JP2007092076A - Fluorine-containing elastomer and composition thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluorine-containing elastomer capable of giving a vulcanization product which has excellent low temperature properties and solvent resistance without deteriorating the original moldability/processability and compression permanent set-resistant characteristics of the fluorine-containing elastomer, and to provide a fluorine-containing elastomer composition which has excellent cold resistance, fuel oil resistance, and the like. <P>SOLUTION: The fluorine-containing elastomer whose copolymerization composition comprises (a) 50-85 mol% vinylidene fluoride, (b) 0-25 mol% tetrafluoroethylene, (c) 7-20 mol% perfluoro(methylvinyl ether), (d) 3-15 mol% CF<SB>2</SB>=CFO[CF<SB>2</SB>CF(CF<SB>3</SB>)O]<SB>n</SB>CF<SB>3</SB>(n: 4-6), and (e) 0.1-2 mol% RfX (Rf is a 2-8C unsaturated fluorohydrocarbon group in which one or more ether bonds may be contained; and X is Br or I) is provided. The fluorine-containing elastomer composition, added with 0.1-10 pts.wt. organic peroxide, 0.1-10 pts.wt. multi-functional unsaturated compound and ≥2 pts.wt. acid receptor based on 100 pts.wt. fluorine-containing elastomer, gives a cured product having excellent cold resistance and fuel oil resistance. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fluorine-containing elastomer and a composition thereof. More specifically, the present invention relates to a fluorine-containing elastomer and a composition thereof that can give a vulcanizate excellent in moldability, low-temperature characteristics and solvent resistance.

  Fluorine-containing elastomers with vinylidene fluoride-tetrafluoroethylene-perfluoro (methyl vinyl ether) as the main structural unit not only have excellent heat resistance and solvent resistance unique to fluorine-containing elastomers, but also have good low-temperature characteristics. Therefore, it is used in various industrial fields including the automobile industry. However, in response to technical progress in recent years, such fluorine-containing elastomers are often difficult to cope with, and in particular, low temperature characteristics and resistance to alcoholic solvents such as methanol have been strictly demanded. ing. Further, along with recent exhaust gas regulations and the like, further heat resistance, solvent resistance, and low temperature characteristics for fluorine-containing elastomers are required.

In order to solve such problems, it has been proposed to copolymerize a monomer having a plurality of ether bonds in the side chain instead of perfluoro (methyl vinyl ether) in the fluorine-containing elastomer. In this case, in order to make the resulting copolymer elastomeric, a large amount of this monomer must be copolymerized, and if the copolymerization ratio is small, it becomes semi-resinous and the low-temperature properties are impaired. It becomes like this. Actually, the copolymerization ratio is 12 to 50 mol%, and in each example, the copolymer composition is 25 to 32 mol%. However, the fluorine-containing elastomer containing a large amount of such monomers has a problem that the mechanical strength is inferior and the molding processability is not good, for example, foaming easily occurs during molding.
Japanese Patent Publication No.5-139661

  In addition, since automotive fuel seal materials are required to have perfect fuel oil resistance, they are currently used mainly on commercially available fluororubber, but in addition to gasoline, which is commonly used as automotive fuel, combustion efficiency In view of the above, oxygen-containing fuels such as ethers and alcohols are also being used. Oxygenated fuel can be handled by increasing the fluorine content in the fluororubber, but increasing the fluorine content will deteriorate cold resistance and may cause fuel leakage in cold winter regions. . On the contrary, if the fluorine content is decreased, the cold resistance is improved, but the resistance to oxygen-containing fuel is lost, and it is very difficult to satisfy both of them simultaneously.

  An object of the present invention is to provide a fluorine-containing elastomer which can give a vulcanizate excellent in low-temperature characteristics and solvent resistance without impairing the molding processability and compression set resistance inherent to the fluorine-containing elastomer, and cold resistance, The object is to provide a composition excellent in fuel oiliness and the like.

The object of the present invention is that the copolymer composition is
(a) Vinylidene fluoride 50-85 mol%
(b) Tetrafluoroethylene 0-25 mol%
(c) Perfluoro (methyl vinyl ether) 7-20 mol%
(d) CF ₂ = CFO [CF ₂ CF (CF ₃ ) O] nCF ₃ 3-15 mol%
(Where n is an integer from 4 to 6)
(e) RfX (Rf is an unsaturated fluorohydrocarbon group having 2 to 8 carbon atoms, 0.1 to 2 mol%
The group may have one or more ether bonds,
X is bromine or iodine)
This is achieved by the fluorine-containing elastomer. This fluorine-containing elastomer preferably has the general formula R (Br) n (I) m (wherein R is a saturated fluorohydrocarbon group or saturated chlorofluorohydrocarbon group having 2 to 6 carbon atoms, and n and m are Obtained by copolymerization in the presence of a bromine-containing and / or iodine compound represented by 0, 1 or 2 and m + n is 2.

  Further, a fluorine-containing elastomer composition comprising 0.1 to 10 parts by weight of an organic peroxide, 0.1 to 10 parts by weight of a polyfunctional unsaturated compound, and 2 parts by weight or more of an acid acceptor per 100 parts by weight of the fluorine-containing elastomer. Since the product provides a cross-linked product excellent in cold resistance and fuel oil resistance, the cross-linked product is preferably used as a sealing material for automobile fuel.

  The fluorine-containing elastomer according to the present invention is a vulcanization having excellent low temperature characteristics (glass transition temperature) and solvent resistance (methal resistance) in addition to its inherent heat resistance, moldability and compression set resistance. Since the product can be formed, it can be effectively used as a molding material for O-rings, oil seals, fuel hoses and the like.

In particular, this fluorine-containing elastomer is obtained by adding a bituminous fine powder or a flat filler and peroxide-crosslinking, and has a TR ₁₀ value (conforming to JIS K6261) of -30 ° C or lower and a methanol swelling ratio (JIS K6258). (Compliance; 25 ° C, 168 hours) is within + 50%, and not only has excellent cold resistance and compression set resistance, but also fuel shielding against gasoline and automobile fuels using oxygenated fuel Since it is excellent, it can be used effectively as a sealing material for automobile fuel. Fuel oil resistance is demonstrated not only for fuel oil and alcohol, but also for oils such as lubricating oil and hydraulic oil, and aromatic or aliphatic hydrocarbons. Is also used.

