Extrudable Polyurethane Adhesive With Latent Isocyanate Groups
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Reactive polyurethane adhesives require protection from ambient moisture, making them inconvenient to handle, while non-reactive polyurethane adhesives lack high thermal stability due to limited use temperature range.
Innovation Solution
A polyurethane composition with hydroxyl groups and latent isocyanate groups in the form of uretdione groups, where the ratio of latent isocyanate groups to hydroxyl groups is greater than 1.2:1, allowing for moisture curing and high thermal stability without premature curing during processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If reactive polyurethane adhesives are used to achieve high thermal stability through moisture curing, then thermal stability is improved, but handling convenience deteriorates due to the need to protect isocyanate end groups from ambient moisture
Solution Approach 1:
The patent changes the chemical state of isocyanate groups from active (reactive) to latent (blocked) form. The polyurethane composition contains latent isocyanate groups that can be activated by heating to a specific temperature range, transforming the material from a stable, easy-to-handle state to a reactive state only when needed for bonding. This parameter change (chemical reactivity) allows the adhesive to maintain stability during handling and then cure when activated.
Solution Approach 2:
The patent incorporates latent isocyanate groups into the polyurethane structure in advance, preparing the material to undergo moisture curing only when activated by heat. This preliminary preparation allows the adhesive to be stored and handled like a non-reactive material, but with the latent capability to crosslink and achieve high thermal stability when the activation temperature is reached.
2Ease of operation
If non-reactive polyurethane adhesives are used to achieve ease of handling, then handling convenience is improved, but thermal stability deteriorates due to limited use temperature range
Solution Approach 1:
The patent introduces latent isocyanate groups that remain dormant at ambient temperatures, allowing easy handling similar to non-reactive adhesives. When heated to the activation temperature range, these latent groups convert to active isocyanates that react with moisture to form crosslinked structures, dramatically expanding the use temperature range and thermal stability.
Solution Approach 2:
The patent creates a dynamic system where the polyurethane's reactivity changes with temperature. At low temperatures, the material behaves like a non-reactive adhesive with good handling properties. At activation temperatures, the latent isocyanate groups become active, enabling moisture curing and crosslinking. This dynamic behavior allows the same material to provide both ease of handling and high thermal stability.
3Temperature
If reactive polyurethane adhesives are used to achieve high thermal stability, then thermal stability is improved, but processing complexity increases due to the need to protect isocyanate groups during storage and processing
Solution Approach 1:
The patent changes the isocyanate groups from permanently reactive to temperature-dependent latent form. This parameter change eliminates the need for complex protective measures during storage and processing, as the material remains stable at ambient temperatures. The complexity is reduced because the material only becomes reactive when heated to the specific activation temperature range, simplifying handling and processing procedures.
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 provides the convenience of non-reactive polyurethanes with the high performance of reactive polyurethanes, remaining flowable during application and achieving strong covalent crosslinks upon moisture absorption, enhancing thermal stability.
Implementation Method 1
After application to the final substrates, ambient moisture reacts with the isocyanate end groups, which leads to crosslinking of the adhesive and relatively high thermal stability
Implementation Method 2
The extrudable article can be heated to cause the uretdione groups to substantially revert to isocyanate groups
Data Source
AI summary
The present disclosure provides an extrudable article and a composition, each including at least one polyurethane including hydroxyl groups and latent isocyanate groups in the form of uretdione groups. The hydroxyl groups are present on a first polyurethane and the latent isocyanate groups are present on either the first polyurethane or a second polyurethane and a ratio of the latent isocyanate groups to the hydroxyl groups is greater than 1.2:1. A method of making the extrudable article is provided including reacting in an extruder a polymerizable composition including a uretdione-containing material including a reaction product of a diisocyanate reacted with itself, a hydroxyl-containing compound, and an isocyanate-containing compound. A method of making a core-sheath filament is provided including forming a core composition of the at least one polyurethane and wrapping a sheath composition including an ethylene copolymer or a polyolefin around the core composition. Further, methods of printing a composition are provided including heating and mixing the extrudable article, such as in an extruder, to form a molten composition, then dispensing the molten composition through a nozzle onto a substrate.