Water-Based Silicone Hydrogel Lens Formulation
Solution Overview
Problem
The production of silicone hydrogel contact lenses requires organic solvents, which pose safety concerns due to the generation of organic vapors during lens production, necessitating a solvent-free method for safer manufacturing.
Innovation Solution
A water-based lens-forming composition comprising a polysiloxane-containing vinylic macromer, optionally a hydrophilic vinylic monomer, a polysiloxane-containing surfactant, and water is introduced into a mold, cured, and then removed, eliminating the need for organic solvents and allowing for a clear solution formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If organic solvents are used in lens formulation, then the polysiloxane-containing vinylic monomer can be dissolved to form a transparent formulation, but organic vapors are generated during production causing safety concerns
Solution Approach 1:
The invention changes the solvent parameter from organic to water-based, while adjusting the surfactant composition (polysiloxane-containing surfactant with 10-40% polysiloxane segments and 60-90% hydrophilic units) to achieve the necessary solubility and transparency in the water-based system
Solution Approach 2:
The polysiloxane-containing surfactant acts as an intermediary substance that enables the dissolution of polysiloxane-containing vinylic monomer in water, bridging the incompatibility between hydrophobic monomer and hydrophilic solvent while eliminating organic vapor generation
2Object-affected harmful factors
If water-based lens-forming composition is used, then organic vapor generation is eliminated improving safety, but the ability to dissolve polysiloxane-containing vinylic monomer becomes challenging
Solution Approach 1:
The invention uses a composite surfactant system containing polysiloxane segments (10-40% by weight) combined with hydrophilic units (60-90% by weight), creating a amphiphilic structure that can interact with both the hydrophobic monomer and hydrophilic water solvent to achieve transparent formulation without organic solvents
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 method reduces the use of organic solvents, enhancing safety by using water as a solvent and ensuring the polysiloxane-containing vinylic monomer is dissolved in water, forming a clear solution, thereby improving the production process of silicone hydrogel lenses.
Implementation Method 1
The polysiloxane-containing surfactant is present in the lens-forming composition in an amount sufficient to dissolve the polysiloxane-containing vinylic monomer or macromer in water to form a substantially clear solution
Implementation Method 2
curing the lens-forming composition in a mold to form the lens
Data Source
AI summary
Described herein are methods for producing silicone hydrogel lenses. The methods involve introducing into a mold a water-based lens-forming composition, curing the lens- forming composition in a mold to form the lens, and removing the lens from the mold. The lens-forming composition comprises (i) a polysiloxane-containing vinylic monomer or macromer, (ii) at least one hydrophilic vinylic monomer, (iii) a surfactant, and, and (iv) water. The surfactant is polysiloxane-containing surfactant that is free of actinically- polymerizable groups and is a copolymer having from about 10% to about 40% by weight of one or more polysiloxane segments and from about 90% to about 60% by weight hydrophilic units and/or segments. The methods permit the use of water as a solvent and reduce the need for organic solvents. Additionally, the lenses produced by the methods can have improved properties such oxygen permeability.