Diamine Composition Control for Clear Polythiourethane Lenses
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Solution Overview
Problem
Existing methods for producing isocyanates used in polythiourethane optical materials face challenges such as striae, cloudiness, yellowing, and low yield due to the use of hydrogen chloride gas and phosgene, which are environmentally hazardous and require complex handling processes.
Innovation Solution
A diamine composition containing benzylmonoamine with a methyl group in specific amounts, reacted with an aqueous hydrochloric acid solution and triphosgene, is used to prepare a diisocyanate composition, adjusting the b* value to enhance purity and yield while preventing striae and cloudiness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If m-XDI is used as a raw material for optical lenses, then mechanical properties and refractive index are improved, but optical characteristics deteriorate due to striae, cloudiness, or yellowing
Solution Approach 1:
The patent applies parameter changes by precisely controlling the isocyanate group content within a specific range (0.5-5.0 mmol/g) and adjusting the composition ratio of different xylylene diisocyanate isomers (o-XDI: 0.1-10 wt%, m-XDI: 85-99.9 wt%, p-XDI: 0.1-10 wt%). This optimization of chemical parameters resolves the contradiction by achieving both good mechanical properties and optical characteristics simultaneously
Solution Approach 2:
The patent uses a composite approach by combining multiple xylylene diisocyanate isomers in specific ratios rather than using a single isomer. This composite composition allows the material to benefit from the mechanical properties of m-XDI while mitigating its optical defects through the presence of o-XDI and p-XDI, thus resolving the contradiction between strength and manufacturing precision
2Productivity
If the direct method of reacting amine with phosgene gas is used, then isocyanate production efficiency is improved, but device complexity increases due to requiring multiple apparatuses
Solution Approach 1:
The patent merges the hydrochloride formation step and the isocyanate synthesis step into a single continuous process. The amine hydrochloride is directly reacted with triphosgene in the same reactor system, eliminating the need for separate apparatuses for hydrochloride formation and isocyanate synthesis, thus reducing device complexity while maintaining high productivity
Solution Approach 2:
The patent uses triphosgene as an intermediary reagent instead of gaseous phosgene. Triphosgene is a stable solid that decomposes to release phosgene in situ, serving as a safe intermediary that eliminates the need for complex gas handling apparatus while maintaining the efficiency of phosgene-based isocyanate synthesis
3Productivity
If hydrogen chloride gas is used to obtain amine hydrochloride, then reaction yield is improved, but harmful factors increase due to environmental hazards and complex handling
Solution Approach 1:
The patent uses triphosgene as an intermediary reagent that safely delivers the necessary phosgene functionality without requiring direct use of hazardous phosgene gas or hydrogen chloride gas. Triphosgene is a stable solid that can be handled safely and decomposes to release phosgene in situ under controlled conditions, thus eliminating environmental hazards while maintaining high reaction yield
Solution Approach 2:
The patent employs triphosgene, which decomposes completely during the reaction to release phosgene and harmless byproducts (HCl and CO2). This disposable reagent approach eliminates the need for complex gas handling and waste treatment systems, reducing environmental impact while maintaining high productivity
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 improves the optical and mechanical properties of polythiourethane lenses by enhancing yield, purity, and impact resistance, while avoiding the use of hazardous gases and reducing environmental impact.
Implementation Method 1
reacting a diamine composition with an aqueous hydrochloric acid solution to obtain a hydrochloride
Implementation Method 2
the hydrochloride is reacted with triphosgene to synthesize a diisocyanate composition
Data Source
AI summary
The diamine composition according to an embodiment of the present invention comprises a benzylmonoamine having a methyl group in an amount of 10 ppm to 2,000 ppm in the composition. When it is used for the preparation of a diisocyanate composition and an optical material, it is possible to improve the optical characteristics by preventing the occurrence of yellowing, striae, and cloudiness in the optical material and enhancing the mechanical properties such as impact resistance at the same time. Thus, the diisocyanate composition can be applied to the preparation of a plastic optical lens of high quality.