Cellulose Ester Ophthalmic Articles Hexanedioate Plasticizer Toughness
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Solution Overview
Problem
Commercially available cellulose esters used in ophthalmic articles, such as eyeglass frames, face challenges with high levels of monomeric plasticizers that decrease Heat Deflection Temperature (HDT) below 90°C, leading to deformation and distortion due to high temperatures, and result in unacceptable plasticizer exudation during processing and use.
Innovation Solution
Cellulose ester compositions with reduced monomeric plasticizer levels are enhanced by incorporating hexanedioate plasticizers, which maintain or exceed HDT above 90°C, providing improved toughness, clarity, and dimensional stability, while minimizing creep deflection and plasticizer exudation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high levels of monomeric plasticizer are added to cellulose ester compositions, then toughness is improved, but Heat Deflection Temperature decreases below 90°C and dimensional stability deteriorates
Solution Approach 1:
The patent changes the chemical parameter of the plasticizer from conventional monomeric types to hexanedioate plasticizers, which have different molecular structure and properties. This parameter change allows achieving the desired toughness while maintaining HDT above 90°C, as the hexanedioate plasticizers provide effective plasticization at lower concentrations without excessively lowering the glass transition temperature
Solution Approach 2:
The patent creates a composite material system combining cellulose ester with specific hexanedioate plasticizers (such as hexanedioic acid diester or polyethylene glycol hexanedioate). This composite approach allows synergistic effects where the hexanedioate plasticizer enhances toughness while the cellulose ester matrix maintains high HDT, resolving the contradiction between toughness and temperature resistance
2Strength
If high levels of monomeric plasticizer are added to cellulose ester compositions, then toughness is improved, but dimensional stability deteriorates due to deformation and distortion in high-temperature environments
Solution Approach 1:
The patent changes the plasticizer type parameter to hexanedioate plasticizers, which have higher boiling points and better thermal stability compared to conventional monomeric plasticizers. This parameter change prevents plasticizer migration and degradation at high temperatures, thereby maintaining dimensional stability while still providing adequate toughness
Solution Approach 2:
The patent replaces conventional monomeric plasticizers that are prone to exudation and degradation with hexanedioate plasticizers that offer long-term stability. The hexanedioate plasticizers remain stably bound in the cellulose ester matrix, preventing the short-living behavior of conventional plasticizers that lead to deformation over time
3Ease of manufacture
If conventional monomeric plasticizers are used in cellulose ester molded articles, then processing is facilitated, but plasticizer exudation occurs during processing and use
Solution Approach 1:
The patent changes the molecular weight parameter of the plasticizer by using hexanedioate plasticizers with higher molecular weight compared to conventional monomeric plasticizers. This parameter change reduces volatility and exudation tendency while maintaining melt processability, as the higher molecular weight plasticizers remain stably dispersed in the cellulose ester matrix during processing and use
Data Source
AI summary
Ophthalmic articles made from a cellulose ester composition is provided, the cellulose ester composition comprising at least one cellulose ester and at least one hexanedioate plasticizer in amounts to provide an ophthalmic article having a high glass transition temperature and dimensional stability.