Bismuth Catalyst for Bubble-Free Polyurethane Curing
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Solution Overview
Problem
Existing polyurethane catalysts suffer from low selectivity towards urethanization reactions, leading to bubble formation, reduced mechanical strength, and thermal instability, while also being sensitive to moisture and requiring organic solvents for application.
Innovation Solution
A bismuth-containing catalyst formed by reacting bismuth(III) salts or complexes with 1,3-ketoamides, which provides high catalytic activity, selectivity, and stability, maintaining activity in the presence of residual water and at elevated temperatures, and is easily soluble in polyurethane starting materials without the need for volatile organic solvents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional catalysts (tertiary amines, dialkyl tin carboxylates) are used to accelerate curing, then curing speed is improved, but bubble formation increases due to low selectivity towards urethanization reaction
Solution Approach 1:
The patent changes the chemical parameters of the catalyst by using bismuth(III) carboxylates with specific carboxylate groups (aliphatic, alicyclic, or aromatic with 6-12 carbon atoms). This parameter change in catalyst structure provides high selectivity for urethanization reaction while maintaining fast curing speed, thereby eliminating bubble formation without sacrificing productivity.
2Productivity
If bismuth(III) tricarboxylates are used for high catalytic activity and selectivity, then urethanization reaction is promoted, but catalyst deactivation occurs rapidly during storage due to moisture sensitivity
Solution Approach 1:
The patent applies local quality by selecting specific carboxylate groups with 6-12 carbon atoms (aliphatic, alicyclic, or aromatic). These specific local chemical structures provide hydrophobic character that protects the bismuth center from moisture attack, thereby maintaining both high catalytic activity and storage stability simultaneously.
Solution Approach 2:
The patent creates a composite catalyst structure combining bismuth(III) center with specific carboxylate ligands. This composite structure integrates the high catalytic activity of bismuth with the moisture resistance of the carboxylate groups, achieving both high productivity and reliability during storage.
3Productivity
If catalysts are used that are solid at room temperature, then catalytic activity can be maintained, but solubility in polyurethane starting materials is poor requiring organic solvents
Solution Approach 1:
The patent changes the physical parameters of the catalyst by selecting carboxylate groups with 6-12 carbon atoms, which increase the lipophilic character of the molecule. This parameter change transforms the catalyst into a liquid at room temperature or a low-melting solid with excellent solubility in polyurethane starting materials and plasticizers, eliminating the need for organic solvents while maintaining catalytic activity.
4Productivity
If dialkyl tin carboxylates are used as catalysts, then curing speed is improved, but thermal resistance of cured composition decreases due to depolymerization
Solution Approach 1:
The patent changes the chemical composition parameter by replacing tin with bismuth and using specific carboxylate groups. This parameter change results in a catalyst that maintains high curing speed but does not cause depolymerization under thermal load, thereby preserving both productivity and thermal resistance of the cured composition.
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 catalyst enables rapid and bubble-free curing of polyurethane compositions with improved mechanical strength and thermal resistance, maintaining activity over extended storage periods and allowing solvent-free systems at room temperature.
Implementation Method 1
To accelerate the curing process, catalysts are admixed. While a plurality of polyurethane catalysts are known, the majority of them are not particularly selective with respect to the urethanization reaction
Implementation Method 2
The residual water content of the polyurethane composition additionally causes catalysts that are sensitive to hydrolysis, such as bismuth carboxylates, to become deactivated if the composition is kept for an extended period prior to use (storage)
Data Source
AI summary
Invention relates to bismuth-containing catalysts, obtainable by reacting at least one bismuth(III) salt or bismuth(III) complex with at least one 1,3-ketoamide with the formula (I). Such complex compounds are suited in particular as catalysts for one- and two-component polyurethane compositions. The invention further relates to two-component polyurethane compositions, including at least one polyisocyanate as the first component, at least one polyol as the second component, and at least one such bismuth-containing catalyst. The invention further relates one-component polyurethane compositions, including at least one polyurethane prepolymer having isocyanate groups, produced from at least one polyisocyanate with at least one polyol, and one such bismuth-containing catalyst. The invention also relates to various uses of the aforementioned polyurethane compositions.