ADDITIVE COMPOSITION FOR LUBRICANTS AND METHOD OF USE THEREOF

Abstract

The present invention relates to an additive composition comprising: (A) at least one (per)fluoropolyether polymer [PFPE polymer.sub.add] comprising a (per)fluoropolyether chain [PFPE chain.sub.add] having a first chain end and a second chain end bonded to opposite sides of said PFPE chain.sub.add, wherein: the first chain end comprises a group of formula C(O)NR.sub.aR.sub.b, wherein R.sub.a and R.sub.b, each independently, are selected from: hydrogen, linear or branched C.sub.1-C.sub.6 alkyl group; the second chain end comprises a group selected from: C.sub.1-C.sub.6 (per)fluoroalkyl group, CF.sub.2C(O)CF.sub.3 and C(OH).sub.2CF.sub.3; C(O)NR.sub.aR.sub.b, wherein R.sub.a and R.sub.b, each independently, are selected from: hydrogen, linear or branched C.sub.1-C.sub.6 alkyl group; C(O)OR.sub.c, wherein R.sub.c is a linear or branched C.sub.1-C.sub.6 alkyl group; (B) 0.01-25.0 wt. %, based on the weight of component (A), of a fluorescent dye of formula (I) (e.g. a rhodamine dye). The present invention also relates to the use of the additive composition in admixture with hydrogenated or fluorinated lubricants. The additive composition is capable of imparting the lubricant with both anti-rust and fluorescence properties.

Claims

1. An additive composition comprising: (A) at least one (per)fluoropolyether polymer, PFPE polymer.sub.add, comprising a (per)fluoropolyether chain, PFPE chain.sub.add, having a first chain end and a second chain end bonded to opposite sides of said PFPE chain.sub.add, wherein: the first chain end comprises a group of formula C(O)NR.sub.aR.sub.b, wherein R.sub.a and R.sub.b, each independently, are selected from: hydrogen, or linear or branched C.sub.1-C.sub.6 alkyl group; the second chain end comprises a group selected from: C.sub.1-C.sub.6 (per)fluoroalkyl group, CF.sub.2C(O)CF.sub.3 and C(OH).sub.2CF.sub.3; C(O)NR.sub.aR.sub.b, wherein R.sub.a and R.sub.b, each independently, are selected from: hydrogen, or linear or branched C.sub.1-C.sub.6 alkyl group; or C(O)OR.sub.c, wherein R.sub.c is a linear or branched C.sub.1-C.sub.6 alkyl group; (B) 0.01-25.0 wt. %, based on the weight of component (A), of a fluorescent dye of formula (I) ##STR00021## wherein: R1 to R4 and R7, each independently, are selected from: H, C.sub.1-C.sub.3 alkyl, CH.sub.2COOH, or C.sub.2H.sub.4OH; R5 and R6, each independently, are selected from: H or C.sub.1-C.sub.3 alkyl; X is an anion selected from: halogen, HCO.sub.2 or ClO.sub.4.

2. The additive composition of claim 1, wherein the (per)fluoropolyether chain, PFPE chain.sub.add, is a partially or fully fluorinated chain, chain (R.sub.f).sub.add, comprising repeating units R.sup., said repeating units R.sup. being independently 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 CF.sub.3; (iii) CF.sub.2CF.sub.2CW.sub.2O, wherein each of W, equal or different from each other, are F, C.sub.1, H; ##STR00022## or (v) (CF.sub.2).sub.wCFZO wherein w is an integer from 0 to 3 and Z is a group of general formula OR.sub.(f-a)Y, wherein R.sub.(f-a) 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, or CF.sub.2CF.sub.2CF.sub.2CF.sub.2O, with each of each of X being independently F or CF.sub.3 and Y being a C.sub.1-C.sub.3 perfluoroalkyl group.

3. The additive composition of claim 1, wherein the chain (R.sub.f) complies with the following formulae (R.sub.f-add-I): ##STR00023## wherein X.sup.1 is independently selected from F or CF.sub.3, X.sup.2, X.sup.3, equal or different from each other and at each occurrence, are independently F, or CF.sub.3, with the proviso that at least one of X.sup.2 and X.sup.3 is F; g1, g2, g3, and g4, equal or different from each other, are each independently 0, such that g1+g2+g3+g4 is in the range from 2 to 300; should at least two of g1, g2, g3 and g4 be different from zero, the different recurring units are statistically distributed along the chain.

4. The additive composition of claim 1, wherein the chain (R.sub.f) complies with the following formulae (R.sub.f-add-II): ##STR00024## wherein X.sup.1 is independently selected from F or CF.sub.3, X.sup.2, X.sup.3, equal or different from each other and at each occurrence, are independently F, or CF.sub.3, with the proviso that at least one of X.sup.2 and X.sup.3 is F; g1, g2, g3, g4, g5 and g6, equal or different from each other, are independently 0, such that g1+g2+g3+g4+g5+g6 is in the range from 2 to 300, with the proviso that at least one of g5 and g6 are different from 0.

5. The additive composition of claim 4, wherein in the formula (R.sub.f-add-II): g1, g5 and g6, equal or different from each other, are independently >0 and such that g1+g5+g6 is in the range from 2 to 300; the different recurring units being statistically distributed along the chain; g2, g3, g4 are equal to 0.

6. The additive composition of claim 1, wherein the PFPE polymer.sub.add is a mixture of polymer compounds comprising: (1) at least one polymer compound comprising a PFPE chain.sub.add comprising a chain (R.sub.f).sub.add complying with formula (R.sub.f-add-II) above, having a first chain end and a second chain end bonded to opposite sides of said PFPE chain.sub.add, wherein: the first chain end comprises a group of formula C(O)NR.sub.aR.sub.b where R.sub.a and R.sub.b, each independently, are selected from: hydrogen, or linear or branched C.sub.1-C.sub.6 alkyl group; the second chain end comprises a group selected from: C.sub.1-C.sub.6 perfluoroalkyl group; CF.sub.2C(O)CF.sub.3; C(OH).sub.2CF.sub.3; C(O)NR.sub.aR.sub.b, wherein R.sub.a and R.sub.b, each independently, are selected from: hydrogen, or linear or branched C.sub.1-C.sub.6 alkyl group; or C(O)OR.sub.c, wherein R.sub.c is selected from linear or branched C.sub.1-C.sub.6 alkyl group; and (2) at least one polymer compound comprising a PFPE chain.sub.add comprising a chain (R.sub.f).sub.add complying with formula (R.sub.f-add-II) above, having a first chain end and a second chain end bonded to opposite sides of said branched PFPE chain.sub.add, wherein each chain end comprises a group selected from: C.sub.1-C.sub.6 perfluoroalkyl group; CF.sub.2C(O)CF.sub.3; C(OH).sub.2CF.sub.3; C(O)NR.sub.aR.sub.b, wherein R.sub.a and R.sub.b, each independently, are selected from: hydrogen, or linear or branched C.sub.1-C.sub.6 alkyl group; or C(O)OR.sub.c, wherein R.sub.c is selected from linear or branched C.sub.1-C.sub.6 alkyl group.

7. The additive composition of claim 1, wherein the dye of formula (I) is selected from: Rhodamine B, Rhodamine 6G, Rhodamine 123, or Rhodamine 110.

8. The additive composition according to claim 1, wherein the dye of formula (I) is in an amount within the range 0.01-25.0 wt based on the weight of component (A).

9. A lubricant composition comprising a base oil and an additive composition according to claim 1, the base oil being selected from hydrogenated oil or (per)fluorinated oil.

