Water-Dispersible Modified Polyisocyanates With Low-Shear Mixing
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Solution Overview
Problem
Existing water-dispersible polyisocyanates face issues with high viscosity requiring high shear force for dispersion, reduced isocyanate group concentration leading to lower crosslinking density, poor storage stability due to polymerization, and increased VOC content when diluted with solvents.
Innovation Solution
A water-dispersible modified polyisocyanate is produced through the reaction of a water-dispersible polyisocyanate and an isocyanate-reactive component, without additional hydrophilizing agents, allowing manual stirring and direct mixing with other components, resulting in low viscosity and improved dispersibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If polyether is introduced to improve water dispersibility of polyisocyanate, then dispersibility is improved, but isocyanate group concentration and crosslinking density are reduced
Solution Approach 1:
The patent changes the chemical structure parameters of the polyisocyanate by introducing specific cyclic carbonates and cyclic carbonic ester groups with defined molecular weights and functions. This allows achieving water dispersibility through structural modification rather than adding large amounts of polyether, thereby maintaining high isocyanate group concentration (NCO content ≥ 20%) and crosslinking density.
2Ease of operation
If high shear force is applied to disperse polyisocyanate in water, then dispersibility is improved, but energy consumption and processing complexity increase
Solution Approach 1:
The patent modifies the molecular structure parameters of polyisocyanate to include specific hydrophilic groups (cyclic carbonates and cyclic carbonic esters) that inherently provide water compatibility. This structural parameter change enables the material to disperse in water with minimal shear force, eliminating the need for high-energy mixing processes.
3Ease of operation
If carboxylic acid groups are used to modify polyisocyanate for water dispersibility, then dispersibility is improved, but storage stability deteriorates due to polymerization
Solution Approach 1:
The patent uses cyclic carbonate and cyclic carbonic ester groups as temporary hydrophilic modifications that do not lead to permanent polymerization. These groups provide water dispersibility without the catalytic polymerization side effects of carboxylic acid groups, ensuring storage stability while maintaining ease of use.
Solution Approach 2:
The patent extracts the harmful catalytic polymerization property from the modification approach while retaining the beneficial water dispersibility. By selecting cyclic carbonate and cyclic carbonic ester groups instead of carboxylic acid groups, the invention removes the unwanted side reaction while preserving the desired water compatibility.
4Ease of operation
If sulfonic acid group-modified polyisocyanate is used to improve water dispersibility, then dispersibility is improved, but VOC content increases when diluted with solvent
Solution Approach 1:
The patent changes the chemical parameters of the polyisocyanate by incorporating cyclic carbonate and cyclic carbonic ester groups that provide inherent water dispersibility without requiring solvent dilution. This eliminates VOC emissions while maintaining good dispersibility, as the modified polyisocyanate can be directly used in aqueous systems.
Data Source
AI summary
The invention relates to a water-dispersible modified polyisocyanate and use thereof, especially as a crosslinking component in water-soluble or water-dispersible coating compositions. The water-dispersible modified polyisocyanate can be obtained by the reaction of a system comprising a water-dispersible polyisocyanate and an isocyanate-reactive component; wherein the viscosity of the water-dispersible modified polyisocyanate is 3000 mPa·s-11000 mPa·s, which is measured with a MV-DIN rotor according to DIN EN ISO 3219:1994-10 at 23° C. and a shear rate of 10 s−1. The modified polyisocyanate according to the present invention has good manual stirring behavior and good dispersibility, and the coating formed by the coating composition containing the modified polyisocyanate has high gloss and good transparency.