food and toy applications with enhanced stability and performance.
Implementation Method 1
UV-curable, in which drying is replaced by polymerization
Implementation Method 2
The polymerization mechanism is usually either free radical polymerization or cationic polymerization
Implementation Method 3
solvent-based, the drying primarily involving evaporation
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; and a polymerizable composition of the liquid consists essentially 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 selected from the group consisting of a vinlyether group, an allylether group, and a allylester group; 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. If the weight percentage of compounds B>24 wt %, then the weight percentage of compounds C>1 wt %, and all weight percentages of A, B, and C are based upon the total weight of the polymerizable composition. At least one polymerizable compound B or C is present in the polymerizable composition if the free radical curable liquid contains no initiator.