  The copolymer composition ratio of the fluorine-containing elastomer is as follows: (a) vinylidene fluoride is 50 to 85 mol%, preferably 60 to 85 mol%, (b) tetrafluoroethylene is 0 to 25 mol%, preferably 0 to 20 Mol%, (c) 7-20 mol% perfluoro (methyl vinyl ether), preferably 7-15 mol%, (d) 3-15 mol% perfluorovinyl ether represented by the above general formula, preferably 3-5 mol% 10 mol%, (e) 0.1 to 2 mol%, preferably 0.3 to 1.5 mol% of a bromine-containing or iodine-unsaturated compound represented by the above general formula, these composition ratios are desired low-temperature characteristics and solvent resistance It is selected as a range that can give a vulcanizate having.

The following components (b) to (e) are copolymerized with the component (a) tetrafluoroethylene.
When the tetrafluoroethylene (b) component is further copolymerized, the solvent resistance can be remarkably improved. However, if the composition ratio of the component (b) is too large, the low temperature characteristics are impaired. Therefore, the ratio is 25 mol% or less, preferably 20 mol% or less. In addition, the copolymerization of component (b) significantly improves the resistance to oxygen-containing compound mixed fuels such as methanol / gasoline mixed fuel and ethanol / gasoline mixed fuel, and alcohol fuels such as methanol and ethanol.
Component (c), perfluoro (methyl vinyl ether), is an essential component for imparting flexibility to the resulting copolymer and improving low temperature characteristics, particularly TR ₇₀ value in the TR test.
As the component (d), perfluorovinyl ether, a single component of the compound represented by the general formula may be used, or a mixture of two or more having various n values may be used. As a perfluorovinyl ether similar to this, the general formula CF ₂ = CFO [CF ₂ CF (CF ₃ ) O] mCF ₂ CF ₂ CF ₃ is known (Japanese Patent Publication No. 5-13961). According to the results of their studies, copolymerization of this monomer imparts low temperature properties, but a decrease in molecular weight, a decrease in molding processability such as foaming during molding, a decrease in mechanical strength, and the like are observed. However, this compound can be copolymerized within a range that does not impair the desired properties, for example, at a ratio of 1 mol% or less.
The perfluorovinyl ether of the component (d) represented by the general formula is obtained by reacting CF ₃ OCF (CF ₃ ) COF with hexafluoropropene oxide in the presence of a cesium fluoride catalyst, a diglyme solvent, etc., and then anhydrous potassium carbonate And the product is a mixture of n = 2-6, but by separating it, perfluorovinyl ether having an n value of 4-6 is separated, These can be used alone or as a mixture thereof or as a mixture of these with n = 2-3. The perfluorovinyl ether of n = 4 to 6 represented by the above general formula shows better low-temperature characteristics at the same copolymerization ratio as compared with that of n = 2 to 3, and a lower copolymerization ratio Can provide equivalent low-temperature characteristics (for example, Examples 1 to 3 to Comparative Example 3 and Example 4 to Comparative Example 5 described later).
The bromine- or iodine compound of the component (e), for example, _{CF 2 = CFOCF 2 CF 2 Br} , CF 2 = CFOCF 2 CF (CF 3) OCF 2 CF 2 Br, CF 2 = CFBr, CF 2 = CHBr, CF R 2 groups such as ₂ = CFI and CF ₂ = CHI are unsaturated fluorohydrocarbon groups having 2 to 8 carbon atoms, which may have one or more ether bonds (Japanese Patent Publication No. 54-1585). In other words, CF ₂ = CFOCF ₂ CF ₂ Br, CF ₂ = CFI, and CF ₂ = CHI are preferably used.

  Further, for the purpose of adjusting the molecular weight of the fluorine-containing elastomer copolymer according to the present invention or for the purpose of suppressing molding processability, particularly foaming in the curing stage, it is represented by the general formula R (Br) n (I) m. It is very effective to carry out the copolymerization reaction in the presence of a bromine-containing and / or iodine compound (see Japanese Patent Publication No. 54-1585).

Such compounds, for example, _{ICF 2 CF 2 CF 2 CF 2} I, ICF 2 CF 2 CF 2 CF 2 Br, ICF 2 CF 2 Br and the like are used, in particular _{ICF 2 CF 2 CF 2 CF 2} I curing characteristics From the viewpoint of the above, it is preferable. Other examples are described in Japanese Patent Publication Nos. 63-308008 and 58-4728.

  These compounds act as chain transfer agents and serve to adjust the molecular weight of the copolymer produced. As a result of the chain transfer reaction, a copolymer having bromine and / or iodine atoms bonded to the molecular ends is obtained, and these sites serve as curing sites in the vulcanization molding stage. However, since the mechanical strength of the final molded product is lowered when the proportion used in the polymerization step is large, the proportion used is about 1% by weight or less, preferably about 0.5 to less than the total monomer weight. 0.01% by weight.

Further, in order to improve the compression set resistance of the vulcanized molded product, perfluorodivinyl ether as described below may be copolymerized. The proportion of use is about 1% by weight or less, preferably about 0.5 to 0.1% by weight, based on the total monomer weight, from the viewpoint of the mechanical properties of the molded product.
CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ OCF = CF ₂

  In addition, other monomers such as fluorinated monomers such as trifluoroethylene, hexafluoropropene, and chlorotrifluoroethylene may be used within a range that does not impair the desired properties required for the fluorinated elastomer of the present invention. Further, it may be copolymerized.

  The fluorine-containing elastomer of the present invention can be produced by an aqueous emulsion polymerization method or an aqueous suspension polymerization method. In the aqueous emulsion polymerization method, either a water-soluble peroxide alone or a redox system in combination with a water-soluble reducing substance can be used as a reaction initiator system. Examples of water-soluble peroxides include ammonium persulfate, potassium persulfate, and sodium persulfate. Examples of water-soluble reducing substances include sodium sulfite and sodium hydrogen sulfite. At this time, a pH regulator (relaxation agent) such as sodium monohydrogen phosphate, sodium dihydrogen phosphate, potassium monohydrogen phosphate, potassium dihydrogen phosphate and the like is also used as a stabilizer for the aqueous emulsion.

As the emulsifier used in the emulsion polymerization method, a fluorinated carboxylate is generally used (see Japanese Patent Publication No. 5-13961), preferably
CF ₃ CF ₂ CF ₂ O [CF (CF ₃ ) CF ₂ O] nCF (CF ₃ ) COONH ₄
n: 1 or 2
Is used. These emulsifiers are used as an aqueous solution of about 1 to 30% by weight, preferably about 5 to 20% by weight. If the amount of the emulsifier is less than this, the monomer and the produced copolymer cannot be uniformly dispersed in the aqueous medium, and if it is too much, it is economically disadvantageous.

  The copolymerization reaction is performed at a temperature of about 20-80 ° C, preferably about 25-60 ° C. If the polymerization temperature is too high, problems such as foaming occur during the molding process, and the compression set properties of the vulcanized molded article also deteriorate. The polymerization pressure is generally performed at about 5 MPa or less.

