Blocked Polyisocyanate Composition for Low-Temperature Coating Curing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional blocked polyisocyanate compositions require high baking temperatures, limiting their use on plastics with poor heat resistance, and face issues with adhesion when layered with upper-coating films and compatibility with polyols.
Innovation Solution
A blocked polyisocyanate composition using a specific combination of malonic acid diester and β-ketoester compounds as blocking agents, with a controlled molar ratio and the presence of a monoalcohol compound, to achieve low-temperature curability and improved adhesion and compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional blocking agents (oximes, phenols, alcohols, lactams) are used, then the blocked polyisocyanate composition can form crosslinked coating films, but a high baking temperature of 140°C or higher is required, resulting in extremely high energy costs and inability to process plastics with poor heat resistance
Solution Approach 1:
The patent changes the chemical structure parameters of the blocking agent by using malonic acid diester compounds with specific R1 and R2 substituent combinations (alkyl groups with 1-8 carbon atoms, cycloalkyl groups, phenyl groups, or benzyl groups). This structural parameter change enables the blocked polyisocyanate to cure at lower temperatures (100-120°C) while maintaining crosslinking effectiveness, thereby reducing energy consumption and enabling processing of heat-sensitive plastics.
Solution Approach 2:
The patent creates a composite blocking agent system by combining malonic acid diester compounds with specific structural features (R1 and R2 groups) and blocked polyisocyanates. This composite approach achieves synergistic effects where the specific molecular structure of the malonic acid diester enables low-temperature curability while maintaining film formation and crosslinking properties, resolving the contradiction between temperature reduction and functional performance.
2Temperature
If blocked polyisocyanate compositions capable of low-temperature curing (100°C or lower) are used, then energy costs are reduced, but adhesion to upper-layer coating films becomes insufficient
Solution Approach 1:
The patent applies local quality by designing specific regions (R1 and R2 substituents) of the malonic acid diester blocking agent with particular properties (alkyl groups with 1-8 carbon atoms, cycloalkyl groups, phenyl groups, or benzyl groups). These localized structural modifications create specific interaction sites that enhance interfacial adhesion to upper-layer coating films while maintaining overall low-temperature curability of the composition.
Solution Approach 2:
The patent modifies the molecular parameters of the blocking agent by selecting specific R1 and R2 group combinations that provide optimal balance between low-temperature reactivity and adhesion performance. The structural parameters (carbon chain length, cyclic structures, aromatic groups) are tuned to achieve sufficient adhesion strength at curing temperatures of 100-120°C, resolving the contradiction between temperature reduction and adhesion reliability.
3Temperature
If blocked polyisocyanate compositions with low-temperature curability are used, then processing of plastics with poor heat resistance becomes possible, but compatibility with some polyols becomes insufficient
Solution Approach 1:
The patent achieves universality by designing the malonic acid diester blocking agent with R1 and R2 groups that provide multiple functional benefits simultaneously: low-temperature curability, good polyol compatibility, and adequate adhesion. The structural design (alkyl groups with 1-8 carbon atoms, cycloalkyl groups, phenyl groups, or benzyl groups) creates a multi-functional blocking agent that works effectively across different polyol types and application conditions, resolving the contradiction between temperature reduction and compositional stability.
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 exhibits excellent adhesion to upper-layer coating films, compatibility with polyols, and low-temperature curability, addressing the limitations of conventional blocked polyisocyanate compositions.
Implementation Method 1
a blocked polyisocyanate composition which contains a blocked polyisocyanate obtained from a blocking agent and a polyisocyanate... capable of forming a crosslinked coating film at a temperature of 100° C. or lower
Implementation Method 2
polyisocyanates that are blocked with a blocking agent (blocked polyisocyanates)... capable of forming crosslinked coating films
Implementation Method 3
excellent adhesion to an upper-layer coating film when coating films are layered
Data Source
AI summary
The present invention provides a blocked polyisocyanate composition comprising a blocked polyisocyanate obtained from a blocking agent and a polyisocyanate derived from at least one diisocyanate selected from the group consisting of an aliphatic diisocyanate and an alicyclic diisocyanate, wherein the blocking agent comprises at least one selected from the group consisting of a malonic acid diester compound having a specific structure and a β-ketoester compound having a specific structure, and a molar ratio of a total of a specific keto form structure and a specific keto form structure to a total of a specific enol form structure and a specific enol form structure is 75/25 or more and 97/3 or less.