US20100240560A1

US20100240560A1 - Ether composition

Info

Publication number: US20100240560A1
Application number: US12/793,757
Authority: US
Inventors: Daisuke Shirakawa; Kana Ishikawa
Original assignee: Asahi Glass Co Ltd
Current assignee: AGC Inc
Priority date: 2007-12-19
Filing date: 2010-06-04
Publication date: 2010-09-23
Also published as: JPWO2009078485A1; WO2009078485A1; JP5152199B2; TW200948894A; CN101903467B; CN101903467A; KR20100094484A

Abstract

An ether composition and a lubricant which bond to substrates with a high bonding ratio and form a coating having a low friction coefficient surface are provided.

An ether composition comprising at least two compounds selected from (X—)₃Y³, (X—)₂Y³—Z and X—Y³(—Z)₂wherein the total number of moles of CF₃groups in Z in relation to the sum of the total number of moles of CF₃groups in Z and the total number of moles of OH groups in X is at least 0.001 and at most 0.30. X is HO—(CH₂CH₂O)_a.(CH₂CH(OH)CH₂O)_b-Q-, Y³is a perfluoroalkane-triyl group, and Z is CF₃(CF₂)_sO(CF₂CF₂O)_g—, wherein 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 bonded between carbon-carbon atoms and/or an etheric oxygen atom bonded to the terminal carbon atom bonded to Y³.

Description

TECHNICAL FIELD

The present invention relates to an ether composition useful as a lubricant, etc.

BACKGROUND ART

A perfluorinated polyether compound (hereinafter referred to as PFPE) is used as a lubricant, etc. to be applied to the surface of a magnetic recording medium (Non-Patent Document 1).
As such a lubricant, PFPE having two CH₂OH groups at its molecular terminals has been commonly used.
Further, the present applicant has proposed the following as PFPE or its composition, which is useful as a lubricant, etc.
(1) PFPE having three CH₂OH groups, or PFPE having two CH₂OH groups and one CF₃group (Patent Document 1).
(2) An ether composition comprising two types of PFPEs different in the molecular weight (Patent Document 2).
In recent years, along with an increase in the recording density of a magnetic recording medium, narrowing of a space between a recording element and a magnetic recording medium and a trend for high speed of rotation of a magnetic recording medium have been advanced. Accordingly, the application environment of a lubricant to be applied on the surface of a magnetic recording medium has been increasingly severe. Therefore, the lubricant is required to have the following properties.
(i) It has a high fixative to a magnetic recording medium, along with the trend for high speed of the magnetic recording medium.
(ii) It forms a coating having a low friction coefficient surface so that when a recording head contacts magnetic recording media, the impact by the contact is dissipated.
However, PFPE heretofore proposed did not provide sufficient performance to meet such requirements.

Non-Patent Document 1: “Monthly TRIBOLOGY”, 1995, vol. 99, November issue, p. 37-38
Patent Document 1: WO2005/068534
Patent Document 2: WO2007/013412

DISCLOSURE OF THE INVENTION

Object to be Accomplished by the Invention

The object of the present invention is to provide an ether composition which bonds to substrates with a high bonding ratio and forms a coating having a low friction coefficient surface and a lubricant containing the ether composition.

Means to Accomplish the Object

The ether composition of the present invention is an ether composition comprising at least two compounds selected from the group consisting of a compound represented by the following formula (A1), a compound represented by the following formula (A2) and a compound represented by the following formula (A3), wherein the total number of moles of CF₃groups in the group represented by the following formula (Z) in relation to the sum of the total number of moles of CF₃groups in the group represented by the following formula (Z) and the total number of moles of OH groups in the group represented by the following formula (X) (CF₃/(OH+CF₃)) is at least 0.001 and at most 0.30:
(X—)₃Y³ (A1),
(X—)₂Y³—Z (A2),
X—Y³(—Z)₂ (A3).
Wherein X is a group represented by the following formula (X),
Y³is a perfluoroalkane-triyl group or a perfluoroalkane-triyl group having an etheric oxygen atom inserted between carbon-carbon atoms, provided that when Y³has a CF₃group, the CF₃group is bonded to a quaternary carbon,
Z is a group represented by the following formula (Z):
HO—(CH₂CH₂O)_a.(CH₂CH(OH)CH₂O)_b-Q- (X),
CF₃(CF₂)_sO(CF₂CF₂O)_g— (Z).
Wherein 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, a polyfluorinated polymethylene group having an etheric oxygen atom bonded between carbon-carbon atoms, a polyfluorinated polymethylene group having an etheric oxygen atom bonded to the terminal carbon atom bonded to Y³or a polyfluorinated polymethylene group having an etheric oxygen atom bonded between carbon-carbon atoms and an etheric oxygen atom bonded to the terminal carbon atom bonded to Y³.
It is preferred that the group (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):
HOCH₂CF₂O(CF₂CF₂O)_d— (X1),
HOCH₂CH(OH)CH₂OCH₂CF₂O(CF₂CF₂O)_d— (X2),
HOCH₂CH₂CF₂O(CF₂CF₂O)_d— (X3),
HOCH₂CH₂OCH₂CF₂O(CF₂CF₂O)_d— (X4),
wherein d is an integer of from 1 to 200.
It is preferred that Y³is a group selected from the group consisting of a group represented by the following formula (Y³-1), a group represented by the following formula (Y³-2) and a group represented by the following formula (Y³-3).
It is preferred that the compound represented by the formula (A1) is a compound represented by the following formula (A1-1), that 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), and that the compound represented by the formula (A3) is a compound represented by the following formula (A3-1a), a compound represented by the following formula (A3-1b) or a combination of a compound represented by the following formula (A3-1a) and a compound represented by the following formula (A3-1b).
It is preferred that the compound represented by the formula (A1), the compound represented by the formula (A2) and the compound represented by the formula (A3) have no —OCF₂O— structure.
It is preferred that the he total amount of the compound represented by the formula (A1), the compound represented by the formula (A2) and the compound represented by the formula (A3) is at least 95 mass % in relation to the ether composition.
It is preferred that the ether composition has a number average molecular weight of from 500 to 1,000,000 and a molecular weight distribution (mass average molecular weight/number average molecular weight) of from 1.01 to 1.5.
The ether composition is preferably used to form a lubricant containing the ether composition.

