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LUBRICATION METHOD WITH ALKOXYLATED PERFLUOROPOLYETHER

20170240839 · 2017-08-24

    Inventors

    Cpc classification

    International classification

    Abstract

    A lubrication method comprising applying to a surface to be lubricated a polymer comprising a partially or fully fluorinated, straight or branched, polyoxyalkylene chain (chain R.sub.f) having two chain ends, wherein one or both chain end(s) bear(s) a hydroxy- or alkoxy-terminated polyoxyalkylene chain free from fluorine atoms (chain R.sub.a), said chain comprising from 4 to 50 fluorine-free oxyalkylene units, said units being the same or different from one another and being selected from —CH.sub.2CH.sub.2O— and —CH.sub.2CH(J)O—, wherein J is independently straight or branched alkyl or aryl, with the proviso that, if both chain ends bear a hydroxy-terminated chain Ra comprising only —CH.sub.2CH.sub.2O— units, chain Rf does not consist only of —CF.sub.2CF.sub.2O-units. Lubricant compositions containing the polymer and methods for preparing the polymer are also herein disclosed.

    Claims

    1. A lubrication method comprising applying to a surface to be lubricated a polymer complying with formula (I) below:
    A-O—R.sub.f—(CF.sub.2).sub.x—CFZ—CH.sub.2—O—R.sub.a  (I) wherein: R.sub.f is a (per)fluoropolyoxyalkylene chain having an average number molecular weight M.sub.n ranging from 100 to 8,000, and comprising repeating units, which may be equal to or different from one another, selected from: (i) —CFXO—, wherein X is F or CF.sub.3, (ii) —CFXCFXO—, wherein X, equal or different at each occurrence, is F or CF.sub.3, with the proviso that at least one of X is —F, (iii) —CF.sub.2CF.sub.2CW.sub.2O—, wherein each of W, equal or different from each other, are F or H, (iv) —CF.sub.2CF.sub.2CF.sub.2CF.sub.2O—, (v) —(CF.sub.2).sub.j—CFZ′—O— wherein j is an integer from 0 to 3 and Z′ is general —OR.sub.f′T, wherein R.sub.f′ is a fluoropolyoxyalkene chain comprising a number of repeating units from 0 to 10, said repeating units being selected from: CFXO—, —CF.sub.2CFXO—, —CF.sub.2CF.sub.2CF.sub.2O—, —CF.sub.2CF.sub.2CF.sub.2CF.sub.2O—, with each of each of X being independently F or CF.sub.3 and T being a C.sub.1-C.sub.3 perfluoroalkyl group; Z is fluorine or CF.sub.3; x is 0 or 1, with the proviso that, when, x is 1, Z is F; A is —(CF.sub.2).sub.x—CFZ—CH.sub.2—O—R.sub.a, wherein x and Z are as defined above, or is a straight or branched C.sub.1-C.sub.4 perfluoroalkyl group wherein one fluorine atom can be substituted by one chlorine atom or one hydrogen atom, with the proviso that, if chlorine is present in group A, it is in a molar amount lower than 2% with respect to the overall amount of end groups and R.sub.a is a hydroxy-, alkoxy- or acyloxy-terminated polyoxyalkylene chain free from fluorine atoms (chain R.sub.a), said chain comprising from 4 to 50 fluorine-free oxyalkylene units, said units being the same or different from one another and being selected from —CH.sub.2CH.sub.2O—, —CH.sub.2CH(CH.sub.3)O—, —CH.sub.2CH(CH.sub.2CH.sub.3)O— and —CH.sub.2CH(Ph)O—, with the proviso that, if A is —(CF.sub.2).sub.x—CFZ—CH.sub.2—R.sub.a and chain R.sub.a is hydroxy-terminated and comprises only —CH.sub.2CH.sub.2O— units, chain R.sub.f does not consist only of —CF.sub.2CF.sub.2O— repeating units.

    2. The method according to claim 1, wherein chain R.sub.f in polymer (I) is selected from formulae (a)-(c) below:
    —(CF.sub.2O).sub.n(CF.sub.2CF.sub.2O).sub.m(CF.sub.2CF.sub.2CF.sub.2O).sub.p(CF.sub.2CF.sub.2CF.sub.2CF.sub.2O).sub.q—  (a) wherein m, n, p, q are 0 or integers selected in such a way as chain R.sub.f meets the above number average molecular weight requirement, with the proviso that if, p and q are simultaneously 0, n is not 0;
    —(CF.sub.2CF(CF.sub.3)O).sub.a(CF.sub.2CF.sub.2O).sub.b(CF.sub.2O).sub.c(CF(CF.sub.3)O).sub.d—  (b) wherein a, b, c, d are 0 or integers selected in such a way as chain R.sub.f meets the above number average molecular weight requirement; with the proviso that, at least one of a, c and d is not 0;
    —(CF.sub.2CF(CF.sub.3)O).sub.e(CF.sub.2O).sub.f(CF(CF.sub.3)O).sub.g—  (c) wherein e, f, g are 0 or integers selected in such a way as chain R.sub.f meets the above number average molecular weight requirement.

    3. The method according to claim 1, wherein chain R.sub.a in polymer (I) complies with formula (R.sub.a-I) below:
    —(CH.sub.2CH.sub.2O).sub.r(CH.sub.2CH(CH.sub.3)O).sub.s(CH.sub.2CH(CH.sub.2CH.sub.3)O).sub.t(CH.sub.2CH(Ph)O).sub.uR.sup.1  (R.sub.a-I) wherein r, s, t and u are independently selected from 0 and a positive number, with r+s+t+u ranging from 4 to 50, and R.sup.1 is selected from hydrogen, C.sub.1-C.sub.4 straight or branched alkyl, and —C(O)R.sup.2, wherein R.sup.2 is C.sub.1-C.sub.4 straight or branched (halo)alkyl, with the proviso that, if chain R.sub.f of compounds (I) comprises only —CF.sub.2CF.sub.2O— units and bears at both ends a chain (R.sub.a-I) wherein s, t and u are 0, R.sup.1 is not hydrogen.

    4. The method according to claim 3, wherein in chain (R.sub.a-I), r is a positive number ranging from 4 to 15, s, t and u are 0 and R.sup.1 is selected from hydrogen or methyl, with the proviso that, if chain R.sub.f of compounds (I) comprises only —CF.sub.2CF.sub.2O— units and bears at both ends a chain (R.sub.a-I), R.sup.1 is not hydrogen.

    5. The method according to claim 3, wherein, in chain (R.sub.a-I), r, t and u are 0, s is a positive number ranging from 4 to 15 and R.sup.1 is selected from hydrogen or methyl.

    6. The method according to claim 3, wherein in chain (R.sub.a-I), t and u are 0, r+s ranges from 4 to 15 and R.sup.1 is selected from hydrogen or methyl.

    7. The method according to claim 1, wherein polymer (I) complies with formula (I-A) below:
    R.sub.a—O—CH.sub.2—CF.sub.2—O—R.sub.f—CF.sub.2—CH.sub.2—O—R.sub.a  (I-A) wherein R.sub.a is a hydroxy-, alkoxy- or acyloxy-terminated polyoxyalkylene chain free from fluorine atoms (chain R.sub.a), said chain comprising from 4 to 50 fluorine-free oxyalkylene units, said units being the same or different from one another and being selected from —CH.sub.2CH.sub.2O—, —CH.sub.2CH(CH.sub.3)O—, —CH.sub.2CH(CH.sub.2CH.sub.3)O— and —CH.sub.2CH(Ph)O—, and R.sub.f complies with formula (a):
    —(CF.sub.2O).sub.n(CF.sub.2CF.sub.2O).sub.m(CF.sub.2CF.sub.2CF.sub.2O).sub.n(CF.sub.2CF.sub.2CF.sub.2CF.sub.2O).sub.q—  (a) wherein m, n, p, q are 0 or integers selected in such a way as chain R.sub.f meets the number average molecular weight requirement, with the proviso that if, p and q are simultaneously 0, n is not 0.

