Polyurethane Catalyst Complexes for Controlled Crosslinking
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Solution Overview
Problem
Existing polyurethane crosslinking reactions face challenges with catalysts that either have rapid reactivity, leading to quick curing but long processing times, or slow reactivity, resulting in prolonged crosslinking times and delayed substrate fixation.
Innovation Solution
Development of catalyst compositions containing metal-based catalysts, such as Sn, Ti, Zn, Pb, Bi, Fe, or Ni, combined with retardant substances like cyclic α-hydroxy ketones and triphenols, which exhibit reduced reactivity initially but accelerate crosslinking after an induction period, suitable for both 1K and 2K systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If rapid-reacting catalysts are used, then crosslinking speed is improved, but processing time increases
Solution Approach 1:
The patent applies preliminary action by incorporating a blocking agent that temporarily deactivates the catalyst during storage and processing. This blocking agent is removed or decomposes after application, allowing the catalyst to become active and accelerate crosslinking at the desired moment. This resolves the contradiction by enabling fast crosslinking only when needed, while maintaining stability during processing.
Solution Approach 2:
The patent changes the activation state parameter of the catalyst through the use of a blocking agent. The catalyst transitions from an inactive blocked state during storage to an active state after application. This parameter change allows the system to have fast crosslinking speed when required while maintaining long stability during processing, effectively resolving the time contradiction.
2Loss of time
If slow-reacting catalysts are used, then processing time is reduced, but crosslinking completion time increases
Solution Approach 1:
The blocking agent is applied in advance to prevent premature catalyst activation during storage and processing. After the composition is applied to the substrate, the blocking agent is removed or decomposes, allowing the catalyst to become active and complete crosslinking rapidly. This ensures both long processing stability and fast crosslinking completion.
Solution Approach 2:
The catalyst activity follows a periodic pattern: inactive during storage and processing (blocked state), then becomes active after application to drive rapid crosslinking. This periodic activation resolves the contradiction by having the catalyst dormant when processing time matters and active when crosslinking completion is needed.
3Productivity
If catalyst activity is increased, then crosslinking reactivity is improved, but substrate fixation time increases
Solution Approach 1:
The blocking agent prevents catalyst activation during substrate processing and positioning. Once the substrate is properly fixed and positioned, the blocking agent decomposes or is removed, allowing high catalyst activity to drive rapid crosslinking and complete substrate fixation. This ensures substrates can be handled and positioned without premature curing, then fixed rapidly afterward.
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
This approach allows for a controlled induction period, enabling longer processing times without compromising the rapid completion of crosslinking, ensuring stable compositions and efficient substrate fixation.
Implementation Method 1
polyurethane crosslinking reactions as a reaction of isocyanate with water or as a reaction of isocyanate with OH components are accelerated by metal or amine catalysts
Implementation Method 2
cyclic α-hydroxy ketones and/or triphenols with three adjacent OH groups... exhibit reduced reactivity initially but accelerate crosslinking after an induction period
Data Source
AI summary
The invention relates to a crosslinkable composition containing reactive polymers selected from among (i) prepolymers having reactive NCO groups or (ii) polymers which have reactive silane groups, optionally further additives and at least one metal-based catalyst, wherein the composition contains up to 10% by weight of retarding substance selected from among cyclic a-hydroxy ketones and/or triphenols having three adjacent OH groups.