EFFECTS OF THE INVENTION

The ether composition of the present invention bonds firmly to substrates, forms a coating having a surface with a low coefficient of friction and is useful as a lubricant to be applied on the surface of magnetic recording media.

BEST MODE FOR CARRYING OUT THE INVENTION

In this specification, a compound represented by the formula (A1) is referred to as the compound (A1). Compounds represented by the other formulae are referred to in the same manner.
Further, a group represented by the formula (X) is referred to as the group (X). Groups represented by the other formulae are referred to in the same manner.
The ether composition of the present invention is an ether composition comprising at least two compounds selected from the compound (A1), the compound (A2) and the compound (A3), and preferably comprises the compound (A1) and the compound (A2), or the compounds (A1) to (A3). Each of the compounds (A1) to (A3) in the ether composition may consist of one or at least two compounds and preferably consists of one compound.
(X—)₃Y³ (A1),
(X—)₂Y³—Z (A2),
X—Y³(—Z)₂ (A3).
X is a group (X).
HO—(CH₂CH₂O)_a.(CH₂CH(OH)CH₂O)_b-Q- (X).
The notation of the structure —(CH₂CH₂O)_a.(CH₂CH(OH)CH₂O)_b— means that when at least one unit is present with respect to each of the (CH₂CH₂O) unit and the (CH₂CH(OH)CH₂O) unit, their arrangement is not particularly limited. Namely, in a case where one unit is present with respect to both units, the unit which is bonded to the terminal hydroxyl group may be either of them. Further, the structure —(CH₂CH₂O)_a.(CH₂CH(OH)CH₂O)_b— may be a block copolymer or a random copolymer.
Q is a polyfluorinated polymethylene group, a polyfluorinated polymethylene group having an etheric oxygen atom bonded between carbon-carbon atoms, a polyfluorinated polymethylene group having an etheric oxygen atom bonded to the terminal carbon atom bonded to Y³or a polyfluorinated polymethylene group having an etheric oxygen atom bonded between carbon-carbon atoms and an etheric oxygen atom bonded to the terminal carbon atom bonded to Y³. The polyfluorinated polymethylene group means a group having at least two hydrogen atoms in —(CH₂)_t— (wherein t is an integer of at least 2) substituted by fluorine atoms. Q is preferably a group represented by the formula —(CH₂)_c—CF₂O(CF₂CF₂O)_d— (wherein the right hand side terminal of the group is bonded to Y³, c is an integer of from 1 to 100, and d is an integer of from 1 to 200).
a is an integer of from 0 to 100, preferably an integer of from 0 to 10, more preferably an integer of from 0 to 2, particularly preferably 0 or 1. When b is 1, a is preferably 0.
b is preferably 0 or 1.
The group (X) is preferably a group (X′).
HO—(CH₂CH₂O)_a.(CH₂CH(OH)CH₂O)_b—(CH₂)_c—CF₂O(CF₂CF₂O)_d— (X′),
wherein a to d are the same as defined above.
c is preferably an integer of from 1 to 10, more preferably 1 or 2.
d is preferably an integer of from 3 to 100, more preferably from an integer of from 5 to 50.
When two or more groups (X) are present in one molecule, they may be the same or different. Groups (X) having different numbers of structural units may be categorized as the same. For example, the same groups may have the same d or may be different only in d. With respect to the numbers other than d, groups (X′) which are different in a, b or c are considered as different groups. When two or more groups (X) are in the same molecule, it is preferred that they are the same groups.
The group (X) is preferably a group (X1), a group (X2), a group (X3) or a group (X4), and a group (X1) or a group (X2) is more preferred in view of easy production and stability of the compounds (A1) to (A3).
HOCH₂CF₂O(CF₂CF₂O)_d— (X1),
HOCH₂CH(OH)CH₂OCH₂CF₂O(CF₂CF₂O)_d— (X2),
HOCH₂CH₂CF₂O(CF₂CF₂O)_d— (X3),
HOCH₂CH₂OCH₂CF₂O(CF₂CF₂O)_d— (X4).
Y³is a perfluoroalkane-triyl group or a perfluoroalkane-triyl group having an etheric oxygen atom inserted between carbon-carbon atoms, and when Y³has a CF₃group, the CF₃group is bonded only to a quaternary carbon.
A perfluoroalkane-triyl group means a trivalent saturated hydrocarbon group having all hydrogen atoms substituted by fluorine atoms, and a quaternary carbon atom which is not bonded to a fluorine atom may be bonded to a CF₃group.
Y³is restricted to a group having no CF₃groups or having only a CF₃group bonded to a quaternary carbon atom for the following reason.
The present inventors studied the effect of the structure of PFPEs on their low friction coefficient and firm bonding, which are incompatible with each other, and found that a CF₃group bonded to a secondary carbon atom (CF₂) or a tertiary carbon atom (CF) has a high degree of freedom in the molecule and hence contributes to decrease in friction coefficient (decrease in viscosity), while inhibiting firm bonding. Therefore, the present inventors decided that the proportion of CF₃groups in an ether composition should be controlled to attain both a low friction coefficient and firm bonding and that PFPE should have a CF₃group which is present only at the terminal of Z and may have another CF₃group attached to a quaternary carbon atom with a relatively low degree of freedom in Y³.
Y³may be a group having an etheric oxygen atom inserted between carbon-carbon atoms. The number of etheric oxygen atoms, if present, is preferably 1 to 3. Because an etheric oxygen atom is present between carbon-carbon atoms, no etheric oxygen atom can be present at the terminal of Y³bonded to X or Z. When Y³contains an etheric oxygen atom, it is preferred that Y³contains no —OCF₂O— structure and has no —OCF₂— structure at the terminal bonded to X or Z. Compounds having neither structure have a remarkably improved chemical stability.
Y³is preferably a group having no etheric oxygen atom, particularly preferably a group (Y³-1), a group (Y³-2) or a group (Y³-3).
Z is a group (Z).
CF₃(CF₂)_sO(CF₂CF₂O)_g— (Z).
s is an integer of from 0 to 19, preferably an integer of from 0 to 15, particularly preferably an integer of from 0 to 5.
g is an integer of from 3 to 200, preferably an integer of from 3 to 100, more preferably an integer of from 3 to 70, particularly preferably an integer of from 5 to 50.
Groups (Z) in which s is the same are considered to be the same, irrespective of whether g is the same or different. The groups (Z) are preferably the same.
