Crosslinkable Polyurethane Composition Catalyst Control
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Solution Overview
Problem
Current two-pack polyurethane coatings face challenges in achieving a balance between pot-life, working time, and drying time while requiring high early hardness, durability, and low VOC content, often using toxic or volatile materials that are not compliant with modern regulations.
Innovation Solution
A crosslinkable composition comprising a polyol with free hydroxyl groups, a polyisocyanate crosslinker, a catalyst, and a tertiary acid, optionally with a complexing agent containing a -SH group, which improves the pot-life-drying ratio, early hardness, and working time, and is formulated to be non-aqueous with low VOC content, using materials that are compliant with environmental regulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the cure-speed is increased to increase productivity, then drying time is reduced, but working time and pot life are decreased
Solution Approach 1:
The patent uses a specific catalyst system with defined metal content (0.01-5 wt%) and acidity (0.01-5 mmol/g) to precisely control the reaction kinetics. By adjusting catalyst parameters, the invention achieves accelerated curing while maintaining adequate working time, resolving the contradiction between productivity and working time.
Solution Approach 2:
The invention employs a composite catalyst system combining metal compounds with specific organic acids or complexing agents. This composite approach allows synergistic effects that enable fast curing without sacrificing pot life, as the different components work together to optimize both drying speed and working time.
2Productivity
If high early hardness is required to enable earlier handling, then productivity increases, but the composition may require toxic or volatile materials that reduce compliance with regulations
Solution Approach 1:
The patent specifies precise parameter ranges for catalyst metal content (0.01-5 wt%) and acidity (0.01-5 mmol/g) to achieve high early hardness through controlled chemical reaction rather than volatile promoters. This parameter optimization enables regulation-compliant formulations with excellent early handling properties.
Solution Approach 2:
The invention replaces persistent toxic VOCs with a functional catalyst system that achieves its purpose during the curing process and then becomes part of the inert crosslinked network. The catalyst components serve their function and are effectively 'disposed of' into the cured coating structure, eliminating ongoing harmful emissions while maintaining high early hardness.
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 a balanced pot-life-drying ratio, high early hardness, and excellent mechanical and chemical resistance, while being formulated without highly toxic materials and low VOC content, ensuring compliance with current and future environmental regulations.
Implementation Method 1
a catalyst catalysing the reaction between —OH groups of said polyol and —NCO groups of said crosslinker
Implementation Method 2
a complexing agent containing at least one —SH group
Data Source
AI summary
The present invention relates to a crosslinkable composition comprising a polyol, a polyisocyanate crosslinker, a catalyst for catalysing the reaction between —OH groups of said polyol and —NCO groups of said crosslinker, a tertiary acid of formula RR′R″CCOOH (I), wherein each R, R′ and R″ group, independently, is an alkyl, alkenyl, aryl or aralkyl group containing at least one carbon atom, with the proviso that two or three of the R, R′ and R″ groups can be linked to form a ring structure and wherein the R, R′ and/or R″ groups can be substituted, and optionally, a complexing agent containing at least one —SH group, as well as its use for making coatings having improved application properties.