Polyisocyanate Flocculation Stability via Additive Stabilization
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Solution Overview
Problem
Existing methods for stabilizing polyisocyanates against flocculation in solvents are inefficient, requiring high stoichiometric amounts of water scavengers that reduce NCO values and lead to side effects like reduced paint properties and instability due to high reactivity and poor solubility.
Innovation Solution
The use of additives such as organic acids with a pKa value less than 4.2, phosphites, and phosphonites to reduce flocculation and precipitate formation in polyisocyanate mixtures, providing antiflocculating effects without significant water scavenging or reactivity issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If water scavengers are used to prevent flocculation of polyisocyanates in solvents, then storage stability is improved, but NCO values are reduced due to dilution and side reactions
Solution Approach 1:
The patent removes water scavengers entirely from the polyisocyanate formulation, extracting the problematic component that caused both flocculation and NCO value reduction. Instead, the invention uses a different approach by controlling water content through careful process control and using alternative stabilization methods that do not consume NCO groups.
Solution Approach 2:
The patent changes the parameter of water content control from using chemical scavengers to using process control parameters. By carefully controlling the water content to be less than 50 ppm through distillation and other purification methods, the invention achieves storage stability without the need for water scavengers that would reduce NCO values.
2Stability of the object's composition
If high amounts of water scavengers are used to stabilize polyisocyanates, then flocculation is prevented, but paint properties deteriorate due to reduced NCO content
Solution Approach 1:
The patent uses small amounts of acceptable solids (such as silica or titanium dioxide) that can be added to the polyisocyanate formulation to provide flocculation stability without consuming NCO groups. These inexpensive additives serve as a short-term solution to prevent flocculation while maintaining the reactive NCO content necessary for paint performance.
Solution Approach 2:
The patent changes the approach from chemical stabilization (water scavengers) to physical stabilization (acceptable solids and process control). By controlling water content to less than 50 ppm and using inert solids, the invention maintains both flocculation stability and paint properties without the trade-off present in conventional approaches.
3Quantity of substance
If reactive water scavengers like para-toluenesulfonyl isocyanate are used, then water is captured effectively, but side reactions occur and pressure builds up in storage vessels
Solution Approach 1:
The patent converts the harmful effect of water (which causes flocculation) into a beneficial control parameter by carefully managing water content to be less than 50 ppm. Rather than trying to scavenge water chemically (which causes side reactions), the invention uses controlled low water content combined with acceptable solids to achieve stability, thereby eliminating the harmful side reactions and pressure buildup.
Solution Approach 2:
The patent creates an inert environment by maintaining extremely low water content (less than 50 ppm) through careful process control and purification. This inert-like condition prevents water from causing flocculation or reacting with isocyanate groups, eliminating the need for reactive water scavengers and their associated side reactions and pressure buildup.
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
These additives significantly enhance the storage stability of polyisocyanates by preventing flocculation and precipitate formation, maintaining paint properties and extending storage life without the drawbacks of high water scavenger usage.
Implementation Method 1
addition of from 0.01 to 1000 ppm by weight of an additive selected from the group consisting of a1) organic acids with a pKs value of less than 4.2
Implementation Method 2
additives such as organic acids with a pKa value less than 4.2, phosphites, and phosphonites to reduce flocculation and precipitate formation
Data Source
AI summary
The invention relates to a novel method for producing polyisocyanates, which are flocculation-stable in solvents and which have isocyanurate groups, from (cyclo)aliphatic diisocyanates.