Aqueous Aluminum Brazing Composition with Low-Residue Polyurethane Binder
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Solution Overview
Problem
In heat exchangers, especially those with complex and thin components, the thermal decomposition of binder resins in brazing compositions can lead to incomplete decomposition products staying in closed spaces, causing surface darkening and poor appearance, while existing compositions lack storage stability and effective brazability in both open and closed environments.
Innovation Solution
An aqueous aluminum brazing composition with a water-soluble/dispersible polyurethane resin that exhibits low residual ratios at 400°C and 520°C, ensuring complete decomposition and minimizing surface darkening, combined with a flux and water-miscible solvent, is used to improve brazability and storage stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional binder resin is used in brazing composition, then the composition can be stored for extended periods, but incomplete decomposition products remain in closed spaces causing surface darkening and poor appearance
Solution Approach 1:
The patent changes the chemical composition parameters of the binder resin by specifying precise proportions of polyester polyol (40-80 parts), polyether polyol (10-50 parts), and isocyanate (10-30 parts) to achieve optimal decomposition characteristics that prevent surface darkening while maintaining storage stability
Solution Approach 2:
The patent creates a composite binder resin system combining multiple polyol types (polyester and polyether) with isocyanate to achieve synergistic effects that simultaneously provide storage stability and complete thermal decomposition without harmful residues
2Object-affected harmful factors
If the binder resin is thermally decomposed sufficiently to prevent surface darkening, then complete decomposition products are achieved, but the composition may lose storage stability
Solution Approach 1:
The patent optimizes the molecular weight range (100-10,000) and chemical composition ratios to achieve a balance where the resin decomposes completely at brazing temperatures while remaining stable during storage, preventing both surface darkening and degradation
3Weight of moving object
If heat exchanger components are reduced in thickness and complexity increased to enhance performance, then weight is reduced and performance enhanced, but the spaces between components become small and closed, trapping decomposition gases
Solution Approach 1:
The patent converts the potential harm of trapped decomposition gases into a benefit by designing a binder resin that decomposes completely into harmless substances (water, carbon dioxide, and simple organic compounds) that do not cause surface darkening or appearance defects even when trapped in closed spaces
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 effectively prevents surface darkening, enhances brazability, and maintains storage stability, ensuring a favorable appearance and efficient joining of aluminum components in both open and closed spaces.
Implementation Method 1
the binder resin is thereby thermally decomposed, and the components are brazed (joined)
Data Source
AI summary
An aqueous aluminum brazing composition contains, as a binder resin, a water-soluble/dispersible polyurethane resin that exhibits a residual ratio of 60% by mass or less in a 400° C. heating environment and exhibits a residual ratio of 1.0% by mass or less in a 520° C. heating environment.