Blocked Polyisocyanate Composition for Low-Temperature Curing
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Solution Overview
Problem
Conventional polyurethane resin coating materials are inconvenient due to their two-component system, requiring separate storage and rapid gelation, making them difficult to use in automatic coating processes, and blocked polyisocyanates require high baking temperatures, limiting their applications and causing operational inefficiencies.
Innovation Solution
A blocked polyisocyanate composition using a specific blocking agent that allows for low-temperature curing, maintaining viscosity stability and adhesion properties, even at 80°C or lower, and includes a hydrophilic blocked polyisocyanate for improved water dispersibility and compatibility with polyhydric hydroxy compounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyurethane coating materials are used, then abrasion resistance and chemical resistance are improved, but ease of operation deteriorates due to two-component system requiring separate storage and rapid gelation
Solution Approach 1:
The invention segments the polyol and polyisocyanate into separate components, with the polyol pre-reacted with a blocking agent to form a blocked polyol. This allows the coating material to be stored as a stable one-component system that only activates when exposed to moisture during application, resolving the contradiction between reliability (polyurethane performance) and ease of operation (storage and application convenience).
Solution Approach 2:
The polyol undergoes preliminary reaction with the blocking agent before storage, forming a blocked polyol that remains stable during storage but activates when exposed to moisture during application. This preliminary action allows the coating material to maintain stability during storage while still forming the necessary polyurethane crosslinks during application, solving the contradiction between storage stability and operational performance.
2Stability of the object's composition
If blocked polyisocyanates with conventional blocking agents are used, then storage stability is improved, but baking temperature requirement increases to at least 140°C
Solution Approach 1:
The invention changes the chemical parameters of the blocking agent, using a blocked polyol with specific functional groups that decompose at lower temperatures (around 100-120°C) compared to conventional blocking agents requiring 140°C or higher. This parameter change allows the coating to maintain storage stability while enabling lower-temperature curing, resolving the contradiction between storage stability and baking temperature requirement.
3Reliability
If high baking temperature is used for blocked polyisocyanate, then curability is improved, but energy consumption increases and substrate heat resistance requirement increases
Solution Approach 1:
The invention changes the thermal decomposition parameters of the blocking agent, using a blocked polyol that decomposes at lower temperatures (100-120°C) compared to conventional blocking agents. This parameter change enables the coating to achieve proper curability at lower temperatures, reducing energy consumption and eliminating the need for substrates with high heat resistance, thus resolving the contradiction between curability and energy consumption.
4Stability of the object's composition
If conventional blocked polyisocyanates are used, then storage stability is improved, but adhesion to polyester films deteriorates due to insufficient reactivity
Solution Approach 1:
The invention applies local quality by incorporating specific functional groups (carboxyl, hydroxyl, or amine groups) at particular locations within the blocked polyol structure. These local functional groups provide enhanced reactivity with polyester films while the overall blocked polyol structure maintains storage stability. This localized modification of chemical properties resolves the contradiction between storage stability and adhesion strength.
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 blocked polyisocyanate composition achieves superior low-temperature curability, hardness retention, and water resistance, as well as excellent initial adhesion and humidity/heat resistance, enabling efficient use in one-component coating materials and adhesive applications.
Implementation Method 1
the use of blocked polyisocyanates in which the active isocyanate groups are all blocked with a blocking agent has been proposed. These blocked polyisocyanates do not react with polyols at normal temperatures.
Implementation Method 2
under heating, the blocking agent dissociates, and the active isocyanate groups are regenerated and can react with the polyol via a crosslinking reaction
Implementation Method 3
the active isocyanate groups are regenerated and can react with the polyol via a crosslinking reaction
Implementation Method 4
includes a hydrophilic blocked polyisocyanate for improved water dispersibility and compatibility with polyhydric hydroxy compounds
Data Source
AI summary
A blocked polyisocyanate composition containing a blocked polyisocyanate obtained from a polyisocyanate and at least one blocking agent, wherein the blocking agent contains a compound represented by general formula (I) shown below, and the amount of methane tetracarbonyl structures represented by general formula (II) shown below, relative to the total molar amount within the blocked polyisocyanate of bonded structures in which the compound represented by general formula (I) is bonded to the polyisocyanate, is at least 0.5 mol% but not more than 10 mol%.