JP2014148670A - Emulsifier for emulsion polymerization and method for producing fluoropolymer using the same - Google Patents

Abstract

[PROBLEMS] To carry out emulsion polymerization of a fluoropolymer with less toxicity and bioaccumulation as compared with the use of perfluoroctanic acid (PFOA) ammonium salt as an emulsifier, and with a small amount of water added to an aqueous medium. An emulsifier for emulsion polymerization capable of lowering the surface tension is provided.
A heteroatom-containing perfluoroalkyl organic acid salt in which two or more linear or branched perfluoroalkyl groups having 1 to 6 carbon atoms are chemically linked with nitrogen or oxygen is used as an emulsifier for emulsion polymerization. Use.
[Selection figure] None

Description

  The present invention relates to an emulsifier for emulsion polymerization and a method for producing a fluoropolymer using the same.

  Fluoropolymers typified by polytetrafluoroethylene (PTFE) are chemically stable and excellent in heat resistance and chemical resistance, and thus are used in various fields as coating materials and processing materials.

  Further, the fluoropolymer is usually produced by emulsion polymerization in an aqueous solution. In emulsion polymerization, a fluorosurfactant is used as an emulsifier (also referred to as an emulsion polymerization agent).

  By the way, emulsion polymerization of a fluoropolymer is usually performed by polymerizing a fluoroolefin (monomer) in the presence of a polymerization initiator in an aqueous medium. In this case, the emulsifier plays an extremely important role in polymerization, such as micelle formation as a polymerization field, monomer emulsifying action, and polymer dispersion stabilizing action, and is indispensable for obtaining a desired polymer. It is.

  As such a fluorosurfactant (that is, an emulsifier), perfluoroctanic acid (PFOA) ammonium salt is known (Patent Documents 1 and 2). However, in recent years, it has been clarified that a compound having a linear perfluoroalkyl group having 7 or more carbon atoms has high toxicity and bioaccumulation, and there has been a problem that its use is being restricted. Therefore, studies have been made to develop a fluorosurfactant that is an alternative material for PFOA.

  By the way, one of the characteristics required for an emulsifier for emulsion polymerization is that the surface tension of water is reduced with a smaller addition amount. When the fluoropolymer is produced by emulsion polymerization, if the amount of the emulsifier added to the aqueous medium is increased, the polymerization process may be adversely affected. Moreover, an emulsifier remains in the polymer to be produced, and as a result, various physical properties of the polymer such as water resistance may be deteriorated. Furthermore, if the emulsifier remains in the generated fluoropolymer, it is discharged to the environment as it is, and there is a concern about the influence on the environment.

  Patent Document 3 discloses a bis (perfluorobutanesulfonyl) imide salt as an alternative material for PFOA. This bis (perfluorobutanesulfonyl) imide salt is disclosed to exhibit properties that exceed PFOA in terms of surface tension. However, when a fluoropolymer is produced by emulsion polymerization, when a bis (perfluorobutanesulfonyl) imide salt is used as an emulsifier, the amount of the emulsifier added to the aqueous medium has not yet been sufficiently reduced. .

  Therefore, a fluorosurfactant capable of lowering the surface tension of water with a smaller addition amount than the above bis (perfluorobutanesulfonyl) imide salt is desired as an emulsifier when producing a fluoropolymer by emulsion polymerization. It was the actual situation.

US Pat. No. 3,391,099 JP 61-207413 A Japanese Patent No. 4080998

  The present invention has been made in view of the above circumstances, and is an emulsifier for emulsion polymerization capable of reducing the surface tension of water with a small addition amount with respect to an aqueous medium, and a method for producing a fluoropolymer using the same It is an issue to provide.

上記式（１）中に示すＲｆ^１及びＲｆ^２は、それぞれ同一または互いに異なる炭素数１〜６のペルフルオロアルキル基であって、直鎖状又は分岐状であってもよい。また、上記Ｒｆ^１及びＲｆ^２は、直接結合して環状を形成していても良いし、酸素原子または窒素原子を介して結合し、複素環を形成していてもよい。
Ｒｆ^３は、炭素数１〜６のペルフルオロアルキレン基であって、直鎖状又は分岐状であってもよい。
Ｘは、ＣＯ_２又はＳＯ_３である。
[２] 前記アニオンは、窒素原子を有するペルフルオロ複素環を有する、下記式（２）で表されるアニオンである、前項１に記載の乳化重合用乳化剤。

上記式（２）中に示すＲｆ^４、Ｒｆ^５及びＲｆ^６は、それぞれ同一又は互いに異なる炭素数１〜６のペルフルオロアルキレン基であって、直鎖状又は分岐状であってもよい。
Ｙは、酸素原子、窒素原子又はＣＦ_２基である。
Ｘは、ＣＯ_２又はＳＯ_３である。
[３] 前記アニオンは、下記式（３）で表されるアニオンである、前項１に記載の乳化重合用乳化剤。

上記式（３）中に示すｍ，ｎはそれぞれ同一又は互いに異なる１〜６の整数である。
Ｒｆ^７は、炭素数１〜６のペルフルオロアルキレン基であって、直鎖状又は分岐状であってもよい。
Ｘは、ＣＯ_２又はＳＯ_３である。
[４] 前記アニオンは、下記式（４）〜（２７）で表されるアニオンからなる群から選択されるアニオンである、前項１に記載の乳化重合用乳化剤。