The group (Z) contributes to decrease in friction coefficient and is preferred to have a certain length in view of increasing the freedom of the CF₃group in the molecule. The group (Z) is preferably a group (Z1), a group (Z2) or a group (Z3).
CF₃O(CF₂CF₂O)_g— (Z1),
CF₃(CF₂)₂O(CF₂CF₂O)_g— (Z2),
CF₃(CF₂)₅O(CF₂CF₂O)_g— (Z3).
Each of the compounds (A1) to (A3) may be a combination of two or more compounds which preferably have the same Y³but differ in a, b, c or d in the group (X). In the group (X), the average of a is preferably a positive number of from 0 to 2, particularly preferably 0. In the group (X′), the average of c is preferably 1, and the average of d is preferably a positive number of from 3 to 100. In the group (Z), the average of g is preferably a positive number of from 3 to 100.
It is preferred that the compounds (A1) to (A3) have no —OCF₂O— structure in view of chemical stability. A compound having no —OCF₂O— structure means a compound in which the presence of the structure cannot be detected by a conventional analytical means (such as ¹⁹F-NMR).
As the compound (A1), a compound (A11) or a compound (A12) is preferred.
{HOCH₂CF₂O(CF₂CF₂O)_d—}₃Y³ (A11),
{HOCH₂CH(OH)CH₂OCH₂CF₂O(CF₂CF₂O)_d—}₃Y³ (A12).
As the compound (A2), a compound (A21) or a compound (A22) is preferred.
{HOCH₂CF₂O(CF₂CF₂O)_d—}₂Y³—(OCF₂CF₂)_gO(CF₂)_SCF₃ (A21),
{HOCH₂CH(OH)CH₂OCH₂CF₂O(CF₂CF₂O)_d—}₂Y³—(OCF₂CF₂)_gO(CF₂)_sCF₃ (A22).
As the compound (A3), a compound (A31) or a compound (A32) is preferred.
HOCH₂CF₂O(CF₂CF₂O)_d—Y³{—(OCF₂CF₂)_gO(CF₂)_sCF₃}₂ (A31),
HOCH₂CH(OH)CH₂OCH₂CF₂O(CF₂CF₂O)_d—Y³{—(OCF₂CF₂)_gO(CF₂)_sCF₃}₂ (A32).
When Y³is the group (Y³-1), the compound (A1) is preferably a compound (A1-1), the compound (A2) is preferably 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), and the compound (A3) is preferably a compound represented by the following formula (A3-1a), a compound represented by the following formula (A3-1b) or a combination of a compound represented by the following formula (A3-1a) and a compound represented by the following formula (A3-1b).
The present inventors found that the friction coefficient and the bonding ratio vary depending on the proportion of groups (Z) and therefore decided that the ratio of groups (Z) is within a specific range. Namely, the total number of moles of CF₃groups in the group (Z) in relation to the sum of the total number of moles of CF₃groups in the group (Z) and the total number of moles of OH groups in the group (X) (CF₃/(OH+CF₃), hereinafter referred to as CF₃ratio) is at least 0.001 and at most 0.30. CF₃ratio is preferably at least 0.01 and at most 0.30. By virtue of the CF₃ratio within a specific range, the ether composition of the present invention can attain a low friction coefficient and a high bonding ratio. When the CF₃ratio in the composition is too high, the effect of lowering the friction coefficient is not expected, and trouble such bleed out is aggravated. When the CF₃ratio is too low, the friction coefficient becomes large. However, the composition of the present invention having a low CF₃ratio and more than two compounds has such an effect that it is unlikely to adhere to other substances in contact with it.
The CF₃ratio can be determined by identifying the structures of the compounds in the ether composition and then measuring their contents, or directly from the ether composition.
Specifically speaking, when NMR is used for the determination, the ether composition is analyzed by ¹⁹F-NMR, and the peak area for CF₃groups is determined. The chemical shift of —OCF₃is observed around −54.0 to −56.0 ppm.
The number of terminal OH groups is determined from the area of the peak attributed to the fluorine atoms in CF₂around −80 to −81.0 ppm in the ¹⁹F-NMR spectrum when the terminal groups are —CF₂CH₂OH, from the area of the peak attributed to the fluorine atoms in CF₂around −75.0 to −78.0 ppm in the ¹⁹F-NMR spectrum when the terminal groups are —CF₂CH₂OCH₂CH(OH)CH₂OH, or from the area of the peak attributed to the fluorine atoms in CF₂around −78.0 to −80.0 ppm in the ¹⁹F-NMR spectrum when the of terminal groups are —CF₂CH₂(OCH₂CH₂)_gOH.
The number of terminal OH groups can also be determined by measuring —OCF₃by ¹⁹F-NMR and ¹H-NMR using a compound having both hydrogen and fluorine atoms such as bistrifluoromethylbenzene as an internal control.
For example, it is determined from the area of the peak attributed to CH₂around 4.0 to 4.1 ppm in the ¹H-NMR spectrum when the terminal groups are —CF₂CH₂OH, from the area of the peak attributed to CH₂next to CF₂around 3.8 to 4.0 ppm or the area of the prak attributed to CH₂in terminal CH₂OH around 3.5 ppm when the terminal groups are —CF₂CH₂O(CH₂CH₂O)_g—H, or from the area of the peak attributed to CH in CH(OH) around 3.7 to 3.9 ppm.
In the case of a compound having both —CH₂CH(OH)CH₂— and —CH₂CH₂O—, because ¹H-NMR signals to be used for determination of the number of OH groups overlap, the OH groups attached to these groups are converted to CF₃C(O)O— or CH₃C(O)O— groups etc., and the number of OH groups is determined from the area of the chemical shift peak of such a group in the ¹H-NMR or ¹⁹F-NMR spectrum.
Further, in ¹H-NMR analysis, the peak attributed to OH groups can shift and overlap with the zone important for identification around 3.5 to 3.8 ppm, depending on the measurement environment (such as pH). Therefore, it is preferred to deutrate the hydrogen in OH groups by adding a trace amount of a deuterated solvent (such as heavy water) to a sample to shift the peak attributed to OH groups so that the peak does not overlap with the previously mentioned peaks.
It is preferred that the ether composition of the present invention does not contain a compound (A4). By not containing the compound (A4), it is means that the compound (A4) is not contained at all, or even if present, its content measured by high performance liquid chromatography (hereinafter referred to as HPLC) is at most 2.0 mass %.
Y³(—Z)₃ (A4).
By virtue of the absence of a compound (A4) in the ether composition of the present invention, it is possible to suppress bleed out and to provide a lubricant which firmly bonds to a substrate. It is preferred to remove the compound (A4) from the ether composition by the purification method mentioned later.
The total amount of the compounds (A1) to (A3) is preferably at least 95 mass % in relation to the ether composition, more preferably at least 98 mass %.