10. The lubricant composition according to claim 9, wherein the (per)fluorinated base oil comprises at least one of: (per)fluoropolyether polymer (A-I), and (per)fluoropolyether block copolymer (A-II): (A-I) (per)fluoropolyether polymer, PFPE polymer.sub.oil, comprising a (per)fluoropolyether chain, PFPE chain.sub.oil, having two chain ends bonded to opposite sides of said PFPE chain.sub.oil, both chain ends comprising a linear or branched perfluorinated alkyl chain having from 1 to 6 carbon atoms, said PFPE polymer.sub.oil having a number average molecular weight from 500 to 100000 as measured by .sup.19F-NMR; or (A-II) at least one block copolymer, PFPE copolymer.sub.oil, comprising a first and a second (per)fluoropolyether chain, PFPE chain.sub.oil, each having two chain ends, wherein the first chain end of said first and second PFPE.sub.oil chain comprises a perfluorinated alkyl group and the second chain end of said first and second PFPE chain.sub.oil are bonded to each other via: at least one first block, block (1), complying with formula (I): ##STR00025## wherein n is 0 or an integer from 1 to 3; R.sub.1 to R.sub.4, each independently, are selected from the group consisting of fluorine atom, or perfluorinated linear or branched alkyl group having from 1 to 6 carbon atoms, group of formula (II) ##STR00026## wherein: R.sub.10 is an oxygen atom, or a bi-/tri-/tetravalent perfluorinated alkyl chain comprising from 1 to 24 carbon atoms optionally interrupted by and/or comprising at least one oxygen atom, t is zero or 1; z is an integer from 1 to 3; R.sub.11 to R.sub.15, each independently, are selected from the group consisting of, fluorine atom, or perfluorinated linear or branched alkyl group having from 1 to 6 carbon atoms and a group of formula (III): ##STR00027## wherein a{circumflex over ()} is zero or 1; V{circumflex over ()} is zero or an integer from 1 to 3; L{circumflex over ()} is zero or an integer from 1 to 250; u{circumflex over ()} is zero or an integer from 1 to 50; A{circumflex over ()} is a PFPE chain; B{circumflex over ()} is a group of formula: ##STR00028## wherein R.sub.1{circumflex over ()} to R.sub.4{circumflex over ()} each independently has the meaning defined above for each of R.sub.1 to R.sub.4, E{circumflex over ()} is a group of formula (CR.sub.100{circumflex over ()}R.sub.101{circumflex over ()}CR.sub.102{circumflex over ()}R.sub.103{circumflex over ()}) wherein R.sub.100{circumflex over ()} and R.sub.101{circumflex over ()}, each independently, are selected from: hydrogen atom; or halogen atom, and R.sub.102{circumflex over ()} and R.sub.103{circumflex over ()} are independently selected from: hydrogen atom; halogen atom; linear or branched alkyl chain comprising from 1 to 6 carbon atoms, optionally containing at least one heteroatom selected from O, N and S; OR.sub.200 wherein R.sub.200 is linear or branched perfluorinated chain comprising from 1 to 6 carbon atoms or a group of formula CF.sub.2OR.sub.201 in which R.sub.201 is a perfluorinated alkyl chain comprising from 1 to 6 carbon atoms, optionally interrupted by one or more oxygen ether atoms; or one of R.sub.100{circumflex over ()} and R.sub.101{circumflex over ()} and one of R.sub.102{circumflex over ()} and R.sub.103{circumflex over ()} are fluorine atoms and the other of R.sub.100{circumflex over ()} and R.sub.101{circumflex over ()} and the other of R.sub.102{circumflex over ()} and R.sub.103{circumflex over ()} together form a perhalogenated cyclic ring having from 4 to 6 members, optionally comprising heteroatoms, such as oxygen atoms; C{circumflex over ()} is a PFPE chain, and T is a perfluorinated alkyl group; at least one second block, block (2), complying with formula (IV): ##STR00029## wherein n* is zero or an integer from 1 to 250, L is zero or an integer from 1 to 250 and the sum of n* and L is 0 or from 1 to 250; R.sup.1* and R.sup.2* are independently selected from hydrogen atom, or halogen atom, and R.sup.3* and R.sup.4* are independently selected from hydrogen atom, halogen atom; linear or branched alkyl chain comprising from 1 to 6 carbon atoms, optionally containing at least one heteroatom selected from O, N and S; OR.sub.200 wherein R.sub.200 is linear or branched perfluorinated chain comprising from 1 to 6 carbon atoms or a group of formula CF.sub.2OR.sub.201 in which R.sub.201 is a perfluorinated alkyl chain comprising from 1 to 6 carbon atoms, optionally interrupted by one or more oxygen ether atoms; or one of R.sup.1* and R.sup.2* and one of R.sup.3* and R.sup.4* are fluorine atoms and the other of R.sup.1* and R.sup.2* and the other of R.sup.3* and R.sup.4* together form a perhalogenated cyclic ring having from 4 to 6 members, optionally comprising heteroatoms, such as oxygen atoms; E has the same meaning provided for E{circumflex over ()} above; optionally, at least a third block, block (3), comprising a PFPE chain; with the proviso that: in said PFPE copolymer: at least one of n, n* and L is different from 0; said block (1), said block (2) and, when present, said block (3) are statistically distributed; in said formula (I): at least one of R.sub.1 to R.sub.4 is a group of formula (II), one of R.sub.11 or R.sub.12 and one of R.sub.13 to R.sub.15, is a group of formula (III); in said formula (III) and said formula (IV): the recurring units are statistically distributed, in said formula (III): when a{circumflex over ()} is 1 at least one of v{circumflex over ()} and LA is different from 0.

11. The lubricant composition according to claim 9, wherein each of the PFPE chains.sub.oil in the PFPE polymer and PFPE copolymer is a partially or fully fluorinated chain, chain (R.sub.f-oil), comprising repeating units R.sup., said repeating units R.sup. being independently 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, Cl, or H; ##STR00030## (v) (CF.sub.2).sub.wCFZO wherein w is an integer from 0 to 3 and Z is a group of general formula OR.sub.(f-a)Y, wherein R.sub.(f-a) is a fluoropolyoxyalkene chain comprising a number of recurring units from 0 to 10, said recurring units being chosen among the followings: CFXO, CF.sub.2CFXO, CF.sub.2CF.sub.2CF.sub.2O, or CF.sub.2CF.sub.2CF.sub.2CF.sub.2O, with each of X being independently F or CF.sub.3 and Y being a C.sub.1-C.sub.3 perfluoroalkyl group.

12. The lubricant composition according to claim 11, wherein the PFPE chain.sub.oil is a partially or fully fluorinated chain [chain (R.sub.f)] comprising repeating units R.sup., said repeating units R.sup. being independently selected from: (i) CFXO, wherein X is F or CF.sub.3; and (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 CF.sub.3.

13. The lubricant composition according to claim 9, which is a lubricant oil or a lubricant grease.

14. A method of detecting a leak of a lubricant composition from an equipment comprising: providing an equipment containing a lubricant composition according to claim 9; irradiating an external surface of the equipment with a UV light to excite the fluorescence of the dye of formula (I) present in the lubricant composition; determining the leak of the lubricant composition on the basis of a fluorescence response from the leaked lubricant composition on said external surface.

15. A method of detecting the presence or uniform application of a lubricant coating on a substrate comprising: coating a surface of a substrate with a lubricant composition according to claim 9 to obtain a coated surface; irradiating the coated surface with a UV light to excite the fluorescence of the dye of formula (I) present in the lubricant composition; determining the presence or uniform application of the lubricant coating on the surface based on a fluorescence response from the coated surface.

