METHOD FOR PRODUCING A FLUORINE-CONTAINING POLYMER AND COMPOSITION THEREIN

Description

Technical Field

[0001] The present invention relates to a method for producing a fluorine-containing polymer, and to a composition containing the fluorine-containing polymer.Background Art

[0002] Fluorine-containing polymers obtained by polymerizing a fluorine-containing monomer having one or more polymerizable carbon-carbon double bonds and one or more oxygen atoms as a ring-constituting atom have been used as, for example, coating materials for anti-reflection films formed on photoresist layers in photolithography technology.

[0003] JP-A-2018-119019 discloses that CF 3 CF 2 CF 2 CF 2 CF 2 CF 2 CH 2 CH 3 as a solvent was added to a fluorine-containing polymer obtained by polymerizing CF 2 =CFOCF 2 CF 2 CF=CF 2 , thereby obtaining a composition having a fluorine-containing polymer content of 20 mass% (Example 6).

[0004] JP-A-2005-314482 discloses that CF 2 =CFCF 2 CF 2 OCF=CF 2 and another fluorine-containing monomer were copolymerized in the absence of a solvent, thereby obtaining a fluorine-containing polymer (Example 2).

[0005] WO 2013 / 018730 discloses that a solution composition containing a fluorine-containing polymer in an amount of 10 mass% was obtained (Production Examples 1-7).

[0006] R.H. French et al., J. Fluorine Chem., 122, 63-80 (2993) discloses hydrofluorocarbon polymers for use as pellicles in 157 nm semiconductor photolithography, which are copolymers of vinylidene fluoride (VdF) with cyclic fluoroether monomers, and especially of VdF and 2-(difluoromethylene)-4,4,5-trifluoro-5-(trifluoromethyl)-1,3-dioxolane.Summary of InventionTechnical Problem

[0007] A primary object of the present invention is to provide a method for producing a fluorine-containing polymer and a composition containing the fluorine-containing polymer.Solution to Problem

[0008] The present invention provides a composition (also referred to as "the present composition" hereinafter) comprising: (1) an aprotic solvent (B) which is at least one of a perfluorotrialkylamine, a perfluoroalkane, a perfluorocyclic ether, and a hydrofluoroether; and (2) dissolved in the aprotic solvent (B), ≥ 20 mass%, based on the mass of the composition, of a polymer (A3) comprising, based on all structural units in the polymer (A3), ≥ 50 mol% of structural units of the formula (A3) wherein R 6< -R 9< each independently are F, C 1-5 -perfluoroalkyl, or C 1-5 -perfluoroalkoxy.

[0009] Also, the present invention provides a method for producing a polymer (A3) comprising, based on all structural units in the polymer (A3), ≥ 50 mol% of structural units of the formula (A3) wherein R 6< -R 9< each independently are F, C 1-5 -perfluoroalkyl, or C 1-5 -perfluoroalkoxy, by subjecting, in the presence of a polymerization initiator, a monomer comprising a monomer (M) corresponding to the structural unit (A3) in the polymer (A3) to polymerization reaction in at least one aprotic solvent (B), which solvent (B) is a hydrofluoroether, wherein the polymer (A3) is dissolved in the solvent (B), and the amount of the polymer (A3) dissolved in the solvent (B) is ≥ 20 mass% based on the total mass of the polymer (A) and the solvent (B) .

[0010] Preferred embodiments of the invention are as defined in the appended dependent claims and / or in the following detailed description.Advantageous Effects of Invention

[0011] The present invention provides a method for producing a fluorine-containing polymer that comprises as a main component a structural unit containing a fluorine-containing aliphatic ring and that can be dissolved at a high concentration (in particular, 20 mass% or more) in an aprotic solvent. The present invention provides a composition in which a fluorine-containing polymer comprising as a main component a structural unit containing a fluorine-containing aliphatic ring is dissolved at a high concentration (in particular, 20 mass% or more) in an aprotic solvent. The present invention can provide a composition comprising a fluorine-containing polymer containing the structural unit of formula (A3) described above as a main component, which has been considered to be difficult to dissolve in a nonperfluoro solvent; and a nonperfluoro solvent, wherein the fluorine-containing polymer is dissolved.Description of EmbodimentsTerms

[0012] Unless otherwise specified, the symbols and abbreviations in the present specification can be understood in the context of the present specification in the meanings commonly used in the technical field to which the present invention belongs. Unless otherwise specified, herein the following definitions apply.

[0013] The terms "comprise" and "contain" are used with the intention of including the terms "consisting essentially of" and "consisting of."

[0014] The steps, treatments, or operations described in the present specification may be performed at room temperature.Room temperature can refer to a temperature within the range of 10-40°C.

[0015] The phrase "C n -C m " (n and m are each a number) indicates that the number of carbon atoms is n or more and m or less, as a person skilled in the art would generally understand.

[0016] The description of compounds can include all stereoisomers (such as enantiomers, diastereomers, and geometric isomers) .

[0017] The phrases "compound of formula (N)," "structural unit of formula (N)," and "monomer of formula (N)" can be referred to as "compound (N)," "structural unit (N)," and "monomer (N)," respectively.

[0018] The "fluorine-containing aliphatic ring" contains a plurality of carbon atoms and one, two, or three etheric oxygen atoms as ring-constituting atoms. When the "fluorine-containing aliphatic ring" contains a plurality of oxygen atoms as ring-constituting atoms, the oxygen atoms are not adjacent to each other.

[0019] The "fluorine-containing aliphatic ring" includes a saturated aliphatic monocyclic ring containing one or more fluorine atoms.

[0020] The "fluorine-containing aliphatic ring" includes a ring of four or more members (e.g., a 4-membered ring, a 5-membered ring, a 6-membered ring, or a 7-membered ring).

[0021] The "fluorine-containing aliphatic ring" may have at least one group selected from the group consisting of perfluoroalkyl (e.g., linear or branched C 1-5 -perfluoroalkyl) and perfluoroalkoxy (e.g., linear or branched C 1-5 -perfluoroalkoxy) as a substituent. The number of substituents may be one or more, such as 1-4, 1-3, 1-2, 1, 2, 3, or 4.

[0022] In the "fluorine-containing aliphatic ring," one or more fluorine atoms may be attached to one or more ring-constituting carbon atoms.

[0023] Examples of the "fluorine-containing aliphatic ring" include perfluorooxetane, perfluorotetrahydrofuran, perfluorodioxolane, perfluorotetrahydropyran, perfluoro-1,3-dioxane, perfluorooxepane optionally, perfluoro-1,3-dioxepane, perfluoro-1,4-dioxepane, and perfluoro-1,3,5-trioxepane, each optionally having one or more substituents.

[0024] Examples of "alkyl" include linear or branched C 1-10 -alkyl, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, hexyl, heptyl, octyl, nonyl, and decyl.

[0025] "Fluoroalkyl" is alkyl in which at least one hydrogen atom is replaced by a fluorine atom. "Fluoroalkyl" may be linear or branched fluoroalkyl.

[0026] The number of carbon atoms in "fluoroalkyl" may be, for example, 1-12, 1-6, 1-5, 1-4, 1-3, 6, 5, 4, 3, 2, or 1.

[0027] The number of fluorine atoms in "fluoroalkyl" may be 1 or more (e.g., 1-3, 1-5, 1-9, 1-11, or 1 to the maximum substitutable number).

[0028] "Fluoroalkyl" includes perfluoroalkyl. "Perfluoroalkyl" is alkyl in which all of the hydrogen atoms are replaced by fluorine atoms.

[0029] Examples of perfluoroalkyl include trifluoromethyl (CF 3 -), pentafluoroethyl (C 2 F 5 -), heptafluoropropyl (CF 3 CF 2 CF 2 -), and heptafluoroisopropyl ((CF 3 ) 2 CF-).

[0030] Specific examples of "fluoroalkyl" include monofluoromethyl, difluoromethyl, trifluoromethyl (CF 3 -), 2,2,2-trifluoroethyl, perfluoroethyl (C 2 F 5 -), tetrafluoropropyl (e.g., HCF 2 CF 2 CH 2 -), hexafluoropropyl (e.g., (CF 3 ) 2 CH-), perfluorobutyl (e.g., CF 3 CF 2 CF 2 CF 2 -), octafluoropentyl (e.g., HCF 2 CF 2 CF 2 CF 2 CH 2 -), perfluoropentyl (e.g., CF 3 CF 2 CF 2 CF 2 CF 2 -), and perfluorohexyl (e.g., CF 3 CF 2 CF 2 CF 2 CF 2 CF 2 -).

