JP2701080B2 - Method for producing peroxide-curable fluoroelastomer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a method for producing a peroxide-curable fluoroelastomer. More specifically, the present invention provides a suspension-polymerized fluoroelastomer which has peroxide-vulcanizable by having a bonding iodine atom serving as a cross-linking point in a molecule, and is excellent in vulcanization characteristics and vulcanization properties. A more efficient manufacturing method.

Conventional technology Conventional fluorine-containing elastomers have excellent heat resistance, solvent resistance, chemical resistance, etc., and are used under particularly severe conditions such as O-rings, oil seals, packing, gaskets and other sealing materials. Used in diaphragms, hose linings, coatings, adhesives, etc.

Also, various vulcanization methods such as polyamine vulcanization, polyol vulcanization, and peroxide vulcanization are known for the fluorine-containing elastomer, and an optimum vulcanization method is selected according to the application. Among them, it is known that a peroxide vulcanization method using an organic peroxide can provide a material having excellent steam resistance, acid resistance, alkali resistance, amine resistance and the like. As the fluorinated elastomer in this case, one having iodine or bromine bonded as a cross-linking point is used, and until now, the general formula Rf.Ix (where Rf is a fluorohydrocarbon group or a chlorofluorohydrocarbon group) A method using an iodine compound represented by the formula (JP-A-53-125491)
JP-A-60-221409, a method using an iodine compound represented by the general formula R.Ix (where R is a hydrocarbon group having 1 to 3 carbon atoms), (Japanese Patent Application Laid-Open (JP-A) No. 232407/1987), a method using an iodine- or bromine-containing peroxide (Japanese Patent Application Laid-Open (JP-A) No. 63-23907), a peroxide-curable fluorine-containing fluorine containing bromine Polymer (JP-B-53-4115),
A method using a bromine compound represented by the general formula R.Brx (where R is a saturated aliphatic hydrocarbon group)
No. 20310) has been proposed.

Such fluorine-containing elastomers which can be vulcanized with peroxide include bromine type and iodine type as crosslinking points, all of which have been put to practical use. Among these, the carbon-bromine bond, which is a cross-linking point, has a larger bond energy than the carbon-iodine bond, so the peroxide vulcanization rate is slow, the degree of vulcanization is small, and the elongation is relatively small even in mechanical properties. It has disadvantages such as large compression set.

On the other hand, a fluorine-containing elastomer obtained by bonding iodine obtained by using an iodine compound as a chain transfer agent (Japanese Unexamined Patent Publication No.
No. 125491, JP-A-60-221409, etc.) mainly have iodine bonded to the polymer terminal, and the terminal portion mainly contributes to the vulcanization reaction, so that the peroxide vulcanization rate is high and the degree of vulcanization is high. In addition, an excellent vulcanizate having a relatively large elongation and a small compression set can be obtained.

As an iodine compound used as a chain transfer agent, it is known that R.Ix is more excellent in terms of toxicity and economy (JP-A-60-221409).

As a method for polymerizing such a fluoroelastomer, an emulsion polymerization method is generally used, and the number of cases in which a suspension polymerization method is used has been extremely rare. The suspension polymerization method does not require a salting-out step, which is essential in the emulsion polymerization method, so that the process is simplified and there are advantages that a salting-out agent is not mixed into the obtained fluorine-containing elastomer. This is an industrially advantageous process.

The present inventors have repeated studies on a method for producing a peroxide-curable fluoroelastomer by such a suspension polymerization method, and have previously found an effective method (JP-A-1-319512). The vulcanizate properties of the resulting fluoroelastomer, especially the compression set characteristics when used as a sealing material, were not always satisfactory.

Problem to be Solved by the Invention Under such circumstances, the present invention sufficiently maintains the good heat resistance, solvent resistance, and chemical resistance inherent to fluorine-containing elastomers, is excellent in processability, and Another object of the present invention is to provide a method for efficiently producing a peroxide-vulcanizable fluoroelastomer which gives a vulcanizate having particularly excellent compression set characteristics among physical properties by suspension polymerization.

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, in an aqueous medium, an organic iodine compound which is a chain transfer agent, an oil-soluble polymerization catalyst and optionally used. It has been found that the purpose can be achieved by using oil droplets composed of a very small amount of halogen-containing solvent as a polymerization site, dissolving a fluorine-containing monomer in this, and performing suspension polymerization at a relatively high temperature and high pressure. The present invention has been completed based on this finding.