16. The additive composition of claim 1, wherein the (per)fluoropolyether chain, PFPE chain.sub.add, is a partially or fully fluorinated chain, chain (R.sub.f).sub.add, consisting of repeating units R.sup., said repeating units R.sup. being independently 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 CF.sub.3; (iii) CF.sub.2CF.sub.2CW.sub.2O, wherein each of W, equal or different from each other, are F, C.sub.1, H; (iv) CF.sub.2CF.sub.2CF.sub.2CF.sub.2O; or (v) (CF.sub.2).sub.wCFZO wherein w is an integer from 0 to 3 and Z is a group of general formula OR.sub.(f-a)Y, wherein R.sub.(f-a) 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, or CF.sub.2CF.sub.2CF.sub.2CF.sub.2O, with each of each of X being independently F or CF.sub.3 and Y being a C.sub.1-C.sub.3 perfluoroalkyl group.

17. The additive composition of claim 1, wherein the dye of formula (I) is Rhodamine B.

18. The additive composition according to claim 1, wherein the dye of formula (I) is in an amount within the range 0.02-10.0 wt based on the weight of component (A).

19. The lubricant composition according to claim 9, wherein each of the PFPE chains.sub.oil in the PFPE polymer and PFPE copolymer is a partially or fully fluorinated chain, chain (R.sub.f-oil), consisting of repeating units R.sup., said repeating units R.sup. being independently 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, Cl, or H; ##STR00031## (v) (CF.sub.2).sub.wCFZO wherein w is an integer from 0 to 3 and Z is a group of general formula OR.sub.(f-a)Y, wherein R.sub.(f-a) is a fluoropolyoxyalkene chain comprising a number of recurring units from 0 to 10, said recurring units being chosen among the followings: CFXO, CF.sub.2CFXO, CF.sub.2CF.sub.2CF.sub.2O, or CF.sub.2CF.sub.2CF.sub.2CF.sub.2O, with each of X being independently F or CF.sub.3 and Y being a C.sub.1-C.sub.3 perfluoroalkyl group.

20. The lubricant composition according to claim 11, wherein the PFPE chain.sub.oil is a partially or fully fluorinated chain [chain (R.sub.f)] consisting of repeating units R.sup., said repeating units R.sup. being independently selected from: (i) CFXO, wherein X is F or CF.sub.3; and (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 CF.sub.3.

Description

DESCRIPTION OF INVENTION

[0016] According to a first aspect, the present invention relates to an additive composition comprising: [0017] (A) at least one (per)fluoropolyether polymer [PFPE polymer.sub.add] comprising a (per)fluoropolyether chain [PFPE chain.sub.add] having a first chain end and a second chain end bonded to opposite sides of said PFPE chain.sub.add, wherein: [0018] the first chain end comprises a group of formula-C(O)NR.sub.aR.sub.b, wherein R.sub.a and R.sub.b, each independently, are selected from: hydrogen, linear or branched C.sub.1-C.sub.6 alkyl group; [0019] the second chain end comprises a group selected from: C.sub.1-C.sub.6 (per)fluoroalkyl group, CF.sub.2C(O)CF.sub.3 and C(OH).sub.2CF.sub.3; C(O)NR.sub.aR.sub.b, wherein R.sub.a and R.sub.b, each independently, are selected from: hydrogen, linear or branched C.sub.1-C.sub.6 alkyl group; C(O)OR.sub.c, wherein R.sub.c is a linear or branched C.sub.1-C.sub.6 alkyl group; [0020] (B) 0.01-25.0 wt. %, based on the weight of component (A), of a fluorescent dye of formula (I)

##STR00001##

wherein: [0021] R1 to R4 and R7, each independently, are selected from: H, C.sub.1-C.sub.3 alkyl, CH.sub.2COOH, C.sub.2H.sub.4OH; [0022] R5 and R6, each independently, are selected from: H and C.sub.1-C.sub.3 alkyl; [0023] X is an anion selected from: halogen, HCO.sub.2 and ClO.sub.4.

[0024] According to a second aspect, the present invention relates to a lubricant composition comprising a base oil and an additive composition according to the first aspect, the base oil being selected from hydrogenated oil or (per)fluorinated oil.

[0025] According to a third aspect, the present invention relates to a method of detecting a leak of a lubricant composition from an equipment comprising: [0026] providing an equipment containing a lubricant composition according to the second aspect; [0027] irradiating an external surface of the equipment with a UV light capable of exciting the fluorescence of the dye of formula (I); [0028] determining the leak of the lubricant composition by observing a fluorescence emission of the fluorescent dye of formula (I) from the leaked lubricant composition on said external surface.

[0029] According to a fourth aspect, the present invention relates to a method of detecting the presence or uniform application of a lubricant coating on a substrate comprising: [0030] coating a surface of a substrate with a lubricant composition according to the second aspect to obtain a coated surface; [0031] irradiating the coated surface with a UV light to excite the fluorescence of the dye of formula (I) present in the lubricant composition; [0032] determining the presence or uniform application of the lubricant coating on the surface based on a fluorescence response from the coated surface.

[0033] As used herein: [0034] the acronym PFPE stands for (per)fluoropolyether and, when used as substantive, is intended to mean either the singular or the plural form, depending on the context; [0035] the prefix (per) in the terms (per)fluoropolyether and (per)fluorinated oil means that the polyether and the oil can be fully or partially fluorinated.

[0036] The additive composition according to the present invention comprises at least one (per)fluoropolyether polymer [PFPE polymer.sub.add] (component (A)) and a fluorescent dye of formula (I) (component (B)).

[0037] The PFPE polymer.sub.add substantially acts as fluid medium into which the fluorescent dye of formula (I) is dispersed or solubilized.

[0038] In the (per)fluoropolyether polymer [PFPE polymer.sub.add] of component (A), the first chain end preferably comprises a terminal group of formula C(O)NR.sub.aR.sub.b group where R.sub.a and R.sub.b, each independently, are selected from hydrogen and C.sub.1-C.sub.3 alkyl group (linear or branched), more preferably from hydrogen and methyl; preferably, the second chain end of the PFPE polymer.sub.add comprises a group selected from: C.sub.1-C.sub.3 perfluoroalkyl group (e.g. CF.sub.3), CF.sub.2C(O)CF.sub.3 and C(OH).sub.2CF.sub.3.

[0039] Since the PFPE polymer.sub.add does not possess acidic functional terminal groups, i.e. COOH groups, the additive composition results less aggressive and thus more compatible with a wide range of material, especially metallic surfaces.

[0040] In the PFPE polymer.sub.add, preferably, the (per)fluoropolyether chain [PFPE chain.sub.add] is a partially or fully fluorinated chain [chain (R.sub.f).sub.add] comprising, preferably consisting of, repeating units R.sup., said repeating units R.sup. being independently selected from: [0041] (i) CFXO, wherein X is F or CF.sub.3; and [0042] (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. [0043] (iii) CF.sub.2CF.sub.2CW.sub.2O, wherein each of W, equal or different from each other, are F, Cl, H;

##STR00002## [0044] (v) (CF.sub.2).sub.wCFZO wherein w is an integer from 0 to 3 and Z is a group of general formula OR.sub.(f-a)Y, wherein R.sub.(f-a) 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 Y being a C.sub.1-C.sub.3 perfluoroalkyl group.

