(19)
(11)EP 3 092 045 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
09.09.2020 Bulletin 2020/37

(21)Application number: 14830458.7

(22)Date of filing:  23.12.2014
(51)International Patent Classification (IPC): 
B01D 15/12(2006.01)
C10M 175/00(2006.01)
B01D 11/04(2006.01)
(86)International application number:
PCT/US2014/072195
(87)International publication number:
WO 2015/105686 (16.07.2015 Gazette  2015/28)

(54)

PERFLUOROPOLYETHER EXTRACTION PROCESSES

PERFLUOROPOLYETHER-EXTRAKTIONSVERFAHREN

PROCÉDÉS D'EXTRACTION DE PERFLUOROPOLYÉTHER


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 07.01.2014 US 201461924461 P

(43)Date of publication of application:
16.11.2016 Bulletin 2016/46

(73)Proprietor: The Chemours Company FC, LLC
Wilmington DE 19801 (US)

(72)Inventors:
  • HUTCHENSON, Keith, W.
    Lincoln University, PA 19352 (US)
  • LIBERT, Sharon Ann
    Hockessin, DE 19707 (US)
  • HOWELL, Jon Lee
    Bear, DE 19701 (US)
  • LIANG, Xian
    Moorestown, NJ 08057 (US)

(74)Representative: Dannenberger, Oliver Andre et al
Abitz & Partner Patentanwälte mbB Arabellastrasse 17
81925 München
81925 München (DE)


(56)References cited: : 
US-A1- 2004 092 406
US-A1- 2013 237 462
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    BACKGROUND


    Field of the Disclosure



    [0001] The present disclosure relates to a process for extracting and recovering a perfluoropolyether from a lubricating grease.

    Description of Related Art



    [0002] Perfluoropolyether (PFPE) oils are highly valued for properties including high-temperature performance, non-flammability, chemical inertness, superior stability and lubricity. Lubricating grease compounds, which possess similar properties, are created by combining the PFPE oil with a variety of thickeners and optionally other additives to meet the requirements of different applications.

    [0003] Lubricating greases are manufactured so that the PFPE oil and the thickeners and other additives do not easily separate. This is extremely important in lubrication applications that experience high temperatures or high mechanical loads. An example of this requirement is in the aerospace industry which has adopted a military specification MIL-PRF-27617G that limits the amount of oil separation for various grades of grease. MIL-PRF-27617G Type II grease has a maximum allowance of oil separation of 15.0% when the grease is exposed to a temperature of 204°C for a total of 30 hours. The oil separation is measured according to ASTM Method D6184 Standard Test Method for Oil Separation from Lubricating Grease.

    [0004] Manufacturers that produce the lubricating grease compounds and the OEMS that consume the lubricating grease compounds generate waste streams of grease. The grease waste occurs during equipment cleanouts or during product transitions or during incomplete grease product removal from a package or other process steps that are common to manufacturing operations. The PFPE oil in the grease waste stream is not affected by contact with the additives or by the time in the waste stream, and the PFPE oil retains all of its valuable The document DE 19 739 659 describes a method for recycling used lubricant grease comprising oil and thickeners, wherein the oil is extracted in a multiple extraction step with organic solvents.

    [0005] Therefore, there is a need to develop a cost-effective and environmentally-friendly process that is capable of separating the PFPE oil from the grease and recovering the oil for use.

    BRIEF SUMMARY OF THE DISCLOSURE



    [0006] The present disclosure provides a process for extracting a perfluoropolyether from a lubricating grease. The process comprises: (a) contacting a solvent comprising a liquid or supercritical carbon dioxide with the lubricating grease comprising a thickener and the perfluoropolyether in an extraction zone to form an extraction solution comprising an extracted perfluoropolyether; and (b) recovering the extracted perfluoropolyether from the extraction solution; wherein the recovered extracted perfluoropolyether comprises no more than about 2 wt % of the thickener.

    BRIEF DESCRIPTION OF THE FIGURE



    [0007] Embodiments are illustrated in the accompanying figures to improve understanding of concepts as presented herein.

    FIG. 1 includes as illustration the extraction process flowsheet of custom high-pressure extraction apparatus.

    FIG. 2 includes as illustration the extraction curve (extraction yield versus solvent to lubricating grease ratio, or solvent-to-feed ratio) for Example 1 at 3500 psig and 60°C.

    FIG. 3 includes as illustration the extraction curve (extraction yield versus solvent to lubricating grease ratio, or solvent-to-feed ratio) for Example 2 at 4500 psig and 80°C.

    FIG. 4 includes as illustration the extraction curve (extraction yield versus solvent to lubricating grease ratio, or solvent-to-feed ratio) for Example 3 at 1200 psig and 28°C.

    FIG. 5 includes as illustration the extraction curve (extraction yield versus solvent to lubricating grease ratio, or solvent-to-feed ratio) for Example 4 at 2500 psig and 50°C.



    [0008] Skilled artisans appreciate that objects in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the objects in the figures may be exaggerated relative to other objects to help to improve understanding of embodiments.

    DETAILED DESCRIPTION



    [0009] The foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as defined in the appended claims. Other features and benefits of any one or more of the embodiments will be apparent from the following detailed description, and from the claims.

    [0010] As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, "or" refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

    [0011] Also, use of "a" or "an" are employed to describe elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

    [0012] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present invention, suitable methods and materials are described below. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

    [0013] When an amount, concentration, or other value or parameter is given as either a range, preferred range or a list of upper preferable values and/or lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range.

    [0014] Before addressing details of embodiments described below, some terms are defined or clarified.

    [0015] The term "wt %", as used herein, means weight percent.

    [0016] The term "extraction", "extracted", or "extracting", as used herein, means a physical or chemical method of removing one or more components from a substrate by means of a solvent.

    [0017] The term "extracted perfluoropolyether", as used herein, means a perfluoropolyether that has been separated from the lubricating grease through extraction processes of this invention.

    [0018] The term "lubricating grease", as used herein, means the grease receiving the extraction processes of this invention to recover the PFPE oil contained therein. Typically, the lubricating grease comprises PFPE and one or more thickeners and other additives (if present, e.g., anti-corrosion additives) used in making such grease.

    [0019] The term "yield of the extracted perfluoropolyether", as used herein, means the amount of the extracted PFPE compared to the total amount of PFPE contained in the lubricating grease prior to extraction.

    SUPERCRITICAL FLUID



    [0020] Supercritical fluids (SCF) exhibit properties intermediate between those of gases and liquids. A key feature of a SCF is that the fluid density can be varied continuously from liquid-like to gas-like densities by varying either the temperature or pressure, or a combination thereof. Various density-dependent physical properties likewise exhibit similar continuous variation in this region. Some of these properties include, but are not limited to, solvent strength (as evidenced by the solubilities of various substances in the SCF media), polarity, viscosity, diffusivity, heat capacity, thermal conductivity, isothermal compressibility, expandability, contractibility, fluidity, and molecular packing. The density variation in a SCF also influences the chemical potential of solutes and hence, reaction rates and equilibrium constants. Thus, the solvent environment in a SCF media can be optimized for a specific application by tuning the various density-dependent fluid properties.

