RMA Coating Primer Adhesion to Metal Substrates
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Solution Overview
Problem
RMA crosslinkable compositions exhibit poor adhesion properties, particularly on polar surfaces such as metal substrates, and existing epoxy primers do not consistently provide good adhesion results for these coatings.
Innovation Solution
A coating system comprising a primer composition with a binder component containing primary amine functionality blocked with a ketone or aldehyde and another component with acetoacetate or acetoacetamide functional groups, combined with an RMA crosslinkable composition featuring components with acidic protons and activated unsaturated groups, along with a catalyst for the Michael Addition reaction, forming an organic binder network that enhances adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If RMA crosslinkable compositions are applied directly to metal substrates, then the coating process is simple, but adhesion to the substrate is poor
Solution Approach 1:
The patent introduces a primer coating composition as an intermediary layer between the metal substrate and the RMA crosslinkable topcoat. This primer contains binder components with specific functional groups (carboxylic acid, hydroxyl, or amine) that chemically interact with both the substrate and the topcoat, serving as a mediator that enables adhesion without requiring modification of the RMA crosslinkable composition itself.
2Reliability
If epoxy primers are used to improve adhesion of RMA crosslinked coatings, then adhesion is improved, but compatibility with all RMA compositions is not consistent
Solution Approach 1:
The patent defines specific parameter ranges for the primer composition to ensure broad compatibility with RMA crosslinkable compositions. The primer contains binder components with carboxylic acid, hydroxyl, or amine functional groups in controlled amounts (0.1-10 wt%, 1-20 wt%, or 1-5 wt% respectively), along with controlled water content (5-50 wt%) and pH (6-9). These parameter specifications allow the primer to work consistently across different RMA composition formulations without requiring custom optimization for each topcoat.
3Reliability
If a primer layer is applied to improve adhesion, then adhesion to metal substrates is improved, but the coating system becomes more complex
Solution Approach 1:
The patent applies local quality by concentrating the adhesion-promoting functionality specifically in the primer layer that contacts the metal substrate, while the RMA crosslinkable topcoat maintains its original composition and properties. The primer contains the specialized binder components with functional groups tailored for metal surface interaction, whereas the topcoat focuses on providing the desired finish and protection properties through RMA crosslinking, allowing each layer to optimize its specific function.
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 coating system achieves excellent adhesion of the cured RMA crosslinked coating to the primer layer and substrates, particularly metal substrates, with improved durability and resistance to weathering.
Implementation Method 1
RMA crosslinkable compositions are compositions comprising at least one RMA crosslinkable component comprising components A and B each comprising at least 2 reactive groups wherein the at least 2 reactive groups of component A are acidic protons (C-H) in activated methylene or methine groups (RMA donor group), and the at least 2 reactive groups of component B are activated unsaturated groups (C=C) (RMA acceptor group). These reactive groups react to achieve crosslinking by Real Michael Addition (RMA) reaction between said at least one RMA crosslinkable components in the presence of a base catalyst (C).
Implementation Method 2
The binder component PA that contains primary amine functionality blocked with a ketone or aldehyde, preferably a ketone, and binder component PB that contains acetoacetate or acetoacetamide, preferably acetoacetate-, functional groups, which components PA and PB form an organic binder network in a cured primer coating.
Implementation Method 3
a substituted carbonate catalyst which decomposes in a coating layer to generate carbon dioxide which evaporates from the applied curing coating layer
Data Source
AI summary
The invention relates to a coating system comprising I) a primer coating composition comprising a binder component PA that contains primary amine functionality blocked with a ketone or aldehyde, a binder component PB that contains acetoacetate or acetoacetamide functional groups and II) a RMA crosslinkable coating composition a component A with at least two acidic protons C-H in activated methylene or methine groups, a component B with at least two activated unsaturated C=C groups and a base crosslinking catalyst C. The invention also relates to the use of the specified primer coating composition for improving adhesion of a RMA crosslinkable coating composition, in particular to metal substrates, to a method for coating a substrate and to coated substrates coated with the coating system of the invention.