Modified Polyisocyanate Coatings Manual Dispersion
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Solution Overview
Problem
Current water-dispersible modified polyisocyanates face challenges such as high viscosity requiring high shear forces for dispersion, reduced crosslinking density, and poor storage stability, as well as increased VOC content due to solvent dilution, which affect the environmental and human health impact.
Innovation Solution
A modified polyisocyanate is developed through a reaction involving aminosulfonic acid, polyisocyanate, tertiary amine, and optionally polyether alcohol, forming iminooxadiazinedione and isocyanurate structures, allowing for manual stirring and dispersion without solvent dilution, with a sulfonate group content of 0.75% to 1.1% by weight, achieving a viscosity of 500 mPa·s to 10000 mPa·s.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If nonionically modified polyisocyanates are used to achieve water dispersibility, then dispersibility is improved, but viscosity becomes very high requiring high shear force for uniform dispersion
Solution Approach 1:
The invention changes the chemical parameter by introducing ionic sulfonate groups instead of nonionic polyether groups. This fundamental parameter change transforms the dispersion mechanism from relying on hydrophilic polyether chains to relying on ionic sulfonate groups that interact with water molecules, thereby reducing viscosity and enabling dispersion without high shear force.
Solution Approach 2:
The invention creates a composite structure by combining polyisocyanate with aminosulfonic acid moieties. This composite material integrates the crosslinking functionality of polyisocyanate with the water-dispersibility of sulfonate groups, achieving both desired properties without the viscosity problems of polyether modification.
2Ease of operation
If polyether modified polyisocyanate is used as crosslinking agent, then water dispersibility is improved, but crosslinking density is significantly reduced
Solution Approach 1:
The invention changes the modifying group from polyether to aminosulfonic acid. This parameter change allows the sulfonate group to provide water dispersibility while the isocyanate groups remain available for crosslinking reactions, thus maintaining high crosslinking density despite improved water dispersibility.
3Ease of operation
If carboxylic acid group modified polyisocyanate is used to reduce viscosity, then water dispersibility is improved, but storage stability becomes poor due to gelation
Solution Approach 1:
The invention uses sulfonic acid groups instead of carboxylic acid groups. The sulfonate groups provide similar water dispersibility but with crucially different chemical stability - they do not catalyze isocyanate polymerization like carboxylate groups do, thus preventing gelation and maintaining storage stability.
Solution Approach 2:
The invention converts the potential harm of ionic groups catalyzing isocyanate polymerization (as seen with carboxylic acids) into a benefit by selecting sulfonic acid groups that provide ionic water dispersibility without the harmful catalytic effect, thus eliminating the storage stability problem.
4Ease of operation
If sulfonic acid group modified polyisocyanate is diluted with solvent to reduce viscosity, then ease of mixing is improved, but VOC content increases causing environmental damage
Solution Approach 1:
The invention optimizes the sulfonate group content to a specific range (0.75-1.1% by weight) and controls viscosity through chemical composition rather than solvent dilution. This parameter change enables the material to be mixed manually without adding VOC-containing solvents, thus eliminating environmental harm while maintaining ease of operation.
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 modified polyisocyanate enables uniform dispersion and high gloss, transparency, and low VOC content in coatings, improving manual stirring behavior and storage stability while reducing environmental and health hazards.
Implementation Method 1
A modified polyisocyanate is obtained by a reaction of a system comprising: a. at least an aminosulfonic acid, b. at least a polyisocyanate, c. at least a tertiary amine
Data Source
AI summary
The present invention relates to a modified polyisocyanate and use thereof, in particular as a crosslinking component of water-soluble or water-dispersible coatings. The modified polyisocyanate is obtained by a reaction of a system comprising the following components: at least an aminosulfonic acid; at least a polyisocyanate; at least a tertiary amine; and optionally a polyether alcohol containing an ethylene oxide group. The modified polyisocyanate comprises at least an iminooxadiazinedione structure and at least an isocyanurate structure, the weight ratio of the iminooxadiazinedione structure to the isocyanurate structure being 1:300 to 1:5. The amount of sulfonate group of the modified polyisocyanate is 0.75% by weight to 1.1% by weight, based on the amount of the modified polyisocyanate as 100% by weight. The viscosity thereof is 500 mPa·s to 10000 mPa·s, as determined according to DIN EN ISO 3219:1994-10 at a temperature of 23°C and a shear rate of 10 s-1. The coating comprising the modified polyisocyanate of the present invention can be manually stirred well, and the resulting coating layer has high gloss and good transparency.