JP7295507B2 - Method for producing fluororesin - Google Patents

Description

The present invention relates to a method for producing fluororesin.

A fluororesin containing a fluorine-containing alicyclic structure (hereinafter referred to as the fluororesin) exhibits amorphous properties and is excellent in transparency, liquid repellency, durability, electrical properties, etc., so it is used in various fields such as optics and electronics. used for purposes.

As the fluororesin, for example, in Patent Document 1, a cyclized polymer of perfluoro(4-vinyloxy-1-butene), in Non-Patent Document 1, poly(perfluoro-2-methylene-4-methyl-1,3 -dioxolanes) have been reported.

The fluororesin is generally provided in the form of a solution in many cases, but in the case of melt molding, it is possible to continuously supply the resin to the inside of the molding machine, so the resin is preferably in the form of particles. Desired. In addition, in other wide-ranging applications, the resin is required to be in the form of particles from the viewpoint of handleability and solubility.

WO2014/156996

Macromolecules, 2005, 38, 4237-4245

In Patent Document 1, suspension polymerization is exemplified as a method for obtaining particles of the fluororesin. However, dispersants and emulsifiers used as polymerization aids remain inside the resin particles and become foreign matter or cause coloration when heated. could have been lost. Further, according to the present inventors, particles cannot be obtained in suspension polymerization without using a dispersant.

In addition, in order to ensure the strict cleanliness required in the fields of optics and electronics, it is desirable to filter the fluororesin solution to remove foreign substances before granulating. For this purpose, it is necessary to once dissolve the fluororesin in a good solvent to form a solution. However, according to the present inventors, in the method of obtaining powder by dropping a polymer solution dissolved in a good solvent into a poor solvent, which is generally known as a reprecipitation method, the fluororesin is in the form of strands, cotton, etc. In addition, the resulting fluororesin has a very low bulk density and is poor in handleability as a powder.

In addition, according to the present inventors, the resins described in Patent Document 1 and Non-Patent Documents have an amorphous shape, so it is difficult to remove the solvent taken inside the resin, Since the solvent remains in the resin, there is a problem that the amount of weight loss during heating is large, foaming occurs during molding, or the work environment during molding deteriorates.

The present invention has been made in view of the above problems, and its object is to provide a fluorine-containing polymer that is excellent in productivity, capable of removing foreign matter, has a large bulk density, is excellent in handleability as a powder, and has a small heat weight loss. An object of the present invention is to provide a method for producing fluororesin particles containing an alicyclic structure.

As a result of intensive studies aimed at achieving the above objects, the present inventors have found that a specific method for producing fluororesin particles containing a fluorine-containing alicyclic structure can solve the above problems, and have completed the present invention. Arrived.

（式（１）中、Ｒｆ₁、Ｒｆ₂、Ｒｆ₃、Ｒｆ₄はそれぞれ独立してフッ素原子、炭素数１～７の直鎖状のパーフルオロアルキル基、炭素数３～７の分岐状のパーフルオロアルキル基または、炭素数３～７の環状のパーフルオロアルキル基からなる群の１種を示し、前記パーフルオロアルキル基はエーテル性酸素原子を有していてもよく、また、Ｒｆ₁、Ｒｆ₂、Ｒｆ₃、Ｒｆ₄は互いに連結して炭素数４以上８以下の環を形成してもよく、該環はエーテル性酸素原子を含む環であってもよい。）
［３］
前記重合工程では、下記一般式（４）で表される単量体を、ラジカル重合開始剤及びフッ素樹脂Ａに対する良溶媒ｂの存在下で重合させて、一般式（１）で表されるフッ素樹脂を得る、［２］に記載のフッ素樹脂の製造方法。

（式（４）中、Ｒｆ₁、Ｒｆ₂、Ｒｆ₃、Ｒｆ₄はそれぞれ独立してフッ素原子、炭素数１～７の直鎖状のパーフルオロアルキル基、炭素数３～７の分岐状のパーフルオロアルキル基または、炭素数３～７の環状のパーフルオロアルキル基からなる群の１種を示し、前記パーフルオロアルキル基はエーテル性酸素原子を有していてもよく、また、Ｒｆ₁、Ｒｆ₂、Ｒｆ₃、Ｒｆ₄は互いに連結して炭素数４以上８以下の環を形成してもよく、該環はエーテル性酸素原子を含む環であってもよい。）
［４］
前記析出工程が、フッ素樹脂Ａと良溶媒ｂとを含むフッ素樹脂Ａ溶液に、撹拌下、フッ素樹脂Ａに対する貧溶媒ｃを加えることによりフッ素樹脂Ａの粒子を析出させる工程である、［１］～［３］のいずれかに記載のフッ素樹脂の製造方法。
［５］
前記撹拌が、単位撹拌容量あたりの撹拌機モータ動力の値であるＰｖ値が０．０５～５０ｋｗ／ｍ³での撹拌である、［４］に記載のフッ素樹脂の製造方法。
［６］
良溶媒ｂが分子内に水素原子を有する含フッ素溶媒である、［１］～［５］のいずれかに記載のフッ素樹脂の製造方法。
［７］
析出工程で得られるフッ素樹脂は、嵩密度が０．２５～１．５ｇ／ｃｍ³である、［１］～［６］のいずれかに記載のフッ素樹脂の製造方法。
［８］
析出工程で得られるフッ素樹脂は、体積平均粒子径が５～２０００μｍである、［１］～［７］のいずれかに記載のフッ素樹脂の製造方法。
［９］
析出工程で得られるフッ素樹脂は、重量平均分子量が５×１０⁴～３×１０⁵である、［１］～［８］のいずれかに記載のフッ素樹脂の製造方法。 The present invention is as follows.
[1]
A polymerization step of polymerizing a monomer containing a fluorine-containing alicyclic structure in the presence of a radical polymerization initiator to obtain a fluororesin A containing a fluorine-containing alicyclic structure, and a fluororesin containing a fluorine-containing alicyclic structure Production of a fluororesin containing a fluorinated alicyclic structure, including a precipitation step of precipitating the fluororesin A by adding a poor solvent c for the fluororesin A to a fluororesin A solution containing A and a good solvent b. Method.
[2]
The method for producing a fluororesin according to [1], wherein the fluororesin A containing a fluorine-containing alicyclic structure is a fluororesin represented by the following general formula (1).

(In formula (1), Rf ₁ , Rf ₂ , Rf ₃ and Rf ₄ are each independently a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, a branched perfluoroalkyl group having 3 to 7 carbon atoms, represents one member of the group consisting of a perfluoroalkyl group or a cyclic perfluoroalkyl group having 3 to 7 carbon atoms, the perfluoroalkyl group optionally having an etheric oxygen atom, and Rf ₁ , Rf ₂ , Rf ₃ and Rf ₄ may be linked together to form a ring having 4 to 8 carbon atoms, and the ring may be a ring containing an etheric oxygen atom.)
[3]
In the polymerization step, a monomer represented by the following general formula (4) is polymerized in the presence of a radical polymerization initiator and a good solvent b for the fluororesin A to obtain a fluorine represented by the general formula (1) The method for producing a fluororesin according to [2], wherein the resin is obtained.

