Continuous Polyisocyanate Dilution for Low-Viscosity Clear Solutions
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Solution Overview
Problem
Existing polyisocyanate compositions from toluene diisocyanate are highly viscous, prone to crystallization, and have incomplete solubility in organic solvents, leading to cloudy solutions that limit their use in paints and adhesives, while also containing high levels of free diisocyanate, which are toxicologically concerning.
Innovation Solution
A process involving continuous dilution of polyisocyanate compositions with solvents inert to isocyanate groups in multiple stages, combined with thermal separation to remove unreacted toluene diisocyanate, results in low-viscosity, turbidity-stable solutions with high isocyanate group content and low color number.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If polyisocyanate compositions are synthesized from toluene diisocyanate, then high isocyanate group content is achieved, but viscosity becomes highly viscous and solubility becomes incomplete
Solution Approach 1:
The patent applies parameter changes by carefully controlling reaction temperature (60-80°C), catalyst dosage (0.01-5 wt%), and reaction time to optimize the balance between isocyanate group content and viscosity. By adjusting these parameters, the process achieves high NCO content while maintaining acceptable viscosity and solubility characteristics
Solution Approach 2:
The patent uses catalysts as intermediaries to facilitate the trimerization reaction of toluene diisocyanate. Specific catalysts (such as organometallic compounds or organic bases) are employed to control the reaction rate and product distribution, enabling high isocyanate group content to be achieved without excessive viscosity increase
2Productivity
If polyisocyanate compositions are used in paints and adhesives, then crosslinking efficiency is improved, but solvent content must be increased to reduce viscosity
Solution Approach 1:
The patent optimizes the solids content parameter to range from 30-70 wt%, which allows the composition to maintain low enough viscosity for practical application while preserving high crosslinking efficiency. This parameter optimization eliminates the need for excessive solvent addition
3Quantity of substance
If toluene diisocyanate is converted to polyisocyanurate, then isocyanate group content increases, but crystallization tendency increases and solubility decreases
Solution Approach 1:
The patent controls the reaction temperature within 60-80°C and limits the isocyanate group content to 20-45 wt% to prevent excessive crystallization. These parameter controls maintain the product in a stable, soluble state while still achieving high isocyanate functionality
Solution Approach 2:
The patent produces composite polyisocyanate compositions containing a mixture of cyclic trimer structures and oligomeric isocyanurates. This composite structure, achieved through controlled reaction conditions, prevents complete crystallization and improves solubility in common organic solvents while maintaining high isocyanate group content
4Productivity
If polyisocyanate compositions are produced with high isocyanate group content, then process efficiency is improved, but color number increases
Solution Approach 1:
The patent optimizes reaction temperature (60-80°C) and catalyst selection to minimize side reactions that produce colored byproducts. By carefully controlling these parameters, the process achieves high isocyanate group content while maintaining low color numbers suitable for clear applications
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 produces polyisocyanate compositions with low viscosity, high isocyanate group content, and minimal turbidity, suitable for clear applications, reducing solvent use and toxicity, and enhancing process efficiency and sustainability.
Implementation Method 1
continuous dilution of polyisocyanate compositions with solvents inert to isocyanate groups in multiple stages
Implementation Method 2
thermal separation to remove unreacted toluene diisocyanate
Data Source
AI summary
The invention relates to a method for producing a polyisocyanate composition, consisting of adding at least one solvent which is inert compared to isocyanate groups to at least one polyisocyanate, said method being characterised in that the addition of the solvent is carried out in one or more steps and at least one of these steps is continuous dilution. The invention also relates to the polyisocyanate compositions obtained according to said method, to the use of the polyisocyanate compositions, a two-component system containing the polyisocyanate composition and to composite systems produced using the two-component system.