Isocyanate-Terminated Prepolymer Turbidity Control
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Solution Overview
Problem
Existing processes for producing polyisocyanates result in products with excessively high turbidity, limiting their use in optically demanding coating systems and finishes.
Innovation Solution
A process involving a stoichiometric excess of aliphatic or cycloaliphatic diisocyanates and polyols with high OH numbers, mixed with specific power input in the range of 0.5 kW/m3 to 40 kW/m3, to produce isocyanate-terminated prepolymers and subsequently polyisocyanates with isocyanurate and allophanate groups, ensuring turbidity levels of at most 2.0 NTU through controlled urethanization and distillative separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional urethanization reaction conditions are used to produce polyisocyanates, then the reaction can proceed to form higher molecular weight adducts, but the resulting products exhibit excessively high turbidity values that limit their use in optically demanding coating systems
Solution Approach 1:
The patent applies parameter changes by controlling the specific power input during mixing (0.5-40 kW/m³) and managing temperature profiles during the urethanization reaction. These parameter adjustments prevent formation of turbid by-products while maintaining desired polyisocyanate product characteristics, directly resolving the optical quality issue.
Solution Approach 2:
The patent replaces conventional mechanical mixing approaches with a more sophisticated control system that monitors and adjusts mixing intensity and temperature dynamically during the reaction. This substitution allows precise control over reaction conditions to eliminate turbidity without compromising product formation.
2Quantity of substance
If high stoichiometric excess of diisocyanate is used to ensure complete reaction and high isocyanate functionality, then the polyisocyanate can achieve desired functionality ≥4, but the reaction mixture becomes more difficult to control and may produce higher turbidity
Solution Approach 1:
The patent implements feedback control by monitoring reaction conditions (temperature, mixing intensity, conversion) and adjusting process parameters in real-time. This allows maintenance of high isocyanate functionality through controlled excess diisocyanate while preventing turbidity formation through dynamic process adjustment.
Solution Approach 2:
The patent applies dynamics by making the mixing intensity and temperature profiles variable rather than constant. The specific power input is adjusted during the reaction course to optimize both high functionality achievement and turbidity prevention, transforming a static process into a dynamically controlled one.
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 process effectively reduces turbidity to acceptable levels, enabling the production of turbidity-free polyisocyanates suitable for elastic coatings, improving their optical quality and reliability in coating systems.
Implementation Method 1
reacting a reaction mixture containing a stoichiometric excess of at least one aliphatic and/or cycloaliphatic diisocyanate and a polyol composition having an OH number >400
Implementation Method 2
distillatively separating off monomeric diisocyanate from the polyisocyanate obtained in step (2)
Implementation Method 3
the reaction mixture is mixed with a specific power input in the range from 0.5 kW/m3 to 40 kW/m3, based on the total volume of the reaction mixture
Data Source
AI summary
The invention relates to a method for producing isocyanate-terminated, urethane group-containing prepolymers, comprising reacting a reaction mixture that contains a stoichiometric excess of at least one aliphatic and/or cycloaliphatic diisocyanate and a polyol composition having an OH number >400, characterized in that the reaction mixture is mixed with a specific power input of 0.5 kW/m3 to 40 kW/m3, relative to the total volume of the reaction mixture.