  The fluorine-containing elastomer thus obtained has a glass transition temperature Tg of −30 to −45 ° C. The molecular weight of the obtained copolymer is not particularly limited, but the number average molecular weight Mn (GPC method, tetrahydrofuran solvent) is preferably about 10,000 to 100,000, preferably about 50,000 to 300,000. The solution viscosity ηsp / c (35 ° C., 1 wt% methyl ethyl ketone solution) as an index of molecular weight is about 0.1-2 dl / g, preferably about 0.2-1 dl / g. Depending on the composition or molecular weight of the resulting copolymer, it may be insoluble or insoluble in methyl ethyl ketone, and a 1 wt% methyl ethyl ketone solution may not be prepared. In this case, hexafluorobenzene was used as a solvent, and the solution viscosity ηsp / c was measured as a 1 wt% hexafluorobenzene solution (35 ° C.). The value of the solution viscosity ηsp / c is about 0.1 to 7 dl / g, preferably 0.3 to 5 dl / g.

  The fluorine-containing elastomer having such properties can be cured by various conventionally known vulcanization methods such as peroxide vulcanization method, polyamine vulcanization method, polyol vulcanization method or irradiation methods such as radiation and electron beam. However, the peroxide vulcanization method using organic peroxides has excellent mechanical strength, and forms a carbon-carbon bond with a stable structure at the cross-linking point, resulting in chemical resistance, wear resistance, solvent resistance, etc. It is particularly preferably used because it gives an excellent vulcanizate.

  Examples of the organic peroxide used in the peroxide vulcanization method include 2,5-dimethyl-2,5-bis (tertiary butylperoxy) hexane, 2,5-dimethyl-2,5-bis (tertiary Butylperoxy) hexyne-3, benzoyl peroxide, bis (2,4-dichlorobenzoyl) peroxide, dicumyl peroxide, di-tert-butyl peroxide, tert-butyl cumyl peroxide, tert-butyl peroxybenzene, 1,1-bis (tert-butylperoxy) -3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroxyperoxide, α, α'-bis (tert-butylperoxy) -p-diisopropylbenzene, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, tert-butylperoxyisopropyl carbonate and the like.

  In the peroxide vulcanization method in which these organic peroxides are used, polyfunctional unsaturated compounds such as tri (meth) allyl isocyanurate, tri (meth) allyl cyanurate, triallyl trimellitate, N, N′-m-phenylenebismaleimide, diallyl phthalate, tris (diallylamine) -s-triazine, triallyl phosphite, 1,2-polybutadiene, ethylene glycol diacrylate, diethylene glycol diacrylate, and the like are preferably used in combination. By using these co-crosslinking agents in combination, a vulcanizate having superior vulcanization characteristics, mechanical strength, compression set characteristics and the like can be obtained.

  Furthermore, hydrotalcite compounds and divalent metal oxides or hydroxides, for example, oxides or hydroxides of calcium, magnesium, lead, zinc and the like can also be used as the acid acceptor.

  Each of the above components to be blended in the peroxide vulcanizing system is about 0.1 to 10 parts by weight, preferably about 0.5 to 5 parts by weight of organic peroxide per 100 parts by weight of the fluorine-containing elastomer. Accordingly, the co-crosslinking agent is used in an amount of about 0.1 to 10 parts by weight, preferably about 0.5 to 5 parts by weight, and the acid acceptor is used in an amount of about 2 parts by weight or more, preferably about 3 to 20 parts by weight. . If the proportion of the acid acceptor used is less than this, the corrosion resistance to the metal is impaired.

  In vulcanization, in addition to the above-described components, conventionally known fillers, reinforcing agents, plasticizers, lubricants, processing aids, pigments, and the like can be appropriately blended. When carbon black is used as a filler or reinforcing agent, it is generally used at a ratio of about 10 to 50 parts by weight per 100 parts by weight of the fluorine-containing elastomer.

  Furthermore, the addition of bituminous fine powder improves the compression set resistance and can extend the life of sealing materials by improving the heat resistance, and the addition of a flat filler improves the fuel oil barrier properties. Thus, it is possible to further suppress the transpiration of automobile fuel or the like to be sealed.

  As a bituminous fine powder, a bituminous substance such as coal is pulverized, and the average particle size is about 10 μm or less, generally about 1 to 10 μm, preferably about 3 to 8 μm. Is used. If an average particle size larger than this is used, the breaking strength and breaking elongation of the rubber are lowered, and the practicality in terms of strength is impaired. Actually, commercially available products such as Mineral Black 325BA manufactured by Keystone Filler & Mfg are used as they are. These bituminous fine powders are used in an amount of about 40 parts by weight or less, preferably about 5 to 30 parts by weight, per 100 parts by weight of the fluorine-containing elastomer. If it is used in a proportion higher than this, the viscosity of the composition becomes too high, which causes troubles during kneading and molding.

  Further, as the flat filler, for example, at least one of clay, mica, graphite, molybdenum disulfide, etc., the average particle diameter is about 0.5-50 μm, preferably about 5-30 μm, and the aspect ratio is 3 or more. Preferably, 5 to 30 are used. When the average particle diameter or aspect ratio is less than this, the fuel shielding property is not improved. On the other hand, when a particle having an average particle size larger than this is used, the breaking strength and breaking elongation of the rubber are lowered, and the practicality in terms of strength is impaired. These flat fillers are used in an amount of about 40 parts by weight or less, preferably about 5 to 30 parts by weight, per 100 parts by weight of the fluorine-containing elastomer. If it is used in a proportion higher than this, the viscosity of the composition will increase and it will no longer be kneaded, and the sealing material after crosslinking will become very hard and the sealing performance will be impaired.

  Each of the above components is kneaded by a commonly used mixing method such as roll mixing, kneader mixing, Banbury mixing, solution mixing, etc., and the kneaded kneaded material is generally pressed at about 100 to 250 ° C. for about 1 to 60 minutes. Vulcanization by vulcanization, preferably oven vulcanization (secondary vulcanization) within about 30 hours at about 150 to 250 ° C. is also performed.

The obtained fluorine-containing elastomer gives a vulcanizate that develops the following low-temperature characteristics after organic peroxide crosslinking.
-43 ℃ ≦ TR ₁₀ <-30 ℃ <TR ₇₀ ≦ -20 ℃
Here, the TR ₁₀ and TR ₇₀ values are 50% elongation of the sample in the TR test, and after vitrification with the glass transition temperature Tg or less, the strain gradually relaxes as the temperature is gradually raised, and the initial elongation is reduced. Shows 10% or 70% recovered temperature.

