Silicone Hydrogel Lens Polymer Purification Using Supercritical CO2
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Solution Overview
Problem
Conventional methods struggle to effectively remove poorly water-soluble silicon-containing compounds from silicone hydrogel contact lenses without using flammable organic solvents, which are hazardous and increase production costs and risks.
Innovation Solution
A method involving polymerization of specific monomers followed by purification with subcritical or supercritical fluids, such as carbon dioxide, to produce a high-purity polymer for silicone hydrogel lenses, eliminating the need for hazardous solvents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If flammable organic solvents such as isopropanol or methyl ethyl ketone are used to remove unreacted silicon-containing monomer, then the purity of the cured product is improved, but the safety and production cost deteriorate due to fire hazards and equipment requirements
Solution Approach 1:
The patent changes the physical state and safety parameters of the extraction medium by using supercritical carbon dioxide instead of flammable liquid solvents. Carbon dioxide is non-flammable, inexpensive, and can be easily removed by pressure release, eliminating fire hazards while maintaining effective extraction of unreacted monomers and impurities from the silicone hydrogel contact lens polymer matrix.
Solution Approach 2:
The patent replaces the chemical extraction mechanism using organic solvents with a physical extraction mechanism using supercritical fluid. The supercritical state of carbon dioxide provides liquid-like density for high solubility and gas-like diffusivity for rapid mass transfer, enabling effective extraction without the harmful chemical properties of traditional organic solvents.
2Manufacturing precision
If flammable organic solvents are used for extraction, then unreacted monomers are effectively removed, but the production cost increases due to explosion-proof equipment requirements
Solution Approach 1:
The patent employs carbon dioxide, which is inexpensive, non-flammable, and can be easily disposed of or recycled. After extraction, the carbon dioxide is simply released by pressure reduction, leaving no residual solvent to handle. This eliminates the need for expensive explosion-proof equipment and safety infrastructure required for flammable organic solvents.
3Manufacturing precision
If large amounts of organic solvent are used, then unreacted monomer is effectively removed, but the manufacturing complexity and safety infrastructure requirements increase
Solution Approach 1:
The patent utilizes the unique parameters of supercritical fluids—specifically the ability to transition between supercritical and gaseous states through pressure and temperature control. This allows the extraction process to be conducted in a closed system with simple pressure control mechanisms, avoiding the need for complex ventilation, grounding, and explosion-proof equipment required for flammable liquid handling.
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 enables the production of high-purity silicone hydrogel lenses with reduced manufacturing costs and improved safety by effectively removing impurities without using flammable organic solvents, enhancing work safety and efficiency.
Implementation Method 1
purifying the polymer (A2) using a subcritical or supercritical fluid to obtain a polymer (A)
Data Source
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AI summary
The present invention provides: a method for producing a high-purity polymer (A); and a method for producing a silicone hydrogel lens at a low cost. A method for producing a polymer (A) according to the present invention comprises: (step 1) a step of obtaining a polymer (A1) by polymerizing a first monomer (a) that has one ethylenically unsaturated group; (step 2) a step of obtaining a polymer (A2) by having the polymer (A1) react with a second monomer that has an ethylenically unsaturated group; and (step 3) a step of obtaining a polymer (A) by purifying the polymer (A2) with use of a subcritical or supercritical fluid. The first monomer is selected from one of the first group consisting of hydroxyl group-containing monomers, and the second group consisting of isocyanate compounds of (meth)acrylic acids, anhydrides of (meth)acrylic acids, and halides of (meth)acrylic acids. The second monomer is selected from the other of the first group and the second group.