[0045] Preferably, chain (R.sub.f).sub.add complies with the following formula:

##STR00003##

wherein [0046] X.sup.1 is independently selected from F and CF.sub.3, [0047] X.sup.2, X.sup.3, equal or different from each other and at each occurrence, are independently F, CF.sub.3, with the proviso that at least one of X.sup.2 and X.sup.3 is F; [0048] g1, g2, g3, and g4, equal or different from each other, are each independently 0, such that g1+g2+g3+g4 is in the range from 2 to 300, preferably from 10 to 250, even more preferably from 15 to 200; should at least two of g1, g2, g3 and g4 be different from zero, the different recurring units are generally statistically distributed along the chain.

[0049] More preferably, in the chain (R.sub.f-add-I), X.sup.2 and X.sup.3, equal or different from each other and at each occurrence, are independently F or CF.sub.3, with the proviso that at least one of X.sup.2 and X.sup.3 is CF.sub.3.

[0050] Even more preferably, the chain (R.sub.f).sub.add complies with the following formula:

##STR00004##

wherein [0051] X.sup.1 is independently selected from F and CF.sub.3, [0052] X.sup.2, X.sup.3, equal or different from each other and at each occurrence, are independently F or CF.sub.3, with the proviso that at least one of X.sup.2 and X.sup.3 is F; [0053] g1, g2, g3, g4, g5 and g6, equal or different from each other, are independently 0, such that g1+g2+g3+g4+g5+g6 is in the range from 2 to 300, preferably from 10 to 250, with the proviso that at least one of g5 and g6 are different from 0.

[0054] Even more preferably, in the chain (R.sub.f-add-II) above: [0055] g1, g5 and g6, equal or different from each other, are independently >0 and such that g1+g5+g6 is in the range from 2 to 300, preferably from 10 to 250; the different recurring units being statistically distributed along the chain; [0056] g2, g3 and g4 are equal to 0.

[0057] Preferably, the (per)fluoropolyether polymer [PFPE polymer.sub.add] is a mixture of polymer compounds comprising: [0058] (1) at least one polymer compound comprising a PFPE chain.sub.add, preferably comprising a chain (R.sub.f).sub.add complying with formula (R.sub.f-add-II) above, having a first chain end and a second chain end bonded to opposite sides of said PFPE chain.sub.add, wherein: [0059] the first chain end comprises a group of formula C(O)NR.sub.aR.sub.b where R.sub.a and R.sub.b, each independently, are selected from: hydrogen, linear or branched C.sub.1-C.sub.6 alkyl group; [0060] the second chain end comprises a group selected from: C.sub.1-C.sub.6 perfluoroalkyl group; CF.sub.2C(O)CF.sub.3; C(OH).sub.2CF.sub.3; C(O)NR.sub.aR.sub.b, wherein R.sub.a and R.sub.b, each independently, are selected from: hydrogen, linear or branched C.sub.1-C.sub.6 alkyl group; C(O)OR.sub.c, wherein R.sub.c is selected from linear or branched C.sub.1-C.sub.6 alkyl group; and [0061] (2) at least one polymer compound comprising a PFPE chain.sub.add, preferably comprising a chain (R.sub.f).sub.add complying with formula (R.sub.f-add-II) above, having a first chain end and a second chain end bonded to opposite sides of said branched PFPE chain.sub.add, wherein each chain end comprises a group selected from: C.sub.1-C.sub.6 perfluoroalkyl group; CF.sub.2C(O)CF.sub.3; C(OH).sub.2CF.sub.3; C(O)NR.sub.aR.sub.b, wherein R.sub.a and R.sub.b, each independently, are selected from: hydrogen, linear or branched C.sub.1-C.sub.6 alkyl group; C(O)OR.sub.c, wherein R.sub.c is selected from linear or branched C.sub.1-C.sub.6 alkyl group.

[0062] Preferably, the polymer compounds having at least one chain end comprising a C(O)NH.sub.2 group are present in the PFPE polymer.sub.add mixture in amount within the range of 1-85 wt % based on the weight of the PFPE polymer.sub.add mixture, more preferably 5-60 wt %, even more preferably 10-40 wt %.

[0063] The above-described PFPE polymers that are suitable as component A of the present invention may be prepared according to synthesis schemes well-known to the skilled person. For example, polymer compounds having terminal groups of formula C(O)NR.sub.aR.sub.b, where R.sub.a and R.sub.b have the meaning indicated above, can be prepared by reacting perfluoropolyether polymers having CFXCOOR (where e.g.: R is CH.sub.3 or C.sub.2H.sub.5; X is halogen atom, such as F and Cl, or CF.sub.3) by treatment with ammonia or an amine NR.sub.aR.sub.b, preferably in a solvent such as, for example, ethyl ether, methanol, or 1,1,2-trichlorotrifluoroethane.

[0064] The above PFPE polymers and mixtures of PFPE polymers suitable as component A of the present invention are also commercially available from Solvay Specialty Polymers Italy S.p.A.

[0065] As compound (B) the additive composition comprises a fluorescent dye, which is a xanthene dye of formula (I)

##STR00005##

wherein: [0066] R1 to R4 and R7, each independently, are selected from: H, C.sub.1-C.sub.3 alkyl, CH.sub.2COOH, C.sub.2H.sub.4OH; [0067] R5 and R6, each independently, are selected from: H and C.sub.1-C.sub.3 alkyl; [0068] X is an anion selected from: halogen, HCO.sub.2 and ClO.sub.4.

[0069] Preferably, in the above formula (I) R1 to R7, each independently, are selected from: H, methyl and ethyl.

[0070] Preferably, the fluorescent dye is selected from: Rhodamine B (CAS n. 81-88-9), Rhodamine 6G (CAS n. 989-38-8), Rhodamine 123 (CAS n. 62669-70-9) and Rhodamine 110 (CAS n. 13558-31-1). More preferably, the fluorescent dye is Rhodamine B.

[0071] The fluorescent dye of formula (I) can be present in component (B) of the additive composition either alone or as a mixture of two or more compounds of formula (I).

[0072] The fluorescent dye is a ultraviolet (UV) fluorescent compound that absorbs light in the ultraviolet or near ultraviolet region of the electromagnetic spectrum. Under illumination by a UV light that emits radiation with wavelength within the range from 10 nm to 750 nm (e.g. a Wood's lamp), the fluorescent dye produces a fluorescence emission that may be visually detected. For example, Rhodamine B (dissolved in ethanol) is characterized by an excitation peak at 510 nm and an emission peak at 565 nm.

[0073] The component (B) is present in the additive composition in amounts within the range of from 0.01 wt. % to 25.0 wt. %, the weight percentages being referred to the weight of component (A). Preferably the dye of formula (I) is in an amount within the range 0.01-25.0 wt. %, preferably 0.01 to 15.0 wt. %, even more preferably from 0.02 to 10.0 wt. % and still more preferably from 0.02 to 5.0 wt. % based on the weight of component (A).

[0074] The fluorescent dyes of formula (I) are well-known in the art. They can be prepared using known synthesis processes and are commercially available.

[0075] If required, the additive composition according to the present invention may contain one or additional components, such as for example those commonly used in lubricant compositions.

[0076] Non-limiting examples of suitable additives are the following: antioxidants, thermal stabilizers, pour-point depressants, anti-wear agents, rheological modifiers, corrosion inhibitors, pigment, dyestuffs and fillers. These additional components should be chosen so as not to interfere with the fluorescence of the additive composition or alternatively, the fluorescent dyes are chosen on the basis that there is no chemical or physical reaction between any of the components of the additive composition which might otherwise interfere with or hinder the fluorescence response of the dye under UV radiation.

