Random Polyurethane Copolymer Binders for Ink-Jet Durability
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Solution Overview
Problem
Current ink-jet inks lack stability and quality, particularly in terms of durability, print nozzle health, and optical density, due to limitations in polyurethane dispersants and binders.
Innovation Solution
Development of an aqueous ink-jet ink using a random polyurethane copolymer with short hard segments, hydrophilic, and hydrophobic segments, derived from the polymerization of diisocyanate with specific diols, which enhances durability and printability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyurethane dispersants and binders are used in ink-jet inks, then the inks can be manufactured with standard formulations, but the inks exhibit insufficient stability, poor durability, and degraded print nozzle health
Solution Approach 1:
The patent employs a composite binder system comprising multiple polyurethane polymers with different molecular weights (e.g., 10,000-50,000 and 50,000-100,000) and different soft segment-to-hard segment ratios. This composite approach combines the benefits of each component: higher molecular weight polymers provide durability and fastness, while lower molecular weight polymers ensure jetting performance and nozzle health. The result is an ink formulation that achieves superior reliability without sacrificing manufacturability, as the composite nature allows for modular preparation from commercially available polyurethane dispersions.
2Stability of the object's composition
If polyurethane binders with long hard segments are used, then the polymer matrix lacks semi-crystalline regions and intermolecular H-bonding, but the inks achieve better flow properties
Solution Approach 1:
The patent applies local quality by creating distinct micro-regions within the polymer matrix: semi-crystalline hard segment domains provide stability and toughness, while the amorphous soft segment regions maintain flexibility and flow. The hard segments (containing urea or carbamate groups) form localized H-bonding networks that stabilize the ink composition, while the soft segments (polyether or polyester chains) ensure proper jetting speed and nozzle compatibility. This spatial differentiation of properties within the single binder system resolves the contradiction between stability and jetting performance.
3Ease of operation
If ionic groups are incorporated into polyurethane monomers to improve water solubility, then the inks become more dispersible, but the durability and fastness of printed ink deteriorate
Solution Approach 1:
The patent segments the polyurethane molecule into distinct functional regions: hydrophilic segments (containing ionic groups like carboxylate or sulfate) provide water solubility and dispersibility, while hydrophobic segments (aromatic or aliphatic chains) and hard segments (urea/carbamate groups) provide durability and fastness. This segmentation allows each part to perform its specialized function without interfering with the other. The ionic groups are confined to specific segments rather than being distributed throughout the entire polymer chain, preserving the integrity of the durable hard segment regions while ensuring adequate water dispersibility.
4Strength
If the mole % of short-chain diol in polyurethane synthesis is increased to create more hard segments, then the toughness and elasticity improve, but the ink formulation becomes more complex and harder to control
Solution Approach 1:
The patent systematically varies key parameters in polyurethane synthesis, particularly the mole percentage of short-chain diol (ranging from 10-50%) and the choice of diisocyanate (aromatic vs. aliphatic). By establishing specific parameter ranges rather than fixed values, the patent creates a design space that allows manufacturers to adjust toughness and elasticity while maintaining process control. The use of well-defined starting materials (commercially available diisocyanates and diols) and standardized reaction conditions (catalysts, temperature, stoichiometry) simplifies the polymerization process despite the complexity of achieving optimal mechanical properties.
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 significantly improves the durability, printability, and jetting performance of ink-jet inks by forming stable semi-crystalline regions that enhance toughness and elasticity, leading to improved optical density and print quality.
Implementation Method 1
The close proximity of urea or carbamate groups is important when intermolecular H-bonding is desired. The intermolecular H-bonding results in the formation of semi-crystalline regions within the polymer matrix.
Data Source
AI summary
The present disclosure provides novel aqueous ink-jet inks containing an aqueous vehicle, a pigment and a random polyurethane copolymer as a binder. The random polyurethane copolymer contains short hard segments without any ionic group. Also disclosed is the use of these dispersions in an ink-jet ink.