Low-Monomer Polyurethane Foam via Molecular Weight Control
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Solution Overview
Problem
Conventional low-monomer polyurethane (PU) foams face challenges with high viscosity, requiring solvents or plasticizers, which are harmful, and lack sufficient mechanical strength due to low isocyanate content, limiting their processing and performance in applications like construction sealing and insulating.
Innovation Solution
A crosslinkable foamable composition with a low content of monomeric isocyanates, comprising 10-90% polyester diols reacted with excess diisocyanates and 90-10% polyether diols, along with additives, blowing agents, and specific molecular weight constraints, to achieve low viscosity and mechanical strength without solvents or plasticizers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If monomeric diisocyanate content is reduced to meet occupational safety standards, then harmful emissions are decreased, but viscosity increases and mechanical strength decreases
Solution Approach 1:
The patent changes the molecular weight parameter of the polyol component to below 5000 g/mol, which fundamentally alters the viscosity-strength relationship. This parameter change allows low-monomer formulations to maintain both low viscosity and high mechanical strength, resolving the contradiction between safety standards and performance requirements.
Solution Approach 2:
The patent creates a composite foam structure by combining low-monomer prepolymers with specific polyols of controlled molecular weight. This composite approach enables the foam to achieve mechanical properties comparable to high-monomer foams while maintaining low monomer content for occupational safety.
2Object-affected harmful factors
If monomeric diisocyanate content is reduced, then occupational safety is improved, but processing ease deteriorates due to high viscosity
Solution Approach 1:
By changing the molecular weight parameter of the polyol to below 5000 g/mol, the patent achieves low viscosity in low-monomer formulations. This parameter change directly improves processing ease and application properties while maintaining monomer content below occupational safety thresholds.
3Object-affected harmful factors
If isocyanate content is reduced for safety reasons, then harmful emissions are decreased, but foam expansion and fillability worsen
Solution Approach 1:
The patent utilizes parameter changes in polyol molecular weight to maintain low viscosity in low-monomer systems. This ensures sufficient foam expansion and joint fillability while keeping isocyanate emissions below harmful thresholds, resolving the contradiction between safety and performance.
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 composition allows for the production of foam materials with mechanical properties comparable to high-monomer PU foams, while meeting occupational safety standards by reducing monomeric isocyanate content and enhancing fire resistance and processing ease.
Implementation Method 1
The one-component PUR foam becomes solid through the crosslinking reactions with moisture.
Implementation Method 2
c) at least one blowing agent
Data Source
AI summary
The invention relates to a cross-linkable foamable composition having a low content of monomer isocyanates, comprising a) 10 to 90% by weight of a prepolymer made of polyester dioles converted using an excess of diisocyanates, b) 90 to 10% by weight of a component based on polyether polyols comprising either at least one Si(OR)3 group or at least one NCO group, c) 0.1 to 30% by weight of additive, d) and at least one propellant, wherein the polyester diole and the polyether diole comprise a molar mass (MN) of less than 5000 g/mol, and the mixture of a and b has a content of monomer diisocyanates of less than 1% by weight.