Aqueous Coating Composition for Stable 1K Aziridine Crosslinking
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Solution Overview
Problem
Current waterborne 1K coating systems using multi-aziridine crosslinkers suffer from stability issues when combined with carboxylic acid functional polymers, leading to hazardous materials and limited shelf life, while 2K systems require mixing before application, increasing complexity and cost.
Innovation Solution
An aqueous coating composition with a pH of 8 to 14, containing multi-aziridine compound particles and carboxylic acid functional polymer particles, which allows for self-crosslinking at room temperature, providing a stable one-pack system with improved crosslinking efficiency and extended shelf life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional low molecular weight crosslinkers are used to achieve high crosslinking density, then crosslinking efficiency is improved, but stability of the coating composition deteriorates due to immediate reaction with water and carboxylate species
Solution Approach 1:
The crosslinking system is segmented into two distinct components: carboxylic acid functional polymer particles and multi-aziridine compound particles, each maintained separately in the aqueous medium. This segmentation prevents premature reaction while enabling crosslinking upon drying, resolving the contradiction between stability and crosslinking efficiency.
Solution Approach 2:
The aqueous medium acts as an intermediary that stabilizes both the carboxylic acid functional polymer and multi-aziridine compound separately, preventing their direct interaction. The pH control (8-14) serves as a mediating condition that maintains stability during storage but allows crosslinking to proceed upon drying.
2Stability of the object's composition
If 2K coating systems are used to maintain stability, then shelf life is improved, but device complexity increases due to required mixing before application
Solution Approach 1:
The invention merges the binder (carboxylic acid functional polymer) and crosslinker (multi-aziridine compound) into a single 1K coating composition that remains stable during storage. Both components are combined in the same aqueous medium without requiring separate storage or pre-mixing, thus eliminating the complexity of 2K systems while maintaining shelf life.
Solution Approach 2:
The coating composition performs self-crosslinking upon drying without requiring external mixing or activation. The system automatically initiates crosslinking when the aqueous medium evaporates, eliminating the need for user intervention to mix components before application.
3Reliability
If homogeneous distribution of crosslinker is achieved for high crosslinking density, then crosslinking efficiency is improved, but harmful factors increase due to susceptibility to nucleophilic species like water
Solution Approach 1:
The crosslinker is segmented into discrete multi-aziridine compound particles that are spatially separated from the carboxylic acid functional polymer particles during storage. This segmentation protects the aziridine groups from nucleophilic attack by water and carboxylate species while ensuring homogeneous distribution upon drying for efficient crosslinking.
Solution Approach 2:
The aqueous medium with controlled pH (8-14) creates a stabilized environment that protects the multi-aziridine compound from premature reaction with nucleophilic species. The environment remains inert during storage but allows crosslinking to proceed upon drying when water evaporates.
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 efficient crosslinking upon drying, offering a user-friendly, high-performance 1K system with reduced handling of hazardous materials and improved coating properties, suitable for a wide range of substrates.
Implementation Method 1
aziridine crosslinking of carboxylic acid functional polymers... these reactive molecules commonly display immediate reaction with carbon/late-functional binders
Implementation Method 2
efficient crosslinking upon drying
Data Source
AI summary
The present invention relates to an aqueous coating composition comprising a multi-aziridine compound and a carboxylic acid functional polymer, characterized in that (i) the composition is an aqueous dispersion having a pH ranging from 8 to 14, (ii) the aqueous dispersion comprises particles X which particles X comprise multi aziridine compound and particles Y which particles Y comprise carboxylic acid functional polymer, and (iii) said multi-aziridine compound has: a) from 2 to 6 of the following structural units A: b) one or more linking chains wherein each one of these linking chains links two of the structural units A; and c) a molecular weight in the range from 500 to 10000 Daltons.