That is, the present invention uses an iodine compound represented by the general formula R.Ix (wherein R is a hydrocarbon group having 1 to 3 carbon atoms and x is 1 or 2) as a chain transfer agent, and comprises vinylidene fluoride. To produce a peroxide-curable fluoroelastomer by copolymerization with at least one fluorine-containing olefin copolymerizable therewith, the above-mentioned monomer and an aqueous medium containing a suspension stabilizer, An iodine compound, an oil-soluble polymerization catalyst, and a halogen-containing solvent in an amount of less than 10 times the total weight of the iodine compound and the oil-soluble polymerization catalyst are dispersed, and at a temperature of 50 to 70 ° C, 15 to 30 kg / cm. An object of the present invention is to provide a method for producing a peroxide-curable fluoroelastomer, which comprises carrying out suspension polymerization under a pressure of ² · G.

 Hereinafter, the present invention will be described in detail.

In the method of the present invention, in order to introduce a bonding iodine atom serving as a crosslinking point in the molecule of the fluorine-containing elastomer,
An iodine compound represented by the general formula R.Ix is used as a chain transfer agent.

In this general formula, R is a hydrocarbon group having 3 or less carbon atoms and x is required to be 2 or less. In the case of having a hydrocarbon group having 4 or more carbon atoms, the fluorine-containing elastomer has a sufficient molecular weight. When x is 3, the produced fluorine-containing elastomer has a three-dimensional structure and the workability is deteriorated. Such iodine compounds are selected from those which do not decompose under polymerization conditions or lose their effects. For example, monoiodomethane, diiodomethane, 1-iodoethane, 1,2-iodoethane, 1-iodo-n-propane Isopropyl iodide, 1,3-diiodo-n-propane and the like. Of these, diiodomethane is most preferably used in view of polymerization reactivity, vulcanization reactivity, availability, and the like.

The iodine compound can be easily produced, is extremely inexpensive, and has low toxicity, so that it can be used industrially advantageously.

When vinylidene fluoride is copolymerized with a fluorine-containing olefin copolymerizable therewith in the presence of the iodine compound represented by the general formula R.Ix, the carbon-iodine bond in the R.Ix molecule is converted into a radical. It is considered that, since it is active against iodine, normal telomerization reaction proceeds and iodine is introduced into the polymer terminal.

This iodine compound is usually 0.005 to the aqueous medium.
To 5% by weight, preferably 0.05 to 3% by weight.

As the fluorinated olefin copolymerizable with vinylidene fluoride used in the method of the present invention, for example, hexafluoropropylene, tetrafluoroethylene, perfluoroalkyl perfluorovinyl ether and the like are preferably used. As the perfluoroalkyl perfluorovinyl ether, for example, perfluoromethyl perfluorovinyl ether, perfluoroethyl perfluorovinyl ether, perfluoropropyl perfluorovinyl ether and the like are preferable.

In the most useful embodiment of the present invention, a binary fluoroelastomer comprising vinylidene fluoride (hereinafter abbreviated as VdF) unit and hexafluoropropylene (hereinafter abbreviated as HFP) unit, and a VdF unit, an HFP unit and a tetrafluoroethylene unit In a ternary fluoroelastomer comprising fluoroethylene (hereinafter abbreviated as TFE) units, the ratio of the VdF units to the HFP units is usually 40:60 to 80:20 by weight.
The preferred ratio is selected in the range of 55:45 to 75:25 by weight in the case of the binary fluorine-containing elastomer, and 45: 5 in the case of the ternary fluorine-containing elastomer.
Choose between 5 and 70:30. Further, the ternary fluorine-containing elastomer has a TFE unit content of 35% by weight or less,
Preferably, it is in the range of 5 to 25% by weight.

Further, as the perfluoroalkyl perfluorovinyl ether-based fluoroelastomer, for example, a VdF unit is 10 to 85 mol%, a TFE unit is 3 to 80 mol%, and a perfluoroalkyl perfluorovinyl ether unit is 2 to 50 mol%.
Are useful.

Those containing a monomer unit in such a ratio show good rubber-like elasticity as a fluorine-containing elastomer, and those in which the ratio of each monomer unit deviates from the above range exhibit properties as a thermoplastic resin. It is not preferable because it has.