[0031] "Alkoxy" may be a group represented by RO-, wherein R is alkyl (e.g., C 1-10 -alkyl).

[0032] Examples of "alkoxy" include linear or branched C 1-10 -alkoxy, such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy, isopentyloxy, neopentyloxy, hexyloxy, heptyloxy, octyloxy, nonyloxy, and decyloxy.

[0033] "Fluoroalkoxy" is alkoxy in which at least one hydrogen atom is replaced by a fluorine atom. "Fluoroalkoxy" may be linear or branched fluoroalkoxy.

[0034] The number of carbon atoms in "fluoroalkoxy" may be, for example, 1-12, 1-6, 1-5, 1-4, 1-3, 6, 5, 4, 3, 2, or 1.

[0035] The number of fluorine atoms in "fluoroalkoxy" may be 1 or more (e.g., 1-3, 1-5, 1-9, 1-11, or 1 to the maximum substitutable number).

[0036] "Fluoroalkoxy" includes perfluoroalkoxy. "Perfluoroalkoxy" is alkoxy in which all of the hydrogen atoms are replaced by fluorine atoms.

[0037] Examples of "perfluoroalkoxy" include trifluoromethoxy, pentafluoroethoxy, heptafluoropropoxy, and heptafluoroisopropoxy.

[0038] Specific examples of "fluoroalkoxy" include fluoromethoxy, difluoromethoxy, trifluoromethoxy, pentafluoroethoxy, heptafluoropropoxy (e.g., CF 3 CF 2 CF 2 O-, (CF 3 ) 2 CFO-), and nonafluorobutoxy (e.g., CF 3 CF 2 CF 2 CF 2 O-, (CF 3 ) 3 CO-).Composition

[0039] An embodiment of the present invention is a composition comprising (A3) a fluorine-containing polymer (also referred to as "polymer (A3)" herein) comprising, based on all structural units in the polymer (A3), ≥ 50 mol% of structural units of the formula (A3) wherein R 6< -R 9< each independently are F, C 1-5 -perfluoroalkyl, or C 1-5 -perfluoroalkoxy and (B) an aprotic solvent which is at least one of a perfluorotrialkylamine, a perfluoroalkane, a perfluorocyclic ether, and a hydrofluoroether. The composition is in a liquid form and the polymer (A3) is dissolved in the aprotic solvent (B).

[0040] In the composition, the fluorine-containing aliphatic ring of the polymer (A3) contains one, two, or three etheric oxygen atoms as a ring-constituting atom, and when the fluorine-containing aliphatic ring contains a plurality of etheric oxygen atoms, the etheric oxygen atoms are not adjacent to each other.Fluorine-Containing Polymer (A)

[0041] The polymer (A3) comprises, based on all structural units in the polymer (A3), ≥ 50 mol% of structural units of the formula (A3) wherein R 6< -R 9< each independently are F, C 1-5 -perfluoroalkyl, or C 1-5 -perfluoroalkoxy.

[0042] The proportion of the structural unit (A3) in the polymer (A) is preferably 80 mol% or more, more preferably 90 mol% or more, and particularly preferably 100 mol%.

[0043] The structural unit (A3) in the polymer (A3) may be one or more types of structural units, preferably one to three types, more preferably one or two types, and particularly preferably one type.

[0044] In the structural unit (A3), R 6< -R 9< may be each independently F, linear or branched C 1-3 -perfluoroalkyl, or linear or branched C 1-3 -perfluoroalkoxy. R 6< -R 9< are preferably each independently F, trifluoromethyl, perfluoroethyl, or trifluoromethoxy, and more preferably F, trifluoromethyl, or trifluoromethoxy.

[0045] The structural unit (A3) is preferably a structural unit of formula (A3), wherein R 6< -R 9< each independently are F or trifluoromethyl.

[0046] The structural unit (A3) is more preferably a structural unit of formula (A3), wherein R 6< -R 9< are F; R 6< -R 8< are F, and R 9< is trifluoromethyl; R 6< are trifluoromethyl, and R 7< -R 9< are F; or R 6< and R 9< are trifluoromethyl, and R 7< and R 8< are F.

[0047] Preferred examples of the structural unit (A3) include a structural unit (A3-1) of the formula

[0048] The polymer (A3) may comprise other structural units in addition to the structural unit (A3). The proportion of the other structural units in all of the structural units in the polymer (A3) is 50 mol% or less, preferably 20 mol% or less, more preferably 10 mol% or less, and particularly preferably 0 mol%.

[0049] Examples of the other structural units include a structural unit (A11) of formula (A11): wherein R 111< is F, C 1-6 -perfluoroalkyl, or C 1-6 -perfluoroalkoxy.

[0050] For example, the polymer (A3) may contain a structural unit (A2-1): and a structural unit (A11-1) of formula (A11-1):

[0051] R 111< may be F, linear or branched C 1-6 -perfluoroalkyl, or linear or branched C 1-6 -perfluoroalkoxy, and preferably is F, linear or branched C 1-4 -perfluoroalkyl, or linear or branched C 1-4 -perfluoroalkoxy, more preferably F, linear or branched C 1-3 -perfluoroalkyl, or linear or branched C 1-3 -perfluoroalkoxy, particularly preferably F or trifluoroalkyl.

[0052] The mass average molecular weight of the polymer (A3) may be, for example, within the range of 5000-1000000, 10000-1000000, 10000-500000, or 90000-350000. The mass average molecular weight of the polymer (A3) is preferably within the range of 10000-750000, more preferably 40000-500000, and particularly preferably 70000-350000.

[0053] The lower limit of the mass average molecular weight of the polymer (A3) may be, for example, 5000 or more, preferably 10000 or more, more preferably 40000 or more, and particularly preferably 70000 or more. The upper limit of the mass average molecular weight of the polymer (A3) may be, for example, 1000000 or less, preferably 750000 or less, more preferably 500000 or less, and particularly preferably 350000 or less. The above upper and lower limits may be appropriately combined.

[0054] The mass average molecular weight of the polymer (A3) is a value determined by a gel permeation chromatography (GPC) method (in particular, the GPC method described later in the Examples) .

[0055] In the present composition, the content of the polymer (A3) may be 20 mass% or more based on the mass of the composition, preferably 20-65 mass%, more preferably > 20 to 65 mass%, and particularly preferably > 20 to 50 mass%.

[0056] The polymer (A3) can be synthesized by a known method. For example, the polymer (A3) can be synthesized by polymerizing a monomer corresponding to the structural unit of the fluorine-containing polymer. The polymerization method may be, for example, radical polymerization, bulk polymerization, solution polymerization, suspension polymerization, or emulsion polymerization. The method of the present invention for producing the polymer (A3) is particularly preferable because the polymer (A3) can be dissolved in a solvent at a high concentration.Aprotic Solvent (B)

[0057] The present composition comprises an aprotic solvent (B). The aprotic solvent is at least one of a perfluorotrialkylamine, a perfluoroalkane, a perfluorocyclic ether, and a hydrofluoroether.

[0058] The perfluoro solvent is an aprotic solvent that contains fluorine and carbon atoms and contains no hydrogen atoms.. The perfluoro solvents may be used singly or in a combination of two or more.

[0059] The hydrofluoroether is a nonperfluoro aprotic solvent that contains fluorine, carbon, and hydrogen atoms.. The hydrofluoroether solvents may be used singly or in a combination of two or more. hydrofluoroether solvents have global warming potentials that are generally lower than those of perfluoro solvents, and are thus preferred solvents in terms of the burden on the environment. On the other hand, hydrofluoroether solvents have been considered to have a low ability to dissolve fluoropolymers. However, the present inventors found that hydrofluoroether solvents can dissolve a polymer comprising, based on all structural units in the polymer (A3), ≥ 50 mol% of the structural unit (A3).

[0060] The perfluorotrialkylamine is, for example, an amine substituted with three linear or branched perfluoroalkyl groups. The number of carbon atoms of each perfluoroalkyl group is, for example, 1-10, preferably 1-5, and more preferably 1-4. The perfluoroalkyl groups may be the same or different, and are preferably the same.

