Blocked Polyisocyanate Composition for Low-Temperature Curing
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Solution Overview
Problem
There is a need for a blocked polyisocyanate composition that cures at a temperature lower than 90°C, offering good storage stability and low-temperature curability, as conventional compositions require high baking temperatures and are not suitable for water-based coatings due to reactivity with water.
Innovation Solution
A blocked polyisocyanate composition containing a polyisocyanate derived from aliphatic or alicyclic diisocyanates, with a malonic acid ester having a tertiary alkyl group and a secondary or primary alkyl group as blocking agents, maintaining a specific molar ratio to ensure storage stability and low-temperature curability, forming a resin film with improved properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional blocked polyisocyanate compositions are used, then curability is achieved, but high baking temperature (140°C or higher) is required which increases energy consumption and limits substrate applicability
Solution Approach 1:
The invention changes the chemical structure parameters of the blocking agent from conventional types to a specific compound with formula (1) containing a quaternary carbon atom. This structural parameter change enables the blocking agent to release isocyanate groups at lower temperatures (80-100°C), thereby reducing the baking temperature required and associated energy consumption while maintaining curability.
Solution Approach 2:
The invention creates a composite blocked polyisocyanate composition by combining the polyisocyanate component with a specifically designed blocking agent having formula (1). This composite structure allows the blocking agent to function as both a storage stabilizer and a low-temperature curing agent, enabling curability at reduced temperatures without requiring high energy input.
2Temperature
If conventional blocked polyisocyanate compositions are used, then curability is achieved, but high baking temperature (140°C or higher) is required which limits use on heat-sensitive substrates
Solution Approach 1:
By changing the blocking agent structure to formula (1) with a quaternary carbon atom, the invention reduces the curing temperature to 80-100°C. This temperature reduction expands substrate applicability to include heat-sensitive materials such as certain plastics and coatings that would deform or degrade at conventional high baking temperatures of 140°C or higher.
3Adaptability or versatility
If polyisocyanate is used in water-based coating materials, then coating versatility is improved, but reactivity with water causes gelation and excessive thickening during storage
Solution Approach 1:
The blocking agent acts as an intermediary that temporarily deactivates the isocyanate groups by forming a stable blocked complex. This prevents direct reaction between isocyanate and water during storage, eliminating gelation and thickening issues. The blocking agent can be released under controlled curing conditions to enable the desired crosslinking reaction, thus enabling water-based coating applications with improved storage stability.
4Temperature
If conventional blocked polyisocyanate compositions are used, then curability is achieved, but baking temperature of 140°C or higher is required which reduces work efficiency due to extended curing time
Solution Approach 1:
By changing to a lower baking temperature regime (80-100°C) through the specialized blocking agent structure, the invention reduces the thermal energy input required for curing. This lower temperature curing process decreases the time needed to achieve adequate crosslinking, thereby improving work efficiency and productivity without sacrificing curability.
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 achieves good storage stability and curability at 80°C, enhancing the usability of polyurethane resin coatings in automated systems and allowing for water-based applications without the need for high-temperature baking.
Implementation Method 1
since isocyanate reacts easily with water
Implementation Method 2
curability at 80°C
Data Source
AI summary
Providing a blocked polyisocyanate composition having good storage stability when used as a resin composition and good curability at a low temperature of about 80°C when formed into a resin film. [Means for Solving the Problems] The blocked polyisocyanate composition contains a blocked polyisocyanate derived from a polyisocyanate and one or more blocking agents. The blocked polyisoxyanate composition has a constitutional unit represented by the following general formula (I) and a constitutional unit represented by the following general formula (II), wherein a molar ratio of the constitutional unit represented by the following general formula (II) to the constitutional unit represented by the following general formula (I) is more than 5/95 and less than 95/5.