When the ether composition consists of a compound (A1) and a compound (A2), the mass ratios (mass %) of the compound (A1) and the compound (A2) in the ether composition is from 50 to 95 for the compound (A1) and from 5 to 50 for the compound (A2), preferably from 60 to 80 for the compound (A1) and from 20 to 40 for the compound (A2).
Further, when the ether composition consists of the compounds (A1) to (A3), the ratios (mass %) of the compound (A1), the compound (A2) and the compound (A3) in the ether composition are from 50 to 90 for the compound (A1), from 5 to 50 for the compound (A2) and from 1 to 25 for the compound (A3), preferably from 60 to 80 for the compound (A1), from 10 to 20 for the compound (A2) and from 5 to 10 for the compound (A3).
The number average molecular weight (hereinafter referred to as Mn) of the ether composition is preferably from 500 to 1,000,000, more preferably from 500 to 100,000, particularly preferably from 1,000 to 20,000.
The molecular weight distribution (hereinafter referred to as Mw/Mn) of the ether composition is preferably from 1.01 to 1.5, more preferably from 1.01 to 1.25. Herein, Mw is the mass average molecular weight.
When the Mn and the Mw/Mn are within the above ranges, the ether composition has a low viscosity, contains a small amount of evaporative components and dissolves homogeneously in a solvent.
The Mn can be measured by gel permeation chromatography (hereinafter referred to as GPC). The Mw/Mn is determined from the Mn and the Mw measured by GPC.
The ether composition of the present invention may be prepared by the following methods.
Method 1: Prepare and purify the compounds (A1) to (A3) respectively and formulate them into a composition.
Method 2: Prepare the compounds (A1) to the compound (A3) so that the resulting reaction product also contains the other two as by-products, and purify the reaction product to a certain CF₃ratio to obtain a composition.
Method 3: Mix two or more compositions obtained after purification in the method 2 into a single composition.
For example, in the method 1, the compound (A1) can be prepared in accordance with the method disclosed in Patent Document 1, and the compounds (A2) and (A3) can be prepared in accordance with the method disclosed in Patent Document 1 by carrying out the reaction by using starting materials for the compounds (A2) and the compound (A3) instead of the starting material for the compound (A1).
In the method 2, a reaction product containing by-products can be obtained by carrying out a reaction in the same manner as in the method 1 or under modified reaction conditions. For example, in a process for preparing the compound (A1) comprising liquid phase fluorination, under severe reaction conditions, the compounds (A2) to (A4) having terminal CF₃groups can be formed by cleavage of molecular terminals. In liquid phase fluorination, the fluorine gas concentration in the gas blown into the liquid phase is preferably from 5.0 to 50 vol %, more preferably from 10 to 30 vol % in view of suppression of formation of the compound (A4).
Under certain reaction conditions, the product of the liquid phase fluorination may contain the compound (A4). If contained, the compound (A4) is preferred to be removed by purification.
As a means for the purification, removal of e.g. metal impurities and anion impurities by an ion adsorbing polymer, supercritical extraction and column chromatography may be mentioned, and it is preferred to combine them.
The ether composition of the present invention may be used as it is, after addition of other compounds or as an additive for other compounds.
The ether composition of the present invention may be used as it is or in combination with other substances. For example, as a lubricant containing the ether composition of the present invention, the composition may be used as it is.
Further, PFPE other than the compounds (A1) to (A3) (hereinafter referred to as other PFPE-XX) may be added to the ether composition. When a PFPE-XX is added to the ether composition of the present invention, its amount is preferably at most 10 mass %, more preferably at most 5 mass % in relation to the total amount of the ether composition (the ether composition of the present invention and the PFPE-XX) so that the present invention can show its characteristics sufficiently.
Further, the ether composition of the present invention may be added to PFPE-XX. The content of the PFPE-XX is preferably at most 50 mass %, more preferably at most 30 mass %, in relation to the total amount of the ether composition. By adding the ether composition of the present invention to PFPE-XX, it is possible to adjust the viscosity of the PFPE-XX and improve the bonding of the PFPE-XX.
Examples of the PFPE-XX used in combination with the ether composition of the present invention include PFPEs-XX having a terminal hydroxyl group and PFPEs-XX having a UV-absorbing terminal group such as those mentioned below.
<PFPEs-XX having a terminal OH group>
FOMBLIN Z-DiOL, FOMBLIN Z-TetraOL, DEMNUM SA and the like.
<PFPEs-XX having a UV-absorbing terminal group>
FOMBLIN Z-DIAC, FOMBLIN Z-DEAL, FOMBLIN AM2001, FOMBLIN Z-DISOC, DEMNUM SH, MorescoA20H and the like.
As another example of PFPE-XX, an ether compound (A⁴) having from 1 to 4 groups (X) and from 0 to 3 groups (Z) and having at least 4 groups (X) and (Z) in total may be mentioned.
The ether compound (A⁴) is preferably at least one member selected from a compound (A⁴1), a compound (A⁴2), a compound (A⁴3) and a compound (A⁴4).
(X—)₄Y⁴ (A⁴1),
(X—)₃Y⁴—Z (A⁴2),
(X—)₂Y⁴(—Z)₂ (A⁴3),
X—Y⁴(—Z)₃ (A⁴4).
X is a group (X), Y4 is a perfluoroalkane-tetrayl group or a perfluoroalkane-triyl group having an etheric oxygen atom inserted between carbon-carbon atoms and having no structure of the group (Z), and Z is a group (Z).
The group (X) is preferably the group (X1), the group (X2), the group (X3) or the group (X4), and the group (X1) or the group (X2) is more preferred in view of the ease of production of the compounds (A⁴1) to (A⁴4) and their stability.
Y⁴is preferred to have no CF₃group.
Y⁴is preferably any one of the groups (Y⁴-1) to (Y⁴-4), and the group (Y⁴-1) is particularly preferred because these compounds are easy to synthesize, are chemically stable and have low crystallinity.