[0077] The additive compositions of the invention can be prepared, for example, by mixing the compounds (A) and (B) by stirring, at room temperature, using conventional mixers, such as a Silverson-type shear mixer.

[0078] To favor the dispersion of the fluorescent dye of component (B) in the PFPE polymer of component (A), the compound (B) may be dissolved in a solvent, such as ethanol, methanol, water or other common solvents, for example in an amount of 0.5-20 wt % based on the weight of the solvent, prior to being mixed with component (A). The solvent used as solubilizing agent may then be removed, for example by stripping with inert gas under vacuum and/or thermal evaporation (e.g. at ca. 100 C.).

[0079] Any optional components may be mixed together with components (A) and (B) at the time that the additive composition is prepared, The optional components, however, may also be added subsequently to the additive composition formed by components (A) and (B). If desired, the optional components may also be added when or after that the additive composition is added to the base oil to prepare a lubricant composition.

[0080] The additive composition is preferably added to the base oil in an amount ranging from 0.05 wt. % to 30.0 wt. %, based on the weight of the base oil, more preferably from 0.1 wt. % to 15.0 wt. %, even more preferably from 1 wt. % to 10.0 wt. %. Most preferably, the additive composition contains about 0.1 wt. % of the fluorescent dye and is added to the base oil in an amount of about 5.0 wt. %.

[0081] According to a second aspect, the present invention is directed to a lubricant composition comprising a base oil and the additive composition described herein. The base oil is selected from hydrogenated oil or (per)fluorinated oil.

[0082] The base oil may be a mixture of one or more hydrogenated oils or one or more (per)fluorinated oils. When mixtures of oils are used, the oils are selected so that they are compatible with each other and for uniform mixture, stable over time.

[0083] Preferably, the hydrogenated oil is selected from mineral oils or synthetic oils, more preferably from: polyalphaolefins (PAOs), dibasic acid esters, polyol esters, phosphate esters, polyesters, alkylated naphthalenes, polyphenyl ethers, polybutenes, multiply-alkylated cyclopentanes, silane hydrocarbons, siloxanes and polyalkylene glycols. The above base oils may be used singly or in combination of two or more.

[0084] Preferably, the base oil is a (per)fluorinated base oil.

[0085] More preferably, said (per)fluorinated base oil is a (per)fluoropolyether base oil [PFPE base oil].

[0086] Preferably, said PFPE base oil is selected from the PFPE polymer.sub.oil (A-I) and [PFPE copolymer.sub.oil] (A-II) describe below: [0087] (A-I) (per)fluoropolyether polymer [PFPE polymer.sub.oil] comprising a (per)fluoropolyether chain [PFPE chain.sub.oil] having two chain ends bonded to opposite sides of said PFPE chain.sub.oil, both chain ends comprising a linear or branched perfluorinated alkyl group having from 1 to 6 carbon atoms, said PFPE polymer.sub.oil having a number average molecular weight from 500 to 100000, preferably from 2000 to 50000 as measured by .sup.19F-NMR; (A-II) at least one block copolymer [PFPE copolymer.sub.oil] comprising a first and a second (per)fluoropolyether chain [PFPE chain.sub.oil] each having two chain ends, wherein the first chain end of said first and second PFPE chain.sub.oil comprises a perfluorinated alkyl group and the second chain end of said first and second PFPE chain.sub.oil are bonded to each other via: [0088] at least one first block [block (1)] complying with formula (I):

##STR00006## [0089] wherein [0090] n is 0 or an integer from 1 to 3; [0091] R.sub.1 to R.sub.4, each independently, is selected in the group comprising, preferably consisting of, fluorine atom, perfluorinated linear or branched alkyl group having from 1 to 6 carbon atoms, group of formula (II)

##STR00007## [0092] wherein: [0093] R.sub.10 is an oxygen atom, or a bi-/tri-/tetravalent perfluorinated alkyl chain comprising from 1 to 24 carbon atoms optionally interrupted by and/or comprising at least one oxygen atom, [0094] t is zero or 1; [0095] z is an integer from 1 to 3; [0096] R.sub.11 to R.sub.15, each independently, is selected in the group comprising, preferably consisting of, fluorine atom, perfluorinated linear or branched alkyl group having from 1 to 6 carbon atoms and a group of formula (III):

##STR00008## [0097] wherein [0098] a{circumflex over ()} is zero or 1; [0099] V{circumflex over ()} is zero or an integer from 1 to 3; [0100] L{circumflex over ()} is zero or an integer from 1 to 250; [0101] u{circumflex over ()} is zero or an integer from 1 to 50; [0102] A{circumflex over ()} is a PFPE chain; [0103] B{circumflex over ()} is a group of formula:

##STR00009## [0104] wherein R.sub.1{circumflex over ()} to R.sub.4{circumflex over ()} each independently has the meaning defined above for each of R.sub.1 to R.sub.4, [0105] E{circumflex over ()} is a group of formula (CR.sub.100{circumflex over ()}R.sub.101{circumflex over ()}CR.sub.102{circumflex over ()}R.sub.103{circumflex over ()}) [0106] wherein [0107] R.sub.100{circumflex over ()} and R.sub.101{circumflex over ()}, each independently, are selected from: hydrogen atom; halogen atom, more preferably fluorine or chlorine atom, and [0108] R.sub.102{circumflex over ()} and R.sub.103{circumflex over ()} are independently selected from: hydrogen atom; halogen atom, more preferably fluorine or chlorine atom; linear or branched alkyl chain comprising from 1 to 6 carbon atoms, optionally containing at least one heteroatom selected from O, N and S; OR.sub.200 wherein R.sub.200 is linear or branched perfluorinated chain comprising from 1 to 6 carbon atoms or a group of formula CF.sub.2OR.sub.201 in which R.sub.201 is a perfluorinated alkyl chain comprising from 1 to 6 carbon atoms, optionally interrupted by one or more oxygen ether atoms; or [0109] one of R.sub.100{circumflex over ()} and R.sub.101{circumflex over ()} and one of R.sub.102{circumflex over ()} and R.sub.103{circumflex over ()} are fluorine atoms and the other of R.sub.100{circumflex over ()} and R.sub.101{circumflex over ()} and the other of R.sub.102{circumflex over ()} and R.sub.103{circumflex over ()} together form a perhalogenated cyclic ring having from 4 to 6 members, optionally comprising heteroatoms, such as oxygen atoms; [0110] C{circumflex over ()} is a PFPE chain, and [0111] T is a perfluorinated alkyl group; [0112] at least one second block [block (2)] complying with formula (IV):

##STR00010## [0113] wherein [0114] n* is zero or an integer from 1 to 250, [0115] L is zero or an integer from 1 to 250 and [0116] the sum of n* and L is 0 or from 1 to 250; [0117] R.sup.1* and R.sup.2* are independently selected from hydrogen atom, halogen atom, more preferably fluorine or chlorine atom, and [0118] R.sup.3* and R.sup.4* are independently selected from hydrogen atom, halogen atom, more preferably fluorine or chlorine atom; linear or branched alkyl chain comprising from 1 to 6 carbon atoms, optionally containing at least one heteroatom selected from O, N and S; OR.sub.200 wherein R.sub.200 is linear or branched perfluorinated chain comprising from 1 to 6 carbon atoms or a group of formula CF.sub.2OR.sub.201 in which R.sub.201 is a perfluorinated alkyl chain comprising from 1 to 6 carbon atoms, optionally interrupted by one or more oxygen ether atoms; or [0119] one of R.sup.1* and R.sup.2* and one of R.sup.3* and R.sup.4* are fluorine atoms and the other of R.sup.1* and R.sup.2* and the other of R.sup.3* and R.sup.4* together form a perhalogenated cyclic ring having from 4 to 6 members, optionally comprising heteroatoms, such as oxygen atoms; [0120] E has the same meaning provided for E{circumflex over ()} above; [0121] optionally, at least one third block [block (3)] comprising a PFPE chain; [0122] with the proviso that: [0123] in said PFPE copolymer: [0124] at least one of n, n* and L is different from 0; [0125] said block (1), said block (2) and, when present, said block (3) are statistically distributed; [0126] in said formula (I): [0127] at least one of R.sub.1 to R.sub.4 is a group of formula (II), [0128] one of R.sub.11 or R.sub.12 and one of R.sub.13 to R.sub.15, is a group of formula (III); [0129] in said formula (III) and said formula (IV): [0130] the recurring units are statistically distributed, [0131] in said formula (III): [0132] when a{circumflex over ()} is 1 at least one of v{circumflex over ()} and L{circumflex over ()} is different from 0.

