Polyurethane Adhesive Latent Hardener Plasticizer Migration
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Solution Overview
Problem
Polyurethane compositions used as adhesives, sealants, or coatings face issues with premature curing and plasticizer migration, leading to bubble formation, reduced storage stability, and damage to substrates due to volatile emissions and odor, especially when applied to sensitive materials like wood, plastics, and porous surfaces.
Innovation Solution
A composition containing polyisocyanate and/or polyurethane polymer with isocyanate groups and a latent hardener with specific aldimino groups, which minimizes plasticizer migration, maintains storage stability, and cures without bubble formation or volatile emissions, ensuring compatibility and stability under various environmental conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If latent hardeners with conventional blocking agents (aldehydes or ketones) are used to prevent bubble formation during curing, then bubble formation is reduced, but premature crosslinking occurs and storage stability is reduced
Solution Approach 1:
The patent changes the chemical structure of the blocking agent by using aldehydes with long-chain hydrophobic substituents (C12-C26 carbon atoms) instead of conventional small aldehydes or ketones. This parameter change in molecular size and hydrophobicity prevents premature crosslinking while maintaining bubble formation control during curing.
Solution Approach 2:
The blocking agent serves a temporary function during storage and application, then is consumed during curing to release the amino groups. The long-chain aldehyde structure ensures it remains stable during storage but reacts appropriately during curing to prevent bubbles.
2Reliability
If conventional latent hardeners are used to control curing, then bubble formation is reduced, but disruptive emissions of volatile odorous aldehydes or ketones occur during curing
Solution Approach 1:
The patent converts the potentially harmful volatile emissions into a beneficial non-volatile, odorless system by using long-chain hydrophobic aldehydes. These large molecules have negligible vapor pressure, eliminating odor issues while still serving as effective blocking agents that control curing and prevent bubble formation.
Solution Approach 2:
By changing the physical parameters of the blocking agent (increasing molecular weight and hydrophobicity through long-chain substituents), the patent transforms the emission characteristics from volatile and odorous to non-volatile and odorless, while maintaining the chemical functionality for curing control.
3Strength
If polyurethane compositions are applied to porous materials or plastics, then adhesion and sealing are achieved, but plasticizer migration causes bleeding, discoloration, staining, or damage to substrates
Solution Approach 1:
The patent converts the problematic migratable blocking agents into non-migratable long-chain aldehydes. These large hydrophobic molecules are incompatible with plasticizer migration pathways and do not extract plasticizers from the composition, thereby eliminating bleeding, discoloration, and substrate damage while maintaining adhesion.
Solution Approach 2:
The blocking agent with long-chain hydrophobic substituents exhibits localized stability within the polyurethane matrix, remaining fixed in the cured composition rather than migrating to substrates or topcoats. This local stability prevents plasticizer migration issues while maintaining bulk adhesion properties.
4Object-generated harmful factors
If high molecular weight blocking agents are used to reduce emissions, then odor is reduced, but plasticizer migration tendency increases due to high equivalent weight and high amount of released aldehyde
Solution Approach 1:
The patent optimizes the chain length of the hydrophobic substituent to C12-C26 carbon atoms, achieving a balance where the blocking agent is sufficiently large to be non-volatile and odorless, yet the amount released during curing is minimal and non-migratable, preventing plasticizer migration while maintaining odor reduction.
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 effectively prevents plasticizer migration, extends the open time, and ensures stable curing without disrupting the substrate or top layer, maintaining the integrity and appearance of materials even under high humidity and temperature conditions.
Implementation Method 1
bind moisture through hydrolysis and thereby release amino groups, which react with the isocyanate groups without forming carbon dioxide
Implementation Method 2
crosslink through the reaction of isocyanate groups with moisture or water and thereby harden to form elastomers
Data Source
AI summary
The present invention relates to the use of a composition - comprising at least one polyisocyanate and/or at least one isocyanate-group-containing polyurethane polymer and at least one latent hardener having aldimino group(s) of formula (I) - as an elastic adhesive, sealant or coating, which is applied on at least one plasticiser migration sensitive substrate and/or is provided with at least one covering layer and a composite obtained therefrom. The use is characterised in that porous material or stress-crack-forming plastics can be used without restriction as substrates and very different materials can be used without restriction as covering layers, without the occurrence of damage associated with plasticiser migration from the composition, such as bleeding, discolouring, spotting, softening, swelling or detachment.