Aromatic compounds bearing hydroxyl-substituted (per)fluoropolyether chains

Abstract

Compounds [compounds (L)] comprising at least one monocyclic, polycyclic or polycondensed aromatic moiety [moiety (A*)], wherein: at least one carbon atom of moiety (A*) is substituted with a fluoropolyoxyalkene chain [chain (R.sub.f)], said chain (R.sub.f) comprising: a) a fluorocarbon segment having ether linkages in the main chain and b) at least one hydroxyl group and wherein: at least one other carbon atom of moiety (A*) is substituted with an electron-withdrawing group and mixtures thereof are herein disclosed. Disclosed are also a process for manufacturing compounds (L), a method for lubricating MRM comprising using compounds (L), a lubricant composition comprising one or more compounds (L) and a method for manufacturing a composition (C).

Claims

1. A compound (L) comprising at least one moiety (A*) wherein moiety (A*) is selected from benzene, biphenyl and naphthalene, and wherein: at least two carbon atoms of moiety (A*) are substituted with a fluoropolyoxyalkene chain (R.sub.f), each chain (R.sub.f) comprising: a) a fluorocarbon segment having ether linkages in the main chain and b) at least one hydroxyl group, each chain (R.sub.f) being bound to an sp.sup.2 carbon atom of said moiety (A*) through bridging group (B) comprising at least one heteroatom directly bound to said sp.sup.2 carbon atom, and wherein: in moiety (A*), all carbon atoms which do not bear a chain (R.sub.f) are substituted with a fluorine atom.

2. A compound (L) according to claim 1 wherein chain (R.sub.f) comprises repeating units R, said repeating units being 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 provision 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, H, (iv) CF.sub.2CF.sub.2CF.sub.2CF.sub.2O, (v) (CF.sub.2).sub.jCFZO wherein j is an integer from 0 to 3 and Z is a group of general formula OR.sub.fT.sub.3, wherein R.sub.f is a fluoropolyoxyalkene chain comprising a number of repeating units from 0 to 10, said recurring 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.sub.3 being a C.sub.1-C.sub.3 perfluoroalkyl group.

3. A compound (L) according to claim 2, wherein chain (R.sub.f) complies with formula (R.sub.f-I) here below:
(CFX.sup.1O).sub.g1(CFX.sup.2CFX.sup.3O).sub.g2(CF.sub.2CF.sub.2CF.sub.2O).sub.g3(CF.sub.2CF.sub.2CF.sub.2CF.sub.2O).sub.g4(R.sub.f-I) wherein: X.sup.1, X.sup.2, X.sup.3 equal or different from each other and at each occurrence are independently F, CF.sub.3; g1, g2, g3, and g4, equal or different from each other, are independently integers0, 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 generally statistically distributed along the chain.

4. A compound (L) according to claim 1, wherein the compound is of formula: ##STR00019## wherein A* is selected from benzene, biphenyl and naphthalene; B is a bridging group (B) selected from a C.sub.1-C.sub.20 divalent alkylene group comprising at least one sulfur or oxygen atom directly bound to an sp.sup.2 carbon atom of moiety (A*), said group being optionally fluorinated and optionally containing one or more hydroxyl groups and from a group forming with moiety (A*) a condensed ring (R) comprising aromatic moiety (A*) and a non-aromatic cyclic moiety comprising two heteroatoms, each heteroatom being directly bound to an sp.sup.2 carbon atom of moiety (A*); R.sub.f is a divalent fluoropolyoxyalkene chain (R.sub.f) wherein chain (R.sub.f) comprises repeating units R, said repeating units being chosen 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 provision 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, H, (iv) CF.sub.2CF.sub.2CF.sub.2CF.sub.2O, (v) (CF.sub.2).sub.jCFZO wherein j is an integer from 0 to 3 and Z is a group of general formula OR.sub.fT.sub.3, wherein R.sub.f is a fluoropolyoxyalkene chain comprising a number of repeating units from 0 to 10, said recurring 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.sub.3 being a C.sub.1-C.sub.3 perfluoroalkyl group; Y is a hydrocarbon group, optionally fluorinated, which comprises at least one hydroxyl group; G is a fluorine atom; x is an integer of at least 2; y is an integer of zx, wherein z is the number of carbon atoms of moiety (A*), when bridging group (B) is a divalent alkylene group as defined above or z2x, when bridging group (B) forms a condensed ring (R) as defined above, with the proviso that, when moiety (A*) is a polycyclic or polycondensed aromatic moiety, the number of bridging carbon atoms is to be detracted from z.

