Cathodic Electrodeposition Coatings with Bismuth Nitrate and Polymethylene Urea
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Solution Overview
Problem
Existing electrophoretic coatings lack uniformity and elasticity, especially at low baking temperatures, and are prone to surface defects and oily precipitates when using bismuth compounds as crosslinking catalysts.
Innovation Solution
Combining basic bismuth nitrate with polymethylene urea as a crosslinking catalyst to facilitate crosslinking reactions at lower temperatures, resulting in a uniform, elastic, and defect-free film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If bismuth compounds are used as crosslinking catalysts in electrophoretic coatings, then crosslinking activity is improved, but oily precipitates form causing surface defects
Solution Approach 1:
The patent uses a carboxylic acid as an intermediary substance to mediate between the basic bismuth nitrate catalyst and the isocyanate groups. The carboxylic acid forms a complex with the basic bismuth nitrate, creating a more controlled catalytic system that maintains high crosslinking activity while preventing the formation of oily precipitates and surface defects.
Solution Approach 2:
The patent changes the chemical parameters of the catalytic system by introducing carboxylic acids with specific molecular weights and functional groups. This parameter modification allows the basic bismuth nitrate to function effectively as a catalyst without producing harmful side effects like oily precipitates, thus resolving the contradiction between activity and surface quality.
2Strength
If conventional crosslinking agents are used in electrophoretic coatings, then crosslinking occurs, but the film surface is non-uniform and lacks elasticity at low baking temperatures
Solution Approach 1:
The patent employs polymethylene urea, a novel crosslinking agent with specific molecular structure and reactivity parameters, that enables effective crosslinking at lower baking temperatures. This crosslinking agent produces uniform, homogeneous films with elastic properties, unlike conventional crosslinking agents that require high temperatures and produce non-uniform surfaces.
Solution Approach 2:
The patent creates a composite crosslinking system by combining basic bismuth nitrate catalyst with polymethylene urea crosslinking agent. This composite approach synergistically achieves effective crosslinking at low temperatures while producing uniform, elastic films, resolving the contradiction between crosslinking efficiency and surface quality.
3Reliability
If high baking temperatures are used to achieve sufficient crosslinking, then crosslinking completeness is improved, but energy consumption increases and film elasticity is reduced
Solution Approach 1:
The patent changes the reaction parameters by using basic bismuth nitrate as a highly active catalyst and polymethylene urea as a responsive crosslinking agent. This parameter change enables sufficient crosslinking completeness to be achieved at lower baking temperatures, thereby reducing energy consumption while maintaining film elasticity and preventing excessive brittleness.
4Temperature
If basic bismuth nitrate is used as catalyst, then crosslinking at lower temperatures is enabled, but distribution difficulty and slight catalytic activity occur
Solution Approach 1:
The patent introduces carboxylic acid as an intermediary that forms a soluble complex with basic bismuth nitrate. This intermediary approach improves the distribution and dispersibility of the catalyst throughout the binder system, eliminating the distribution difficulties inherent in using basic bismuth nitrate alone, while maintaining its ability to enable low-temperature crosslinking.
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 combination of basic bismuth nitrate and polymethylene urea enables electrophoretic coatings to be easily produced, stable, and filterable, with optimal particle size, excellent flow, and superior corrosion and edge protection, while maintaining mechanical properties.
Implementation Method 1
bismuth compounds have been preferred as crosslinking catalysts because, in addition to their high activity... The use of bismuth compounds as a catalyst in the formation of urethane structures from isocyanate and hydroxyl groups has long been known
Implementation Method 2
polymethylene urea with a crosslinking agent... The film has an even and homogeneous surface, even in critical edge areas, and has elastic properties
Implementation Method 3
cathodically depositable electrophoretic paint... could easily be electrophoretically deposited onto electrically conductive substrates
Data Source
AI summary
The invention relates to a cathodic electrodeposition coating which contains at least one binder, at least one cross-linker and at least one bismuth compound, characterized in that a basic bismuth nitrate is used as the bismuth compound and polymethylene urea is contained as an additional component.