(In the formula (4), Rf ₁ , Rf ₂ , Rf ₃ and Rf ₄ are each independently a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, a branched perfluoroalkyl group having 3 to 7 carbon atoms, represents one member of the group consisting of a perfluoroalkyl group or a cyclic perfluoroalkyl group having 3 to 7 carbon atoms, the perfluoroalkyl group optionally having an etheric oxygen atom, and Rf ₁ , Rf ₂ , Rf ₃ and Rf ₄ may be linked together to form a ring having 4 to 8 carbon atoms, and the ring may be a ring containing an etheric oxygen atom.)
[4]
The precipitation step is a step of precipitating the particles of the fluororesin A by adding the poor solvent c for the fluororesin A to the fluororesin A solution containing the fluororesin A and the good solvent b under stirring [1]. A method for producing a fluororesin according to any one of [3].
[5]
The method for producing a fluororesin according to [4], wherein the stirring is performed at a Pv value of 0.05 to 50 kw/m ³ , which is a value of power of the stirrer motor per unit stirring capacity.
[6]
The method for producing a fluororesin according to any one of [1] to [5], wherein the good solvent b is a fluorine-containing solvent having a hydrogen atom in its molecule.
[7]
The method for producing a fluororesin according to any one of [1] to [6], wherein the fluororesin obtained in the precipitation step has a bulk density of 0.25 to 1.5 g/cm ³ .
[8]
The method for producing a fluororesin according to any one of [1] to [7], wherein the fluororesin obtained in the precipitation step has a volume average particle size of 5 to 2000 μm.
[9]
The method for producing a fluororesin according to any one of [1] to [8], wherein the fluororesin obtained in the precipitation step has a weight average molecular weight of 5×10 ⁴ to 3×10 ⁵ .

According to the present invention, it is possible to provide a method for producing fluororesin particles containing a fluorine-containing alicyclic structure, which have a high bulk density, are excellent in handleability as a powder, and exhibit a small heat weight loss. The manufacturing method of the present invention also has the advantage of being excellent in productivity and capable of removing foreign matter.

1 is a diagram showing the particle size distribution of resin particles produced in Example 1. FIG.

The method for producing a fluororesin of the present invention comprises a polymerization step of obtaining a fluororesin A having a fluorinated alicyclic structure by polymerizing a monomer having a fluorinated alicyclic structure in the presence of a radical polymerization initiator; A precipitation step of precipitating the fluororesin A by adding the poor solvent c for the fluororesin A to the fluororesin A solution containing the fluororesin A containing the fluorine-containing alicyclic structure and the good solvent b.

The structure of the fluororesin containing a fluorine-containing alicyclic structure (hereinafter referred to as "fluororesin A") is not particularly limited as long as it contains a fluorine-containing alicyclic structure. Those containing a residue unit represented by, perfluoro(4-vinyloxy-1-butene) cyclized polymers and copolymers, perfluoro(2,2-dimethyl-1,3-dioxole) polymers and copolymers Polymers, copolymers of perfluoro(2,2-dimethyl-1,3-dioxole) and tetrafluoroethylene, polymers of 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole and copolymers, and copolymers of 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole and tetrafluoroethylene.

（式（１）中、Ｒｆ₁、Ｒｆ₂、Ｒｆ₃、Ｒｆ₄はそれぞれ独立してフッ素原子、炭素数１～７の直鎖状のパーフルオロアルキル基、炭素数３～７の分岐状のパーフルオロアルキル基または、炭素数３～７の環状のパーフルオロアルキル基からなる群の１種を示し、前記パーフルオロアルキル基はエーテル性酸素原子を有していてもよく、また、Ｒｆ₁、Ｒｆ₂、Ｒｆ₃、Ｒｆ₄は互いに連結して炭素数４以上８以下の環を形成してもよく、該環はエーテル性酸素原子を含む環であってもよい。）

(In formula (1), Rf ₁ , Rf ₂ , Rf ₃ and Rf ₄ are each independently a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, a branched perfluoroalkyl group having 3 to 7 carbon atoms, represents one member of the group consisting of a perfluoroalkyl group or a cyclic perfluoroalkyl group having 3 to 7 carbon atoms, the perfluoroalkyl group optionally having an etheric oxygen atom, and Rf ₁ , Rf ₂ , Rf ₃ and Rf ₄ may be linked together to form a ring having 4 to 8 carbon atoms, and the ring may be a ring containing an etheric oxygen atom.)

Rf ₁ , Rf ₂ , Rf ₃ and Rf ₄ groups in the residue unit represented by the general formula (1) are each independently a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, a carbon It is one of the group consisting of branched perfluoroalkyl groups having 3 to 7 carbon atoms or cyclic perfluoroalkyl groups having 3 to 7 carbon atoms. The perfluoroalkyl group may have an etheric oxygen atom. Also, Rf ₁ , Rf ₂ , Rf ₃ and Rf ₄ may be linked together to form a ring having 4 or more and 8 or less carbon atoms, and the ring may be a ring containing an etheric oxygen atom. Rf ₁ , Rf ₂ , Rf ₃ , and Rf ₄ in general formula (1) are synonymous with Rf ₅ , Rf ₆ , Rf ₇ , and Rf ₈ in general formula (4) described later, respectively, and will be described below. Specific examples of Rf ₁ , Rf ₂ , Rf ₃ and Rf ₄ are also specific examples of Rf ₅ , Rf ₆ , Rf ₇ and Rf ₈ .

Examples of linear perfluoroalkyl groups having 1 to 7 carbon atoms include trifluoromethyl group, pentafluoroethyl group, heptafluoropropyl group, nonafluorobutyl group, undecafluoropentyl group, tridecafluorohexyl group, A pentadecafluoroheptyl group and the like can be mentioned. Branched perfluoroalkyl groups having 3 to 7 carbon atoms include, for example, heptafluoroisopropyl group, nonafluoroisobutyl group, nonafluorosec-butyl group, nonafluorotert-butyl group and the like. Examples of the cyclic perfluoroalkyl group having 3 to 7 carbon atoms include heptafluorocyclopropyl group, nonafluorocyclobutyl group, tridecafluorocyclohexyl group and the like. Linear perfluoroalkyl groups having 1 to 7 carbon atoms which may have an etheric oxygen atom include, for example, -CF ₂ OCF ₃ group, -(CF ₂ ) ₂ OCF ₃ group, -(CF ₂ ) ₂ OCF ₂ CF ₃ group and the like. Examples of cyclic perfluoroalkyl groups having 3 to 7 carbon atoms and optionally having an etheric oxygen atom include 2-(2,3,3,4,4,5,5,6,6-decafluoro )-pyrinyl group, 4-(2,3,3,4,4,5,5,6,6-decafluoro)-pyrinyl group, 2-(2,3,3,4,4,5,5- heptafluoro)-furanyl group and the like.

at least one of Rf ₁ , Rf ₂ , Rf ₃ and Rf ₄ is a linear perfluoroalkyl group having 1 to 7 carbon atoms, a branched perfluoroalkyl group having 3 to 7 carbon atoms or 3 carbon atoms; A fluororesin that is one of the group consisting of 1 to 7 cyclic perfluoroalkyl groups is preferable from the viewpoint of exhibiting excellent heat resistance.

Specific examples of the residue unit represented by general formula (1) include, for example, residue units represented by the following general formula (2).

Among these, a fluororesin containing a residue unit represented by the following general formula (3) is preferable because of its excellent heat resistance and moldability, and perfluoro(4-methyl-2-methylene-1,3-dioxolane ) fluororesins containing residue units are more preferred.