5. A compound (L) according to claim 4 of formula (L-1*) below: ##STR00020## wherein x is an integer of at least 2, and n is 6x.

6. A compound (L) according to claim 5 wherein x is an integer ranging from 2 to 4.

7. A compound (L) according to claim 6 which is selected from: a compound (L-1*a), wherein B is OCH.sub.2CF.sub.2O and Y is CF.sub.2CH.sub.2OH; a compound (L-1*b), wherein B is OCH.sub.2CH(OH)CH.sub.2OCH.sub.2CF.sub.2O and Y is CF.sub.2CH.sub.2OCH.sub.2CHOHCH.sub.2OH; a compound (L-1*c), wherein B is OCH.sub.2CF.sub.2O and Y is CF.sub.2CH.sub.2OCH.sub.2CHOHCH.sub.2OH; a compound (L-1*d) wherein B is OCH.sub.2CH(OH)CH.sub.2OCH.sub.2CF.sub.2O and Y is CF.sub.2CH.sub.2OH; and wherein: chain (R.sub.f) complies with formula (R.sub.f-III) below:
O(CF.sub.2CF.sub.2O).sub.a1(CF.sub.2O).sub.a2(R.sub.f-III) wherein: a1, and a2 are integers>0 such that the number average molecular weight is between 400 and 10,000, with the ratio a2/a1 being comprised between 0.1 and 10, and x ranges from 2 to 4 and n is 6x.

8. A process for the manufacture of a compound (L) according to claim 1, said process comprising the reaction of a perfluorinated monocyclic, polycyclic or polycondensed aromatic compound (A) with a (per)fluoropolyether (PFPE) polyol [PFPE (P.sub.pol)].

9. A lubricant composition for magnetic recording media (MRM), said composition comprising one or more compounds (L) as defined in claim 1 in admixture with further ingredients.

10. A method of lubricating a magnetic recording media (MRM), said method comprising using one or more compounds (L) as defined in claim 1.

11. A compound (L) according to claim 3, wherein g1+g2+g3+g4 is in the range from 2 to 100.

12. A compound (L) according to claim 7, wherein a1, and a2 are integers>0 such that the number average molecular weight is between 400 and 5,000 and wherein the ratio a2/a1 is between 0.2 and 5.

Description

EXPERIMENTAL SECTION

(1) Materials and Methods

(2) Materials

(3) The PFPE (P.sub.pol)-(IIA) used in Examples 1 and 2 complies with formula:
HOCH.sub.2CF.sub.2O(CF.sub.2CF.sub.2O).sub.a1(CF.sub.2O).sub.a2CF.sub.2CH.sub.2OH

(4) wherein EW=515, f=1.994, a1/a2=0.95, polydispersity index Mw/Mn=1.08.

(5) The PFPE (P.sub.pol)-(IIA) used in Example 3 complies with formula:
H(OCH.sub.2CH.sub.2).sub.nOCH.sub.2CF.sub.2O(CF.sub.2CF.sub.2O).sub.a1(CF.sub.2O).sub.a2CF.sub.2CH.sub.2O(CH.sub.2CH.sub.2O).sub.nH

(6) wherein EW=621, n=1.5, a1/a2=0.9, a1 and a2 are selected in such a way as to obtain Mn=1224, polydispersity index Mw/Mn=1.10.

(7) The PFPE (P.sub.pol)-(IIA) used in Example 4 complies with formula:
HOCH.sub.2CF.sub.2O(CF.sub.2CF.sub.2O).sub.a1(CF.sub.2O).sub.a2CF.sub.2CH.sub.2OH

(8) wherein EW=541, f=1.956, a1/a2=1.0, polydispersity index Mw/Mn=1.10.

(9) These PFPE (P.sub.pol) can be obtained by multiple distillation and purification of commercially available products from Solvay Specialty Polymers Italy.