In the method of the present invention, the above-mentioned iodine compound and a small amount of a halogen-containing solvent used in some cases are added to an aqueous medium containing a suspension stabilizer with mechanical stirring, and a mixed monomer having a predetermined composition (a charged monomer) is added thereto. )
Is dissolved under pressure, and the liquid temperature is 50-70 ° C, preferably 50-60 ° C.
The suspension polymerization is carried out by adding an oil-soluble polymerization catalyst alone or by dissolving it in a small amount of a halogen-containing solvent. If the polymerization temperature is lower than 50 ° C., the polymerization rate tends to be slow. If the polymerization temperature is higher than 70 ° C., the suspended particles of the polymer become sticky during the polymerization and are likely to be blocked.

In the present invention, polymerization is performed while adjusting the polymerization pressure to a range of 15 to 30 kg / cm ² · G. In this case, the amount of the charged monomer is adjusted so as to reach the set polymerization pressure, and after the polymerization is started,
A mixed monomer (additional monomer) having a new composition is added so that the polymerization pressure becomes constant, and the polymerization proceeds.

To this polymerization pressure is less than 15kg / cm ² · G there is a slow trend rate of polymerization, also, because the 30kg / cm even beyond the ² · G does not change the rate of polymerization is too much, a pressure greater than 30kg / cm ² · G There is no need to carry out the polymerization.

In the method of the present invention, the oil-soluble catalyst may be used alone or may be used after being dissolved in a halogen-containing solvent.
In this case, the amount of the halogen-containing solvent present in the polymerization system needs to be less than 10 times the total weight of the iodine compound used as a chain transfer agent and the oil-soluble catalyst.

In the method of the present invention, a chain transfer agent represented by the general formula R
Using an iodine compound represented by Ix (where R and x have the same meanings as described above) and performing a so-called telomerization reaction to bind iodine to the polymer terminal, so that a chain transfer other than the iodine compound is performed. In the presence of the substance, end groups other than iodine are also formed. In the present invention,
As the halogen-containing solvent, those which are not easily chain-transferred are preferably used. However, since chain transfer still does not occur at all, the amount thereof is at least 10 times the total weight of the iodine compound and the oil-soluble catalyst. As a result, the ratio of iodine bonded to the polymer terminal is reduced, and as a result, the peroxide vulcanization reactivity is reduced, and the compression set of the vulcanized product is deteriorated.

The halogen-containing solvent is preferably used in a smaller amount, and may not be used at all, from the viewpoint of suppressing reactions other than the purpose.However, from the viewpoint of providing a polymerization site and functioning as a catalyst diluent, the iodine is used. It is advantageous to use approximately the same amount as the total weight of the compound and the oil-soluble catalyst.

With respect to the ratio of the iodine compound to the oil-soluble polymerization catalyst, the telomerization reaction using the iodine compound as a telogen is the main reaction, and other side reactions are suppressed. Is desirably suppressed to a molar ratio of 0.5 or less.

In the present invention, a method for effectively promoting a telomerization reaction by suspension polymerization has been found. In particular, 1,1,2-trichloro-1,2,2-, which has been considered to be inert as a polymerization solvent for fluorine-containing olefins,
It is based on the finding that trifluoroethane is not completely inert to the polymerization of the fluoroelastomer and a partial chain transfer reaction occurs, and it can be said that it cannot be predicted by conventional thinking.

Examples of the oil-soluble polymerization catalyst include organic peroxide compounds such as diisopropyl peroxydicarbonate, dialkyl peroxydicarbonates such as di-n-propylperoxydicarbonate, t-butyl peroxyisobutyrate, and t-butyl. Peroxyesters such as peroxypivalate, diacyl peroxides such as dipropyl peroxide, di (perfluoropropionyl) peroxide, di (perfluorobutyryl) peroxide, and di (trichlorooctafluorohexanoyl) peroxide Appropriately selected from di [perfluoro (or chlorofluoro) acyl] peroxides, etc. (R ¹ and R ² in the formula are each an alkyl group having 1 to 10 carbon atoms, which may be the same or different from each other). It is suitable. Such dialkyl peroxydicarbonates include, for example, diisopropyl peroxydicarbonate, di-sec-butylperoxydicarbonate, di-sec-amylperoxydicarbonate, di-s
Examples thereof include ec-hexylperoxydicarbonate, di-n-propylperoxydicarbonate, di-n-butylperoxydicarbonate, and among them, diisopropylperoxydicarbonate is particularly preferable.

