Method of refining a lubricant for use on a magnetic recording medium

1. A method to refine a lubricant including a compound A having a perfluoropolyether molecular structure that has two hydroxyl groups at each of two ends of compound A, and a compound B having the perfluoropolyether molecular structure that has one hydroxyl group at each of two ends of compound B, the method comprising:

placing the lubricant into a pressure vessel set at a predetermined pressure and at a predetermined temperature;

removing the compound B by a process comprising:

flowing an extracting medium of a supercritical carbon dioxide fluid at a predetermined rate through the pressure vessel,

holding the pressure vessel at the predetermined temperature and the predetermined pressure,

dissolving the compound B in the supercritical carbon dioxide fluid, and

removing the dissolved compound B from the pressure vessel; and recovering the compound A by a process comprising:

flowing the extracting medium of the supercritical carbon dioxide fluid through the pressure vessel,

holding the pressure vessel at the predetermined pressure and at a temperature lower than the predetermined temperature,

dissolving the compound A in the extracting medium, and

recovering the dissolved compound A from the pressure vessel.

2. The method to refine a lubricant as recited in claim 1 , wherein the predetermined temperature is in a range from 31° C. to 100° C. and the predetermined pressure is in a range from 7.4 MPa to 30 MPa.

3. The method to refine a lubricant as recited in claim 2 , wherein the predetermined temperature is in a range from 40° C. to 100° C.

4. The method to refine a lubricant as recited in claim 1 , wherein the compound A is a lubricant A represented by formula (1) and the compound B is a lubricant B represented by formula (2);

HO—CH 2 —CH(OH)—CH 2 —O—CH 2 —CF 2 —(O—C 2 F 4 )p—(O—CF 2 )q—O—CF 2 —CH 2 —O—CH 2 —CH(OH)—CH 2 —OH  lubricant A, formula (1):

HO—CH 2 —CF 2 —(O—C 2 F 4 )p—(O—CF 2 )q—O—CF 2 —CH 2 —OH,  lubricant B, formula (2):

where p and q are positive integers.

5. A method to refine a lubricant including a compound A having a perfluoropolyether molecular structure that has two hydroxyl groups at each of two ends of compound A, and a compound B having the perfluoropolyether molecular structure that has one hydroxyl group at each of two ends of compound B, the method comprising:

placing the lubricant into a pressure vessel set at a predetermined pressure and at a predetermined temperature;

removing the compound B by a process comprising:

flowing an extracting medium of a supercritical carbon dioxide fluid at a predetermined rate through the pressure vessel,

holding the pressure vessel at the predetermined temperature and at the predetermined pressure,

dissolving the compound B in the supercritical carbon dioxide fluid, and

removing the dissolved compound B from the pressure vessel; and recovering the compound A by a process comprising:

flowing the extracting medium of the supercritical carbon dioxide fluid through the pressure vessel,

holding the pressure vessel at the predetermined temperature and at

a pressure higher than the predetermined pressure,

dissolving the compound A in the supercritical carbon dioxide fluid, and

recovering the dissolved compound A from the pressure vessel.

6. The method to refine a lubricant as recited in claim 5 , wherein the predetermined temperature is in a range from 31° C. to 100° C. and the predetermined pressure is in a range from 7.4 MPa to 30 MPa.

7. The method to refine a lubricant as recited in claim 6 , wherein the predetermined temperature is in a range from 40° C. to 100° C.

8. The method to refine a lubricant as recited in claim 5 , wherein the removing of the compound B comprises removing a component that is dissolved in the supercritical carbon dioxide fluid under a state at 60° C. and 15 Mpa.

9. The method to refine a lubricant as recited in claim 5 , wherein the recovering of the compound A comprises recovering a component that is dissolved in the supercritical carbon dioxide fluid under a state at 60° C. and 20 MPa.

10. The method to refine a lubricant as recited in claim 5 , wherein the compound A is a lubricant A represented by formula (1) and the compound B is a lubricant B represented by formula (2),

HO—CH 2 —CH(OH)—CH 2 —O—CH 2 —CF 2 —(O—C 2 F 4 )p—(O—CF 2 ) q—O—CF 2 —CH 2 —O—CH 2 —CH(OH)—CH 2 —OH  lubricant A, formula (1):

HO—CH 2 —CF 2 —(O—C 2 F 4 )p—(O—CF 2 )q—O—CF 2 —CH 2 —OH,  lubricant B, formula (2)

where p and q are positive integers.