[５] 前記アニオンは、下記式（２８）〜（４３）で表されるアニオンからなる群から選択されるアニオンである、前項１に記載の乳化重合用乳化剤。

[６] （Ｃ_４Ｆ_９）_２ＮＣＦ_２ＣＦ_２ＣＯ_２ ⁻Ｒ^１Ｒ^２Ｒ^３Ｒ^４Ｎ^＋，（Ｃ_４Ｆ_９）_２ＮＣＦ_２ＣＦ（ＣＦ_３）ＣＯ_２ ⁻Ｒ^１Ｒ^２Ｒ^３Ｒ^４Ｎ^＋，Ｏ（ＣＦ_２ＣＦ_２）_２ＮＣＦ_２ＣＦ_２ＣＯ_２ ⁻Ｒ^１Ｒ^２Ｒ^３Ｒ^４Ｎ^＋，Ｏ（ＣＦ_２ＣＦ_２）_２ＮＣＦ_２ＣＦ（ＣＦ_３）ＣＯ_２ ⁻Ｒ^１Ｒ^２Ｒ^３Ｒ^４Ｎ^＋，ＣＦ_２（ＣＦ_２ＣＦ_２）_２ＮＣＦ_２ＣＦ_２ＣＯ_２ ⁻Ｒ^１Ｒ^２Ｒ^３Ｒ^４Ｎ^＋，ＣＦ_２（ＣＦ_２ＣＦ_２）_２ＮＣＦ_２ＣＦ（ＣＦ_３）ＣＯ_２ ⁻Ｒ^１Ｒ^２Ｒ^３Ｒ^４Ｎ^＋，（Ｃ_４Ｆ_９）_２ＮＣＦ_２ＣＦ_２ＳＯ_３ ⁻Ｒ^１Ｒ^２Ｒ^３Ｒ^４Ｎ^＋，（Ｃ_４Ｆ_９）_２ＮＣＦ_２ＣＦ_２ＣＯ_２ ⁻Ｌｉ^＋，（Ｃ_４Ｆ_９）_２ＮＣＦ_２ＣＦ_２ＣＯ_２ ⁻Ｎａ^＋，（Ｃ_４Ｆ_９）_２ＮＣＦ_２ＣＦ_２ＣＯ_２ ⁻Ｋ^＋，（（Ｃ_４Ｆ_９）_２ＮＣＦ_２ＣＦ_２ＣＯ_２ ⁻）_２Ｃａ^２＋，（Ｃ_４Ｆ_９）_２ＮＣＦ_２ＣＦ_２ＣＯ_２ ⁻Ｈ_３Ｏ^＋（但し、上記Ｒ^１〜Ｒ^４は水素原子またはそれぞれ独立した炭素数１〜２０までの直鎖もしくは分岐状のアルキル基）からなる群から選択される少なくとも１以上のヘテロ原子含有ペルフルオロアルキル有機酸塩を含む、前項１に記載の乳化重合用乳化剤。
[７] 水性媒体中、フリーラジカルの存在下、少なくとも１種の乳化剤と少なくとも１種の開始剤との存在下で、少なくとも１種のフルオロモノマーを乳化重合することを含むフルオロポリマーの製造方法であって、
前記乳化剤として、前項１に記載の乳化重合用乳化剤を用いる、フルオロポリマーの製造方法。
[８] 前記乳化剤の添加量は、前記水性媒体の質量に対して、１００〜１０００ｐｐｍの範囲である、前項７に記載のフルオロポリマーの製造方法。
[９] 前記ヘテロ原子含有ペルフルオロアルキル有機酸塩の質量部は、前記乳化剤の質量部全体に対して、５０〜１００％の範囲である、前項７に記載のフルオロポリマーの製造方法。 In order to solve the above problems, the present invention employs the following configuration.
[1] An anion represented by the following formula (1);
^{H +, R 1 R 2 R} 3 R 4 N + ( ^where linear or branched alkyl group of up to R 1 to R ⁴ is from 1 to 20 carbon atoms which independently hydrogen atom or, _{respectively),} H ^{3 O} +, An emulsifier for emulsion polymerization comprising at least one heteroatom-containing perfluoroalkyl organic acid salt having one cation selected from the group consisting of Li ⁺ , K ⁺ , Na ⁺ , Ca ²⁺ and Mg ²⁺ .

Rf ¹ and Rf ² shown in the above formula (1) are the same or different C 1-6 perfluoroalkyl groups, and may be linear or branched. Rf ¹ and Rf ² may be directly bonded to form a ring, or may be bonded through an oxygen atom or a nitrogen atom to form a heterocyclic ring.
Rf ³ is a C 1-6 perfluoroalkylene group, and may be linear or branched.
X is CO ₂ or SO ₃ .
[2] The emulsion polymerization emulsifier according to item 1, wherein the anion is an anion represented by the following formula (2) having a perfluoroheterocycle having a nitrogen atom.

Rf ⁴ , Rf ⁵ and Rf ⁶ shown in the above formula (2) are the same or different C 1-6 perfluoroalkylene groups, and may be linear or branched.
Y is an oxygen atom, a nitrogen atom or a CF ₂ group.
X is CO ₂ or SO ₃ .
[3] The emulsion polymerization emulsifier according to item 1, wherein the anion is an anion represented by the following formula (3).

M and n shown in the above formula (3) are the same or different integers of 1 to 6, respectively.
Rf ⁷ is a C 1-6 perfluoroalkylene group, and may be linear or branched.
X is CO ₂ or SO ₃ .
[4] The emulsifier for emulsion polymerization according to item 1, wherein the anion is an anion selected from the group consisting of anions represented by the following formulas (4) to (27).

[5] The emulsion polymerization emulsifier according to item 1, wherein the anion is an anion selected from the group consisting of anions represented by the following formulas (28) to (43).

_{[6] (C 4 F 9} ) 2 NCF 2 CF 2 CO 2 - R 1 R 2 R 3 R 4 N +, (C 4 F 9) 2 NCF 2 CF (CF 3) CO 2 - R 1 R 2 R _{^{3 R 4 N +, O (}} CF 2 CF 2) 2 NCF 2 CF 2 CO 2 - R 1 R 2 R 3 R 4 N +, O (CF 2 CF 2) 2 NCF 2 CF (CF 3) CO 2 - ^{R 1 R 2 R 3 R 4} N +, CF 2 (CF 2 CF 2) 2 NCF 2 CF 2 CO 2 - R 1 R 2 R 3 R 4 N +, CF 2 (CF 2 CF 2) 2 NCF 2 CF ^{_{(CF 3) CO 2 - R}} 1 R 2 R 3 R 4 N +, (C 4 F 9) 2 NCF 2 CF 2 SO 3 - R 1 R 2 R 3 R 4 N +, (C 4 F 9) 2 ^{_{NCF 2 CF 2 CO 2 - Li}} +, (C 4 F 9) 2 NCF 2 CF 2 C O ₂ ⁻ Na ⁺ , (C ₄ F ₉ ) ₂ NCF ₂ CF ₂ CO ₂ ⁻ K ⁺ , ((C ₄ F ₉ ) ₂ NCF ₂ CF ₂ CO ₂ ⁻ ) ₂ Ca ²⁺ , (C ₄ F ₉ ) _{2 ^{NCF 2 CF 2 CO 2 - H}} 3 O + ( where the ^R 1 to R ⁴ is a hydrogen atom or independent linear or branched alkyl group having up to 20 carbon atoms) is selected from the group consisting of 2. The emulsifier for emulsion polymerization according to item 1, comprising at least one heteroatom-containing perfluoroalkyl organic acid salt.
[7] A process for producing a fluoropolymer comprising emulsion polymerization of at least one fluoromonomer in an aqueous medium in the presence of free radicals in the presence of at least one emulsifier and at least one initiator. There,
A method for producing a fluoropolymer, wherein the emulsifier for emulsion polymerization described in item 1 is used as the emulsifier.
[8] The method for producing a fluoropolymer according to item 7, wherein the amount of the emulsifier added is in the range of 100 to 1000 ppm with respect to the mass of the aqueous medium.
[9] The method for producing a fluoropolymer according to item 7, wherein the mass part of the heteroatom-containing perfluoroalkyl organic acid salt is in the range of 50 to 100% with respect to the entire mass part of the emulsifier.

