Polyisocyanate Composition for Stable Polyurethane Foams
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Solution Overview
Problem
Existing polyurethane formulations for aerosol foams and adhesives face challenges with high viscosities and poor storage stability due to high monomeric isocyanate content, leading to usability issues and safety concerns from respirable isocyanates.
Innovation Solution
A process involving a mixture of diphenylmethane diisocyanate and polyphenylene polymethylene polyisocyanates with specific composition and purification to reduce uretonimine and monomeric isocyanate content, resulting in polyisocyanates with improved storage stability and processing properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If monomeric isocyanates are removed by distillation to reduce respirable isocyanates, then safety is improved, but storage stability deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters by controlling the core structure distribution (2-core MDI ≤2%, 3-core MDI 25-65%, 4-core MDI 5-45%, >5-core MDI 1-40%) and functionality (2.2-5.2) of polyphenylene polymethylene polyisocyanates. This parameter optimization achieves both low monomeric isocyanate content (<0.5% by weight) and improved storage stability, resolving the contradiction between safety and reliability
Solution Approach 2:
The patent uses composite polyisocyanate formulations combining different core structures (2-core, 3-core, 4-core, and >5-core MDI) in specific proportions. This composite approach creates a synergistic effect where the mixture maintains stability while reducing harmful monomeric isocyanates, addressing both safety and storage stability requirements
2Object-affected harmful factors
If polyisocyanates with reduced monomer content are used, then safety is improved, but viscosity increases
Solution Approach 1:
The patent optimizes the functionality parameter (average functionality 2.2-5.2) and core structure distribution of polyisocyanates to achieve the right balance. By controlling these parameters, the formulation reduces monomeric isocyanate content while maintaining viscosity at acceptable levels for processing, resolving the contradiction between safety and ease of operation
3Productivity
If polyisocyanates with high functionality are used, then productivity is improved, but manufacturing complexity increases
Solution Approach 1:
The patent defines specific parameter ranges for functionality (2.2-5.2) and core structure distribution to optimize crosslinking efficiency. By establishing these parameter specifications, the patent achieves high productivity through efficient crosslinking while managing manufacturing complexity through clear compositional guidelines
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 produces polyisocyanates with reduced viscosity and enhanced storage stability, ensuring safer and more effective use in one- and two-component polyurethane systems, including aerosol foams and rigid foams, with improved processing and storage characteristics.
Implementation Method 1
reacting polyisocyanates a) with compounds having at least two hydrogen atoms reactive with isocyanate groups b)
Implementation Method 2
removing the unreacted monomeric isocyanates after the reaction, for example by distillation
Data Source
AI summary
The invention provides a process for preparing polyurethanes by reacting polyisocyanates a) with compounds having at least two hydrogen atoms reactive with isocyanate groups b), characterized in that the polyisocyanate a) used is at least one polyisocyanate ai) with a mean functionality of greater than 2, a content of diisocyanates of not more than 2% by weight and a content of uretonimines of not more than 4% by weight, based in each case on the weight of the polyisocyanate ai).