式（４）中、Ｒｆ ₅ 、Ｒｆ ₆ 、Ｒｆ ₇ 、Ｒｆ ₈ はそれぞれ独立してフッ素原子、炭素数１～７の直鎖状のパーフルオロアルキル基、炭素数３～７の分岐状のパーフルオロアルキル基または、炭素数３～７の環状のパーフルオロアルキル基からなる群の１種を示し、前記パーフルオロアルキル基はエーテル性酸素原子を有していてもよく、また、Ｒｆ ₅ 、Ｒｆ ₆ 、Ｒｆ ₇ 、Ｒｆ ₈ は互いに連結して炭素数４以上８以下の環を形成してもよく、該環はエーテル性酸素原子を含む環であってもよい。式（４）中のＲｆ₅、Ｒｆ₆、Ｒｆ₇、Ｒｆ₈は、式（１）中のＲｆ₁、Ｒｆ₂、Ｒｆ₃、Ｒｆ₄とそれぞれ同義である。 In the polymerization step, a monomer represented by the following general formula (4) is polymerized in the presence of a radical polymerization initiator and a good solvent b for the fluororesin A to obtain a fluororesin represented by the general formula (1) can be obtained.

In formula (4), Rf ₅ , Rf ₆ , Rf ₇ and Rf ₈ are each independently a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, or a branched perfluoroalkyl group having 3 to 7 carbon atoms. one of the group consisting of a fluoroalkyl group or a cyclic perfluoroalkyl group having 3 to 7 carbon atoms, the perfluoroalkyl group optionally having an etheric oxygen atom, and Rf ₅ , Rf ₆ , Rf ₇ and Rf ₈ may be linked together to form a ring having 4 or more and 8 or less carbon atoms, and the ring may be a ring containing an etheric oxygen atom. Rf ₅ , Rf ₆ , Rf ₇ and Rf ₈ in formula (4) are synonymous with Rf ₁ , Rf ₂ , Rf ₃ and Rf ₄ in formula (1).

The polymerization step is a step of polymerizing a monomer represented by the general formula (4) in the presence of a radical polymerization initiator to obtain a fluororesin A containing a residue unit represented by the general formula (1). be. The polymerization method in the polymerization step is not particularly limited, and examples thereof include methods such as solution polymerization, precipitation polymerization, bulk polymerization, emulsion polymerization, and suspension polymerization.

In the production method of the present invention, the monomer represented by general formula (4) is perfluoro(4-methyl-2-methylene-1,3-dioxolane) represented by general formula (8), and It is particularly preferred that the residue unit represented by formula (1) is a perfluoro(4-methyl-2-methylene-1,3-dioxolane) residue unit represented by general formula (9).

Examples of radical polymerization initiators for radical polymerization include bis(perfluorobenzoyl) peroxide (PFBPO), (CF ₃ COO) ₂ , (CF ₃ CF ₂ COO) ₂ and (C ₃ F ₇ COO) _{2 .} , ( _{C4F9COO ) 2} , ( _{C5F11COO ) 2} , ( _{C6F13COO )2 ,} ( _C7F15COO ) ₂ , ( _C8F17COO ) ₂ and _the like _. Peroxide; benzoyl peroxide, lauryl peroxide, octanoyl peroxide, acetyl peroxide, di-tert-butyl peroxide, tert-butyl cumyl peroxide, dicumyl peroxide, tert-butyl peroxyacetate, perfluoro Organic peroxides such as (di-trt-butyl peroxide), bis(2,3,4,5,6-pentafluorobenzoyl) peroxide, tert-butyl peroxybenzoate, tert-butyl perpivalate;2 ,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-butyronitrile), 2,2'-azobisisobutyronitrile, dimethyl-2,2'-azobisisobutyl azo-based initiators such as rate, 1,1′-azobis(cyclohexane-1-carbonitrile), and the like.

The radical polymerization initiator yields a fluororesin with a small heat weight loss, suppresses yellowing after heating and melting, has excellent melt molding processability, excellent defoaming during melting, and cracks during heating and cooling. Perfluoroorganic peroxides are preferred, and bis(perfluorobenzoyl)peroxide (PFBPO) is more preferred, from the viewpoint of reducing the Here, the term "perfluoro organic peroxide" refers to a compound having a structure in which the hydrogen atoms of the organic peroxide are substituted with fluorine atoms.

In the polymerization step, the monomer represented by the general formula (4) is polymerized in the presence of a radical polymerization initiator and a good solvent b for the fluororesin A. The good solvent b for the fluororesin A means an organic solvent capable of dissolving the fluororesin A at 50°C. “Soluble” means that at least part of the fluororesin A having a weight average molecular weight Mw of 5 to 15×10 ⁴ is soluble in the organic solvent. In the case, when the powdery or cotton-like fluororesin A sample is immersed in 20 times the amount (w / w) of an organic solvent at 50 ° C. for 5 hours or more, 80% by weight or more of the fluororesin A sample is at least in the solvent. This solvent can be used as a good solvent if it is partially or wholly soluble. Here, the fluororesin A can be a fluororesin containing a residue unit represented by the general formula (3).

The solvent that can be a good solvent b is preferably at least one selected from the group consisting of perfluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, hydrofluoroethers, hydrofluoroolefins and aromatic fluorine compounds, more preferably perfluorocarbons. Fluorohexane, perfluoro-N-methylmorpholine, perfluoro-N-propylmorpholine, perfluorotriethylamine, perfluoromethyldibutylamine, perfluorotributylamine, CF ₃ CF ₂ CHCl ₂ , CF ₃ CHFCHFCF ₂ CF ₃ , CF _{3 CF2CF2CF2CF2CF2H , CF3 ( CF2 ) 5CH2CH3 , C4F9OCH3 , C4F9OC2H5 , C2F5CF ( OCH3 ) C _ _ _ 3} F ₇ ), preferably at least one of the group consisting of hexafluorobenzene.

For example, perfluorocarbons such as Fluorinert FC-5052, FC-72, FC-770, FC-3283, FC-40, FC-43 (all manufactured by 3M Japan); Asahiklin AK-225 (manufactured by Asahi Glass Co., Ltd.), etc. Hydrochlorofluorocarbons; Vertrel XF (manufactured by Mitsui Chemours), Asahiklin AC-2000, AC-6000 (both manufactured by Asahi Glass Co., Ltd.) Hydrofluorocarbons; Novec7100, Novec7200, Novec7300 (manufactured by 3M Japan) Hydro fluoroethers; hydrofluoroolefins such as Opteon SF10 (manufactured by Mitsui Chemours); aromatic fluorine-containing solvents such as hexafluorobenzene; _{A preferred specific example of the good solvent is Novec7300 (C2F5CF ( OCH3 ) C3F7} , manufactured by 3M Japan Ltd.).

The good solvent is preferably a fluorine-containing solvent, such as hydrofluorocarbons, hydrofluorocarbons, hydrofluorocarbons, hydrofluorocarbons, etc. Aliphatic fluorine-containing solvents having a hydrogen atom in the molecule such as ethers, hydrochlorofluorocarbons and hydrofluoroolefins; A fluorine-containing solvent having a hydrogen atom in the molecule such as an olefin is more preferable, a hydrofluorocarbon or a hydrofluoroether is more preferable, and a hydrofluoroether is particularly preferable. Here, the aliphatic fluorine-containing solvent having hydrogen atoms may be saturated or unsaturated, and may be linear or cyclic.

Conditions in the polymerization process, such as polymerization temperature, polymerization time, concentration of radical polymerization initiator, concentration of monomer, ratio of initiator to monomer, amount of solvent used, etc. It can be appropriately determined in consideration of the types of the polymerization initiator, solvent, and the like. Examples are as follows. The polymerization temperature is, for example, in the range of 30 to 70° C., the polymerization time is, for example, in the range of 5 to 96 hours, and the concentration of the radical polymerization initiator is, for example, 0.1 to 5 mol % with respect to the monomer. The range, monomer concentration, can range, for example, from 5 to 40% by weight relative to the sum of monomer and solvent. However, these numerical ranges are examples and are not intended to be limited to these ranges. In particular, the concentration of the monomer is appropriately determined depending on the type of monomer and the type of solvent, and also considering the solubility of the polymer to be produced in the solvent.