Further, in order to satisfy the conditions for TR ₁₀ and TR ₇₀ , the total composition amount of perfluoro (methyl vinyl ether) of component (c) and perfluorovinyl ether of component (d) is 10 mol% or more, Preferably it is 15 mol% or more. When the total amount of these component compositions is 10 mol% or less, the resulting copolymer becomes a semi-resin or the low temperature characteristics, particularly TR ₇₀ value, deteriorates.

  Next, the present invention will be described with reference to examples.

Stainless steel autoclave of volume 10L with Reference Example stirrer, cesium fluoride 36 g, was charged with diglyme 360g and _{CF 3 OCF (CF 3) COF} 4.18kg, was cooled to -10 ° C. After stirring overnight, there 12.0 kg of hexafluoropropene oxide was charged at a feed rate of 150 g / hour. After the completion of the supply, stirring was continued for 2 hours while maintaining this temperature, and then the temperature was returned to room temperature. Thereafter, only the fluorocarbon phase was carefully extracted from the lower outlet of the autoclave. As a result of analyzing 15.9 kg of the obtained fluorocarbon phase by gas chromatography (GC), it had the following composition.
CF ₃ O [CF (CF ₃ ) CF ₂ O] nCF (CF ₃ ) COF
n GC (%)
twenty one
3 27
4 50
5 20
6 2

1.2 kg of the obtained fluorocarbon phase and 1.2 kg of anhydrous calcium carbonate were charged into a 10 L glass reaction vessel equipped with a stirrer and heated to 130 ° C. After the generation of carbon dioxide gas was completed, the inside was depressurized to 1 Torr, and an unreacted fluorocarbon mixture and a very small amount of diglyme (total 30 g) were recovered. As a result of analyzing 1.0 kg of the obtained product by GC, it had the following composition. Since the vinylation reaction proceeds almost quantitatively (90% or more), the composition hardly changes before and after the reaction.
CF ₂ = CFO [CF ₂ CF (CF ₃ ) 0] nCF ₃
n GC (%)
twenty one
3 27
4 50
5 20
6 2

δ/ppm
F^a -114.2
F^b -121.6
F^c -135.2
F^d -83.5
F^e -143.3
F^f -78.9
F^g -144.4
F^h -52.8

(n=3)MPr₃VE

δ/ppm
F^a -114.2
F^b -121.6
F^c -135.3
F^d -83.5
F^e -143.2
F^f -78.9
F^g -144.5
F^h -52.9

(n=4)MPr₄VE

δ/ppm
F^a -114.2
F^b -121.6
F^c -135.3
F^d -83.4
F^e -143.1
F^f -78.8
F^g -144.5
F^h -52.9

(n=5)MPr₅VE

δ/ppm
F^a -114.1
F^b -121.7
F^c -135.3
F^d -83.5
F^e -143.1
F^f -78.9
F^g -144.5
F^h -52.9

(n=6)MPr₆VE

δ/ppm
F^a -114.1
F^b -121.6
F^c -135.3
F^d -83.5
F^e -143.1
F^f -78.8
F^g -144.5
F^h -52.9 The resulting vinyl ether compound was distilled to isolate compounds having respective n values. Each compound was identified by ¹⁹ F-NMR analysis (chemical shift is based on CFCl ₃ ).
(n = 2) MPr ₂ VE

δ / ppm
F ^a -114.2
F ^b -121.6
F ^c -135.2
F ^d -83.5
F ^e -143.3
F ^f -78.9
F ^g -144.4
F ^h -52.8

(n = 3) MPr ₃ VE

δ / ppm
F ^a -114.2
F ^b -121.6
F ^c -135.3
F ^d -83.5
F ^e -143.2
F ^f -78.9
F ^g -144.5
F ^h -52.9

(n = 4) MPr ₄ VE

δ / ppm
F ^a -114.2
F ^b -121.6
F ^c -135.3
F ^d -83.4
F ^e -143.1
F ^f -78.8
F ^g -144.5
F ^h -52.9

(n = 5) MPr ₅ VE

δ / ppm
F ^a -114.1
F ^b -121.7
F ^c -135.3
F ^d -83.5
F ^e -143.1
F ^f -78.9
F ^g -144.5
F ^h -52.9

(n = 6) MPr ₆ VE

δ / ppm
F ^a -114.1
F ^b -121.6
F ^c -135.3
F ^d -83.5
F ^e -143.1
F ^f -78.8
F ^g -144.5
F ^h -52.9

Comparative Example 1
The inside of a 500 ml stainless steel autoclave was replaced with nitrogen gas, and after deaeration, the following reaction medium was charged.
Surfactant CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) CF ₂ OCF (CF ₃ ) COONH ₄ 30g
Na ₂ HPO ₄・ 12H ₂ 0 0.5g
Ion exchange water 250ml

The inside of the autoclave was again replaced with nitrogen gas, and after deaeration, the following reaction raw materials were charged.
Vinylidene fluoride [VdF] 40g (68.1%)
Tetrafluoroethylene [TFE] 6g (6.5%)
Perfluoro (methyl vinyl ether) [FMVE] 24g (15.8%)
CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF (CF ₃ ) OCF ₃ [MPr ₂ VE] 40 g (8.8%)
CF ₂ = CFOCF ₂ CF ₂ Br [FBrVE] 2g (0.8%)
ICF ₂ CF ₂ CF ₂ CF ₂ I [DIOFB] 0.5g
The percentage in parentheses is mol%.

Next, the temperature inside the autoclave was set to 50 ° C., and 0.01 g of sodium hydrogen sulfite and 0.05 g of ammonium persulfate were added as 0.3 wt% aqueous solutions to start the polymerization reaction. After reacting for 2 hours, cooling, discharging the residual gas and taking out the emulsion, adding 5 wt% aqueous calcium chloride solution to coagulate the polymer, washing with water and drying, the following composition ( ¹⁹ F 108 g of an elastomeric copolymer (by -NMR method) was obtained.
VdF 71 mol%
TFE 7 mol%
FMVE 14 mol%
MPr ₂ VE 7.2 mol%
FBrVE 0.8 mol%

To 100 parts of this elastomeric copolymer (weight, the same shall apply hereinafter)
MT carbon black (Cancab product Thermax N990) 30 parts Triallyl isocyanurate (Nippon Kasei products TAIC M60) 6 parts Organic peroxide (Nippon Yushi Co., Ltd. Perhexa 25B-40) 1.4 parts
Add 4 parts of ZnO, mix with a two-roll mill, and compress the resulting curable composition at 180 ° C for 10 minutes to obtain a sheet and O-ring (P24) with a thickness of 2 mm, and further at 200 ° C for 10 hours Secondary vulcanization (oven vulcanization) was performed.