    8. A polymer complying with formula (I*)
    A-O—R.sub.f—(CF.sub.2).sub.x—CFZ—CH.sub.2—O—R.sub.a  (I*) wherein: R.sub.f is a (per)fluoropolyoxyalkylene chain having an average number molecular weight M.sub.n ranging from 100 to 8,000, and comprising repeating units, which may be equal to or different from one another, selected from (i) —CFXO—, wherein X is F or CF.sub.3, (ii) —CFXCFXO—, wherein X, equal or different at each occurrence, is F or CF.sub.3, with the proviso that at least one of X is —F, (iii) —CF.sub.2CF.sub.2CW.sub.2O—, wherein each of W, equal or different from each other, are F or H, (iv) —CF.sub.2CF.sub.2CF.sub.2CF.sub.2O—, (v) —(CF.sub.2).sub.j—CFZ′—O— wherein j is an integer from 0 to 3 and Z′ is —OR.sub.f′T, wherein R.sub.f′ is a fluoropolyoxyalkene chain comprising a number of repeating units from 0 to 10, said repeating units being selected from: CFXO—, —CF.sub.2CFXO—, —CF.sub.2CF.sub.2CF.sub.2O—, —CF.sub.2CF.sub.2CF.sub.2CF.sub.2O—, with each of each of X being independently F or CF.sub.3, and T being a C.sub.1-C.sub.3 perfluoroalkyl group; Z is fluorine or CF.sub.3; x is 0 or 1, with the proviso that, when, x is 1, Z is F; A is (CF.sub.2).sub.x—CFZ—CH.sub.2—O—R.sub.a, wherein x and Z are as defined above, or is selected from straight or branched C.sub.1-C.sub.4 perfluoroalkyl groups wherein one fluorine atom can be substituted by one chlorine atom or one hydrogen atom, with the proviso that, if chlorine is present in group A, it is in a molar amount lower than 2% with respect to the overall amount of end groups and R.sub.a complies with formula (R.sub.a-I*) below:
    —(CH.sub.2CH.sub.2O).sub.r(CH.sub.2CH(CH.sub.3)O).sub.s(CH.sub.2CH(CH.sub.2CH.sub.3)O).sub.t(CH.sub.2CH(Ph)O).sub.uR.sup.1  (R.sub.a-I*) wherein: r, s, t and u are independently selected from 0 and a positive number and r+s+t+u is a positive number ranging from 4 to 50; and R.sup.1 is selected from hydrogen, C.sub.1-C.sub.4 straight or branched alkyl, and —C(O)R.sup.2, wherein R.sup.2 is C.sub.1-C.sub.4 straight or branched (halo)alkyl, with the proviso that, when R.sup.1 is hydrogen, at least one of s, t and u is not 0.

    9. The polymer according to claim 8 wherein chain R.sub.f is selected from formulae (a*)-(c*) here below:
    —(CF.sub.2O).sub.n(CF.sub.2CF.sub.2O).sub.mCF.sub.2CF.sub.2CF.sub.2O).sub.p(CF.sub.2CF.sub.2CF.sub.2CF.sub.2O).sub.q—  (a*) wherein m, n, p, q are 0 or integers selected in such a way as chain R.sub.f meets the above number average molecular weight requirement;
    —(CF.sub.2CF(CF.sub.3)O).sub.a(CF.sub.2CF.sub.2O).sub.b(CF.sub.2O).sub.c(CF(CF.sub.3)O).sub.d—  (b*) wherein a, b, c, d are 0 or integers selected in such a way as chain R.sub.f meets the above number average molecular weight requirement; with the proviso that, at least one of a, c and d is not 0;
    —(CF.sub.2CF(CF.sub.3)O).sub.e(CF.sub.2O).sub.f(CF(CF.sub.3)O).sub.g—  (c*) wherein e, f, g are 0 or integers selected in such a way as chain R.sub.f meets the above number average molecular weight requirement.

    10. The polymer according to claim 8, which is a polymer of formula (I*-A) below
    R.sub.a—O—CH.sub.2—CF.sub.2—O—R.sub.f—CF.sub.2—CH.sub.2—O—R.sub.a  (I*-A) wherein: R.sub.a complies with formula (R.sub.a-I*) below:
    —(CH.sub.2CH.sub.2O).sub.r(CH.sub.2CH(CH.sub.3)O).sub.s(CH.sub.2CH(CH.sub.2CH.sub.3)O).sub.t(CH.sub.2CH(Ph)O).sub.uR.sup.1  (R.sub.a-I*) wherein: r, s, t and u are independently selected from 0 and a positive number and r+s+t+u is a positive number ranging from 4 to 50; and R.sup.1 is selected from hydrogen, C.sub.1-C.sub.4 straight or branched alkyl, and —C(O)R.sup.2, wherein R.sup.2 is C.sub.1-C.sub.4 straight or branched (halo)alkyl, with the proviso that, when R.sup.1 is hydrogen, at least one of s, t and u is not 0 and R.sub.f complies with formula (a*):
    —(CF.sub.2O).sub.n(CF.sub.2CF.sub.2O).sub.m(CF.sub.2CF.sub.2O).sub.p(CF.sub.2CF.sub.2CF.sub.2CF.sub.2O).sub.q—  (a*) wherein m, n, p, q are 0 or integers selected in such a way as chain R.sub.f meets the number average molecular weight requirement.

    11. The polymer according to claim 10 wherein r, t and u in formula (R.sub.a-I*) are 0 and s is a positive number ranging from 4 to 15.

    12. The polymer according to claim 10 wherein in formula (R.sub.a-I*) r+s is a positive number ranging from 4 to 15 and t and u are 0.

    13. A composition comprising: (a) a polymer as defined in claim 8; in admixture with one or more of (b) a lubricant base oil; (c) a thickening agent; (d) an additive; and optionally (e) a solvent.

    14. The method according to claim 1, wherein R.sub.f is a (per)fluoropolyoxyalkylene chain having an average number molecular weight M.sub.n ranging from 800 to 3,000.

    15. The method according to claim 1, wherein R.sub.f consists of repeating units, which may be equal to or different from one another, selected from: (i) —CFXO—, wherein X is F or CF.sub.3, (ii) —CFXCFXO—, wherein X, equal or different at each occurrence, is F or CF.sub.3, with the proviso that at least one of X is —F, (iii) —CF.sub.2CF.sub.2CW.sub.2O—, wherein each of W, equal or different from each other, are F or H, (iv) —CF.sub.2CF.sub.2CF.sub.2CF.sub.2O—, (v) —(CF.sub.2).sub.j—CFZ′—O— wherein j is an integer from 0 to 3 and Z′ is —OR.sub.f′T, wherein R.sub.f′ is a fluoropolyoxyalkene chain comprising a number of repeating units from 0 to 10, said repeating units being selected from: —CFXO—, —CF.sub.2CFXO—, —CF.sub.2CF.sub.2CF.sub.2O—, —CF.sub.2CF.sub.2CF.sub.2CF.sub.2O—, with each of each of X being independently F or CF.sub.3 and T being a C.sub.1-C.sub.3 perfluoroalkyl group.