When the ether composition of the present invention and a PFPE-XX are used in combination, the CF₃ratio in the whole composition is preferably adjusted to at least 0.001 and at most 0.30 in order for the ether composition of the present invention to exert its performance. The PFPE-XX is preferred not to contain a PFPE having only CF₃groups at the terminals. In this case, the total number of moles of OH groups covers all the terminal OH groups, and the total number of moles of CF₃groups covers all the CF₃groups other than those attached to a quaternary carbon atom. These total numbers of moles can be determined by NMR as previously described.
Further, it is preferred to use a PFPE-XX having a number average molecular weight of from 1,000 to 10,000 as the PFPE-XX.
The ether composition of the present invention is preferably used as a solvent composition by dissolving or dispersing the ether composition in a solvent.
The solvent is preferably a perfluoroamine (such as perfluorotripropylamine or perfluorotributylamine), a perfluoroalkane (such as Vertrel XF (manufactured by DuPont)) or a hydrofluoroether (such as AE-3000 (manufactured by Asahi Glass Company, Limited)), and a hydrofluoroether is more preferred in view of its low ozone depleting potential.
The solvent composition may be a solution, a suspension or an emulsion and is preferably a solution.
The concentration of the ether composition of the present invention in the solvent composition is preferably from 0.001 to 50 mass %, more preferably from 0.01 to 20 mass %.
The solvent composition may contain or may not contain an additional component other than the ether composition of the present invention and the solvent (hereinafter referred to additional component). When the solvent composition is used as a lubricant, the additional component may be a radical scavenger (such as X1p (manufactured by Dow Chemicals)) or the like.
When the solvent composition is used as a surface modifier, the additional component may be a coupling agent (of a silane, epoxy, titanium or aluminum type). Such a coupling agent improves adhesion between a substrate and a coating.
It is preferred that the solvent composition does not contain metal ions, anions, water, low molecular weight polar compounds or the like because otherwise, the solvent composition would not show the intended performance.
Ions of metals (such as Na, K, Ca and Al) can form Lewis acid catalysts with anions which catalyze decomposition of PFPEs. Anions (of F, Cl, NO₂, NO₃, PO₄, SO₄, C₂O₄and the like) and water can corrode the surface of a substrate. Therefore, the water content of the solvent composition is preferably at most 2,000 ppm. Low molecular weight polar compounds (such as alcohols, plasticizers eluted from resins) can impair the adhesion between a substrate and a coating.
When the ether composition of the present invention is used as a lubricant for magnetic disks, it is used in the same manner as conventional lubricants. For example, it is applied to the surface of a substrate for a magnetic disk by roll coating casting, dip coating (dipping), spin coating, water casting, die coating, Langmuir-Blodgett film formation or vacuum vapor deposition, and dip coating, spin coating or vacuum vapor deposition is preferred.
The substrate may be a NiP-plated substrate (aluminum, glass or the like) having a primer layer, a recording layer and a carbon protective layer in this order.
The carbon protective layer is preferably at most 5.0 mm thick and preferably has an average surface roughness (Ra) of at most 2.0 mm.
After application of a lubricant, a magnetic disk having a lubricant layer is preferably subjected to adsorption treatment so that the lubricant is adsorbed onto the surface of the carbon protective layer.
The adsorption treatment may be heat treatment, infrared treatment, UV treatment or plasma treatment, and is preferably heat treatment or UV treatment, more preferably heat treatment. Further, after adsorption treatment, the magnetic disk may be washed with a fluorine-containing solvent for the purpose of removal of contaminants and an excess of the lubricant.
The surface of the lubricant coating after the adsorption treatment has good water repellency enough to keep the inside the magnetic disk off water and shows good lubricity for a long time.
The bonding ratio of the ether composition of the present invention after adsorption treatment can be at least 60%. It is preferably at least 65%, particularly preferably at least 70%.
The contact angle of water (at room temperature) on the surface of a magnetic disk treated with the ether composition of the present invention can be at least 80°. It is preferably at 85°.
The preferred thickness of a coating formed of the ether composition of the present invention is at most 5.0 nm, more preferably at most 3.0 nm, particularly preferably at most 2.0 nm, in view of improvement of recording density and durability.
The ether composition of the present invention can be applied to surfaces other than those of magnetic disk substrates. For example, it is useful as a surface modifier to be applied to the surfaces of polymer substrates for control of the refractive indices of the substrates, as a surface modifier for improvement in the chemical resistance of polymer substrates by surface modification, as an additive to be added to a wire coating material, an ink repellent (for example, for coating or for a printer such as an ink jet printer), an adhesive for semiconductor devices (such as an adhesive for lead on chip tape, a protective coating for semiconductor (such as a moistureproof coating agent or an ascent inhibitor for soldering) or a thin membrane (such as a pellicle membrane) to be used in optical field, a lubricant for an antireflection film for displays and an antireflection film for resists.
A coating formed from the ether composition of the present invention is transparent, has a low refractive index, and is excellent in heat resistance and chemical resistance. Further, the coating has high lubricity and has self-replenishing property.
The ether composition of the present invention is also useful as a surfactant. For example, it may be used as an additive to lower the surface tension of paint, a leveling agent for paint or a leveling agent for a polishing liquid. When it is added to paint, it is preferably added in an amount of from 0.01 to 5 mass % in relation to the paint.