The following tests were performed on the vulcanized product and the vulcanized product.
Curing test: t ₁₀ , t ₉₀ at 180 ° C using a Monsanto disk rheometer
Measure ML and MH values
Normal state property: Conforms to JIS K6250,6253 Compression set: Conforms to ASTM D395 Method B, P24 O-ring, 200 ° C, 70 hours
Measure value Low-temperature characteristics: Measure TR ₁₀ and TR ₇₀ values according to ASTM D1329 Methanol swelling test: Measure volume change rate after immersion in methanol at 25 ° C for 70 hours

Comparative Examples 2-6
In Comparative Example 1, the reaction medium, reaction raw materials, and reaction conditions were changed as shown in Table 1 below. In Table 1, the production amount of the produced elastomer copolymer, the copolymer composition, the solution viscosity ηsp / c, and the glass transition temperature Tg (using SEIKO I SSC5200) are also shown.
Table 1
Comparative example
2 3 4 5 6
[Reaction medium]
Surfactant (g) 40 40 40 40 40
Na ₂ HPO ₄・ 12H ₂ O (g) 0.5 0.5 0.5 0.5 0.5
Ion exchange water (ml) 250 250 250 250 250
[Reaction raw materials]
VdF (g) 40 40 40 46 46
TFE (g) 6 6 6--
FMVE (g) 20 24 16 24 24
MPr ₂ VE (g) 26--40-
MPr ₃ VE (g) 14 40 48-40
FBrVE (g) 2 2 2 2 2
DIOFB (g) 0.5 0.5 0.5 0.5 0.5
[Reaction conditions]
Temperature (° C) 50 50 50 50 50
Time (hrs) 14 17 20 15 20
[Amount of copolymer]
Production amount (g) 110 107 106 103 105
[Copolymer composition]
VdF (mol%) 72 72 75 84 83
TFE (mol%) 7 7 7--
FMVE (mol%) 14 16 11 10 11
MPr ₂ VE (mol%) 4.2--5.3-
MPr ₃ VE (mol%) 2 4.2 6.2-5.2
FBrVE (mol%) 0.8 0.8 0.8 0.7 0.8
[Solution viscosity]
ηsp / c (dl / g) 0.60 0.55 0.51 0.65 0.56

[Glass-transition temperature]
Tg (° C) -33.5 -34.2 -35.0 -36.6 -36.9

Further, using the elastomeric copolymers obtained in Comparative Examples 2 to 6, the curable composition was prepared and vulcanized in the same manner as in Comparative Example 1, and the vulcanized product and the vulcanized product were used. The measurement results in each test are shown in the following Table 2 together with the measurement results in Comparative Example 1.
Table 2
Comparative example
Measurement item 1 2 3 4 5 6
[Curing test]
t ₁₀ (min) 0.5 0.5 0.6 0.6 0.6 0.6
t ₉₀ (min) 1.4 1.6 1.6 1.8 1.8 2.5
ML (dN ・ m) 0.8 0.6 0.7 0.4 0.6 1.1
MH (dN ・ m) 13.6 13.9 12.5 11.4 13.3 15.5
[Normal physical properties]
Hardness 72 68 67 68 65 67
100% modulus (MPa)----5.0 6.5
Strength at break (MPa) 9.6 10.4 8.4 7.2 11.6 10.7
Elongation at break (%) 160 160 150 150 170 150
Specific gravity 1.87 1.86 1.86 1.87 1.87 1.87
[Compression set]
200 ° C, 70 hours (%) 39 27 30 29 34 33
[Low temperature characteristics]
TR ₁₀ (° C) -31.7 -32.5 -33.5 -34.3 -33.9 -35.8
TR ₇₀ (℃) -22.8 -24.2 -23.3 -20.1 -23.3 -24.7
[Methanol swelling test]
Volume change rate (%) +21 +13 +20 +15 +39 +33

Examples 1-5, Comparative Example 7
In Comparative Example 1, the amount of sodium sulfite was changed to 0.04 g, the amount of ammonium persulfate was changed to 0.2 g, and the reaction medium, reaction raw materials and reaction conditions were changed as shown in Table 3 below. In Table 3, the production amount of the produced elastomer copolymer, the copolymer composition, the solution viscosity ηsp / c, and the glass transition temperature Tg are also shown. In Comparative Example 7, since the obtained copolymer was not completely dissolved in methyl ethyl ketone, the solution viscosity ηsp / c could not be measured (the measurement as a hexafluorobenzene solution described later was not performed). Absent).
Table 3
Example Comparative Example
1 2 3 4 5 7
[Reaction medium]
Surfactant (g) 40 40 40 40 40 40
Na ₂ HPO ₄・ 12H ₂ O (g) 0.5 0.5 0.5 0.5 0.5 0.5
Ion exchange water (ml) 200 200 200 200 200 200
[Reaction raw materials]
VdF (g) 42 42 42 42 42 42
FMVE (g) 28 24 20 18 24-
MPr ₃ VE (g)----22-
MPr ₄ VE (g) 44 44 44 50 22 68
FBrVE (g) 2 2 2 2 2 2
DIOFB (g) 0.5 0.5 0.5 0.5 0.5 0.5
[Reaction conditions]
Temperature (° C) 50 50 50 50 50 50
Time (hrs) 10 10 10 10 10 10
[Amount of copolymer]
Production amount (g) 114 110 108 115 107 110
[Copolymer composition]
VdF (mol%) 78 80 81 82 80 90
FMVE (mol%) 17 15 14 12 14-
MPr ₃ VE (mol%)---- _3-
MPr ₄ VE (mol%) 4.2 4.2 4.2 5.3 2.2 9
FBrVE (mol%) 0.8 0.8 0.8 0.7 0.8 1.0
[Solution viscosity]
ηsp / c (dl / g) 0.41 0.31 0.45 0.40 0.46 Measurement
Impossible
[Glass-transition temperature]
Tg (° C) -38.6 -39.2 -39.6 -40.2 -38.7 -41.0

