Water-Dispersible Polyurethane with Amide-Based Stabilization
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Solution Overview
Problem
Existing water-dispersible polyurethanes require high acid values to maintain stability, leading to increased water sensitivity, reduced hydrolytic stability, and higher viscosity, which affects coating durability and application efficiency.
Innovation Solution
Employing a carboxylic acid-bearing isocyanate-reactive compound with a specific structural formula, such as the reaction product of diisopropanol amine and cyclic acid anhydride, to stabilize polyurethanes with lower acid numbers, allowing for higher solids dispersions with manageable viscosity and improved particle size distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If high acid values are used to maintain dispersion stability, then stability is improved, but water resistance and hydrolytic stability deteriorate
Solution Approach 1:
The patent changes the chemical structure of the dispersing agent from traditional carboxylic acid groups to amide groups containing hydrophilic moieties. This parameter change in the molecular structure allows the polyurethane to achieve dispersion stability through hydrogen bonding and hydrophilic interactions rather than ionic carboxylate groups, thereby maintaining stability while improving water resistance and reducing acid number
Solution Approach 2:
The patent introduces amide groups as intermediary structures that mediate between the hydrophobic polyurethane backbone and the aqueous environment. These amide groups with hydrophilic moieties act as intermediaries that provide water dispersibility without requiring high acid values, thus resolving the contradiction between stability and water resistance
2Stability of the object's composition
If high acid values are used to maintain dispersion stability, then stability is improved, but viscosity increases
Solution Approach 1:
The patent changes the dispersing mechanism from ionic carboxylate groups to neutral amide groups with hydrophilic moieties. This parameter change reduces the electrostatic repulsion and intermolecular interactions that cause viscosity increase, allowing for lower viscosity dispersions while maintaining stability through hydrogen bonding and solvation effects
3Stability of the object's composition
If high acid values are used to maintain dispersion stability, then stability is improved, but particle size distribution worsens
Solution Approach 1:
The patent changes the surface chemistry of the polyurethane particles by incorporating amide groups with hydrophilic moieties instead of carboxylic acid groups. This parameter change in surface chemistry provides more uniform steric and hydrogen bonding stabilization, resulting in narrower particle size distribution and reduced sedimentation while maintaining dispersion stability
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 solution results in polyurethanes with lower acid numbers, enhanced water resistance, and reduced viscosity, enabling higher solids content dispersions with improved storage stability and reduced sedimentation, thus improving coating durability and application efficiency.
Implementation Method 1
at least one organic carboxylate group-bearing isocyanate-reactive compound for providing chain-pendant carboxylate ionic dispersing groups in the polyurethane
Implementation Method 2
the amide carboxylic acid compound with formula (1) can be used to stabilize polyurethanes into water
Implementation Method 3
stabilization can be achieved even when using lower amounts of the amide carboxylic acid compound with formula (1) compared to 2,2-dimethylol propionic acid (DMPA), resulting in a lower acid number of the polyurethane
Data Source
AI summary
The present invention relates to an aqueous dispersion comprising dispersed particles comprising a polyurethane comprising at least the following building blocks derived from a) at least one organic polyisocyanate, b) at least one carboxylate group-bearing isocyanate-reactive compound, and c) at least one organic isocyanate-reactive polyol, wherein at least one of the carboxylate group-bearing compounds b) has the following structural formula O II (1) R2(R3)—N—C—R1-COO− wherein R1 is a divalent aliphatic hydrocarbon radical having from 2 to 8 carbon atoms or a divalent cycloaliphatic hydrocarbon radical having from 6 to 8 carbon atoms or a divalent aromatic hydrocarbon radical having from 6 to 8 carbon atoms, R2 and R3 are 2-hydroxypropyl.