For polymerization, it is preferable to use a chain transfer agent or the like in combination with the monomer and the radical polymerization initiator from the viewpoint of obtaining particles having a high bulk density and excellent handleability as a powder. Although the chain transfer agent is not particularly limited, for example, an organic compound having 1 to 20 carbon atoms and containing at least one atom selected from the group consisting of a hydrogen atom and a chlorine atom can be used. Here, the chain transfer agent is a substance that has the effect of reducing the molecular weight by being present in the system during radical polymerization of the fluororesin. Specific examples of the chain transfer agent include organic compounds having 1 to 20 carbon atoms containing a hydrogen atom such as toluene, acetone, ethyl acetate, tetrahydrofuran, methyl ethyl ketone, methanol, ethanol, isopropanol; chloroform, dichloromethane, tetrachloromethane, chloro C1-C20 organic compounds containing chlorine atoms such as methane, dichloroethane, trichloroethane, tetrachloroethane, pentachloroethane, hexachloroethane, benzyl chloride, pentafluorobenzyl chloride, pentafluorobenzoyl chloride, and the like. Among them, the bulk density is high, particles with excellent handleability as powder can be obtained, the amount of heat weight loss is small, yellowing after heating and melting can be suppressed, and the molecular weight of the fluororesin can be controlled. It is preferably an organic compound having 1 to 20 carbon atoms and containing a chlorine atom from the viewpoint of excellent workability, excellent defoaming properties during melting, less cracking during heating and cooling, and excellent yield. It is more preferably represented by formula (A).

(In formula (A), m is an integer of 0 to 3, n is an integer of 1 to 3, p is an integer of 0 to 1, q is an integer of 0 to 1, and m + n + p + q is 4 R ¹ and R ² are each independently a hydrocarbon group having 1 to 19 carbon atoms or an oxygen atom, and the oxygen atom may form ^a double bond with an adjacent carbon atom. The total number of carbon atoms of ² is 1 to 19, and the hydrocarbon group may have one or more atoms selected from an oxygen atom, a fluorine atom, and a chlorine atom, even if it does not have a hydrogen atom. The hydrocarbon group may be linear, branched, alicyclic, or aromatic, and R ¹ and R ² may be linked together to form a group having 3 carbon atoms. It may form a ring of ~19.)

Among them, the bulk density is high, particles with excellent handleability as powder can be obtained, the amount of heat weight loss is small, yellowing after heating and melting can be suppressed, and the molecular weight of the fluororesin can be controlled. It should be an organic compound having 1 to 20 carbon atoms containing a hydrogen atom and a chlorine atom from the viewpoint of excellent workability, excellent defoaming property during melting, less crack generation during heating and cooling, and excellent yield. More preferred. Examples of organic compounds having 1 to 20 carbon atoms containing hydrogen and chlorine atoms include chloroform, dichloromethane, chloromethane, dichloroethane, trichloroethane, tetrachloroethane, pentachloroethane, benzyl chloride, and pentafluorobenzyl chloride. In addition, in the organic compound having 1 to 20 carbon atoms containing a hydrogen atom and a chlorine atom, particles having a high bulk density and excellent handleability as a powder can be obtained, the amount of heat weight loss is small, and after heating and melting It is possible to control the molecular weight of the fluororesin while suppressing yellowing, and it has excellent melt molding processability, excellent defoaming properties during melting, less crack generation during heating and cooling, and excellent yield. and chlorine atoms in a number ratio of hydrogen atoms:chlorine atoms=1:9 to 9:1, more preferably 1:9 to 5:5. In addition, it is possible to obtain particles with high bulk density and excellent handleability as powder, small heat weight loss, suppress yellowing after heating and melting, control the molecular weight of fluororesin, and melt molding process. From the standpoint of excellent heat resistance, excellent defoaming properties during melting, little cracking during heating and cooling, and excellent yield, the organic compound having 1 to 20 carbon atoms containing a hydrogen atom and a chlorine atom has the following general formula: It is preferably represented by (B) or (C), more preferably represented by general formula (B).

（式（Ｂ）中、ｍ、ｎはそれぞれ独立して１～３の整数であり、ｐは０～１の整数であり、ｑは０～１の整数であり、ｍ＋ｎ＋ｐ＋ｑは４である。Ｒ¹及びＲ²はそれぞれ独立して炭素数１～１９の炭化水素基であり、Ｒ¹ _p及びＲ² _qの炭素数の合計は０～１９であり、前記炭化水素基は酸素原子、フッ素原子、塩素原子から選ばれる１以上の原子を有していても良く、水素原子を有していなくても良い。また炭化水素基は直鎖状であっても、分岐状であっても、脂環状であっても、芳香環状であっても良く、Ｒ¹及びＲ²が互いに連結して炭素数３～１９の環を形成していても良い。）

(In formula (B), m and n are each independently an integer of 1 to 3, p is an integer of 0 to 1, q is an integer of 0 to 1, and m + n + p + q is 4. R ¹ and R ² are each independently a hydrocarbon group having 1 to 19 carbon atoms, the total number of carbon atoms of R ¹ _p and R ² _q is 0 to 19, and the hydrocarbon group is an oxygen atom or a fluorine atom. , Chlorine atoms, and may have no hydrogen atoms.The hydrocarbon group may be linear or branched, and may be lipophilic. It may be cyclic or aromatic, and R ¹ and R ² may be linked together to form a ring having 3 to 19 carbon atoms.)

(In formula (C), m, n, u and v are each independently an integer of 0 to 3, m+u is 1 to 5, n+v is 1 to 5, p, q, r, s , t are each independently an integer of 0 to 1, m+n+p+q is 3, r+s+u+v is 3, and R ¹ , R ² , R ³ , R ⁴ and R ⁵ each independently have 1 to 1 carbon atoms. 18 hydrocarbon groups, the total number of carbon atoms in R ¹ , R ² , R ³ , R ⁴ and R ⁵ is 0 to 18, and the hydrocarbon group is selected from oxygen, fluorine and chlorine atoms. It may have one or more atoms, it may have no hydrogen atoms, and the hydrocarbon group may be linear, branched, or alicyclic, It may be an aromatic ring, and two or more groups selected from R ¹ , R ² , R ³ , R ⁴ and R ⁵ may be linked together to form a ring having 3 to 19 carbon atoms. There may be multiple rings.)

Examples of the organic compound having 1 to 20 carbon atoms containing a chlorine atom represented by general formula (A) include chloroform, dichloromethane, tetrachloromethane, chloromethane, dichloroethane, trichloroethane, tetrachloroethane, pentachloroethane, hexachloroethane, and benzyl. chloride, pentafluorobenzyl chloride, pentafluorobenzoyl chloride and the like. Examples of the organic compound having 1 to 20 carbon atoms containing a hydrogen atom and a chlorine atom represented by the general formula (B) include chloroform, dichloromethane, chloromethane, dichloroethane, trichloroethane, tetrachloroethane, pentachloroethane, benzyl chloride, and pentafluoro. benzyl chloride and the like. Examples of the organic compound having 1 to 20 carbon atoms containing a hydrogen atom and a chlorine atom represented by general formula (C) include 1,1,1-trichloroethane and the like.

