Epoxy-functional Polyurethane Urea Dispersion Self-crosslinking
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Solution Overview
Problem
Existing polyurethane dispersions face challenges in achieving high hydrolysis resistance and molecular weight without the need for additional crosslinking components, with existing solutions either requiring extra components or having slow crosslinking processes or occupational hygiene concerns.
Innovation Solution
Aqueous polyurethane urea dispersions with epoxy-functional polyurethane units that can be thermally crosslinked as a one-component system or crosslinked with polyfunctional crosslinkers, incorporating specific structural components such as polyisocyanates, polyhydroxy compounds, and isocyanate-reactive polyepoxides to achieve self-crosslinking and high hydrolysis stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If self-crosslinking polyurethane dispersions use carbonyl-containing isocyanate-reactive compounds and add crosslinkers like dihydrazides and diamines, then hydrolysis stability is improved, but device complexity increases due to requiring further components
Solution Approach 1:
The patent combines the polyol and crosslinker functions into a single component by using polyols with both hydroxyl groups (for polyurethane formation) and carbonyl groups (for crosslinking). This eliminates the need for separate crosslinker additions while achieving hydrolysis stability through self-crosslinking during drying.
Solution Approach 2:
The polyols used in the invention serve multiple functions: they act as both the polyol component for polyurethane chain formation and as the crosslinking agent through their carbonyl groups. This multi-functionality reduces system complexity while maintaining hydrolysis resistance.
2Reliability
If fatty acid-modified polyurethane dispersions crosslink under oxygen influence, then hydrolysis resistance is achieved, but productivity decreases due to slow networking over up to seven days
Solution Approach 1:
The patent replaces slow oxidative crosslinking mechanisms with rapid thermal crosslinking. By incorporating carbonyl groups that react with isocyanates, the system enables fast crosslinking during the drying process at elevated temperatures, eliminating the seven-day networking period while achieving hydrolysis resistance.
3Reliability
If self-crosslinking polyurethane dispersions use blocked isocyanate groups, then crosslinking capability is achieved, but occupational hygiene deteriorates due to blocking agent release at elevated temperatures
Solution Approach 1:
The patent extracts the harmful blocking agent from the system by using unblocked isocyanate groups instead. The carbonyl-containing polyols provide crosslinking capability without requiring blocking agents, eliminating the occupational hygiene issue of blocking agent release during application and drying.
4Reliability
If polyurethane dispersions achieve high molecular weight for improved coating properties, then solvent stability and hydrolysis resistance improve, but device complexity increases due to need for additional crosslinking components
Solution Approach 1:
The patent merges the high molecular weight polyol component and crosslinker into a single multifunctional component. The polyols with molecular weights of 400-8000 g/mol contain both the polyol chains for high molecular weight construction and carbonyl groups for crosslinking, achieving solvent stability and hydrolysis resistance without additional components.
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 enables the production of coatings with excellent hydrolysis resistance and high molecular weight, allowing for thermal self-crosslinking or crosslinking with polyfunctional compounds, improving the properties of the coatings significantly.
Implementation Method 1
epoxy-functional polyurethane polyureas can be thermally crosslinked without the addition of further compounds (one-component (1K) system)
Implementation Method 2
The polyurethane urea dispersions according to the invention contain as structural components a) one or more polyiscocyanate compounds with a functionality ≥2, b) one or more polyhydroxy compounds
Implementation Method 3
isocyanate-reactive polyepoxides to achieve self-crosslinking
Data Source
AI summary
The present invention relates to aqueous polyurethane urea dispersions having integral functional groups and coating agents produced therefrom, to a method for the production thereof, and to the use thereof for producing coating agents.