One of these oil-soluble polymerization catalysts may be used,
Two or more species may be used in combination, and the amount used is usually 0.001 to 5% by weight, preferably 0.0
It is selected in the range of 1 to 3% by weight.

Examples of the halogen-containing solvent used in the method of the present invention include a general formula CH ₃ R ³ ... (II) (wherein R ³ is a perhalomethyl group or a perhaloethyl group containing at least one fluorine atom). A) is included.

Since the compound represented by the general formula (II) contains a hydrogen atom, it has a small ozone depletion potential, is less likely to cause environmental destruction, has no problem in its use, and has a small chain transfer property to fluoroolefins. The polymerization rate and the molecular weight of the resulting polymer can be mentioned sufficiently.

Specific examples of the compound represented by the general formula (II) include ethane-based compounds such as CH ₃ CCl ₂ F, CH ₃ CClF ₂ and CH ₃ CF ₃ , and CH ₃ C
F ₂ CF ₃ , CH ₃ CF ₂ CF ₂ Cl, CH ₃ CF ₂ CFCl ₂ , CH ₃ CFCl CF ₃ , CH ₃ CF
Propane-based ones such as ClCF ₂ Cl and CH ₃ CF ₂ CFCl ₂ can be mentioned, but CH ₃ CCl ₂ FC is preferred from the viewpoint of easy handling, easy availability, and the like. The halogen-containing solvents may be used alone or in combination of two or more.

The suspension stabilizer used in the method of the present invention includes:
For example, methylcellulose, carboxymethylcellulose, bentonite, talc, diatomaceous earth and the like can be mentioned, and among these, methylcellulose is preferable.

One of these suspension stabilizers may be used alone, or two or more thereof may be used in combination. The amount of the suspension stabilizer is usually 0.001 to 3% by weight, preferably 0.01 to 1% by weight based on the aqueous medium. Is selected in the range.

The polymerization time in the present invention is not particularly limited, but is usually about 3 to 50 hours. The amount of the generated fluoropolymer is substantially equal to the amount of the additional monomer, and the charge composition is determined so that the composition of the fluoropolymer and the composition of the additional monomer are substantially the same.

The composition of the charged monomer and the added monomer was determined by gas chromatography (GC), and the composition of the monomer units in the fluoropolymer was determined by dissolving the polymer in acetone at ¹⁹ F NM.
It can be measured by R.

The fluorine-containing elastomer of the present invention can be vulcanized with a polyamine compound, a polyol compound or the like, but when peroxide vulcanization using an organic peroxide, the improved performance of the fluorine-containing elastomer of the present invention is remarkably exhibited. .

Next, the peroxide vulcanization method will be described. First, a polyfunctional unsaturated compound, an organic peroxide and a metal oxide or metal water acting as a filler or an acid acceptor used as necessary are added to the fluorine-containing elastomer. After compounding and kneading the oxides and the like, vulcanization is performed by heating. As the polyfunctional unsaturated compound, for example, triallyl cyanurate, triallyl isocyanurate, tris (diallylamine) -s-triazine and the like are useful, and triallyl isocyanurate is particularly preferably used. The amount of these polyfunctional unsaturated compounds used is 100
The amount is usually 0.1 to 10 parts by weight, preferably 1 to 6 parts by weight per part by weight.

As the organic oxide, those which easily generate peroxy radicals by heat are preferable. For example, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-
3,2,5-dimethyl-2,5-di (t-butylperoxy)
Dialkyl peroxides such as hexane are preferred.

As metal oxides and hydroxides as acid acceptors, for example, oxides and hydroxides such as calcium, magnesium, lead, and zinc are effective. These acid acceptors may not be particularly used depending on the purpose. As the filler, for example, carbon black, silica, clay, talc and the like are appropriately used as needed.

The mixture of the fluorine-containing elastomer, the polyfunctional unsaturated compound, the organic peroxide, and the filler and the acid acceptor used as necessary is kneaded with a roll or a Banbury mixer, and then added to a mold. Pressed for primary vulcanization and then secondary vulcanization. In general, the primary vulcanization conditions are 100-200
° C, vulcanization time 5 minutes to 30 minutes, pressure 20 to 300 kg / cm ² · G The range of secondary vulcanization is usually 100 to 200
° C, the vulcanization time is selected from the range of 0 to 20 hours.