  The emulsifier for emulsion polymerization of the present invention comprises a heteroatom-containing perfluoroalkyl organic acid salt in which two or more linear or branched perfluoroalkyl groups having 1 to 6 carbon atoms are chemically linked with nitrogen or oxygen. Although it is a main component and does not have a linear perfluoroalkyl group having 7 or more carbon atoms, the surface tension of water can be reduced with a smaller addition amount to the aqueous medium.

  Moreover, since the manufacturing method of the fluoropolymer of this invention uses the emulsifier for emulsion polymerization mentioned above for superposition | polymerization of a fluoro olefin, it becomes possible to reduce the addition amount of an emulsifier with respect to an aqueous medium.

  Hereinafter, an emulsifier for emulsion polymerization which is an embodiment to which the present invention is applied and a method for producing a fluoropolymer using the same, a heteroatom-containing perfluoroalkyl which is a main component of an emulsifier for emulsion polymerization and is a fluorosurfactant This will be described in detail below together with the organic acid salt.

<Emulsifier for emulsion polymerization>
The emulsifier for emulsion polymerization of this embodiment is mainly composed of a fluorosurfactant having no linear perfluoroalkyl group having 7 or more carbon atoms, which is considered to have high bioaccumulation in its structure. Specifically, as such a fluorosurfactant, two or more linear or branched perfluoroalkyl groups having 1 to 6 carbon atoms are chemically linked with nitrogen or oxygen, and contain hetero atoms. A perfluoroalkyl organic acid salt (that is, a salt containing an anion and a cation) is used as a main component of an emulsifier for emulsion polymerization.
Hereinafter, the heteroatom-containing perfluoroalkyl organic acid salt, which is the main component of the emulsifier for emulsion polymerization of the present embodiment, will be specifically described.

(Anion of heteroatom-containing perfluoroalkyl organic acid salt)
The anion of the heteroatom-containing perfluoroalkyl organic acid salt, which is the main component of the emulsifier for emulsion polymerization of this embodiment, can be represented by the following formula (1).

Here, Rf ¹ and Rf ² shown in the above formula (1) are the same or different C 1-6 perfluoroalkyl groups, and may be linear or branched. Rf ¹ and Rf ² may be directly bonded to form a ring, or may be bonded via an oxygen atom or a nitrogen atom to form a heterocyclic ring together with the oxygen atom or nitrogen atom to which both are bonded. It may be formed.
Rf ³ is a C 1-6 perfluoroalkylene group, and may be linear or branched.
X is CO ₂ or SO ₃ .

  Examples of the anion represented by the above formula (1) include those having a perfluoroheterocycle represented by the following formula (2), those having a perfluoroamine structure represented by the following formula (3), Is mentioned.

Here, Rf ⁴ , Rf ⁵ and Rf ⁶ shown in the above formula (2) are the same or different C 1-6 perfluoroalkylene groups, and may be linear or branched. .
Y is an oxygen atom, a nitrogen atom or a CF ₂ group.
Furthermore, X is CO ₂ or SO ₃ .

M and n shown in the above formula (3) are the same or different integers of 1 to 6, respectively.
Rf ⁷ is a C 1-6 perfluoroalkylene group, and may be linear or branched.
X is CO ₂ or SO ₃ .

Specific examples of the anion represented by the above formula (2) include those having perfluoropiperidine, perfluoropyrrolidine, perfluoropiperazine, perfluoromorpholine, and perfluorohexamethyleneimine as the perfluoroheterocycle.
More specifically, anions represented by the following formulas (4) to (27) are exemplified.

  Specific examples of the anion represented by the above formula (3) include anions represented by the following formulas (28) to (43).

(Cation of heteroatom-containing perfluoroalkyl organic acid salt)
The cation of the heteroatom-containing perfluoroalkyl organic acid salt, which is the main component of the emulsifier for emulsion polymerization of this embodiment, is particularly limited as long as it becomes soluble in an aqueous medium when combined with the above-described anion. It is not something. Specific examples of such cations include H ⁺ , NH ₄ ⁺ , H ₃ O ⁺ , Li ⁺ , K ⁺ , Na ⁺ , Ca ²⁺ and Mg ²⁺ .

(Specific example of heteroatom-containing perfluoroalkyl organic acid salt)
The heteroatom-containing perfluoroalkyl organic acid salt, which is the main component of the emulsifier for emulsion polymerization of this embodiment, is the above-mentioned anion and cation salt. Examples of such heteroatom-containing perfluoroalkyl organic acid _{salts, (C 4 F 9) 2} NCF 2 CF 2 CO 2 - NH 4 +, (C 4 F 9) 2 NCF 2 CF (CF 3) CO ^{_{2 - NH 4 +, O (}} CF 2 CF 2) 2 NCF 2 CF 2 CO 2 - NH 4 +, O (CF 2 CF 2) 2 NCF 2 CF (CF 3) CO 2 - NH 4 +, CF 2 ( _{CF 2 CF 2) 2 NCF 2} CF 2 CO 2 - NH 4 +, CF 2 (CF 2 CF 2) 2 NCF 2 CF (CF 3) CO 2 - NH 4 +, (C 4 F 9) 2 NCF 2 CF ^{_{2 SO 3 - NH 4 +,}} (C 4 F 9) 2 NCF 2 CF 2 CO 2 - Li +, (C 4 F 9) 2 NCF 2 CF 2 CO 2 - Na +, (C 4 F 9) 2 NCF ₂ CF ^{_{CO 2 - K +, ((}} C 4 F 9) 2 NCF 2 CF 2 CO 2 -) 2 Ca 2+, (C 4 F 9) 2 NCF 2 CF 2 CO 2 - include H 3 ^{O +,} and the like.

