Urethane Optical Material Polymerization Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Urethane lenses face issues with deformation during secondary processing, low heat resistance, and color fading due to rapid polymerization and high reactivity when using aromatic isocyanates, leading to poor workability and strength in molded products.
Innovation Solution
A polymerizable composition comprising specific aromatic isocyanates, alcohols with a high secondary hydroxyl group ratio, and acid phosphate, along with a hindered amine compound, is used to control the polymerization rate and improve heat resistance and tinting properties, while suppressing striation and color fading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If aromatic isocyanates are used to improve heat resistance and tinting properties, then the reactivity and curing rate increase excessively, but the workability during preparation and casting deteriorates due to rapid viscosity increase
Solution Approach 1:
A hindered amine compound is introduced as an intermediary substance to moderate the reaction between aromatic isocyanates and alcohol. This mediator controls the curing rate and viscosity increase, allowing the system to maintain both heat resistance and workability during preparation and casting operations.
Solution Approach 2:
The reaction parameters are controlled by adjusting the type and amount of hindered amine compound used. By changing the chemical parameters of the system (introducing specific hindered amine compounds with controlled reactivity), the patent achieves optimal balance between heat resistance and workability during the curing process.
2Temperature
If aromatic isocyanates are used to enhance heat resistance, then the glass transition temperature increases, but the molded product exhibits striation and poor surface quality
Solution Approach 1:
The hindered amine compound acts as a mediator that ensures uniform distribution and controlled reaction progression throughout the molded product. This prevents localized overheating and uneven curing that would cause striation, while still achieving the desired glass transition temperature and heat resistance.
Solution Approach 2:
By carefully selecting and dosing hindered amine compounds, the patent optimizes the curing parameters to achieve uniform gelation throughout the material. This controlled parameter adjustment prevents the formation of striation and ensures high surface quality while maintaining the required thermal properties.
3Strength
If high reactivity is achieved through aromatic isocyanates to improve curing speed, then the strength increases, but the color fading after organic solvent cleaning worsens
Solution Approach 1:
The hindered amine compound serves as a protective intermediary that creates a more stable and uniform polymer network. This moderated curing approach reduces the formation of unstable chromophores and reactive groups that would otherwise cause color fading during subsequent solvent cleaning operations, while still achieving the required strength.
Solution Approach 2:
The patent adjusts the curing parameters by introducing hindered amine compounds to achieve optimal crosslinking density and network uniformity. This parameter optimization ensures that the material attains sufficient strength while developing better color stability that resists fading during organic solvent cleaning processes.
4Quantity of substance
If tolylene diisocyanate is used to reduce material cost, then the price decreases, but the molded product cannot be obtained due to excessively fast reaction speed
Solution Approach 1:
A hindered amine compound is introduced as a controlling intermediary that moderates the extremely fast reaction between tolylene diisocyanate and alcohol. This mediator extends the working time and allows the composition to be properly cast and molded, making the low-cost tolylene diisocyanate system manufacturable while maintaining cost effectiveness.
Solution Approach 2:
The patent modifies the reaction parameters by adding hindered amine compounds that control the gelation and curing kinetics. This parameter adjustment transforms the unmanageably fast reaction of tolylene diisocyanate into a controllable process that allows proper molding operations while maintaining the low material cost advantage.
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 composition achieves superior workability, heat resistance, strength, and tinting properties, with reduced striation and color fading, resulting in a balanced urethane molded product suitable for optical applications.
Implementation Method 1
a polymerizable composition for an optical material including: (A) one or more isocyanates having two or more isocyanato groups that contains an aromatic isocyanate; (B) one or more alcohols having two or more hydroxyl groups; and (C) an acid phosphate
Implementation Method 2
a urethane resin formed of isocyanate and alcohol which has a lower refractive index than the thiourethane resin
Data Source
Figure 1
AI summary
A polymerizable composition for an optical material includes: (A) one or more isocyanates having two or more isocyanato groups that contains an aromatic isocyanate; (B) one or more alcohols having two or more hydroxyl groups; and (C) an acid phosphate represented by the following formula (1), in which a ratio of the molar number of a secondary hydroxyl group to the total molar number of primary and secondary hydroxyl groups contained in the alcohol (B) is 50% or higher.