Urea-Terminated Polyurethane Dispersants for Inkjet Stability
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Solution Overview
Problem
Current polyurethane dispersants used for pigments in inkjet inks lack stability and performance, particularly in maintaining particle dispersion and inkjet printing quality, as they are limited by their water solubility and structural properties.
Innovation Solution
Development of urea-terminated polyurethane dispersants with grafted alkyl, aryl, or fluoroalkyl substituents, which provide enhanced stability and dispersion properties through ionic substitution and specific molecular structures, allowing for improved particle size control and inkjet ink performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyurethane dispersants with excess isocyanate reactive groups are used, then pigment dispersion is achieved, but stability and performance are insufficient
Solution Approach 1:
The patent changes the terminal group parameter from conventional isocyanate-terminated or hydroxyl-terminated polyurethanes to urea-terminated polyurethanes. This parameter change fundamentally alters the molecular structure's interaction with pigment particles and water, providing enhanced dispersion stability without requiring complex crosslinking structures. The urea terminal groups offer improved hydrogen bonding capabilities and water solubility control.
Solution Approach 2:
The patent creates a composite molecular structure combining polyurethane backbone with grafted alkyl, aryl, or fluoroalkyl substituents and ionic groups. This composite structure integrates multiple functional properties: the polyurethane provides base dispersancy, the grafted hydrophobic groups enhance pigment affinity, and the ionic groups improve water solubility and electrostatic stabilization, achieving superior stability without excessive structural complexity.
2Stability of the object's composition
If polyurethane dispersants with limited water solubility are used, then pigment binding is achieved, but aqueous dispersion stability deteriorates
Solution Approach 1:
The patent applies local quality by incorporating ionic groups at specific locations within the polyurethane molecule (through the diol component) rather than uniformly throughout. This localized ionic substitution provides water solubility and electrostatic repulsion where needed for aqueous stability, while maintaining hydrophobic regions for pigment affinity, thus resolving the contradiction between water solubility and pigment binding.
Solution Approach 2:
The patent changes the water solubility parameter by introducing ionic groups (such as carboxylate, sulfonate, or phosphate groups) into the diol component of the polyurethane. This parameter change transforms the dispersant from water-insoluble or limited-solubility to water-soluble or water-dispersible, enabling stable aqueous dispersions while maintaining pigment binding capabilities through the hydrophobic grafted groups.
3Manufacturing precision
If particle size is reduced to improve inkjet performance, then printing quality improves, but dispersion stability becomes more difficult to maintain
Solution Approach 1:
The patent uses the urea-terminated polyurethane with grafted substituents as an intermediary substance between pigment particles and water. This intermediary provides steric hindrance through the grafted alkyl/aryl/fluoroalkyl groups and electrostatic repulsion through ionic groups, preventing aggregation of fine pigment particles and maintaining dispersion stability at the small particle sizes required for inkjet printing performance.
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 urea-terminated polyurethane dispersants achieve stable aqueous dispersions with particle sizes less than 300 nm, enhancing the performance and stability of inkjet inks, including improved washfastness and colorfastness on printed textiles.
Implementation Method 1
the ionic dispersant is physically adsorbed to the particle
Implementation Method 2
the polymeric ionic dispersant stably disperses the pigment in the aqueous vehicle
Data Source
AI summary
The present invention relates to urea terminated polyurethane dispersants based on certain diols which have grafted alkyl, aryl or fluoroalkyl substituents, aqueous dispersions of such polyurethanes, the manufacture of the urea terminated polyurethane dispersions and inks containing pigments and/or disperse dyes dispersed with these urea terminated polyurethane dispersants.