Acidified Polyester Polyurethane Dispersion for Low-Solvent Coatings
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Solution Overview
Problem
Current aqueous polyester-polyurethane dispersions require high amounts of solvents, are complex to produce, and often result in coatings with poor pigment wetting, optical properties, and adhesion issues due to high molecular weights and susceptibility to saponification, which does not meet modern low-emission and performance requirements.
Innovation Solution
Development of hydroxy-functional polyester-polyurethane dispersions acidified with acid anhydrides, combined with crosslinking resins like melamine resins and polyisocyanates, which are easier to produce, stable, and provide coatings with improved flow, hardness, and resistance properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If water-dilutable polyesters are obtained by reacting hydroxy-functional polyesters with acid anhydrides and neutralizing to convert carboxyl groups into hydrophilic salt groups, then the dispersions can be water-dispersed, but the carboxyl groups have increasing tendency to saponify in aqueous solution with increasing pH, requiring large amounts of organic solvents and complicated dispersing steps
Solution Approach 1:
The patent changes the chemical structure by incorporating carboxyl groups into the polyester backbone via hydrolysis-stable urethane linkages rather than as terminal groups. This structural parameter change allows the carboxyl groups to be protected from saponification while maintaining water dispersibility through neutralization, eliminating the need for large amounts of organic solvents.
Solution Approach 2:
The invention creates a composite structure where carboxyl groups are integrated into the polyester-polyurethane backbone through urethane linkages, forming a hybrid structure that combines the hydrophilic properties of carboxyl groups with the hydrolysis stability of urethane bonds, preventing saponification while maintaining water dispersibility.
2Reliability
If aqueous polyester dispersions are produced by reacting hydroxy-functional polyesters with hydroxycarboxylic acids and polyisocyanates to incorporate acid groups via hydrolysis-stable urethane groups, then storage stability and mechanical properties are improved, but relatively large amounts of solvent are required and significantly higher molecular weights lead to poor pigment wetting and adhesion
Solution Approach 1:
The patent optimizes the molecular weight parameter by producing dispersions with molecular weights of 5,000 to 50,000 g/mol, which is lower than conventional polyester-polyurethane dispersions. This parameter change improves pigment wetting and adhesion while maintaining storage stability through the hydrolysis-stable urethane-linked carboxyl groups.
Solution Approach 2:
The invention introduces carboxyl groups at specific locations within the polyester-polyurethane backbone through controlled reaction with hydroxycarboxylic acids. This localized incorporation of hydrophilic groups provides water dispersibility and storage stability without uniformly increasing molecular weight throughout the entire polymer chain, preserving good pigment wetting and adhesion properties.
3Reliability
If high molecular weight polyester-polyurethane dispersions are used to ensure storage stability, then reliability is improved, but pigment wetting, optical properties, and adhesion to substrates deteriorate
Solution Approach 1:
The patent changes the molecular weight parameter to an optimized range of 5,000 to 50,000 g/mol, balancing storage stability with pigment wetting and adhesion performance. This parameter optimization eliminates the need for excessively high molecular weights while maintaining reliable storage stability through the hydrolysis-stable urethane-linked carboxyl groups.
Solution Approach 2:
The invention creates a simplified polyester-polyurethane structure that copies the essential functional groups (carboxyl groups linked via urethane bonds) needed for storage stability without replicating the unnecessarily high molecular weight of conventional dispersions. This structural copying achieves stability with lower molecular weight, improving pigment wetting and adhesion.
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 new dispersions achieve stable, high-quality coatings with adjustable hardness and elasticity, excellent flow, and enhanced resistance properties, while minimizing solvent content and avoiding saponification issues, making them suitable for low-emission coatings.
Implementation Method 1
Water-dilutable polyesters are obtained by reacting hydroxy-functional polyesters with acid anhydrides and thus incorporating terminal carboxyl groups into the polyester, which, after neutralization, are converted into hydrophilic salt groups
Implementation Method 2
in combination with crosslinking resins, such as melamine resins and/or polyisocyanates, can be cured to give paints and coatings with the required level of properties
Implementation Method 3
Aqueous polyester dispersions are often produced by reacting hydroxy-functional polyesters with hydroxycarboxylic acids and polyisocyanates
Data Source
AI summary
The invention relates to novel acidified, hydroxyfunctional polyester polyurethane dispersions, to a method for the production thereof, and the use thereof in combination with cross-linking resins for producing paints, coatings, and adhesives.