(10) The mesyl derivative of Solketal was prepared following the procedure of example 1 of EP 2197939 (Step 1), which comprises the reaction of Solketal with methanesulfonylchloride.

(11) Hexafluorobenzene (HFB) was obtained from Sigma-Aldrich and was used as received.

(12) 1,3-hexafluoroxylene (HFX) was obtained from Miteni S.p.A. and was used as received.

(13) HCl, KOH, isobutanol and methanol were obtained from Sigma-Aldrich.

(14) Methods

(15) NMR Spectroscopy

(16) .sup.19F and .sup.13C NMR spectra were recorded on neat samples at 60 C. using an Agilent System 500 operating at 125.70 MHz for .sup.13C and 470.30 MHz for .sup.19F.

(17) Fractionation with Supercritical CO.sub.2 (scCO.sub.2)

(18) Fractionation with scCO.sub.2 was carried out using a 300 ml SFT-150 Supercritical CO.sub.2 Extraction System.

Example 1

(19) Step 1Reaction Between the Mesyl Derivative of Solketal and a PFPE (P.sub.pol)-(IIA)

(20) 600 g of (P.sub.pol)-(IIA) of formula HOCH.sub.2CF.sub.2O(CF.sub.2CF.sub.2O).sub.a1(CF.sub.2O).sub.a2CF.sub.2CH.sub.2OH

(21) (EW=515, f=1.994, a1/a2=0.95 1165 meq), 367 g of mesyl derivative of Solketal (1748 meq) and 600 g of HFX were charged, under nitrogen atmosphere, into a two-liter four-necked round bottom flask equipped with a mechanical stirrer, a thermometer and a refrigerant. Then, 100 g of KOH powder (85% w/w, 1518 meq) was added under stirring at room temperature and the mixture, kept under stirring, was heated with an external bath to 70 C., controlling the conversion from time to time by means of .sup.19F-NMR after cooling down to room temperature. After 7 hours the conversion was 78% and the reaction was stopped. The resulting mixture was washed twice with distilled water (500 g) and isobutanol (100 g) to obtain two phases, after phase separation, the lower organic layer was collected and the solvents were removed by distillation under reduced pressure. After a further hydroalcoholic washing with methanol (158 g) and distilled water (10 g), phase separation and solvents removal, 677 g of a mixture of PFPE polyols was obtained. This mixture can be schematically represented by the following chemical structure:
EOCH.sub.2CF.sub.2O(CF.sub.2CF.sub.2O).sub.a1(CF.sub.2O).sub.a2CF.sub.2CH.sub.2OE(M1)

(22) wherein 22% by molar basis of groups E represents hydrogen and the remaining 78% by molar basis of groups E comply with formula:

(23) ##STR00008##

(24) Step 2Reaction of the Mixture of Step 1 with Hexafluorobenzene

(25) 2.83 g HFB (C.sub.6F.sub.6, 15.2 mmol, 91.3 meq), 230 g acetonitrile (CH.sub.3CN) and 463 g mixture of step 1 (equivalent hydroxyl weight EW=2644 g/eq, 175.1 meq) were charged, under nitrogen atmosphere, into a 1-liter 4-necked round bottom flask equipped with a mechanical stirrer, a thermometer and a refrigerant. Then, 6.6 g KOH powder (85% w/w, 100.2 meq) was added under stirring at room temperature and the resulting mixture, kept under stirring, was heated with an external bath to 80 C. After 8 hours reaction, during which precipitation of KF occurred, the reaction mixture was cooled down to room temperature and further 6.6 g KOH powder (85% w/w) was added under stirring. After heating to 80 C. for further 8 hours, the reaction mixture was cooled down to room temperature and further 6.6 g KOH powder (85% w/w) was added under stirring. After heating to 80 C. for 8 hours the reaction was stopped and the resulting mixture was cooled down to room temperature.

