Wood Coating Polyurethane Dispersion with Fatty Acids
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Solution Overview
Problem
Aqueous polyurethane dispersions used for wood coatings exhibit inferior wood-wetting properties compared to solvent-borne systems, compromising the enhancement of natural wood structures.
Innovation Solution
Incorporating hydroxyl group-containing unsaturated fatty acids into polyurethane dispersions, which can be cured with polyaziridines, carbodiimides, or non-blocked polyfunctional isocyanates at ambient or slightly elevated temperatures, to improve wood-wetting properties while maintaining mechanical and chemical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional aqueous polyurethane dispersions are used for wood coatings, then the coating provides basic protection and ease of application, but the wood-wetting properties are inferior compared to solvent-borne systems
Solution Approach 1:
The patent modifies the chemical composition parameters of the polyurethane dispersion by incorporating hydroxyl group-containing unsaturated fatty acids (such as castor oil, tung oil, or linseed oil derivatives) into the polyurethane structure. This chemical parameter change alters the surface properties of the coating, enabling superior wood-wetting properties while maintaining the aqueous nature of the system.
Solution Approach 2:
The invention creates a composite polyurethane structure that combines conventional polyurethane components with hydroxyl group-containing unsaturated fatty acids. This composite approach integrates the benefits of both materials: the protective and mechanical properties of polyurethane with the excellent wood-wetting capabilities of oil-based components, achieving performance comparable to or exceeding solvent-borne systems.
2Reliability
If hydroxyl group-containing unsaturated fatty acids are incorporated into polyurethane dispersions, then wood-wetting properties are improved, but the complexity of the polymer synthesis increases
Solution Approach 1:
The patent employs preliminary action by pre-modifying the polyol component with hydroxyl group-containing unsaturated fatty acids before the main polyurethane synthesis. This preliminary modification simplifies the overall process by incorporating the desired wood-wetting properties into the base polymer structure beforehand, rather than requiring complex post-synthesis modifications or multi-step reactions during the main polymerization process.
3Strength
If the polyurethane is modified with hydroxyl group-containing unsaturated fatty acids, then mechanical and chemical resistance is maintained or enhanced, but the manufacturing process becomes more complex
Solution Approach 1:
The invention optimizes the formulation parameters by selecting specific ratios of hydroxyl group-containing unsaturated fatty acids (at least 40% of the total fatty acid content) and controlling the hydroxyl number within a specific range (120-230 mg/g). These parameter optimizations ensure that the modified polyurethane maintains or enhances mechanical and chemical resistance while keeping the manufacturing process manageable through defined compositional guidelines.
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 modified polyurethane dispersions demonstrate superior wood-wetting properties and enhanced mechanical and chemical stability, comparable to or exceeding conventional aqueous polyurethane coatings.
Implementation Method 1
Incorporation of the said fatty acids is effected by reaction of its hydroxyl group with an isocyanate group of a polyfunctional isocyanate A which is used in the synthesis of the polyurethane U
Implementation Method 2
at least partly neutralising the group capable of forming anions in the compound D, to form anionic groups
Implementation Method 3
dispersing this polymer in water
Implementation Method 4
the coatings thus produced are usually inferior to those made from solvent borne systems with regard to the wood wetting properties which leads to enhancement of the immanent structure found in natural substrates such as wood
Data Source
AI summary
A two-pack coating composition comprising curing agents selected from the group consisting of non-blocked poly-functional isocyanates I, polyaziridines Z, and carbodiimides Y, and an aqueously dispersed polyurethane U wherein the polyurethane U comprises building blocks derived from hydroxyl group containing unsaturated fatty acids B21, a process for the production of the polyurethane U, and a method of use thereof in combination with the said curing agents in preparing coating compositions which are particularly useful for wood.