Crosslinkable Composition Latent Catalyst Flow
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Solution Overview
Problem
Existing RMA crosslinkable compositions face challenges in balancing fast curing profiles with robustness against acidic contaminants, which can lead to surface defects and uneven hardness development, especially in high-solid content coatings, and are not suitable for complex substrates or highly pigmented systems.
Innovation Solution
A crosslinkable composition comprising a malonate or acetoacetate-based RMA donor, an acryloyl-based RMA acceptor, and a catalyst system with a carbonate salt, along with an X-H group containing component that acts as a Michael addition donor, creating an induction time for improved flow and levelling, and subsequent accelerated curing to prevent solvent entrapment and enhance hardness build-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high levels of catalyst are used to achieve fast curing profile and high robustness against acid contaminants, then curing speed and robustness are improved, but surface appearance and hardness development are negatively influenced
Solution Approach 1:
A latent base catalyst system is introduced as an intermediary that remains inactive during application and initial flow/levelling periods, then activates later to initiate curing. This mediator allows the formulation to tolerate higher catalyst levels for robustness without causing premature surface defects, as the catalyst only becomes active when needed (after solvent evaporation and levelling).
Solution Approach 2:
The formulation includes acid scavengers that preemptively neutralize acid contaminants before they can interfere with the curing reaction. This preliminary protective action allows the use of higher catalyst levels for robustness without compromising surface appearance, as the acid interference is prevented in advance.
2Productivity
If high levels of catalyst are used to achieve fast curing profile, then curing speed is improved, but surface appearance and hardness development are negatively influenced
Solution Approach 1:
The coating formulation is designed to undergo preliminary flow and levelling actions before curing begins. The latent catalyst system remains inactive during this critical surface-forming period, allowing the coating to self-level properly. Only after this preliminary action is complete does the catalyst activate to initiate fast curing, thus achieving both good surface appearance and high curing speed.
Solution Approach 2:
The catalyst system transitions from an inactive state during application and flow to an active state during curing. This dynamic behavior allows the formulation to adapt to different process stages: remaining quiescent when surface quality is being established, then becoming highly reactive when curing speed is needed, thus resolving the contradiction between surface appearance and curing speed.
3Productivity
If curing occurs very fast especially at the surface, then productivity is improved, but solvent entrapment and surface irregularities occur
Solution Approach 1:
The formulation allows solvent evaporation and surface formation to occur before curing begins. The latent catalyst system remains inactive during this preliminary phase, enabling solvents to escape and the surface to level properly without being locked in place by premature crosslinking. Only after this preliminary action is complete does fast curing begin, preventing solvent entrapment while maintaining high productivity.
Solution Approach 2:
The curing process is divided into distinct periods: an initial period where solvents evaporate and the coating flows/levels without significant crosslinking, followed by a second period where fast curing occurs. This periodic action separates the solvent removal phase from the crosslinking phase, preventing solvent entrapment while achieving high curing speed in the second period.
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 a balanced reactivity profile with prolonged open time for flow and levelling, reducing surface defects and enhancing hardness development while maintaining fast curing completion, thus improving the appearance and mechanical properties of the coating.
Implementation Method 1
a component with at least 2 activated unsaturated groups (hereafter also referred to as the RMA acceptor) and a component with at least 2 acidic protons C-H in activated methylene or methine groups (hereafter also referred to as the RMA donor) react and crosslink to each other in the presence of a strong base catalyst
Implementation Method 2
Real Michael addition is activated by strong bases
Data Source
AI summary
The invention relates to a crosslinkable composition comprising a component A with at least 2 acidic protons C-H in activated methylene or methine groups (the RMA donor group), and a component B with at least 2 activated unsaturated groups (the RMA acceptor group), and a catalyst system C that contains, or is able to generate a basic catalyst capable of activating the RMA reaction between components A and B, characterised in that the crosslinkable composition further comprises an X-H group containing component D that is also a Michael addition donor reactable with component B under the action of catalyst C, wherein X is N, P, O, S or wherein X is C as part of an acidic methyl (CH3) group. The invention further relates to the use of component D and of catalyst additive mixtures for the manufacture of RMA crosslinkable composition having improved surface appearance.