Hydrophobic Polyurethane Composition With Adjustable Pot Life
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Solution Overview
Problem
Hydrophobic two-component polyurethane compositions face challenges in achieving a long, adjustable pot life while ensuring rapid curing and excellent mechanical properties, particularly when using catalyst systems that promote rapid curing.
Innovation Solution
A polyurethane composition comprising a mixture of hydrophobic and hydrophilic polyols, a compound with thiol groups, and a metal catalyst that forms thio complexes, with a specific molar ratio of thiol groups to metal atoms, allowing for a long pot life followed by rapid curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high proportions of isocyanates are used to achieve rapid curing and high mechanical properties, then curing speed and strength are improved, but pot life becomes too short for practical use
Solution Approach 1:
A catalyst system comprising a metal catalyst and a thiol compound is introduced as an intermediary substance. The thiol compound acts as a mediator that temporarily binds to the metal catalyst, forming a thio-complex that controls the reaction rate. This allows the system to maintain a long pot life during storage and handling while enabling rapid curing after application, thus resolving the contradiction between prolonged pot life and fast curing speed.
Solution Approach 2:
The invention changes the chemical parameters of the catalyst system by introducing a thiol compound with specific molecular weight (50-500 g/mol) and thiol group content (0.1-5 wt%). This parameter modification allows the catalyst to exhibit different reactivity characteristics: low reactivity during storage (long pot life) and high reactivity after application (rapid curing), thereby resolving the contradiction between pot life duration and curing speed.
2Productivity
If catalyst systems are used to achieve rapid curing, then curing speed is improved, but the system becomes uncontrollably fast with much too short pot life
Solution Approach 1:
The thiol compound serves as a controllable intermediary that binds to the metal catalyst to form a thio-complex. This complexed state provides controlled, gradual reactivity rather than uncontrollable rapid reaction. The thiol compound acts as a rate-controlling agent that can be adjusted to provide the desired balance between pot life and curing speed, thereby improving controllability while maintaining productivity.
3Reliability
If hydrophobic polyols are used to achieve improved water resistance and adhesion, then aging resistance and adhesion are improved, but compatibility with catalyst systems for adjustable pot life becomes problematic
Solution Approach 1:
The thiol compound acts as a bridge or intermediary between the hydrophobic polyol system and the metal catalyst. It forms a thio-complex with the catalyst that is compatible with hydrophobic environments, allowing the catalyst system to function effectively with hydrophobic polyols while maintaining the desired pot life adjustability and water resistance properties.
Solution Approach 2:
The invention creates a composite catalyst system combining metal catalyst with thiol compound, which together form a thio-complex that is compatible with hydrophobic polyols. This composite approach allows the system to maintain both the water resistance provided by hydrophobic polyols and the catalytic activity needed for controlled curing, resolving the compatibility issue.
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 composition achieves high strength and elasticity with a long, adjustable pot life, enabling efficient processing and rapid development of mechanical properties, suitable for structural adhesives and composite materials.
Implementation Method 1
a catalyst system comprising a metal catalyst and compounds containing thiol groups, which allow an adjustable, long pot life and then very rapid curing of the composition
Implementation Method 2
a compound having at least one thiol group in the first component and a polyisocyanate in the second component... a metal catalyst that is able to form thio complexes
Implementation Method 3
Two-component polyurethane compositions based on polyols and polyisocyanates... cure to form a polymeric network
Data Source
AI summary
A polyurethane composition includes first and second components, wherein the first component contains between 30% and 99% by weight of a polyol mixture including 100 parts by weight of at least one hydrophobic polyol, 10 to 75 parts by weight of at least one hydrophilic polyol, 0 to 25 parts by weight of at least one diol having two hydroxyl groups linked via a C2 to C9 carbon chain; and also at least one compound having at least one thiol group; and the second component includes at least one polyisocyanate, wherein one of the two components additionally includes at least one metal catalyst for the reaction of hydroxyl groups and isocyanate groups that is able to form thio complexes and the molar ratio of all the thiol groups in the at least one compound to all metal atoms in the at least one metal catalyst is between 1:1 and 250:1.