Cycloaliphatic Polyisocyanate Emulsion for Low-VOC Coatings
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Solution Overview
Problem
Existing polyisocyanate-based coatings and adhesives face challenges in achieving stable emulsions with fine particle sizes and maintaining properties like gloss, water resistance, and drying speed comparable to those using organic solvents, while also reducing solvent use and ensuring safety from toxic solvents.
Innovation Solution
A mixture comprising cycloaliphatic polyisocyanate, an ether ester type solvent, and a non-reactive hydrophilic additive, which forms an aqueous emulsion that is self-emulsifiable and provides high-gloss, chemically resistant coatings with reduced drying time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If organic solvents are used in polyisocyanate-based coatings, then good gloss and water resistance are achieved, but toxicity and flammability increase
Solution Approach 1:
The patent changes the chemical parameters of the solvent system by using ether ester solvents with specific molecular structures (containing both ether and ester functional groups) instead of traditional organic solvents. This parameter change maintains the solvation capability needed for good gloss and water resistance while fundamentally altering the toxicological and flammability parameters to be non-toxic and non-flammable.
Solution Approach 2:
The patent employs a solvent system that can be easily evaporated and replaced, using volatile ether ester compounds that serve their purpose during application and then dissipate, leaving no harmful residue. This approach allows the use of aggressive solvents during application for good performance, but they are short-lived and leave no harmful impact.
2Object-affected harmful factors
If water-based emulsions are used to reduce solvent content, then toxicity is reduced, but emulsion stability and particle size control become difficult
Solution Approach 1:
The patent introduces specific non-ionic surfactants as intermediary substances that mediate between the hydrophobic polyisocyanate components and the aqueous phase. These surfactants with specific HLB values (10-16) act as intermediaries that stabilize the emulsion by reducing interfacial tension and preventing particle aggregation, thereby achieving good emulsion stability while maintaining the water-based non-toxic formulation.
Solution Approach 2:
The patent carefully controls the particle size parameter of the emulsion by adjusting emulsification conditions, surfactant concentration, and mixing parameters. By optimizing these parameters, the patent achieves fine particle sizes (0.1-10 µm) that provide both stability and good coating performance, resolving the contradiction between water-based formulation and emulsion stability.
3Object-affected harmful factors
If solvent-free solutions are used, then toxicity is minimized, but application viscosity and processing become problematic
Solution Approach 1:
The patent uses ether ester solvents as intermediary substances that provide temporary liquidity during application and then evaporate completely. These solvents act as intermediaries that enable easy application by reducing viscosity during the application process, but they leave no harmful residue as they completely evaporate, maintaining the benefit of minimal toxicity.
Solution Approach 2:
The patent creates a dynamic solvent system where the solvent concentration changes over time - high during application to ensure low viscosity and ease of application, then decreases as evaporation occurs, leading to the final cured coating. This dynamic approach allows the system to be easy to apply when needed while minimizing solvent content in the final product.
4Quantity of substance
If polyisocyanate compositions are emulsified in water, then organic solvent content is reduced, but coating drying time increases
Solution Approach 1:
The patent changes the physical parameters of the water-based emulsion by controlling particle size, solid content, and pH to optimize drying performance. By adjusting these parameters, the patent achieves fast drying times comparable to solvent-based systems while maintaining reduced organic solvent content, as the fine particle size and optimized composition facilitate rapid water evaporation and coating formation.
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 and adhesives with improved gloss, water resistance, and drying speed, while minimizing solvent use and ensuring safety by using non-toxic, non-flammable solvents, thus addressing the stability and performance issues of previous technologies.
Implementation Method 1
a mixture based on polyisocyanate(s), characterized in that it comprises: at least one cycloaliphatic polyisocyanate; at least one solvent comprising an ester function and an ether function
Implementation Method 2
an aqueous emulsion which is characterized in that it is obtained by emulsifying in water the mixture as described above
Data Source
AI summary
The mixture of the invention comprises at least one cycloaliphatic polyisocyanate and at least one solvent comprising an ester function and an ether function. An aqueous emulsion can be obtained from this mixture which also comprises a compound bearing a function with a mobile hydrogen, selected from primary or secondary hydroxyl functions, phenol functions, primary and/or secondary amino functions, carboxylic functions and a thiol function or a compound containing precursor functions capable of freeing hydroxyl functions. The emulsion can be used for the manufacture of coatings on a substrate of cement, of wood or of leather especially, and also for the manufacture of adhesives.