[0133] Preferably, each of the PFPE chain.sub.oil mentioned above, both in the PFPE polymer.sub.oil and in the PFPE copolymer.sub.oil, is a partially or fully fluorinated chain [chain (R.sub.f-oil)] comprising, preferably consisting of, repeating units R.sup., said repeating units R.sup. being independently selected from: [0134] (i) CFXO, wherein X is F or CF.sub.3; [0135] (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; [0136] (iii) CF.sub.2CF.sub.2CW.sub.2O, wherein each of W, equal or different from each other, are F, Cl, H;

##STR00011## [0137] (v) (CF.sub.2)w-CFZO wherein w is an integer from 0 to 3 and Z is a group of general formula OR.sub.(f-a)Y, wherein R.sub.(f-a) is a fluoropolyoxyalkene chain comprising a number of recurring 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 X being independently F or CF.sub.3 and Y being a C.sub.1-C.sub.3 perfluoroalkyl group.

[0138] Preferably, the PFPE chain.sub.oil is a partially or fully fluorinated chain [chain (R.sub.f)] comprising, preferably consisting of, repeating units R.sup., said repeating units R.sup. being independently selected from: [0139] (i) CFXO, wherein X is F or CF.sub.3; and [0140] (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 CF.sub.3.

[0141] Preferably, each of the PFPE chains.sub.oil mentioned above, both in the PFPE polymer.sub.oil and in the PFPE copolymer.sub.oil, comprises a chain (R.sub.f-oil) complying with any of formulae (R.sub.f-oil-I) and (R.sub.f-oil-II) below:

##STR00012## [0142] wherein [0143] X.sup.1 is independently selected from F and CF.sub.3, [0144] X.sup.2, X.sup.3, equal or different from each other and at each occurrence, are independently F, CF.sub.3, with the proviso that at least one of X is F; [0145] g1, g2, g3, and g4, equal or different from each other, are each independently 0, such that g1+g2+g3+g4 is in the range from 2 to 300, preferably from 10 to 250, even more preferably from 15 to 200; should at least two of g1, g2, g3 and g4 be different from zero, the different recurring units are generally statistically distributed along the chain;

##STR00013## [0146] wherein [0147] X.sup.1 is independently selected from F and CF.sub.3, [0148] X.sup.2, X.sup.3, equal or different from each other and at each occurrence, are independently F, CF.sub.3, with the proviso that at least one of X is F; [0149] g1, g2, g3, g4, g5 and g6, equal or different from each other, are independently 0, such that g1+g2+g3+g4+g5+g6 is in the range from 2 to 300, preferably from 10 to 250, with the proviso that at least one of g5 and g6 are different from 0.

[0150] In a preferred embodiment, chain (R.sub.f-oil) complies with formula (R.sub.f-oil-I) above.

[0151] Preferably, the PFPE base oil is a PFPE polymer.sub.oil (A-I).

[0152] Preferably, said PFPE polymer.sub.oil (A-I) has a viscosity at 25 C. of from 10 to 3000 cSt, more preferably of from 15 to 2000 cSt and even more preferably of from 100 to 500 cSt.

[0153] Preferably, said PFPE chain.sub.oil in the PFPE base oil comprises chain R.sub.f-oil complying with formula (R.sub.f-oil-II) above.

[0154] Preferably, in said chain (R.sub.f-oil-II), X.sup.1 is F.

[0155] Preferably, in said chain (R.sub.f-oil-II), X.sup.2 and X.sup.3 are both F.

[0156] Preferably, in said chain (R.sub.f-oil-II), g1 and g2, equal or different, are both >0.

[0157] Preferably, in said chain (R.sub.f-oil-II), g3 and g4 are both 0.

[0158] Preferably, in said chain (R.sub.f-oil-II), g1+g2 is in the range from 20 to 200.

[0159] Preferably, the PFPE base oil is the PFPE copolymer.sub.oil (A-II).

[0160] Preferably, the PFPE copolymer.sub.oil (A-II) has a number average molecular weight from 500 to 100000, preferably from 2000 to 50000 as measured by .sup.19F-NMR.

[0161] It will be understood by those skilled in the art that said first chain end of said first and second PFPE chain correspond to the two chain ends of the PFPE copolymer.sub.oil.

[0162] Preferably, said first chain end of said first and second PFPE chain.sub.oil comprises a perfluorinated linear alkyl group having from 1 to 3 carbon atoms.

[0163] Preferably, said perfluorinated linear alkyl groups are the same for both said first and second chain end.

[0164] Preferably, said first chain end of said first and second PFPE chain.sub.oil and said T in formula (III), equal or different from each other, are a perfluorinated alkyl group having from 1 to 3 carbon atoms.

[0165] For example, T and T, equal to or different from each other, are a fluorine atom or a group selected from CF.sub.3, CF.sub.2CF.sub.3, CF.sub.2CF.sub.2CF.sub.3, CF(CF.sub.3).sub.2.

[0166] Other halogenated groups, such as for example CF.sub.2C.sub.1 and CF.sub.2CF.sub.2C.sub.1, can be present.

[0167] Preferably, in said first and second PFPE chain.sub.oil, A{circumflex over ()} and C{circumflex over ()} are equal or different from each other.

[0168] Preferably, in the PFPE copolymer.sub.oil, said first PFPE chain.sub.oil is bonded to said block (1) via a sigma bond or a group (C) selected from CF.sub.2, CF.sub.2CF.sub.2 or O.

[0169] Preferably, in the PFPE copolymer, said block (2) is bonded to said second PFPE chain.sub.oil via a sigma bond or a group (C) selected from CF.sub.2, CF.sub.2CF.sub.2 or O.

[0170] Preferably, when both said block (1) and said block (2) are present, they are linked via a sigma bond.

[0171] Preferably, in the PFPE copolymer.sub.oil, the sum of (n+n*+v{circumflex over ()}) is from 1 to 15, preferably from 1 to 11, more preferably from 1 to 9.

[0172] Preferably, in the PFPE copolymer.sub.oil, the sum of (L+L{circumflex over ()}) is from 1 to 500, preferably from 2 to 500, more preferably from 2 to 300.

