Aqueous Pigment Dispersion via Ionizable Coating

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Solution Overview

Problem

Existing methods for creating stable aqueous dispersions of organic color pigments, such as quinacridone magenta, cyan, and yellow, are difficult and costly, often requiring dispersing agents that increase viscosity and limit formulation latitude in applications like ink-jet inks.

Innovation Solution

A process involving grinding a mixture of pigment, coating agents with ionizable moieties, and a grinding agent, followed by washing and pH adjustment to ionize the coating agents, allowing the pigment to disperse in an aqueous vehicle without additional dispersants, thereby reducing viscosity and enhancing formulation flexibility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If dispersing agents are used to produce stable pigment dispersion, then dispersion stability is improved, but viscosity increases and formulation latitude is reduced

Engineering Contradiction:

Improvedispersion stabilityVSAvoidviscosity

Core Design Contradiction:

Stability of the object's compositionVSQuantity of substance

Solution Approach 1:

The pigment surface is modified with coating agents that provide self-dispersing functionality. The coating agents contain hydrophilic moieties that enable the pigment to spontaneously disperse in aqueous vehicles without requiring additional dispersing agents. This self-service approach eliminates the need for external dispersants while maintaining stable dispersion.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The chemical properties of the pigment surface are changed by introducing coating agents with specific functional groups. The coating agents modify the surface parameters to include hydrophilic characteristics, transforming the pigment from hydrophobic to hydrophilic, which enables water dispersibility without additional chemicals.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If dispersing agents are used to achieve stable pigment dispersion, then dispersion stability is improved, but formulation latitude is reduced

Engineering Contradiction:

Improvedispersion stabilityVSAvoidformulation latitude

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The coating-modified pigment provides inherent dispersing capability through its surface chemistry. This self-service property allows the pigment to disperse autonomously in aqueous media, eliminating the need for formulation adjustments with dispersing agents and thereby expanding formulation flexibility and adaptability.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

By changing the surface parameters of the pigment through coating, the material gains new properties that enable versatile formulation options. The hydrophilic surface allows the pigment to be used in various aqueous-based applications without being constrained by the need for specific dispersing agents, thus improving formulation latitude.

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If chemical reactions are used to modify pigment surface with hydrophilic moieties, then water dispersibility is improved, but process complexity and cost increase

Engineering Contradiction:

Improvewater dispersibilityVSAvoidprocess complexity and cost

Core Design Contradiction:

Stability of the object's compositionVSEase of manufacture

Solution Approach 1:

Coating agents are used as intermediaries to transfer hydrophilic properties to the pigment surface. Instead of directly chemically modifying the pigment through complex reactions, the coating agents serve as mediators that physically adhere to the pigment surface and provide the desired hydrophilic characteristics through a simpler coating process.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention replaces complex chemical reaction systems with a mechanical coating process. Instead of using elaborate chemical synthesis methods to attach hydrophilic groups, the process uses mechanical mixing and coating techniques to apply pre-formed coating agents to the pigment surface, thereby simplifying the manufacturing process.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 stable, low-viscosity aqueous pigment dispersions that are easily dispersible in water, enabling the production of high-quality ink-jet inks with improved color saturation and optical density, while reducing production costs and complexity.

Implementation Method 1

adjusting the pH to ionize said ionizable moiety on said coating agents

Methodology Applied

Scientific EffectIonization: Ionisation

Implementation Method 2

grinding a mixture comprising a pigment, one or a combination of coating agents, a grinding agent and a vehicle

Methodology Applied

Scientific EffectMechanical grinding: Abrasion

Data Source

PatentUS9023141B2Method of preparing aqueous pigment dispersions

Publication Date: 2015.05.05 SP HOLDING II ET INC

AI summary

A process for preparing an aqueous pigment dispersion is provided in which a pigment, a coating agent, a grinding agent and a vehicle are subjected to grinding, followed by removal of the grinding agent and the vehicle to form a press cake, and dispersing the press cake to form a pigment dispersion. Also disclosed is an ink-jet ink containing an aqueous vehicle and the aqueous pigment dispersion thus made.