[0061] Examples of perfluorotrialkylamines include perfluorotrimethylamine, perfluorotriethylamine, perfluorotripropylamine, perfluorotriisopropylamine, perfluorotributylamine, perfluorotri-sec-butylamine, perfluorotri-tert-butylamine, perfluorotripentylamine, perfluorotriisopentylamine, and perfluorotrineopentylamine.

[0062] Preferred examples of perfluorotrialkylamines include perfluorotripropylamine and perfluorotributylamine.

[0063] The perfluoroalkane is, for example, a linear, branched, or cyclic C 3-12 - (preferably C 3-10 -, more preferably C 3-6 -) perfluoroalkane.

[0064] Examples of perfluoroalkanes include perfluoropentane, perfluoro-2-methylpentane, perfluorohexane, perfluoro-2-methylhexane, perfluoroheptane, perfluorooctane, perfluorononane, perfluorodecane, perfluorocyclohexane, perfluoro(methylcyclohexane), perfluoro(dimethylcyclohexane) (e.g., perfluoro(1,3-dimethylcyclohexane)), and perfluorodecalin.

[0065] Preferred examples of perfluoroalkanes include perfluoropentane, perfluorohexane, perfluoroheptane, and perfluorooctane.

[0066] The perfluorocyclic ether is, for example, a perfluorocyclic ether optionally having one or more perfluoroalkyl groups. The ring(s) of the perfluorocyclic ether may be 3- to 6-membered ring(s). The ring(s) of the perfluorocyclic ether may have one or more oxygen atoms as a ring-constituting atom. The ring(s) preferably have one or two oxygen atoms, more preferably one oxygen atom.

[0067] The perfluoroalkyl group as a substituent is, for example, linear or branched C 1-6 -, C 1-5 -, or C 1-4 -perfluoroalkyl. The perfluoroalkyl group is preferably linear or branched C 1-3 -perfluoroalkyl.

[0068] The number of substituents is, for example, 1-4, preferably 1-3, and more preferably 1-2. When a plurality of substituents are present, they may be the same or different.

[0069] Examples of perfluorocyclic ethers include perfluorotetrahydrofuran, perfluoro-5-methyltetrahydrofuran, perfluoro-5-ethyltetrahydrofuran, perfluoro-5-propyltetrahydrofuran, perfluoro-5-butyltetrahydrofuran, and perfluorotetrahydropyran.

[0070] Preferred examples of perfluorocyclic ethers include perfluoro-5-ethyltetrahydrofuran and perfluoro-5-butyltetrahydrofuran.

[0071] The hydrofluoroether is, for example, a fluorine-containing ether.

[0072] The hydrofluoroether preferably has a global warming potential (GWP) of 600 or less, more preferably 400 or less, and particularly preferably 300 or less. The lower limit of the global warming potential (GWP) of the hydrofluoroether may be 1 or more, or 5 or more.

[0073] Examples of hydrofluoroethers include CF 3 CF 2 CF 2 CF 2 OCH 3 , CF 3 CF 2 CF(CF 3 )OCH 3 , CF 3 CF(CF 3 )CF 2 OCH 3 , CF 3 CF 2 CF 2 CF 2 OC 2 H 5 , CF 3 CH 2 OCF 2 CHF 2 , C 2 F 5 CF(OCH 3 )C 3 F 7 , (CF 3 ) 2 CHOCH 3 , (CF 3 ) 2 CFOCH 3 , CHF 2 CF 2 OCH 2 CF 3 , CHF 2 CF 2 CH 2 OCF 2 CHF 2 , CF 3 CHFCF 2 OCH 3 , CF 3 CHFCF 2 OCF 3 , trifluoromethyl 1,2,2,2-tetrafluoroethyl ether (HFE-227me), difluoromethyl 1,1,2,2,2-pentafluoroethyl ether (HFE-227mc), trifluoromethyl 1,1,2,2-tetrafluoroethyl ether (HFE-227pc), difluoromethyl 2,2,2-trifluoroethyl ether (HFE-245mf), 2,2-difluoroethyltrifluoromethyl ether (HFE-245pf), 1,1,2,3,3-hexafluoropropyl methyl ether (CF 3 CHFCF 2 OCH 3 ), 1,1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (CHF 2 CF 2 OCH 2 CF 3 ), and 1,1,1, 3, 3, 3-hexafluoro-2-methoxypropane ((CF 3 ) 2 CHOCH 3 ).

[0074] Preferred examples of hydrofluoroethers include CF 3 CF 2 CF 2 CF 2 OCH 3 , CF 3 CF 2 CF 2 CF 2 OC 2 H 5 , CF 3 CH 2 OCF 2 CHF 2 , C 2 F 5 CF(OCH 3 )C 3 F 7 , 1,1,2,3,3-hexafluoropropyl methyl ether (CF 3 CHFCF 2 OCH 3 ), 1,1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (CHF 2 CF 2 OCH 2 CF 3 ), and 1,1,1, 3, 3, 3-hexafluoro-2-methoxypropane ((CF 3 ) 2 CHOCH 3 ).

[0075] The hydrofluoroether may be at least one member selected from compounds of the formulae (B-1), (B-2), (B-3), (B-4), (CF 3 ) 2 CHOCH 3 , (CF 3 ) 2 CFOCH 3 , CF 3 CHFCF 2 OCH 3 , and CF 3 CHFCF 2 OCF 3 .         F(CF 2 ) p O(CH 2 ) q H     (B-1),         H(CF 2 ) p O(CF 2 ) q F     (B-2),         H(CF 2 ) p O(CH 2 ) q H     (B-3), Wherein, each independently in the formulae, p and q are an integer of 1-6, and q is an integer of 1-4.         X(CF 2 ) p CH 2 O(CF 2 ) q H     (B-4), wherein X is F or H, and p and q are as defined above.

[0076] The hydrofluoroether is more preferably a compound of formula (B-5):         R 21< -O-R 22<      (B-5), wherein R 21< is linear or branched propyl or butyl in which at least one hydrogen atom is replaced by fluorine, and R 22< is methyl or ethyl. The compound of formula (B-5) may be a compound in which R 21< is perfluorobutyl, and R 22< is methyl or ethyl.

[0077] As the aprotic solvent (B), a hydrofluoroether is preferable because it has less environmental impact during use and can be easily distilled off from the polymer.

[0078] The aprotic solvent (B) may have a global warming potential (GWP) of, for example, 600 or less, or 400 or less, preferably 375 or less, more preferably 350 or less, and particularly preferably 0. The lower limit of the global warming potential (GWP) of the aprotic solvent (B) may be 1 or more, or 5 or more.

[0079] In the present composition, the content of the aprotic solvent (B) may be 80 mass% or less based on the mass of the composition, preferably 35-80 mass%, more preferably 35 to < 80 mass%, and particularly preferably 50 to < 80 mass%.Other Components

[0080] The present composition may comprise the starting monomer, an oligomer formed from the starting monomer, a polymerization initiator, impurities derived from the starting material, in addition to the polymer (A3) and the aprotic solvent (B). The amounts of the components contained in the composition can be adjusted, for example, by setting the production conditions for the polymer (A3) (e.g., temperature, time, the kind and amount of starting monomer, the kind and amount of solvent, or the kind and amount of polymerization initiator). The amounts of the components can also be adjusted by purification after the production of the polymer (A3).

[0081] In the present composition, the content of the polymer (A3) may be, for example, 20 mass% or more, 30 mass% or more, greater than 30 mass%, or 31 mass% or more. The content of the polymer (A3) is preferably 20-65 mass%, > 20 to 65 mass%, or 20-50 mass%, more preferably 30-65 mass%, > 30 to 65 mass%, or 31-65 mass%, and particularly preferably 30-50 mass%, > 30 to 50 mass%, or 31-50 mass%.

[0082] In the present composition, the content of the aprotic solvent may be, for example, 80 mass% or less, 70 mass% or less, less than 70 mass%, or 69 mass% or less. The content of the aprotic solvent is preferably 35-80 mass%, 35 to < 80 mass%, or 50-80 mass%, more preferably 35-70 mass%, 35 to < 70 mass%, or 35-69 mass%, and particularly preferably 50-70 mass%, 50 to < 70 mass%, or 50-69 mass%.Composition (A3-2) Comprising Polymer (A3) and Hydrofluoroether_ as Nonperfluoro Aprotic Solvent (B)

[0083] In another aspect of the invention, the present composition is a composition (A3-2) comprising the polymer (A3) and a hydrofluoroether as nonperfluoro aprotic solvent (B). In the composition (A3-2), the polymer (A3) may be dissolved even though the solvent is a nonperfluoro solvent.