_{Further, (C 4 F 9) 2} NCF 2 CF 2 CO 2 - R 1 R 2 R 3 R 4 N +, (C 4 F 9) 2 NCF 2 CF (CF 3) CO 2 - R 1 R 2 R _{^{3 R 4 N +, O (}} CF 2 CF 2) 2 NCF 2 CF 2 CO 2 - R 1 R 2 R 3 R 4 N +, O (CF 2 CF 2) 2 NCF 2 CF (CF 3) CO 2 - ^{R 1 R 2 R 3 R 4} N +, CF 2 (CF 2 CF 2) 2 NCF 2 CF 2 CO 2 - R 1 R 2 R 3 R 4 N +, CF 2 (CF 2 CF 2) 2 NCF 2 CF ^{_{(CF 3) CO 2 - R}} 1 R 2 R 3 R 4 N +, (C 4 F 9) 2 NCF 2 CF 2 SO 3 - R 1 R 2 R 3 R 4 N + ( ^where, R 1 to R ⁴ Is a hydrogen atom or an independent straight chain or atom having 1 to 20 carbon atoms. Jo of an alkyl group).

Here, as the quaternary ammonium salt (R ¹ R ² R ³ R ⁴ N ⁺ ), R ^{1 to} R ⁴ are each a hydrogen atom or a linear or branched alkyl group having 1 to 20 carbon atoms independently of each other. If it is, it will not specifically limit. More specifically, examples of the compound in which R ¹ R ² R ³ R ⁴ are all the same include (CH ₃ ) ₄ N ⁺ , (C ₂ H ₅ ) ₄ N ⁺ , and (C ₃ H ₇ ) ₄ N ^+. , (C ₄ H ₉ ) ₄ N ⁺ , (C ₅ H ₁₁ ) ₄ N ⁺ , (C ₆ H ₁₃ ) ₄ N ⁺ , (C ₇ H ₁₅ ) ₄ N ⁺ , (C ₈ H ₁₇ ) ₄ N ⁺ , (C ₉ H ₁₉ ) ₄ N ⁺ , (C ₁₀ H ₂₁ ) ₄ N ^{+ and the} like. In addition, when R ¹ R ² R ³ is all a methyl group, for example, R ⁴ is (C ₂ H ₅ ), (C ₆ H ₁₃ ), (C ₈ H ₁₇ ), (C ₉ H ₁₉ ), Examples of the compound include (C ₁₀ H ₂₁ ), (C ₁₂ H ₂₅ ), (C ₁₄ H ₂₉ ), (C ₁₆ H ₃₃ ), and (C ₁₈ H ₃₇ ). Further, when all of R ¹ R ² are methyl groups, for example, all of R ³ R ⁴ are (C ₈ H ₁₇ ), (C ₁₀ H ₂₁ ), (C ₁₂ H ₂₅ ), (C ₁₄ H ₂₉ ). , (C ₁₆ H ₃₃ ), (C ₁₈ H ₃₇ ) and the like. Furthermore, examples of the case where R ¹ is a methyl group include compounds in which R ² R ³ R ⁴ are all (C ₄ H ₉ ), (C ₈ H ₁₇ ), and the like.

  These are merely examples, and the heteroatom-containing perfluoroalkyl organic acid salt applicable to the emulsifier for emulsion polymerization of the present embodiment is not limited thereto.

(Method for producing heteroatom-containing perfluoroalkyl organic acid salt)
The method for producing the heteroatom-containing perfluoroalkyl organic acid salt described above will be described below, classified according to the type of X constituting the anion shown in the above formula (1).

なお、上記式（４４）中に示されるＲｆ^１、Ｒｆ^２及びＲｆ^３は上記式（１）と同一であり、Ｚはフッ素原子、塩素原子、臭素原子、ヨウ素原子などのハロゲン原子である。 “When X = CO ₂ (Carboxylic Acid)”
When the heteroatom-containing perfluoroalkyl organic acid salt is an ammonium salt, a heteroatom-containing perfluoroalkylcarboxylic acid halide represented by the following formula (44) and R ¹ R ² R ³ R ⁴ N ⁺ OH ⁻ (wherein R ^{1 to} R ⁴ can be produced by reacting with a hydrogen atom or an independent linear or branched alkyl group having 1 to 20 carbon atoms.

Incidentally, ^Rf 1, Rf ² and Rf ³ shown in the above formula (44) is the same as the above formula (1), Z is a fluorine atom, a chlorine atom, a bromine atom, a halogen atom such as iodine atom.

  Here, the heteroatom-containing perfluoroalkylcarboxylic acid fluoride in which Z in the above formula (44) is a fluorine atom is, for example, electrolytic fluorination of a corresponding carboxylic acid ester or halide in hydrogen fluoride. Can be obtained. Moreover, when using what said Z is halogen atoms other than a fluorine atom, for example, the carboxylic acid fluoride which has the perfluoroalkyl group obtained by the said electrolytic fluorination is hydrolyzed, and corresponding carboxylic acid is used. After the formation, it can be obtained by reacting with an appropriate acid halogenating agent to derive the corresponding carboxylic acid halide.

When the heteroatom-containing perfluoroalkyl organic acid salt is a metal salt, the above R ¹ R ² R ³ R ⁴ N ⁺ OH ⁻ (wherein R ^{1 to} R ⁴ are each a hydrogen atom or an independent carbon number of 1 to Instead of up to 20 linear or branched alkyl groups) M ¹ OH, M ¹ ₂ CO ₃ or M ² (OH) ₂ , M ² CO ₃ (M ¹ = Li, K, Na, M ² = Ca, Mg).

なお、上記式（４５）中に示されるＲｆ^１、Ｒｆ^２及びＲｆ^３は上記式（１）と同一であり、Ｚはフッ素原子、塩素原子、臭素原子、ヨウ素原子などのハロゲン原子である。 “In the case of X = SO ₃ (sulfonic acid type)”
When the anion shown in the above formula (1) is a sulfonic acid type, it is represented by the following formula (45) instead of the heteroatom-containing perfluoroalkylcarboxylic acid halide represented by the above formula (44). By using a heteroatom-containing perfluoroalkylsulfonic acid halide, it can be produced in the same manner as in the carboxylic acid system.

Incidentally, ^Rf 1, Rf ² and Rf ³ shown in the above formula (45) is the same as the above formula (1), Z is a fluorine atom, a chlorine atom, a bromine atom, a halogen atom such as iodine atom.

