Toner Emulsion Aggregation via Solvent Flashing
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Solution Overview
Problem
Existing toner processes face challenges in achieving robust and repeatable aggregation and coalescence performance, especially with high acid number polyester resins and the incorporation of wax emulsions without surfactants, which affects fusing performance and relative humidity sensitivity.
Innovation Solution
A process involving solvent flashing to emulsify polyester resin and wax together with reduced or no surfactants, allowing for the formation of a resin and wax emulsion that is then mixed with a colorant and coagulant, heated to aggregate and coalesce into toner particles, reducing the need for separate wax emulsification and surfactant removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wax is added in the form of an aqueous emulsion stabilized with surfactants, then the wax can be effectively incorporated into the toner formulation, but the process becomes complex and requires additional surfactant removal steps
Solution Approach 1:
The patent extracts and eliminates surfactants from the wax emulsion formulation. Instead of using conventional surfactant-stabilized wax emulsions, the invention uses a solvent flashing process that creates a surfactant-free wax-resin emulsion, thereby removing the need for surfactant removal steps and simplifying the overall process.
Solution Approach 2:
The patent combines wax and resin into a single emulsion phase through solvent flashing. By dissolving both components in a common solvent and then flashing off the solvent, the invention creates a unified wax-resin emulsion that eliminates the need for separate wax and resin emulsification processes.
2Ease of manufacture
If separate wax emulsification is performed, then wax can be incorporated into the toner, but additional processing steps and costs are incurred
Solution Approach 1:
The patent merges the wax emulsification step with the resin emulsion formation step into a single solvent flashing operation. Both wax and resin are dissolved in the same solvent, and the simultaneous flashing process creates a combined wax-resin emulsion, eliminating redundant processing steps.
Solution Approach 2:
The solvent flashing process serves multiple functions simultaneously: it dissolves the wax, dissolves the resin, creates the emulsion structure, and removes the solvent all in one operation. This multi-functional approach replaces what would traditionally require separate emulsification, dissolution, and solvent removal steps.
3Adaptability or versatility
If high acid number polyester resins are used, then the toner formulation achieves desired properties, but aggregation and coalescence performance becomes less robust and repeatable
Solution Approach 1:
The patent changes the physical-chemical parameters of the resin by controlling the acid number within a specific range (8-50). This parameter optimization, combined with the solvent flashing process, achieves robust aggregation and coalescence performance while maintaining formulation flexibility for different resin types.
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 enables the production of toner particles with improved fusing performance, reduced surfactant usage, and enhanced relative humidity sensitivity, while minimizing surfactant removal steps and costs.
Implementation Method 1
solvent flashing to emulsify polyester resin and wax together
Implementation Method 2
emulsify the resin and wax for incorporation into the toner
Implementation Method 3
heating to a temperature of from about 30° C. to below the glass transition temperature (Tg) of said resin, wherein the aggregate grows to a size of from about 3 to about 20 microns
Implementation Method 4
heating the mixture to above the resin Tg to coalesce said aggregate
Data Source
AI summary
A process for preparing a toner, includes solvent flashing wax and resin together to emulsify the resin and wax to a sub-micro size; mixing the wax and resin emulsion with a colorant, and optionally a coagulant to form a mixture; heating the mixture at a temperature below a glass transition temperature of the resin to aggregate the resin, colorant, and wax, to form aggregated particles; heating the aggregated particles and coalescent agent at a temperature above the glass transition temperature of said resin, to coalesce the aggregated particles to form toner particles, optionally cooling the mixture; and isolating the toner particles.