Colour-Stable Polyisocyanates Using Dialkyl Phosphite Stabilizers
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Solution Overview
Problem
Current polyisocyanate compositions face stabilization challenges when mixed with catalysts and stored, particularly due to the use of phosphites which have unpleasant odors, toxicity issues, and moisture sensitivity, leading to health and occupational hygiene concerns, and insufficient color stability.
Innovation Solution
The development of polyisocyanate compositions that include at least one polyisocyanate, a catalyst for isocyanate group reactions, a Brønsted acid with a pKa value less than 4, such as dialkyl phosphates, arylsulfonic acids, or phosphonic acid dioctyl esters, and sterically hindered phenols, ensuring color stability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If phosphites (especially trialkyl phosphites) are used as stabilizers in polyisocyanate compositions, then color stability during storage is improved, but health and occupational hygiene problems arise due to unpleasant odor, toxicity, and corrosiveness
Solution Approach 1:
The patent changes the chemical structure parameter of the phosphite stabilizer from trialkyl phosphites to dialkyl phosphites with specific alkyl groups (isobutyl, sec-butyl, tert-butyl). This structural modification reduces the harmful properties (odor, toxicity) while maintaining the stabilizing function. The specific parameter change is in the alkyl group substitution pattern on the phosphite molecule.
Solution Approach 2:
The patent employs stabilizers that are effective at very low concentrations (1-100 ppm), allowing the use of less hazardous substances. The dialkyl phosphites function efficiently in small amounts, reducing the need for large quantities of potentially harmful stabilizers.
2Reliability
If trialkyl phosphites are used as stabilizers, then antioxidant effect is achieved, but moisture sensitivity and processing problems occur
Solution Approach 1:
The patent modifies the moisture sensitivity parameter by changing from trialkyl to dialkyl phosphite structure. The specific dialkyl substitution pattern (with bulky isobutyl, sec-butyl, or tert-butyl groups) reduces water affinity and hydrolysis tendency, thereby decreasing moisture sensitivity while preserving antioxidant properties.
3Speed
If catalysts are added to polyisocyanate compositions to accelerate reaction, then reaction speed between isocyanate groups and reactive groups is improved, but color drift during storage increases
Solution Approach 1:
The patent introduces dialkyl phosphites as intermediary substances that mediate between the catalyst and the polyisocyanate system. These phosphites act as stabilizing intermediaries that prevent direct harmful interactions between catalysts and polyisocyanates during storage, while allowing the catalyst to function properly during the actual reaction process.
Solution Approach 2:
The dialkyl phosphite stabilizers provide beforehand cushioning by being present in the composition prior to use. They preemptively protect the polyisocyanate-catalyst system from degradation and color drift during storage, creating a stable reservoir that maintains functionality until the reaction is needed.
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 proposed compositions achieve long-term color stability and safety by using non-toxic, odorless stabilizers, maintaining effectiveness regardless of the monomeric isocyanate origin, and are suitable for use in polyurethane paints.
Implementation Method 1
The polyisocyanate compositions contain at least one Brønsted acid with a pKa value of less than 4, such as dialkyl phosphates, arylsulfonic acids, or phosphonic acid dioctyl esters
Implementation Method 2
The polyisocyanate compositions contain at least one sterically hindered phenol
Implementation Method 3
at least one compound capable of accelerating the reaction of isocyanate groups with isocyanate-reactive groups
Data Source
AI summary
The invention relates to a novel method for producing polyisocyanates of (cyclo)aliphatic diisocyanates, which are colour-stable in solvents and which comprise isocyanurate groups.