In addition, particles with high bulk density and excellent handleability as powder can be obtained, the amount of weight loss on heating is small, and while yellowing after heating and melting is suppressed, defoaming and crack generation are compatible during melting. In addition, a fluororesin having excellent defoaming properties and heat resistance when melted, a low melt viscosity, and less cracking can be obtained, and the yield is also excellent. It is preferably 0.01 to 95% by weight, more preferably 1 to 50% by weight, even more preferably 3 to 50% by weight, based on the total amount of the monomer and the chain transfer agent.

In the precipitation step, the poor solvent c for the fluororesin A is added to the fluororesin A solution containing the fluororesin A containing the fluorine-containing alicyclic structure and the good solvent b to precipitate the fluororesin A.

The poor solvent c for ^the fluororesin A means a solvent in which the fluororesin A is difficult to dissolve. When immersed in a solvent at 50° C. for 5 hours or more and cooled to 25° C., the amount of fluororesin A dissolved in the solvent is less than 20% by weight, preferably less than 10% by weight. can be done. Furthermore, in the present invention, the poor solvent for the fluororesin A is also a solvent capable of precipitating the fluororesin A from a fluororesin A solution in which the fluororesin is dissolved in a good solvent. The poor solvent is preferably a solvent in which the fluororesin A precipitates when a solution obtained by dissolving the fluororesin A in a certain good solvent is added dropwise at 25° C. to a solvent 10 times the amount of the good solvent. Here, the fluororesin A can be a fluororesin containing a residue unit represented by the general formula (3).

Solvents that can be the poor solvent c include, for example, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 2,2,2-trifluoroethanol, 1,1,1, 3,3,3-hexafluoroisopropanol, 1,2,2,3,3,4,4-heptafluorocyclopentane, 1H,1H-pentafluoropropanol, 1H,1H-heptafluorobutanol, 2-perfluorobutyl Ethanol, 4,4,4-trifluorobutanol, 1H,1H,3H-tetrafluoropropanol, 1H,1H,5H-octafluoropropanol, 1H,1H,7H-dodecafluoroheptanol, 1H,1H,3H-hexa Fluorobutanol, 2,2,3,3,3-pentafluoropropyldifluoromethyl ether, 2,2,3,3,3-pentafluoropropyl-1,1,2,2-tetrafluoroethyl ether, 1,1 , 2,2-tetrafluoroethyl ethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, hexafluoroisopropyl methyl ether, 1,1,3,3, 3-pentafluoro-2-trifluoromethylpropyl methyl ether, 1,1,2,3,3,3-hexafluoropropyl methyl ether, 1,1,2,3,3,3-hexafluoropropyl ethyl ether, fluorine-containing solvents having a hydrogen atom in the molecule such as 2,2,3,4,4,4-hexafluorobutyldifluoromethyl ether; hexane, heptane, toluene, acetone, methanol, ethanol, isopropanol, ethyl acetate, methyl ethyl ketone, At least one selected from the group consisting of fluorine-free organic solvents such as methyl isobutyl ketone, tetrahydrofuran, chloroform, dichloromethane, dichloroethane, and trichloroethane.

The poor solvent is preferably a fluorine-containing solvent, since a fluororesin with excellent productivity, high bulk density, excellent handleability as a powder, and small weight loss on heating can be obtained. Fluorine-containing solvents having atoms such as 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 2,2,2-trifluoroethanol, More preferred is at least one of the group consisting of 1,3,3,3-hexafluoroisopropanol and 1,2,2,3,3,4,4-heptafluorocyclopentane. From the viewpoint of economy, the poor solvent is a fluorine-free organic solvent such as hexane, heptane, toluene, acetone, methanol, ethanol, isopropanol, ethyl acetate, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, chloroform, dichloromethane, dichloroethane, trichloroethane. Solvents are preferred.

Whether a certain solvent is a good solvent or a poor solvent can also be evaluated by checking whether the polarity of the organic solvent is within a specific range. Specifically, based on the Hansen solubility parameters, solvents with a certain range of polarity can be good solvents or poor solvents. However, if the definition/judgment method differs from the above-mentioned good solvent or poor solvent, the classification according to the above definition/judgment method is positive.

The Hansen solubility parameter is the solubility parameter introduced by Hildebrand divided by Hansen into three components, the dispersion term δD, the polar term δP, and the hydrogen bonding term δH, and shown in three-dimensional space. be. The dispersion term δD indicates the effect of the dispersion force, the polar term δP indicates the effect of the dipole force, and the hydrogen bonding term δH indicates the effect of the hydrogen bonding force. In a three-dimensional space, the more apart the coordinates of a resin and the coordinates of a solvent are, the more difficult the resin is to dissolve in the solvent.

The definition and calculation method of the Hansen Solubility Parameter are described in the following references. Charles M. Hansen, "Hansen Solubility Parameters: A Users Handbook," CRC Press, 2007. For solvents for which literature values are not known, Hansen Solubility Parameters can be easily estimated from their chemical structures by using computer software (Hansen Solubility Parameters in Practice (HSPiP)).

In the present invention, HSPiP 5th Edition is used, and the values are used for organic solvents registered in the database, and estimated values are used for organic solvents that are not registered.

The Hansen Solubility Parameter of a resin can be determined by adding a solution of the resin in a good solvent to a number of different solvents with established Hansen Solubility Parameters to see if the resin dissolves. Specifically, when the coordinates of the Hansen solubility parameters of all the solvents used in the test are shown in a three-dimensional space, all the coordinates of solvents in which the solubility of resin A is 80% by weight or more are included inside the sphere, and the resin A sphere (solubility sphere) is found such that the coordinates of the solvent in which the solubility of A is less than 20% by weight are outside the sphere, and the center coordinates of the solubility sphere are taken as the Hansen solubility parameter of the resin.

Then, if the coordinates of the Hansen solubility parameters of a solvent that was not used in the solubility test are (δD, δP, δH), the organic solvent is a good solvent if the coordinates are contained inside the solubility sphere. It is believed that there is. On the other hand, if the coordinates lie outside the solubility sphere, the organic solvent is considered to be a poor solvent.

The Hansen solubility parameter of the resin containing the perfluoro(4-methyl-2-methylene-1,3-dioxolane) residue unit represented by the general formula (5) in the present invention is represented by the following general formula (6). Hansen solubility parameter of the compound represented by the general formula (5) (pentamer of the compound represented by the general formula (5)), using the value estimated using HSPiP, estimated Hansen solubility of the compound represented by the general formula (6) The parameters δD, δP and δH were 11.6, 3.5 and 1.4 (MPa ^1/2 ) respectively.

(In formula (6), Rf ₉ , Rf ₁₀ , Rf ₁₁ and Rf ₁₂ are each independently a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, a branched perfluoroalkyl group having 3 to 7 carbon atoms, represents one of the group consisting of a perfluoroalkyl group or a cyclic perfluoroalkyl group having 3 to 7 carbon atoms, the perfluoroalkyl group optionally having an etheric oxygen atom, and Rf ₉ , Rf ₁₀ , Rf ₁₁ and Rf ₁₂ may be linked together to form a ring having 4 to 8 carbon atoms, which may be a ring containing an etheric oxygen atom).

Then, when the solubility index R with the resin calculated by the formula (7) from the Hansen solubility parameter is obtained, the solubility index R of the good solvent is preferably less than 4, and the solubility index R of the poor solvent is is preferably 4 or more.
R=4×{(δD ₁ −δD ₂ ) ² +(δP ₁ −δP ₂ ) ² +(δH ₁ −δH ₂ ) ² } ^0.5 (7)
Here, δD ₁ , δP ₁ , δH ₁ are the dispersion _term , the polar _term and the hydrogen term of the _Hansen solubility parameter of the resin particles, respectively; term and hydrogen term.

