Solvo-Surfactant Mold Cleaning for Silicone Hydrogel Lenses
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Solution Overview
Problem
The conventional cast-molding technique for silicone hydrogel contact lenses faces challenges due to dimensional variations in disposable plastic molds, leading to inconsistencies in lens production, and the use of organic solvents for cleaning reusable molds is costly, environmentally unfriendly, and inefficient.
Innovation Solution
A water-based cleaning method using a solvo-surfactant, specifically an alkyl (propylene glycol) n ether, is employed to effectively clean reusable molds, facilitating the dissolution and dispersion of silicone-containing components, thereby maintaining high cleaning performance and reducing environmental impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If organic solvents are used to clean reusable molds, then cleaning effectiveness is improved, but cost increases and environmental harm worsens
Solution Approach 1:
The invention changes the chemical parameters of the cleaning system by using water-based solvo-surfactants instead of organic solvents. The solvo-surfactants have specific molecular structures (alkyl chains with ethoxylate groups) that enable them to dissolve silicone-containing components effectively in water, achieving comparable cleaning effectiveness without the environmental harm of organic solvents.
Solution Approach 2:
The solvo-surfactant acts as an intermediary substance between water and the silicone-containing components on the mold surface. It has both hydrophilic (water-soluble) and lipophilic (silicone-soluble) characteristics, allowing it to bridge the gap between water and the non-polar silicone residues, enabling effective removal without direct contact between water and silicone.
2Object-affected harmful factors
If ethoxylated water-soluble silicone surfactants are used, then environmental friendliness is improved, but foaming increases requiring additional defoamer
Solution Approach 1:
The invention modifies the molecular structure parameters of the surfactant by controlling the alkyl chain length (C12-C22) and the degree of ethoxylation (average 3-15 ethoxylate groups). These parameter optimizations reduce excessive foaming while maintaining cleaning effectiveness, eliminating the need for additional defoamers and simplifying the process.
3Manufacturing precision
If reusable molds are used for Lightstream Technology, then manufacturing precision is improved, but cleaning difficulty increases due to spatial limitation of actinic radiation
Solution Approach 1:
The solvo-surfactant serves as an intermediary that can access and clean mold surfaces in the spatially limited environment between the mold and the UV radiation field. Its amphiphilic nature allows it to effectively remove silicone residues from the mold surfaces that are exposed to spatially limited actinic radiation, maintaining cleaning effectiveness despite the geometric constraints.
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 method ensures high fidelity in lens production, reduces environmental harm, and minimizes water consumption, achieving efficient and sustainable mold cleaning while preventing re-soiling, thus enhancing the reproducibility and quality of silicone hydrogel contact lenses.
Implementation Method 1
the solvo-surfactant is an alkyl (propylene glycol) n ether wherein alkyl is a linear alkyl group having 2 to 5 carbon atoms and n is the integer 1, 2 or 3
Implementation Method 2
a water-based solution containing a solvo-surfactant, wherein the solvo-surfactant is an alkyl (propylene glycol) n ether
Data Source
AI summary
Method for washing, with a water-based system, reusable molds for making silicone hydrogel contact lenses. The water-based washing system comprises a solvo-surfactant which is an alkyl (propylene glycol)nether wherein alkyl is a linear alkyl group having 2 to 5 carbon atoms and n is the integer 1, 2 or 3. The water-based system of the invention can effectively wash away silicone-containing components and other components of a lens formulation left behind on the molding surfaces of a reusable mold, after removing a silicone hydrogel contact lens cast molded in the reusable mold.