Polyurethane Coating with Dihydrazide to Reduce Aldehyde Emissions
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Solution Overview
Problem
Current methods for reducing aldehyde emissions, such as formaldehyde and acetaldehyde, in polyurethane artificial leather are inadequate, as existing solutions cannot effectively bind these substances without impacting processing properties or requiring significant modifications to polyurethane systems, and existing technologies struggle to address the stringent regulatory limits for volatile organic compounds in automotive and indoor applications.
Innovation Solution
The use of organic dihydrazides with limited water solubility, specifically adipic acid dihydrazide and diphenyloxy-4,4'-disulfohydrazide, is introduced into polyurethane coatings to effectively bind formaldehyde and acetaldehyde, reducing emissions while maintaining the processing properties of the polyurethane systems, allowing for the formation of solvent-free or low-solvent formulations that meet regulatory standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional polyurethane systems are used to produce artificial leather, then processing properties and mechanical performance are maintained, but aldehyde emissions (formaldehyde and acetaldehyde) exceed regulatory limits
Solution Approach 1:
The patent introduces dihydrazide compounds as intermediary substances that react with aldehydes (formaldehyde and acetaldehyde) to form hydrazones. These dihydrazides act as mediators between the harmful aldehydes and the polyurethane matrix, capturing the aldehydes through chemical reaction and preventing their emission, while maintaining compatibility with the existing polyurethane system
Solution Approach 2:
The patent converts the harmful effect of aldehyde emissions into a beneficial outcome by utilizing the reactive nature of aldehydes to form stable hydrazone bonds with dihydrazides. The harmful volatile substances are transformed into bound, non-volatile hydrazone structures that are integrated into the polyurethane matrix, thereby eliminating emissions while maintaining material integrity
2Reliability
If blocking agents are added to control isocyanate reactivity, then manufacturing safety is improved, but unpleasant smell and increased VOC values occur
Solution Approach 1:
The patent changes the chemical parameters of the system by introducing dihydrazide compounds with specific reactivity characteristics. These compounds alter the reaction kinetics and equilibrium of the polyurethane system, enabling controlled curing without requiring traditional blocking agents that leave residual odors and VOCs. The dihydrazides react with isocyanates to form stable urea linkages, changing the chemical pathway to eliminate harmful emissions
3Object-affected harmful factors
If aldehyde scavengers are added to bind formaldehyde and acetaldehyde, then emission limits are met, but processing properties and mechanical performance are compromised
Solution Approach 1:
The patent employs dihydrazide compounds that perform multiple functions simultaneously: they act as aldehyde scavengers to bind formaldehyde and acetaldehyde, serve as crosslinking agents to enhance mechanical properties through hydrazone bond formation, and maintain processing compatibility with conventional polyurethane systems. This multi-functionality eliminates the need for separate additives that would compromise mechanical performance
4Object-generated harmful factors
If solvent-free high-solid systems are used, then VOC emissions are reduced, but aldehyde emissions from raw materials and additives remain unaddressed
Solution Approach 1:
The patent extracts and targets the specific problem of aldehyde emissions from raw materials and additives by incorporating dihydrazide compounds that selectively react with aldehyde groups. This extraction approach isolates the aldehyde binding function from the broader VOC reduction strategy, addressing the remaining harmful emissions that solvent-free systems do not eliminate
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
This approach significantly reduces or eliminates aldehyde emissions by at least 30% to 70% in polyurethane composite structures, meeting stringent emission limits without compromising the processing or mechanical properties of the materials, enabling the production of zero-emission composite materials using conventional coating processes.
Implementation Method 1
an organic dihydrazide with a limited water solubility of at most 15 g per 100 g of water, the dihydrazide being used to reduce aldehyde emissions
Data Source
AI summary
The present invention relates to flowable formulations for forming polyurethane coatings, comprising an organic dihydrazide with a limited water solubility of at most 15 g per 100 g of water, wherein the dihydrazide is used to reduce or eliminate aldehyde emissions released from the polyurethane coating or composite structures comprising such a polyurethane coating. The present invention further relates to composite structures comprising polyurethane coatings formed from the flowable formulations, methods for producing such composite structures, and the use of corresponding organic dihydrazides for reducing and eliminating formaldehyde and acetaldehyde emissions in sheet products produced from flowable coating systems.