Examples of solvents having an affinity Ra of 4 or more for resins containing perfluoro(4-methyl-2-methylene-1,3-dioxolane) residue units include the following organic solvents.

In the precipitation step, the fluororesin A solution contains a poor solvent c for the fluororesin A solution from the viewpoint of obtaining particles having a high bulk density and excellent handleability as a powder and obtaining a resin with a small amount of weight loss on heating. is added to precipitate the fluororesin A.

In the precipitation step, particles of the fluororesin A are preferably precipitated by adding the poor solvent c for the fluororesin A to the fluororesin A solution containing the fluororesin A and the good solvent b while stirring.

It is excellent in productivity, prevents mutual adhesion of particles, has a high bulk density, provides particles excellent in handleability as a powder, and provides a fluororesin with a small amount of weight loss on heating. The weight ratio of good solvent b: poor solvent c after mixing is preferably in the range of 1:99 to 90:10, more preferably 1:99 to 70:30, and 1:99 to 50:50. More preferably, 3:97 to 60:40 is even more preferable.

Stirring is excellent in productivity, prevents mutual adhesion of particles, gives particles with high bulk density and excellent handleability as powder, and obtains fluororesin with small heat weight loss. Stirring is preferably performed at a Pv value of 0.05 to 50 kw/m ³ which is the value of the agitator motor power per capacity. The Pv value is more preferably 0.2 to 50 kW/m ³ , still more preferably 0.5 to 30 kW/m ³ and even more preferably 0.5 to 10 kW/m ³ . Here, the Pv value (kW/m ³ ) can be calculated by the following formula (10).

（ここで、Ｎｐ：動力数、ρ：溶液の密度（ｋｇ／ｍ³）、ｎ：撹拌翼の回転数（ｒｐｍ）、ｄ：撹拌翼の直径（ｍｍ）、Ｖ：溶液量（Ｌ）を表す。）

(Here, Np: power number, ρ: density of solution (kg/m ³ ), n: rotation speed of stirring blade (rpm), d: diameter of stirring blade (mm), V: amount of solution (L) show.)

Np in Equation (10) is a dimensionless number called power number, which varies depending on the shape of the stirring blade. This Np is obtained from known documents such as "Kagaku Kiseki, August 1995, pp. 71-79" and "Shinko Faudler Giho vol.28, No. 8 (October 1984), pp. 13-16". be able to. At this time, when the ratio b/d of the blade width b to the stirring blade diameter d is different from that described in the literature, it can be calculated by the following formula (11).

Actual Np = Literature Np x (Actual b/d)/(Literature b/d) (11)
(Here, Np: power number, b: width of stirring blade (mm), d: diameter of stirring blade (mm).)

In the fluororesin A solution obtained in the precipitation step, in which the resin is precipitated, mutual adhesion of the obtained resin is prevented, and a resin excellent in handleability as a powder is obtained, so the poor solvent c is added. It is preferable to perform a poor solvent addition step. The amount of the poor solvent c added in the poor solvent addition step is excellent in productivity, prevents mutual adhesion of particles, and gives a resin with excellent handleability as a powder, so the fluororesin obtained in the precipitation step The amount of the poor solvent c added is preferably 0.1 times or more, more preferably 0.5 times or more and 1 time or more, relative to the weight of the A-containing solution. The poor solvent c used in the poor solvent addition step may be the same as or different from the poor solvent c used in the precipitation step.

In the present invention, any other step may be added, and a separation step of removing a solid by solid-liquid separation may be included after the precipitation step or the poor solvent addition step. The solid-liquid separation method is not particularly limited, but examples thereof include pressure filtration, vacuum filtration, centrifugation, and centrifugal filtration. Although the size of the filter to be used is not limited, for example, a filter having a capture particle size of 30 μm or less can be used. The material of the filter to be used is not limited, but examples thereof include polypropylene, polyethylene, polyethylene terephthalate, nylon, PTFE, and PES.

In the present invention, any other process may be added, and a washing process for washing the particles of the fluororesin A and/or a drying process for drying may be included. In the washing step, it is preferable to use a poor solvent c, and the poor solvent c is preferably an organic solvent that allows the fluororesin A to precipitate at 25°C. The drying method is not particularly limited, and examples thereof include vacuum drying, reduced pressure drying, normal pressure drying, air drying, shaking drying, warm air drying, heat drying and the like. The poor solvent c used in the drying step may be the same as or different from the poor solvent c used in the poor solvent addition step and the poor solvent c used in the precipitation step.

The fluororesin obtained by the production method of the present invention has a bulk density of, for example, 0.25 to 1.5 g/cm ³ . is preferable from the viewpoint of obtaining a fluororesin having a small The bulk density is more preferably 0.30 to 1.0 g/cm ³ and even more preferably 0.35 to 0.7 g/cm ³ . Bulk density measurements are carried out as follows. Weigh and put fluororesin A into a glass sample tube with a volume of 13.5 mL (liquid level height is 2.8 cm when 10 mL of water is added) whose height per unit volume has been measured in advance, and the powder at that time. The bulk density was calculated from the height and the weight of the powder according to the following formula.
Bulk density = (weight of powder (g)) / ((height of powder (cm) / 0.28 (cm / mL))

The fluororesin obtained by the production method of the present invention has high fluidity, can be continuously supplied to a molding machine, etc., has a high bulk density, and has a small amount of heat weight loss. The particle size is preferably 5 μm to 2000 μm, more preferably 5 μm to 1000 μm, even more preferably 5 μm to 500 μm. The 90% particle size of the fluororesin obtained by the production method of the present invention is preferably 2,500 μm or less, more preferably 2,000 μm or less, and more preferably 1,000 μm or less, since the fluidity and moldability are further improved.

The fluororesin obtained by the production method of the present invention has a low content of fine particles, is further prevented from dusting, and has improved fluidity, so it is preferable that the 10% particle diameter is 3 μm or more. .

The volume average particle size, 90% particle size, 10% particle size, and particle size distribution of the fluororesin obtained by the production method of the present invention can be evaluated by particle size distribution measurement (volume distribution) by a laser diffraction scattering method. can. The particle size distribution by the laser diffraction scattering method can be measured by dispersing the resin particles in water or an organic solvent such as methanol. As a laser scatterometer, Microtrac manufactured by Microtrac Bell Co., Ltd. can be exemplified.

The volume average particle size, also called Mean Volume Diameter, is the average particle size expressed on a volume basis. It is represented by Σ(vd)/Σ(v), where v is the volume-based percentage for each particle size channel.

The 10% particle size means the particle size at the point where the cumulative amount is 10% when the total volume of the powder mass is 100% and the cumulative amount is calculated. The 90% particle size means the particle size at the point where the cumulative amount is 90% when the cumulative amount is calculated with the total volume of the powder mass being 100%.

Since the fluororesin obtained by the production method of the present invention becomes resin particles that are difficult to foam during molding, the weight loss when heated at 250 ° C. is preferably 1% by weight or less, and 0.5% by weight or less. is preferred. Also, the minimum amount of weight loss when heated to 250° C. is not particularly limited, but for example, 0.001% by weight or more can be exemplified. In addition, since the resin particles of the present invention are resin particles that are difficult to foam during molding, the amount of residual solvent contained in the resin is preferably 1% by weight or less, and 0.5% by weight or less. is preferred. Here, the amount of weight loss when heated to 250° C. means the amount of weight loss at 250° C. when the temperature is raised from 40° C. at 10° C./min under an air current using TG-DTA. (Sample weight at 250° C.)/(weighed sample weight))×100).