    [0021] A fluid is in the SCF state when the system temperature and pressure exceed the corresponding critical point values defined by the critical temperature (Tc) and pressure (Pc). For pure substances, the Tc and Pc are the highest at which vapor and liquid phases can coexist. Above the Tc, a liquid does not form for a pure substance, regardless of the applied pressure. Similarly, the Pc and critical molar volume are defined at this Tc corresponding to the state at which the vapor and liquid phases merge. For carbon dioxide, the critical point is 7.38 MPa (Pc) at 31.1 °C (Tc). For a discussion of supercritical fluids, see Kirk-Othmer Encycl. of Chem. Technology, 4th Ed., Vol. 23, pg. 452-477.

    PERFLUOROPOLYETHERS



    [0022] Perfluoropolyethers are oligomers or polymers composed of perfluoroalkyl ether repeating units. A perfluoropolyether is typically polydisperse, a mixture of oligomers or polymers with different molecular weights. Perfluoropolyether is synonymous to perfluoropolyalkylether. Other synonymous terms frequently used include "PFPE", "PFAE", "PFPE oil", "PFPE fluid", and "PFPAE". These synonyms can be used interchangeably in this disclosure. The two end groups of a suitable perfluoropolyether for the processes of this invention, independently, can be functionalized or unfunctionalized. In an unfunctionalized perfluoropolyether, the end group can be branched or straight chain perfluoroalkyl radical end groups. Examples of such perfluoropolyethers can have the formula of Cr'F(2r'+1)-A-Cr'F(2r'+1) in which each r' is independently 3 to 6; A can be O-(CF(CF3)CF2-O)w', O-(CF2-O)x'(CF2CF2-O)y', O-(C2F4-O)w', O-(C2F4-O)x'(C3F6-O)y', O-(CF(CF3)CF2-O)x'(CF2-O)y', O-(CF2CF2CF2-O)w', O-(CF(CF3)CF2-O)x'(CF2CF2-O)y'-(CF2-O)z', or combinations of two or more thereof; preferably A is O-(CF(CF3)CF2-O)w', O-(C2F4-O)w', O-(C2F4-O)x'(C3F6-O)y', O-(CF2CF2CF2-O)w', or combinations of two or more thereof; w' is an integer from 4 to 100; x' and y' are each independently an integer from 1 to 100. Specific examples include, but are not limited to, F(CF(CF3)-CF2-O)9-CF2CF3, F(CF(CF3)-CF2-O)9-CF(CF3)2, and combinations thereof. In such PFPEs, up to 30% of the halogen atoms can be halogens other than fluorine, such as, for example, chlorine atoms.

    [0023] In some embodiments of this invention, the lubricating grease comprises a perfluoropolyether wherein at least one end group of the perfluoropolyether is unfunctionalized. In some embodiments, such an unfunctionalized end group is a branched or straight chain perfluoroalkyl group. In some embodiments, such an unfunctionalized end group is a straight chain perfluoroalkyl group.

    [0024] The two end groups of a suitable perfluoropolyether for the processes of this invention, independently, can also be functionalized. A typical functionalized end group can be selected from the group consisting of esters, hydroxyls, amines, amides, cyanos, carboxylic acids and sulfonic acids. In some embodiments of this invention, these functionalized perfluoropolyethers are added to the fully inert PFPE fluids as anti-corrosion, anti-wear, or extreme pressure additives in an amount of no more than about 10 wt %, and in some embodiments no more than about 3 wt %, compared to the total amount of PFPE fluid.

    [0025] Representative perfluoropolyethers suitable for the processes of this invention include KRYTOX® fluids which are available from DuPont and have the formula of CF3-(CF2)2-O-[CF(CF3)-CF2-O]j'-R'f. In the formula, j' is an integer from 2 - 100 and R'f is CF2CF3, a C3 to C6 perfluoroalkyl group, or combinations thereof.

    [0026] Representative perfluoropolyethers suitable for the processes of this invention also include FOMBLIN® and GALDEN® fluids, available from Ausimont, Milan, Italy and produced by perfluoroolefin photooxidation. For example, FOMBLIN®-Y can have the formula of CF3O[CF2CF(CF3)O]m(CF2O)n-R1f or CF3O[CF2CF(CF3)O]m'(CF2CF2O)o'(CF2O)n'-R1f. In the formulae R1f is CF3, C2F5, C3F7, or combinations of two or more thereof; (m + n) is an integer from 8 - 45; and m/n is from 20 - 1000; o' is 1; (m'+n'+o') is an integer from 8 - 45; m'/n' is from 20 - 1000. FOMBLIN®-Z can have the formula of CF3O(CF2CF2-O-)p'(CF2-O)q'CF3 where (p' + q') is an integer from 40 - 180 and p'/q' is from 0.5 - 2.

    [0027] Representative perfluoropolyethers suitable for the processes of this invention also include DEMNUM® fluids, another family of PFPE available from Daikin Industries. It can be produced by sequential oligomerization and fluorination of 2,2,3,3-tetrafluorooxetane, yielding the formula of F-[(CF2)3-O]t'-R2f where R2f is CF3, C2F5, or combinations thereof and t' is an integer from 2 - 200.

    LUBRICATING GREASE



    [0028] A lubricating grease receiving the extraction processes of this invention typically comprises, other than PFPE, one or more thickeners and optionally one or more other additives such as anti-corrosion additives, anti-rust additives, or anti-wear additives. In some embodiments of this invention, the lubricating grease comprises, consists essentially of, or consists of a thickener and a perfluoropolyether.

    [0029] Thickeners for a lubricating grease include, but are not limited to, one or more of the following materials: halogenated polymers and copolymers such as polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), perfluoroalkoxy (PFA), perfluoro methyl alkoxy (MFA), ethylene tetrafluoroethylene (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene chlorotrifluoroethylene (ECTFE), polyvinylidene fluoride (PVDF), and the like, talc, silica, clay, boron nitride, titanium dioxide, silicon nitride, metal soaps such as lithium soaps, sodium soaps, lithium complex soaps, calcium sulfonates, aluminum soaps, and the like, melamine cyanurate, urea, polyureas, polyurethanes, and polyolefins such as polyethylene. In some embodiments, the silica thickener is a fumed silica. The thickeners can be present in any appropriate molecular weight distributions, particle shapes and sizes as known to one skilled in the art. For example, the polytetrafluoroethylene thickener can be polytetrafluoroethylene micropowder.

    [0030] In some embodiments of this invention, the thickener is a halogenated polymer or co-polymer. In some embodiments of this invention, the thickener is selected from the group consisting of PTFE, FEP, PFA, MFA, ETFE, PCTFE, ECTFE, PVDF, and combinations thereof. In some embodiments of this invention, the thickener is PTFE.

    [0031] In some embodiments of this invention, the thickener is an inorganic compound. In some embodiments of this invention, the thickener is selected from the group consisting of talc, silica, clay, boron nitride, titanium dioxide, silicon nitride, and combinations thereof.

    [0032] In some embodiments of this invention, the thickener is an organic compound. In some embodiments of this invention, the thickener is selected from the group consisting of metal soaps, melamine cyanurate, urea, polyureas, polyurethanes, polyolefins, and combinations thereof.

    [0033] In some embodiments of this invention, the metal soap is selected from the group consisting of lithium soaps, sodium soaps, lithium complex soaps, calcium sulfonates, aluminum soaps, and combinations thereof.

    [0034] In some embodiments of this invention, the lubricating grease further comprises, other than PFPE and thickener, one or more other additives such as anti-corrosion additives, anti-rust additives, or anti-wear additives. Examples of such other additives include sodium nitrite and organic phosphorus compounds.

