Silicone Hydrogel Lens Polymer Purification With 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 to produce a high-purity polymer, using monomers like hydroxy group-containing monomers, (meth)acrylic isocyanate compounds, and (meth)acrylic anhydrides, and purifying with carbon dioxide or its mixtures to remove impurities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If flammable organic solvents such as isopropanol or methyl ethyl ketone are used to remove unreacted silicon-containing monomer from cured product, then the unreacted monomer can be effectively removed, but the production cost increases significantly and the risk of fire and other disasters increases

Engineering Contradiction:

ImprovesafetyVSAvoidproduction cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the physical and chemical parameters of the extraction system by using supercritical carbon dioxide instead of conventional organic solvents. By adjusting pressure and temperature parameters to achieve supercritical state, CO2 achieves effective extraction capability while eliminating fire hazards and reducing production costs

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs carbon dioxide, an inexpensive and readily available gas, as the extraction medium. After use, the CO2 is simply depressurized and can be vented or recycled, eliminating the need for expensive explosion-proof equipment and complex solvent recovery systems required for flammable organic solvents

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Reliability

If flammable organic solvents are used to remove unreacted monomer, then extraction effectiveness is achieved, but explosion-proof equipment is required resulting in huge equipment costs

Engineering Contradiction:

Improveextraction effectivenessVSAvoidequipment cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent creates an inert extraction environment by using carbon dioxide, which does not support combustion. This eliminates the need for explosion-proof equipment while maintaining effective extraction of unreacted monomers from the cured contact lens product

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

3Productivity

If conventional polymerization methods are used, then polymer production is achieved, but poorly water-soluble silicon-containing compounds remain as impurities that are difficult to remove

Engineering Contradiction:

Improvepolymer production efficiencyVSAvoidpurity of polymer

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent utilizes the phase transition properties of carbon dioxide between gas and supercritical fluid states. By pressurizing CO2 into a supercritical state for extraction, then depressurizing it back to gas, the system achieves continuous extraction cycles that effectively remove silicon-containing impurities while maintaining high polymer production efficiency

Inventive Principle:

Principle #36Phase transitions

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 contact lenses at reduced costs and improved safety by eliminating the need for flammable organic solvents, enhancing work safety and efficiency.

Implementation Method 1

purifying the polymer (A2) with a subcritical or supercritical fluid to obtain a polymer (A)

Methodology Applied

Scientific EffectSupercritical fluid extraction: Supercritical Fluid Extraction

Implementation Method 2

polymerizing a first monomer (a) having an ethylenically unsaturated group to obtain a polymer (A1)

Methodology Applied

Scientific EffectPolymerization:

Data Source

PatentUS20260103556A1Method for producing polymer, method for producing curable composition, method for producing cured product, and method for producing contact lens using curable composition

Publication Date: 2026.04.16 NIPPON KAYAKU CO LTD

AI summary

A method for producing a high-purity polymer (A); and a method for producing a silicone hydrogel lens at a low cost are provided. A method for producing a polymer (A) includes: (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 and second group.