Polyurethane Dispersion Chemical Resistance via Oxidative Crosslinking
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Solution Overview
Problem
Aqueous polyurethane dispersions used for coatings face challenges in achieving high chemical resistance while maintaining good mechanical properties, particularly in abrasion resistance, compared to radiation-curable or two-component polyurethane dispersions.
Innovation Solution
The development of polyurethanes with a high fraction of oxidatively drying triglycerides and cycloaliphatic diisocyanates, combined with chain extenders, to create polyurethane dispersions that enhance chemical resistance without compromising mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If auto-oxidatively crosslinkable polyurethane dispersions are used, then chemical resistance is improved, but mechanical properties and abrasion resistance deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating specific fractions of oxidatively drying triglycerides (20-60 wt%) and cycloaliphatic diisocyanates (30-60 wt%) to achieve optimal balance between chemical resistance and mechanical properties
Solution Approach 2:
The patent creates a composite polyurethane system combining oxidatively drying triglycerides with cycloaliphatic diisocyanates and chain extenders, forming a multi-component polymer structure that achieves both chemical resistance and mechanical strength
2Strength
If dehydrated castor oil is used to improve abrasion resistance, then mechanical properties are improved, but the sum total of OH groups and double bonds remains the same
Solution Approach 1:
Instead of dehydrating castor oil to convert OH groups to double bonds, the patent uses the reverse approach by incorporating oxidatively drying triglycerides that naturally contain both OH groups and double bonds, achieving similar mechanical improvement with greater compositional flexibility
3Reliability
If castor oil is mixed with non-functional triglyceride and subjected to transesterification, then mechanical and chemical resistance are improved, but crosslinking density remains lower than radiation-curable or 2k systems
Solution Approach 1:
The patent optimizes the composition parameters by precisely controlling the fractions of oxidatively drying triglycerides and cycloaliphatic diisocyanates, and by selecting specific chain extenders to achieve high crosslinking density through auto-oxidative crosslinking, matching the performance of radiation-curable and 2k systems
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 polyurethane dispersions with significantly increased chemical resistance and maintained mechanical properties, suitable for use in high-grade coatings, such as floor coatings, without the need for additional crosslinking agents or radiation curing.
Implementation Method 1
Coatings comprising such binders crosslink through reaction with atmospheric oxygen (auto-oxidative crosslinking)
Implementation Method 2
polyurethanes which on the one hand have a particularly high fraction of oxidatively drying triglycerides
Data Source
AI summary
The present invention relates to hydrophilized polyurethanes having a particularly high content of hydroxy-functional, unsaturated triglycerides, to a process for preparing polyurethane dispersions based thereon, to the use of the dispersions as binders in oxidatively drying coating materials having particularly high chemical resistance, and to articles and substrates coated with these coating materials.