Silicone Hydrogel Lens Formulation for TPP Pot-Life Stability
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Solution Overview
Problem
Contact lens formulations containing triphenylphosphine (TPP) are susceptible to premature polymerization, especially when high levels of polymerizable siloxanes and hydrophilic N-vinyl amide monomers are present, leading to instability and lens defects during manufacturing.
Innovation Solution
Incorporating 1,4-bis[(2-methacryloxyethyl)amino]-9,10-anthraquinone (RB247) and optionally benzophenone UV-absorbing agents or benzotriazole HEVL absorbers into formulations with TPP to stabilize the mixture, enhancing stability and preventing premature polymerization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If triphenylphosphine (TPP) is added to silicone hydrogel contact lens formulations, then processability is improved and lens defects are reduced, but premature polymerization occurs leading to poor pot-life
Solution Approach 1:
The patent introduces RB247 as an intermediary substance that mediates between TPP and the monomer mixture. RB247 acts as a stabilizing agent that prevents premature polymerization while allowing TPP to maintain its processability benefits. The intermediary creates a balanced system where TPP can function as a processing aid without triggering unwanted polymerization reactions.
Solution Approach 2:
The patent modifies the chemical composition parameters by adding specific stabilizing agents (RB247, benzophenone UV-absorbing agents, and benzotriazole HEVL absorbers) to change the stability parameters of the formulation. This allows the system to maintain improved processability from TPP while achieving acceptable pot-life stability through adjusted chemical parameters.
2Reliability
If hydroquinone inhibitors are used to prevent premature polymerization, then stability is improved, but they become ineffective when oxygen is depleted
Solution Approach 1:
RB247 serves as an intermediary that provides oxygen-independent stabilization. Unlike hydroquinone inhibitors that require oxygen to function, RB247 and related stabilizing agents maintain their inhibitory effect on polymerization regardless of oxygen presence, making the formulation more adaptable to varying oxygen conditions during storage and processing.
Solution Approach 2:
The patent changes the inhibition mechanism parameter from oxygen-dependent (hydroquinone) to oxygen-independent (RB247, benzophenone, benzotriazole). This parameter change allows the formulation to maintain stability across different oxygen environments, improving both reliability and adaptability simultaneously.
3Manufacturing precision
If high levels of polymerizable siloxane and hydrophilic N-vinyl amide monomers are combined, then desired lens properties are achieved, but susceptibility to premature polymerization increases
Solution Approach 1:
The patent introduces multiple stabilizing agents as intermediaries that specifically protect the combination of polymerizable siloxane and hydrophilic N-vinyl amide monomers from premature polymerization. These intermediaries create a protective chemical environment that allows the high-level monomer combination to maintain both its desired lens properties and its polymerization stability.
Solution Approach 2:
The patent creates a composite formulation system that combines multiple components (siloxane, N-vinyl amide monomers, TPP, RB247, UV-absorbing agents, HEVL absorbers) into a stable mixture. This composite approach allows the beneficial properties of high-level monomer content to be realized while the composite structure provides enhanced stability against premature polymerization.
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 formulations maintain stability for over a day without gelation, significantly reducing lens defects and improving manufacturing consistency.
Implementation Method 1
Triphenylphosphine (TPP) can be added to formulated mixtures to act as an oxygen scavenger
Implementation Method 2
by including the tinting agent RB247 in contact lens formulations... Benzophenone UV-absorbing agents, such as UV416, and benzotriazole HEVL absorbers, especially UV13 or UV28, have also been found to enhance the stability
Data Source
AI summary
The present invention provides a silicone hydrogel contact lens formulation, comprising a polymerizable siloxane component, a hydrophilic N-vinyl amide monomer, triphenylphosphine (TPP) and one or more of anthraquinone blue tinting agent, a benzophenone UV-absorbing agent or a benzotriazole HEVL absorber; a silicone hydrogel contact lens formed from the polymerisation of the silicone hydrogel contact lens formulation; and the use of an anthraquinone blue tinting agent, a benzophenone UV-absorbing agent and/or a benzotriazole HEVL absorber to stabilise a formulation comprising a polymerizable siloxane component, a hydrophilic N-vinyl amide monomer and TPP.