[0173] According to a preferred embodiment, the PFPE copolymer.sub.oil comprises a first and a second PFPE chain.sub.oil, each having two chain ends, wherein the first chain end of said first and second PFPE chain.sub.oil comprises a perfluorinated alkyl group, preferably a perfluorinated linear alkyl group having from 1 to 3 carbon atoms, and the second chain end of said first and second PFPE chain are bonded to each other via: [0174] at least one block (2) complying with formula (IV):

##STR00014## [0175] wherein [0176] n* is an integer from 1 to 250, [0177] L is an integer from 1 to 250, and the sum of n* and L is from 1 to 250; [0178] R.sup.1* and R.sup.2* are fluorine atom, and [0179] R.sup.3* and R.sup.4* are independently selected from halogen atom, more preferably fluorine or chlorine atom; linear or branched alkyl chain comprising from 1 to 6 carbon atoms, optionally containing at least one heteroatom selected from O, N and S; OR.sub.200 wherein R.sub.200 is linear or branched perfluorinated chain comprising from 1 to 6 carbon atoms or a group of formula CF.sub.2OR.sub.201 in which R.sub.201 is a perfluorinated alkyl chain comprising from 1 to 6 carbon atoms, optionally interrupted by one or more oxygen ether atoms; E is a group of formula (CR100{circumflex over ()}R101{circumflex over ()}CR102{circumflex over ()}R103{circumflex over ()}) [0180] wherein [0181] R.sub.100{circumflex over ()} and R.sub.101{circumflex over ()} are independently selected from halogen atom, preferably fluorine or chlorine atom, and [0182] R.sub.102{circumflex over ()} and R.sub.103{circumflex over ()} are independently selected from halogen atom, preferably fluorine or chlorine atom; OR.sub.200 wherein R.sub.200 is linear or branched perfluorinated chain comprising from 1 to 6 carbon atoms or a group of formula CF.sub.2OR.sub.201 in which R.sub.201 is a perfluorinated alkyl chain comprising from 1 to 6 carbon atoms, optionally interrupted by one or more oxygen ether atoms; [0183] and [0184] optionally, at least one block (3) comprising a PFPE chain.

[0185] Preferably, said PFPE copolymer.sub.oil has a viscosity, measured at 25 C., that is higher than 1,000 mm.sup.2/s, more preferably higher than 2,000 mm.sup.2/s and even more preferably higher than 3,000 mm.sup.2/s.

[0186] Preferably, said PFPE copolymer.sub.oil has a viscosity, measured at 25 C., that is lower than 5,000,000 mm.sup.2/s, more preferably lower than 2,500,000 mm.sup.2/s, and even more preferably lower than 2,000,000 mm.sup.2/s.

[0187] Preferably, said PFPE copolymer.sub.oil has a viscosity, measured at 25 C., that is of from 3,000 to 1,500,000 mm.sup.2/s, more preferably of from 3,500 to 1,000,000 mm.sup.2/s and even more preferably of from 4,000 to 950,000 mm.sup.2/s.

[0188] Herein, the viscosity of the PFPE polymers and copolymers are meant to be measured at 25 C. with an Anton Paar MCR 502 parallel plate rheometer equipped with parallel plates of 25 mm, at 1 rad/s and at 25 C.

[0189] The PFPE copolymer.sub.oil can be prepared via known processes, for example as disclosed in WO 2008/065163 (SOLVAY SOLEXIS S.P.A.) or via supercritical fluid fractionation.

[0190] More preferably, the PFPE copolymer.sub.oil can be prepared via a process [process (P)], which comprises [0191] (a) contacting: [0192] at least one (per)fluoropolyether polymer comprising peroxidic groups [PFPE peroxy]; [0193] with [0194] at least one perfluorinated compound of formula (X-p):

##STR00015## [0195] wherein [0196] each of R.sub.21 to R.sub.23 and R.sub.31 to R.sub.33 is independently fluorine atom, perfluorinated alkyl group having from 1 to 3 carbon atoms, [0197] R.sub.10 is an oxygen atom, or a perfluorinated alkyl chain comprising from 2 to 18 carbon atoms, optionally and preferably interrupted by and/or comprising at least one oxygen atom, [0198] t is zero or 1, preferably 1; [0199] each of z* and z** is independently 1 or 2; [0200] and/or [0201] at least one compound [compound (O)] selected in the group comprising, preferably consisting of: [0202] (i) hydrogenated or (per)halogenated olefin comprising from 2 to 8 carbon atoms, preferably ethylene (E), propylene (PP), tetrafluoroethylene (TFE), hexafluoropropylene (HFP), chlorotrifluoroethylene (CTFE), and 1,1-difluoroethylene (VDF);

##STR00016## [0203] wherein [0204] R.sub.f is a C.sub.1-C.sub.6 (per)fluoroalkyl group, preferably CF.sub.3, C.sub.2F.sub.5, C.sub.3F.sub.7 (also referred to as PAVE hereinafter); a group C.sub.1-C.sub.12 [(per)fluoro]-oxyalkyl comprising catenary oxygen atoms, preferably perfluoro-2-propoxypropyl group (also referred to as perfluoro-oxy-alkyl-vinyl ethers hereinafter); a group CF.sub.2OR.sub.f2 (also referred to as perfluoro-methoxy-vinyl ethers or MOVE hereinafter) wherein R.sub.f2 is selected from the group consisting of C.sub.1-C.sub.6 perfluoro-alkyl; C.sub.5-C.sub.6 cyclic perfluoro-alkyl, and C.sub.2-C.sub.6 perfluoro-oxy-alkyl, comprising at least one catenary oxygen atom, preferably R.sub.f2 is CF.sub.2CF.sub.3 (MOVE1), CF.sub.2CF.sub.2OCF.sub.3 (MOVE2), or CF.sub.3 (MOVE3); [0205] (iii) perfluorodioxoles having formula:

##STR00017## [0206] wherein each of R.sub.f3, R.sub.f4, R.sub.f5, R.sub.f6, equal to or different from each other, is independently selected from the group consisting of fluorine atom and C.sub.1-C.sub.6 perfluoroalkyl groups, optionally comprising one or more than one oxygen atom, such as notably CF.sub.3, C.sub.2F.sub.5, C.sub.3F.sub.7, OCF.sub.3, OCF.sub.2CF.sub.2OCF.sub.3; in the presence of UV radiation or under heating, [0207] provided that the amount of the compound of formula (X-p) is less than 5 wt. % of the amount of the PFPE peroxy.

[0208] Optionally, a fluorination step can be performed.

[0209] The PFPE polymer.sub.oil can be prepared by means of processes that are well-known to the person skilled in the art. They are also commercially available from Solvay Specialty Polymers Italy S.p.A., for example under the trade names Fomblin Y, Fomblin M, Fomblin Z.

[0210] The lubricant composition may be in the form of a lubricant oil or a lubricant grease. When the lubricant composition is in the form of a grease, it contains at least one thickening agent (i.e. thickener).

[0211] Preferably, the thickener is in the form of powder having an average particle size (d.sub.50) within the range of 1-15 micrometer, more preferably 2-12 micrometers, and still more preferably 3-10 micrometers, as measured by laser diffraction particle size analysis as volume particle size distribution.

[0212] According to an embodiment, said thickener is selected from soap thickeners.

[0213] Soap thickeners include for example simple soaps that are organic salts of long chain organic acid with alkali metal, such as lithium, calcium, sodium, aluminum, barium, and complex soaps including simple soaps and a complexing agent. Suitable examples are lithium 12-hydroxystearate, lithium complex, calcium complex and aluminum complex.

[0214] According to an embodiment, said thickener is selected from non-soap thickeners.

[0215] Non-soap thickeners include for example polyurea, clay, fumed silica, fluorinated polymer, and/or aromatic polymer.

[0216] Preferably, said thickener is a fluorinated polymer.