[0084] The matters described in the sections other than this section may be applied to the composition (A3-2); however, the concentration of the fluorine-containing polymer (A3) may be less than 20 mass%.Method for Producing Fluorine-Containing Polymer (A3)

[0085] The 3 polymer (A3) is produced by subjecting a monomer to a polymerization reaction in the presence of a polymerization initiator.

[0086] The monomer comprises a monomer (M) corresponding to the structural unit (A3) in the polymer (A3).

[0087] The polymerization reaction is performed in an aprotic solvent (B), which solvent (B) is at least one solvent selected from a hydrofluoroether.

[0088] In the present method, an aprotic solvent (B) in which the content or dissolution amount of fluorine-containing polymer (A) is high can be obtained. Thus, the present method is suitable as a method for producing the present composition.Monomer

[0089] The "monomer (M)" is a monomer corresponding to the structural unit (A3) in the polymer (A3). In addition to the monomer (M), other monomers can be used as monomers. In the present specification, monomers corresponding to structural units that are contained in the polymer (A) and are structural units other than the structural unit (A3) may be referred to as "other monomers."

[0090] Those skilled in the art can understand that a polymerization reaction of a specific monomer yields a polymer (A) containing a structural unit corresponding to the monomer. Thus, those skilled in the art can select a suitable monomer to produce the desired polymer (A).

[0091] For example, the monomers corresponding to the structural units (A3-1) and (A11-1) may be respectively monomers of the formulae (M3-1) and (M11-1) (which may be respectively referred to as "monomer (M3-1)" and "monomer (M11-1)" herein).         CF 2 =CF 2      (M11-1)

[0092] As the monomer (M), one kind of monomer (M) may be used singly, or two or more kinds of monomers (M) may be used in combination. Moreover, the monomer (M) can also be used in combination with other monomers.Aprotic Solvent (B)

[0093] In the present method, the monomer is polymerized in an aprotic solvent (B), which solvent (B) is at least one solvent selected from a hydrofluoroether.Polymerization Initiator

[0094] In the present method, the monomer is polymerized in the presence of a polymerization initiator. The polymerization initiator may be any polymerization initiator that can polymerize the monomer (M), and is, for example, a radical polymerization initiator. The polymerization initiator preferably has a 10-hour half-life temperature within the range of 0-160°C.

[0095] The polymerization initiator preferably contains one or more fluorine atoms since a liquid composition having a high polymer (A3) content can be obtained. The polymerization initiator is more preferably a nonperfluoro polymerization initiator. The nonperfluoro polymerization initiator is a polymerization initiator containing hydrogen and fluorine atoms. Thus, the nonperfluoro polymerization initiator does not include perfluoro compounds.

[0096] The polymerization initiators may be used singly or in a combination of two or more.

[0097] Examples of polymerization initiators include compounds of the following formulas (C1), (C2), and (C3) (which may be respectively referred to as "compound (C1)," "compound (C2)," and "compound (C3)" herein) and inorganic peroxides. The compounds (C1)-(C3) and inorganic peroxides may be used singly or in combination: wherein R 31< and R 32< in formula (C1) and R 33< and R 34< in formula (C2) are the same or different, and each is a group in which at least one fluorine atom of C 3-10 -perfluoroalkyl optionally substituted with perfluorophenyl is replaced by hydrogen, or a group in which at least one fluorine atom of perfluorophenyl optionally substituted with linear or branched C 1-4 -perfluoroalkyl is replaced by hydrogen; and formula (C3): wherein R 35< and R 36< each independently are a group in which at least one fluorine atom of C 1-10 -perfluoroalkyl optionally substituted with perfluorophenyl is replaced by hydrogen, or a group in which at least one fluorine atom of perfluorophenyl optionally substituted with linear or branched C 1-4 -perfluoroalkyl is replaced by hydrogen.

[0098] Preferably, R 31< and R 32< each independently are perfluoropropyl, perfluoroisopropyl, perfluoro-2-phenyl-2-propyl, perfluorobutyl, perfluoro-sec-butyl, perfluoro-tert-butyl, perfluoropentyl, perfluoroisopentyl, perfluoroneopentyl, perfluoro-2-methyl-2-pentyl, perfluoro-2,4,4-trimethyl-2-pentyl, perfluorohexyl, perfluoro-2-methylhexyl, perfluoro-2-ethylhexyl, perfluorocyclohexyl, perfluoro-4-methylcyclohexyl, perfluoro-4-ethylcyclohexyl, perfluoro-4-tert-butylcyclohexyl, perfluoroheptyl, perfluoro-2-heptyl, perfluoro-3-heptyl, perfluorooctyl, perfluoro-2-methyl-2-octyl, perfluorononyl, perfluorodecyl, perfluorophenyl, perfluoro-2-methylphenyl, perfluoro-3-methylphenyl, or perfluoro-4-methylphenyl, in which at least one fluorine atom is replaced by hydrogen.

[0099] In R 31< and R 32< , the number of fluorine atoms replaced by hydrogen is one to the maximum substitutable number (SN max ), preferably three less than SN max to SN max , more preferably two less than SN max to SN max , even more preferably one less than SN max to SN max , and particularly preferably SN max .

[0100] More preferably, R 31< and R 32< each independently are propyl, isopropyl, sec-butyl, 2-ethylhexyl, or 4-tert-butylcyclohexyl.

[0101] Particularly preferably, R 31< and R 32< each independently are propyl or isopropyl.

[0102] Preferred examples of the compound (C1) include di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, bis(4-tert-butylcyclohexyl)peroxydicarbonate, and di-2-ethylhexyl peroxydicarbonate.

[0103] Particularly preferred examples of the compound (C1) include di-n-propyl peroxydicarbonate and diisopropyl peroxydicarbonate.

[0104] Preferably, R 33< and R 34< each independently are perfluoropropyl, perfluoroisopropyl, perfluoro-2-phenyl-2-propyl, perfluorobutyl, perfluoro-sec-butyl, perfluoro-tert-butyl, perfluoropentyl, perfluoroisopentyl, perfluoroneopentyl, perfluoro-2-methyl-2-pentyl, perfluoro-2,4,4-trimethyl-2-pentyl, perfluorohexyl, perfluoro-2-methylhexyl, perfluoro-2-ethylhexyl, perfluorocyclohexyl, perfluoro-4-methylcyclohexyl, perfluoro-4-ethylcyclohexyl, perfluoro-4-tert-butylcyclohexyl, perfluoroheptyl, perfluoro-2-heptyl, perfluoro-3-heptyl, perfluorooctyl, perfluoro-2-methyl-2-octyl, perfluorononyl, perfluorodecyl, perfluorophenyl, perfluoro-2-methylphenyl, perfluoro-3-methylphenyl, or perfluoro-4-methylphenyl, in which at least one fluorine atom is replaced by hydrogen.

[0105] In R 33< and R 34< , the number of fluorine atoms replaced by hydrogen is one to SN max , preferably three less than SN max to SN max , more preferably two less than SN max to SN max , and even more preferably one less than SN max to SN max .

[0106] More preferably, R 33< and R 34< each independently are isopropyl, 2,4,4-trimethylpentyl, ω-hydro-dodecafluorohexyl, ω-hydro-hexadecafluorooctyl, phenyl, or 3-methylphenyl.

[0107] Preferred examples of the compound (C2) include diisobutyryl peroxide, di(3,5,5-trimethylhexanoyl)peroxide, di(ω-hydro-dodecafluoroheptanoyl)peroxide, di(ω-hydro-hexadecafluorononanoyl)peroxide, ω-hydro-dodecafluoroheptanoyl-ω-hydro-hexadecafluorononanoyl-peroxide, benzoyl peroxide, benzoyl m-methylbenzoyl peroxide, and m-toluoyl peroxide.

