Functionalized Polyurethane Binder for Complete Curing
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Solution Overview
Problem
Radiation-curable water-emulsifiable polyurethane (meth)acrylates face issues with incomplete curing in shaded areas or thick layers due to insufficient high-energy radiation penetration, and existing binder formulations have lower crosslinking density and are prone to yellowing.
Innovation Solution
Aqueous binder formulation comprising a polyurethane A obtained by reacting diisocyanates or polyisocyanates with specific organic compounds, excluding aldehydic and ketonic carbonyl groups, and a carboxylic acid hydrazide B, which can cure both with and without high-energy radiation, achieving high crosslinking density and pendulum hardness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If radiation-curable water-emulsifiable polyurethane (meth)acrylates are used, then curing can be achieved with high-energy radiation, but incomplete curing occurs in shaded areas or thick layers due to insufficient radiation penetration
Solution Approach 1:
The patent employs a dual-cure mechanism that dynamically adapts to different application conditions: UV irradiation triggers acrylate group polymerization for rapid surface curing, while the hydrazone crosslinking system provides progressive curing throughout the coating thickness and in shaded areas, ensuring complete curing regardless of radiation penetration limitations
Solution Approach 2:
The binder combines polyurethane with acrylate groups and hydrazone crosslinking capability, creating a composite curing system that integrates both UV-curable acrylate polymerization and moisture-cured hydrazone crosslinking, thereby achieving reliable curing across diverse substrate geometries and coating thicknesses
2Strength
If conventional binder formulations are used, then crosslinking can occur, but the crosslinking density is lower and yellowing occurs
Solution Approach 1:
The patent modifies the chemical structure by incorporating acrylate groups into the polyurethane backbone and utilizing hydrazone crosslinking, which changes the crosslinking mechanism to achieve higher crosslinking density while avoiding the yellowing associated with conventional amine-based systems through altered chemical reaction pathways
Solution Approach 2:
The formulation uses specific functional groups (acrylate and hydrazone) at strategic positions within the polyurethane structure to locally enhance crosslinking density in the coating matrix, creating regions of high crosslinking that improve overall coating strength without introducing yellowing-prone aromatic or amine components
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 formulation ensures complete curing in complex substrate shapes and thick layers without radiation, while maintaining high crosslinking density and preventing yellowing, thus providing stable and effective coatings.
Implementation Method 1
aqueous binder formulation comprising a polyurethane A and a carboxylic acid hydrazide B
Implementation Method 2
Radiation-curable water-emulsifiable polyurethane (meth)acrylates
Data Source
AI summary
Described herein are binder formulations based on acryloyloxy-functionalized polyurethanes.