EXAMPLES

Now, the present invention will be described in further detail with reference to Examples. However, it should be understood that the present invention is by no means thereby restricted.
In the following:
tetramethylsilane is abbreviated as TMS,
CCl₂FCClF₂is abbreviated as R-113,
dichloropentafluoropropane is abbreviated as R-225,
CClF₂CClFCF₂OCF₂CClF₂is abbreviated as CFE-419,
hexafluoroisopropyl alcohol is abbreviated as HFIP, and
Isopropyl alcohol is abbreviated as IPA.

(NMR Analysis)

TMS was used as a standard substance for ¹H-NMR (300.4 MHz), and CFCl₃was used as a standard substance for ¹⁹F-NMR (282.7 MHz). R-113 was used as a solvent for NMR, unless otherwise specified.

(HPLC Analysis)

The ratios of the compounds in the composition were determined with a HPLC analyzer (Prominence, manufactured by Shimadzu Corporation) under the following conditions. Specifically, in each run, the HPFIP concentration in the mobile phase was gradually increased from 0% to 100%, and the mass ratios of compounds in the composition eluted in descending order of the number of OH groups were determined.
Analytical column: normal phase silica gel column (SIL-gel, manufactured by YMC Co., Ltd.)
Mobile phase: R-225 (ASAHIKLIN AK-225G, manufactured by Asahi Glass Company, Limited) and HFIP
Mobile phase flow rate: 1.0 mL/min
Column temperature: 37° C.
Detector: evaporative light scattering detector

(GPC Analysis)

Mn and Mw were measured by GPC in accordance with JP-A-2001-208736 under the following conditions, and Mw/Mn was determined.
Mobile phase: solvent mixture of R-225 (ASAHIKLIN AK-225SEC Grade 1, manufactured by Asahi Glass Company, Limited) and HFIP (R-255/HFIP=99/1 in volume ratio)
Analytical column: serially connected two PLgel MIXED-E columns (manufactured by Polymer Laboratories)
Molecular weight standard samples: four perfluoropolyethers having Mw/Mn less than 1.1 and molecular weights of from 2,000 to 10,000 and one perfluoropolyether having Mw/Mn of at least 1.1 and a molecular weight of 1,300
Mobile phase flow rate: 1.0 mL/min
Column temperature: 37° C.
Detector: evaporative light scattering detector

(Contact Angle)

Contact angles on lubricant coatings were measured with a contact angle meter (CA-X, manufactured by Face). The contact angles between five drops of water or hexadecane with a volume of about 2 μL and the surface of each lubricant coating were measured and averaged.

(Friction Coefficient)

The friction coefficient on the surface of each lubricant coating was measured with a friction meter (Tribogear, manufactured by Heidon) using a SUS ball with a diameter of 10 mm as a contactor under a load 2 kg load at 25 rpm.

(Transfer Test)

After the measurement of friction coefficient, the surface of the contactor was inspected under an optical microscope for lubricant transfer at the four contact points and rated as ◯ when no lubricant transfer was observed, as Δ when lubricant transfer was observed at 1 to 3 contact points and as x when lubricant transfer was observed at all the four contact points.

(Metal Ion Analysis)

The metal ion content in 1.0 g of each fraction was determined by ashing-inductively coupled plasma-mass spectroscopy.

(Anion Analysis)

1.0 g of each fraction or 30 g of ultrapure water was stirred in a polytetrafluoroethylene bottle preliminarily washed with dilute aqueous sodium hydroxide for 24 hours to prepare a sample, and the anion content was determined by water extraction-ion chromatography.

(Water Content)

The water content in each fraction was measured by Karl-Fischer coulometric titration.

Example 1

Polyoxyethylene glycerol ether (Uniox G1200, manufactured by NOF CORPORATION) was reacted with FCOCF(CF₃)OCF₂CF(CF₃)O(CF₂)₃F in the same manner as in Example 11 of Patent Document 1 to obtain a compound (B-1), which was liquid at room temperature. NMR analysis revealed that in the compound (B-1), the average of (k+r+p) was 20.5, R^fwas —CF(CF₃)OCF₂CF(CF₃)OCF₂CF₂CF₃, the Mn was 2,600, and the Mw/Mn was 1.15.
¹H-NMR (solvent: CDCl₃) δ(ppm): 3.4 to 3.8, 4.5.
¹⁹F-NMR (solvent: CDCl₃) δ(ppm): −76.0 to −81.0, −81.0 to −82.0, −82.0 to −82.5, −82.5 to −85.0, −128.0 to −129.2, −131.1, −144.7.

Example 2

Liquid phase fluorination was carried out in the same manner as in Example 2-1 in Patent Document 1 except that R-113 was replaced with CFE-419, and the compound (D3-1) was replaced with the compound (B-1) to obtain a composition (c-1). The composition (c-1) contained a compound (C-1) as a main component, and in the composition, at least 99.9 mol % of the hydrogen atoms in the compound (B-1) had been replaced by fluorine atoms.

Example 3

Liquid phase fluorination was carried out in the same manner as in Example 2 except that the fluorine gas concentration in the gals blown into the liquid phase was changed from 20 vol % to 10 vol % to obtain a composition (c-2).

Example 4

Liquid phase fluorination was carried out in the same manner as in Example 2 except that the fluorine gas concentration in the gals blown into the liquid phase was changed from 20 vol % to 50 vol % to obtain a composition (c-3).
¹H-NMR (solvent: CDCl₃) δ(ppm): 5.9 to 6.4.
¹⁹F-NMR (solvent: CDCl₃) δ(ppm): −55.8, −77.5 to −86.0, −88.2 to −92.0, −120.0 to −139.0, −142.0 to −146.0.

Example 5

Example 3 in Patent Document 1 was followed except that the compound (D4-1) was replaced with the composition (c-1), with the composition (c-2) and with the composition (c-3), to obtain a composition (d-1), a composition (d-2) and a composition (d-3) each containing a compound (D-1) as a main component.

Example 6

Example 4-1 in Patent Document 1 was followed except that the compound (D5-1) was replaced with the composition (d-1), with the composition (d-2) and with the composition (d-3), to obtain a composition (e-1), a composition (e-2) and a composition (e-3) each containing a compound (E-1) as a main component.

Example 7

Example 5 in Patent Document 1 was followed except that the compound (D7-1) was replaced with the composition (e-1), with the composition (e-2) and with the composition (e-3), to obtain a composition (a-1), a composition (a-2) and a composition (a-3) each containing a compound (A11-1) as a main component.
NMR analysis and HPLC analysis revealed that each of the resulting compositions contained compounds having two terminal OH groups (A21-1a) and (A21-1b) (hereinafter the compounds (A21-1a) and (A21-1b) are collectively referred to as (A21-1)) and compounds having one terminal OH group (A31-1a) and (A31-1b) (hereinafter the compounds (A31-1a) and (A31-1b) are collectively referred to as (A31-1)).
The NMR spectrum patterns of the compound (a-1), the composition (a-2) and the composition (a-3):
¹H-NMR δ(ppm): 3.94.
¹⁹F-NMR δ(ppm): −54.0, −80.1, −88.2 to −90.5, −135.0 to −139.0.
The results of NMR analysis, HPLC analysis and GPC analysis are shown in Table 1.
The ratio of terminal OH groups to terminal CF₃groups in the molecule were calculated from the ratio of the area of the peak attributed to the fluorine atoms in CF₃groups around −54.0 ppm to the area of the peak attributed to the fluorine atoms in CF₂groups in CF₂CH₂OH groups around −80.1 ppm.