Further, using the elastomeric copolymers obtained in Examples 1 to 5 and Comparative Example 7, the curable composition was prepared and vulcanized in the same manner as in Comparative Example 1, and the vulcanized product and vulcanized product were vulcanized. The measurement results in each test conducted for are shown in Table 4 below.
Table 4
Example Comparative Example
Measurement item 1 2 3 4 5 7
[Curing test]
t ₁₀ (min) 0.5 0.5 0.5 0.5 0.5 0.5
t ₉₀ (min) 1.7 1.7 1.7 1.7 1.5 2.0
ML (dN ・ m) 0.4 0.4 0.5 0.3 0.6 0.3
MH (dN ・ m) 10.0 10.0 9.9 9.7 9.7 9.0
[Normal physical properties]
Hardness 67 65 66 68 65 77
100% modulus (MPa) 5.8 5.1 5.5 6.1 5.4 8.0
Strength at break (MPa) 11.8 10.1 12.1 10.9 10.6 9.5
Elongation at break (%) 160 150 150 150 150 120
Specific gravity 1.87 1.87 1.86 1.86 1.87 1.87
[Compression set]
200 ° C, 70 hours (%) 32 30 31 31 30 37
[Low temperature characteristics]
TR ₁₀ (° C) -36.9 -37.5 -37.1 -37.8 -37.4 -38.7
TR ₇₀ (° C) -26.4 -28.4 -26.0 -26.0 -28.4 -1.0
[Methanol swelling test]
Volume change rate (%) +32 +26 +34 +24 +30 +13

Example 6
The inside of a 500 ml stainless steel autoclave was replaced with nitrogen gas, and after deaeration, the following reaction medium was charged.
Surfactant CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) CF ₂ OCF (CF ₃ ) COONH ₄ 40g
Na ₂ HPO ₄・ 12H ₂ 0 0.5g
Ion exchange water 200ml

The inside of the autoclave was again replaced with nitrogen gas, and after deaeration, the following reaction raw materials were charged.
Vinylidene fluoride [VdF] 42g (77.53%)
Perfluoro (methyl vinyl ether) [FMVE] 18g (12.81%)
CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF (CF ₃ ) OCF ₂ CF (CF ₃ ) OCF ₂ CF (CF ₃ ) OCF ₃
[MPr ₄ VE] 65g (9.25%)
CF ₂ = CFI 0.5g (0.28%)
CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ OCF = CF ₂ [FDVE] 0.5g (0.13%)
ICF ₂ CF ₂ CF ₂ CF ₂ I [DIOFB] 0.5g
The percentage in parentheses is mol%.

Next, the temperature inside the autoclave was adjusted to 50 ° C., and 0.1 g of sodium hydrogen sulfite and 0.5 g of ammonium persulfate were added as 3 wt% aqueous solutions to initiate the polymerization reaction. After reacting for 10 hours, cooling, discharging the residual gas, taking out the emulsion, adding 5 wt% aqueous calcium chloride solution to coagulate the polymer, washing with water and drying, the following composition ( ¹⁹ F 123 g of an elastomeric copolymer (by -NMR method) was obtained.
VdF 86 mol%
FMVE 8 mol%
MPr ₄ VE 5.7 mol%
FDVE 0.3 mol%
The resulting elastomer copolymer had a solution viscosity ηsp / c of 0.30 dl / g and a glass transition temperature Tg (measured using SEIKO I SSC5200) of −41.3 ° C.

Example 7
In Example 6, the polymerization reaction was performed under the same conditions except that the following reaction raw materials were used.
VdF 42g (77.64%)
FMVE 18g (12.83%)
MPr ₄ VE 65g (9.27%)
CF ₂ = CFI 0.5g (0.28%)
ICF ₂ CF ₂ CF ₂ CF ₂ I 0.5g
123g resulting elastomeric copolymer is a composition as in Example 6 (VdF 86 mol% with ¹⁹ F-NMR method, FMVE 8 mol%, MPr ₄ VE 6 mol%), the solution viscosity .eta.sp / c was 0.28 dl / g, and the glass transition temperature Tg was −41.6 ° C.

Using the elastomeric copolymers obtained in Examples 6 to 7 above, the curable composition was prepared and vulcanized in the same manner as in Comparative Example 1, and during the vulcanization and the vulcanized product (however, The compression molding temperature is changed to 170 ° C. and the secondary vulcanization time is changed to 4 hours.
Table 5
Measurement item Example 6 Example 7
[Curing test]
t ₁₀ (min) 0.7 0.7
t ₉₀ (min) 1.9 1.9
ML (dN ・ m) 0.3 0.2
MH (dN ・ m) 8.1 6.6
[Normal physical properties]
Hardness 67 66
100% modulus (MPa) 7.1 5.3
Strength at break (MPa) 7.9 8.4
Elongation at break (%) 110 140
Specific gravity 1.87 1.87
[Compression set]
200 ° C, 70 hours (%) 35 44
[Low temperature characteristics]
TR ₁₀ (℃) -39.2 -39.5
TR ₇₀ (℃) -24.7 -25.5
[Methanol swelling test]
Volume change rate (%) +14 +14

Comparative Example 8
In Comparative Example 1, the reaction medium, reaction raw materials, and reaction conditions were changed as shown in Table 6 below. In Table 6, the production amount of the produced elastomer copolymer, the copolymer composition, the solution viscosity ηsp / c, and the glass transition temperature Tg are also shown.
Table 6
Comparative Example 8
[Reaction medium]
Surfactant (g) 30
Na ₂ HPO ₄・ 12H ₂ O (g) 0.5
Ion exchange water (ml) 220
[Reaction raw materials]
VdF (g) 42
FMVE (g) 24
MPr ₂ VE (g) 44
FBrVE (g) 1.0
DIOFB (g) 0.5
[Reaction conditions]
Temperature (℃) 50
Hours (hrs) 12
[Amount of copolymer]
Production amount (g) 110
[Copolymer composition]
VdF (mol%) 80
FMVE (mol%) 13
MPr ₂ VE (mol%) 6.6
FBrVE (mol%) 0.4
[Solution viscosity]
ηsp / c (dl / g) 0.62
[Glass-transition temperature]
Tg (℃) -35.2

Further, the elastomeric copolymer obtained in Comparative Example 8 was used to prepare and vulcanize the curable composition in the same manner as in Comparative Example 1, and during the vulcanization and each test performed on the vulcanized product The measurement results at are shown in Table 7 below.
Table 7
Measurement item comparison example 8
[Curing test]
t ₁₀ (min) 0.5
t ₉₀ (min) 1.7
ML (dN ・ m) 0.4
MH (dN ・ m) 11.0
[Normal physical properties]
Hardness 67
100% modulus (MPa) 3.7
Strength at break (MPa) 9.3
Elongation at break (%) 180
Specific gravity 1.87
[Compression set]
200 ° C, 70 hours (%) 39
[Low temperature characteristics]
TR ₁₀ (℃) -33.1
TR ₇₀ (℃) -23.8
[Methanol swelling test]
Volume change rate (%) +28

