Blocked Hydrazone Cross-Linking for Water-Borne Coatings
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Solution Overview
Problem
Water-borne compositions, such as paints and coatings, face challenges with premature cross-linking of polymers containing vinyl-containing monomers, which leads to reduced mechanical and physical properties and shelf-life instability due to the interference of acetaldehyde products with cross-linking agents, resulting in inadequate performance and safety concerns from volatile substances like acetone.
Innovation Solution
Employing a blocked cross-linking agent with a hydrazone group that remains non-reactive with acetaldehyde and converts to an active hydrazide form during coalescence, allowing controlled cross-linking upon application, thereby preventing premature cross-linking and enhancing the mechanical and physical properties of the films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a cross-linking agent is used to improve mechanical properties and durability, then adhesion, scrubability, and chemical resistance are improved, but premature cross-linking occurs during storage leading to viscosity instability and reduced shelf-life
Solution Approach 1:
The patent applies preliminary anti-action by using a blocked cross-linking agent that is pre-prepared but rendered non-reactive through blocking. The cross-linking functionality is present in the formulation but prevented from reacting during storage by the blocking group. This anticipates and prevents the harmful effect of premature cross-linking while maintaining the potential for beneficial cross-linking upon application.
Solution Approach 2:
The patent employs parameter changes by modifying the chemical state of the cross-linking agent from active to blocked form. The blocking group changes the reactivity parameter of the cross-linking agent, making it non-reactive during storage. Upon application, conditions change (water evaporation, pH shift, or enzymatic action) that reverse the blocking, restoring cross-linking capability.
2Strength
If cross-linking occurs during storage to improve film properties, then mechanical strength is enhanced, but the polymer gels and builds viscosity in the can resulting in poor film formation
Solution Approach 1:
The blocked cross-linking agent provides preliminary anti-action by preventing the gelation and viscosity build-up that would occur with active cross-linking agents during storage. The blocking mechanism stops the cross-linking reaction before it can interfere with film formation, while still allowing the cross-linking to occur after application when film formation is complete.
3Reliability
If volatile substances like acetone are used to suppress premature cross-linking, then shelf-life is improved, but safety hazards and environmental concerns arise
Solution Approach 1:
The patent applies the taking out principle by removing the need for volatile substances like acetone entirely. Instead of using harmful volatiles to suppress cross-linking, the invention extracts the cross-linking functionality from the active state and places it in a blocked state that is inherently stable and non-volatile, eliminating safety and environmental hazards.
Solution Approach 2:
The blocking group serves as an intermediary between the cross-linking agent and the polymer. It temporarily prevents direct interaction during storage, providing shelf-life stability without requiring volatile substances. The intermediary is removed or deactivated upon application, allowing the cross-linking reaction to proceed.
4Ease of manufacture
If self-cross-linking polymers are used to simplify formulation, then manufacturing is easier, but mechanical property improvement is minimal particularly for scrubability
Solution Approach 1:
The patent merges the advantages of both self-cross-linking and external cross-linking approaches. It uses polymers with cross-linkable functionality (like self-cross-linking) combined with a blocked cross-linking agent (providing external cross-linking capability). This combination achieves superior scrubability through extensive cross-linking while maintaining formulation simplicity and ease of manufacture.
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
This approach effectively mitigates premature cross-linking, ensuring the attainment of desired mechanical and physical properties like adhesion, toughness, and scrubability, while eliminating safety hazards associated with volatile substances and improving stoichiometric control.
Implementation Method 1
a blocked cross-linking agent, such as in hydrazone form, that is not capable of reacting with the acetaldehyde product but is capable of converting to a cross-linking agent form, such as in hydrazide form
Implementation Method 2
The binder and the pigment, if present, are the primary solid components of the water-borne composition and remain on surfaces to which they have been applied forming a solid layer as solvent evaporates
Implementation Method 3
Coalescence is a process whereby polymer particles in aqueous dispersion come into contact with one another during drying, and polymer chains form (i.e., diffuse) across boundaries of latex/dispersion particles
Data Source
AI summary
Water-borne cross-linking polymeric compositions and related embodiments, such as methods of making and using the compositions, as well as products formed with said compositions are described. The water-borne composition may comprise one or more polymers formulated from one or more monomers of which at least one is a monomer that yields acetaldehyde as a hydrolysis product, and incorporating cross-linking functionality such as, but not limited to, carbonyl or epoxy functionality, and a blocked cross-linking agent, for example, a hydrazone. Neither the cross-linking functionality nor the acetaldehyde reacts with the blocked cross-linking agent; however, the blocked cross-linking agent is capable of conversion to an alternative form cross-linking agent such as, but not limited to, a hydrazide, to yield a cross-linked polymer. The alternative form cross-linking agent may be formed in an equilibrium reaction including the blocked cross-linking agent.