    16. The method according to claim 2, wherein the m/n ratio is between 0.1 and 20 when m is other than 0; (p+q)/(m+n) is between 0 and 0.2 when (m+n) is other than 0; a/b is between 0.1 and 10 when b is other than 0; (c+d)/(a+b) is between 0.01 and 0.5 when (a+b) is other than 0; and (f+g)/e is between 0.01 and 0.5 when e is other than 0

    17. The polymer according to claim 8, wherein R.sub.f is a (per)fluoropolyoxyalkylene chain having an average number molecular weight M.sub.n ranging from 800 to 3,000.

    18. The polymer according to claim 8, wherein R.sub.f consists of repeating units, which may be equal to or different from one another, selected from: (i) —CFXO—, wherein X is F or CF.sub.3, (ii) —CFXCFXO—, wherein X, equal or different at each occurrence, is F or CF.sub.3, with the proviso that at least one of X is —F, (iii) —CF.sub.2CF.sub.2CW.sub.2O—, wherein each of W, equal or different from each other, are F or H, (iv) —CF.sub.2CF.sub.2CF.sub.2CF.sub.2O—, (v) —(CF.sub.2).sub.j—CFZ′—O— wherein j is an integer from 0 to 3 and Z′ is —OR.sub.f′T, wherein R.sub.f′ is a fluoropolyoxyalkene chain comprising a number of repeating units from 0 to 10, said repeating units being selected from: —CFXO—, —CF.sub.2CFXO—, —CF.sub.2CF.sub.2CF.sub.2O—, —CF.sub.2CF.sub.2CF.sub.2CF.sub.2O—, with each of each of X being independently F or CF.sub.3 and T being a C.sub.1-C.sub.3 perfluoroalkyl group.

    19. The polymer according to claim 9, wherein the m/n ratio is between 0.1 and 20 when m is other than 0; (p+q)/(m+n) is between 0 and 0.2 when (m+n) is other than 0; a/b is between 0.1 and 10 when b is other than 0; (c+d)/(a+b) is between 0.01 and 0.5 when (a+b) is other than 0; and (f+g)/e is between 0.01 and 0.5 when e is other than 0.

    Description

    BRIEF DESCRIPTION OF DRAWINGS

    [0027] FIG. 1 illustrates the results of a thermogravimetric analysis (TGA) carried out on two polymers according to the present invention.

    SUMMARY OF INVENTION

    [0028] The Applicant has now surprisingly found out that polymers comprising a (per)fluoropolyether chain having two chain ends, wherein one or both chain ends bear a definite number of oxyalkylene units free from fluorine atoms show higher thermal stability, improved lubrication properties (such as lower wear) and improved performances at extreme pressures with respect to PAGs. It has also been observed that such polymers are endowed with improved compatibility with PAGs. Therefore, they are suitable for use in lubrication methods comprising applying such polymers or compositions containing them to a surface to be lubricated.

    [0029] The polymers for use in the method of the invention comprise a partially or fully fluorinated, straight or branched, polyoxyalkylene chain (chain R.sub.f) having two chain ends, wherein one or both chain end(s) bear(s) a hydroxy-, alkoxy- or acyloxy-terminated polyoxyalkylene chain free from fluorine atoms (chain R.sub.a), said chain comprising from 4 to 50 fluorine-free oxyalkylene units, said units being the same or different from one another and being selected from —CH.sub.2CH.sub.2O— and —CH.sub.2CH(J)O—, wherein J is independently straight or branched alkyl or aryl, preferably methyl, ethyl or phenyl, with the proviso that, if both chain ends bear a hydroxy-terminated chain R.sub.a comprising only —CH.sub.2CH.sub.2O— units, chain R.sub.f does not consist only of —CF.sub.2CF.sub.2O— units.

    [0030] The polymers for use in the method of the invention will be herein after also generically referred to as “PFPE-PAGs” and, more specifically, as “mono- or bi-functional” PFPE-PAGs, depending on whether one or both chain ends bear a chain R.sub.a.

    [0031] The invention further relates to lubricant compositions comprising the PFPE-PAGs and to methods for preparing the PFPE-PAGs.

    Definitions

    [0032] For the purposes of the present description, the term “(per)fluoropolyether” stands for “fully or partially fluorinated polyether”.

    [0033] The acronym PFPE stands for (per)fluoropolyether.

    [0034] The term “(halo)alkyl” denotes a hydrocarbon group wherein one or more hydrogens can be replaced by one or more halogen atoms, preferably fluorine atoms.

    [0035] The indefinite article “a” stands for “one or more”, unless indicated otherwise. Substantives in the plural form are to be construed as including also the singular form, i.e. as “one or more”, unless indicated otherwise. For example, the term “compounds” is to be construed as “a compound” or “one or more compounds”, unless indicated otherwise.

    [0036] When ranges are indicated, range extremes are included.

    [0037] Typically, the PFPE-PAGs for use in the method of the invention comply with formula (I) below:


    A-O—R.sub.f—(CF.sub.2).sub.x—CFZ—CH.sub.2—O—R.sub.a  (I)

    wherein: [0038] R.sub.f is a (per)fluoropolyoxyalkylene chain having an average number molecular weight M.sub.n ranging from 100 to 8,000, preferably from 300 to 6,000, more preferably from 800 to 3,000, and comprising, preferably consisting of, repeating units, which may be equal to or different from one another, selected from:

    [0039] (i) —CFXO—, wherein X is F or CF.sub.3,

    [0040] (ii) —CFXCFXO—, wherein X, equal or different at each occurrence, is F or CF.sub.3, with the provision that at least one of X is —F,

    [0041] (iii) —CF.sub.2CF.sub.2CW.sub.2O—, wherein each of W, equal or different from each other, are F or H,

    [0042] (iv) —CF.sub.2CF.sub.2CF.sub.2CF.sub.2O—,

    [0043] (v) —(CF.sub.2).sub.j—CFZ′—O— wherein j is an integer from 0 to 3 and Z′ is a group of general formula —OR.sub.f′T, wherein R.sub.f′ is a fluoropolyoxyalkene chain comprising a number of repeating units from 0 to 10, said recurring units being chosen among the followings: —CFXO—, —CF.sub.2CFXO—, —CF.sub.2CF.sub.2CF.sub.2O—, —CF.sub.2CF.sub.2CF.sub.2CF.sub.2O—, with each of each of X being independently F or CF.sub.3 and T being a C.sub.1-C.sub.3 perfluoroalkyl group; [0044] Z is fluorine or CF.sub.3; [0045] x is 0 or 1, with the proviso that, when, x is 1, Z is F; [0046] A is —(CF.sub.2).sub.x—CFZ—CH.sub.2—O—R.sub.a, wherein x and Z are as defined above, or is a straight or branched C.sub.1-C.sub.4 perfluoroalkyl group wherein one fluorine atom can be substituted by one chlorine atom or one hydrogen atom, with the proviso that, if chlorine is present in group A, it is in a molar amount lower than 2% with respect to the overall amount of end groups and [0047] R.sub.a is a hydroxy-, alkoxy- or acyloxy-terminated polyoxyalkylene chain free from fluorine atoms (chain R.sub.a), said chain comprising from 4 to 50 fluorine-free oxyalkylene units, said units being the same or different from one another and being selected from —CH.sub.2CH.sub.2O— and —CH.sub.2CH(J)O—, wherein J is as defined above

    [0048] with the proviso that, if A is —(CF.sub.2).sub.x—CFZ—CH.sub.2—R.sub.a and chain R.sub.a is hydroxy-terminated and comprises only —CH.sub.2CH.sub.2O— units, chain R.sub.f does not consist only of —CF.sub.2CF.sub.2O— repeating units.