(26) Step 3Hydrolysis and Deprotection of the Mixture Obtained in Step 2

(27) The mixture obtained at the end of step 2 was first added with 272 g distilled water and then with 212 g HCl 2% w/w water solution; formation of two phases was observed. Each time the two phases were vigorously shaken and, after separation, the lower organic layer was collected. The crude product was then added with 120 g methanol and 75 g HCl 7.5% w/w water solution, and subsequently heated to 70 C. and stirred during 3 hours, in order to completely remove the protective groups. After phase separation, the lower organic layer was collected and the solvent was removed by distillation at 80 C. under reduced pressure, to afford a crude residue (423 g) which was characterized by .sup.19F-NMR and .sup.13C-NMR. The molar composition of the residue was as follows: 36.7% para-disubstituted product having formula:

(28) ##STR00009##

(29) and 56.1% trisubstituted product of formula:

(30) ##STR00010## and 7.2% tetrasubstituted product having the following structure:

(31) ##STR00011##

(32) wherein R.sub.f=(CF.sub.2CF.sub.2O).sub.a1(CF.sub.2O).sub.a2.

(33) .sup.19F-NMR spectrum of the para-disubstituted product (neat sample) (ppm): CF.sub.2CH.sub.2OCH.sub.2CH(OH)CH.sub.2OH 78.0 and 80.0; CF.sub.2CH.sub.2OC.sub.Ar 78.9 and 80.9; C.sub.ArF 158.1.

(34) .sup.19F-NMR spectrum of the trisubstituted product (neat sample) (ppm): CF.sub.2CH.sub.2OCH.sub.2CH(OH)CH.sub.2OH 78.0 and 80.0; CF.sub.2CH.sub.2OC.sub.Ar 78.9 and 80.9; C.sub.ArF 150.6, 156.4 and 157.7.

(35) .sup.19F-NMR spectrum of the tetrasubstituted product (neat sample) (ppm): CF.sub.2CH.sub.2OCH.sub.2CH(OH)CH.sub.2OH 78.0 and 80.0; CF.sub.2CH.sub.2OC.sub.Ar 78.9 and 80.9; C.sub.ArF 150.3.

(36) Step 4Thin Layer Distillation of the Residue obtained in Step 3

(37) The residue obtained in step 3 was submitted to two passages of thin layer distillation at 200 C./2.2 Pa and 250 C./1.3 Pa, respectively in order to remove any unreacted PFPE polyols. Two fractions, corresponding to 89.3% by weight, were removed, leaving 45 g of a high boiling, low volatility residue, which was characterized by .sup.19F-NMR and .sup.13C-NMR. The molar composition of the residue was as follows: 22.9% para-disubstituted product; 63.7% trisubstituted product; and 13.4% tetrasubstituted product

(38) indicating that during vacuum distillation the para-disubstituted product percentage decreased, while the trisubstituted and tetrasubstituted products percentage increased.

(39) Step 5Fractionation of the Residue of Step 4 with Supercritical Carbon Dioxide (scCO.sub.2)

(40) The residue obtained in step 4 was charged into a 300 ml SFT-150 Supercritical CO.sub.2 Extraction System, heated at 100 C. and fractionated through a step-by-step pressure increase (from 19 to 35 MPa), operating at a CO.sub.2 flow rate of 4 NI/min. Any residual unreacted PFPE (P.sub.pol) was easily removed at scCO.sub.2 low pressure, while compounds comprising more (fluoro)benzene moieties were selectively collected at high pressure. Each fraction was characterized by .sup.19F-NMR and .sup.13C-NMR. Specifically, fractions wherein any residual unreacted PFPE (P.sub.pol) has been removed and containing only one aromatic moiety are easily identified through .sup.19 F-NMR since the ratio between the signals of CF.sub.2CH.sub.2OCH.sub.2CH(OH)CH.sub.2OH (78.0 and 80.0 ppm) and those of the CF.sub.2CH.sub.2OC.sub.Ar (78.9 and 80.9 ppm) is 1. During fractionation, the mixture composition in terms of para-disubstituted, trisubstituted and tetrasubstituted product changed according to the solubility of the different compounds in scCO.sub.2. Specifically, the para-disubstituted product percentage decreased from 61.6 to 8.5%, the trisubstituted product percentage increased from 38.4 to 77.2% while the tetrasubstituted product percentage, negligible in the first fractions, increased up to 25% in the last ones. For instance, fraction 7, corresponding to 14% w/w of the residue submitted to fractionation, has the following molar composition: 10.5% para-disubstituted product, 78.3% trisubstituted product and 11.2% tetrasubstituted product,

(41) corresponding to an average OH functionality of 6.0.