    EXTRACTION AND RECOVERY



    [0035] The present disclosure provides a process for extracting a perfluoropolyether. The process comprises: (a) contacting a solvent comprising a liquid or supercritical carbon dioxide with a lubricating grease comprising a thickener and the perfluoropolyether in an extraction zone to form an extraction solution comprising an extracted perfluoropolyether; and (b) recovering the extracted perfluoropolyether from the extraction solution; wherein the recovered extracted perfluoropolyether comprises no more than about 2 wt % of the thickener.

    [0036] It was found through experiments that perfluoropolyethers contained in a lubricating grease can be efficiently separated and recovered from the grease by using liquid or supercritical carbon dioxide as the extracting solvent. The process is cost-effective and environmentally friendly.

    [0037] In some embodiments of this invention, the yield of the extracted perfluoropolyether is at least about 75 wt %. In some embodiments, the yield of the extracted perfluoropolyether is at least about 80 wt %. In some embodiments, the yield of the extracted perfluoropolyether is at least about 85 wt %. In some embodiments, the yield of the extracted perfluoropolyether is at least about 90 wt %. In some embodiments, the yield of the extracted perfluoropolyether is at least about 95 wt %. In some embodiments, the yield of the extracted perfluoropolyether is at least about 99 wt %.

    [0038] A suitable solvent for the extraction processes of this invention comprises, consists essentially of, or consists of a liquid carbon dioxide or a supercritical carbon dioxide.

    [0039] In some embodiments of this invention, the solvent comprises, consists essentially of, or consists of a liquid carbon dioxide. In some embodiments, the solvent consists essentially of a liquid carbon dioxide.

    [0040] In some embodiments of this invention, the solvent comprises, consists essentially of, or consists of a supercritical carbon dioxide. In some embodiments, the solvent consists essentially of a supercritical carbon dioxide.

    [0041] In some embodiments of this invention, the weight ratio of the solvent to the lubricating grease is no more than about 50. In some embodiments of this invention, the weight ratio of the solvent to the lubricating grease is no more than about 30. In some embodiments, the weight ratio of the solvent to the lubricating grease is no more than about 10. In some embodiments, the weight ratio of the solvent to the lubricating grease is no more than about 8. In some embodiments, the weight ratio of the solvent to the lubricating grease is no more than about 7. In some embodiments, the weight ratio of the solvent to the lubricating grease is no more than about 6. In some embodiments, the weight ratio of the solvent to the lubricating grease is no more than about 5.

    [0042] In some embodiments of this invention, the weight ratio of the solvent to the lubricating grease is no more than about 7, and the yield of the extracted perfluoropolyether is at least about 75 wt %, at least about 90 wt %, or at least about 95 wt %. In some embodiments of this invention, the solvent comprises, consists essentially of, or consists of a supercritical carbon dioxide, the weight ratio of the solvent to the lubricating grease is no more than about 7, the temperature in the extraction zone is from about 40 °C to about 100 °C, the pressure in the extraction zone is from about 2200 psig to about 6000 psig, and the yield of the extracted perfluoropolyether is at least about 90 wt % or at least about 95 wt %.

    [0043] The contacting step (a) can be carried out using well-known chemical engineering practices in an extraction vessel. In some embodiments of this invention, a lubricating grease is placed in a container through which the liquid or supercritical carbon dioxide is passed to solubilize the PFPE contained in the lubricating grease to form an extraction solution. The liquid or supercritical carbon dioxide can flow through the lubricating grease continuously, or be exposed to the lubricating grease in a discontinuous batch process.

    [0044] The extraction vessel can be made of materials known in the art. In some embodiments of this invention, the extraction vessel is a stainless steel, high pressure vessel. In some embodiments of this invention, the extraction vessel is a vertical column and is operated in an upflow or downflow configuration. In some embodiments, the solvent is fed to the extraction zone in an upflow mode. In some embodiments, the solvent is fed to the extraction zone in a downflow mode.

    [0045] The temperature and pressure in the extraction zone are chosen to keep the carbon dioxide in the liquid or supercritical state during the extraction process.

    [0046] When the solvent comprises, consists essentially of, or consists of a supercritical carbon dioxide, typically the temperature in the extraction zone is from Tc to no more than about 150 °C. In some embodiments, the temperature is from about 40 °C to about 110 °C. In some embodiments, the temperature is from about 50 °C to about 100 °C. In some embodiments, the temperature is from about 60 °C to about 90 °C. In some embodiments, the temperature is from about 70 °C to about 90 °C. Typically, the pressure in the extraction zone is from about 1500 psig to about 10,000 psig. In some embodiments, the pressure is from about 1500 psig to about 6000 psig. In some embodiments, the pressure is from about 2000 psig to about 6000 psig. In some embodiments, the pressure is from about 3000 psig to about 5000 psig. In some embodiments, the pressure is from about 4000 psig to about 5000 psig.

    [0047] When the solvent comprises, consists essentially of, or consists of a liquid carbon dioxide, typically the temperature in the extraction zone is from about 0 °C to less than Tc. In some embodiments, the temperature is from about 15 °C to less than Tc. In some embodiments, the temperature is from about 25 °C to less than Tc.

    [0048] The extraction solution obtained from the contacting step typically comprises the solvent (i.e., liquid or supercritical carbon dioxide), the extracted perfluoropolyether, water, and the thickener contaminant.

    [0049] In the recovering step (b), the extracted perfluoropolyether can be recovered from the extraction solution. In some embodiments of this invention, the extracted perfluoropolyether is recovered from the extraction solution by evaporating the liquid or supercritical carbon dioxide. As the liquid or supercritical carbon dioxide evaporates, the extracted perfluoropolyether is typically precipitated out together with water and the thickener contaminant contained in the extraction solution.

    [0050] It was found through experiments that PFPE can be effectively separated from the lubricating grease substantially free of thickeners and other additives. In some embodiments of this invention, the recovered extracted perfluoropolyether comprises no more than about 2 wt % of the thickener. In some embodiments of this invention, the recovered extracted perfluoropolyether comprises no more than about 1 wt % of the thickener. In some embodiments of this invention, the recovered extracted perfluoropolyether comprises no more than about 0.1 wt % of the thickener. In this disclosure, the sentence "recovered extracted perfluoropolyether comprises no more than about 2 wt % of the thickener" means that the amount of the thickener contaminant contained in the recovered extracted perfluoropolyether is no more than about 2 wt % compared to the total amount of the pure perfluoropolyether and the thickener contained in the recovered extracted perfluoropolyether.

    [0051] In some embodiments of this invention, the extraction solution is directed through a pressure reduction valve to a separation vessel where the liquid or supercritical carbon dioxide is evaporated and removed and the extracted perfluoropolyether is precipitated from the extraction solution for collection. The relatively pure CO2 stream from the top of the separation vessel may be recycled back to the extraction zone.

    [0052] In some embodiments of this invention, the recovered extracted perfluoropolyethers can be further purified as described in this disclosure.

    PURIFICATION



    [0053] Water and other contaminants in the recovered extracted perfluoropolyether can be removed by techniques known in the art. In some embodiments, water and the extracted perfluoropolyether will separate into two phases, and water can be removed by, for example, simple decantation. In some embodiments, water can be removed by drying agents such as molecular sieves.

    [0054] In some embodiments of this invention, the recovered extracted perfluoropolyether can be purified by contacting with an adsorbing agent, such as activated carbon, diatomaceous earth, or alumina, to remove the discoloration contaminants. The activated carbon can be in the form of powder, granules, or pellets, et al. Commercially available diatomaceous earth include those sold under the Celite® trademark name.