Effect of the Invention According to the method of the present invention, a peroxide-curable fluorine-containing elastomer having a bonded iodine atom serving as a crosslinking point in a molecule can be efficiently produced. Further, the fluorine-containing elastomer obtained by the method of the present invention is excellent in processability at the time of roll kneading, and is excellent in heat resistance, solvent resistance, chemical resistance and excellent compression set by being peroxide-vulcanized. It can provide a vulcanizate that can be used together, and is suitably used, for example, for sealing materials such as gaskets, O-rings, and oil seals used under severe conditions, diaphragms, hoses, and protective coatings.

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

The physical properties and molecular weight of the fluoroelastomer, the physical properties of the vulcanized rubber, and the vulcanization properties were determined according to the following methods.

(1) Physical Properties and Molecular Weight of Fluorine-Containing Elastomer (a) Intrinsic Viscosity Number [η] A solution of a fluorine-containing elastomer in methyl ethyl ketone having a concentration of 0.1 g / 100 ml was prepared and measured at 35 ° C. using a capillary viscometer.

(B) The molecular weights _N and _W and the molecular weight distribution _W / _N are
It was measured and determined under the following conditions.

Molecular weight distribution measurement conditions Liquid chromatograph: LC-3A type [Shimadzu Corporation]
Column: KF-80M (2) + KF-800P (pre-column)
[Showa Denko KK] Detector: ERC-7510S [Elma Optical Co., Ltd.] Integrator: 7000A (manufactured by System Instruments) Developing solvent: tetrahydrofuran Concentration: 0.1% by weight Temperature: 35 ° C For molecular weight calibration curve Standard polymer: monodisperse polystyrene [Toyo Soda Co., Ltd.] [ _W / _N- 1.2 (max)] (c) Mooney viscosity Measured under the following conditions according to JIS K-6300.

Mooney Viscosity Measurement Conditions Specimen: 7 to 8 mm thick, about 4 cm x 4 cm square plate with a hole of about 10 mm in the center, including two pieces (one set weighing 35 to 40 g) ), Test specimen.

Measuring device: Ueshima Seisakusho VR-103ST, using L-shaped rotor Measuring method: The test piece was attached to the device with cellophane sandwiched between the test piece and the metal surface in contact with it, temperature 121 ° C, preheating time 1 minute, The measurement is performed under the condition that the rotor operates for 10 minutes.

(D) Iodine content Elastomer is dissolved in acetone and the concentration is about 20% by weight.
Was prepared and determined by a fluorescent X-ray method.

(2) Physical properties of vulcanized rubber (a) Tensile properties Under the following peroxide vulcanization standard conditions, a vulcanized sheet with a thickness of 2 mm was prepared, and a No. 3 dumbbell-type test piece was punched out from the vulcanized sheet according to JIS K-6301. Using a tensile tester (manufactured by Toyo Seiki Co., Ltd.), measurement was performed at a tensile speed of 50 cm / min.

Standard conditions for peroxide vulcanization Fluorine-containing elastomer: 100 parts by weight Medium thermal carbon: 30 parts by weight Triallyl isocyanurate: 4 parts by weight Perhexa 2.5B-40: 3.75 parts by weight [Nippon Oil & Fats Co., Ltd.
Kneading method: Roll Primary hot press vulcanization: 160 ° C × 10 minutes Secondary oven vulcanization: 180 ° C × 4 hours (b) Compression set P-24 type O which was peroxide-vulcanized under the above standard vulcanization conditions
-Using a ring, hold at a temperature of 200 ° C for 72 hours under 25% pressure compression according to JIS K-6301, then allow it to cool to room temperature for 30 minutes, then measure using a thickness gauge (manufactured by Kyoto Kobunki Keiki) did.

(3) Vulcanization characteristics According to ASTM D2094-87, the vulcanization characteristics, ie, minimum viscosity, degree of vulcanization, induction period and appropriate vulcanization time are determined by an oscillating disk rheometer (ODR) as follows. Was.