Example 2

(42) Step 1Salification of a PFPE (P.sub.pol)-(IIA)

(43) 822.3 g of PFPE (P.sub.pol)-(IIA) of formula: HOCH.sub.2CF.sub.2O(CF.sub.2CF.sub.2O).sub.a1(CF.sub.2O).sub.a2CF.sub.2CH.sub.2OH

(44) (EW=515, f=1.994, a1/a2=0.95, 1596.7 meq)

(45) is charged into a 1 l round-bottomed flask equipped with mechanical stirrer, dropping funnel, thermometer and refrigerant, then added with 23.8 g KOH (212.1 meq; 50% solution in water). The mixture is heated and maintained at 80 C. under stirring, and then vacuum is applied by means of a mechanical pump until complete elimination of water, until obtainment of a clear solution of salified (P.sub.pol)-(IIA).

(46) Step 2Reaction between Salified (P.sub.pol)-(IIA) and Hexafluorobenzene

(47) In a separate flask, 3.0 g HFB (C.sub.6F.sub.6, 16.1 mmol, 96.7 meq) is dissolved under nitrogen atmosphere in 135 g acetonitrile; the resulting solution is poured into a dropping funnel and slowly added to the solution from step 1 under stirring at 80 C. for 5 hours. After 8 hours, during which precipitation of KF occurs, the reaction is stopped and the resulting mixture is cooled down to room temperature.

(48) Step 3Hydrolysis of the Mixture obtained in Step 2

(49) The mixture obtained in step 2 is added with 214 g distilled water, 24 g HCl 37% w/w water solution and 35 g isobutyl alcohol. The two resulting phases are vigorously stirred at 50 C. for 30 minutes and, after separation, the lower organic layer is collected. The solvents are then removed by distillation at 80 C. under reduced pressure to afford 860 g crude product, containing a large amount of unreacted PFPE (P.sub.pol)-(IIA).

(50) Step 4Thin-Layer Distillation of the Crude Product of Step 3

(51) Most of the unreacted PFPE (P.sub.pol)-(IIA) is removed in two passages by thin layer distillation leaving 120 g of a high boiling, low volatility residue, which is characterized by .sup.19F-NMR and .sup.1H-NMR. Its molar composition is as follows: 29% para-disubstituted product having formula:

(52) ##STR00012## 59% trisubstituted product of formula:

(53) ##STR00013## and 12% tetrasubstituted product having the following formula:

(54) ##STR00014##

(55) wherein R.sub.f(CF.sub.2CF.sub.2O).sub.a1(CF.sub.2O).sub.a2.

(56) Step 5Fractionation of the Crude Product of Step 4 with Supercritical Carbon Dioxide (scCO.sub.2)

(57) The crude product of example 4 is charged into a 300 ml SFT-150 Supercritical CO.sub.2 Extraction System, heated at 100 C. and fractionated through a step-by-step pressure increase (from 10 to 35 MPa), operating at a CO.sub.2 flow rate of 4 NI/min. Any residual unreacted PFPE (P.sub.pol)-(IIA) is removed at scCO.sub.2 low pressure, while compounds comprising more (fluoro)benzene moieties are selectively collected at high pressure. Each fraction is characterized by .sup.19F-NMR and .sup.13C-NMR. During fractionation, the composition in terms of para-disubstituted, trisubstituted and tetrasubstituted products changes according to the solubility of the different compounds in scCO.sub.2. Specifically, the para-disubstituted product percentage decreases from 65 to a negligible amount, the trisubstituted product percentage increases from 35 to 82% while the tetrasubstituted product percentage, negligible in the first fractions, increases up to 18% in the last fraction. Therefore, the fractionation of the polyol mixture by scCO.sub.2 allows isolating fractions having different compositions in terms of di-, tri- and tetrasubstituted rings. This example demonstrates that this technique can be applied to reduce the amount of the di-substituted species and increase the average alcohol functionality of the mixture.

