Moisture-Curing Coatings Using Butylsilane Binders
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Solution Overview
Problem
Existing moisture-curing coating compositions based on alkoxysilane groups have a high curing rate with short potlife, inadequate performance properties for automotive refinishes, and issues with surface defects and methanol release.
Innovation Solution
A moisture-curing coating composition using aprotic solvents with polyacrylate or polymethacrylate binders containing ethoxysilane groups and a phosphorous- and nitrogen-containing catalyst, allowing for rapid curing at low temperatures while maintaining a longer potlife and reducing methanol release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If alkoxysilane-functional prepolymers with high moisture reactivity are used, then curing rate is improved, but potlife becomes too short
Solution Approach 1:
The patent changes the chemical parameters of the silane groups from highly reactive types (methoxysilane, ethoxysilane) to less reactive butylsilane groups. This parameter change reduces the curing rate constant, allowing the coating to remain workable for an extended potlife of at least 30 minutes while still achieving complete curing at 60°C within 30 minutes.
2Loss of time
If conventional silane-modified polymers are used, then potlife is extended, but curing rate becomes too slow
Solution Approach 1:
The patent optimizes the balance between potlife and curing rate by selecting butylsilane groups with specific reactivity characteristics. The butylsilane provides moderate moisture reactivity that enables both extended potlife (≥30 minutes) and rapid curing (complete in 30 minutes at 60°C), resolving the trade-off between these two parameters.
3Productivity
If methoxysilane or ethoxysilane groups are used, then curing rate is improved, but methanol release increases
Solution Approach 1:
The patent changes the alkoxy group parameter from methyl or ethyl to butyl groups. This substitution fundamentally alters the byproduct of the condensation reaction from methanol or ethanol to butanol, which has lower toxicity and vapor pressure. The butylsilane groups maintain adequate curing rate while eliminating the harmful methanol release associated with conventional silane systems.
4Loss of substance
If high solids content is achieved, then environmental performance is improved, but application viscosity increases
Solution Approach 1:
The patent achieves a solids content of at least 60% by weight through careful formulation of the coating composition. The use of butylsilane-functionalized polyacrylate and polymethacrylate binders allows this high solids content to be attained while maintaining manageable viscosity for spray application, balancing environmental performance with ease of application.
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 achieves rapid curing at 60°C within 30 minutes, maintains a potlife of at least 30 minutes, produces coatings with high transparency and no surface defects, and has a high solids content, while minimizing methanol release.
Implementation Method 1
In the presence of atmospheric moisture, the alkoxysilane groups of the binders are capable even at room temperature of undergoing condensation of one another, with elimination of the alkoxy groups, to form Si—O—Si bridges
Implementation Method 2
as crosslinking catalyst at least one phosphorous- and nitrogen-containing catalyst (B)
Data Source
AI summary
Disclosed is a moisture-curing coating composition based on aprotic solvents comprising a binder with a polyacrylate or polymethacrylate obtained using monomer (I)and a phosphorous- and nitrogen-containing catalyst. Also disclosed is a method of producing a multicoat finish using these coating compositions and also to the use of this method to coat interior or exterior bodywork components or to coat components for shipbuilding and aircraft construction or to coat components for household and electrical appliances or to coat plastics moldings or films.