[0217] According to this embodiment, said fluorinated polymer is poly(tetrafluoroethylene) (PTFE).

[0218] Preferably, said thickener is an aromatic polymer.

[0219] According to this embodiment, said aromatic polymer has a melting point of at least 150 C.

[0220] Preferably, said aromatic polymer is in the form of powder having a d.sub.50 measured by laser diffraction particle size analysis as volume particle size distribution, within the range 1-15 micrometer, and a surface area (determined by gas adsorption using the BET method according to ISO 9277) within the range of from 0.5 to less than 5 m.sup.2/g.

[0221] Said at least one aromatic polymer is advantageously selected in the group comprising, preferably consisting of: [0222] (a) poly(arylene sulphides) (PAS) polymer; [0223] (b) poly(phenylene oxides) (PPO) polymer; [0224] (c) poly(aryl ether ketone) (PAEK) polymer; and [0225] (d) poly(aryl ether sulfone) (PAES) polymer.

[0226] Preferably, said at least one aromatic polymer is a PAS polymer, such as those described in WO 2015/177857, WO2007/082829 and WO2023/078890.

[0227] Preferably, the total amount of thickening agent in the grease composition is within the range of 0.1-50.0 wt. %, more preferably 1.0-35 wt. %, based on the weight of the grease composition.

[0228] The additive compositions of the present invention are stable, i.e. they have a high shelf life, in a wide range of temperatures, for long periods, without clear separation of the components.

[0229] The additive compositions of the present invention can be used to impart a base oil with both anti-rust and fluorescence properties. The anti-rust effect can be determined by subjecting the lubricant containing the additive composition to a test according to ASTM D665 as described in the enclosed examples.

[0230] The fluorescent properties of the lubricants can be exploited to detect a leak of a lubricant from an equipment containing it, such as a hydraulic or refrigerant equipment or a container. Indeed, upon the leakage of a lubricant containing the additive composition of the present invention, the site of the leakage can be detected by irradiating the external surface of the equipment using a UV light source that emits radiations capable of exciting the fluorescence of the fluorescent dye of the additive composition. For example, a light source with a wavelength within the range from 10 nm to 750 nm, preferably from 400 nm to about 600 nm, can be used. By observing the fluorescence emission of the leaked lubricant on the external surface, the position of the leakage can be detected.

[0231] In a similar way, the fluorescent properties of a lubricant composition, especially a lubricant composition in the form of a grease, can be used to determine its presence or uniform application on a surface of a substrate, e.g. machine elements, such as bearings, pins, shafts and gears, thus allowing the end-user to verify the lubrication of the entirety of the surface or know when it is time to re-lubricate.

[0232] The present invention will be now described in more details by reference to the following examples, whose purpose is merely illustrative and do not limit the scope of the present invention.

[0233] Should the disclosure of any 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.

EXAMPLES

Determination of the Anti-Rust Properties

[0234] The anti-rust properties of the lubricant compositions have been determined following the test described in ASTM D665. The result of the test is expressed in terms of pass or fail.

Determination of the Fluorescence Properties

[0235] The fluorescence properties of the additive compositions and lubricant compositions have been evaluated visually by depositing a drop of the additive composition paper sheet followed by UV irradiation with a Wood's lamp. If the drop brightens, the additive composition is considered fluorescent.

[0236] The result of the fluorescence test is expressed in terms of YES (i.e. fluorescence observed) or NO (i.e. fluorescence not observed).

Materials Used

[0237] Rhodamine B (Sigma Aldrich); [0238] Fluorescein sodium salt (Sigma Aldrich); [0239] 2,5-bis(5-tert-butylbenzoxazol-2-yl)thiophene (BBOTSigma Aldrich); [0240] Polymer 1: mixture of PFPEs of formula

##STR00018## [0241] wherein: [0242] T is a group selected from: C(O)NH.sub.2; CF.sub.3; CF.sub.2C(O)CF.sub.3; C(OH).sub.2CF.sub.3; C(O)OCH.sub.3; T is a group selected from: C(O)NH.sub.2; F; CF.sub.3; CF.sub.2C(O)CF.sub.3; C(OH).sub.2CF.sub.3; C(O)OCH.sub.3; the ratio n/(m+r) is about 15; the number average molecular weight is about 2600; the total amount of polymer compounds having at least one of C(O)NH.sub.2 group being about 30 wt % of the weight of the PFPE mixture; [0243] Polymer 2: mixture of functional PFPEs of formula

##STR00019## [0244] wherein: [0245] T is a group selected from: CF.sub.3; CF.sub.2C(O)CF.sub.3; C(OH).sub.2CF.sub.3; C(O)OCH.sub.3; T is a group selected from: C(O)OH; F; CF.sub.3; CF.sub.2C(O)CF.sub.3; C(OH).sub.2CF.sub.3; C(O)OCH.sub.3; the ratio n/(m+r) is about 15; the number average molecular weight is about 2600; the total amount of polymer compounds having at least one C(O)OH group being about 30 wt % of the weight of the PFPE mixture; [0246] Base oil Fomblin L-VAC Y25/6 (Solvay Specialty Polymers) complying with formula:

##STR00020## [0247] wherein: m/n=40/1, the average number molecular weight (Mn) is 2400 and the kinematic viscosity at 20 C. is 250 cSt (measured according to ASTM D445).

Preparation of the Additive Compositions

[0248] An additive composition AC1 according to the present invention has been prepared by stirring with a Silverson shear mixer, at ambient temperature (ca. 25 C.), a mixture of 500 g of Polymer 1 (component (A)) and 0.5 g of Rhodamine B (CAS n. 81-88-9) as fluorescent dye (component (B)). The additive composition AC1 contains 0.1 wt. % of the fluorescent additive of component (B) based on the weight of component (A).

[0249] For comparison purposes, following the same procedure, three additive compositionsAC2* to AC5*have been prepared using Polymer 2 instead of Polymer 1 and/or a fluorescent dye selected from Fluorescein and BBOT instead of Rhodamine B.

[0250] The comparative additive composition AC5*, which substantially corresponds to the composition disclosed in US 2006/163352 A1, contains a PFPE polymer (A) having acidic chain ends and the compound BBOT (2,5-bis(5-tert-butylbenzoxazol-2-yl)thiophene) as fluorescent dye (B).

Preparation of the Lubricant Compositions

[0251] A lubricant composition according to the invention has been prepared by mixing under stirring at ambient temperature the additive composition AC1 as prepared above with the base oil at a concentration of 5 wt. % of AC1 with respect to the weight of the base oil.

[0252] For comparison purposes, following the same procedure, comparative lubricant compositions have been prepared using the additive compositions AC2*-AC5* described above instead of AC1 and the same base oil.

[0253] The composition of the materials tested and the results of their characterization are reported in Table 1.

TABLE-US-00001 TABLE 1 Fluorescence Fluorescence Anti-rust on Additive on Lubricant on Lubricant Sample Composition Composition Composition AC1 YES YES PASS (Rhodamine B + Polymer 1) AC2* NO NO FAIL (Rhodamine B + Polymer 2) AC3* NO NO PASS (BBOT + Polymer 1) AC4* NO n.d. n.d. (Fluoresceina + Polymer 1) AC5* YES YES FAIL (BBOT + Polymer 2) *Comparative examples

[0254] The results of Table 1 show that the additive composition of the invention imparts both anti-rust and fluorescence properties to the base oil. Replacing the fluorescent dye of formula (I) with a fluorescent dye of the prior art and/or the PFPE polymer results in lubricants exhibiting none or only one of the two properties.