Radiation Curable Polyurethane Dispersion Water Release Stability
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Solution Overview
Problem
Radiation curable polyurethane dispersions prepared from hydroxyl-terminated polyurethane prepolymers using solvent-free processes result in films with poor water release properties, contrasting with isocyanate-terminated prepolymers which are sensitive to humidity and have lower storage stability.
Innovation Solution
The development of ethylenically unsaturated hydroxyl-terminated polyurethanes synthesized by reacting ethylenically unsaturated compounds with saturated alcohols and polyisocyanates, avoiding the use of solvents and ensuring a higher number of free hydroxyl groups compared to isocyanate groups, enhancing dispersibility and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If hydroxyl-terminated polyurethane prepolymers are used in solvent-free processes, then storage stability and dispersibility are improved, but water release properties deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the polyurethane by incorporating specific saturated polyester polyols (B2) and saturated polycarbonate polyols (B22) into the hydroxyl-terminated polyurethane structure. This modifies the polymer properties to simultaneously achieve good storage stability and excellent water release properties, resolving the contradiction between these two performance aspects.
Solution Approach 2:
The patent creates a composite polyurethane system by combining hydroxyl-terminated polyurethane with specific saturated polyester polyols and saturated polycarbonate polyols. This composite structure integrates the advantages of each component: the hydroxyl-terminated polyurethane provides storage stability and dispersibility, while the saturated polyester and polycarbonate polyols contribute to water release properties, thereby resolving the technical contradiction.
2Object-generated harmful factors
If isocyanate-terminated prepolymers are used, then water release properties are improved, but sensitivity to humidity and storage stability deteriorate
Solution Approach 1:
Instead of using isocyanate-terminated prepolymers as conventionally done, the patent inverts the approach by using hydroxyl-terminated prepolymers with specific polyester and polycarbonate polyols. This inversion allows achieving both good water release properties and storage stability, eliminating the need to choose between these two properties.
Solution Approach 2:
The patent changes the terminal functional groups from isocyanate to hydroxyl, and modifies the polyol composition to include saturated polyester and polycarbonate polyols. This parameter change fundamentally alters the polymer's interaction with water and humidity, enabling simultaneous achievement of water release properties and storage stability without the sensitivity issues of isocyanate-terminated systems.
3Ease of operation
If solvents are used to reduce viscosity, then processability is improved, but need to remove solvents and production cost deteriorate
Solution Approach 1:
The patent extracts and eliminates the solvent step from the production process entirely. By formulating the polyurethane dispersion without requiring solvent addition and subsequent removal, the process becomes simpler and more cost-effective. The saturated polyester and polycarbonate polyols in the composition provide sufficient flexibility and processability without needing external solvents, thereby resolving the contradiction between processability and production cost.
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 dispersions exhibit excellent water release properties and improved storage stability, outperforming hydroxyl-terminated polyurethane films while reducing the need for solvents and minimizing residual isocyanates, thus offering safer and more cost-effective production.
Implementation Method 1
radiation curable compositions comprising a high molecular weight ethylenically unsaturated polyurethane (A) and a low molecular weight ethylenically unsaturated polyurethane (B)
Data Source
AI summary
The present invention provides for an ethylenically unsaturated hydroxyl-terminated polyurethane (I) obtained by reacting (i) at least one ethylenically unsaturated compound (A) containing at least two reactive groups capable of reacting with isocyanate groups and at least one ethylenically unsaturated group; with (ii) at least one saturated alcohol component (B) comprising: (iia) at least one saturated hydroxylated compound (B1) containing hydrophilic groups capable of rendering the polyurethane dispersible in aqueous medium either directly or after the reaction with a neutralizing agent to provide a salt, and at least one compound (B2) that is selected from saturated polyester polyols (B21) and/or from saturated polycarbonate polyols (B22); and/or (iib) at least one compound (B3) that is selected from saturated polyester polyols (B31) containing compound (B1) moieties and/or from saturated polycarbonate polyols (B32) containing compound (B1) moieties; and, optionally, one or more of compounds (B1) and/or (B2); (iii) optionally, at least one ethylenically unsaturated compound (C) containing essentially one reactive group capable of reacting with isocyanate groups; and with (iv) at least one polyisocyanate (D). The present invention further relates to radiation curable coating compositions comprising same, to their preparation process and their uses.