Examples 8-10
In Comparative Example 1, the reaction medium, reaction initiator, reaction raw materials, and reaction conditions were changed as shown in Table 8 below. In Table 8, the production amount of the produced elastomer copolymer, the copolymer composition, the solution viscosity ηsp / c, and the glass transition temperature Tg are also shown. If the obtained copolymer does not completely dissolve as a 1 wt% methyl ethyl ketone solution at 35 ° C, measure the solution viscosity ηsp / c as a 1 wt% hexafluorobenzene solution at 35 ° C and add parentheses. And displayed the value.
Table 8
Example 8 Example 9 Example 10
[Reaction medium]
Surfactant (g) 40 40 40
Na ₂ HPO ₄・ 12H ₂ O (g) 0.5 0.5 0.5
Ion exchange water (ml) 180 180 180
[Reaction initiator]
Ammonium persulfate (g) 0.25 0.25 0.25
Na ₂ SO ₃ (g) 0.05 0.05 0.05
[Reaction raw materials]
VdF (g) 24 24 24
TFE (g) 12 12 12
FMVE (g) 14 14 14
MPr ₅ VE (g) 64 72 72
FBrVE (g) 2 2.5 2.5
DIOFB (g) − 0.07 0.14
[Reaction conditions]
Temperature (℃) 33 33 33
Time (hrs) 12 12 12
[Amount of copolymer]
Generated amount (g) 105 113 111
[Copolymer composition]
VdF (mol%) 62 61 61
TFE (mol%) 16 16 16
FMVE (mol%) 11 11 11
MPr ₅ VE (mol%) 10.0 10.7 10.7
FBrVE (mol%) 1.0 1.3 1.3
[Solution viscosity]
ηsp / c (dl / g) (1.38) (0.73) (0.64)
[Glass-transition temperature]
Tg (℃) -40.9 -41.9 -42.6

The elastomeric copolymers obtained in Examples 8 to 10 were used to prepare and vulcanize the curable composition in the same manner as in Comparative Example 1. Table 9 below shows the measurement results in each test performed (the oxide amount was changed to 2 parts, and the secondary vulcanization condition was changed to 230 ° C. and 20 hours).
Table 9
Measurement item Example 8 Example 9 Example 10
[Curing test]
t ₁₀ (min) 0.5 0.5 0.5
t ₉₀ (min) 2.1 1.9 1.9
ML (dN ・ m) 2.6 1.1 0.7
MH (dN ・ m) 11.4 10.0 9.5
[Normal physical properties]
Hardness 62 60 61
100% modulus (MPa) 4.3 3.7 4.8
Strength at break (MPa) 11.5 10.5 9.7
Elongation at break (%) 180 190 170
Specific gravity 1.90 1.90 1.90
[Compression set]
200 ° C, 70 hours (%) 27 35 36
[Low temperature characteristics]
TR ₁₀ (° C) -38.3 -39.6 -40.6
TR ₇₀ (℃) -24.6 -29.4 -29.0
[Methanol swelling test]
Volume change rate (%) +4.0 +4.2 +8.1

Examples 11-15
In Comparative Example 1, the reaction medium, reaction initiator, reaction raw materials, and reaction conditions were changed as shown in Table 10 below. In Table 10, the production amount of the produced elastomer copolymer, the copolymer composition, the solution viscosity ηsp / c, and the glass transition temperature Tg are also shown. ITrFE is
CF ₂ = CFI
It is. The solution viscosities ηsp / c of Examples 11 to 13 and 15 were measured as 1 wt% hexafluorobenzene solutions (35 ° C.) for the same reason as described above.
Table 10
Example
11 12 13 14 15
[Reaction medium]
Surfactant (g) 40 40 40 30 40
Na ₂ HPO ₄・ 12H ₂ O (g) 0.5 0.5 0.5 0.5 0.5
Ion exchange water (ml) 200 170 200 170 200
[Reaction initiator]
Ammonium persulfate (g) 0.25 0.25 0.25 0.13 0.25
Na ₂ SO ₃ (g) 0.05 0.05 0.05 0.02 0.05
[Reaction raw materials]
VdF (g) 26 24 30 34 24
TFE (g) 12 14 8 24 14
FMVE (g) 14 14 14 32 14
MPr ₃ VE (g) − 12 − − −
MPr ₄ VE (g) − 40 64 40 −
MPr ₅ VE (g) 72 12 − − 72
FBrVE (g) 2 2 2 1.5 −
DIOFB (g) − − − 0.25 0.15
ITrFE (g) − − − − 0.50
[Reaction conditions]
Temperature (° C) 33 33 50 50 40
Time (hrs) 12 12 12 12 12
[Amount of copolymer]
Production amount (g) 111 103 112 124 103
[Copolymer composition]
VdF (mol%) 65 62 70 57 61
TFE (mol%) 16 18 10 20 19
FMVE (mol%) 10 10 10 18 10
MPr ₃ VE (mol%) − 2 − − −
MPr ₄ VE (mol%) − 6 9 4.5 −
MPr ₅ VE (mol%) 8 1 − − 9.6
ITrFE (mol%) − − − − 0.4
FBrVE (mol%) 1 1 1 0.5 −
[Solution viscosity]
ηsp / c (dl / g) (3.36) (4.63) (4.83) 0.55 (0.67)
[Glass-transition temperature]
Tg (° C) -41.9 -39.5 -40.0 -35.6 -44.1

Using the elastomeric copolymer obtained in Examples 11 to 15, the curable composition was prepared and vulcanized in the same manner as in Comparative Example 1, and the vulcanized product and the vulcanized product (however, the Examples The amount of organic peroxide in 11-12 is 2 parts, the secondary vulcanization conditions in Examples 11-13 are 230 ° C., 20 hours, the compression molding temperature in Example 14 is 170 ° C., the secondary vulcanization The measurement results in each test (time changed to 4 hours) are shown in Table 11 below.
Table 11
Example
Measurement item 11 12 13 14 15
[Curing test]
t ₁₀ (min) 0.6 0.5 0.5 0.5 0.5
t ₉₀ (min) 2.4 2.4 2.4 1.6 1.9
ML (dN ・ m) 1.3 1.7 1.7 2.4 0.4
MH (dN ・ m) 8.2 9.6 10.0 18.5 7.4
[Normal physical properties]
Hardness 59 61 60 68 62
100% modulus (MPa) 3.0 3.4 2.8 5.1 5.4
Strength at break (MPa) 9.4 9.2 10.1 13.5 7.0
Elongation at break (%) 200 190 220 200 120
Specific gravity 1.90 1.90 1.89 1.88 1.89
[Compression set]
200 ° C, 70 hours (%) 31 31 28 28 27
[Low temperature characteristics]
TR ₁₀ (° C) -39.1 -37.0 -37.9 -33.7 -41.0
TR ₇₀ (℃) -24.1 -23.4 -28.8 -26.9 -28.3
[Methanol swelling test]
Volume change rate (%) +3.3 +3.0 +5.1 +3.4 +3.2