    [0055] Activated carbon used in the embodiments of this invention may come from any of the following sources: wood, peat, coal, coconut shells, bones, lignite, petroleum-based residues and sugar. Commercially available activated carbons which may be used include those sold under the following trademarks: Barneby & Sutcliffe™, Darco™, Nucharm, Columbia JXN™, Columbia LCK™, Calgon™ PCB, Calgon™ BPL, Westvaco™, Norit™, Takeda™ and Barnaby Cheny NB™.

    [0056] The activated carbon also includes three dimensional matrix porous carbonaceous materials. Examples are those described in U.S. Pat. No. 4,978,649. In one embodiment of the invention, activated carbon includes three dimensional matrix carbonaceous materials which are obtained by introducing gaseous or vaporous carbon-containing compounds (e.g., hydrocarbons) into a mass of granules of a carbonaceous material (e.g., carbon black); decomposing the carbon-containing compounds to deposit carbon on the surface of the granules; and treating the resulting material with an activator gas comprising steam to provide a porous carbonaceous material. A carbon-carbon composite material is thus formed.

    [0057] In some embodiments, the purified extracted perfluoropolyether can be fractionated or distilled to generate perfluoropolyether with desired molecular weight. The purified extracted perfluoropolyether can also undergo chemical reactions to produce PFPE oil with desired properties.

    [0058] Many aspects and embodiments have been described above and are merely exemplary and not limiting. After reading this specification, skilled artisans appreciate that other aspects and embodiments are possible without departing from the scope of the invention.

    EXAMPLES



    [0059] The concepts described herein will be further described in the following examples, which do not limit the scope of the invention described in the claims.

    [0060] Materials: Eleven grades of formulated perflurorpolyether lubricating greases were used in these examples, including commercially-available DuPont Krytox® greases and non-commercial research samples to illustrate the breadth of the applicability of this extraction process at recovering perfluoropolyether oil from various grease matrix formulations.
    • Krytox® GPL 203: 15 - 45 % PTFE Micropowder and 55 - 85 % PFPE Oil
    • Krytox® GPL 207: 15 - 45 % PTFE Micropowder and 55 - 85 % PFPE Oil
    • Krytox® GPL 227: 18 - 27 % PTFE Micropowder, 1 - 5% Sodium Nitrite and 71 - 80 % PFPE Oil
    • Krytox® GPL226SR: 23-25 % PTFE Micropowder, 2-3 % of a proprietary additive, and 73-74% PFPE oil
    • Krytox® NRT 8908: 30 - 50 % Talc (Mg3H2(SiO3)4) and 50-70 % PFPE oil
    • Krytox® GPL 407: 1- 10 % Silica and 90-95% PFPE Oil
    • XHT-BD: 15 - 25 % Boron Nitride, and 75 - 85 % PFPE oil
    • Mg Stearate:GPL205: 15-45 % Mg Stearate powder and 55-85% PFPE oil
    • BN/PTFE:GPL205: 10 - 40 % Micropowder consisting of 50wt% Boron Nitride/50wt% PTFE thickener and 6-85% PFPE oil
    • PU: 15- 45 % Polyurea thickener and 35-45% PFPE oil
    • PU/ZnO: 15-45% Polyurea + zinc oxide thickener and 35-45% PFPE oil


    [0061] Carbon dioxide (99.99% grade) was obtained from GTS-Welco.

    [0062] Extraction Method: The extraction examples were conducted using a custom high-pressure extraction apparatus illustrated in Figure 1. The 300 mL extraction vessel (High Pressure Equipment Co.) was fabricated from 316 SS and was equipped with a 2-micron sintered metal filter on the effluent end of the vessel. The extraction vessel was fitted with band heating elements (Power Modules, Inc.) which were controlled by an automated temperature controller monitoring a thermocouple imbedded in the extraction vessel wall. The vessel was equipped with an insulation blanket to maintain a uniform extraction temperature. The CO2 was supplied from a standard cylinder with the CO2 vapor from the top of the cylinder condensed and chilled to 5°C in a heat exchanger and fed into one of two positive displacement syringe pumps (Isco Model 100D/X) for metering into the extraction vessel. The CO2 pumps were interconnected via a dual-pump valve kit (ISCO Model DP VK) and operated in continuous flow mode. Prior to entering the top of the extraction vessel, the inlet CO2 stream was preheated by an electrical heating tape (Amptek AWH-051) wrapped around the transfer tubing which was operated via an automated temperature controller. The extraction temperature was monitored and controlled from three calibrated thermocouples (Omega Engineering Inc., Type K) located at the extraction vessel inlet, inside the extraction vessel, and at the extraction vessel outlet. The extraction pressure was maintained with an automated back pressure regulator (Jasco Model BP-1580-81) on the effluent side of the vessel, and the extracted perfluoropolyether oil was collected in a sample vessel while simultaneously venting the CO2 solvent to the atmosphere.

    [0063] For each example, an approximately 100-200 g quantity of the starting lubricating grease was weighed into two perforated metal baskets custom made to fit into the 300mL extraction vessel. After placing these baskets into the extraction vessel, the system was sealed, heated, and pressurized at the desired CO2 flow rate to the desired operating conditions. The back pressure regulator was then set to the desired operating pressure. The time, pressure, temperature, recovered PFPE oil weight, and total CO2 liquid volume fed from the syringe pumps were monitored during the extraction. When the desired extraction time was complete, a pre-programmed 2hr depressurization routine was initiated on the back pressure regulator to reduce the system to atmospheric pressure. The baskets were then removed and weighed. Reported extraction yields from the starting lubricating grease samples were determined gravimetrically based on the total amount of PFPE oil contained in the starting lubricating greases.

    [0064] The following examples show quantitative results for semi-continuous CO2 extractions of the eleven DuPont Krytox® lubricating grease samples under various conditions to exemplify the technical feasibility of this process approach for separating the Krytox® PFPE oil from the lubricating grease matrix.

    EXAMPLE 1


    Extraction Curve at 3500 psig and 60°C using Supercritical CO2 with Krytox® GPL 207 Lubricating Grease



    [0065] This Example demonstrated the feasibility of isolating perfluoropolyether oil from a PTFE-based lubricating grease matrix with supercritical CO2 at extraction conditions of 3500 psig and 60°C and illustrated generation of an extraction curve showing the relative amount of PFPE oil recovered as a function of the solvent (CO2)-to-feed (lubricating grease) ratio at the given extraction conditions.

    [0066] A 300 mL extraction vessel was charged with 234.2 g of DuPont Krytox® GPL 207 lubricating grease which was placed in two perforated metal baskets in the vessel. The extraction vessel and lubricating grease sample were flushed with CO2 and then pressurized to 3500 psig with CO2 at 60°C. The lubricating grease sample was extracted at these conditions and a CO2 flow rate of 2.0 g/min for 9h with intermittent PFPE oil samples collected from the extract. Table 1 shows the corresponding cumulative extraction yield as a function of the cumulative solvent-to-feed ratio, and this trend is further illustrated in Figure 2. A total of 75.2 wt % of the 185.2 g of PFPE oil in the starting lubricating grease was recovered in the extract with a total cumulative solvent-to-feed ratio of 6.36. FT-IR and 19F NMR analysis verified the recovered PFPE oils to be structurally identical to the original PFPE oils in the starting lubricating grease.
    Table 1. Solvent-to-Feed Ratio and Extraction Yield Data at 3500 psig and 60°C for Example 1
    Specific Solvent Ratio (g CO2/g Lubricating Grease)Extraction Yield (wt %)
    0.13 6.0
    0.32 13.1
    0.58 23.6
    1.09 37.2
    1.60 46.3
    2.15 52.8
    2.92 59.2
    3.69 64.2
    4.46 68.2
    5.32 72.0
    6.36 75.2

    EXAMPLE 2


    Extraction Curve at 4500 psig and 80°C using Supercritical CO2 with Krytox® GPL 227 Lubricating Grease



    [0067] This Example demonstrated the feasibility of isolating perfluoropolyether oil from a PTFE-based lubricating grease matrix with supercritical CO2 at extraction conditions of 4500 psig and 80°C.

