Polythiourethane Transparent Substrate Curing With Latent Catalysts
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Solution Overview
Problem
Existing fast cure processes for polythiourethane based substrates suffer from a short pot life of the polymerizable mixture, leading to constraints in mixing and filling steps, and often result in optical defects such as bubbles and striations.
Innovation Solution
A method using latent, heat-activatable catalysts is introduced, allowing for a longer pot life and controlled polymerization, reducing the likelihood of optical defects by blending the catalyst in an inactive form and activating it during the curing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a highly reactive catalyst is used to shorten curing time, then productivity is improved, but the pot life of the polymerizable mixture becomes too short allowing proper mixing and filling
Solution Approach 1:
The catalyst is pre-associated with a blocking agent (such as a carboxylic acid or isocyanate) to form a stable complex that is stored in advance. This preliminary action allows the catalyst to be prepared and stored without being active, and then activated only when needed during the curing process, thereby extending the pot life while maintaining fast curing capability.
Solution Approach 2:
A blocking agent acts as an intermediary between the catalyst and the polymerizable mixture. The blocking agent temporarily deactivates the catalyst by forming a stable complex, preventing premature polymerization. This intermediary allows the mixture to remain stable during storage and handling, then releases the catalyst activity under controlled conditions during curing.
2Use of energy by moving object
If monomers are pre-reacted to form oligomers to reduce curing time, then energy release is controlled, but the mixture becomes highly viscous requiring rapid processing
Solution Approach 1:
The viscosity of the polymerizable mixture is controlled by adjusting the degree of pre-reaction to form oligomers. By optimizing the balance between monomer conversion and oligomer formation, the mixture maintains manageable viscosity for proper mixing and filling, while still benefiting from the energy release control that prevents runaway polymerization reactions.
3Productivity
If the catalyst is activated immediately upon mixing, then polymerization proceeds rapidly, but optical defects such as bubbles and striations occur
Solution Approach 1:
The catalyst is prepared in an inactive state and stored with the polymerizable mixture in advance. The activation step is postponed until the mixture is properly degassed and ready for curing, ensuring that rapid polymerization occurs only under controlled conditions that prevent optical defects.
Solution Approach 2:
The blocking agent serves as an intermediary that prevents premature catalyst activation. This allows sufficient time for degassing and proper mixture preparation, eliminating bubbles and striations before the rapid polymerization phase begins, thus ensuring high optical quality.
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 method enables a stable and controlled polymerization reaction, minimizing reactivity during mixing and filling, thereby reducing the risk of clogging and optical defects, while maintaining a high level of mixing integrity.
Implementation Method 1
at least one latent catalyst that is heat-activatable is used in the process prior to curing step 4), and said catalyst is subsequently activated
Implementation Method 2
curing step 4) consisting in polymerizing said mixture of first and second components A and B to form the polythiourethane based transparent substrate
Data Source
AI summary
The present invention relates to a method of fast curing a polythiourethane based transparent casted substrate. comprising in a preferred embodiment providing a first component A comprising a polythiourethane pre-polymer Al having isocyanate or isothiocyanate end groups. providing a second component B comprising a polythiourethane pre-polymer BI having thiol end groups. mixing together first and second components A and B and filling a molding cavity of a casting mold assembly with the resulting mixture. curing said mixture to obtain a transparent substrate, wherein at least one latent catalyst that is heat-activatable is added in the process prior to curing step 4). and said catalyst is subsequently activated to accelerate the polymerization reaction forming the polythiourethane based transparent substrate.