Low Migration Inkjet Varnish for Food Packaging
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Solution Overview
Problem
Current inkjet varnishes with low viscosities face challenges in drying and polymerization, leading to reduced printing rates and potential substrate heating, while high viscosity varnishes require significant heating, which is detrimental and costly, and existing low-migration varnishes may contaminate foodstuffs and fail to meet safety standards.
Innovation Solution
A curable varnish composition comprising monofunctional and difunctional acrylate monomers, a photo-initiator with high molecular weight, and optional nanoparticles, designed for inkjet deposition with low viscosity and rapid polymerization at moderate temperatures, ensuring low migration and resistance to yellowing, suitable for food packaging and meeting safety standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the viscosity of the varnish is reduced to meet new inkjet printing head requirements, then the varnish can be deposited by latest inkjet technology, but the drying and polymerization time increases and printing rates are reduced
Solution Approach 1:
The patent changes the chemical composition parameters of the varnish by using specific monomer combinations (monofunctional acrylate, difunctional diacrylate, and multifunctional acrylate with functionality between 3 and 6) and high molecular weight photoinitiators (≥400 g/mol). This compositional parameter change enables the varnish to maintain optimal viscosity for inkjet deposition while achieving rapid polymerization through UV curing, thus resolving the contradiction between depositability and printing rate.
2Productivity
If the viscosity of the varnish is increased to maintain rapid polymerization, then the printing rate can be maintained, but significant heating is required which is detrimental and costly
Solution Approach 1:
The patent replaces the thermal polymerization mechanism with a photopolymerization mechanism using UV light and high molecular weight photoinitiators. This substitution eliminates the need for significant heating while maintaining rapid curing and high printing rates, directly resolving the contradiction between productivity and temperature.
3Reliability
If conventional low-migration varnishes are used to meet safety standards, then migration control is improved, but they may still contaminate foodstuffs and fail to meet evolving safety standards
Solution Approach 1:
The patent creates a composite varnish formulation combining three types of acrylate monomers (monofunctional, difunctional, and multifunctional with functionality between 3 and 6) plus high molecular weight photoinitiators. This composite material approach achieves superior low-migration properties and enhanced safety profile that meets and exceeds evolving food packaging standards, resolving the contradiction between migration control and foodstuff contamination prevention.
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 varnish enables high printing rates without substrate heating, maintains low migration properties, and provides superior resistance to yellowing, meeting safety and performance requirements for food packaging while adhering to safety standards.
Implementation Method 1
a curable varnish composition comprising monofunctional and difunctional acrylate monomers, a photo-initiator with high molecular weight
Implementation Method 2
the less viscous the varnish, the longer the drying or the polymerization of the varnish takes and the more the printing rates are reduced if the speed of transfer of the printed substrates in the ultraviolet oven is reduced to allow sufficient polymerization
Data Source
Figure 1
AI summary
The invention relates to a varnish with low levels of migration for covering the surface of an inkjet-printed and inkjet-deposited substrate, the composition of the varnish comprising at least: a hardenable monofunctional acrylate monomer; a hardenable difunctional diacrylate monomer; a hardenable acrylate monomer and/or oligomer with a sole acrylate functionality, said functionality being between 3 and 6; and a photoinitiator.