Examples 16-18
In Comparative Example 1, the reaction medium, reaction initiator, reaction raw materials, and reaction conditions were changed as shown in Table 12 below. In Table 12, the production amount of the produced elastomer copolymer, the copolymer composition, the solution viscosity ηsp / c, and the glass transition temperature Tg are also shown. BDFE is
CF ₂ = CHBr
It is. The solution viscosity ηsp / c of Example 16 was measured as a 1 wt% hexafluorobenzene solution (35 ° C.) for the same reason as described above.
Table 12
Example
16 17 18
[Reaction medium]
Surfactant (g) 40 40 40
Na ₂ HPO ₄・ 12H ₂ O (g) 0.5 0.5 0.5
Ion exchange water (ml) 170 210 210
[Reaction initiator]
Ammonium persulfate (g) 0.25 0.45 0.35
NaHSO ₃ (g) 0.05 0.09 0.07
[Reaction raw materials]
VdF (g) 30 28 30
TFE (g) 8 10 8
FMVE (g) 14 20 14
MPr ₄ VE (g) − − 64
MPr ₅ VE (g) 72 30 −
MPr ₆ VE (g) − 10 −
FBrVE (g) 2.5 2.5 −
BDFE (g) − − 1.0
DIOFB (g) − 0.08 0.1
[Reaction conditions]
Temperature (℃) 35 50 50
Time (hrs) 12 12 12
[Amount of copolymer]
Production amount (g) 115 89 109
[Copolymer composition]
VdF (mol%) 70 66 70
TFE (mol%) 10 13 10
FMVE (mol%) 10 15 10
MPr ₄ VE (mol%) − − 9
MPr ₅ VE (mol%) 9 4 −
MPr ₆ VE (mol%) − 1 −
FBrVE (mol%) 1 1 −
BDFE (mol%) − − 1
[Solution viscosity]
ηsp / c (dl / g) (1.23) 0.33 0.10
[Glass-transition temperature]
Tg (℃) -42.5 -38.5 -41.6

Using the elastomeric copolymers obtained in Examples 16 to 18, the curable composition was prepared and vulcanized in the same manner as in Comparative Example 1, and the vulcanized product and the vulcanized product (however, the organic polymer Table 13 below shows the measurement results in each test in which the amount of oxide was changed to 2 parts, and the secondary vulcanization conditions were changed to 230 ° C. and 20 hours, respectively. In Example 18, very slight foaming was observed on the surface of the sheet having a thickness of 2 mm during molding.
Table 13
Example
Measurement item 16 17 18
[Curing test]
t ₁₀ (min) 0.5 0.5 0.5
t ₉₀ (min) 2.6 2.1 3.0
ML (dN ・ m) 2.0 2.1 0.3
MH (dN ・ m) 10.7 16.4 6.4
[Normal physical properties]
Hardness 59 66 58
100% modulus (MPa) 4.5 8.1 3.1
Strength at break (MPa) 11.3 13.9 8.2
Elongation at break (%) 180 140 200
Specific gravity 1.89 1.88 1.88
[Compression set]
200 ° C, 70 hours (%) 24 25 41
[Low temperature characteristics]
TR ₁₀ (° C) -40.3 -36.6 -38.5
TR ₇₀ (℃) -28.7 -27.7 -22.0
[Methanol swelling test]
Volume change rate (%) +4.3 +9.8 +6.0

Claims (14)

Its copolymer composition is
(a) Vinylidene fluoride 50-85 mol%
(b) Tetrafluoroethylene 0-25 mol%
(c) Perfluoro (methyl vinyl ether) 7-20 mol%
(d) CF ₂ = CFO [CF ₂ CF (CF ₃ ) O] nCF ₃ 3-15 mol%
(Where n is an integer from 4 to 6)
(e) RfX (Rf is an unsaturated fluorohydrocarbon group having 2 to 8 carbon atoms, 0.1 to 2 mol%
The group may have one or more ether bonds,
X is bromine or iodine)
A fluorine-containing elastomer.   The fluorine-containing elastomer according to claim 1, wherein the solution viscosity ηsp / c (35 ° C, 1 wt% methyl ethyl ketone solution) is 0.1 to 2 dl / g.   The fluorine-containing elastomer according to claim 1, wherein the solution viscosity ηsp / c (35 ° C, 1 wt% hexafluorobenzene solution) is 0.1 to 7 dl / g.   General formula R (Br) n (I) m (wherein R is a saturated fluorohydrocarbon group or saturated chlorofluorohydrocarbon group having 2 to 6 carbon atoms, n and m are 0, 1 or 2, 2. The fluorine-containing elastomer according to claim 1, which is obtained by copolymerization reaction in the presence of a bromine-containing and / or iodine compound represented by m + n is 2.   The fluorine-containing elastomer according to claim 1 or 4, having a glass transition temperature Tg of -30 to -45 ° C.   The fluorine-containing elastomer according to claim 1 or 4, wherein the total copolymerization amount of the component (c) and the component (d) is 10 mol% or more. The fluorine-containing elastomer according to claim 1 or 4, wherein the component compound (e) is CF ₂ = CFOCF ₂ CF ₂ Br, CF ₂ = CFBr, CF ₂ = CHBr, CF ₂ = CFI or CF ₂ = CHI. The fluorine-containing elastomer according to claim 1 or 4, wherein the bromine-containing and / or iodine compound is ICF ₂ CF ₂ CF ₂ CF ₂ I.   5 to 100 parts by weight of the fluorine-containing elastomer according to claim 1 or 4, 0.1 to 10 parts by weight of an organic peroxide, 0.1 to 10 parts by weight of a polyfunctional unsaturated compound and 2 parts by weight or more of an acid acceptor are added. A fluorine-containing elastomer composition. The fluorine-containing elastomer composition of Claim 9 which gives the vulcanizate which expresses the low temperature characteristic (based on ASTM D1329) shown below after organic peroxide bridge | crosslinking.
-43 ℃ ≦ TR ₁₀ <-30 ℃ <TR ₇₀ ≦ -20 ℃   The fluorine-containing elastomer composition according to claim 9, further comprising 40 parts by weight or less of a flat filler.   A fluororubber-based sealing material obtained by crosslinking and molding the fluorine-containing elastomer composition according to claim 9, 10 or 11.   The fluororubber-based sealing material according to claim 12, which is used as a sealing material for automobile fuel. The fluororubber-based sealing material according to claim 12 or 13, wherein the TR ₁₀ value (according to ASTM D1329) is -30 ° C or less and the methanol swelling ratio (according to JIS K6258; 25 ° C, 168 hours) is within + 50%.