[0108] Particularly preferred examples of the compound (C2) include diisobutyryl peroxide, di(ω-hydro-dodecafluoroheptanoyl)peroxide, di(ω-hydro-hexadecafluorononanoyl)peroxide, ω-hydro-dodecafluoroheptanoyl-ω-hydro-hexadecafluorononanoyl-peroxide, and benzoyl peroxide.

[0109] Preferably, R 35< and R 36< each independently are perfluoromethyl, perfluoroethyl, perfluoropropyl, perfluoroisopropyl, perfluoro-2-phenyl-2-propyl, perfluorobutyl, perfluoro-sec-butyl, perfluoro-tert-butyl, perfluoropentyl, perfluoroisopentyl, perfluoroneopentyl, perfluoro-2-methyl-2-pentyl, perfluoro-2,4,4-trimethyl-2-pentyl, perfluorohexyl, perfluoro-2-methylhexyl, perfluoro-2-ethylhexyl, perfluorocyclohexyl, perfluoro-4-methylcyclohexyl, perfluoro-4-ethylcyclohexyl, perfluoro-4-tert-butylcyclohexyl, perfluoroheptyl, perfluoro-2-heptyl, perfluoro-3-heptyl, perfluorooctyl, perfluoro-2-methyl-2-octyl, perfluorononyl, perfluorodecyl, perfluorophenyl, perfluoro-2-methylphenyl, perfluoro-3-methylphenyl, or perfluoro-4-methylphenyl, in which at least one fluorine atom is replaced by hydrogen.

[0110] In R 35< and R 36< , the number of fluorine atoms replaced by hydrogen is one to SN max , preferably three less than SN max to SN max , more preferably two less than SN max to SN max , even more preferably one less than SN max to SN max , and particularly preferably SN max .

[0111] More preferably, R 35< and R 36< each independently are isopropyl, 2-phenyl-2-propyl, tert-butyl, 2-methyl-2-pentyl, 2,4,4-trimethyl-2-pentyl, 2-heptyl, 2-methyl-2-octyl, phenyl, or 3-methylphenyl.

[0112] Preferred examples of the compound (C3) include tert-butyl peroxyneodecanoate, tert-butyl peroxypivalate, tert-hexyl peroxypivalate, OO-tert-butyl O-isopropyl peroxycarbonate, and tert-butyl peroxyacetate.

[0113] Particularly preferred examples of the compound (C3) include tert-butyl peroxypivalate and tert-hexyl peroxypivalate.

[0114] Preferred examples of inorganic peroxides include ammonium salts, sodium salts, and potassium salts of persulfuric acid, perboric acid, perchloric acid, perphosphoric acid, percarbonic acid, and permanganic acid.

[0115] Particularly preferred examples of inorganic peroxides include ammonium persulfate, sodium persulfate, and potassium persulfate.

[0116] The inorganic peroxides may be used singly or in a combination of two or more. The inorganic peroxides may be used in combination with reducing agents, such as sulfite-based reducing agents (e.g., sodium dithionite) and sulfite reducing agents (e.g., sodium sulfite, ammonium sulfite, and sodium hydrogen sulfite).

[0117] Preferred examples of polymerization initiators include di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, diisobutyryl peroxide, di(ω-hydro-dodecafluoroheptanoyl)peroxide, di(ω-hydro-hexadecafluorononanoyl)peroxide, ω-hydro-dodecafluoroheptanoyl-ω-hydro-hexadecafluorononanoyl-peroxide, benzoyl peroxide, tert-butyl peroxypivalate, tert-hexyl peroxypivalate, ammonium persulfate, sodium persulfate, and potassium persulfate.

[0118] Particularly preferred examples of polymerization initiators include di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, diisobutyryl peroxide, di(ω-hydro-dodecafluoroheptanoyl)peroxide, benzoyl peroxide, tert-butyl peroxypivalate, tert-hexyl peroxypivalate, and ammonium persulfate.

[0119] The amount of monomer (M) used in the polymerization reaction can be appropriately determined according to, for example, the proportion of the structural unit corresponding to the monomer (M) in the desired polymer (A3). For example, the amount of monomer (M) is 50 mol% or more, preferably 80 mol% or more, even more preferably 90 mol% or more, and particularly preferably 100 mol%, based on the total number of moles of all of the starting monomers.

[0120] When one or more other monomers are used in addition to the monomer (M), the amount of the other monomers can be appropriately determined according to, for example, the proportion of the structural units corresponding to the other monomers in the desired polymer (A3). For example, the amount of the other monomers is 50 mol% or less, preferably 20 mol% or less, more preferably 10 mol% or less, and particularly preferably 0 mol%, based on the total number of moles of all of the starting monomers.

[0121] The amount of aprotic solvent (B) used in the polymerization reaction may be within the range of 20-300 mass%, preferably 35-250 mass%, and more preferably 50-300 mass%, based on the amount of monomer (M) taken as 100 mass%. The amount of polymerization initiator used in the polymerization reaction may be, for example, within the range of 0.0001-0.05 g, preferably 0.0001-0.01 g, and more preferably 0.0005-0.008 g, per gram of all monomers (i.e., the total amount of monomer (M) and other monomers) to be subjected to the reaction.

[0122] The temperature of the polymerization reaction may be, for example, within the range of -10°C to 160°C, preferably 0-160°C, and more preferably 0-100°C.

[0123] The polymerization reaction may be performed at a temperature that is not greater than 20°C higher than the boiling point of the monomer (M) corresponding to the structural unit (A3) of the polymer (A3) or the boiling point of the aprotic solvent, whichever is lower, and that is not greater than 20°C higher than the 10-hour half-life temperature of the polymerization initiator. In this case, the lower limit of the temperature may be, for example, -10°C, and preferably 0°C.

[0124] The reaction time of the polymerization reaction may be preferably within the range of 0.5-72 h, more preferably 1-48 h, and even more preferably 3-30 h.

[0125] The polymerization reaction can be performed in the presence or absence of an inert gas (e.g., nitrogen gas), and preferably in the presence of an inert gas.

[0126] The polymerization reaction can be performed under reduced pressure, atmospheric pressure, or increased pressure.

[0127] The polymerization reaction can be performed by adding the monomer to the aprotic solvent (B) containing the polymerization initiator. The polymerization reaction can also be performed by adding the polymerization initiator to the aprotic solvent (B) containing the monomer.

[0128] The polymer (A3) produced in the polymerization reaction can be isolated or purified, if desired, by a conventional method, such as extraction, dissolution, concentration, filtration, precipitation, dehydration, adsorption, or chromatography, or a combination of these methods.

[0129] The polymer (A3) generally has low solubility in the aprotic solvent (B). It has been thus difficult to form e.g. a coating film that contains a high concentration of the polymer (A3). However, the present method makes it possible to produce a liquid in which the polymer (A3) is dissolved at a high concentration in the aprotic solvent (B). For example, the present method makes it possible to produce a liquid in which the amount of polymer (A) dissolved is 20 mass% or more, preferably 20-65 mass%, more preferably > 20 to 65 mass%, and particularly preferably > 20 to 50 mass%, based on the total mass of the polymer (A3) and the aprotic solvent (B).

[0130] The polymer (A3) may be purified and isolated from the liquid. In another embodiment, the liquid may be used as is for applications in which the polymer (A3) is required.

[0131] The amount of polymer (A3) dissolved may be, for example, 20 mass% or more, 30 mass% or more, > 30 mass%, or 31 mass% or more, preferably 20-65 mass%, > 20 to 65 mass%, or 20-50 mass%, more preferably 30-65 mass%, > 30 to 65 mass%, or 31-65 mass%, and particularly preferably 30-50 mass%, > 30 to 50 mass%, or 31-50 mass%, based on the total mass of the fluorine-containing polymer (A3) and the aprotic solvent (B).

[0132] When the aprotic solvent is a hydrofluoroether as nonperfluoro solvent, the amount of polymer (A3) dissolved may be less than 20 mass% in addition to the above ranges, such as 1 mass% or more, 5 mass% or more, 10 mass% or more, 15 mass% or more, 20 mass% or more, 30 mass% or more, > 30 mass%, or 31 mass% or more, preferably 20-65 mass%, > 20 to 65 mass%, or 20-50 mass%, more preferably 30-65 mass%, > 30 to 65 mass%, or 31-65 mass%, and particularly preferably 30-50 mass%, > 30 to 50 mass%, or 31-50 mass%.

