Self-Crosslinked Polymeric Dispersant for Stable Inkjet Pigment Dispersion
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Solution Overview
Problem
Existing dispersants for aqueous ink jet inks face challenges in dispersing a wide variety of pigments effectively, leading to instability, jet clogging, and limited tolerance to ink formulation variations, particularly with high co-solvent contents, due to high specific surface areas and low surface charge of pigments like carbon black.
Innovation Solution
A self-crosslinked polymeric dispersant comprising a copolymer with acid, base, hydrophobic, and steric hydrophilic groups that forms crosslinked dispersions in situ via intramolecular/intermolecular charge interactions, minimizing interparticle ionic interactions and providing enhanced stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional dispersants are used for pigments with high specific surface areas and low surface charge, then pigment dispersion is achieved, but stability is poor and jet clogging occurs
Solution Approach 1:
The dispersant employs a composite molecular structure containing both ionic groups (carboxylic acid and amine) and nonionic polyethylene oxide chains. This composite architecture enables dual mechanisms of action: ionic interactions provide strong anchoring to pigment surfaces while polyethylene oxide chains extend into the continuous phase to provide steric stabilization, preventing aggregation and jet clogging
Solution Approach 2:
The invention changes the chemical parameters of the dispersant by incorporating specific functional groups with defined pKa values and molecular weights. The carboxylic acid groups (pKa 4-6) and amine groups (pKa 8-10) provide pH-dependent ionic character, while polyethylene oxide chains with molecular weights of 100-10,000 g/mol provide tunable steric barriers, collectively improving dispersion stability
2Reliability
If dispersants are used to disperse pigments effectively, then color strength is achieved, but tolerance to ink formulation variations is limited
Solution Approach 1:
The dispersant molecule is designed with multiple functional groups that can interact with different types of pigment surfaces through various mechanisms. The ionic groups can engage in electrostatic interactions with charged pigment surfaces, while the polyethylene oxide chains provide universal steric stabilization across different pigment types, enabling broad applicability
Solution Approach 2:
The dispersant exhibits local quality differentiation within its molecular structure: the ionic groups (carboxylic acid and amine) are localized to provide strong surface anchoring and electrostatic stabilization, while the polyethylene oxide chains are positioned to extend into the continuous phase providing steric barriers. This spatial differentiation of functions enhances both formulation tolerance and pigment variety coverage
3Stability of the object's composition
If high co-solvent contents are used in ink formulations, then solubility is improved, but dispersant stability deteriorates
Solution Approach 1:
The invention changes the physical-chemical parameters of the dispersant by incorporating polyethylene oxide chains with specific molecular weights (100-10,000 g/mol) that provide hydrophilic character and hydration shells. These chains maintain dispersant stability in high co-solvent environments by providing steric barriers that are less sensitive to solvent composition changes than purely ionic systems
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 dispersant achieves superior stability in high co-solvent-loaded ink formulations, reducing viscosity, and ensures reliable jetting quality with enhanced color strength and less humidity sensitivity, while being cost-effective and compatible with various film-forming polymers.
Implementation Method 1
forms crosslinked dispersions in situ via intramolecular/intermolecular charge interactions
Implementation Method 2
minimizing interparticle ionic interactions
Data Source
AI summary
A self-crosslinked polymeric dispersant including a self-crosslinked polymeric dispersant comprising: a copolymer comprising: an acid group; a base group; a hydrophobic group; and a steric hydrophilic group.