Porous Core-Shell Toner via Freeze-Drying

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Solution Overview

Problem

Conventional electrophotographic toner powders face issues such as low yield, high manufacturing costs, and adverse effects on developer life due to wide particle size distribution and brittle binder polymers, which also lead to increased toner mass and poor print quality.

Innovation Solution

The development of core-shell polymer particles with a porous core and non-porous shell, where the core has micro, meso, and macro pores, and the shell has minimal porosity, achieved through an oil-in-water emulsion process with phase separation, allowing for controlled porosity and size distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional grinding method is used to produce toner particles, then manufacturing process is simple, but particle size distribution is wide and yield is low

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoidparticle size distribution

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent utilizes phase transition of water from liquid to solid (freezing) to create a controlled environment for particle formation. The aqueous suspension is frozen and then lyophilized, allowing uniform particle size distribution to be achieved while maintaining manufacturing simplicity. The phase transition enables precise control over particle morphology without complex grinding processes.

Inventive Principle:

Principle #36Phase transitions

Solution Approach 2:

The patent replaces the mechanical grinding system with a chemical/physical process involving freezing and lyophilization. Instead of mechanically pulverizing polymer to achieve particle size distribution, the invention uses controlled phase transitions and solvent removal to naturally form particles with narrow size distribution, eliminating the need for brittle polymers and complex grinding equipment.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If low molecular weight binder polymer is used to improve grinding, then grinding efficiency increases, but toner flakes form and carrier particles scum

Engineering Contradiction:

Improvegrinding efficiencyVSAvoidtoner quality

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent uses freezing and lyophilization phase transitions to form toner particles directly without mechanical grinding. This eliminates the need for low molecular weight binders that cause flaking and scumming, while still achieving efficient particle production. The controlled phase transition process naturally produces particles with appropriate properties for electrophotographic use.

Inventive Principle:

Principle #36Phase transitions

Solution Approach 2:

The invention replaces mechanical grinding with a freeze-drying process that forms particles through controlled phase transitions. This substitution eliminates the adverse effects of low molecular weight binders (flaking, scumming) while maintaining high productivity. The process produces reliable toner quality without the trade-offs associated with conventional grinding methods.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Quantity of substance

If porous toner particles are used to reduce toner mass, then cost per page decreases, but surface properties may be compromised

Engineering Contradiction:

Improvetoner massVSAvoidsurface properties

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent creates particles with non-uniform internal structure through controlled freezing and lyophilization. The process generates particles that are porous internally (reducing mass) while maintaining appropriate surface properties (spheroidal shape, smooth exterior) for electrophotographic performance. This local differentiation of structure allows simultaneous achievement of reduced toner mass and maintained reliability.

Inventive Principle:

Principle #3Local quality

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 approach reduces toner mass, lowers costs, improves print quality, and maintains surface properties similar to solid toners, enhancing the electrophotographic process by reducing curl and image relief while expanding its application areas.

Implementation Method 1

removing the solvent

Methodology Applied

Scientific EffectEvaporation: Evaporation

Implementation Method 2

oil-in-water emulsion process with phase separation

Methodology Applied

Scientific EffectPhase separation: Phase Change

Data Source

PatentUS8940362B2Method for manufacturing porous particles with non-porous shell

Publication Date: 2015.01.27 EASTMAN KODAK CO

AI summary

A method of manufacturing porous core-shell polymer particles having a nonporous shell including: providing a first organic solvent containing a dissolved polymer; dispersing the organic solvent in an aqueous phase containing a stabilizer to form an emulsion; adding the emulsion to a second organic solvent wherein the second organic solvent is miscible with water and the first organic solvent, and a non-solvent for the polymer; and evaporating the first and second organic solvents from the emulsion to form core-shell polymer particles. The method results in core-shell polymer particles comprising a common binder polymer for the core and the shell wherein the core has a porosity and the shell is non-porous. The particles have a porosity from 10 to 70 percent.