Silicone Hydrogel Lens Formulation Stabilization Against Premature Gelation

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Solution Overview

Problem

Silicone hydrogel contact lens formulations containing triphenylphosphine (TPP) are susceptible to premature polymerization due to the presence of hydroquinone inhibitors, leading to poor pot-life and increased lens defects during manufacturing.

Innovation Solution

Incorporating 1,4-bis[(2-methacryloxyethyl)amino]-9,10-anthraquinone (RB247) and/or benzophenone UV-absorbing agents and benzotriazole HEVL absorbers into formulations with at least 40% polymerizable siloxane and 30% hydrophilic N-vinyl amide monomers stabilizes the formulations, reducing premature polymerization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If triphenylphosphine (TPP) is added to silicone hydrogel contact lens formulations, then lens processability and defect reduction are improved, but premature polymerization occurs leading to poor pot-life

Engineering Contradiction:

Improvelens processabilityVSAvoidformulation stability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

RB247 acts as an intermediary substance that mediates between TPP and the polymerizable groups. It preferentially reacts with or sequesters active species that would otherwise initiate premature polymerization, while allowing TPP to maintain its beneficial effects on lens processability and defect reduction. This resolves the contradiction by introducing a third component that protects the system from harmful interactions.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

RB247 provides preliminary anti-action by preventing polymerization before it can occur undesirably. The dye is incorporated into the formulation in advance to counteract the polymerizing tendency caused by TPP, especially under storage conditions. This preliminary protective action maintains formulation stability throughout storage and handling.

Inventive Principle:

Principle #9Preliminary anti-action

2Reliability

If hydroquinone inhibitors are used to prevent premature polymerization, then formulation stability is improved, but they become ineffective when oxygen is depleted

Engineering Contradiction:

Improveformulation stabilityVSAvoidoxygen dependency

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The invention changes the chemical parameter of the inhibition mechanism by replacing oxygen-dependent hydroquinone inhibitors with RB247, which operates through a different chemical pathway. RB247's stabilization mechanism does not rely on oxygen presence, making it effective under both aerobic and anaerobic conditions. This parameter change resolves the oxygen dependency limitation.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If high levels of polymerizable siloxane (≥40%) are used in formulations, then desired lens properties are achieved, but susceptibility to premature polymerization increases

Engineering Contradiction:

Improvelens property qualityVSAvoidpolymerization stability

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

RB247 serves as a protective intermediary specifically for high-siloxane formulations. It counteracts the increased polymerization susceptibility that comes with high siloxane content by providing a stabilizing effect that allows these formulations to maintain both their desired lens properties and improved polymerization stability during storage and handling.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 exhibit improved stability, maintaining a stable, non-gelled state for over 1 day and avoiding complete gelation for up to 3 days, compared to formulations without these additives which can gel within 1 to 2 days.

Implementation Method 1

1,4-bis[(2-methacryloxyethyl)amino]-9,10-anthraquinone (RB247) and/or benzophenone UV-absorbing agents and benzotriazole HEVL absorbers into formulations

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Implementation Method 2

Triphenylphosphine (TPP) can be added to formulated mixtures to act as an oxygen scavenger

Methodology Applied

Scientific EffectOxygen scavenging: Absorption (physical)

Data Source

PatentEP4646619B1Stabilized formulations for contact lenses

Publication Date: 2026.03.25 COOPERVISION INT LTD

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.