Thiourethane Optical Material pH Adjustment Whitening Prevention
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Solution Overview
Problem
The production of thiourethane-based optical materials using general-purpose isocyanate compounds often results in nonuniformity polymerization and whitening due to the miscibility issues and pH variations of polythiol compounds, leading to defective lenses and increased production costs.
Innovation Solution
Adjusting the pH of polythiol compounds to a range of 3.1 to 7 through washing with an inorganic acid followed by an aqueous basic solution, and using an organotin compound as a catalyst to enhance the reaction rate and miscibility with isocyanate compounds, thereby preventing whitening and nonuniformity polymerization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If general-purpose isocyanate compounds are used to produce thiourethane-based optical materials, then production cost is reduced, but nonuniformity polymerization and whitening occur due to miscibility issues
Solution Approach 1:
The patent adjusts the pH parameter of the polythiol compound to within the range of 3.1 to 7.0, which fundamentally changes the chemical environment and enables general-purpose isocyanate compounds to polymerize uniformly without causing whitening or nonuniformity polymerization, thus resolving the contradiction between cost reduction and manufacturing precision
Solution Approach 2:
The patent performs preliminary pH adjustment and washing treatments on the polythiol compound before polymerization to remove inorganic acid residues. This preliminary action prevents subsequent polymerization defects, allowing the use of cost-effective general-purpose isocyanate compounds while maintaining high polymerization uniformity
2Speed
If polythiol compounds with low pH are used, then reaction rate increases, but dissolution from pressure-sensitive adhesive tape and whitening occur
Solution Approach 1:
The patent optimizes the pH parameter to a specific range (3.1 to 7.0), which balances the reaction rate enhancement with the prevention of harmful effects. This parameter optimization ensures sufficient reactivity while preventing dissolution from pressure-sensitive adhesive tape and whitening at lens edges
Solution Approach 2:
The patent uses aqueous basic solutions as intermediaries to neutralize excess inorganic acid in the polythiol compound. This intermediary treatment adjusts the pH to an optimal range that maintains fast reaction rate while eliminating the harmful effects of excessive acidity on adhesive tape and lens edges
3Manufacturing precision
If inorganic acid treatment is applied to polythiol compounds, then purity is improved, but catalyst activity deteriorates due to remaining inorganic acid
Solution Approach 1:
The patent performs preliminary washing with aqueous basic solutions after inorganic acid treatment to remove residual inorganic acid. This preliminary action preserves the purity benefits of acid treatment while eliminating the harmful effect on catalyst activity, thus maintaining high polymerization productivity
Solution Approach 2:
The patent extracts and removes inorganic acid residues from the polythiol compound through washing with aqueous basic solutions. This extraction process retains the purity improvements from acid treatment while eliminating the remaining inorganic acid that would otherwise deteriorate catalyst activity and reduce polymerization rate
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
This approach produces high-quality thiourethane-based optical materials with stable quality, reduced defective rates, and improved optical properties by minimizing whitening and nonuniformity polymerization, while maintaining the cost-effectiveness of using general-purpose isocyanate compounds.
Implementation Method 1
an organotin compound as a catalyst to enhance the reaction rate
Implementation Method 2
adjusting the pH of a polythiol compound, wherein the product is obtained from an organic layer which is acquired after washing with an inorganic acid then washed several times with an aqueous basic solution
Data Source
AI summary
Disclosed is a method of producing a high-quality thiourethane-based optical material using a general-purpose polyisocyanate compound. According to the method, the pH of a polythiol compound is adjusted to 3.1 to 7 to prevent the occurrence of whitening, which is a problem of the prior art arising from the dissolution of a pressure-sensitive adhesive from a pressure-sensitive adhesive tape upon lens casting. The°pH adjustment increases the reaction rate of a resin composition including the polythiol compound. The use of the polythiol compound whose pH is adjusted enables the production of a thiourethane-based optical material that does not suffer from whitening at the edges of the optical lens and nonuniformity polymerization. Further disclosed are a resin composition for a thiourethane-based optical material, and an optical material including a resin produced by the method.