Silane-Grafted Wood Coating Dispersion for Tannin Blocking
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Solution Overview
Problem
Existing aqueous coatings for wood surfaces, particularly those with visible knots, suffer from migration of tannins and other colored compounds, leading to blisters and poor adhesion, with known solutions either turning yellow over time or having limited performance due to compatibility issues with additives.
Innovation Solution
An aqueous polymer dispersion combining carboxylic acid monomers, tertiary amine monomers, and grafted silane groups, which is self-crosslinkable without additional crosslinking agents, effectively blocks tannins and other compounds, enhancing resistance to blistering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aqueous coatings are applied to wood surfaces with knots, then the coating provides initial protection, but tannins and colored compounds migrate to the surface causing blisters and blemishes over time
Solution Approach 1:
The coating composition includes a water-soluble polyphenolic compound that proactively binds to tannins and colored compounds in the wood before they can migrate to the surface. This preliminary binding action prevents the harmful migration that would otherwise occur over time, addressing the contradiction by acting in advance to secure long-term reliability.
Solution Approach 2:
The water-soluble polyphenolic compound acts as an intermediary substance between the wood substrate and the coating system. It mediates the interaction by binding to migratable compounds in the wood, preventing them from reaching the coating surface and causing blisters or blemishes, thus maintaining coating durability.
2Object-affected harmful factors
If cationic polymer-based coatings are used for blocking tannins, then good blocking performance is achieved, but the coating turns yellow over time
Solution Approach 1:
The invention changes the chemical parameters of the coating composition by using a water-soluble polyphenolic compound instead of cationic polymers. This parameter change maintains effective tannin blocking while eliminating the yellowing issue, as polyphenolic compounds do not undergo the same oxidative yellowing reactions as cationic polymers.
Solution Approach 2:
The coating composition uses a water-soluble polyphenolic compound that provides uniform blocking performance across the coating system. This homogeneous approach ensures consistent tannin prevention without the localized yellowing problems that can occur with cationic polymer-based coatings.
3Ease of manufacture
If anionic emulsion-based coatings are used, then yellowing is avoided, but blocking performance against tannins is limited due to compatibility issues with additives
Solution Approach 1:
The invention changes the chemical nature of the coating from anionic emulsion to a water-soluble polyphenolic compound system. This parameter change enables both good tannin blocking performance and compatibility with various additives, as the polyphenolic compounds can interact with tannins through multiple binding mechanisms while maintaining formulation flexibility.
4Object-affected harmful factors
If multiple coats of paint are applied to prevent blemishes, then some blocking is achieved, but blemishes can still reappear and the process is time-consuming
Solution Approach 1:
The water-soluble polyphenolic compound performs preliminary binding of tannins and colored compounds in a single coating application. This preliminary action eliminates the need for multiple coats, as the binding occurs at the wood-coating interface before migration can happen, saving time while effectively preventing blemishes.
Solution Approach 2:
The coating composition contains the water-soluble polyphenolic compound that automatically binds to migratable compounds in the wood substrate. This self-service mechanism provides effective tannin blocking without requiring additional application steps or multiple coats, reducing the time loss associated with repeated coating applications.
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 dispersion provides improved resistance to blistering and migration of tannins, maintaining aesthetic appearance and durability of wood coatings, with a single-component system that does not require additional crosslinking agents.
Implementation Method 1
the migration at the surface of the coating of tannins and of other wood compounds which can migrate, such as lignin and derivatives... blocking the migration of tannins and other compounds present in wood
Implementation Method 2
The invention also covers a coated substrate, in particular made of wood having visible knots at the surface or knots in the heart of the wood... grafted silane groups
Data Source
AI summary
The invention relates to an aqueous polymer dispersion, with said polymer comprising, in its structure, monomer units incorporated from a composition of monomers comprising: a) at least one (meth)acrylic monomer which is a C1-C18 (meth)acrylic ester, without any ionic group, b) at least one ethylenically unsaturated monomer carrying at least one carboxylic acid group, c) at least one ethylenically unsaturated monomer carrying a tertiary amine, and with said polymer additionally carrying grafted blocked silane groups in the —Si(OR1)3 or —Si—R2(OR1)2 or —Si—(R2)2(OR1), with R1, R2 being an identical or different C1 to C4 alkyl, and with said grafted blocked silane groups being incorporated by at least one or two routes or their combination. The invention also relates to a coating composition comprising said dispersion of the invention and to its use for aqueous protective coating compositions for wood.