Radiation-Curable Polyurethane Acrylates for Wood Grain Highlighting
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Solution Overview
Problem
Existing radiation-curable, water-dispersible polyurethane acrylates exhibit low grain highlighting on wood substrates, necessitating the development of formulations that provide good grain highlighting, high optical transparency, and smooth film formation when dried at elevated temperatures.
Innovation Solution
The synthesis of urethane (meth)acrylates comprising specific components such as (cyclo)aliphatic di- and polyisocyanates, (cyclo)aliphatic diols, polyesterdiols, compounds with isocyanate-reactive and acid groups, and optional additives like low molecular weight (meth)acrylates, which are then partially neutralized and reacted to achieve the desired properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If radiation-curable, water-dispersible polyurethane acrylates are used, then coating efficiency and curing speed are improved, but grain highlighting on wood substrates deteriorates
Solution Approach 1:
The patent changes the chemical parameters of the polyurethane acrylate by selecting specific components: (cyclo)aliphatic diols with molar mass <700 g/mol, polyesterdiols with Mw 700-2000 and acid number ≤20 mg KOH/g, and controlling the NCO:OH ratio between 0.95-1.05. These parameter changes optimize the balance between water dispersibility (for coating efficiency) and grain highlighting performance.
Solution Approach 2:
The invention creates a composite polyurethane acrylate system combining multiple components: isocyanates, diols, polyesterdiols, chain extenders, and hydrophilic modifiers. This composite approach allows simultaneous achievement of water dispersibility, grain highlighting, and smooth film formation that single-component systems cannot provide.
2Stability of the object's composition
If ionic centers (carboxylate or sulfonate groups) are introduced to improve water dispersibility, then water solubility is improved, but yellowing of varnishes occurs
Solution Approach 1:
The patent extracts the hydrophilic functionality from traditional ionic groups (carboxylate/sulfonate) and replaces it with alternative water-dispersing mechanisms through specific polyesterdiol selection and controlled neutralization with bases, eliminating the yellowing problem while maintaining water dispersibility.
Solution Approach 2:
The invention changes the chemical nature of the hydrophilic groups by using polyesterdiols with controlled acid numbers (≤20 mg KOH/g) and neutralizing them to control the degree of ionization, thereby achieving water dispersibility without the severe yellowing associated with high concentrations of traditional ionic groups.
3Reliability
If molar mass is increased to reduce film stickiness, then film stability is improved, but grain highlighting capability deteriorates
Solution Approach 1:
The patent optimizes the molar mass parameters within specific ranges: diols <700 g/mol, polyesterdiols 700-2000 g/mol, and controls the overall polymer structure through NCO:OH ratio (0.95-1.05). This parameter optimization achieves the balance between sufficient molar mass for film stability and appropriate molecular weight for grain highlighting.
Solution Approach 2:
The polyurethane acrylate is segmented into different functional blocks: soft segments from diols providing flexibility and grain highlighting, hard segments from isocyanates providing strength and film stability, and hydrophilic segments from polyesterdiols providing water dispersibility. This segmentation allows each component to contribute its optimal properties without compromising the others.
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 resulting formulations demonstrate excellent grain highlighting, wet transparency, and form smooth, full, and optically transparent films on wood substrates, suitable for coating wood and wood-containing materials.
Implementation Method 1
radiation-curing, water-dispersible polyurethane (meth)acrylates
Data Source
AI summary
The present invention describes radiation-curable, water-dispersible polyurethane acrylates which feature good grain highlighting, their use, and the method for producing them.