Aqueous Ink Composition for Low-Temperature Cure and Resolubility
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Solution Overview
Problem
Existing aqueous inkjet ink compositions fail to achieve resolubility and cure at low temperatures while maintaining stability and preventing printhead blockage, especially when using self-crosslinking styrene-acrylic dispersions alone.
Innovation Solution
Combining self-crosslinkable styrene-acrylic polymer dispersions with hydroxyl-functional polyurethane dispersions (OH-PUDs) to enhance resolubility and allow curing at temperatures below 100°C, using amines with boiling points between 130°C and 250°C to further improve resolubility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional crosslinking methods are used to achieve water resistance, then water resistance is improved, but pH instability and printhead blockage occur
Solution Approach 1:
The patent introduces a polyol component as an intermediary substance that mediates between the crosslinking agent and the aqueous ink composition. The polyol reacts with the crosslinking agent to form a complex that then crosslinks with the polymer, preventing direct pH-disrupting reactions while enabling water resistance. This intermediary approach resolves the contradiction by allowing crosslinking without the harmful pH effects of conventional direct crosslinking methods.
2Stability of the object's composition
If high co-solvent concentrations are used to maintain stability, then stability is improved, but printing speed decreases due to slower drying
Solution Approach 1:
The patent changes the chemical parameters of the ink composition by introducing a polyol component with specific molecular weight and hydroxyl value ranges. This parameter change allows the system to achieve stability with reduced co-solvent concentrations (5-30% by weight), thereby improving printing speed while maintaining ink stability through the polyol's stabilizing effect rather than relying on high co-solvent content.
3Strength
If self-crosslinking styrene-acrylic dispersions are used to achieve water resistance, then water resistance is improved, but resolubility is lost causing printhead blockage
Solution Approach 1:
The patent applies partial crosslinking by controlling the ratio of crosslinking agent to polymer and using a polyol intermediary to moderate the crosslinking reaction. This partial action approach creates a balance where sufficient crosslinking provides water resistance while leaving enough uncrosslinked or reversibly crosslinked segments to maintain resolubility, preventing printhead blockage while achieving the desired water resistance.
4Strength
If crosslinking agents are added to improve water resistance, then water resistance is improved, but pH instability occurs
Solution Approach 1:
The patent uses polyol as an intermediary that buffers the pH impact of crosslinking agents. The polyol reacts with the crosslinking agent first, forming a complex that then crosslinks with the polymer. This two-step process prevents the direct pH-disrupting reaction between crosslinking agents and the aqueous ink composition, maintaining pH stability while achieving water resistance.
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
Inks exhibit excellent resolubility and water resistance after drying, preventing printhead blockage and achieving high-quality prints at ambient or elevated temperatures.
Implementation Method 1
The polymer contains ketone, or aldehyde, groups as part of its molecular structure which can then react, upon drying, with multifunctional primary (or secondary) amines to affect the crosslinking reaction
Implementation Method 2
A number of other patents describe the use of optional crosslinkers in combination with PUDs to enable improved resistance properties, including; WO2019074683, US20190106587
Data Source
AI summary
Curable aqueous printing ink compositions, especially inkjet, having excellent resolubility, comprising self-crosslinkable styrene-acrylic polymer dispersions and hydroxy-functional PUDs.