    [0068] A 300 mL extraction vessel was charged with 232.5 g of DuPont Krytox® GPL 227 lubricating grease which was placed in two perforated metal baskets in the vessel. The extraction vessel and lubricating grease sample were flushed with CO2 and then pressurized to 4500 psig with CO2 at 80°C. The lubricating grease sample was extracted at these conditions and a CO2 flow rate of 2.1 g/min for 9h with intermittent PFPE oil samples collected from the extract. Table 2 shows the corresponding cumulative extraction yield as a function of the cumulative solvent-to-feed ratio, and this trend is further illustrated in Figure 3. A total of 95.1 wt % of the 183.4 g of PFPE oil in the starting lubricating grease was recovered in the extract with a total cumulative solvent-to-feed ratio of 6.54. FT-IR and 19F NMR analysis verified the recovered PFPE oils to be structurally identical to the original PFPE oils in the starting lubricating grease.
    Table 2. Solvent-to-Feed Ratio and Extraction Yield Data at 4500 psig and 80°C for Example 2
    Specific Solvent Ratio (g CO2/g Lubricating Grease)Extraction Yield (wt %)
    0.20 16.1
    0.37 23.4
    0.62 35.8
    1.15 50.6
    1.71 61.7
    2.24 69.5
    2.90 77.2
    3.55 82.6
    4.27 87.1
    5.48 92.1
    6.54 95.1

    EXAMPLE 3


    Extraction Curve at 1200 psig and 28°C using Liquid CO2 with Krytox® GPL 203 Lubricating Grease



    [0069] This Example demonstrated the feasibility of isolating perfluoropolyether oil from a PTFE-based lubricating grease matrix with liquid CO2 at extraction conditions of 1200 psig and 28°C.

    [0070] A 300 mL extraction vessel was charged with 229.7 g of DuPont Krytox® GPL 203 lubricating grease which was placed in two perforated metal baskets in the vessel. The extraction vessel and lubricating grease sample were flushed with CO2 and then pressurized to 1200 psig with liquid CO2 at 28°C. The lubricating grease sample was extracted at these conditions and a CO2 flow rate of 1.8 g/min for 2.7h with intermittent PFPE oil samples collected from the extract. Table 3 shows the corresponding cumulative extraction yield as a function of the cumulative solvent-to-feed ratio, and this trend is further illustrated in Figure 4. A total of 45.0 wt % of the 177.0 g of PFPE oil in the starting lubricating grease was recovered in the extract with a total cumulative solvent-to-feed ratio of 1.76. FT-IR and 19F NMR analysis verified the recovered PFPE oils to be structurally identical to the original PFPE oils in the starting lubricating grease.
    Table 3. Solvent-to-Feed Ratio and Extraction Yield Data at 1200 psig and 28°C for Example 3
    Specific Solvent Ratio (g CO2/g Lubricating Grease)Extraction Yield (wt %)
    0.09 4.7
    0.17 8.5
    0.33 15.1
    0.47 20.2
    0.64 25.7
    0.84 30.8
    1.04 34.7
    1.28 38.7
    1.54 42.1
    1.76 45.0

    EXAMPLE 4


    Extraction Curve at 2500 psig and 50°C using Supercritical CO2 with Krytox® GPL 227 Lubricating Grease



    [0071] This Example demonstrated the feasibility of isolating perfluoropolyether oil from a PTFE-based lubricating grease matrix with supercritical CO2 at extraction conditions of 2500 psig and 50°C.

    [0072] A 300 mL extraction vessel was charged with 208.0 g of DuPont Krytox® GPL 227 lubricating grease which was placed in two perforated metal baskets in the vessel. The extraction vessel and lubricating grease sample were flushed with CO2 and then pressurized to 2500 psig with CO2 at 50°C. The lubricating grease sample was extracted at these conditions and a CO2 flow rate of 1.9 g/min for 5.9h with intermittent PFPE oil samples collected from the extract. Table 4 shows the corresponding cumulative extraction yield as a function of the cumulative solvent-to-feed ratio, and this trend is further illustrated in Figure 5. A total of 50.8 wt % of the 164.0 g of PFPE oil in the starting lubricating grease was recovered in the extract with a total cumulative solvent-to-feed ratio of 4.7. FT-IR and 19F NMR analysis verified the recovered PFPE oils to be structurally identical to the original PFPE oils in the starting lubricating grease.
    Table 4. Solvent-to-Feed Ratio and Extraction Yield Data at 2500 psig and 50°C for Example 4
    Specific Solvent Ratio (g CO2/g Lubricating Grease)Extraction Yield (wt %)
    0.10 1.6
    0.16 3.5
    0.31 6.7
    0.39 9.2
    0.50 12.1
    0.77 18.6
    1.09 24.8
    1.55 29.6
    2.01 33.7
    2.64 38.7
    3.05 41.7
    3.57 45.0
    3.83 46.5
    4.70 50.8

    EXAMPLE 5


    Extraction Curve at 4500 psig and 80°C using Supercritical CO2 with Krytox® GPL 226SR Lubricating Grease



    [0073] This Example demonstrated the feasibility of isolating perfluoropolyether oil from a PTFE Micropowder-based lubricating grease matrix containing a proprietary additive with supercritical CO2 at extraction conditions of 4500 psig and 80°C.

    [0074] A 300 mL extraction vessel was charged with 102.9 g of DuPont Krytox® GPL 226SR lubricating grease which was placed in two perforated metal baskets in the vessel. The extraction vessel and lubricating grease sample were flushed with CO2 and then pressurized to 4500 psig with CO2 at 80°C. The lubricating grease sample was extracted at these conditions and a CO2 flow rate of 5.2 g/min for 3.7h with intermittent PFPE oil samples collected from the extract. Table 5 shows the corresponding cumulative extraction yield as a function of the cumulative solvent-to-feed ratio. A total of 95.5 wt % of the 77.7 g of PFPE oil in the starting lubricating grease was recovered in the extract with a total cumulative solvent-to-feed ratio of 11.1. FT-IR analysis verified the recovered PFPE oils to be structurally identical to the original PFPE oils in the starting lubricating grease.
    Table 5. Solvent-to-Feed Ratio and Extraction Yield Data at 4500 psig and 80°C for Example 5
    Specific Solvent Ratio (g CO2/g Lubricating Grease)Extraction Yield (wt %)
    0.25 17.3
    0.50 23.2
    0.75 27.9
    1.26 35.8
    2.01 46.6
    3.02 57.5
    4.02 66.4
    5.08 73.3
    7.04 82.1
    9.05 88.6
    10.1 90.9
    11.1 95.5

    EXAMPLE 6


    Extraction Curve at 4500 psig and 80°C using Supercritical CO2 with Krytox® NRT 8908 Lubricating Grease



    [0075] This Example demonstrated the feasibility of isolating perfluoropolyether oil from a talc-based lubricating grease matrix with supercritical CO2 at extraction conditions of 4500 psig and 80°C.

