Cross-linked Polyurethane Dispersant for Ink-jet Pigment Stability
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Solution Overview
Problem
Current ink-jet printing technologies face challenges in achieving stable, durable, and high-quality inks due to pigment agglomeration and flocculation issues, which affect storage and printing performance, particularly in ink-jet applications requiring good rub-fastness, wet-fastness, and highlighter pen fastness.
Innovation Solution
The development of an aqueous inkjet ink using a cross-linked polyurethane dispersant with cross-linkable moieties pendent to the polymer backbone and terminal to the polymer chain, reacted with a cross-linking agent such as epoxide, isocyanate, or carbodiimide, to create a stable pigment dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional polymeric dispersants are used to disperse pigment in aqueous vehicle, then pigment dispersion is achieved, but pigment particles tend to agglomerate or flocculate during storage and printing
Solution Approach 1:
The patent uses a composite dispersant system combining polyurethane polymer backbone with grafted acrylic acid moieties and cross-linked silane networks. This multi-component composite structure provides both steric stabilization (from polymer chains) and chemical bonding (from silane cross-links to pigment surface), preventing pigment agglomeration more effectively than conventional single-component dispersants.
Solution Approach 2:
The patent modifies the dispersant structure by introducing cross-linkable silane groups that can form covalent bonds with pigment surfaces. This chemical parameter change transforms the dispersant from purely physical adsorption to chemical bonding, dramatically improving dispersion stability during storage and printing cycles.
2Ease of operation
If pigment is dispersed in liquid aqueous vehicle, then ink formulation is achieved, but pigment particles agglomerate or flocculate during storage and printing
Solution Approach 1:
The patent introduces silane-cross-linked polyurethane dispersant as an intermediary between pigment particles and aqueous vehicle. This intermediary forms strong chemical bonds with pigment surfaces while maintaining compatibility with aqueous medium, enabling stable dispersion without requiring complex formulation adjustments.
3Productivity
If current dispersants are used in ink-jet printing, then basic ink functionality is achieved, but requisite stability, durability, optical density and chroma are not provided
Solution Approach 1:
The patent changes the chemical parameters of the dispersant by incorporating cross-linkable silane groups that form covalent bonds with pigment surfaces. This parameter change enhances pigment-binder interaction, improving ink stability, durability, and color properties (optical density and chroma) while maintaining ink-jet printing functionality.
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 cross-linked polyurethane dispersant provides enhanced stability, durability, and optical density, preventing pigment agglomeration and ensuring consistent performance throughout repeated jetting cycles and storage, thereby meeting the demanding requirements of ink-jet printing.
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 comprising an aqueous ink vehicle and an aqueous dispersion, the aqueous dispersion comprises a colorant and a polyurethane dispersant, wherein said polyurethane dispersant is comprised of a polymer having a cross-linkable moiety, wherein the cross-linkable moiety is cross-linked with a cross-linking agent.