Solvent-Based Flexographic Ink Resolubility at High Speed
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Solution Overview
Problem
Conventional inks used in flexographic printing deteriorate at high linear speeds, leading to print defects such as irregularly shaped missed areas due to the inability of the ink to wet the printing blanket or substrate, and excessive drying causing pinholing and poor print quality.
Innovation Solution
The formulation of solvent-based flexographic and rotogravure inks with resins and solvents optimized to maintain a compatible solubility parameter range, ensuring resolubility and ink transfer quality even at high speeds by balancing the solubility parameters of the resin and solvent blend, particularly using Hansen's three-component solubility parameter system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional inks are used at high linear speeds, then printing speed increases, but print quality deteriorates due to inability of ink to wet surfaces and excessive drying causing pinholing
Solution Approach 1:
The patent modifies the chemical composition parameters of the ink, specifically adjusting the solvent blend to achieve a solubility parameter between 19.0-23.5 (J/cm³)¹/² and controlling resin content (5-30 wt%), solvent content (40-70 wt%), and colorant content (4-25 wt%). These parameter changes enable the ink to maintain proper wetting and drying characteristics at high linear speeds exceeding 1800 feet per minute, preventing pinholing and ensuring complete surface coverage.
2Productivity
If linear speed exceeds 1800 feet per minute, then productivity increases, but print defects occur due to insufficient dwell time for ink transfer and air displacement
Solution Approach 1:
The patent changes the physical-chemical parameters of the ink formulation, specifically the solvent volatility profile and solubility parameter, to enable rapid yet complete ink transfer within the reduced dwell time at high speeds. The controlled evaporation rate prevents air entrapment and ensures reliable ink deposition even when dwell time is less than a high speed shutter on a 35 mm camera.
Solution Approach 2:
The patent creates a dynamic ink formulation that adapts to the high-speed printing process. The solvent blend is designed to provide optimal wetting during the brief contact period, then rapidly evaporate to prevent smearing, with the solubility parameter carefully controlled to maintain resin resolubility throughout the process. This dynamic behavior ensures consistent print quality across varying high-speed conditions.
3Loss of time
If solvent evaporation is accelerated at high speeds, then drying time decreases, but ink resolubility is compromised leading to poor ink transfer
Solution Approach 1:
The patent carefully balances the solvent composition parameters to achieve a solubility parameter between 19.0-23.5 (J/cm³)¹/², which maintains resin resolubility during the high-speed printing process. The solvent blend is formulated with specific ratios of volatile and less volatile components to control the evaporation profile, ensuring that resin remains soluble during ink transfer while achieving rapid drying to prevent smearing and maintain sharp edges.
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 optimized ink formulations significantly reduce print defects and maintain high print quality at speeds exceeding 1800 feet per minute, ensuring minimal areas of non-coverage and improved lamination bond strength.
Implementation Method 1
as the solvent mixture evaporates, the SP of the overall mixture will remain favorable to the resolubilization of the resin solids in the ink or coating
Implementation Method 2
the inability of the ink to wet out the surfaces of the printing blanket or plate or the substrate
Data Source
AI summary
Formulations for solvent-based flexographic or rotogravure inks, which are capable high-quality, defect-free printing at high speeds, contain flexographic ink resins solutions and solvent mixtures which are designed to maintain a dynamic solubility parameter in the ink as the dry state is approached during the printing process. The inks described show extremely high quality printing at linear press speeds above 1800 fee per minute (ca 0.549 km/min).