11. The method to refine a lubricant as recited in claim 5 , wherein the lubricant is a mixture of a lubricant A having a molecular structure represented by a formula (1) and a lubricant B having a molecular structure represented by a formula (2), the mixture comprising the lubricant B in an amount from zero to 10 molar percent with respect a molar amount of the mixture of the lubricants A and B,

HO—CH 2 —CH(OH)—CH 2 —O—CH 2 —CF 2 —(O—C 2 F 4 )p—(O—CF 2 ) q—O—CF 2 —CH 2 —O—CH 2 —CH(OH)—CH 2 —OH  lubricant A, formula (1):

HO—CH 2 —CF 2 —(O—C 2 F 4 )p—(O—CF 2 )q—O—CF 2 —CH 2 —OH,  lubricant B, formula (2):

where p and q are positive integers.

12. A lubricant of a magnetic recording medium, comprising:

a compound A comprising a perfluoropolyether molecular structure having two hydroxyl groups at each of two ends of compound A; and

a compound B comprising the perfluoropolyether molecular structure having one hydroxyl group at each of two ends of compound B, wherein the lubricant is refined by

placing the lubricant into a pressure vessel set at a predetermined pressure and a predetermined temperature,

removing the compound B by a process comprising:

flowing an extracting medium of a supercritical carbon dioxide fluid at a predetermined rate through the pressure vessel,

holding the pressure vessel at the predetermined temperature and at the predetermined pressure,

dissolving the compound B in the supercritical carbon dioxide fluid, and

removing the dissolved compound B from the pressure vessel, and recovering the compound A by a process comprising:

flowing the extracting medium of the supercritical carbon dioxide fluid through the pressure vessel,

holding the pressure vessel at the predetermined pressure and at a temperature lower than the predetermined temperature,

dissolving the compound A in the supercritical carbon dioxide fluid, and

recovering the dissolved compound A from the pressure vessel.

13. The lubricant of the magnetic recording medium as recited in claim 12 , wherein the lubricant is a mixture of a lubricant A having a molecular structure represented by a formula (1) and a lubricant B having a molecular structure represented by a formula (2), the mixture comprising the lubricant B in an amount from zero to 10 molar percent with respect a molar amount of the mixture of the lubricants A and B:

HO—CH 2 —CH(OH)—CH 2 —O—CH 2 —CF 2 —(O—C 2 F 4 )p—(O—CF 2 )q—O—CF 2—CH 2 —O—CH 2 —CH(OH)—CH 2 —OH  lubricant A, formula (1)

HO—CH 2 —CF 2 —(O—C 2 F 4 )p—(O—CF 2 )q—O—CF 2 —CH 2 —OH,  lubricant B, formula (2):

where p and q are positive integers.

14. A magnetic recording medium using a lubricant, the lubricant comprising:

a compound A comprising a perfluoropolyether molecular structure having two hydroxyl groups at each of two ends of compound A; and

a compound B comprising the perfluoropolyether molecular structure having one hydroxyl group at each of two ends of compound B, wherein the lubricant is refined by

placing the lubricant into a pressure vessel set at a predetermined pressure and at a predetermined temperature,

removing the compound B by a process comprising:

flowing an extracting medium of a supercritical carbon dioxide fluid at a predetermined rate through the pressure vessel,

holding the pressure vessel at the predetermined temperature and at the predetermined pressure,

dissolving the compound B in the supercritical carbon dioxide fluid, and

removing the dissolved compound B from the pressure vessel, and recovering the compound A by a process comprising:

flowing the extracting medium of the supercritical carbon dioxide fluid through the pressure vessel,

holding the pressure vessel at the predetermined pressure and at a temperature lower than the predetermined temperature,

dissolving the compound A in the supercritical carbon dioxide fluid, and

recovering the dissolved compound A from the pressure vessel.

15. The magnetic recording medium as recited in claim 14 , wherein the lubricant is a mixture of a lubricant A having a molecular structure represented by a formula (1) and a lubricant B having a molecular structure represented by a formula (2), the mixture comprising the lubricant B in an amount from zero to 10 molar percent with respect a molar amount of the mixture of the lubricants A and B:

HO—CH 2 —CH(OH)—CH 2 —O—CH 2 —CF 2 —(O—C 2 F 4 )p—(O—CF 2 )q—O—CF 2 —CH 2 —O—CH 2 —CH(OH)—CH 2 —OH  lubricant A, formula (1):

HO—CH 2 —CF 2 —(O—C 2 F 4 )p—(O—CF 2 )q—O—CF 2 —CH 2 —OH,  lubricant B, formula (2):

where p and q are positive integers.