    [0049] Preferred R.sub.f chains in the PFPE-PAGs of formula (I) are those selected from formulae (a)-(c) here below:


    —(CF.sub.2O).sub.n(CF.sub.2CF.sub.2O).sub.m(CF.sub.2CF.sub.2CF.sub.2O).sub.p(CF.sub.2CF.sub.2CF.sub.2CF.sub.2O).sub.q—  (a)

    wherein m, n, p, q are 0 or integers selected in such a way as chain R.sub.f meets the above number average molecular weight requirement, with the proviso that if, p and q are simultaneously 0, n is not 0; when m is other than 0, the m/n ratio is preferably between 0.1 and 20; when (m+n) is other than 0, (p+q)/(m+n) is preferably between 0 and 0.2;


    —(CF.sub.2CF(CF.sub.3)O).sub.a(CF.sub.2CF.sub.2O).sub.b(CF.sub.2O).sub.c(CF(CF.sub.3)O).sub.d—  (b)

    wherein a, b, c, d are 0 or integers selected in such a way as chain R.sub.f meets the above number average molecular weight requirement; with the proviso that, at least one of a, c and d is not 0; when b is other than 0, a/b is preferably between 0.1 and 10; when (a+b) is different from 0 (c+d)/(a+b) preferably is between 0.01 and 0.5, more preferably between 0.01 and 0.2;


    —(CF.sub.2CF(CF.sub.3)O).sub.e(CF.sub.2O).sub.f(CF(CF.sub.3)O).sub.g—  (c)

    wherein e, f, g are 0 or integers selected in such a way as chain R.sub.f meets the above number average molecular weight requirement; when e is other than 0, (f+g)/e is preferably between 0.01 and 0.5, more preferably between 0.01 and 0.2.

    [0050] PFPE-PAGs of formula (I) wherein chain R.sub.f complies with formula (a) as defined above are particularly preferred in the method of the invention.

    [0051] Typically, in the PFPE-PAGs of formula (I), chain R.sub.a complies with formula

    [0052] (R.sub.a-I) below:


    —(CH.sub.2CH.sub.2O).sub.r(CH.sub.2CH(CH.sub.3)O).sub.s(CH.sub.2CH(CH.sub.2CH.sub.3)O).sub.t(CH.sub.2CH(Ph)O).sub.uR.sup.1  (R.sub.a-I)

    wherein r, s, t and u are independently selected from 0 and a positive number, with r+s+t+u ranging from 4 to 50, preferably from 4 to 15, more preferably from 4 to 10, and R.sup.1 is selected from hydrogen, C.sub.1-C.sub.4 straight or branched alkyl, preferably methyl, and —C(O)R.sup.2, wherein R.sup.2 is C.sub.1-C.sub.4 straight or branched (halo)alkyl, with the proviso that, if chain R.sub.f of compounds (I) comprises only —CF.sub.2CF.sub.2O— units and bears at both ends a chain (R.sub.a-I) wherein s, t and u are 0, R.sup.1 is not hydrogen.

    [0053] In one preferred embodiment, in chain (R.sub.a-I), r is a positive number ranging from 4 to 15, preferably from 4 to 10, s, t and u are 0 and R.sup.1 is selected from hydrogen or methyl, with the proviso that, if chain R.sub.f of compounds (I) comprises only —CF.sub.2CF.sub.2O— units and bears at both ends a chain (R.sub.a-I), R.sup.1 is not hydrogen.

    [0054] In another preferred embodiment, r, t and u are 0, s is a positive number ranging from 4 to 15, preferably from 4 to 10, and R.sup.1 is selected from hydrogen or methyl.

    [0055] In another preferred embodiment, r and s are positive numbers and t and u are 0, r+s ranges from 4 to 15, preferably from 4 to 10, and R.sup.1 is selected from hydrogen or methyl.

    [0056] When two or more of the —CH.sub.2CH.sub.2O—, —CH.sub.2CH(CH.sub.3)O—, —CH.sub.2CH(CH.sub.2CH.sub.3)O— and —CH.sub.2CH(Ph)O— units are present in chain (R.sub.a-I), they can be arranged in blocks or they can be disposed at random.

    [0057] According to one preferred embodiment, the PFPE-PAGs are bifunctional PFPE-PAGs complying with formula (I-A) below:


    R.sub.a—O—CH.sub.2—CF.sub.2—O—R.sub.f—CF.sub.2—CH.sub.2—O—R.sub.a  (I-A)

    wherein: [0058] R.sub.a is as defined above and [0059] R.sub.f complies with formula (a) as defined above.

    [0060] According to another preferred embodiment, the PFPE-PAGs are monofunctional PFPE-PAGs complying with formula (I-B) below:


    A-O—R.sub.f—CF.sub.2—CH.sub.2—O—R.sub.a  (I-B)

    wherein: [0061] A is a straight or branched C.sub.1-C.sub.4 perfluoroalkyl group wherein one fluorine atom can be substituted by one chlorine atom or one hydrogen atom, with the proviso that, if chlorine is present in group A, it is in a molar amount lower than 2% with respect to the overall amount of end groups, [0062] R.sub.a is as defined above and [0063] R.sub.f complies with formula (a) as defined above.

    [0064] In the method of the invention, bifunctional PFPE-PAGs of formula (I-A) are preferred.

    [0065] A preferred group of PFPE-PAGs of formula (I) complies with formula (I*) below:


    A-O—R.sub.f—(CF.sub.2).sub.x—CFZ—CH.sub.2—O—R.sub.a  (I*)

    wherein: [0066] R.sub.f is a (per)fluoropolyoxyalkylene chain having an average number molecular weight M.sub.n ranging from 100 to 8,000, preferably from 300 to 6,000, more preferably from 800 to 3,000, and comprising, preferably consisting of, repeating units, which may be equal to or different from one another, selected from

    [0067] (i) —CFXO—, wherein X is F or CF.sub.3,

    [0068] (ii) —CFXCFXO—, wherein X, equal or different at each occurrence, is F or CF.sub.3, with the proviso that at least one of X is —F,

    [0069] (iii) —CF.sub.2CF.sub.2CW.sub.2O—, wherein each of W, equal or different from each other, are F or H,

    [0070] (iv) —CF.sub.2CF.sub.2CF.sub.2CF.sub.2O—,

    [0071] (v) —(CF.sub.2).sub.j—CFZ′—O— wherein j is an integer from 0 to 3 and Z′ is a group of general formula —OR.sub.f′T, wherein R.sub.f′ is a fluoropolyoxyalkene chain comprising a number of repeating units from 0 to 10, said recurring units being chosen among the followings: —CFXO—, —CF.sub.2CFXO—, —CF.sub.2CF.sub.2CF.sub.2O—, —CF.sub.2CF.sub.2CF.sub.2CF.sub.2O—, with each of each of X being independently F or CF.sub.3, and T being a C.sub.1-C.sub.3 perfluoroalkyl group; [0072] Z is fluorine or CF.sub.3; [0073] x is 0 or 1, with the proviso that, when, x is 1, Z is F; [0074] A is (CF.sub.2).sub.x—CFZ—CH.sub.2—O—R.sub.a, wherein x and Z are as defined above, or is selected from straight or branched C.sub.1-C.sub.4 perfluoroalkyl groups wherein one fluorine atom can be substituted by one chlorine atom or one hydrogen atom, with the proviso that, if chlorine is present in group A, it is in a molar amount lower than 2% with respect to the overall amount of end groups and [0075] R.sub.a complies with formula (R.sub.a-I*) below:


    —(CH.sub.2CH.sub.2O).sub.r(CH.sub.2CH(CH.sub.3)O).sub.s(CH.sub.2CH(CH.sub.2CH.sub.3)O).sub.t(CH.sub.2CH(Ph)O).sub.uR.sup.1  (R.sub.a-I*)

    wherein: [0076] r, s, t and u are independently selected from 0 and a positive number and r+s+t+u is a positive number ranging from 4 to 50, preferably from 4 to 15, more preferably from 4 to 10; and [0077] R.sup.1 is selected from hydrogen, C.sub.1-C.sub.4 straight or branched alkyl, and —C(O)R.sup.2, wherein R.sup.2 is C.sub.1-C.sub.4 straight or branched (halo)alkyl, with the proviso that, when R.sup.1 is hydrogen, at least one of s, t and u is not 0.

    [0078] Preferred R.sub.f chains in the PFPE-PAGs of formula (I*) are those selected from formulae (a*)-(c*) here below:


    —(CF.sub.2O).sub.n(CF.sub.2CF.sub.2O).sub.m(CF.sub.2CF.sub.2CF.sub.2O).sub.p(CF.sub.2CF.sub.2CF.sub.2CF.sub.2O).sub.q—  (a*)

    wherein m, n, p, q are 0 or integers selected in such a way as chain R.sub.f meets the above number average molecular weight requirement; when m is other than 0, the m/n ratio is preferably between 0.1 and 20; when (m+n) is other than 0, (p+q)/(m+n) is preferably between 0 and 0.2;


    —(CF.sub.2CF(CF.sub.3)O).sub.a(CF.sub.2CF.sub.2O).sub.b(CF.sub.2O).sub.c(CF(CF.sub.3)O).sub.d—  (b*)

    wherein a, b, c, d are 0 or integers selected in such a way as chain R.sub.f meets the above number average molecular weight requirement; with the proviso that, at least one of a, c and d is not 0; when b is other than 0, a/b is preferably between 0.1 and 10; when (a+b) is different from 0 (c+d)/(a+b) preferably is between 0.01 and 0.5, more preferably between 0.01 and 0.2;


    —(CF.sub.2CF(CF.sub.3)O).sub.e(CF.sub.2O).sub.f(CF(CF.sub.3)O).sub.g—  (c*)

    wherein e, f, g are 0 or integers selected in such a way as chain R.sub.f meets the above number average molecular weight requirement; when e is other than 0, (f+g)/e is preferably between 0.01 and 0.5, more preferably between 0.01 and 0.2.

    [0079] A first group of preferred compounds (I*) complies with formula (I*-A) below:


    R.sub.a—O—CH.sub.2—CF.sub.2—O—R.sub.f—CF.sub.2—CH.sub.2—O—R.sub.a  (I*-A)

    in which: [0080] R.sub.f complies with formulae (a*)-(c*) as defined above; and [0081] R.sub.a complies with formula (R.sub.a-I*) as defined above.

    [0082] Preferably, in compounds (I*-A), chain R.sub.f complies with formula (a*).

    [0083] A second group of compounds (I*) complies with formula (I*-B) below:


    A-O—R.sub.f—CF.sub.2—CH.sub.2—O—R.sub.a  (I*-B)

    in which: [0084] R.sub.f complies with formulae (a*)-(c*) as defined above; and [0085] R.sub.a complies with formula (R.sub.a-I*) as defined above, and A is a straight or branched C.sub.1-C.sub.4 perfluoroalkyl group wherein one fluorine atom can be substituted by one chlorine atom or one hydrogen atom, with the proviso that, if chlorine is present in group A, it is in a molar amount lower than 2% with respect to the overall amount of end groups,

    [0086] Preferably, in compounds (I*-B), chain R.sub.f complies with formula (a*).

    [0087] Preferred compounds (I*-A) and (I*-B) are those wherein r, t and u are 0 and s is a positive number ranging from 4 to 15, preferably from 4 to 10, and those wherein r+s is a positive number ranging from 4 to 15, preferably from 4 to 10, and t and u are 0.

    [0088] Preferably, in compounds (I*-A) and (I*-B), R.sup.1 is methyl or C(O)CH.sub.3.

    [0089] PFPE-PAGs of formula (I*) represent a further aspect of the present invention.

    [0090] The PFPE-PAGs for use in the method of the invention can be obtained by reaction of a mono- or bi-functional PFPE alcohol with an alkoxylating agent in such an amount as to obtain from 4 to 50, preferably from 4 to 15, more preferably from 4 to 10, oxyalkylene units at one or both chain ends.

    [0091] For the purposes of the obtainment of the PFPE-PAGs of formula (I), the mono- or bi-functional PFPE alcohol complies with formula (II) below:


    Y—O—R.sub.f—(CF.sub.2).sub.x—CFZ—CH.sub.2—OH  (II)

    wherein: [0092] R.sub.f, x and Z are as defined above; [0093] Y is (CF.sub.2).sub.x—CFZ—CH.sub.2—OH, wherein x and Z are as defined above, or is selected from straight or branched C.sub.1-C.sub.4 perfluoroalkyl groups wherein one fluorine atom can be substituted by one chlorine atom or one hydrogen atom, with the proviso that, if chlorine is present in group A, it is in a molar amount lower than 2% with respect to the overall amount of end groups and

    [0094] the alkoxylating agent is selected from ethylene oxide, propylene oxide, 1,2-butylene oxide and styrene oxide and a mixture of two or more thereof.

    [0095] Specifically, bifunctional PFPE-PAGs (I-A) wherein chain R.sub.a complies with formula (R.sub.a-I) as defined above wherein R.sup.1 is hydrogen can be obtained by reaction of a bifunctional PFPE alcohol of formula (II-A) below:


    HO—CH.sub.2—CF.sub.2—O—R.sub.f—CF.sub.2—CH.sub.2—OH  (II-A)

    wherein R.sub.f complies with formula (a) as defined above
    with ethylene oxide, propylene oxide, 1,2-butylene oxide, styrene oxide or with a mixture of two or more thereof.

    [0096] Monofunctional PFPE-PAGs (I-B) wherein chain R.sub.a complies with formula (R.sub.a-I) as defined above wherein R.sup.1 is hydrogen can instead be obtained by reaction of a monofunctional PFPE alcohol of formula (II-B) below:


    A-O—R.sub.f—CF.sub.2—CH.sub.2—OH  (II-B)

    wherein R.sub.f complies with formula (a) as defined above and A is a straight or branched C.sub.1-C.sub.4 perfluoroalkyl group wherein one fluorine atom can be substituted by one chlorine atom or one hydrogen atom, with the proviso that, if chlorine is present in group A, it is in a molar amount lower than 2% with respect to the overall amount of end groups
    with ethylene oxide, propylene oxide, 1,2-butylene oxide, styrene oxide or with a mixture of two or more thereof.

