Ambient-Curable Isocyanate-Free Polyurethane via Segmented Catalyst
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Solution Overview
Problem
Existing isocyanate-free polyurethane compositions require high temperatures for curing, limiting their application in ambient temperature applications, and the separation of catalysts with pigments and fillers leads to poor cure responses due to adsorption and neutralization issues, necessitating a storage-stable, two-component system that can cure at room temperature without induction time.
Innovation Solution
A two-component composition with a polycarbamate component containing pigments, fillers, or extenders and a second component comprising alkanol, polyaldehyde, and catalyst, where the catalyst is included in the second component to prevent adsorption, allowing for room temperature curing and eliminating the need for induction time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the catalyst is included with pigments, fillers or extenders in the first component, then the composition can be stored as a two-component system, but the catalyst adsorbs on the surface of pigments, fillers or extenders and reduces the cure response
Solution Approach 1:
The patent divides the composition into two separate components: the first component contains the polycarbamate with pigments, fillers or extenders, while the second component contains the catalyst separately. This segmentation prevents the catalyst from adsorbing onto pigment surfaces during storage, maintaining catalyst availability and cure response while still enabling a two-component storage system.
Solution Approach 2:
The patent introduces a separate second component as an intermediary container for the catalyst. This intermediary structure allows the catalyst to be protected from direct contact with pigments and fillers during storage, preventing adsorption issues while enabling easy mixing and activation of the curing reaction when the two components are combined.
2Reliability
If the catalyst is kept separate to avoid adsorption, then the cure response is improved, but the composition requires three components instead of two
Solution Approach 1:
The patent merges the catalyst with the polyaldehyde or acetal/hemiacetal of a polyaldehyde into a single second component. This combination allows the catalyst to be kept separate from pigments and fillers (improving cure response) while reducing the total number of components from three to two, simplifying the composition structure.
3Object-affected harmful factors
If known isocyanate-free compositions are used, then health and safety concerns are addressed, but curing requires elevated temperatures above 80°C
Solution Approach 1:
The patent changes the temperature parameter of the curing process by using a specifically selected catalyst in the second component that enables the crosslinking reaction to proceed at ambient temperatures (0°C to less than 80°C) rather than requiring elevated temperatures above 80°C. This parameter change maintains the health and safety benefits of isocyanate-free compositions while expanding their applicability to ambient temperature curing applications.
4Reliability
If polycarbamate and polyaldehyde are mixed, then crosslinking can occur, but a 15 minute induction time is required before use
Solution Approach 1:
The patent eliminates the induction time by performing preliminary action: the catalyst is pre-combined with the polyaldehyde or acetal/hemiacetal in the second component during manufacturing. This preliminary preparation ensures that when the two components are mixed at the point of use, the crosslinking reaction can proceed immediately without requiring a 15-minute induction period, thus eliminating the time loss while maintaining reliable crosslinking.
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 solution provides a storage-stable, ambient temperature-curable polyurethane with improved crosslinking, water resistance, and MEK resistance, enabling applications previously unattainable by prior art, such as in adhesives, coatings, and sealants, with reduced volatile organic compounds and formaldehyde byproducts.
Implementation Method 1
one or more catalyst, such as an organic or inorganic protic acid or Lewis acid thereof having a pKa of less than 5.0... such that the first and second components when combined form a composition that reacts to cure at a temperature of from 0° C. to less than 80° C. to form a crosslinked polyurethane
Implementation Method 2
there is a minimum 15 minute induction time needed to allow alcohol in the mixture to react with the aldehyde to form acetal
Data Source
AI summary
The present invention provides a multicomponent composition that is substantially isocyanate-free and comprises a polycarbamate as a first component having a filler, pigment, extender or matting agent and a second component containing an acidic catalyst an alkanol having one OH group, a polyaldehyde and an acetal or hemiacetal of the polyaldehyde. The compositions are shelf stable and useful as two components and avoid problems caused by combining the catalyst with any filler, pigment, extender or matting agent.