Blocked Polyisocyanate Catalyst Composition for Low-Temperature Curing
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Solution Overview
Problem
Existing catalysts for dissociating blocked polyisocyanate, such as quaternary ammonium salts, cause color change over time, limiting their use in coating materials due to yellowing issues.
Innovation Solution
A catalyst composition comprising a quaternary ammonium salt and a carbonate diester compound, with specific ratios and components, is used to dissociate the blocking agent from blocked polyisocyanate, providing low-temperature curability while minimizing color change.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a quaternary ammonium salt is used as a deblocking catalyst, then low-temperature curability is improved, but color change (yellowing) occurs over time
Solution Approach 1:
The patent uses a quaternary ammonium hydroxide compound as an intermediary substance that mediates between the blocked polyisocyanate and the main agent. This specific intermediary (quaternary ammonium hydroxide) provides catalytic activity for deblocking at low temperatures while being stable against color change, resolving the contradiction between low-temperature curability and color stability.
Solution Approach 2:
The patent changes the parameter of the catalyst from general quaternary ammonium salts to specifically quaternary ammonium hydroxide compounds with defined chemical structures (formula 1). This parameter change in the catalyst's chemical nature and structure enables both low-temperature deblocking activity and resistance to color change over time.
2Duration of action of moving object
If blocked polyisocyanate is used as a curing agent, then pot life is extended, but low-temperature curability is reduced
Solution Approach 1:
The quaternary ammonium hydroxide compound acts as an intermediary that enables the blocked polyisocyanate to release its blocking agent at low temperatures. This intermediary facilitates the deblocking reaction that would otherwise require high temperatures, thus maintaining both extended pot life and low-temperature curability.
3Ease of operation
If polyisocyanate and polyol are mixed in advance, then workability is improved, but pot life is shortened due to rapid curing
Solution Approach 1:
The patent applies preliminary action by pre-mixing the blocked polyisocyanate and main agent before coating. The blocking agent prevents premature reaction during mixing and storage, allowing the mixture to be prepared in advance. Upon heating or adding the quaternary ammonium hydroxide catalyst, the blocking agent dissociates and curing proceeds, providing both improved workability and controlled pot life.
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 catalyst composition effectively imparts low-temperature curability to coating materials, reducing color change and coloration of the coating film, enhancing workability and stability.
Implementation Method 1
As a catalyst for dissociating a blocking agent from a blocked polyisocyanate (a deblocking catalyst), for example, a quaternary ammonium salt is known
Implementation Method 2
it has been surprisingly found that the color change of a quaternary ammonium salt over time is suppressed in a mixture of the quaternary ammonium salt and a carbonate diester compound
Data Source
AI summary
A catalyst composition used for dissociating a blocking agent from a blocked polyisocyanate, containing a quaternary ammonium salt and a carbonate diester compound.