  Here, the heteroatom-containing perfluoroalkylsulfonic acid halide represented by the above formula (45) is a corresponding sulfonic acid ester in the same manner as the heteroatom-containing perfluoroalkylcarboxylic acid halide represented by the above formula (44). Alternatively, it can be obtained by electrolytic fluorination of a halide.

In addition, the heteroatom-containing perfluoroalkyl organic acid salt applicable to the emulsifier for emulsion polymerization of this embodiment is obtained by acid decomposition of a carboxylate (or sulfonate) produced by the above-described method in the presence of an appropriate acid. Carboxylic acid (or sulfonic acid) obtained by M ¹ OH, M ¹ ₂ CO ₃ or M ² (OH) ₂ , M ² CO ₃ [M ¹ = R ¹ R ² R ³ R ⁴ N ⁺ ( Wherein R ^{1 to} R ⁴ are reacted with a hydrogen atom or an independent linear or branched alkyl group having 1 to 20 carbon atoms, Li, K, Na, M ² = Ca, Mg]. There may be. By this method, a higher purity heteroatom-containing perfluoroalkyl organic acid salt can be obtained.
As described above, the heteroatom-containing perfluoroalkyl organic acid salt that is the main component of the emulsifier for emulsion polymerization of the present embodiment is obtained.

  The emulsifier for emulsion polymerization of this embodiment is characterized by containing at least one or more of the above heteroatom-containing perfluoroalkyl organic acid salt that is a fluorosurfactant. That is, in the emulsifier for emulsion polymerization, the heteroatom-containing perfluoroalkyl organic acid salt may be used singly or in combination of two or more.

  Furthermore, the emulsifier for emulsion polymerization of the present embodiment may contain a non-fluorine surfactant in addition to the fluorine-based surfactant (the heteroatom-containing perfluoroalkyl organic acid salt) as the main component. Specific examples of non-fluorine surfactants include nonionic non-fluorine surfactants, anionic non-fluorine surfactants, and amphoteric surfactants.

  Nonionic non-fluorine surfactants include, for example, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, polyoxyethylene sorbitan alkyl esters, glycerin esters. And derivatives thereof.

  Examples of the anionic non-fluorine surfactant include esters of higher alcohol sulfates such as sodium alkyl sulfonate, sodium alkyl benzene sulfonate, sodium dialkyl ester succinate, and alkyl diphenyl ether disulfonate sodium salt. It is done.

  Examples of amphoteric surfactants include lauryl betaine.

  Moreover, the emulsifier for emulsion polymerization of the present embodiment is based on the mass part of the heteroatom-containing perfluoroalkyl organic acid salt as the main component (when two or more kinds are contained, the whole of the emulsifier as a whole). Is preferably in the range of 50 to 100%. Here, when the mass part of the heteroatom-containing perfluoroalkyl organic acid salt is less than 50% with respect to the mass part of the whole emulsifier, the emulsifying effect is not sufficiently exhibited, which is not preferable. On the other hand, the above range is preferable because the emulsification effect is sufficiently exhibited.

  Since the emulsifier for emulsion polymerization of this embodiment does not have a linear perfluoroalkyl group having 7 or more carbon atoms, bioaccumulation can be reduced. In addition, the emulsifier for emulsion polymerization of the present embodiment has a structure in which the main component fluorine-based surfactant has a heteroatom, so that it is decomposed compared to a perfluoroalkyl group-containing compound in which the main skeleton is formed only from carbon. The effect that it becomes easy is acquired.

  Furthermore, the emulsifier for emulsion polymerization of this embodiment is a heteroatom-containing perfluoroalkyl organic compound in which two or more linear or branched perfluoroalkyl groups having 1 to 6 carbon atoms are chemically linked with nitrogen or oxygen. The acid salt is the main component, and as shown in the examples described later, the surface tension of water can be reduced with a smaller amount of addition to the aqueous medium.

  Furthermore, when the emulsifier for emulsion polymerization of this embodiment has a structure of a branched perfluoroalkylene group next to a carbonyl group or a sulfonyl group, it can be easily decomposed, and the resulting fluoropolymer The effect that an emulsifier becomes difficult to remain is acquired.

<Method for producing fluoropolymer>
Next, the manufacturing method of the fluoropolymer using the emulsifier for emulsion polymerization which has as a main component the hetero atom containing perfluoroalkyl organic acid salt mentioned above is demonstrated below.

  In the method for producing a fluoropolymer of this embodiment, at least one fluoromonomer as a raw material is emulsified in an aqueous medium in the presence of free radicals in the presence of at least one emulsifier and at least one initiator. It is a thing to superpose | polymerize, The emulsifier for emulsion polymerization containing at least 1 or more of the hetero atom containing perfluoroalkyl organic acid salt mentioned above is used as an emulsifier.

(Aqueous medium)
An aqueous medium will not be specifically limited if it is a liquid containing water, In addition to water, it may contain a water-soluble organic solvent in the range which does not impair the characteristic of this invention. As the aqueous medium, water is preferable.

(material)
The raw material fluoromonomer (fluoroolefin) includes tetrafluoroethylene (TFE), vinylidene fluoride (VDF), chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), trifluoropropylene, and vinyl fluoride (VF). ), Perfluoroalkyl vinyl ether (for example, perfluoromethyl vinyl ether, perfluoroethyl vinyl ether) and the like. These fluoroolefins can be homopolymerized or copolymerized from a mixture of two or more.

(Polymerization initiator)
The polymerization initiator applicable to the fluoropolymer production method of the present embodiment is not particularly limited as long as it generates radicals in emulsion polymerization. Examples of such a polymerization initiator include persulfates such as ammonium persulfate and potassium persulfate, organic peroxides such as disuccinic acid peroxide, bisglutaric acid peroxide, and t-butyl hydroperoxide, and potassium permanganate. An oxidizing agent etc. are mentioned. The polymerization initiator may be redox combined with a reducing agent such as sulfite, bisulfite, oxalic acid or ferrous chloride.

(emulsifier)
The fluoropolymer production method of the present embodiment is characterized by using the above-described emulsifier for emulsion polymerization as an emulsifier for emulsion polymerization.

(Other additive components)
In the method for producing a fluoropolymer of this embodiment, a molecular weight modifier may be added. Examples of the molecular weight modifier include ester compounds such as dimethyl malonate, diethyl malonate, methyl acetate, ethyl acetate, butyl acetate, dimethyl succinate, isopentane, isopropanol, acetone, mercaptan, carbon tetrachloride, cyclohexane, iodomethane, Examples thereof include iodopropane, isopropyl iodide, diiodomethane, and diiodopropane.