TABLE 1

	NMR analysis
Fluorine gas	Ratio of terminal	HPLC analysis	GPC
concentration	functional groups [%]	Compositional ratio [%]	analysis

Composition	[%]	CF₃OCF₂—	—CF₂CH₂OH	A31-1	A21-1	A11-1	Mn	Mw/Mn

a-1	20	7	93	1	18	81	2,000	1.07
a-2	10	3	97	1	9	90	2,100	1.05
a-3	50	21	79	20	30	50	1,850	1.13

Example 8

The composition (a-3) was purified by column chromatography as follows.
A slurry of a particulate silica gel (MS-Gel D75-120A, manufactured by S. I. Tech Co., Ltd.) in R-225 was packed into a column with a diameter of 150 mm and a length of 500 mm to form a silica gel bed with a height of 100 mm.
150 g of the composition (a-3) was loaded on the silica gel bed and fractionated by using extraction solvents (solvent mixtures of R225 and IPA) with gradually increasing IPA concentrations to obtain fractions (p1-1) to (p1-5). The volumes of the extraction solvents, the IPA concentrations in the extraction solvents and the masses of the fractions are shown in Table 2.

TABLE 2

	IPA concentration	Volume of extraction solvent
Fraction	[%]	[L]	Mass [g]

p1-1	0	5	50
p1-2	20	3	35
p1-3	50	3	32
p1-4	70	3	15
p1-5	100	5	3

Total:	135
Loaded amount:	150

Each fraction was analyzed by HPLC and GPC. The results are shown in Table 3.

	TABLE 3

	HPLC analysis	GPC
	compositional ratio [%]	analysis

	A31-1	A21-1	A11-1	Mn	Mw/Mn

a-3	20	30	50	1,850	1.15
p1-1	37	48	15	1,750	1.15
p1-2	20	39	41	1,810	1.13
p1-3	1	23	76	1,850	1.14
p1-4	0	10	90	1,860	1.10
p1-5	0	6	94	2,100	1.10

In the extraction by column chromatography, because of the influence of the number of terminal hydroxyl groups, the proportions of the compound (A21-1) and the compound (A31-1) were high in less polar fractions, and the proportion of the compound (A11-1) was high in more polar fractions.

Example 9

The fraction (p1-3) was purified by supercritical extraction as follows.
A thick-walled stainless steel vessel (inner diameter φ33 mm×depth 45 mm) having an inlet and an outlet, a supercritical carbon dioxide delivery pump (SCF-210, manufactured by JASCO Corporation), an automatic back pressure regulator (880-01, manufactured by JASCO Corporation) and an ordinary chromatographic column oven were assembled into an apparatus.
30 g of the fraction (p1-3) was injected into the vessel, and supercritical carbon dioxide was feed at a flow rate of 2.5 cc/min in terms of liquid carbon dioxide. The pressure in the vessel was changed with time, while the temperature in the vessel was maintained at 60° C., and extracts at different pressures were collected as fractions (p2-1) to (p2-7). The pressure in the vessel, the pressure holding time and the amounts of the fractions are shown in Table 4.

TABLE 4

Fraction	Pressure [MPa]	Holding time [min]	Mass [g]

p2-1	10 → 11	75 → 120	0.25
p2-2	12	120	1.81
p2-3	13	120	5.46
p2-4	13.5	120	8.26
p2-5	14	120	9.17
p2-6	15	120	3.63
p2-7	16 → 20 → 25	90 → 60 → 60	0.60
Residue			0.01

	Extracts + residue:	29.19
	Injected amount:	30

Each fraction was analyzed by HPLC, NMR and GPC. The results are shown in Table 5. In the supercritical extraction, because of the influence of molecular weight, molecules were extracted in the ascending order of molecular weight.

	TABLE 5

	HPLC analysis	GPC
	compositional ratio [%]	analysis

	A31-1	A21-1	A11-1	Mn	Mw/Mn

p1-3	1	23	76	1,850	1.15
p2-1	37	53	9	1,750	1.1
p2-2	20	53	27	1,980	1.08
p2-3	6	42	51	2,030	1.09
p2-4	1.3	30	68	2,150	1.10
p2-5	0	4	96	2,500	1.14
p2-6	0	2	98	2,700	1.79
p2-7	0	0	100	—	—

Each fraction was examined on the solubility in R-225, Vertrel XF (manufactured by Du Pont) and AE-3000 (manufactured by Asahi Glass Company, Limited). Each fraction was mixed with the solvents at a concentration of 1 mass %, and the solubilities were examined visually. All the fractions were soluble in all the solvents.

Examples 10 to 12

Working Examples

A carbon protective layer was formed on glass blanks for magnetic disks (2.5″ blanks, manufactured by Asahi Glass Company, Limited) by depositing DLC (diamond-like carbon) by radio-frequency magnetron sputtering using a carbon target to obtain stimulant disks. The Ar gas pressure was 0.003 Torr, and the input power density on the target was 3 W/cm². The carbon protective layers were 30 nm thick. The water contact angle on the carbon protective layers was 40°.
The fractions (p2-2), (p2-3) and (p2-5) were diluted with Vertrel XF to obtain solvent compositions having a fraction concentration of 0.01 mass %.
The stimulant disks were dipped in the solvent compositions for 30 seconds and pulled out at a constant rate of 6 mm/sec. The stimulant disks coated with the solvent compositions were subjected to heat treatment in a thermostatic oven at 100° C. for 1 hour to form lubricant coatings. The disks having lubricant coatings were rinsed with Vertrel XF for 30 seconds by dipping. The thicknesses of the lubricant coatings were measured with an ellipsometer before and after rinsing to determine the bonding ratios. The contact angles and friction coefficients on the surfaces of the lubricant coatings were measured. After measurement of friction coefficients, the surface of the contactor was inspected under an optical microscope for lubricant transfer. The results are shown in Table 6.