Example 3

(58) Step 1Salification of a PFPE (P.sub.pol)-(IIA)

(59) 925.3 g PFPE (P.sub.pol)-(IIA) of formula:
H(OCH.sub.2CH.sub.2).sub.nOCH.sub.2CF.sub.2O(CF.sub.2CF.sub.2O).sub.a1(CF.sub.2O).sub.a2CF.sub.2CH.sub.2O(CH.sub.2CH.sub.2O).sub.nH

(60) (EW=621, 1490.0 meq, n=1.5, a1/a2=0.9, a1 and a2 selected in such a way as Mn=1224)

(61) is charged into a 1 l round-bottomed flask equipped with mechanical stirrer, dropping funnel, thermometer and refrigerant, then added with 22.3 g KOH (198.7 meq; 50% solution in water). The mixture is heated and maintained at 80 C. under stirring, and then vacuum is applied by means of a mechanical pump until complete elimination of water and obtainment of a clear solution, containing PFPE (P.sub.pol)-(IIA) potassium salt.

(62) Step 2Reaction of PFPE (P.sub.pol)-(IIA) Potassium Salt with HFB

(63) In a separated flask, 2.8 g HFB (15.0 mmol, 90.3 meq) is dissolved under nitrogen atmosphere in 126 g acetonitrile; the solution is poured into the dropping funnel and slowly added to the solution from step 1 under stirring at 80 C. during 5 hours. After 8 hours of reaction, during which precipitation of KF occurs, the reaction is stopped and the mixture is cooled down to room temperature.

(64) Step 3Hydrolysis of the Mixture obtained from Step 2

(65) The mixture obtained from step 1 is added with 241 g distilled water, 27 g HCl 37% w/w water solution and 39 g isobutyl alcohol. The resulting two phases are vigorously stirred at 50 C. for 30 minutes and, after separation, the lower organic layer is collected. The solvents are then removed by distillation at 80 C. under reduced pressure to afford 968 g crude product, containing a large amount of unreacted PFPE (P.sub.pol)-(IIA).

(66) Step 4Thin-Layer Distillation of the Crude Product of Step 3

(67) Most of PFPE (P.sub.pol)-(IIA) is removed in two passages by thin-layer distillation, leaving 135 g of a high boiling, low volatility residue, which is characterized by .sup.19F-NMR and .sup.1H-NMR. Its molar composition is as follows: 30% para-disubstituted product having formula:

(68) ##STR00015## 60% trisubstituted product of formula:

(69) ##STR00016##

(70) and 10% tetrasubstituted product having the following formula:

(71) ##STR00017##

(72) wherein R.sub.f(CF.sub.2CF.sub.2O).sub.a1(CF.sub.2O).sub.a2 and n=1.5.

(73) Step 5Fractionation of the Residue from Step 4 with scCO.sub.2

(74) Mixture (M3) is charged into a 300 ml SFT-150 Supercritical CO.sub.2 Extraction System, heated at 100 C. and fractionated through a step-by-step pressure increase (from 10 to 35 MPa), operating at a CO.sub.2 flow rate of 4 NI/min. Any residual unreacted PFPE (P.sub.pol)-(IIA) is easily removed at scCO.sub.2 low pressure, while compounds comprising more (fluoro)benzene moieties are selectively collected at high pressure. Each fraction is characterized by .sup.19F-NMR and .sup.13C-NMR. During fractionation, the mixture composition in terms of para-disubstituted, trisubstituted and tetrasubstituted product changes according to the solubility of different species in scCO.sub.2. Specifically, the para-disubstituted product percentage decreases from 70 to a negligible amount, the trisubstituted product percentage increases from 30 to 85% while the tetrasubstituted product percentage, negligible in the first fractions, increases up to 15% in the last fraction. Therefore, fractionation with scCO.sub.2 allows isolating fractions having different compositions in terms of di-, tri- and tetra-substituted rings.

