Tin-Free Polyurethane Acrylates via Bismuth Catalyst
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Aqueous radiation-curable polyurethane dispersions synthesized with conventional catalysts other than dibutyltin dilaurate (DBTL) often result in coarser particle patterns, sedimentation, and increased viscosity, and there is a need for tin-free alternatives that maintain the properties of DBTL-catalyzed systems.
Innovation Solution
The use of bismuth(III) salts in combination with acids having a pKa of less than 2.5 as catalysts for synthesizing tin-free radiation-curable polyurethane acrylates, which react with isocyanate-functional compounds to achieve weight-average molecular weights comparable to DBTL-catalyzed systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional catalysts other than DBTL are used for synthesizing aqueous radiation-curable polyurethane dispersions, then tin-free alternatives can be achieved, but the particle pattern becomes coarser, sedimentation occurs, and viscosity increases
Solution Approach 1:
The patent changes the catalytic parameters by introducing a specific catalyst system (bismuth(III) salt combined with a strong acid having pKa < 2.5) that modifies the reaction conditions to achieve fine particle formation without organotin compounds. This parameter change in catalyst composition and strength enables both tin-free synthesis and fine particle pattern (APS < 100 nm).
Solution Approach 2:
The patent employs a composite catalyst system combining bismuth(III) salt with strong acid (pKa < 2.5), where the synergistic interaction between these two components creates effective catalysis for polyurethane formation. This composite approach replaces DBTL while maintaining reaction efficiency and producing fine particles without sedimentation.
2Object-affected harmful factors
If conventional catalysts other than DBTL are used, then tin-free polyurethane can be produced, but molecular weight is reduced and properties deviate from DBTL-catalyzed systems
Solution Approach 1:
The patent adjusts the catalytic parameters by using bismuth(III) salt combined with strong acid (pKa < 2.5), which changes the reaction kinetics to achieve comparable molecular weights (MW ≥ 10,000 g/mol) to DBTL-catalyzed systems. This parameter optimization ensures that tin-free polyurethane maintains the desired molecular weight and physical properties.
3Object-affected harmful factors
If conventional catalysts other than DBTL are used, then tin-free alternatives are achieved, but the dispersion becomes more viscous and sedimentation occurs
Solution Approach 1:
The patent employs a composite catalyst system of bismuth(III) salt with strong acid (pKa < 2.5) that creates favorable reaction conditions for stable dispersion formation. This composite catalyst approach produces polyurethane with appropriate viscosity and prevents sedimentation, achieving both tin-free synthesis and high dispersion stability.
Solution Approach 2:
The patent modifies the catalytic parameters by introducing strong acid (pKa < 2.5) with the bismuth(III) salt, which changes the reaction conditions to produce dispersions with optimal viscosity and stability. This parameter change prevents sedimentation and maintains homogeneous dispersion even at elevated temperatures.
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
This approach produces polyurethane acrylates with comparable physical and use properties to DBTL-catalyzed systems, including suitable molecular weights and stability, without the use of organotin compounds.
Implementation Method 1
bismuth(III) salts in combination with acids having a pKa of less than 2.5 as catalysts for synthesizing tin-free radiation-curable polyurethane acrylates, which react with isocyanate-functional compounds
Implementation Method 2
bismuth(III) salts in combination with acids having a pKa of less than 2.5 as catalysts for synthesizing tin-free radiation-curable polyurethane acrylates
Implementation Method 3
aqueous radiation-curable coating compositions based on tin-free aqueous polyurethane dispersions
Data Source
AI summary
The present invention relates to radiation-curable coating compositions based on tin-free aqueous polyurethane dispersions based on polyurethane acrylates (i), characterized in that the polyurethane acrylate (i) comprises as builder componentsA) one or more compounds with at least one group which is reactive towards isocyanate and at least one unsaturated group which can undergo free radical polymerization,B) one or more compounds which differ from A) and have at least one group which is reactive towards isocyanate,C) one or more compounds with at least one group which is reactive towards isocyanate and additionally at least one group having a hydrophilizing action,D) one or more organic polyisocyanates,which are reacted in the presence ofF) bismuth(III) salt(s) andG) an acid having a pKa of <2.5,and a process for the preparation thereof, the use of the coating compositions as lacquers and/or adhesives, and objects and substrates provided with these lacquers and/or adhesives.