The fluororesin obtained by the production method of the present invention has excellent productivity, prevents mutual adhesion of particles, has a high bulk density, gives particles excellent in handleability as powder, and has a small amount of weight loss on heating. From the viewpoint of obtaining a fluororesin, the weight average molecular weight is preferably 5×10 ⁴ to 5×10 ⁵ . More preferably, the weight average molecular weight Mw is in the range of 5×10 ⁴ to 3×10 ⁵ . When the weight average molecular weight Mw is within this range, the melt viscosity at a shear rate of 10 ⁻² s and 250° C. can be 1×10 ² to 3×10 ⁵ Pa·s. Excellent for Furthermore, it is also excellent in defoaming properties during melting. In addition, when the weight average molecular weight Mw is within this range, cracks are less likely to occur during heating and cooling. The fluororesin of the present invention is excellent in productivity, prevents mutual adhesion of particles, has a high bulk density, gives particles excellent in handleability as powder, and provides a fluororesin with a small weight loss on heating. The weight average molecular weight Mw is preferably in the range of 5×10 ⁴ to 2×10 ⁵ from the viewpoint of excellent melt moldability and excellent defoaming property when melted, and the weight average molecular weight Mw is within this range. At a shear rate of 10 ^-2 s, the melt viscosity at 250 ° C. can be 1 × 10 ² to 2 × 10 ⁴ Pa s. Therefore, it is preferable. It has excellent productivity, prevents mutual adhesion of particles, has high bulk density, provides particles with excellent handling properties as powder, obtains fluororesin with small heat weight loss, and has excellent melt molding processability. The weight average molecular weight Mw is more preferably in the range of 5×10 ⁴ to 1.5×10 ⁵ from the viewpoint of excellent defoaming properties during melting.

The weight average molecular weight Mw of the fluororesin of the present invention can be determined using gel permeation chromatography (GPC), for example, standard polymethyl methacrylate with a known molecular weight as a standard sample, and both the standard sample and the fluororesin as an eluent. Using a solvent, it can be calculated from the elution times of the sample and standard sample, and the molecular weight of the standard sample. As the solution, Asahiklin AK-225 (manufactured by Asahi Glass Co., Ltd.) and 10 wt% of 1,1,1,3,3,3-hexafluoro-2-propanol (Wako Pure Chemical) with respect to AK-225 (manufactured by industry) can be mentioned.

Hereinafter, the present invention will be described in more detail based on examples. However, the examples are illustrative of the present invention, and the present invention is not intended to be limited to the examples.

<Physical property measurement method>
(1) Weight average molecular weight Mw
Measurement was performed using gel permeation chromatography equipped with a column TSKgel SuperHZM-M manufactured by Tosoh Corporation and an RI detector. Asahiklin AK-225 (manufactured by Asahi Glass Co., Ltd.) was used as an eluent, and 10 wt% of 1,1,1,3,3,3-hexafluoro-2-propanol (manufactured by Wako Pure Chemical Industries, Ltd.) was added to AK-225. was used. Using Agilent's standard polymethyl methacrylate as a standard sample, the weight average molecular weight Mw in terms of polymethyl methacrylate was calculated from the elution times of the sample and the standard sample.

(2) Measurement of volume average particle size, 10% particle size, and 90% particle size Using Microtrac MT3000 manufactured by Microtrac Bell Co., Ltd., using methanol as a dispersion medium Volume average particle size (unit: μm ), 10% particle size, and 90% particle size were measured.

（ここで、Ｎｐ：動力数、ρ：溶液の密度（ｋｇ／ｍ³）、ｎ：撹拌翼の回転数（ｒｐｍ）、ｄ：撹拌翼の直径（ｍｍ）、Ｖ：溶液量（Ｌ）を表す。）。 (3) Calculation of Pv value The Pv value, which is the value of the stirrer motor power per unit stirring capacity, was calculated using the following formula. An Np of 4.2 was used when four diagonal paddle stirring blades (blade diameter: 50 mm, oblique angle: 45°) were used.

(Here, Np: power number, ρ: density of solution (kg/m ³ ), n: rotation speed of stirring blade (rpm), d: diameter of stirring blade (mm), V: amount of solution (L) show.).

(4) Calculation of bulk density Fluororesin A was weighed into a glass sample tube with a volume of 13.5 mL (liquid level height of 2.8 cm when 10 mL of water was added) whose height per unit volume was measured in advance. From the height and weight of the powder at that time, the bulk density was calculated according to the following formula.
Bulk density = (weight of powder (g)) / ((height of powder (cm) / 0.28 (cm / mL))

(5) Calculation of weight loss after heating at 250° C. About 10 to 15 mg of sample is weighed into an aluminum sample pan (SSC000E030 manufactured by Hitachi High-Tech Science Co., Ltd.), and a TG / DTA device (TG / DTA6200AST2 manufactured by Hitachi High-Tech Science Co., Ltd.) ), the temperature was raised from 40 ° C. to 300 ° C. at 10 ° C./min under an instrument air stream (160 mL / min), and the weight loss at 250 ° C. (1-(sample weight at 250 ° C.) / (weighed The weight of the sample))×100) was obtained and used as the amount of weight loss on heating at 250°C.

Example 1
0.173 g (0.000410 mol) of bis(2,3,4,5,6-pentafluorobenzoyl) peroxide as an initiator and perfluoro(4-methyl-2- methylene-1,3-dioxolane) 20.0 g (0.0820 mol), Novec 7300 (manufactured by 3M Japan Ltd., C ₂ F ₅ CF (OCH ₃ )C ₃ F ₇ ) 80.00 g as a polymerization solvent, chain transfer agent 2.22 g (0.0186 mol) of chloroform (manufactured by Wako Pure Chemical Industries, Ltd.) was added, and after repeating nitrogen replacement and pressure release by freezing and degassing, sealing was performed under reduced pressure (monomer/solvent = 20/80 ( wt/wt)). This ampoule was placed in a constant temperature bath at 55° C. and held for 24 hours to carry out radical solution polymerization. As a result, a viscous liquid in which the resin was dissolved was obtained. After cooling to room temperature, the ampoule was opened, and the resin solution was diluted with 100 g of Novec 7300 to adjust the viscosity to prepare a diluted resin solution (solid concentration: 10% by weight).

This solution was transferred to a separable flask with a capacity of 1000 mL equipped with four diagonal paddle stirring blades (blade diameter 50 mm, blade width 12 mm, slant 45°), three-one motor, and water bath, and stirred at 600 rpm (Pv value: 20. 6 kw/m ³ ) and 420 g of Zeorora H (1,2,2,3,3,4,4-heptafluorocyclopentane manufactured by Nippon Zeon Co., Ltd.) was slowly added to obtain a particulate solid (Zeorolla H /Novec7300 = 70/30 (wt/wt), Pv value after completion of addition: 6.1 kw/m ³ ). Particles of fluororesin A were obtained by suction filtration, washing with acetone twice, and vacuum drying under heating. The obtained resin was fine particles having a volume average particle size of 92 μm, a 10% particle size of 19 μm, and a 90% particle size of 198 μm, and had almost no coarse particles. The weight average molecular weight Mw of the obtained fluororesin was 7.9×10 ⁴ . Table 2 shows the evaluation results of the fluororesin.