    [0076] A 300 mL extraction vessel was charged with 172.7 g of DuPont Krytox® NRT 8908 lubricating grease which was placed in two perforated metal baskets in the vessel. The extraction vessel and lubricating grease sample were flushed with CO2 and then pressurized to 4500 psig with CO2 at 80°C. The lubricating grease sample was extracted at these conditions and a CO2 flow rate of 5.2 g/min for 4.4h with intermittent PFPE oil samples collected from the extract. Table 6 shows the corresponding cumulative extraction yield as a function of the cumulative solvent-to-feed ratio. A total of 92.9 wt % of the 120.9 g of PFPE oil in the starting lubricating grease was recovered in the extract with a total cumulative solvent-to-feed ratio of 7.9. FT-IR analysis verified the recovered PFPE oils to be structurally identical to the original PFPE oils in the starting lubricating grease.
    Table 6. Solvent-to-Feed Ratio and Extraction Yield Data at 4500 psig and 80°C for Example 6
    Specific Solvent Ratio (g CO2/g Lubricating Grease)Extraction Yield (wt %)
    0.15 7.9
    0.30 13.1
    0.60 22.9
    0.90 33.5
    1.35 42.3
    1.80 49.8
    2.40 57.8
    2.99 64.3
    4.19 73.8
    5.39 80.6
    6.29 84.4
    7.04 86.9
    7.94 92.9

    EXAMPLE 7


    Extraction Curve at 4500 psig and 80°C using Supercritical CO2 with Krytox® GPL 407 Lubricating Grease



    [0077] This Example demonstrated the feasibility of isolating perfluoropolyether oil from a silica-based lubricating grease matrix with supercritical CO2 at extraction conditions of 4500 psig and 80°C.

    [0078] A 300 mL extraction vessel was charged with 146.7 g of DuPont Krytox® GPL 407 lubricating grease which was placed in two perforated metal baskets in the vessel. The extraction vessel and lubricating grease sample were flushed with CO2 and then pressurized to 4500 psig with CO2 at 80°C. The lubricating grease sample was extracted at these conditions and a CO2 flow rate of 5.2 g/min for 4.2h with intermittent PFPE oil samples collected from the extract. Table 7 shows the corresponding cumulative extraction yield as a function of the cumulative solvent-to-feed ratio. A total of 97.2 wt % of the 139.74 g of PFPE oil in the starting lubricating grease was recovered in the extract with a total cumulative solvent-to-feed ratio of 8.8. FT-IR analysis verified the recovered PFPE oils to be structurally identical to the original PFPE oils in the starting lubricating grease.
    Table 7. Solvent-to-Feed Ratio and Extraction Yield Data at 4500 psig and 80°C for Example 7
    Specific Solvent Ratio (g CO2/g Lubricating Grease)Extraction Yield (wt %)
    0.17 23.2
    0.35 32.8
    0.53 39.9
    0.88 52.2
    1.23 61.5
    1.76 68.2
    2.29 73.5
    3.00 79.3
    4.16 85.6
    5.47 90.1
    6.53 92.6
    7.24 93.9
    8.82 97.2

    EXAMPLE 8


    Extraction Curve at 4500 psig and 80°C using Supercritical CO2 with Krytox® XHT-BD Lubricating Grease



    [0079] This Example demonstrated the feasibility of isolating perfluoropolyether oil from a Boron Nitride-based lubricating grease matrix with supercritical CO2 at extraction conditions of 4500 psig and 80°C.

    [0080] A 300 mL extraction vessel was charged with 150.3 g of DuPont Krytox® XHT-BD lubricating grease which was placed in two perforated metal baskets in the vessel. The extraction vessel and lubricating grease sample were flushed with CO2 and then pressurized to 4500 psig with CO2 at 80°C. The lubricating grease sample was extracted at these conditions and a CO2 flow rate of 5.2 g/min for 4.2h with intermittent PFPE oil samples collected from the extract. Table 8 shows the corresponding cumulative extraction yield as a function of the cumulative solvent-to-feed ratio. A total of 89.5 wt % of the 117.0 g of PFPE oil in the starting lubricating grease was recovered in the extract with a total cumulative solvent-to-feed ratio of 8.6. FT-IR analysis verified the recovered PFPE oils to be structurally identical to the original PFPE oils in the starting lubricating grease.
    Table 8. Solvent-to-Feed Ratio and Extraction Yield Data at 4500 psig and 80°C for Example 8
    Specific Solvent Ratio (g CO2/g Lubricating Grease)Extraction Yield (wt %)
    0.17 18.3
    0.34 25.2
    0.52 29.9
    0.86 38.3
    1.21 45.4
    1.72 51.4
    2.24 56.6
    2.93 62.8
    4.06 70.6
    5.34 77.1
    6.37 81.1
    7.06 83.3
    8.61 89.5

    EXAMPLE 9


    Extraction Curve at 4500 psig and 80°C using Supercritical CO2 with Magnesium Stearate-thickened Krytox® GPL205 Lubricating Grease



    [0081] This Example demonstrated the feasibility of isolating perfluoropolyether oil from a Magnesium Stearate-based lubricating grease matrix with supercritical CO2 at extraction conditions of 4500 psig and 80°C.

    [0082] A 300 mL extraction vessel was charged with 154.7 g of a lubricating grease comprised of magnesium stearate and DuPont Krytox® GPL205 PFPE oil which was placed in two perforated metal baskets in the vessel. The extraction vessel and lubricating grease sample were flushed with CO2 and then pressurized to 4500 psig with CO2 at 80°C. The lubricating grease sample was extracted at these conditions and a CO2 flow rate of 5.2 g/min for 3.6 h with intermittent PFPE oil samples collected from the extract. Table 9 shows the corresponding cumulative extraction yield as a function of the cumulative solvent-to-feed ratio. A total of 99.8 wt % of the 126.9 g of PFPE oil in the starting lubricating grease was recovered in the extract with a total cumulative solvent-to-feed ratio of 7.2. FT-IR analysis verified the recovered PFPE oils to be structurally identical to the original PFPE oils in the starting lubricating grease.
    Table 9. Solvent-to-Feed Ratio and Extraction Yield Data at 4500 psig and 80°C for Example 9
    Specific Solvent Ratio (g CO2/g Lubricating Grease)Extraction Yield (wt %)
    0.17 13.4
    0.33 19.7
    0.50 24.8
    0.83 34.7
    1.17 42.2
    1.67 52.4
    2.17 62.4
    3.04 76.0
    3.94 85.4
    4.88 91.9
    6.25 97.0
    7.19 99.8

    EXAMPLE 10


    Extraction Curve at 4500 psig and 80°C using Supercritical CO2 with 50wt% Boron Nitride/50wt% PTFE Micropowder-thickened Krytox® GPL205 Lubricating Grease



    [0083] This Example demonstrated the feasibility of isolating perfluoropolyether oil from a Boron Nitride/PTFE-based lubricating grease matrix with supercritical CO2 at extraction conditions of 4500 psig and 80°C.