  Furthermore, a chain transfer agent, a pH adjuster, a buffering agent, and the like may be added as optional components as appropriate, but the amount is preferably used within a range that does not impair the effects of the present invention.

  The reactor used in the method for producing a fluoropolymer according to the present embodiment is not particularly limited as long as it is equipped with a heating device and comes into contact with a gas and a solid or a liquid. Can do. An example of such a reactor is an autoclave.

  In the method for producing a fluoropolymer of this embodiment, polymerization is performed according to the following procedure. First, the above-described reaction vessel is filled with an aqueous medium (for example, water), an emulsifier for emulsion polymerization, a raw material fluoroolefin (monomer), and various additives, and oxygen in the system is removed with an inert gas such as nitrogen. After that, the contents of the reactor are stirred and heated to a predetermined polymerization temperature. Next, an initiator is added at a predetermined ratio to start the polymerization.

  The polymerization temperature is not particularly limited, and an optimum temperature can be adopted according to the kind of the polymerization initiator. The polymerization temperature is preferably 40 to 120 ° C, more preferably 50 to 100 ° C.

  The method for supplying the fluoroolefin (monomer) is not particularly limited, and it may be supplied continuously or sequentially. The monomer is preferably supplied so as to keep the pressure in the system constant.

  Specifically, the addition amount of the initiator is preferably 50 to 10000 ppm, more preferably 100 to 5000 ppm with respect to the mass of the aqueous medium. In addition, the addition amount of an initiator can employ | adopt an optimal amount with the kind of initiator.

  The lower limit of the addition amount of the emulsifier for emulsion polymerization is preferably 10 ppm or more, and more preferably 100 ppm or more with respect to the mass of the aqueous medium. The upper limit is preferably 10,000 ppm or less, and more preferably 1000 ppm or less. Here, when the addition amount of the emulsifier for emulsion polymerization relative to the mass of the aqueous medium is less than 10 ppm, the emulsification effect is not sufficiently exhibited, which is not preferable. On the other hand, if it exceeds 10000 ppm, an unnecessary emulsifier is used, which is not preferable because the cost for producing the polymer increases. On the other hand, when it is in the range of 10 to 10,000 ppm, it is preferable because the emulsifying effect is sufficiently exhibited, and when it is 100 to 1000 ppm, the emulsifying effect is sufficiently exhibited and the cost for producing the polymer Is more preferable because it can be reduced.

  As described above, the fluoropolymer production method of the present embodiment uses the above-described emulsifier for emulsion polymerization as an emulsifier for emulsion polymerization of fluoroolefins, and therefore the amount of the emulsifier added to the aqueous medium can be reduced. .

  Moreover, since the fluoropolymer production method of the present embodiment uses the above-described emulsifier for emulsion polymerization for the polymerization of fluoromonomer (fluoroolefin), a fluoropolymer having high dispersion stability in an aqueous medium is obtained. It is done. Furthermore, as shown in the Examples described later, since the amount of the emulsifier can be reduced, it becomes possible to produce a fluoropolymer at a lower cost.

  Furthermore, since the fluoropolymer production method of the present embodiment has the characteristic that the above-mentioned emulsifier for emulsion polymerization is easily decomposed, an effect that the emulsifier used for emulsion polymerization hardly remains in the produced fluoropolymer is obtained.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  Hereinafter, the effects of the present invention will be described in more detail by way of examples. In addition, this invention is not limited at all by the Example.

Example 1
_{"(C 4 F 9) 2 NCF} 2 CF 2 CO 2 - NH 4 + synthesis"
_{(C 4 H 9) 2 NCH} 2 CH 2 CO 2 obtained by electrolytic fluorination of _{CH 3 (C 4 F 9)} 12,5wt% aqueous solution of sodium hydroxide _{2 NCF 2 CF 2 COF (47,8g} ) at room temperature (51, 1 g). After stirring at room temperature for 1 hour, ethyl acetate (150 ml) was added to the reaction solution, extraction was performed, and the ethyl acetate layer was concentrated and dried to give (C ₄ F ₉ ) ₂ NCF ₂ CF ₂ as a crude product. CO ₂ ⁻ Na ⁺ (38, 8 g) was obtained.

Then, the resulting _{(C 4 F 9) 2 NCF} 2 CF 2 CO 2 - Na + (38,8g) in concentrated sulfuric acid at room temperature (95,7%, 75,0g) was charged, 2 at 110 ° C. After stirring for a period of time, vacuum distillation was performed to obtain (C ₄ F ₉ ) ₂ NCF ₂ CF ₂ CO ₂ H (27, 7 g).

Further, the obtained (C ₄ F ₉ ) ₂ NCF ₂ CF ₂ CO ₂ H (24, 8 g) and ion-exchanged water (25, 0 g) were mixed, and 28 wt% aqueous ammonia (2, 8 g) was added thereto. Added dropwise at room temperature. After reacting for 1 hour at room temperature, water was distilled off under reduced pressure, by _{dryness, (C 4 F 9) 2} NCF 2 CF 2 CO 2 - was obtained NH 4 + (25,2g).

(Example 2)
"Synthesis of _{(C 4 F 9) 2 NCF} 2 CF 2 CO 2 N (CH 3) 4 '
(C ₄ F ₉ ) ₂ NCF ₂ CF ₂ CO ₂ H (27.7 g) obtained by synthesis in the same manner as in Example 1 and ion-exchanged water (64.6 g) were mixed to obtain 25% water. An aqueous tetramethylammonium oxide solution (16.9 g) was added dropwise while heating to 45 ° C. After reacting at room temperature for 1 hour, water was distilled off under reduced pressure and dried to obtain (C ₄ F ₉ ) ₂ NCF ₂ CF ₂ CO ₂ N (CH ₃ ) ₄ (30.9 g).