    [0097] Mono- and bifunctional PFPE-PAGs wherein chain R.sub.a complies with formula (R.sub.a-I) in which R.sup.1 is C.sub.1-C.sub.4-straight or branched alkyl can be obtained according to known methods by alkylation of the corresponding mono- and bifunctional PFPE-PAGs wherein chain R.sub.a complies with formula (R.sub.a-I) in which R.sup.1 is hydrogen.

    [0098] Mono- and bifunctional PFPE-PAGs wherein chain R.sub.a complies with formula (R.sub.a-I) in which R.sup.1 is —C(O)R.sup.2 as defined above can be obtained according to known methods by acylation the corresponding mono- and bifunctional PFPE-PAGs wherein chain R.sub.a complies with formula (R.sub.a-I) in which R.sup.1 is hydrogen.

    [0099] PFPE alcohols of formula (II-A) or (II-B) can be manufactured by chemical reduction of corresponding PFPE carboxylic acids or esters according to several methods known in the art, using reducing agents such as NaBH.sub.4, or by catalytic hydrogenation, as disclosed, for example, in U.S. Pat. No. 6,509,509 (AUSIMONT SPA) Jul. 5, 2001, U.S. Pat. No. 6,573,411 (AUSIMONT SPA) Nov. 21, 2002, WO 2008/122639 (SOLVAY SOLEXIS SPA) Oct. 16, 2008. Precursors of PFPE carboxylic acids or of PFPE esters can be manufactured according to different methods, e.g. by oxypolymerization of fluoroolefins or by ring opening polymerization of HFPO (hexafluoropropylene oxide), as taught in U.S. Pat. No. 3,847,978 (MONTEDISON SPA) Nov. 12, 1974, U.S. Pat. No. 3,766,251 (MONTEDISON SPA) Oct. 16, 1973, U.S. Pat. No. 3,715,378 (MONTEDISON SPA) Feb. 6, 1973, U.S. Pat. No. 3,665,041 (MONTEDISON SPA) May 23, 1972, U.S. Pat. No. 4,647,413 (MINESOTA MINING & MFG) Mar. 3, 1987, EP 151877 A (MINNESOTA MINING & MFG) Aug. 21, 1985, U.S. Pat. No. 3,442,942 (MONTEDISON SPA) May 6, 1969, U.S. Pat. No. 577,291 (AUSIMONT SPA) Jul. 7, 1988, U.S. Pat. No. 5,258,110 (AUSIMONT SRL) Nov. 2, 1993 or U.S. Pat. No. 7,132,574 (SOLVAY SOLEXIS SPA) Jul. 11, 2006.

    [0100] Preferably, the PFPE-PAGs for use in the method of the invention present invention are synthesised following the process (or “method”) disclosed in international patent application WO 2014/090649 (SOLVAY SPECIALTY POLYMERS ITALY S.P.A.) Jun. 19, 2014. This method comprises the use of a boron-based catalytic species, wherein said species is prepared by first providing a mixture of a PFPE alcohol containing a catalytic amount of the corresponding alkoxide and then bringing into contact such mixture with a catalytic amount of a boric acid triester of the same PFPE alcohol.

    [0101] In greater detail and with particular reference to the preparation of PFPE-PAGs according to the invention, this process comprises the following steps:

    [0102] 1) separately providing a mixture [M1], comprising a PFPE alcohol of formula (II) as defined above and a catalytic amount of the corresponding alkoxide (herein after “PFPE-alk”);

    [0103] 2) bringing into contact mixture [M1] with a boric acid triester of the same PFPE alcohol (herein after “PFPE-triBor)” in such an amount that the molar ratio PFPE-alk:PFPE-triBor is at least 1, to obtain a mixture [M2];

    [0104] 3) contacting mixture [M2] with a catalytic amount of an iodine source to obtain a mixture [M3];

    [0105] 4) treating mixture [M3] with ethylene oxide, propylene oxide, 1,2-butykene oxide or styrene oxide or a mixture thereof to provide a mixture [M4] containing a PFPE-PAG (I).

    [0106] In step 1) of the process, mixture [M1] is typically prepared by adding a base to the PFPE alcohol of formula (II) and by allowing the base to react with the PFPE alcohol and form a catalytic amount of the corresponding PFPE-alk dissolved in the PFPE alcohol. The base can be selected from metal hydrides or hydroxides like NaOH, KOH, Ca(OH).sub.2 and Mg(OH).sub.2; according to a preferred embodiment, the base is KOH. Typically, the base is used in such an amount to obtain from 1 to 15%, preferably from 2 to 12% of PFPE-alk with respect to the PFPE alcohol. Accordingly, for the purposes of the present description, the expression “catalytic amount of PFPE-alk” is intended to mean a molar amount ranging from 1 to 15% mol, more preferably from 2 to 12% mol with respect to the PFPE alcohol. When a metal hydroxide is used as base, the reaction is typically promoted by heating and the proceeding of the reaction is checked by monitoring the amount of water evaporated off the reaction mixture. When a metal hydride is used as base, the proceeding of the reaction is checked by monitoring the amount of hydrogen evaporated off the reaction mixture.

    [0107] Step 2) can be performed in two different ways. In a first preferred embodiment, a mixture containing a PFPE-triBor and the PFPE alcohol (herein after referred to as mixture [M.sub.est]) is prepared and then brought into contact with mixture [M1]. Typically, [M.sub.est] is prepared by adding boric acid or a boric acid ester (including mono-, di- and tri-alkyl esters), and allowing the reagents to react until completion of the reaction, i.e. until obtainment of the PFPE-triBor in admixture with the PFPE alcohol. Typically, the esterification reaction is carried out under vacuum and with heating and the completion is checked by monitoring the amount of water (in case boric acid is used) or alcohol (in case an alkyl ester of boric acid is used) evaporated off the reaction mixture. In a second preferred embodiment, the PFPE-triBor is prepared in situ, i.e. by adding to [M1] a boric acid trialkyl ester as defined above; also in this case the reaction is typically carried out under vacuum and with heating and the completion of the reaction is checked in the same way. The molar ratio between the PFPE-alk and the PFPE-triBor is at least 1; according to a preferred embodiment, the PFPE-alk is used in excess with respect to PFPE-triBor, i.e. the molar ratio is higher than 1; still more preferably, the molar ratio is of at least 2. Indeed, it has been observed that when a molar ratio of at least 2 is used, the reaction proceeds faster and a higher conversion is achieved.

    [0108] Step 3) of the process is typically carried out by adding a catalytic amount of an iodine source, to reaction mixture [M2]. The iodine source can be selected from one or more alkali- or alkaline-earth metal iodides, such as NaI, Kl, CaI.sub.2, ammonium iodides, such as NH.sub.4I, elemental iodine and combinations thereof. According to a preferred embodiment, the iodine source is KI. A catalytic amount of iodine source is typically an equivalent amount ranging from 0.01 to 5% with respect to the fluoroalcohol.

    [0109] Step 4) of the process is typically carried out by adding to mixture [M3] ethylene oxide, propylene oxide, 1,2-butylene oxide, styrene oxide or a mixture thereof in such a stoichiometric amount with respect to PFPE alcohol (II) as to obtain an alkoxylation degree ranging from 4 to 50, preferably from 4 to 15, more preferably from 4 to 10.