Comparative example 1
It was carried out according to the description of Sample 93 in Table 2 of Non-Patent Document 1. However, since there was no description of the polymer concentration during reprecipitation purification, the polymer was diluted to 10 wt %. 0.0880 g (0.000209 mol) of bis(2,3,4,5,6-pentafluorobenzoyl) peroxide as an initiator and perfluoro(4-methyl-2- 20.0 g (0.0820 mol) of methylene-1,3-dioxolane) and 32.63 g of hexafluorobenzene as a polymerization solvent were added, and after repeated nitrogen replacement and pressure release by freeze degassing, the mixture was sealed under reduced pressure ( monomer/solvent=38/62 (wt/wt)). This ampoule was placed in a constant temperature bath at 60° C. and held for 24 hours to carry out radical solution polymerization. As a result, a viscous liquid in which the resin was dissolved was obtained. After cooling to room temperature, the ampoule was opened, and the resin solution was diluted with 147 g of hexafluorobenzene for viscosity adjustment to prepare a diluted resin solution. Put 1 L of chloroform in a beaker equipped with an anchor wing, add the resin diluted solution to the beaker under stirring to precipitate the resin, collect the precipitated resin by filtration, and then vacuum dry it to obtain an amorphous par A fluoro(4-methyl-2-methylene-1,3-dioxolane) resin was obtained. When the size of the obtained fluororesin was measured with a ruler, the size was about 10 mm. The weight average molecular weight Mw of the obtained fluororesin was 3.7×10 ⁵ . Table 2 shows the evaluation results of the fluororesin.

Reference example 1
0.173 g (0.000410 mol) of bis(2,3,4,5,6-pentafluorobenzoyl) peroxide as an initiator and perfluoro(4-methyl-2- methylene-1,3-dioxolane) 20.0 g (0.0820 mol), Novec 7300 (manufactured by 3M Japan Ltd., C ₂ F ₅ CF (OCH ₃ )C ₃ F ₇ ) 80.00 g as a polymerization solvent, chain transfer agent 2.22 g (0.0186 mol) of chloroform (manufactured by Wako Pure Chemical Industries, Ltd.) was added, and after repeating nitrogen replacement and pressure release by freezing and degassing, sealing was performed under reduced pressure (monomer/solvent = 20/80 ( wt/wt)). This ampoule was placed in a constant temperature bath at 55° C. and held for 24 hours to carry out radical solution polymerization. As a result, a viscous liquid in which the resin was dissolved was obtained. After cooling to room temperature, the ampoule was opened, and the resin solution was diluted with 100 g of Novec 7300 to adjust the viscosity to prepare a diluted resin solution (solid concentration: 10% by weight). 2 L of acetone is placed in a plastic cup equipped with an anchor wing, and the diluted resin solution that has undergone pressure filtration is added to the beaker while stirring to precipitate the resin. A powdery perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin was obtained by repeating and vacuum drying. The weight average molecular weight Mw of the obtained fluororesin was 5.2×10 ⁴ . Table 1 shows the evaluation results of the fluororesin.

Reference example 2
The fluororesin A (weight average molecular weight Mw = 7.9 × 10 ⁴ ) prepared in Example 1 was immersed in various organic solvents of 20 times the amount (w/w) of the fluororesin A at 50°C for 5 hours or more to dissolve. When it was confirmed by visual inspection, the following results were obtained.
Dissolves: FC-72, FC-770, Novec 7200, Novec 7300, hexafluorobenzene. When the solutions dissolved in these solvents were cooled to 25°C, all of them remained dissolved. All of them had almost no undissolved residue and had a solubility of 90 wt % or more.
Not soluble: Zeorora H, AE-3000, trifluoroethanol, ethyl acetate, chloroform, acetone, hexane. In both cases, after cooling to 25° C., filtration and drying, the recovery rate of fluororesin A exceeded 80%, and the solubility was less than 20 wt %.

Reference example 3
Fluororesin A (weight average molecular weight Mw = 7.9 × 10 ⁴ ) was dissolved in Novec 7300 at a solid content concentration of 10% by weight. When it was added dropwise to , it was visually confirmed whether a solid precipitated, and the following results were obtained.
No solids precipitated: FC-72, FC-770, Novec7200, Novec7300, hexafluorobenzene. All of them had no precipitates and had a solubility of 90 wt % or more.
A solid precipitated out: Zeorora H, AE-3000, trifluoroethanol, ethyl acetate, chloroform, acetone, hexane. In both cases, the recovery rate of fluororesin A after filtration and drying exceeded 80%, and the solubility was less than 20 wt%.

INDUSTRIAL APPLICABILITY The present invention is useful in fields related to fluororesins.

Claims (7)

a polymerization step of polymerizing a monomer containing a fluorine-containing alicyclic structure in the presence of a radical polymerization initiator to obtain a fluororesin A represented by the following general formula (1) containing a fluorine-containing alicyclic structure; For a fluororesin A solution containing a fluororesin A containing a fluorine- containing alicyclic structure and a hydrofluoroether which is a good solvent b in which 80% by weight or more of the fluororesin A is completely dissolved , a poor solvent c for the fluororesin A is added. provided that the poor solvent c has a solubility index R of 4 or more, and a method for producing a fluororesin containing a fluorine-containing alicyclic structure (provided that the fluororesin is —SO ₂ F groups) .

(In formula (1), Rf ₁ , Rf ₂ , Rf ₃ and Rf ₄ are each independently a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, a branched perfluoroalkyl group having 3 to 7 carbon atoms, represents one member of the group consisting of a perfluoroalkyl group or a cyclic perfluoroalkyl group having 3 to 7 carbon atoms, the perfluoroalkyl group optionally having an etheric oxygen atom, and Rf ₁ , Rf ₂ , Rf ₃ and Rf ₄ may be linked together to form a ring having 4 to 8 carbon atoms, and the ring may be a ring containing an etheric oxygen atom.) In the polymerization step, a monomer represented by the following general formula (4) is polymerized in the presence of a radical polymerization initiator and a hydrofluoroether, which is a good solvent b for the fluororesin A, to obtain a general formula (1) The method for producing a fluororesin according to claim 1 , wherein the fluororesin represented by is obtained.

(In formula (4), Rf ₅ , Rf ₆ , Rf ₇ and Rf ₈ are each independently a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, a branched perfluoroalkyl group having 3 to 7 carbon atoms, represents one member of the group consisting of a perfluoroalkyl group or a cyclic perfluoroalkyl group having 3 to 7 carbon atoms, the perfluoroalkyl group optionally having an etheric oxygen atom, and Rf ₅ , Rf ₆ , Rf ₇ and Rf ₈ may be linked together to form a ring having 4 or more and 8 or less carbon atoms, and the ring may be a ring containing an etheric oxygen atom.) The precipitating step is a step of precipitating particles of the fluororesin A by adding the poor solvent c for the fluororesin A to the fluororesin A solution containing the fluororesin A and the hydrofluoroether as the good solvent b, while stirring. A method for producing a fluororesin according to any one of claims 1 and 2 . 4. The method for producing a fluororesin according to claim 3 , wherein the stirring is performed at a Pv value of 0.05 to 50 kw/m ³ , which is a value of power of the stirrer motor per unit stirring capacity. 5. The method for producing a fluororesin according to claim 1, wherein the fluororesin obtained in the precipitation step has a bulk density of 0.25 to 1.5 g/cm ³ . The method for producing a fluororesin according to any one of claims 1 to 5 , wherein the fluororesin obtained in the precipitation step has a volume average particle size of 5 to 2000 µm. 7. The method for producing a fluororesin according to claim 1, wherein the fluororesin obtained in the precipitation step has a weight average molecular weight of 5 × 10 ⁴ to 3×10 ⁵ .

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