(Example 3)
_{"CF 2 (CF 2 CF 2)} 2 NCF 2 CF (CF 3) CO 2 - NH 4 + synthesis"
CF ₂ (CF ₂ CF ₂ ) ₂ NCF ₂ CF (CF ₃ ) COF (55, 7 g) obtained by electrolytic fluorination of CH ₂ (CH ₂ CH ₂ ) ₂ NCH ₂ CH (CH ₃ ) CO ₂ CH ₃ The solution was added dropwise to a 12, 5 wt% aqueous sodium hydroxide solution (92, 8 g) at room temperature. After stirring at room temperature for 1 hour, the precipitated NaF was removed by filtration. Concentrated sulfuric acid (28, 5 g) was added dropwise to the obtained aqueous solution at room temperature and allowed to react for 1 hour. Thereafter, stirring was stopped, sulfuric acid was removed by decantation, and concentrated sulfuric acid (40, 0 g) was again added. After stirring for 1 hour, sulfuric acid was removed and vacuum distillation was performed to obtain CF ₂ (CF ₂ CF ₂ ) ₂ NCF ₂ CF (CF ₃ ) CO ₂ H (39, 0 g).

The obtained CF ₂ (CF ₂ CF ₂ ) ₂ NCF ₂ CF (CF ₃ ) CO ₂ H (30, 1 g) was dissolved in ion-exchanged water (30, 1 g), and 28 wt% ammonia was cooled to 20 ° C. or lower. Water (4, 4 g) was added dropwise. After reacting for 1 hour at room temperature, water was distilled off under reduced pressure, by _{dryness, CF 2 (CF 2 CF 2} ) 2 NCF 2 CF (CF 3) CO 2 - NH 4 + a (30,7g) Obtained.

(Verification test 1)
Five compounds, i.e., compounds of the following formula (46) (hereinafter, referred to as perfluoroalkyl morpholine ring containing ammonium salt), _{"(C 4 F 9) 2 NCF} 2 CF 2 CO 2 - NH 4 + ", " _{(C 4 F 9 SO 2)} 2 N - NH 4 + "," _{(C 4 F 9) 2 NCF} 2 CF 2 CO 2 N (CH 3) 4 "," ^{_{C 7 F 15 CO 2 - NH}} 4 + " Was added to water at concentrations of 1000, 500, and 100 ppm, and then the surface tension value in water was measured. The surface tension was measured by the Wilhelmy method using an automatic surface tension meter CBVP-Z manufactured by Kyowa Interface Science. The results are shown in Table 1 below.

From Table 1, the main component of the emulsifier for emulsion polymerization of the present invention "perfluoroalkyl morpholine ring containing ammonium salt", _{"(C 4 F 9) 2 NCF} 2 CF 2 CO 2 - NH 4 + " and _"(C 4 F ₉ ) ₂ NCF ₂ CF ₂ CO ₂ N (CH ₃ ) ₄ ”, the surface tension of water is reduced to 28, 19 and 18 (mN / m), respectively, when 1000 ppm is added to water. It was found that the surface tension can be reduced with a small addition amount compared to the above two types.
Also, _{"(C 4 F 9 SO 2)} 2 N - NH 4 + " and ^{_{"C 7 F 15 CO 2 - NH}} 4 + ", respectively the surface tension of water in the case of 1000ppm added into water 40, 55 (mN is a / m), this value is the main component of the emulsifier for emulsion polymerization of the present invention "perfluoroalkyl morpholine ring containing ammonium salt", _{"(C 4 F 9) 2 NCF} 2 CF 2 CO 2 - NH 4 + "And" (C ₄ F ₉ ) ₂ NCF ₂ CF ₂ CO ₂ N (CH ₃ ) ₄ "were found to be achieved by the addition of 100 ppm, which is an almost 1/10 addition.
That is, "perfluoro morpholine ring containing ammonium salt", _{"(C 4 F 9) 2 NCF} 2 CF 2 CO 2 - NH 4 + " and _{"(C 4 F 9) 2 NCF} 2 CF 2 CO 2 N (CH 3) It has been suggested that when emulsion polymerization is carried out using the emulsifier for emulsion polymerization of the present invention having ₄ "as a main component, the polymerization can be carried out with a smaller addition amount.

(Example 4)
"Emulsion polymerization of tetrafluoroethylene using ammonium salt containing perfluoromorpholine ring as emulsifier"
In a 500 mL autoclave, water (150 g), dibasic potassium monophosphate (0, 05 g), ammonium persulfate (0, 5 g), perfluoromorpholine ring-containing ammonium salt (0, 15 g), dimethyl malonate (0, 1 g) Was charged. Next, the reaction vessel was purged with nitrogen to remove oxygen. Thereafter, tetrafluoroethylene (50, 0 g) was charged and reacted at 70 ° C. for 16 hours to obtain an aqueous dispersion of PTFE (average particle size: 199 nm). The obtained PTFE was uniformly dispersed in water, and no sediment was observed.
In Examples 4 to 7 and Comparative Examples 1 to 3, the average particle size of PTFE particles in the aqueous dispersion was measured using a concentrated particle size analyzer (FPAR-1000 manufactured by Otsuka Electronics Co., Ltd.).

(Example 5)
"- emulsion polymerization of tetrafluoroethylene using an _NH ^{4 +} as an emulsifier _{(C 4 F 9) 2 NCF} 2 CF 2 CO 2 "
Instead of perfluoro morpholine ring containing ammonium _{salts, (C 4 F 9) 2} NCF 2 CF 2 CO 2 - except for the use of _NH ^{4 +,} the same procedure as in Example 4, an aqueous dispersion of PTFE (average particle size : 190 nm). Even in this case, the obtained PTFE was uniformly dispersed in water, and no sediment was observed.

(Example 6)
"- emulsion polymerization of tetrafluoroethylene using Li ⁺ as the emulsifier _{(C 4 F 9) 2 NCF} 2 CF 2 CO 2 "
Instead of perfluoro morpholine ring containing ammonium salts _{(C 4 F 9) 2 NCF} 2 CF 2 CO 2 - except for the use of Li ⁺ in the same manner as in Example 4, an aqueous dispersion of PTFE (average particle size: 204 nm) Got. Even in this case, the obtained PTFE was uniformly dispersed in water, and no sediment was observed.

(Example 7)
_{"(C 4 F 9) 2 NCF} 2 CF 2 CO 2 - emulsion polymerization of tetrafluoroethylene using an _NH ^{4 +} as an emulsifier (amount added small)"
_{(C 4 F 9) 2 NCF} 2 CF 2 CO 2 - except that the 0,08g of _NH ^{4 +} addition amount of in the same manner as in Example 5 to obtain a dispersion of PTFE. Despite reducing the amount of emulsifier added, the obtained PTFE was uniformly dispersed in water, and no sediment was observed. The average particle size was 212 nm.