[0133] The polymer (A3) produced by the present method can be used in conventionally known applications of the polymer (A3). Examples of the applications include a pellicle film formed on a photomask used in the lithography process.Examples

[0134] An embodiment of the present invention is described in more detail below with reference to Examples.

[0135] The symbols and abbreviations in the Examples are used with the following meanings. PMMA: polymethyl methacrylate Initiator solution (1): a methanol solution containing 50 mass% di-n-propyl peroxydicarbonate (10-hour half-life temperature: 40°C) Initiator solution (2): a perfluorohexane solution containing 7 mass% di(ω-hydro-dodecafluoroheptanoyl)peroxide (10-hour half-life temperature: 15°C) Fluorine-containing polymer (A3-1): a polymer comprising the structural unit (A3-1) GPC Analysis Method

[0136] Sample Preparation Method

[0137] A polymer is dissolved in perfluorobenzene to prepare a 2 wt% polymer solution, and the polymer solution is passed through a membrane filter (0.22 µm) to obtain a sample solution.Measurement method

[0138] Standard sample for measurement of molecular weight: PMMA Detection method: RI (differential refractometer) Criteria for Polymer Solubility

[0139] Whether the polymer in each composition was dissolved was determined as follows.

[0140] Each of prepared compositions was visually checked. When no undissolved polymer was observed and the entire composition flowed uniformly at room temperature, it was determined that the polymer was dissolved.Example 1: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0141] The monomer (M3-1) (10 g), methyl nonafluorobutyl ether (15 g) as a solvent, and the initiator solution (1) (0.017 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the mixture was heated such that the internal temperature was maintained at 40°C, thereby producing a composition containing 36 wt% fluorine-containing polymer (A3-1) (8.5 g; Mw: 273268). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0142] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer (the "impurities" means e.g. HF, 4,4,5-trifluoro-2,5-bis(trifluoromethyl)-1,3-dioxolane, 2-(difluoromethyl)-2,4,4,5-tetrafluoro-5-(trifluoromethyl)-1,3-dioxolane, and 4,4,5-trifluoro-2,5-bis(trifluoromethyl)-1,3-dioxolane-2-carboxylic acid; the same applies to other Examples) by vacuum drying at 120°C after the completion of the polymerization reaction.Example 2: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0143] The monomer (M3-1) (10 g), methyl nonafluorobutyl ether (20 g) as a solvent, and the initiator solution (1) (0.030 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the mixture was heated such that the internal temperature was maintained at 40°C, thereby producing a composition containing 31 wt% fluorine-containing polymer (A3-1) (8.8 g; Mw: 143514). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0144] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 3: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0145] The monomer (M3-1) (10 g), methyl nonafluorobutyl ether (20 g) as a solvent, and the initiator solution (1) (0.041 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the mixture was heated such that the internal temperature was maintained at 40°C, thereby producing a composition containing 31 wt% fluorine-containing polymer (A3-1) (9.1 g; Mw: 107403). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0146] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 4: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0147] The monomer (M3-1) (10 g), methyl nonafluorobutyl ether (30 g) as a solvent, and the initiator solution (1) (0.017 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the mixture was heated such that the internal temperature was maintained at 40°C, thereby producing a composition containing 23 wt% fluorine-containing polymer (A3-1) (9.0 g; Mw: 147399). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0148] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 5: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0149] The monomer (M3-1) (10 g), methyl nonafluorobutyl ether (60 g) as a solvent, and the initiator solution (1) (0.013 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the mixture was heated such that the internal temperature was maintained at 40°C, thereby producing a composition containing 11 wt% fluorine-containing polymer (A3-1) (7.4 g; Mw: 99273). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0150] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 6: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0151] The monomer (M3-1) (10 g), methyl nonafluorobutyl ether (80 g) as a solvent, and the initiator solution (1) (0.013 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the mixture was heated such that the internal temperature was maintained at 40°C, thereby producing a composition containing 7 wt% fluorine-containing polymer (A3-1) (6.1 g; Mw: 82991). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0152] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 7: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0153] The monomer (M3-1) (10 g), ethyl nonafluorobutyl ether (boiling point: 76°C) (5 g) as a solvent, and the initiator solution (1) (0.020 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the mixture was heated such that the internal temperature was maintained at 40°C, thereby producing a composition containing 64 wt% fluorine-containing polymer (A3-1) (8.7 g; Mw: 114791). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0154] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 8: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0155] The monomer (M3-1) (10 g), ethyl nonafluorobutyl ether (12 g) as a solvent, and the initiator solution (1) (0.015 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the mixture was heated such that the internal temperature was maintained at 40°C, thereby producing a composition containing 44 wt% fluorine-containing polymer (A3-1) (9.3 g; Mw: 150609). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0156] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 9: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0157] The monomer (M3-1) (10 g), ethyl nonafluorobutyl ether (12 g) as a solvent, and the initiator solution (1) (0.035 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the mixture was heated such that the internal temperature was maintained at 40°C, thereby producing a composition containing 45 wt% fluorine-containing polymer (A3-1) (9.7 g; Mw: 127901). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0158] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 10: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0159] The monomer (M3-1) (10 g), ethyl nonafluorobutyl ether (12 g) as a solvent, and the initiator solution (1) (0.054 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the mixture was heated such that the internal temperature was maintained at 40°C, thereby producing a composition containing 45 wt% fluorine-containing polymer (A3-1) (9.7 g; Mw: 113366). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0160] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 11: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0161] The monomer (M3-1) (10 g), ethyl nonafluorobutyl ether (20 g) as a solvent, and the initiator solution (1) (0.041 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the mixture was heated such that the internal temperature was maintained at 40°C, thereby producing a composition containing 31 wt% fluorine-containing polymer (A3-1) (9.0 g; Mw: 97533). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0162] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 12: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0163] The monomer (M3-1) (10 g), ethyl nonafluorobutyl ether (30 g) as a solvent, and the initiator solution (1) (0.041 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the mixture was heated such that the internal temperature was maintained at 40°C, thereby producing a composition containing 22 wt% fluorine-containing polymer (A3-1) (8.6 g; Mw: 63291). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0164] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 13: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0165] The monomer (M3-1) (10 g), ethyl nonafluorobutyl ether (60 g) as a solvent, and the initiator solution (1) (0.020 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the mixture was heated such that the internal temperature was maintained at 40°C, thereby producing a composition containing 10 wt% fluorine-containing polymer (A3-1) (7.0 g; Mw: 73154). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0166] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 14: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0167] The monomer (M3-1) (10 g), ethyl nonafluorobutyl ether (80 g) as a solvent, and the initiator solution (1) (0.020 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the mixture was heated such that the internal temperature was maintained at 40°C, thereby producing a composition containing 6 wt% fluorine-containing polymer (A3-1) (5.5 g; Mw: 52838). