Cross-linked Polyurethane Dispersant for Ink Stability
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Solution Overview
Problem
Aqueous inkjet inks face challenges in maintaining stable pigment dispersions, particularly in ink-jet printing applications, where pigment agglomeration and flocculation occur due to the lack of solubility in aqueous vehicles, leading to issues with durability, rub-fastness, and highlighter pen fastness.
Innovation Solution
The development of an aqueous inkjet ink with a cross-linked polyurethane dispersant containing cross-linkable moieties pendent to the polymer backbone and terminal to the polymer chain, which reacts with a cross-linking agent to form a stable pigment dispersion, combined with a non-reactive polymeric binder for enhanced stability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a polymeric dispersant is used to disperse pigment particles in aqueous vehicle, then the pigment dispersion can be formed, but the pigment particles tend to agglomerate or flocculate during storage and use
Solution Approach 1:
The invention uses a composite dispersant system comprising a polymeric dispersant combined with a cross-linking agent. The polymeric dispersant contains cross-linkable functional groups that react with the cross-linking agent to form a cross-linked network structure on the pigment particle surface, creating a composite material that provides both dispersion stability and durability.
Solution Approach 2:
The invention changes the chemical state of the dispersant from linear polymeric chains to cross-linked network structures through chemical reaction. This parameter change in molecular architecture transforms the dispersant's properties, enhancing both steric stabilization and mechanical adhesion to the pigment particles.
2Ease of operation
If pigment is dispersed in liquid aqueous vehicle, then the ink can be formulated, but pigment particles agglomerate or flocculate during storage and jetting cycles
Solution Approach 1:
The cross-linked polymeric dispersant acts as an intermediary between the hydrophobic pigment particles and the hydrophilic aqueous vehicle. The dispersant's cross-linked structure provides a bridge that maintains compatibility between immiscible phases, enabling stable dispersion of insoluble pigment in water-based ink.
3Stability of the object's composition
If conventional dispersants are used to improve dispersion stability, then storage stability improves, but durability, rub-fastness and highlighter pen fastness are insufficient
Solution Approach 1:
The invention applies local quality enhancement by creating cross-linked regions specifically at the pigment particle surface while maintaining the aqueous dispersion properties in the bulk ink. This localized cross-linking provides durability and fastness where needed (at the pigment-binder interface) without compromising the ink's flow and jetting characteristics.
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 solution provides highly stable, high-quality inks with improved smudge resistance and highlighter smear performance, ensuring durability and fastness in ink-jet printing applications by maintaining the stability of pigment dispersions throughout storage and repeated jetting cycles.
Implementation Method 1
a cross-linked pigment dispersion based on a polyurethane dispersant having cross-linkable moieties both pendent to the polymer backbone and terminal to the polymer chain, and the cross-linking of these moieties with a cross-linking agent
Data Source
AI summary
The present disclosure provides an ink-jet ink containing an aqueous ink vehicle, an aqueous dispersion and a polymeric binder. The aqueous dispersion contains a colorant and a polyurethane dispersant, wherein the polyurethane dispersant is made with a polymer having cross-linkable moieties that are cross-linked with a cross-linking agent.