Vulcanization Characteristics Measurement Conditions Specimen: The compounded rubber material kneaded under the standard conditions of peroxide vulcanization is dispensed at a thickness of 6 ± 1 mm. A set of two pieces (one set having a weight of 25 to 30 g) including a single plate having a side of 30 to 35 mm and a hole having a diameter of about 8 mm at the center is prepared.

Test device: Toyo Seiki Oscillating Disk Rheometer, amplitude 3 degrees, amplitude 6cpm Disk: BL type Measurement method: Place the test piece with a cellophane between the test piece and the metal surface in contact with it At a measuring temperature of 160 ° C,
Measured without preheating.

Reference Example 1 An autoclave equipped with an electromagnetic induction stirrer and having an internal volume of about 15 was thoroughly scavenged with nitrogen gas, and repeatedly depressurized and charged with nitrogen three times to replace with nitrogen. Then, 5,440 g of pure water deoxygenated under reduced pressure. And 5.4 g of methylcellulose (viscosity 50 cp) as a suspension stabilizer and 27.7 g of jodmethane were charged.
The temperature was kept at 50 ° C. while stirring at 00 rpm. Then VdF
A mixed monomer composed of 366 g, 1,740 g of HFP, and 146 g of TFE was charged as a charged monomer. At 50 ° C., the internal pressure of the autoclave reached 24 kg / cm ² · G.

Next, as a catalyst, a solution prepared by dissolving 4.3 g of diisopropyl peroxydicarbonate in 86 g of 1,1,2-trichloro-1,2,2-trifluoroethane (hereinafter referred to as Freon 113) was charged, and polymerization was started. Was. 23.5kg pressure by polymerization
/ cm ² · G, a mixed monomer consisting of 47.6% by weight of VdF, 31.6% by weight of HFP and 20.8% by weight of TFE was added as an additional monomer, and the pressure was again reduced to 24 kg / cm ² · G. I put it back.
Such an operation was repeated to carry out a polymerization reaction for 12.5 hours. After completion of the polymerization reaction, the suspension obtained by scavenging the remaining mixed monomer was dehydrated with a centrifuge, washed sufficiently with water, and vacuum-dried at 100 ° C. to obtain about 5,200 g of an elastomer. When the obtained fluorine-containing elastomer was analyzed by ¹⁹ FNMR, 47.5% by weight of VdF unit and 31.4% of HFP unit were obtained.
%, TFE unit 21.1% by weight, and the fluorine content was 68.
1% by weight.

[Η] is 50 ml / g, _N is 3.3 × 10 ⁴ , _W / _N is
2.3, iodine content is 0.51%, Mooney viscosity ML _{1 + 10} 121 ℃ =
It was 5.

When peroxide vulcanization was carried out under the above-mentioned standard conditions of the fluoroelastomer, a vulcanizate having excellent processability and excellent physical properties was obtained. Second vulcanization and vulcanized rubber properties
It is shown in the table.

Examples 2 and 3, Reference Examples 2 and 3, and Comparative Examples 1 to 4 The same procedure as in Reference Example 1 was carried out except that the polymerization was carried out under the polymerization conditions shown in Table 1. Table 2 shows the polymer properties, vulcanization properties, and vulcanized rubber properties of the obtained elastomer.

Continuation of front page (72) Inventor Kenzo Hashimura 6-4100 Asahicho, Nobeoka-shi, Miyazaki Asahi Kasei Kogyo Co., Ltd. (56) References JP-A-1-319512 (JP, A)

Claims (1)

(57) [Claims] 1. In an aqueous medium containing (A) a suspension stabilizer, i) vinylidene fluoride, ii) at least one other copolymerizable fluorine-containing olefin, iii) an oil-soluble polymerization catalyst, iv. Wherein R is a hydrocarbon group having 1 to 3 carbon atoms, and x is 1
Or 2) a chain transfer agent which is an iodine compound represented by the formula: and v) a compound represented by the formula CH ₃ R ^{3 wherein} R ³ is a perhalomethyl or perhaloethyl group containing at least one fluorine atom. A solvent, wherein the solvent is present in an amount of less than 10 times the total weight of the iodine compound and the polymerization catalyst, and (B) at a temperature of 50-70 ° C, 15-30 kg / cm ² -A method for producing a peroxide-curable fluorine-containing elastomer, wherein suspension polymerization is performed under a pressure of G.