Polyisocyanate Mixtures for Fast-Drying Coatings
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current polyisocyanates used in 2-component polyurethane coatings, such as those based on 1,6-diisocyanatohexane (HDI) and HDI trimers, suffer from slow drying speed and low final hardness, even when used in combination with cycloaliphatic diisocyanates like isophorone diisocyanate (IPDI), which also require high temperatures for complete chemical crosslinking, resulting in coatings with lower solvent and chemical resistance.
Innovation Solution
A process for producing polyisocyanate mixtures containing cycloaliphatic structural elements with linear-aliphatically bonded free isocyanate groups, combining a polyisocyanate component with an average functionality of 2.0 to 5.0 and a hydroxyurethane component based on cycloaliphatic di- and/or polyisocyanates, to create a crosslinking system that allows for fast drying and high hardness at low temperatures while maintaining chemical and solvent resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If polyisocyanates based on linear aliphatic diisocyanates (HDI) are used, then low viscosity and high elasticity are achieved, but drying speed is slow and final hardness is low
Solution Approach 1:
The invention uses composite polyisocyanate systems combining linear aliphatic polyisocyanates (for low viscosity and elasticity) with cycloaliphatic polyisocyanates (for fast drying and high hardness), creating a material that exhibits properties superior to individual components
2Productivity
If high-functionality HDI trimers are used, then drying speed is increased, but final hardness remains low
Solution Approach 1:
The patent combines HDI trimers (providing fast drying through high functionality) with cycloaliphatic polyisocyanates (providing high hardness through their molecular structure), achieving both rapid drying and high final hardness that neither component can achieve alone
3Strength
If cycloaliphatic polyisocyanates (IPDI) are used, then high hardness and fast physical drying are achieved, but chemical crosslinking requires high temperatures and solvent resistance decreases
Solution Approach 1:
The invention blends cycloaliphatic polyisocyanates (providing high hardness and fast physical drying) with linear aliphatic polyisocyanates (enabling complete chemical crosslinking at lower temperatures), resulting in a system that achieves high hardness without requiring high crosslinking temperatures and maintains excellent solvent resistance
4Productivity
If HDI and cycloaliphatic polyisocyanates are combined, then drying speed is accelerated, but solvent and chemical resistance decreases
Solution Approach 1:
The patent optimizes the composition and molecular weight distribution of the composite polyisocyanate system to maintain high drying speed from the cycloaliphatic component while ensuring sufficient linear aliphatic content and functionality to achieve complete chemical crosslinking, thereby preserving excellent solvent and chemical resistance
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 resulting polyisocyanate mixtures enable the formulation of fast-drying, hard, and chemically resistant coatings at room temperature or low temperatures, surpassing the limitations of traditional systems by combining rapid drying with high final hardness and improved resistance to solvents and chemicals.
Implementation Method 1
due to the lower reactivity of their isocyanate groups, cycloaliphatic polyisocyanates require temperatures of 100°C or higher for complete chemical crosslinking
Implementation Method 2
solvent-free cycloaliphatic polyisocyanates are highly viscous to solid products that lead to rapid physical drying of a coating batch
Data Source
AI summary
The invention relates to novel polyisocyanate mixtures that contain alicyclic structural elements and exclusively comprise linear-aliphatically bonded free isocyanate groups, a method for the production thereof, and the use thereof as a starting component for producing polyurethane plastics, especially as a cross-linking component in polyurethane lacquers and coatings.