Patent ID: 6911420

Claim:
A method to refine a lubricant including a compound A having a perfluoropolyether molecular structure that has two hydroxyl groups at each of two ends of compound A, and a compound B having the perfluoropolyether molecular structure that has one hydroxyl group at each of two ends of compound B, the method comprising: placing the lubricant into a pressure vessel set at a predetermined pressure and at a predetermined temperature; removing the compound B by a process comprising: flowing an extracting medium of a supercritical carbon dioxide fluid at a predetermined rate through the pressure vessel, holding the pressure vessel at the predetermined temperature and the predetermined pressure, dissolving the compound B in the supercritical carbon dioxide fluid, and removing the dissolved compound B from the pressure vessel; and recovering the compound A by a process comprising: flowing the extracting medium of the supercritical carbon dioxide fluid through the pressure vessel, holding the pressure vessel at the predetermined pressure and at a temperature lower than the predetermined temperature, dissolving the compound A in the extracting medium, and recovering the dissolved compound A from the pressure vessel.