High Molecular Weight Polycarbodiimide via Two-Solvent Polymerization
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Solution Overview
Problem
Conventional methods for producing polycarbodiimides result in low molecular weight polymers due to precipitation and gelation in solvents, limiting their applications and requiring processing in powder form, which restricts their use and handling.
Innovation Solution
A method involving the polymerization of toluene diisocyanate with a carbodiimidization catalyst in a first solvent, followed by the introduction of a second solvent, allowing continued polymerization to achieve high molecular weight polycarbodiimides suitable for diverse applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional methods use a single solvent for polymerization, then the process is simple, but the polycarbodiimide precipitates and gels at low molecular weight (1,000-3,000), limiting further polymerization
Solution Approach 1:
The patent divides the polymerization process into two distinct stages using different solvents: a first solvent (chlorinated aliphatic hydrocarbon) for initial polymerization, and a second solvent (chlorinated aromatic compound) for continued polymerization after adding the reaction mixture. This segmentation allows the process to overcome the molecular weight limitation imposed by precipitation in a single solvent system.
Solution Approach 2:
The patent changes the solvent parameter between polymerization stages. The first solvent (boiling point 50-150°C) is used initially, then the reaction mixture is combined with a second solvent (boiling point 80-200°C) that provides different solubility characteristics, allowing polymerization to continue beyond the point where precipitation would normally occur in a single solvent system.
2Ease of operation
If polycarbodiimide is produced in solution, then processing and storage are easier, but conventional methods cause precipitation and gelation, preventing solution form handling
Solution Approach 1:
The patent ensures continuous polymerization action by adding the second solvent after the initial reaction mixture is formed. This allows the polymerization process to continue uninterrupted in solution form, producing high molecular weight polycarbodiimide that remains soluble and can be handled, stored, and processed in solution rather than requiring precipitation and powder handling.
3Strength
If polymerization continues to high molecular weight, then physical properties improve, but precipitation and gelation cease polymerization at low molecular weight
Solution Approach 1:
The patent uses a two-solvent system where the first solvent acts as an initial reaction medium and the second solvent acts as an intermediary that prevents precipitation. The second solvent (chlorinated aromatic compound with higher boiling point) serves as a mediator that maintains solubility during extended polymerization, allowing the system to achieve high molecular weights without the gelation that would otherwise terminate the reaction.
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 produces high molecular weight polycarbodiimides with excellent physical properties, enabling their use in various applications like synthetic fibers, automotive, and aerospace, and allows for processing and storage in solution form.
Implementation Method 1
an organic isocyanate, such as an aromatic isocyanate, is polymerized in the presence of a carbodiimidization catalyst
Implementation Method 2
the organic isocyanate is polymerized in the presence of the carbodiimidization catalyst while disposed in a solvent such that the polycarbodiimide is produced in solution
Implementation Method 3
the polycarbodiimides precipitate and/or gel in the solvent once the polycarbodiimides reach a certain molecular weight
Data Source
AI summary
A method of producing the high molecular weight polycarbodiimide comprises the steps of providing an isocyanate component comprising toluene diisocyanate (TDI), a carbodiimidization catalyst, and a first solvent. The method further comprises the step of polymerizing the isocyanate component in the first solvent and in the presence of the carbodiimidization catalyst to produce a reaction mixture including at least one carbodiimide compound and the first solvent. In addition, the method comprises the step of combining a second solvent and the reaction mixture. Finally, the method comprises the step of polymerizing the at least one carbodiimide compound for a second period of time in the first and second solvents and in the presence of the carbodiimidization catalyst to produce the high molecular weight polycarbodiimide.