Energy-Curable Ink Viscosity Modifiers for Low-Shear Flow
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Solution Overview
Problem
Energy curable inks, particularly UV-curable flexographic inks, exhibit high viscosity at low shear rates, leading to handling difficulties and printing challenges due to their thixotropic nature.
Innovation Solution
Incorporation of high molecular weight, low volatile solvents such as 2,2,4-trimethyl-1,3-pentanediol isobutyrate (Texanol), 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB), and dipropylene glycol butyl ether (DPGBE) into the ink composition to reduce viscosity and improve thixotropic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If energy curable inks are formulated with conventional solvents or no solvents, then the ink maintains high viscosity at low shear rates which provides good print stability, but the ink becomes difficult to handle and pump into the anilox chamber
Solution Approach 1:
The patent applies parameter changes by introducing specific high molecular weight solvents (Texanol, TXIB, DPGBE) that alter the rheological parameters of the ink. These solvents change the viscosity-shear rate relationship, specifically reducing low shear rate viscosity while maintaining or enhancing thixotropic behavior, thereby improving pumpability without sacrificing print stability
Solution Approach 2:
The patent uses composite material approach by combining specific solvent molecules (Texanol, TXIB, DPGBE) with the ink vehicle system. These solvents form a composite formulation that exhibits synergistic effects: the solvent molecules interact with the resin and pigment particles to modify the overall rheological properties, achieving both low viscosity at rest and high viscosity during printing
2Productivity
If high molecular weight solvents like Texanol are added to reduce viscosity, then flow and pumpability improve, but the ink composition becomes more complex
Solution Approach 1:
The patent changes the chemical parameter of the solvent component by selecting high molecular weight solvents with specific functional groups. This parameter change allows the solvent to perform multiple functions: viscosity reduction, thixotropy enhancement, and print stability improvement, thereby managing composition complexity while achieving productivity goals
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 solvents significantly lower the low shear rate viscosity by up to 25% or more, enhancing the flow and pumpability of the inks, making them more user-friendly for printing processes.
Implementation Method 1
Thixotropy is a property well known to printers and ink formulators, and refers to viscous or gelled material that will flow when agitated or shear stressed, but subsequently reverts to a viscous or gelled material once the agitation or shear stress stops.
Data Source
AI summary
The present invention provides energy curable thixotropic compositions comprising low amounts of 2,2,4-trimethyl-1,3-pentanediol isobutyrate (Texanol); 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB); or dipropylene glycol butyl ether (DPGBE mixes isomers), or combinations thereof. The addition of the selected solvents in amounts of about 0.5 wt % to 3 wt % reduced the low shear rate viscosity of the energy curable thixotropic compositions.