    [0084] A 300 mL extraction vessel was charged with 174.2 g of a lubricating grease comprised of Boron Nitride, PTFE Micropowder and DuPont Krytox® GPL205 PFPE oil which was placed in two perforated metal baskets in the vessel. The extraction vessel and lubricating grease sample were flushed with CO2 and then pressurized to 4500 psig with CO2 at 80°C. The lubricating grease sample was extracted at these conditions and a CO2 flow rate of 5.2 g/min for 5.0 h with intermittent PFPE oil samples collected from the extract. Table 10 shows the corresponding cumulative extraction yield as a function of the cumulative solvent-to-feed ratio. A total of 92.3 wt % of the 142.9 g of PFPE oil in the starting lubricating grease was recovered in the extract with a total cumulative solvent-to-feed ratio of 8.9. FT-IR analysis verified the recovered PFPE oils to be structurally identical to the original PFPE oils in the starting lubricating grease.
    Table 10. Solvent-to-Feed Ratio and Extraction Yield Data at 4500 psig and 80°C for Example 10
    Specific Solvent Ratio (g CO2/g Lubricating Grease)Extraction Yield (wt %)
    0.15 17.3
    0.30 25.3
    0.45 30.8
    0.75 41.9
    1.04 50.5
    1.49 57.1
    2.05 64.0
    2.88 72.5
    3.72 78.3
    4.61 82.7
    5.79 86.6
    6.69 88.4
    7.72 89.9
    8.91 92.3

    EXAMPLE 11


    Extraction Curve at 4500 psig and 80°C using Supercritical CO2 with Lubricating Grease comprised of Polyurea thickener with both a polyester and Krytox® 1531 PFPE oil



    [0085] This Example demonstrated the feasibility of isolating a polyester and a perfluoropolyether oil from a polyurea-based lubricating grease matrix with supercritical CO2 at extraction conditions of 4500 psig and 80°C.

    [0086] A 300 mL extraction vessel was charged with 115.84 g of a lubricating grease comprised of polyurea and a combination of a polyester and DuPont Krytox® 1531 PFPE oil which was placed in two perforated metal baskets in the vessel. The extraction vessel and lubricating grease sample were flushed with CO2 and then pressurized to 4500 psig with CO2 at 80°C. The lubricating grease sample was extracted at these conditions and a CO2 flow rate of 5.2 g/min for 3.3 h with intermittent PFPE oil samples collected from the extract. Table 11 shows the corresponding cumulative extraction yield as a function of the cumulative solvent-to-feed ratio. A total of 95.9 wt % of the 76.5 g of polyester and PFPE oil in the starting lubricating grease was recovered in the extract with a total cumulative solvent-to-feed ratio of 8.7. FT-IR analysis verified the recovered PFPE oils to be structurally identical to the original PFPE oils in the starting lubricating grease.
    Table 11. Solvent-to-Feed Ratio and Extraction Yield Data at 4500_psig and 80°C for Example 11
    Specific Solvent RatioExtraction Yield
    (g CO2/g Lubricating Grease)(wt %)
    0.22 16.8
    0.45 21.9
    0.67 25.9
    0.89 29.4
    1.34 36.4
    2.01 46.0
    2.99 58.2
    4.02 68.7
    4.91 76.3
    5.81 82.0
    6.70 86.9
    7.37 89.8
    8.71 95.9

    EXAMPLE 12


    Extraction Curve at 4500 psig and 80°C using Supercritical CO2 with Lubricating Grease comprised of Polyurea/Zinc Oxide thickener with both a polyester and Krytox® 1531 PFPE oil



    [0087] This Example demonstrated the feasibility of isolating a polyester and a perfluoropolyether oil from a polyurea and zinc oxide-based lubricating grease matrix with supercritical CO2 at extraction conditions of 4500 psig and 80°C.

    [0088] A 300 mL extraction vessel was charged with 119.98 g of a lubricating grease comprised of polyurea, zinc oxide, and a combination of a polyester and DuPont Krytox® 1531 PFPE oil which was placed in two perforated metal baskets in the vessel. The extraction vessel and lubricating grease sample were flushed with CO2 and then pressurized to 4500 psig with CO2 at 80°C. The lubricating grease sample was extracted at these conditions and a CO2 flow rate of 5.2 g/min for 2.8 h with intermittent PFPE oil samples collected from the extract. Table 12 shows the corresponding cumulative extraction yield as a function of the cumulative solvent-to-feed ratio. The 73.8 g of polyester and PFPE oil in the starting lubricating grease was recovered quantitatively in the extract with a total cumulative solvent-to-feed ratio of 7.3. FT-IR analysis verified the recovered PFPE oils to be structurally identical to the original PFPE oils in the starting lubricating grease.
    Table 12. Solvent-to-Feed Ratio and Extraction Yield Data at 4500_psig and 80°C for Example 12
    Specific Solvent RatioExtraction Yield
    (g CO2/g Lubricating Grease)(wt %)
    0.22 24.1
    0.43 32.3
    0.65 38.0
    0.86 42.5
    1.29 50.3
    1.94 61.1
    2.89 73.8
    3.88 83.8
    4.74 90.0
    5.61 94.4
    6.68 98.2
    7.33 100.0



    Claims

    1. A process for extracting a perfluoropolyether from a lubricating grease, comprising:

    (a) contacting a solvent comprising a liquid or supercritical carbon dioxide with the lubricating grease comprising a thickener and the perfluoropolyether in an extraction zone to form an extraction solution comprising an extracted perfluoropolyether; and

    (b) recovering the extracted perfluoropolyether from the extraction solution by evaporating the liquid or super critical carbon dioxide; wherein the recovered extracted perfluoropolyether comprises no more than about 2 wt % of the thickener.


     
    2. The process of claim 1, wherein the thickener is selected from the group consisting of PTFE, FEP, PFA, MFA, ETFE, PCTFE, ECTFE, PVDF, and combinations thereof.
     
    3. The process of claim 2, wherein the thickener is PTFE.
     
    4. The process of claim 1, wherein the thickener is selected from the group consisting of talc, silica, clay, boron nitride, titanium dioxide, silicon nitride, and combinations thereof.
     
    5. The process of claim 1, wherein the thickener is selected from the group consisting of metal soaps, melamine cyanurate, urea, polyureas, polyurethanes, polyolefins, and combinations thereof.
     
    6. The process of claim 5, wherein the metal soap is selected from the group consisting of lithium soaps, sodium soaps, lithium complex soaps, calcium sulfonates, aluminum soaps, and combinations thereof.
     
    7. The process of any one of claims 1 to 6, wherein the weight ratio of the solvent to the lubricating grease is no more than about 50, preferably no more than about 10, more preferably no more than about 7.
     
    8. The process of any one of claims 1 to 7, wherein the solvent comprises supercritical carbon dioxide.
     
    9. The process of claim 8, wherein the temperature in the extraction zone is from about 40 °C to about 110 °C.
     
    10. The process of claim 9, wherein the temperature in the extraction zone is from about 70 °C to about 90 °C.
     
    11. The process of any one of claims 8 to 10, wherein the pressure in the extraction zone is from about 1500 psig (103.4 bar) to about 6000 psig (413.7 bar) or from from about 2000 psig (137.9 bar) to about 6000 psig (413.7 bar).
     
    12. The process of claim 11, wherein the pressure in the extraction zone is from about 3000 psig (206.8 bar) to about 5000 psig (344.7 bar) or from about 4000 psig (275.8 bar) to about 5000 psig (344.7 bar).
     
    13. The process of any one of claims 1 to 7, wherein the solvent comprises liquid carbon dioxide.
     
    14. The process of claim 13, wherein the temperature in the extraction zone is from about 25 °C to less than 31.1 °C.
     
    15. The process of any one of claims 1 to 14, wherein the recovered extracted perfluoropolyether is further purified by an adsorbing agent.
     