(Comparative Example 1)
_{(C 4 F 9 SO 2)} 2 N - NH 4 + in place of the emulsion polymerization perfluoroalkyl morpholine ring containing ammonium salts of tetrafluoroethylene used as an emulsifier _{(C 4 F 9 SO 2)} 2 N - with _NH ^{4 +} Except for the above, an aqueous dispersion of PTFE (average particle size: 230 nm) was obtained in the same manner as in Example 4. Although the dispersibility of the obtained PTFE was good, a part of PTFE was precipitated over time.

(Comparative Example 2)
_"C 7 _F 15 _CO ² - emulsion polymerization of tetrafluoroethylene using an _NH ^{4 +} as an emulsifier"
Give: except for using - ^{_{"+ NH 4 C 7 F 15 CO}} 2 ", in the same manner as in Example 4, an aqueous dispersion of PTFE (244 nm average particle size) instead of perfluoro morpholine ring containing ammonium salts, It was. Although the dispersibility of the obtained PTFE was good, sedimentation of PTFE was confirmed over time. Moreover, the sedimentation speed was the fastest compared with Examples 4-7 and Comparative Example 1.

(Comparative Example 3)
"Emulsion polymerization of tetrafluoroethylene without using emulsifier"
A PTFE aqueous dispersion (average particle size: 30, 5 μm) was obtained in the same manner as in Example 4 except that the perfluoromorpholine ring-containing ammonium salt was not used as the emulsifier. The obtained dispersion was poor in dispersibility, and it was confirmed that PTFE immediately settled.

  The emulsifier for emulsion polymerization of the present invention can reduce the surface tension of water with a small addition amount compared to existing emulsifiers such as PFOA. Moreover, the fluoropolymer excellent in dispersion stability can be obtained by using it as an emulsifier at the time of superposition | polymerization of a fluoro olefin. In addition, the method for producing a fluoropolymer of the present invention uses the above-mentioned emulsifier for emulsion polymerization as an emulsifier used for polymerization, and the amount of the emulsifier can be reduced, so that it becomes possible to produce a fluoropolymer at a lower cost. . The emulsifier for emulsion polymerization of the present invention is useful as an emulsifier for producing a fluoropolymer.

Claims (9)

An anion represented by the following formula (1);
^{H +, R 1 R 2 R} 3 R 4 N + ( ^where linear or branched alkyl group of up to R 1 to R ⁴ is from 1 to 20 carbon atoms which independently hydrogen atom or, _{respectively),} H ^{3 O} +, An emulsifier for emulsion polymerization comprising at least one heteroatom-containing perfluoroalkyl organic acid salt having one cation selected from the group consisting of Li ⁺ , K ⁺ , Na ⁺ , Ca ²⁺ and Mg ²⁺ .

Rf ¹ and Rf ² shown in the above formula (1) are the same or different C 1-6 perfluoroalkyl groups, and may be linear or branched. Rf ¹ and Rf ² may be directly bonded to form a ring, or may be bonded through an oxygen atom or a nitrogen atom to form a heterocyclic ring.
Rf ³ is a C 1-6 perfluoroalkylene group, and may be linear or branched.
X is CO ₂ or SO ₃ . The emulsifier for emulsion polymerization according to claim 1, wherein the anion is an anion represented by the following formula (2) having a perfluoroheterocycle having a nitrogen atom.

Rf ⁴ , Rf ⁵ and Rf ⁶ shown in the above formula (2) are the same or different C 1-6 perfluoroalkylene groups, and may be linear or branched.
Y is an oxygen atom, a nitrogen atom or a CF ₂ group.
X is CO ₂ or SO ₃ . The emulsifier for emulsion polymerization according to claim 1, wherein the anion is an anion represented by the following formula (3).

M and n shown in the above formula (3) are the same or different integers of 1 to 6, respectively.
Rf ⁷ is a C 1-6 perfluoroalkylene group, and may be linear or branched.
X is CO ₂ or SO ₃ . The emulsifier for emulsion polymerization according to claim 1, wherein the anion is an anion selected from the group consisting of anions represented by the following formulas (4) to (27).

The emulsifier for emulsion polymerization according to claim 1, wherein the anion is an anion selected from the group consisting of anions represented by the following formulas (28) to (43).

_{(C 4 F 9) 2 NCF} 2 CF 2 CO 2 - R 1 R 2 R 3 R 4 N +, (C 4 F 9) 2 NCF 2 CF (CF 3) CO 2 - R 1 R 2 R 3 R 4 ^{_{N +, O (CF 2 CF}} 2) 2 NCF 2 CF 2 CO 2 - R 1 R 2 R 3 R 4 N +, O (CF 2 CF 2) 2 NCF 2 CF (CF 3) CO 2 - R 1 R ^{2 R 3 R 4 N +,} CF 2 (CF 2 CF 2) 2 NCF 2 CF 2 CO 2 - R 1 R 2 R 3 R 4 N +, CF 2 (CF 2 CF 2) 2 NCF 2 CF (CF 3 ^{_{) CO 2 - R 1 R 2}} R 3 R 4 N +, (C 4 F 9) 2 NCF 2 CF 2 SO 3 - R 1 R 2 R 3 R 4 N +, (C 4 F 9) 2 NCF 2 CF ^{_{2 CO 2 - Li +, (}} C 4 F 9) 2 NCF 2 CF 2 CO ^{_{- Na +, (C 4 F}} 9) 2 NCF 2 CF 2 CO 2 - K +, ((C 4 F 9) 2 NCF 2 CF 2 CO 2 -) 2 Ca 2+, (C 4 F 9) 2 NCF 2 ^{_{CF 2 CO 2 - H 3 O}} + ( where the ^R 1 to R ⁴ is a hydrogen atom or independent linear or branched alkyl group having up to 20 carbon atoms) at least one selected from the group consisting of The emulsifier for emulsion polymerization according to claim 1, comprising the above heteroatom-containing perfluoroalkyl organic acid salt. A process for producing a fluoropolymer comprising emulsion polymerizing at least one fluoromonomer in an aqueous medium in the presence of free radicals in the presence of at least one emulsifier and at least one initiator, comprising:
A method for producing a fluoropolymer, wherein the emulsifier for emulsion polymerization according to claim 1 is used as the emulsifier.   The method for producing a fluoropolymer according to claim 7, wherein the addition amount of the emulsifier is in a range of 100 to 1000 ppm with respect to a mass of the aqueous medium.   The mass part of the said hetero atom containing perfluoroalkyl organic acid salt is a manufacturing method of the fluoropolymer of Claim 7 which is the range of 50 to 100% with respect to the whole mass part of the said emulsifier.