Cross-linked Colorant Dispersion Stability via Polymer Adsorption
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Solution Overview
Problem
Conventional dispersants in aqueous pigment dispersions are prone to displacement by more strongly adsorbing materials, leading to destabilization and flocculation, necessitating a more effective and cost-efficient process for creating stable colorant dispersions.
Innovation Solution
A process involving the use of a partially neutralized dispersant polymer with a cross-linkable moiety, adsorbed onto the colorant, followed by reaction with a cross-linking agent and pH adjustment to greater than 8, while minimizing un-adsorbed polymer interference, and optionally including ultrafiltration for purification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional dispersants are used in aqueous pigment dispersions, then the dispersants can be easily applied and are cost-effective, but they are readily displaced by more strongly adsorbing materials leading to destabilization and flocculation
Solution Approach 1:
The dispersant polymer is pre-crosslinked before being applied to the pigment particles. This preliminary crosslinking creates a stable, resistant network structure that prevents displacement by more strongly adsorbing materials, thereby maintaining dispersion stability while preserving ease of application
Solution Approach 2:
The invention uses a composite dispersant system combining crosslinked polymer chains with pigment particles. The crosslinked structure creates a reinforced dispersant layer that resists displacement, achieving both ease of application and enhanced stability through the composite nature of the crosslinked polymer-particle system
2Productivity
If cross-linking is performed in the presence of un-adsorbed dispersant polymer, then the cross-linking reaction can proceed, but the un-adsorbed polymer interferes with the cross-linking process and reduces efficiency
Solution Approach 1:
The invention removes un-adsorbed dispersant polymer from the system before cross-linking occurs. This extraction step ensures that only the polymer chains adsorbed onto the pigment particles undergo cross-linking, eliminating interference from free polymer and maximizing cross-linking efficiency
Solution Approach 2:
The adsorption of dispersant polymer onto pigment particles is completed before the cross-linking step. This preliminary adsorption ensures that the polymer is in the correct position and bound to the particles when cross-linking begins, preventing interference and ensuring efficient cross-linking of the adsorbed polymer layer
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
This process results in a stable cross-linked colorant dispersion with reduced un-adsorbed polymer, enhancing the stability and effectiveness of the dispersion, suitable for ink-jet printing applications.
Implementation Method 1
it is often required to use a dispersing agent, such as a polymeric dispersant or a surfactant, to produce a stable dispersion of the pigment in the aqueous vehicle
Implementation Method 2
reacting the cross-linkable moiety on the dispersant with a cross-linking agent
Data Source
AI summary
A process for preparing a crossed-linked colorant dispersion is provided in which a partially neutralized dispersant polymer having a cross-linkable moiety is used as a dispersant for a colorant by reacting the cross-linkable moiety on the dispersant with a cross-linking agent.