Example 4

(75) Step 1Reaction between the Mesyl Derivative of Solketal and a PFPE (P.sub.pol)-(IIA) to obtain a Mixture of (P.sub.pol)-(IIA)-(P.sub.pol)-(IIC)

(76) 600 g (Ppol)-(IIA) of formula HOCH.sub.2CF.sub.2O(CF.sub.2CF.sub.2O).sub.a1(CF.sub.2O).sub.a2CF.sub.2CH.sub.2OH

(77) (EW=541, f=1.956, a1/a2=1.0, 1109 meq),

(78) 100 g mesyl derivative of Solketal (476 meq) and 600 g of 1,3-hexafluoroxylene (HFX) are charged, under nitrogen atmosphere, into a 2-liter 4-necked round bottom flask equipped with a mechanical stirrer, a thermometer and a refrigerant. Then, 30 g KOH powder (85% w/w, 454 meq) is added under stirring at room temperature and the mixture, kept under stirring, is heated with an external bath to 70 C. Conversion is controlled from time to time by .sup.19F-NMR, after cooling down the withdrawn samples to room temperature. After 5 hours of reaction conversion is about 30% and the reaction is stopped. The resulting mixture is washed twice with distilled water (200 and 120 g, respectively) and, after phase separation, the lower organic layer is collected. After removal of solvents by distillation under reduced pressure, 647 g ketal-protected mixture of PFPE (P.sub.pol) (IIA)-(IIC) is obtained. The mixture can be schematically represented by the following chemical structure:
XOCH.sub.2CF.sub.2O(CF.sub.2CF.sub.2O).sub.a1(CF.sub.2O).sub.a2CF.sub.2CH.sub.2OX

(79) wherein XH (66.8% of the total end-groups on molar basis) or the following group:

(80) ##STR00018##

(81) Step 2Salification of the Mixture from Step 2

(82) 635 g ketal-protected mixture of PFPE (P.sub.pol)-(IIA)-(P.sub.pol)-(IIC) from step 1 (hydroxyl EW=843, 753.3 meq) is charged into a 1 l round-bottomed flask equipped with mechanical stirrer, dropping funnel, thermometer and refrigerant, then added with 22.4 g KOH (199.6 meq; 50% solution in water). The mixture is heated and maintained at 80 C. under stirring, and then vacuum is applied by means of a mechanical pump until complete elimination of water, thereby obtaining a clear solution.

(83) Step 3Reaction of the Salified Mixture from Step 3 with HFB

(84) In a separated flask 2.8 g HFB (15.0 mmol, 90.3 meq) is dissolved under nitrogen atmosphere in 126 g acetonitrile; the solution is poured into the dropping funnel and slowly added to the solution from step 2 under stirring at 80 C. during 5 hours. After 8 hours of reaction, during which precipitation of KF occurs, the reaction is stopped and the mixture is cooled down to room temperature.

(85) Step 4Hydrolysis of the Mixture from Step 3

(86) The mixture obtained from step 3 is added with 78 g distilled water, 200 g methanol and 37 g HCl 37% w/w water solution. The crude product is then heated at 70 C. and stirred during 3 hours, in order to completely remove the protective groups. After phase separation, the lower organic layer is collected and the solvent is removed by distillation at 80 C. under reduced pressure, to afford 603 g crude product.

(87) Step 5Thin-Layer Distillation of the Crude Product from Step 3

(88) Most of the unreacted PFPE polyols (P.sub.pol)-(IIA)-(P.sub.pol)-(IIC) are removed in two passages by thin layer distillation leaving 85 g of a high boiling, low volatility residue.

(89) Step 6Fractionation of the Residue from Step 3 with scCO.sub.2

(90) The residue obtained from step 5 is charged into a 300 ml SFT-150 Supercritical CO.sub.2 Extraction System, heated at 100 C. and purified through a step-by-step pressure increase (from 10 to 35 MPa), operating at a CO.sub.2 flow rate of 4 NI/min. Any residual unreacted PFPE polyols (P.sub.pol)-(IIA)-(P.sub.pol)-(IIC) are removed at scCO.sub.2 low pressure, while the target product is separated at higher pressure. The analysis indicates that the product is a mixture of para-disubstituted, trisubstituted and tetrasubstituted derivatives of HFB containing both CF.sub.2CH.sub.2OH and CF.sub.2CH.sub.2OCH.sub.2CH(OH)CH.sub.2OH end-groups.