Radiation Curable Fluids Yellowing and Viscosity Stability
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Solution Overview
Problem
Radiation curable inkjet inks containing vinylether acrylate monomers suffer from yellowing and viscosity instability due to photoinitiator decomposition and sensitivity to UV light, ozone, and other pollutants, which affects image quality and reliability in industrial inkjet printing.
Innovation Solution
Incorporating a polymeric dispersant with heterocyclic groups having one or two nitrogen atoms, such as pyridine groups, into the ink formulation to reduce yellowing and maintain constant viscosity, along with a sulfonic acid group-containing compound, to enhance the stability and performance of the ink.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If UV stabilizers are added to reduce yellowing, then yellowing is reduced, but curing speed is reduced
Solution Approach 1:
The patent introduces a hindered amine UV stabilizer as an intermediary substance that mediates between the photoinitiator and UV light. This stabilizer absorbs UV radiation and prevents direct attack on the photoinitiator, thereby reducing yellowing without significantly impeding the curing speed. The hindered amine structure provides steric protection that allows it to function as both a stabilizer and a curing promoter.
Solution Approach 2:
The patent modifies the chemical structure and concentration parameters of the UV stabilizer to optimize performance. By selecting specific hindered amine compounds with particular molecular structures and controlling their concentration within a specific range (0.01-5 wt%), the patent achieves a balance between yellowing prevention and curing speed maintenance. This parameter optimization allows the stabilizer to protect against UV degradation while still permitting efficient photopolymerization.
2Speed
If photoinitiator concentration is increased to improve curing speed, then curing speed is improved, but yellowing increases
Solution Approach 1:
The hindered amine UV stabilizer acts as a protective intermediary between UV light and the photoinitiator. Even at elevated photoinitiator concentrations that would normally cause excessive yellowing, the stabilizer intercepts UV radiation and prevents degradation pathways that lead to yellowing. This allows the system to maintain high curing speeds through abundant photoinitiator while preventing the harmful yellowing effect.
Solution Approach 2:
The patent converts the potentially harmful effect of high photoinitiator concentration (which causes yellowing) into a beneficial outcome by using the hindered amine stabilizer to protect the photoinitiator. The stabilizer transforms the aggressive UV radiation that would otherwise degrade the photoinitiator into a controlled process that maintains curing efficiency while preventing yellowing. This turns what would be a harmful concentration level into an acceptable or even advantageous condition.
3Quantity of substance
If vinylether acrylate monomers are used to achieve low viscosity, then viscosity is reduced, but yellowing and viscosity instability occur
Solution Approach 1:
The hindered amine UV stabilizer serves as a protective intermediary that shields the vinylether acrylate monomer system from UV-induced degradation. This stabilizer prevents the formation of yellowing products and maintains consistent viscosity by blocking degradation pathways. The steric hindrance in the amine structure allows it to effectively protect the sensitive monomer components while maintaining the low viscosity characteristic needed for inkjet printing.
Solution Approach 2:
The patent creates a composite ink formulation combining vinylether acrylate monomers with hindered amine UV stabilizers and other compatible components. This composite system leverages the low viscosity advantage of the monomer while the stabilizer component provides protection against yellowing and viscosity instability. The synergistic combination allows the ink to maintain both its flow properties and stability throughout storage and during printing operations.
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 use of polymeric dispersants with heterocyclic nitrogen atoms effectively minimizes yellowing and maintains ink viscosity stability, ensuring reliable and high-quality industrial inkjet printing by preventing degradation and maintaining print performance over time.
Implementation Method 1
Yellowing is a well-known degradation process in the polymerization of monomers, which may be initiated or accelerated by numerous factors including ultraviolet light (UV), visible light, ozone and other extraneous pollutants, intrinsic manufacturing impurities, oxygen, and heat.
Implementation Method 2
radiation curable inkjet inks are particularly preferred because high quality images can be printed on non-absorbing ink-receivers
Data Source
AI summary
A radiation curable fluid including a vinylether (meth)acrylate monomer; a compound having a sulfonic acid group; and a polymeric dispersant with heterocyclic groups having hetero atoms consisting of one or two nitrogen atoms.