Ionic Polymer Dispersants for Pigment Ink Stability
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Solution Overview
Problem
Current pigment inks face challenges in achieving high optical density and colloidal stability when printed on plain paper, often requiring high amounts of organic solvent and resulting in poor rub fastness and water fastness, with existing dispersants failing to simultaneously provide both stability and high optical density.
Innovation Solution
A process for preparing polymers that react specific compounds with diisocyanates and isocyanate reactive compounds, incorporating ionic groups to form pre-polymers which are then reacted with organic amines, alcohols, or thiols to create polymers that act as dispersants for particulate solids in aqueous vehicles, enhancing colloidal stability and optical density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If dispersant stabilised pigment inks are formulated to achieve high colloidal stability, then the pigment particles remain dispersed, but the optical density when printed on plain paper becomes low
Solution Approach 1:
The patent modifies the chemical structure of dispersants by incorporating ionic groups (such as carboxylic acid, sulfonic acid, or phosphonic acid groups) into the polymer backbone. This parameter change in the dispersant's molecular structure enables it to provide both colloidal stability through electrostatic repulsion and high optical density by maintaining appropriate pigment dispersion on plain paper surfaces.
Solution Approach 2:
The invention creates composite dispersant molecules that combine hydrophilic ionic groups with hydrophobic segments that can interact with pigment surfaces. This composite structure allows the dispersant to simultaneously stabilize pigment particles in the ink formulation and maintain their dispersion quality when printed on plain paper, resolving the contradiction between colloidal stability and optical density.
2Illumination intensity
If dispersants are used to achieve high optical density on plain paper, then the pigment dispersion quality improves, but significant amounts of organic solvent are required to dissolve/disperse the dispersant
Solution Approach 1:
The patent changes the solubility parameters of dispersants by introducing ionic groups that enhance water solubility. This parameter modification allows the dispersants to be effectively dissolved or dispersed in aqueous vehicles without requiring significant amounts of organic solvent, thereby reducing the organic solvent content while maintaining high optical density performance.
Solution Approach 2:
The invention replaces expensive and environmentally problematic organic solvents with water as the primary vehicle. The ionic dispersants designed in this patent are specifically formulated to work in aqueous environments, eliminating the need for large amounts of organic solvents while maintaining dispersant effectiveness and high optical density.
3Ease of manufacture
If conventional dispersants are used in pigment based inks, then the ink can be formulated, but the final images exhibit poor rub fastness, water-fastness or highlighter smear fastness
Solution Approach 1:
The patent designs composite dispersant molecules with ionic groups that can form strong interactions with both the pigment particles and the substrate surface. These ionic groups (carboxylic acid, sulfonic acid, or phosphonic acid) create enhanced adhesion through electrostatic and chemical bonding, resulting in improved rub fastness, water-fastness, and highlighter smear fastness while maintaining ease of ink formulation.
4Stability of the object's composition
If pigment particles are reduced to sub micron sizes to prevent agglomeration, then colloidal stability improves, but energy consumption and time in the comminution process increases
Solution Approach 1:
The patent incorporates dispersant molecules during the comminution process itself, rather than adding them after particle size reduction. This preliminary action of having dispersants present during milling prevents particle agglomeration in real-time, maintaining colloidal stability throughout the energy-intensive comminution process and reducing the total energy required to achieve stable sub-micron dispersions.
Solution Approach 2:
The invention changes the surface properties of pigment particles through ionic dispersant attachment, which reduces particle-particle attraction forces. This parameter change in surface chemistry allows for more efficient comminution with lower energy input, as particles remain better separated during the size reduction process, reducing the energy and time required to achieve stable sub-micron dispersions.
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 resulting polymers effectively stabilize pigment dispersions in aqueous systems, achieving high optical density and improved fastness properties on plain paper, while reducing the need for excessive organic solvents and energy consumption in the comminution process.
Implementation Method 1
The resulting polymers effectively stabilize pigment dispersions in aqueous systems
Implementation Method 2
incorporating ionic groups to form pre-polymers which are then reacted with organic amines, alcohols, or thiols to create polymers that act as dispersants for particulate solids in aqueous vehicles, enhancing colloidal stability
Data Source
AI summary
A process for preparing a polymer comprising reacting at least the components i), ii) and optionally iii) to form a pre-polymer: i) a compound of the Formula (1); wherein: T1 and T2 are each independently HO—, HS— or HNR1—; Q1 and Q2 independently are —NR2—; A1 and A2 independently are an optionally substituted divalent organic linking group; Z is a halogen; R1 when present is H or an optionally substituted alkyl, aryl or heterocyclyl group; R2 is H or an optionally substituted alkyl, aryl or heterocyclyl group; ii) a diisocyanate; iii) optionally an isocyanate reactive compound; and then reacting the pre-polymer with at least component iv): iv) one or more compounds selected from an organic amine, alcohol or thiol provided that at least one of the organic compounds in component iv) has at least one ionic group.