HDI Polyester Prepolymers for Low Viscosity and Crystallization Stability
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Solution Overview
Problem
Current solvent-free 2K polyurethane or polyurea coatings face limitations in achieving sufficient elasticity and weather resistance, particularly due to the high viscosity and crystallization tendencies of existing HDI polyester prepolymers, which hinder their use in outdoor applications under varying environmental conditions.
Innovation Solution
Development of isocyanate-functional HDI polyester prepolymers with specific molecular structures, combining polycaprolactone polyesters and polyester polyols derived from aliphatic dicarboxylic acids and branched aliphatic diols, which maintain low viscosity and prevent crystallization, ensuring stability and quick curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If polycaprolactone polyester prepolymers from HDI are used, then viscosity is low, but crystallization tendency is high leading to clouding and solidification
Solution Approach 1:
The patent combines polycaprolactone polyester and polyester from aliphatic dicarboxylic acids in a specific ratio (30-70 wt% polycaprolactone polyester) to create a composite prepolymer system. This composite approach allows the low viscosity of polycaprolactone polyester to be maintained while the aliphatic dicarboxylic acid component suppresses crystallization, resolving the contradiction between low viscosity and crystallization stability
Solution Approach 2:
The patent modifies the chemical composition parameters of the polyester components, specifically using aliphatic dicarboxylic acids with 4-12 carbon atoms and controlling the molecular weight and hydroxyl functionality. These parameter changes in the molecular structure prevent crystallization while maintaining low viscosity, solving the contradiction between viscosity and crystallization tendency
2Reliability
If polyester polyols from linear dicarboxylic acids are used, then weather resistance is good, but viscosity is significantly higher
Solution Approach 1:
The patent optimizes the molecular weight parameters of the polyester polyols (300-3000 g/mol) and controls the hydroxyl functionality (1.9-2.3) to achieve low viscosity. By adjusting these physical parameters while maintaining aliphatic structure for weather resistance, the contradiction between weather resistance and low viscosity is resolved
Solution Approach 2:
The patent creates a composite polyester system combining polycaprolactone polyester with polyester from aliphatic dicarboxylic acids. This composite structure provides both the weather resistance of aliphatic polyesters and the low viscosity needed for practical application, overcoming the high viscosity limitation of conventional linear polyester polyols
3Force
If oligomeric paint polyisocyanates are used, then viscosity is low and weather resistance is high, but elasticity is insufficient for crack-bridging coatings
Solution Approach 1:
The patent uses composite polyester polyols combining polycaprolactone segments with aliphatic dicarboxylic acid chains. This composite molecular structure provides both flexibility for elasticity and low viscosity, enabling crack-bridging capability while maintaining ease of application, thus resolving the contradiction between viscosity and elasticity
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 new prepolymers exhibit extremely low viscosities, stability against crystallization, and excellent weather resistance, enabling the production of elastic, light-resistant coatings suitable for outdoor use without the need for solvents.
Implementation Method 1
polycaprolactone polyester prepolymers from HDI show comparatively low viscosities but also a strong tendency to crystallize, which leads to rapid clouding, especially in cool ambient conditions and lead to solidification
Implementation Method 2
due to their poor weather resistance - a result of oxidative polyether chain degradation
Data Source
AI summary
The invention relates to a crystallization stable polyester prepolymers for producing HDI- and PDI-based, solvent-free two component (2K)-polyurethane- and/or polyurea coating agents.