Cationic Polyurethane Dispersion Using Low-Boiling Solvents

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Solution Overview

Problem

Existing aqueous cationic polyurethane dispersions face challenges due to poor solubility in typical solvents, reliance on high-boiling-point solvents for removal, limited availability of quaternized amino diols, and non-compliance with Swiss regulations, especially when used in inks and primers contacting food and drinks.

Innovation Solution

Incorporating cationic surfactants into the polyurethane resin dispersion, using polyalkylene oxide in the polyurethane backbone, and adding them during or after the reaction with polyisocyanate and polyether diols to enhance dispersibility and colloidal stability, allowing solvent-free production compliant with Swiss regulations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If quaternized amino diols are used to produce aqueous cationic polyurethane dispersions, then the dispersions can be obtained, but the solubility in typical solvents (acetone, acetonitrile, dioxolane) is poor requiring high-boiling-point solvents

Engineering Contradiction:

Improveaqueous cationic polyurethane dispersion productionVSAvoidsolvent removal difficulty

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention changes the chemical structure parameter of the amino diol from quaternized (permanent positive charge) to tertiary amino (protonatable, conditional positive charge). This parameter change enables solubility in low-boiling-point solvents while maintaining the ability to form aqueous cationic dispersions through protonation in acidic conditions.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention replaces expensive, difficult-to-remove high-boiling-point solvents (NMP, DMF, DMSO) with cheap, easily removable low-boiling-point solvents (acetone, acetonitrile, dioxolane). The volatile solvents can be easily evaporated or distilled off, leaving the polyurethane dispersion without residual solvent contamination.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Reliability

If quaternized amino diols are used, then aqueous cationic polyurethane dispersions can be produced, but compliance with Swiss regulations (Annex 10) is not achieved

Engineering Contradiction:

Improveaqueous cationic polyurethane dispersion productionVSAvoidregulatory compliance for food contact

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention changes the amino diol from quaternized (permanent cationic) to tertiary amino (conditional cationic). This parameter change enables compliance with Swiss regulations because tertiary amino polyols are not listed in Annex 10, whereas quaternized amino diols are restricted. The tertiary amino groups only become cationic under acidic printing conditions, not permanently.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If post-synthesis quaternization is performed to obtain aqueous cationic polyurethane dispersions, then cationic character is achieved, but toxic reagents (methyl sulphate, benzyl chloride) must be removed

Engineering Contradiction:

Improveaqueous cationic polyurethane dispersion productionVSAvoidpurification process complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention performs preliminary selection of safe, non-toxic tertiary amino diols that comply with food contact regulations before synthesis. This eliminates the need for post-synthesis quaternization with toxic reagents and subsequent purification to remove residual toxins. The tertiary amino groups are inherently safe and only become cationic under controlled acidic conditions during inkjet printing.

Inventive Principle:

Principle #10Preliminary action

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 method produces aqueous cationic polyurethane dispersions suitable for inkjet inks, ensuring good adhesion to non-porous substrates and compliance with Swiss regulations, while avoiding toxic reagents and high-boiling-point solvents.

Implementation Method 1

one of the properties of polyurethane based resins is that they assure a good adhesion of the resin to non-porous substrates

Methodology Applied

Scientific EffectAdhesion: Adhesive

Implementation Method 2

adding them during or after the reaction with polyisocyanate and polyether diols to enhance dispersibility and colloidal stability

Methodology Applied

Scientific EffectColloidal stability: Colloid

Data Source

PatentUS12497481B2Aqueous cationic polyurethane dispersions

Publication Date: 2025.12.16 AGFA NV

AI summary

An aqueous polyurethane resin dispersion, the polyurethane resin having a polyalkylene oxide in a side chain thereof and is obtainable by reacting in an organic solvent, a polyisocyanate with a 1,2 or 1,3 polyether diol and with a polymeric diol selected from the group consisting of polyester diol, polyether diol, polycarbonate diol, polyacrylate diol and polyolefin diol and by adding a cationic surfactant or cationic surfactant precursor to the organic solvent.