Low-Viscosity Water-Dilutable Urethane (Meth)acrylates Preparation
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Solution Overview
Problem
Current water-dilutable radiation-curable polyurethane systems have low solids content, high viscosity, and poor chemical resistance, storage stability, and UV reactivity, limiting their application in coatings and adhesives.
Innovation Solution
A process for preparing low-viscosity, water-dilutable polyurethane (meth)acrylates using oligomeric polyisocyanates, polyoxyalkylene mono-ols, hydroxyalkyl (meth)acrylates, and partially esterified polyoxyalkylene polyols, with specific reaction conditions to achieve high solids content and improved UV reactivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If polyurethane dispersions with water-adjusted viscosity are used, then water dilutability is improved, but solids content decreases and drying time increases
Solution Approach 1:
The invention changes the chemical structure parameters of the polyurethane by using polyethylene oxide polyols with specific molecular weights and ratios, and by controlling the NCO index during synthesis. This enables the coating composition to achieve both high solids content (≥80 wt.%) and good water dilutability without requiring high water content for viscosity adjustment
Solution Approach 2:
The invention creates a composite polyurethane system combining polyethylene oxide polyols with specific hydroxyl values (18-56 mg KOH/g) and regular polyols, crosslinked through isocyanate groups to form a network structure that provides both water compatibility and high solids content stability
2Quantity of substance
If polyethylene oxide polyol-based polyurethanes are used for high solids content, then solids content increases, but UV reactivity and storage stability decrease
Solution Approach 1:
The invention introduces local reactive sites by incorporating compounds with carboxyl groups (component C) and isocyanate groups (component D) at specific locations in the polyurethane chain. These localized functional groups provide UV reactivity and crosslinking capability without requiring high overall water content, enabling solids content ≥80 wt.% with maintained reactivity
Solution Approach 2:
The invention optimizes the hydroxyl value parameter of polyethylene oxide polyols to a specific range (18-56 mg KOH/g) and controls the NCO index (0.8-1.5) to balance polymer chain density and reactivity, achieving high solids content while maintaining adequate UV reactivity through controlled molecular architecture
3Ease of operation
If high water content is used for viscosity adjustment, then water dilutability is improved, but application thickness is reduced and drying time increases
Solution Approach 1:
The invention changes the fundamental approach to viscosity control by synthesizing polyurethanes with inherently low viscosity through specific polyol selection (hydroxyl value 18-56 mg KOH/g) and molecular weight distribution, enabling viscosity adjustment with minimal water (≤20 wt.%) while maintaining application thickness and reducing drying time
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 polyurethane (meth)acrylates have low viscosity, high solids content, enhanced chemical resistance, improved storage stability, and increased UV reactivity, making them suitable for coatings, adhesives, and other applications.
Implementation Method 1
The curing of coating systems carrying activated double bonds by actinic radiation is known and is established in industry. Actinic radiation is understood as meaning electromagnetic, ionizing radiation, in particular electron beams, UV rays and visible light
Data Source
AI summary
The present invention relates to a process for the preparation of highly reactive, low-viscosity and water-dilutable polyisocyanate reaction products which contain activated groups which react, by polymerization, with ethylenically unsaturated compounds under the action of actinic radiation. The present invention furthermore relates to a process for the preparation of such products and their use.