Ether composition

1. An ether composition comprising at least two ether compounds (A) each of which has from 1 to 4 groups represented by the following formula (X) and from 0 to 3 groups represented by the following formula (Z), with the total of the groups represented by the formula (X) and the groups represented by the formula (Z) being 4:

HO—(CH 2 CH 2 O) a .(CH 2 CH(OH)CH 2 O) b -Q-  (X),

CF 3 (CF 2 ) s O(CF 2 CF 2 O) g —  (Z),

provided that in the above formulae (X) and (Z), a is an integer of from 0 to 100, b is 0 or 1, s is an integer of from 0 to 19, g is an integer of from 3 to 200, and Q is a polyfluorinated polymethylene group or a polyfluorinated polymethylene group having an etheric oxygen atom,

wherein the ratio (CF 3 /(OH+CF 3 )) of the total molar amount of CF 3 groups in the groups represented by the formula (Z) to the sum of the total molar amount of CF 3 groups in the groups represented by the formula (Z) and the total molar amount of OH groups in the groups represented by the formula (X) is from 0.01 to 0.5.

2. The ether composition according to claim 1 , wherein said at least two ether compounds (A) are at least two members selected from the group consisting of a compound represented by the following formula (A1), a compound represented by the following formula (A2), a compound represented by the following formula (A3) and a compound represented by the following formula (A4):

(X—) 4 Y  (A1),

(X—) 3 Y—Z  (A2),

(X—) 2 Y(—Z) 2   (A3),

X—Y(—Z) 3   (A4).

wherein X is a group represented by the above formula (X),

Y is a perfluoroalkane-tetrayl group or a group having an etheric oxygen atom inserted between carbon-carbon atoms of such a perfluoroalkane-tetrayl group and not having a structure of the group represented by the formula (Z), and

Z is a group represented by the above formula (Z).

3. The ether composition according to claim 2 , wherein X is a group selected from the group consisting of a group represented by the following formula (X1), a group represented by the following formula (X2), a group represented by the following formula (X3) and a group represented by the following formula (X4):

HOCH 2 CF 2 O(CF 2 CF 2 O) d —  (X1),

HOCH 2 CH(OH)CH 2 OCH 2 CF 2 O(CF 2 CF 2 O) d —  (X2),

HOCH 2 CH 2 CF 2 O(CF 2 CF 2 O) d —  (X3),

HOCH 2 CH 2 OCH 2 CF 2 O(CF 2 CF 2 O) d   (X4),

wherein d is an integer of from 1 to 200.

4. The ether composition according to claim 2 , wherein Y is a group having no CF 3 group.

5. The ether composition according to claim 2 , wherein Y is a group selected from the group consisting of a group represented by the following formula (Y-1), a group represented by the following formula (Y-2), a group represented by the following formula (Y-3) and a group represented by the following formula (Y-4):

6. The ether composition according to claim 2 , wherein the compound represented by the formula (A1) is a compound represented by the following formula (A1-1); the compound represented by the formula (A2) is a compound represented by the following formula (A2-1a), a compound represented by the following formula (A2-1b) or a combination of a compound represented by the following formula (A2-1a) and a compound represented by the following formula (A2-1b); the compound represented by the formula (A3) is a compound selected from the group consisting of a compound represented by the following formula (A3-1a), a compound represented by the following formula (A3-1b), a compound represented by the following formula (A3-1c) and a compound represented by the following formula (A3-1d); and the compound represented by the formula (A4) is a compound represented by the following formula (A4-1a), a compound represented by the following formula (A4-1b) or a combination of a compound represented by the following formula (A4-1a) and a compound represented by the following formula (A4-1b):

wherein X and Z in the formulae are as defined above.

7. The ether composition according to claim 1 , wherein the ether compounds (A) have no —OCF 2 O— structure.

8. The ether composition according to claim 1 , wherein the total amount of the ether compounds (A) is at least 95 mass % based on the ether composition.

9. The ether composition according to claim 1 , which has a number average molecular weight of from 500 to 1,000,000 and a molecular weight distribution of from 1.01 to 1.5.

10. A lubricant containing the ether composition as defined in claim 1 .

11. The ether composition according to claim 1 , wherein the ratio (CF 3 /(OH+CF 3 )) of the total molar amount of CF 3 groups in the groups represented by the formula (Z) to the sum of the total molar amount of CF 3 groups in the groups represented by the formula (Z) and the total molar amount of OH groups in the groups represented by the formula (X) is from 0.01 to 0.25.

12. The ether composition according to claim 1 , wherein the ratio (CF 3 /(OH+CF 3 )) of the total molar amount of CF 3 groups in the groups represented by the formula (Z) to the sum of the total molar amount of CF 3 groups in the groups represented by the formula (Z) and the total molar amount of OH groups in the groups represented by the formula (X) is from 0.01 to 0.15.

13. The ether composition according to claim 1 , wherein the ratio (CF 3 /(OH+CF 3 )) of the total molar amount of CF 3 groups in the groups represented by the formula (Z) to the sum of the total molar amount of CF 3 groups in the groups represented by the formula (Z) and the total molar amount of OH groups in the groups represented by the formula (X) is from 0.01 to 0.05.

14. The ether composition according to claim 1 , wherein the CF 3 groups are only present at a terminal of the group represented by the formula (Z).