Lubricant for magnetic recording media

A lubricant for magnetic recording media, comprising a fluorine-containing ether compound represented by formula (1), wherein a proportion of molecules represented by formula (1s) to 100% of the fluorine-containing ether compound represented by formula (1) is 90% or more in terms of a peak area ratio based on high-performance liquid chromatography:

• wherein n is any one of integers of 0 to 2;
• R3 and R3′ are each independently a perfluoropolyether chain represented by formula (1f);
• when n is 1 or 2, R3 and one or two R3′s are partially or totally the same, or are different from each other;
• R4 is a divalent linking group having 1 to 3 polar groups;
• when n is 2, two R4s are the same or different;
• R2 and R5 are divalent linking groups having one or more polar groups, and are the same or different;
• an end of R2 on a side bonded to R1 is an oxygen atom;
• an end of R5 on a side bonded to R6 is an oxygen atom;
• R1 and R6 are each a terminal group bonded to an oxygen atom at an end of R2 or R5, and are the same or different;
• and R1 and R6 are hydrogen atoms or organic groups having 1 to 50 carbon atoms,
• wherein Af1 represents a divalent perfluorohydrocarbon group having a linear or branched structure having 2 to 5 carbon atoms;
• when Af1 has a linear structure, repeating units represented by (Af1—O) are all the same;
• when Af1 has a branched structure, a structure in which an orientation direction of Af1 in the repeating unit represented by (Af1—O) is interchanged from left to right is optionally partially included;
• Af2 and Af3 each independently represent a divalent linear perfluorohydrocarbon group having 1 to 4 carbon atoms;
• and m represents an average degree of polymerization and is a real number of 1 to 13,
• wherein the same symbols as in formula (1) represent the same structures or values as in formula (1);
• and R3s and R3s′ are each independently a perfluoropolyether chain represented by formula (1f-1):
• wherein the same symbols as in formula (1f) represent the same structures as in formula (1f);
• and s represents a degree of polymerization and is any one of integers of 1 to 13.

A method for producing a lubricant for magnetic recording media, the lubricant comprising a fluorine-containing ether compound represented by formula (1), wherein a proportion of molecules with the same molecular weight contained in the fluorine-containing ether compound is 90% or more in terms of a peak area ratio based on high-performance liquid chromatography,

• the method comprising a step of synthesizing the fluorine-containing ether compound using a fluorinated polyalkylene glycol represented by formula (1f′) as a raw material;
• wherein a proportion of molecules with the same molecular weight contained in the fluorinated polyalkylene glycol is 90% or more in terms of a peak area ratio based on high-performance liquid chromatography:
• wherein n is any one of integers of 0 to 2;
• R3 and R3′ are each independently a perfluoropolyether chain represented by formula (1f);
• when n is 1 or 2, R3 and one or two R3′s are partially or totally the same, or are different from each other;
• R4 is a divalent linking group having 1 to 3 polar groups;
• when n is 2, two R4s are the same or different;
• R2 and R5 are divalent linking groups having one or more polar groups, and are the same or different;
• an end of R2 on a side bonded to R1 is an oxygen atom;
• an end of R5 on a side bonded to R6 is an oxygen atom;
• R1 and R6 are each a terminal group bonded to an oxygen atom at an end of R2 or R5, and are the same or different;
• and R1 and R6 are hydrogen atoms or organic groups having 1 to 50 carbon atoms,
• wherein Af1 represents a divalent perfluorohydrocarbon group having a linear or branched structure having 2 to 5 carbon atoms;
• when Af1 has a linear structure, repeating units represented by (Af1—O) are all the same;
• when Af1 has a branched structure, a structure in which an orientation direction of Af in the repeating unit represented by (Af1—O) is interchanged from left to right is optionally partially included;
• Af2 and Af3 each independently represent a divalent linear perfluorohydrocarbon group having 1 to 4 carbon atoms;
• and m represents an average degree of polymerization and is a real number of 1 to 13,
• wherein Af1, Af2, Af3 and m correspond to those in formula (1f);
• and in formula (1), when n is 1 or 2 and when R3 and one or two R3′s are not all the same, formula (1f′) represents a fluorine-containing polyalkylene glycol corresponding to each of R3 and R3′.

A method for producing a lubricant for magnetic recording media, the lubricant comprising a fluorine-containing ether compound represented by formula (1), wherein a proportion of molecules represented by formula (1s) to 100% of the fluorine-containing ether compound represented by formula (1) is 90% or more in terms of a peak area ratio based on high-performance liquid chromatography,

• the method comprising a step of synthesizing the fluorine-containing ether compound using a fluorinated polyalkylene glycol represented by formula (1f′) as a raw material,
• wherein a proportion of molecules represented by formula (1f′-1) to 100% of the fluorinated polyalkylene glycol represented by formula (1f′) is 90% or more in terms of a peak area ratio based on high-performance liquid chromatography:
• wherein n is any one of integers of 0 to 2;
• R3 and R3′ are each independently a perfluoropolyether chain represented by formula (1f);
• when n is 1 or 2, R3 and one or two R3′s are partially or totally the same, or are different from each other;
• R4 is a divalent linking group having 1 to 3 polar groups;
• when n is 2, two R4s are the same or different;
• R2 and R5 are divalent linking groups having one or more polar groups, and are the same or different;
• an end of R2 on a side bonded to R1 is an oxygen atom;
• an end of R5 on a side bonded to R6 is an oxygen atom;
• R1 and R6 are each a terminal group bonded to an oxygen atom at an end of R2 or R5, and are the same or different;
• and R1 and R6 are hydrogen atoms or organic groups having 1 to 50 carbon atoms,
• wherein Af1 represents a divalent perfluorohydrocarbon group having 2 to 5 carbon atoms and having a linear or branched structure;
• when Af1 has a linear structure, repeating units represented by (Af1—O) are all the same;
• when Af1 has a branched structure, a structure in which an orientation direction of Af in the repeating unit represented by (Af1—O) is interchanged from left to right is optionally partially included;
• Af2 and Af3 each independently represent a divalent linear perfluorohydrocarbon group having 1 to 4 carbon atoms;
• and m represents an average degree of polymerization and is a real number of 1 to 13,
• wherein the same symbols as in formula (1) represent the same structures or values as in formula (1);
• and R3s and R3s′ are each independently a perfluoropolyether chain represented by formula (1f-1),
• wherein the same symbols as in formula (1f) represent the same structures as in formula (1f);
• and s represents a degree of polymerization and is any one of integers of 1 to 13,
• wherein Af1, Af2, Af3 and m correspond to those in formula (1f);
• and in formula (1), when n is 1 or 2 and when R3 and one or two R3′ are not all the same, formula (1f′) represents a fluorine-containing polyalkylene glycol corresponding to each of R3 and R3′,
• wherein the same symbols as in formula (1f′) represent the same structures as in formula (1f′);
• and t represents a degree of polymerization and is any one of integers of 1 to 13.