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0168] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 15: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0169] The monomer (M3-1) (10 g), 3-methoxytridecafluorohexane (boiling point: 98°C) (20 g) as a solvent, and the initiator solution (1) (0.034 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the mixture was heated such that the internal temperature was maintained at 40°C, thereby producing a composition containing 31 wt% fluorine-containing polymer (A3-1) (8.9 g; Mw: 131202). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0170] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 16: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0171] The monomer (M3-1) (10 g), perfluorotripropylamine (boiling point: 128°C) (15 g) as a solvent, and the initiator solution (1) (0.052 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the mixture was heated such that the internal temperature was maintained at 40°C, thereby producing a composition containing 37 wt% fluorine-containing polymer (A3-1) (8.9 g; Mw: 158427). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0172] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 17: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0173] The monomer (M3-1) (10 g), perfluorotripropylamine (10 g) as a solvent, and the initiator solution (1) (0.052 g) were placed in a 20-mL glass container, and then a polymerization reaction was performed for 20 hours while the mixture was heated such that the internal temperature was maintained at 40°C, thereby producing a composition containing 49 wt% fluorine-containing polymer (A3-1) (9.5 g; Mw: 213475). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0174] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 18: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0175] The monomer (M3-1) (10 g), perfluoro-5-butyltetrahydrofuran (boiling point: 102°C) (15 g) as a solvent, and the initiator solution (1) (0.025 g) were placed in a 20-mL glass container, and then a polymerization reaction was performed for 20 hours while the mixture was heated such that the internal temperature was maintained at 40°C, thereby producing a composition containing 38 wt% fluorine-containing polymer (A3-1) (9.0 g; Mw: 158992). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0176] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 19: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0177] The monomer (M3-1) (10 g), perfluorohexane (boiling point: 56°C) (10 g) as a solvent, and the initiator solution (1) (0.025 g) were placed in a 20-mL glass container, and then a polymerization reaction was performed for 20 hours while the mixture was heated such that the internal temperature was maintained at 40°C, thereby producing a composition containing 45 wt% fluorine-containing polymer (A3-1) (8.2 g; Mw: 128122). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0178] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 20: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0179] The monomer (M3-1) (10 g), perfluorobenzene (boiling point: 80°C) (10 g) as a solvent, and the initiator solution (1) (0.031 g) were placed in a 20-mL glass container, and then a polymerization reaction was performed for 20 hours while the mixture was heated such that the internal temperature was maintained at 40°C, thereby producing a composition containing 32 wt% fluorine-containing polymer (A3-1) (4.7 g; Mw: 45323). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0180] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 21: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0181] The monomer (M3-1) (10 g), methyl nonafluorobutyl ether (20 g) as a solvent, and the initiator solution (2) (0.010 g) were placed in a 20-mL glass container, and then a polymerization reaction was performed for 20 hours while the internal temperature was adjusted to 15°C, thereby producing a composition containing 32 wt% fluorine-containing polymer (A3-1) (9.3 g; Mw: 217533). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0182] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 22: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0183] The monomer (M3-1) (10 g), methyl nonafluorobutyl ether (20 g) as a solvent, and the initiator solution (2) (0.022 g) were placed in a 20-mL glass container, and then a polymerization reaction was performed for 20 hours while the internal temperature was adjusted to 15°C, thereby producing a composition containing 32 wt% fluorine-containing polymer (A3-1) (9.6 g; Mw: 109215). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0184] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 23: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0185] The monomer (M3-1) (10 g), perfluorotripropylamine (15 g) as a solvent, and the initiator solution (2) (0.017 g) were placed in a 20-mL glass container, and then a polymerization reaction was performed for 20 hours while the internal temperature was adjusted to 15°C, thereby producing a composition containing 36 wt% fluorine-containing polymer (A3-1) (8.6 g; Mw: 163900). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0186] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 24: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0187] The monomer (M3-1) (10 g), 1,1,1,2,3,3-hexafluoropropyl methyl ether (15 g) as a solvent, and the initiator solution (1) (0.041 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the internal temperature was adjusted to 40°C, thereby producing a composition containing 37 wt% fluorine-containing polymer (A3-1) (9.3 g; Mw: 99264). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0188] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 25: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0189] The monomer (M3-1) (10 g), 1,1,1,2,3,3-hexafluoropropyl methyl ether (20 g) as a solvent, and the initiator solution (1) (0.037 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the internal temperature was adjusted to 40°C, thereby producing a composition containing 30 wt% fluorine-containing polymer (A3-1) (8.9 g; Mw: 80192). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0190] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 26: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0191] The monomer (M3-1) (10 g), 1,1,1,2,3,3-hexafluoropropyl methyl ether (20 g) as a solvent, and the initiator solution (2) (0.025 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the internal temperature was adjusted to 15°C, thereby producing a composition containing 31 wt% fluorine-containing polymer (A3-1) (9.4 g; Mw: 102931). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0192] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 27: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0193] The monomer (M3-1) (10 g), 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (15 g) as a solvent, and the initiator solution (1) (0.040 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the internal temperature was adjusted to 40°C, thereby producing a composition containing 36 wt% fluorine-containing polymer (A3-1) (8.9 g; Mw: 110481). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0194] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 28: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0195] The monomer (M3-1) (10 g), 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (20 g) as a solvent, and the initiator solution (1) (0.034 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the internal temperature was adjusted to 40°C, thereby producing a composition containing 29 wt% fluorine-containing polymer (A3-1) (8.6 g; Mw: 97423). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0196] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 29: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0197] The monomer (M3-1) (10 g), 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (20 g) as a solvent, and the initiator solution (2) (0.023 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the internal temperature was adjusted to 15°C, thereby producing a composition containing 31 wt% fluorine-containing polymer (A3-1) (9.2 g; Mw: 126345). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0198] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 30: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0199] The monomer (M3-1) (10 g), 1,1,1,3,3,3-hexafluoro-2-methoxypropane (15 g) as a solvent, and the initiator solution (1) (0.040 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the internal temperature was adjusted to 40°C, thereby producing a composition containing 34 wt% fluorine-containing polymer (A3-1) (8.4 g; Mw: 78016). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0200] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 31: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0201] The monomer (M3-1) (10 g), 1,1,1,3,3,3-hexafluoro-2-methoxypropane (20 g) as a solvent, and the initiator solution (1) (0.036 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the internal temperature was adjusted to 40°C, thereby producing a composition containing 26 wt% fluorine-containing polymer (A3-1) (7.9 g; Mw: 70127). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0202] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.Example 32: Production of Composition Comprising Structural Unit (A3-1) as Main Component