    [0110] The alkoxylation reaction is typically carried out by adding to mixture [M3] one or more aliquots of ethylene oxide, propylene oxide or a mixture thereof and by monitoring the consumption of the oxide(s) and the formation of the PFPE-PAG. When ethylene oxide or propylene oxide is used, the reaction is monitored by checking the ethylene oxide pressure in the reactor. The reaction is typically carried out under heating at a temperature usually ranging from 90° C. to 190° C. When ethylene oxide is used as alkoxylating agent, the reaction is carried out at temperatures usually ranging from 110° to 160° C.

    [0111] Once the reaction is complete, the resulting PFPE-PAG can be isolated from mixture [M4] by conventional techniques, including extraction and distillation. Usually, mixture [M4] is cooled down to room temperature and then diluted with a fluorinated solvent, then treated with a water solution of an inorganic base, typically a carbonate, and the organic phase is separated and submitted to distillation. Examples of fluorinated solvents include, for example, Galden® PFPEs, hydrofluoroethers (HFEs) including Novec® HFEs, hydrofluorocarbons (HFCs), like Vertel® or Fluorinert®, and fluoroaromatic solvents like hexafluorobenzene and 1,3-hexafluoroxylene. Typically, the fluorinated solvent is 1,3-hexafluoroxylene.

    [0112] PFPE-PAGs according to the present invention are endowed with lubricant properties and they are advantageous in that they are stable under harsh conditions and in that they have a lower coefficient of friction, lower wear and improved performances under extreme pressure conditions with respect to PAGs. In particular, experiments carried out by the Applicant have demonstrated that PFPE-PAGs of formula (I), in particular those of formula (I-A), are endowed with lower coefficient of friction, lower wear and higher extreme pressure loads with respect to both PAGs having the same molecular weight and PAGs having the same molecular weight as chain R.sub.a in the PFPE-PAG. Experiments carried out by the Applicant further demonstrated that the PFPE-PAGs of formula (I), in particular those of formula (I-A), are endowed with higher thermal stability than PAGs having the same molecular weight.

    [0113] The PFPE-PAGs of the invention can be used as such of in admixture with further ingredients or additives typically used in the manufacture of lubricant compositions. Accordingly, the present invention further relates to a lubricant composition comprising a PFPE-PAG as defined above, in particular a PFPE-PAG of formula (I), in admixture with further lubricants and/or additives selected from those commonly used in lubricant compositions.

    [0114] In particular, compositions according to the present comprise:

    [0115] (a) a PFPE-PAG of formula (I) as defined above; in admixture of one or more of:

    [0116] (b) a lubricant base oil;

    [0117] (c) a thickening agent;

    [0118] (d) an additive; and optionally

    [0119] (e) a solvent.

    [0120] Non-limiting examples of lubricant base oils comprise PFPEs, polyalphaolefins (PAO), PAGs, mineral oils, silicon oils, polyphenyethers, etc.

    [0121] Non-limiting examples of additives comprise antirust agents, antioxidants, thermal stabilizers, pour-point depressants, antiwear agents, including those for high pressures, dispersants, tracers, dyestuffs, talc and inorganic fillers. Examples of dispersants are, for example, surfactants, preferably non-ionic surfactants, more preferably (per)fluoropolyether surfactants and (per)fluoroalkyl surfactants.

    [0122] Non-limiting examples of PFPE lubricant base oils such as those disclosed in identified as compounds (1)-(8) EP 2100909 A (SOLVAY SOLEXIS SPA) Sep. 16, 2009.

    [0123] Examples of thickening agents are talc, silica, boron nitride, polyureas, alkali or alkali-earth metals terephthalates, calcium and lithium soaps and complexes thereof and PTFE (polytetrafluoroethylene); among them, PTFE is preferred.

    [0124] Examples of solvents are fluorinated or partially fluorinated solvents, such as Galden® PFPEs, Novec® HFEs and other organic solvents like methyl-ethyl-ketone, isopropyl alcohol, butylacetate, etc.

    [0125] Compositions comprising PFPE-PAGs of formula (I) and a PFPE oil may advantageously be in the form of greases (compositions C-1), i.e. the compositions consist of a PFPE oil, a thickening agent and a PFPE-PAG of formula (I) in an amount ranging from 0.1% to 30% wt, preferably from 3% to 10% wt with respect to the weight of the composition. Experiments carried out by the Applicant have indeed demonstrated that such compositions show significantly lower wear values than greases that do not contain PFPE-PAGs. Thus, the PFPE-PAGs of the invention can act as anti-wear additives for lubricant compositions in the form of greases.

    [0126] A preferred example of lubricant base oil to be mixed with the PFPE-PAGs of the invention is represented by PAGs. In particular, experiments carried out by the Applicant showed that the PFPE-PAGs of formula (I) according to the present invention, in particular PFPE-PAGs of formula (I-A), are able to dissolve PAGs. Accordingly, the present invention further relates to a lubrication method comprising applying a PFPE-PAG of formula (I) as defined above in admixture with a PAG, and to lubricant compositions (compositions C-2) comprising, preferably consisting of, a PFPE-PAG of formula (I) as defined above in admixture with a PAG and, optionally, one or more additives. Preferred compositions C-2 comprise, preferably consist of, a PFPE-PAG of formula (I) as defined above and a PAG in a weight amount ranging from 5 to 10% with respect to the weight of the composition and, optionally, one or more additives. Accordingly, the present invention further relates to compositions C-2 consisting of:

    (a1) a PFPE-PAG of formula (I) as defined above and
    (a2) a PAG, preferably a PEG and, optionally
    (a3) one or more additives.

    [0127] Lubricant compositions C-1 and C-2 can be manufactured according to methods known in the art.

    [0128] Should the disclosure of ant patents, patent applications and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

    [0129] The invention will be disclosed in greater detail in the following Experimental section by means of non-limiting examples.

    EXPERIMENTAL SECTION

    Materials and Methods

    [0130] The PFPE-PAGs of referred to in the Examples were synthesised following the process in international patent application filed on Dec. 4, 2013 with number EP2013/075476 by Solvay Specialty Polymers Italy S.p.A.

    [0131] PEG 2000 and PEG 400 were purchased from Aldrich® and were used as such.

    [0132] Kinematic viscosities measurements were carried out according to the ASTM D445 “Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)” at different temperatures.

    [0133] The viscosity Index, VI, was calculated according to the ASTM D2270 “Standard Practice for Calculating Viscosity Index from Kinematic Viscosity at 40 and 100° C.”.

    [0134] Kinematic viscosities at different temperatures, not experimentally measured, were calculated according to the Ubbelohde-Walther equation in a temperature range from 20° to 100° C.

    [0135] Friction and wear properties were determined according to the ASTM D6425 “Standard Test Method for Measuring Friction and Wear Properties of Extreme Pressure (EP) Lubricating Oils Using SRV Test Machine” using a ball-on-disk configuration with a pre-load at 50N for 30″, a load of 300 N for 2 hours, with a frequency of 50 Hz and a stroke of 1 mm.

    [0136] The pour point of the analyzed samples was determined according to the ASTM D97 “Standard Test Method for Pour Point of Petroleum Products”.

    [0137] The wear on grease samples has been evaluated according to the ASTM D2266 “Standard Test Method for Wear Preventive Characteristics of Lubricating Grease (Four-Ball Method)”, at 75° C., with a load of 40 Kgf (1200 rpm, 1 h).

    [0138] Extreme pressure properties of lubricating oils for hydraulics, gears and engines under high-frequency linear oscillation motion were determined according to the ASTM D7421 “Standard Test Method for Determining Extreme Pressure Properties of Lubricating Oils Using High-Frequency, Linear-Oscillation (SRV) Test Machine 1”.

