Polyurethane NCO End Groups Catalyst System
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Solution Overview
Problem
Current polyurethane-based sealants face challenges due to the toxicological risks of tin-based catalysts and the instability and increased viscosity of bismuth-based compositions over time, leading to deteriorated properties and limited storage stability.
Innovation Solution
A process involving the preparation of polyurethanes with NCO end groups using organometallic catalysts and tertiary amines, with controlled catalyst content, to create compositions that are safer, more stable, and exhibit improved adhesion and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If tin-based catalysts are used for polyaddition, then catalytic activity is high, but toxicological risks to man and environment increase
Solution Approach 1:
The patent replaces persistent toxic tin-based catalysts with alternative catalyst systems (organometallic catalysts like bismuth or zinc compounds, and/or tertiary amines) that offer adequate catalytic activity while presenting lower toxicological risks. The catalyst system is designed to fulfill the catalytic function without the long-term environmental persistence and toxicity associated with tin compounds.
Solution Approach 2:
The patent modifies the catalyst system parameters by transitioning from tin-based catalysts to alternative catalysts with different chemical properties. The total catalyst content is controlled at less than or equal to 10,000 ppm (preferably less than or equal to 1,000 ppm) to optimize the balance between catalytic activity and reduced toxicity, maintaining productivity while improving safety and environmental compatibility.
2Productivity
If bismuth-based catalysts are used at high concentrations, then catalytic activity is sufficient, but composition stability decreases and viscosity increases over time
Solution Approach 1:
The patent optimizes the catalyst concentration parameter by limiting the total catalyst content to less than or equal to 10,000 ppm (preferably less than or equal to 1,000 ppm). This controlled low concentration prevents excessive catalytic activity that would cause premature crosslinking and viscosity increase during storage, while still providing sufficient activity for the intended application. The patent also controls the NCO/OH ratio to be between 1.05 and 2.0 to prevent spontaneous crosslinking.
Solution Approach 2:
The patent uses a dual-catalyst system or controlled single-catalyst approach where the catalyst acts as an intermediary that can be precisely controlled in quantity and activity. By using organometallic catalysts and/or tertiary amines at controlled concentrations, the patent achieves sufficient catalytic activity for the polyaddition reaction while preventing unwanted side reactions and maintaining composition stability during storage.
3Object-affected harmful factors
If bismuth-based catalysts are used, then toxicological risks are reduced, but composition viscosity increases and adhesion properties deteriorate
Solution Approach 1:
The patent precisely controls the catalyst concentration parameter (total catalyst content less than or equal to 10,000 ppm, preferably less than or equal to 1,000 ppm) and the NCO/OH ratio (between 1.05 and 2.0) to prevent excessive crosslinking during storage. This controlled approach maintains adhesion properties and mechanical strength by avoiding premature gelation and viscosity increase, while still using safer alternative catalysts to reduce toxicological risks.
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 process results in polyurethane compositions that are environmentally friendly, stable over long storage periods, and maintain excellent mechanical and adhesion properties, suitable for use as adhesives, sealants, or surface coatings.
Implementation Method 1
preparation of a polyurethane having NCO end groups, comprising a stage of polyaddition of a composition of polyol(s) and of a composition of polyisocyanate(s), in the presence of at least one catalyst A chosen from the group consisting: of organometallic catalysts, with the exception of tin-based catalysts, of tertiary amines
Data Source
AI summary
The present invention relates to a method for producing a composition comprising at least one polyurethane with NCO end groups, and at least one catalyst B selected from among tertiary amines, said method comprising the following steps: a) production of a polyurethane with NCO end groups, comprising a step of polyaddition of a polyol composition and a polyisocyanate composition, in the presence of at least one catalyst A selected from the group consisting of—organo-metallic catalysts excluding tin-based catalysts, —tertiary amines, and—mixtures of same; and b) the addition of at least one catalyst B, selected from among tertiary amines, to the polyurethane with NCO end groups obtained in step a).