[0203] The monomer (M3-1) (10 g), 1,1,1,3,3,3-hexafluoro-2-methoxypropane (20 g) as a solvent, and the initiator solution (2) (0.022 g) were placed in a 50-mL glass container, and then a polymerization reaction was performed for 20 hours while the internal temperature was adjusted to 15°C, thereby producing a composition containing 30 wt% fluorine-containing polymer (A3-1) (8.9 g; Mw: 84829). The solubility of the polymer was visually determined, and it was confirmed that the obtained solution was completely homogeneous.

[0204] The weight of the polymer in the composition was measured by distilling off the unreacted starting material, the solvent, the initiator residue, and the impurities contained in a trace amount in the monomer by vacuum drying at 120°C after the completion of the polymerization reaction.

[0205] Tables 1 and 2 show the results obtained in the Examples. Table 1EntryMonomerInitiator solutionSolventPolymerMethod for preparing compositionSolubility (visual evaluation)Polymer concentration in compositionKind9Kind9StructureGWP9Structural unitPolymerization method9Mwwt%Ex. 1M3-110(1)0.017C 4 F 9 OCH 3 29715A3-1Solution polymerization8.5273268Polymerization○36%Ex. 2M3-110(1)0.030C 4 F 9 OCH 3 29720A3-1Solution polymerization8.8143514Polymerization○31%Ex. 3M3-110(1)0.041C 4 F 9 OCH 3 29720A3-1Solution polymerization9.1107403Polymerization○31%Ex. 4M3-110(1)0.017C 4 F 9 OCH 3 29730A3-1Solution polymerization9.0147399Polymerization○23%Ex. 5M3-110(1)0.013C 4 F 9 OCH 3 29760A3-1Solution polymerization7.499273Polymerization○11%Ex. 6M3-110(1)0.013C 4 F 9 OCH 3 29780A3-1Solution polymerization6.182991Polymerization○7%Ex. 7M3-110(1)0.020C 4 F 9 OC 2 H 5 575A3-1Solution polymerization8.7114791Polymerization○64%Ex. 8M3-110(1)0.015C 4 F 9 OC 2 H 5 5712A3-1Solution polymerization9.3150609Polymerization○44%Ex. 9M3-110(1)0.035C 4 F 9 OC 2 H 5 5712A3-1Solution polymerization97127901Polymerization○45%Ex. 10M3-110(1)0.054C 4 F 9 OC 2 H 5 5712A3-1Solution polymerization97113366Polymerization○45%Ex. 11M3-110(1)0.041C 4 F 9 OC 2 H 5 5720A3-1Solution polymerization9.097533Polymerization○31%Ex. 12M3-110(1)0.041C 4 F 9 OC 2 H 5 5730A3-1Solution polymerization8.663291Polymerization○22%Ex. 13M3-110(1)0.020C 4 F 9 OC 2 H 5 5760A3-1Solution polymerization7.073154Polymerization○10%Ex. 14M3-110(1)0.020C 4 F 9 OC 2 H 5 5780A3-1Solution polymerization5.552838Polymerization○6%Ex. 15M3-110(1)0.034C 2 F 5 CF(OCH 3 )C 3 F 7 31020A3-1Solution polymerization8.9131202Polymerization○31% Table 2 EntryMonomerInitiator solutionSolventPolymerMethod for preparing compositionSolubility (visual evaluation)Polymer concentration in compositionKind9Kind9StructureGWP9Structural unitPolymerization method9Mwwt%Ex. 16M3-110(1)0.052(CF 3 CF 2 CF 2 ) 3 N890015A3-1Solution polymerization8.9158427Polymerization○37%Ex. 17M3-110(1)0.052(CF 3 CF 2 CF 2 ) 3 N890010A3-1Solution polymerization9.5213475Polymerization○49%Ex. 18M3-110(1)0.025Perfluoro-5-butyltetrahydrofuran>1000015A3-1Solution polymerization9.0158992Polymerization○38%Ex. 19M3-110(1)0.025Perfluorohexane740010A3-1Solution polymerization8.2128122Polymerization○45%Ex. 20M3-110(1)0.031Perfluorobenzene1510A3-1Solution polymerization4.745323Polymerization○32%Ex. 21M3-110(2)0.010C 4 F 9 OCH 3 29720A3-1Solution polymerization9.3217533Polymerization○32%Ex. 22M3-110(2)0.022C 4 F 9 OCH 3 29720A3-1Solution polymerization9.6109215Polymerization○32%Ex. 23M3-110(2)0.017(CF 3 CF 2 CF 2 ) 3 N890015A3-1Solution polymerization8.6163900Polymerization○36%Ex. 24M3-110(1)0.041CF 3 CHFCF 2 OCH 3 10115A3-1Solution polymerization9.399264Polymerization○37%Ex. 25M3-110(1)0.037CF 3 CHFCF 2 OCH 3 10120A3-1Solution polymerization8.980192Polymerization○30%Ex. 26M3-110(2)0.025CF 3 CHFCF 2 OCH 3 10120A3-1Solution polymerization9.4102931Polymerization○31%Ex. 27M3-110(1)0.040CHF 2 CF 2 OCH 2 CF 3 58015A3-1Solution polymerization8.9110481Polymerization○36%Ex. 28M3-110(1)0.034CHF 2 CF 2 OCH 2 CF 3 58020A3-1Solution polymerization8.697423Polymerization○29%Ex. 29M3-110(2)0.023CHF 2 CF 2 OCH 2 CF 3 58020A3-1Solution polymerization9.2126345Polymerization○31%Ex. 30M3-110(1)0.040(CF 3 ) 2 CHOCH 3 2715A3-1Solution polymerization8.478016Polymerization○34%Ex. 31M3-110(1)0.036(CF 3 ) 2 CHOCH 3 2720A3-1Solution polymerization7970127Polymerization○26%Ex. 32M3-110(2)0.022(CF 3 ) 2 CHOCH 3 2720A3-1Solution polymerization8.984829Polymerization○30%

Claims

1. A composition comprising: (1) an aprotic solvent (B) which is at least one of a perfluorotrialkylamine, a perfluoroalkane, a perfluorocyclic ether, and a hydrofluoroether; and (2) dissolved in the aprotic solvent (B), ≥ 20 mass%, based on the mass of the composition, of a polymer (A3) comprising, based on all structural units in the polymer (A3), ≥ 50 mol% of structural units of the formula (A3): wherein R6-R9 each independently are F, C1-5-perfluoroalkyl, or C1-5-perfluoroalkoxy.

2. The composition of claim 1, which contains 20-65 mass%, preferably > 20 to 65 mass%, of the polymer (A3) dissolved in the aprotic solvent (B), based on the mass of the composition.

3. The composition of claim 1 or 2, wherein the aprotic solvent (B) is a hydrofluoroether, and preferably at least one hydrofluoroether selected from (CF3)2CHOCH3, (CF3)2CFOCH3, CF3CHFCF2OCH3, CF3CHFCF2OCF3 and compounds of the formulae (B-1) to (B-4):         F(CF2)pO(CH2)qH     (B-1)         H(CF2)pO(CF2)qF     (B-2)         H(CF2)pO(CH2)qH     (B-3)         X(CF2)pCH2O(CF2)qH     (B-4) wherein p is an integer of 1-6, q is an integer of 1-4 and X is H or F; or a compound of the formula R21-O-R22 (B-5), wherein R21 is linear or branched fluoropropyl or fluorobutyl, and R22 is methyl or ethyl.

4. The composition of any of claims 1-3, wherein the aprotic solvent (B) has a global warming potential (GWP) of ≤ 400.

5. The composition of any of claims 1-4, wherein the structural unit of formula (A3) is a structural unit of the formula (A3-1):

6. The composition of any of claims 1-5, wherein the proportion of structural units of the formula (A3) in the polymer (A3) is ≥ 80 mol%.

7. The composition of any of claims 1-6, wherein the polymer (A3) has a mass average molecular weight of 5,000-1,000,000, preferably 40,000-500,000, determined by a gel permeation chromatography (GPC) using a solution of 2 wt.% polymer in perfluorobenzene and passed through a membrane filter (0.22 µm) as sample solution and PMMA as standard, and using a differential refractometry as detection method.

8. A method for producing a polymer (A3) comprising, based on all structural units in the polymer (A3), ≥ 50 mol% of structural units of the formula (A3) wherein R6-R9 each independently are F, C1-5-perfluoroalkyl, or C1-5-perfluoroalkoxy, by subjecting, in the presence of a polymerization initiator, a monomer comprising a monomer (M) corresponding to the structural unit (A3) in the polymer (A) to polymerization reaction in at least one aprotic solvent (B), which solvent (B) is a hydrofluoroether, wherein the polymer (A3) is dissolved in the solvent (B), and the amount of the polymer (A3) dissolved in the solvent (B) is ≥ 20 mass% based on the total mass of the polymer (A3) and the solvent (B).

9. The method of claim 8, wherein the polymerization initiator has a 10-hour half-life temperature of 0-160°C; and the polymerization reaction is performed in the aprotic solvent (B) at a temperature ≤ 20°C higher than (i) the boiling point of the monomer (M) or of the aprotic solvent, whichever is lower, and (ii) the 10-hour half-life temperature of the polymerization initiator.

10. The method of claim 8 or 9, wherein the polymerization initiator is a nonperfluoro polymerization initiator, preferably at least one compound selected from inorganic peroxides and compounds of the formulae (C1)-(C3): wherein R31-R34 each independently are a group in which at least one F of C3-10-perfluoroalkyl optionally substituted with perfluorophenyl is replaced by H, or a group in which at least one F of perfluorophenyl optionally substituted with linear or branched C1-4-perfluoroalkyl is replaced by H; wherein R35 and R36 each independently are a group in which at least one F of C1-10-perfluoroalkyl optionally substituted with perfluorophenyl is replaced by H, or a group in which at least one F of perfluorophenyl optionally substituted with linear or branched C1-4-perfluoroalkyl is replaced by H.

11. The method of any of claims 8-10, wherein the aprotic solvent (B) is at least one hydrofluoroether selected from (CF3)2CHOCH3, (CF3)2CFOCH3, CF3CHFCF2OCH3, CF3CHFCF2OCF3 and compounds of the formulae (B-1) to (B-4):         F(CF2)pO(CH2)qH     (B-1)         H(CF2)pO(CF2)qF     (B-2)         H(CF2)pO(CH2)qH     (B-3)         X(CF2)pCH2O(CF2)qH     (B-4) wherein p is an integer of 1-6, q is an integer of 1-4 and X is H or F; or is a compound of the formula R21-O-R22 (B-5), wherein R21 is linear or branched fluoropropyl or fluorobutyl, and R22 is methyl or ethyl.

12. The method of any of claims 8-11, wherein the aprotic solvent (B) has a global warming potential (GWP) of ≤ 400.

13. The method of any of claims 8-12, wherein the amount of the aprotic solvent (B) in the polymerization reaction is 20-300 mass%, preferably 50-200 mass%, based on the mass of the monomer (M).

14. The method of any of claims 8-13, wherein the polymer (A3) comprises, as the main component, a structural unit of the formula (A3-1):

15. The method of any of claims 8-14, wherein the polymer (A3) has a mass average molecular weight of 5,000-1,000,000, preferably 40,000-500,000, determined by a gel permeation chromatography (GPC) using a solution of 2 wt.% polymer in perfluorobenzene and passed through a membrane filter (0.22 µm) as sample solution and PMMA as standard, and using a differential refractometry as detection method.