Sulfur-Containing Plastic Lens Production via Intermediary Catalyst
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Solution Overview
Problem
Existing processes for producing plastic lenses with high refractive index and Abbe number often compromise weatherability due to the need for high amounts of reaction-promoting substances, particularly when using aromatic heterocyclic compounds like imidazole-based substances, which decrease light resistance.
Innovation Solution
A process involving the preparation of a prepolymer by reacting compounds with epoxy groups and sulfur in the presence of a vulcanization catalyst, followed by adding the remaining polythiol compound, reduces the amount of catalyst needed, thereby enhancing weatherability while maintaining high refractive index and Abbe number.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high amounts of reaction-promoting substances (aromatic heterocyclic compounds like imidazole-based substances) are used to promote polymerization, then polymerization reaction efficiency is improved, but weatherability (light resistance) deteriorates due to degradation and discoloration
Solution Approach 1:
The patent uses a sulfonium salt or iodonium salt as an intermediary catalyst to mediate the polymerization reaction between the compound with epoxy group and sulfur. This intermediary catalyst promotes the reaction efficiently while being less harmful to weatherability compared to aromatic heterocyclic compounds. The intermediary transfers the catalytic function while minimizing degradation and discoloration of the final product.
Solution Approach 2:
The patent changes the chemical parameter of the catalyst from aromatic heterocyclic compounds (imidazole-based substances) to sulfonium salts or iodonium salts. This parameter change in catalyst type fundamentally alters the reaction pathway to one that maintains polymerization efficiency while preserving the optical properties and weatherability of the plastic lens material.
2Manufacturing precision
If high refractive index and Abbe number are achieved through sulfur-containing compounds, then optical performance is improved, but uniformity and transparency deteriorate due to separation or incomplete dissolution of solid inorganic compounds
Solution Approach 1:
The patent changes the physical state parameter of the sulfur source from solid inorganic compounds to molecularly dispersed sulfur atoms incorporated during polymerization. This parameter change allows sulfur to be uniformly distributed at the molecular level within the polymer matrix, achieving both high optical performance and compositional uniformity without separation or dissolution issues.
Solution Approach 2:
The patent replaces the mechanical mixing approach (which fails to achieve uniform dispersion of solid inorganic compounds) with a chemical incorporation approach where sulfur atoms are integrated into the polymer chain during the polymerization reaction. This substitution of the sulfur introduction mechanism ensures molecular-level uniformity.
3Manufacturing precision
If conventional polymerization processes are used with sulfur and epoxy compounds, then refractive index is increased, but weatherability deteriorates due to degradation and discoloration
Solution Approach 1:
The patent introduces sulfonium salts or iodonium salts as intermediary catalysts that facilitate the polymerization between epoxy compounds and sulfur without causing significant degradation or discoloration. These intermediaries enable the chemical reaction to proceed while preserving the optical clarity and weatherability of the material.
Solution Approach 2:
The patent converts the potential harm of sulfur incorporation (which can cause discoloration and degradation) into a benefit by using controlled polymerization with specific catalysts. The sulfur, which could otherwise harm weatherability, is instead incorporated in a controlled manner that enhances refractive index while maintaining excellent weatherability through the chosen polymerization pathway.
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 results in plastic lenses with excellent weatherability, high refractive index, and transparency, suppressing degradation and discoloration, and facilitating uniform polymerization with improved mechanical strength.
Implementation Method 1
preparing a prepolymer comprising sulfur by bringing at least one compound having epithio group, sulfur and a portion of a polythiol compound into reaction with each other in the presence of a vulcanization catalyst
Implementation Method 2
adding the rest of the polythiol compound to the prepared prepolymer comprising sulfur and allowing the polymerization to proceed
Data Source
AI summary
A process for producing a plastic lens which comprises preparing a prepolymer comprising sulfur by bringing at least one compound having epithio group, sulfur and a portion of a polythiol compound into reaction with each other and, thereafter, adding rest of the polythiol compound to the prepared prepolymer comprising sulfur and allowing polymerization to proceed. A plastic lens of excellent quality which exhibits excellent weatherability in combination with a great refractive index, a great Abbe number and excellent transparency is produced.