    Ansprüche

    1. Verfahren zum Extrahieren eines Perfluorpolyethers aus einem Schmierfett, umfassend:

    (a) Kontaktieren eines Lösungsmittels umfassend ein flüssiges oder superkritisches Kohlendioxid mit dem Schmierfett umfassend ein Verdickungsmittel und den Perfluorpolyether in einer Extraktionszone, um eine Extraktionslösung zu bilden, die einen extrahierten Perfluorpolyether umfasst; und

    (b) Gewinnen des extrahierten Perfluorpolyethers aus der Extraktionslösung durch Verdampfen des flüssigen oder superkritischen Kohlendioxids; wobei der gewonnene extrahierte Perfluorpolyether nicht mehr als etwa 2 Gew.-% des Verdickungsmittels umfasst.


     
    2. Verfahren nach Anspruch 1, wobei das Verdickungsmittel aus der Gruppe ausgewählt ist bestehend aus PTFE, FEP, PFA, MFA, ETFE, PCTFE, ECTFE, PVDF und Kombinationen davon.
     
    3. Verfahren nach Anspruch 2, wobei das Verdickungsmittel PTFE ist.
     
    4. Verfahren nach Anspruch 1, wobei das Verdickungsmittel aus der Gruppe ausgewählt ist bestehend aus Talkum, Siliciumdioxid, Ton, Bornitrid, Titandioxid, Siliciumnitrid und Kombinationen davon.
     
    5. Verfahren nach Anspruch 1, wobei das Verdickungsmittel aus der Gruppe ausgewählt ist bestehend aus Metallseifen, Melamincyanurat, Harnstoff, Polyharnstoffen, Polyurethanen, Polyolefinen und Kombinationen davon.
     
    6. Verfahren nach Anspruch 5, wobei die Metallseife aus der Gruppe ausgewählt ist bestehend aus Lithiumseifen, Natriumseifen, Lithiumkomplexseifen, Calciumsulfonaten, Aluminiumseifen und Kombinationen davon.
     
    7. Verfahren nach einem der Ansprüche 1 bis 6, wobei das Gewichtsverhältnis des Lösungsmittels zu dem Schmierfett nicht mehr als etwa 50, bevorzugt nicht mehr als etwa 10, noch bevorzugter nicht mehr als etwa 7 beträgt.
     
    8. Verfahren nach einem der Ansprüche 1 bis 7, wobei das Lösungsmittel superkritisches Kohlendioxid umfasst.
     
    9. Verfahren nach Anspruch 8, wobei die Temperatur in der Extraktionszone etwa 40 °C bis etwa 110 °C beträgt.
     
    10. Verfahren nach Anspruch 9, wobei die Temperatur der Extraktionszone etwa 70 °C bis etwa 90 °C beträgt.
     
    11. Verfahren nach einem der Ansprüche 8 bis 10, wobei der Druck in der Extraktionszone etwa 1500 psig (103,4 bar) bis etwa 6000 psig (413,7 bar) oder etwa 2000 psig (137,9 bar) bis etwa 6000 psig (413,7 bar) beträgt.
     
    12. Verfahren nach Anspruch 11, wobei der Druck in der Extraktionszone etwa 3000 psig (206,8 bar) bis etwa 5000 psig (344,7 bar) oder etwa 4000 psig (275,8 bar) bis etwa 5000 psig (344,7 bar) beträgt.
     
    13. Verfahren nach einem der Ansprüche 1 bis 7, wobei das Lösungsmittel flüssiges Kohlendioxid umfasst.
     
    14. Verfahren nach Anspruch 13, wobei die Temperatur in der Extraktionszone etwa 25 °C bis weniger als 31,1 °C beträgt.
     
    15. Verfahren nach einem der Ansprüche 1 bis 14, wobei der gewonnene extrahierte Perfluorpolyether ferner durch ein Adsorptionsmittel gereinigt wird.
     


    Revendications

    1. Procédé d'extraction d'un polyéther perfluoré à partir d'une graisse lubrifiante, comprenant:

    (a) la mise en contact d'un solvant comprenant un dioxyde de carbone liquide ou supercritique avec la graisse lubrifiante comprenant un épaississant et le polyéther perfluoré dans une zone d'extraction pour former une solution d'extraction comprenant un polyéther perfluoré extrait; et

    (b) la récupération du polyéther perfluoré extrait de la solution d'extraction par évaporation du dioxyde de carbone liquide ou supercritique; le polyéther perfluoré extrait récupéré ne comprenant pas plus d'environ 2 % en pds de l'épaississant.


     
    2. Procédé selon la revendication 1, l'épaississant étant sélectionné dans le groupe constitué du PTFE, FEP, PFA, MFA, ETFE, PCTFE, ECTFE, PVDF, et de leurs combinaisons.
     
    3. Procédé selon la revendication 2, l'épaississant étant le PTFE.
     
    4. Procédé selon la revendication 1, l'épaississant étant sélectionné dans le groupe constitué du talc, de la silice, de l'argile, du nitrure de bore, du dioxyde de titane, du nitrure de silicium, et de leurs combinaisons.
     
    5. Procédé selon la revendication 1, l'épaississant étant sélectionné dans le groupe constitué des savons métalliques, du cyanurate de mélamine, de l'urée, des polyurées, des polyuréthanes, des polyoléfines, et de leurs combinaisons.
     
    6. Procédé selon la revendication 5, le savon métallique étant sélectionné dans le groupe constitué des savons de lithium, des savons de sodium, des savons de complexe de lithium, des sulfonates de calcium, des savons d'aluminium, et de leurs combinaisons.
     
    7. Procédé selon l'une quelconque des revendications 1 à 6, le rapport en poids du solvant à la graisse lubrifiante n'étant pas supérieur à environ 50, préférablement non supérieur à environ 10, plus préférablement non supérieur à environ 7.
     
    8. Procédé selon l'une quelconque des revendications 1 à 7, le solvant comprenant du dioxyde de carbone supercritique.
     
    9. Procédé selon la revendication 8, la température dans la zone d'extraction étant d'environ 40°C à environ 110°C.
     
    10. Procédé selon la revendication 9, la température dans la zone d'extraction étant d'environ 70°C à environ 90°C.
     
    11. Procédé selon l'une quelconque des revendications 8 à 10, la pression dans la zone d'extraction étant d'environ 1 500 lb/po2 (103,4 bars) à environ 6 000 lb/po2 (413,7 bars) ou d'environ 2 000 lb/po2 (137,9 bars) à environ 6 000 lb/po2 (413,7 bars).
     
    12. Procédé selon la revendication 11, la pression dans la zone d'extraction étant d'environ 3 000 lb/po2 (206,8 bars) à environ 5 000 lb/po2 (344,7 bars) ou d'environ 4 000 lb/po2 (275,8 bars) à environ 5 000 lb/po2 (344,7 bars).
     
    13. Procédé selon l'une quelconque des revendications 1 à 7, le solvant comprenant du dioxyde de carbone liquide.
     
    14. Procédé selon la revendication 13, la température dans la zone d'extraction étant d'environ 25°C à moins de 31,1°C.
     
    15. Procédé selon l'une quelconque des revendications 1 à 14, le polyéther perfluoré extrait récupéré étant en outre purifié par un agent adsorbant.
     




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    Cited references

    REFERENCES CITED IN THE DESCRIPTION



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    Non-patent literature cited in the description