16. A lubricant of a magnetic recording medium, comprising:

a compound A comprising a perfluoropolyether molecular structure having two hydroxyl groups at each of two ends of compound A; and

a compound B comprising the perfluoropolyether molecular structure having one hydroxyl group at each of two ends of compound B, wherein the lubricant is refined by

placing the lubricant into a pressure vessel set at a predetermined pressure and at a predetermined temperature,

removing the compound B by a process comprising:

flowing an extracting medium of a supercritical carbon dioxide fluid at a predetermined rate through the pressure vessel,

holding the pressure vessel at the predetermined temperature and at the predetermined pressure,

dissolving the compound B in the supercritical carbon dioxide fluid, and

removing the dissolved compound B from the pressure vessel, and recovering the compound A by a process comprising:

flowing the extracting medium of the supercritical carbon dioxide fluid through the pressure vessel,

holding the pressure vessel at the predetermined temperature and at a pressure higher than the predetermined pressure

dissolving the compound A in the extracting medium, and

recovering the dissolved compound A from the pressure vessel.

17. The lubricant of the magnetic recording medium as recited in claim 16 , wherein the lubricant is a mixture of a lubricant A having a molecular structure represented by a formula (1) and a lubricant B having a molecular structure represented by a formula (2), the mixture comprising the lubricant B in an amount from zero to 10 molar percent with respect a molar amount of the mixture of the lubricants A and B:

HO—CH 2 —CH(OH)—CH 2 —O—CH 2 —CF 2 —(O—C 2 F 4 )p—(O—CF 2 )q—O—CF 2 —CH 2 —O—CH 2 —CH(OH)—CH 2 —OH  lubricant A, formula (1):

HO—CH 2 —CF 2 —(O—C 2 F 4 )p—(O—CF 2 )q—O—CF 2 —CH 2 —OH,  lubricant B, formula (2):

where p and q are positive integers.

18. The lubricant of the magnetic recording medium as recited in claim 16 , wherein the predetermined temperature is in a range from 31° C. to 100° C. and the predetermined pressure is in a range from 7.4 MPa to 30 MPa.

19. The lubricant of the magnetic recording medium as recited in claim 18 , wherein the predetermined temperature is in a range from 40° C. to 100° C.

20. A magnetic recording medium using a lubricant, the lubricant comprising:

a compound A comprising a perfluoropolyether molecular structure having two hydroxyl groups at each of two ends of compound A; and

a compound B comprising the perfluoropolyether molecular structure having one hydroxyl group at each of two ends of compound B, wherein the lubricant is refined by

placing the lubricant into a pressure vessel set at a predetermined pressure and at a predetermined temperature,

removing the compound B by a process comprising:

flowing an extracting medium of a supercritical carbon dioxide fluid at a predetermined rate through the pressure vessel,

holding the pressure vessel at the predetermined temperature and at the predetermined pressure,

dissolving the compound B in the supercritical carbon dioxide fluid, and

removing the dissolved compound B from the pressure vessel, and

recovering the compound A by a process comprising:

flowing the extracting medium of the supercritical carbon dioxide fluid through the pressure vessel,

holding the pressure vessel held at the predetermined temperature and at a pressure higher than the predetermined pressure,

dissolving the compound A in the supercritical carbon dioxide fluid, and

recovering the dissolved compound A from the pressure vessel.

21. The magnetic recording medium as recited in claim 20 , wherein the lubricant is a mixture of a lubricant A having a molecular structure represented by a formula (1) and a lubricant B having a molecular structure represented by a formula (2), the mixture comprising the lubricant B in an amount from zero to 10 molar percent with respect a molar amount of the mixture of the lubricants A and B:

HO—CH 2 —CH(OH)—CH 2 —O—CH 2 —CF 2 —(O—C 2 F 4 )p—(O—CF 2 )q—O—CF 2 —CH 2 —O—CH 2 —CH(OH)—CH 2 —OH  lubricant A, formula (1)

HO—CH 2 —CF 2 —(O—C 2 F 4 )p—(O—CF 2 )q—O—CF 2 —CH 2 —OH,  lubricant B, formula (2)

where p and q are positive integers.

22. The magnetic recording medium as recited in claim 20 , wherein the predetermined temperature is in a range from 31° C. to 100° C. and the predetermined pressure is in a range from 7.4 MPa to 30 MPa.

23. The magnetic recording medium as recited in claim 22 , wherein the predetermined temperature is in a range from 40° C. to 100° C.