Example 13

Reference Example

A lubricant coating was formed on the surface of a stimulant disk in the same manner as in Example 1 except that the fraction (p2-2) was replaced with the compound (F) (FOMBLIN Z-TetraOL, Mn: 3,000, Mw/Mn=1.23, manufactured by Solvay) and evaluated in the same manner as in Example 10. The CF₃ratio in the compound is 0.
HOCH₂CH(OH)CH₂OCH₂CF₂O(CF₂O)_i(CF₂CF₂O)_ii—CF₂CH₂OCH₂CH(OH)CH₂OH (F)
wherein i/ii=1.0.

Examples 14 and 15

Lubricant coatings were formed on stimulant disks in the same manner as in Example 10 except that the fraction (p2-2) was replaced with the fraction (p2-6) or (p2-7) and evaluated in the same manner as in Example 10. The results are shown in Table 6.

TABLE 6

		Coating	Bonding	Friction
CF₃	Contact angle [°]	thickness	ratio	coefficient	Transfer

Ex.		ratio	Water	Hexadecane	[mm]	[%]	[—]	test

10	p2-2	0.31	108	76	1.5	60	1.2	◯
11	p2-3	0.18	102	72	1.8	75	1.2	◯
12	p2-5	0.013	88	61	2.1	82	1.4	◯
13	FOMBLIN Z	0	93	62	1.6	80	3.2	◯
	TetraOL
14	p2-6	0.007	n.d.	n.d.	n.d.	n.d.	n.d.	◯
15	p2-7	0	n.d.	n.d.	n.d.	n.d.	n.d.	X

The results of Examples 10 to 12 indicate that a composition comprising PFPEs having three terminal groups having specific structures at the molecular terminals can provide a surface with a high bonding ratio, a large contact angle and a small friction coefficient, when the OH/CH₃ratio is more than 2 and at most 100.

Example 16

Metal ion and anion analyses of the fractions (p2-2), (p2-3) and (p2-5) and measurement of their water contents were carried out. The results are shown in Table 7.

TABLE 7

p2-2	p2-3	p2-5

Metal ions	Al	10	<1	30
[ppb]	Na	260	130	200
	K	60	11	35
	Mg	70	300	400
	Ca	350	800	200
	Cr	3	n.d.	1
	Mn	n.d.	n.d.	3
	Fe	10	8	20
	Co	n.d.	n.d.	n.d.
	Ni	5	3	10
	Cu	3	n.d.	3
	Zn	10	8	10
	Ba	2	n.d.	3
	Pb	n.d.	n.d.	n.d.
Anions	F	650	1,600	1,800
[ppb]	Formic acid	n.d.	n.d.	n.d.
	Cl	620	230	110
	NO₃	n.d.	120	230
	SO₄	930	360	550
	Oxalic acid	900	700	1,100
Water		960	940	900
content
[ppm]

n.d. not detected

INDUSTRIAL APPLICABILITY

The ether composition of the present invention shows a high bonding ratio, forms a coating having a low friction coefficient surface and is useful as a lubricant to be applied on the surface of magnetic recording media.
The entire disclosures of Japanese Patent Application No. 2007-327619 filed on Dec. 19, 2007 and Japanese Patent Application No. 2008-196370 filed on Jul. 30, 2008 including specifications, claims and summaries are incorporated herein by reference in their entireties.

Claims

1. An ether composition comprising at least two compounds selected from the group consisting of a compound represented by the following formula (A1), a compound represented by the following formula (A2) and a compound represented by the following formula (A3), wherein the total number of moles of CF₃groups in the group represented by the following formula (Z) in relation to the sum of the total number of moles of CF₃groups in the group represented by the following formula (Z) and the total number of moles of OH groups in the group represented by the following formula (X) (CF₃/(OH+CF₃)) is at least 0.001 and at most 0.30:

(X—)₃Y³ (A1),

(X—)₂Y³—Z (A2),

X—Y³(—Z)₂ (A3).

Wherein X is a group represented by the following formula (X),

Y³is a perfluoroalkane-triyl group or a perfluoroalkane-triyl group having an etheric oxygen atom inserted between carbon-carbon atoms, provided that when Y³has a CF₃group, the CF₃group is bonded to a quaternary carbon,

HO—(CH₂CH₂O)_a.(CH₂CH(OH)CH₂O)_b-Q- (X),

CF₃(CF₂)_sO(CF₂CF₂O)_g— (Z).

Wherein 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, a polyfluorinated polymethylene group having an etheric oxygen atom bonded between carbon-carbon atoms, a polyfluorinated polymethylene group having an etheric oxygen atom bonded to the terminal carbon atom bonded to Y³or a polyfluorinated polymethylene group having an etheric oxygen atom bonded between carbon-carbon atoms and an etheric oxygen atom bonded to the terminal carbon atom bonded to Y³.

2. The ether composition according to claim 1, 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):

HOCH₂CF₂O(CF₂CF₂O)_d— (X1),

HOCH₂CH(OH)CH₂OCH₂CF₂O(CF₂CF₂O)_d— (X2),

HOCH₂CH₂CF₂O(CF₂CF₂O)_d— (X3),

HOCH₂CH₂OCH₂CF₂O(CF₂CF₂O)_d— (X4),

wherein d is an integer of from 1 to 200.

3. The ether composition according to claim 1, wherein Y³is a group selected from the group consisting of a group represented by the following formula (Y³-1), a group represented by the following formula (Y³-2) and a group represented by the following formula (Y³-3).

4. The ether composition according to claim 1, 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), and the compound represented by the formula (A3) is a compound represented by the following formula (A3-1a), a compound represented by the following formula (A3-1b) or a combination of a compound represented by the following formula (A3-1a) and a compound represented by the following formula (A3-1b).

5. The ether composition according to claim 1, wherein the compound represented by the formula (A1), the compound represented by the formula (A2) and the compound represented by the formula (A3) have no —OCF₂O— structure.

6. The ether composition according to claim 1, wherein the total amount of the compound represented by the formula (A1), the compound represented by the formula (A2) and the compound represented by the formula (A3) is at least 95 mass % in relation to the ether composition.

7. 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 (mass average molecular weight/number average molecular weight) of from 1.01 to 1.5.

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