    [0139] All the tests performed to evaluate friction and wear properties were carried out at isoviscous conditions in order to compare the same lubricity film layer.

    Example 1

    [0140] A PFPE-PAG of formula:


    H(OCH.sub.2CH.sub.2)O.sub.rCH.sub.2CF.sub.2O(CF.sub.2CF.sub.2O).sub.m(CF.sub.2O).sub.n—CF.sub.2CH.sub.2O(CH.sub.2CH.sub.2O).sub.rH

    with r=5, p/q˜1 and an average molecular weight M.sub.n=2050
    was manufactured as indicated above. The product is a transparent liquid at room temperature and the pour point is −18° C.

    [0141] The calculated kinematic viscosity values are as follows:

    at 20° C.=395 cSt;

    at 40° C.=137 cSt and

    at 100° C.=17.5 cSt

    [0142] with a corresponding viscosity index equal to 141.

    [0143] A SRV test was carried out at 70° C., in double, with a kinematic viscosity of the product corresponding to 41 cSt. After the test the average coefficient of friction was 0.14±0.01 and the measured wear-on-the-ball was 1.0±0.1 mm.

    Example 2 (Comparative Example)

    [0144] Polyethylenglycol PEG 2000, which is a white solid at room temperature having an average molecule weight of 2000, was heated above its melting point (˜50° C.) in order to measure the kinematic viscosity. At 100° C. the kinematic viscosity was equal to 43.04 cSt.

    [0145] A SRV test was carried out at 100° C., in double, with a kinematic viscosity of the product corresponding to 43.04 cSt, under the same isoviscous conditions as Example 1. After the test, the average coefficient of friction was 0.20±0.02 and the measure wear-on-the-ball was 1.5±0.1 mm.

    Example 3 (Comparative Example)

    [0146] Polyethylenglycol PEG 400 (average molecule weight=400) was subjected to the SRV test. PEG 400 is a transparent liquid at room temperature having a kinematic viscosity at 20° C.=106.6 cSt, at 40° C.=40.2 cSt and at 100° C.=7.03 cSt with a corresponding viscosity index equal to 136.

    [0147] The SRV test was carried out at 40° C., in double, with a kinematic viscosity of the product corresponding to 40.2 cSt, under the same isoviscous conditions as in Example 1 and in comparative Example 2. After the test, the average coefficient of friction was 0.20±0.02 and the measured wear-on-the-ball was 1.4±0.06 mm.

    [0148] Examples 1, 2 and 3 above show that the PFPE-PAG is endowed with lower coefficient of friction, lower wear and good viscosity index with respect to: [0149] both a PEG having the same molecular weight as the PFPE-PAG of Example 1 (Comparative example 2) and [0150] a PEG having the same molecular weight as the PAG moieties in the PFPE-PAG of Example 1 (Comparative example 3).

    Example 4

    [0151] A PFPE-PAG of formula:


    HO(CH.sub.2(CH.sub.3)CHO).sub.s(CH.sub.2CH.sub.2O).sub.rCH.sub.2CF.sub.2O(CF.sub.2CF.sub.2O).sub.m(CF.sub.2O).sub.n—CF.sub.2CH.sub.2(OCH.sub.2CH.sub.2).sub.r(OCH(CH.sub.3)CH.sub.2).sub.sOH

    [0152] with r=2.5, s=4.5, m/n˜1 and an average molecular weight M.sub.n=2050 was manufactured as indicated above.

    [0153] The product is a transparent liquid at room temperature having a pour point of −38° C.

    [0154] The kinematic viscosity values are as follows:

    at 20° C.=274 cSt,

    at 40° C.=98 cSt

    and at 100° C.=13.7 cSt

    [0155] with a corresponding viscosity index equal to 142.

    [0156] A SRV test was carried out at 50° C., in double, with a kinematic viscosity of the product corresponding to 63 cSt. After the test the average coefficient of friction was 0.15±0.004 and the measured wear-on-the-ball was 1.1±0.1 mm.

    Example 5

    [0157] 10 g PEG 400 was added to 200 g of the PFPE-PAG of Example 4 in a glass vessel and kept under stirring at room temperature. After 15′ stirring was stopped and a transparent solution was obtained.

    Example 6

    [0158] 20 g PEG 400 was added to 200 g of the product of the Example 1 in a glass vessel and kept under stirring at room temperature. After 15′ stirring was stopped and a transparent solution was obtained.

    [0159] Examples 5-6 show that the PFPE-PAGs of the invention are able to solubilize PAGs.

    Example 7

    [0160] A thermal stability test on the PFPE-PAG of Example 1 was performed by means TGA in air (10° C./min). At 250° C. a weight loss of 6% was observed, while at 300° C. the corresponding value was 19% (see FIG. 1).

    Example 8

    [0161] A thermal stability test on the PEG of Example 2 was performed by means of TGA in air (10° C./min). At 250° C. a weight loss of 9.5% was observed, while at 300° C. the corresponding value was 34% (see FIG. 1).

    [0162] Examples 7 and Example 8 show that the PFPE-PAGs of the invention have improved thermal stability than PAGs having the same molecular weight.

    Example 9 (Comparative Example)

    [0163] A perfluorinated grease was prepared by adding a commercial PFPE, Fomblin® M30, to the powder of PTFE, in order to reach a cone penetration value of 277 mm/10′.

    [0164] This grease was subjected to the 4-ball wear test, following the procedure described above. The wear observed on the ball after the test was 1.46 mm+0.04 mm.

    Example 10

    [0165] The grease prepared in the Example 9 was added with 5% by weight of the PFPE-PAG of Example 1 and was subjected to the 4-ball wear test following the procedure described above.

    [0166] The wear observed on the ball after the test was 0.80 mm+0.05 mm.

    [0167] Example 9 and 10 show that the PFPE-PAGs of the invention are able to act as antiwear additive for perfluorinated greases.

    Example 11

    [0168] The PFPE-PAG of Example 4 was analysed under extreme pressure conditions according to ASTM D7421, under the following operative conditions: [0169] Temperature: 60° C. (kinematic viscosity of the sample oil at this temperature was 43 cSt); [0170] Stroke: 2 mm [0171] Frequency: 50 Hz [0172] Pre-load: 50 N for 30″ [0173] Load: 100 N for 15′ and increase of 100 N each 2′ up to 2000 N.

    [0174] The results showed that no seizure occurred at the final load of 2000 N.

    Example 12 (Comparative Example)

    [0175] A commercial base oil (without additives) consisting of polypropyleneglycol monobutylether, having an average molecular weight M.sub.n of 1,400 g/mol was analysed. The kinematic viscosity values were as follows:

    at 20° C.=316 cSt;

    at 40° C.=115 cSt and

    at 100° C.=20.8 cSt

    [0176] with a corresponding viscosity index equal to 207.

    [0177] A SRV test was carried out, in double, at 70° C., with a kinematic viscosity of the product corresponding to 44 cSt. After the test, the average coefficient of friction was 0.22±0.001 and the measured wear on the ball was 1.6±0.1 mm.

    [0178] The base oil was analysed under extreme pressure conditions according to the ASTM D7421, under the same operative conditions as in Example 11: The results showed that seizure occurred at a load of 1000 N.

    [0179] The comparison between Example 11 and Example 12 shows that the presence of PFPE sequences in the PFPE-GAG imparts lubrication properties to the PAG base oil, low coefficient of friction, low wear and significantly improved extreme pressure properties.