JP2006070245A - Fluorocopolymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluorocopolymer that is excellent in crosslinking reactivity and gives a crosslinked rubber having excellent physical properties and to provide a crosslinked rubber formed from the fluorocopolymer. <P>SOLUTION: The fluorocopolymer comprises (a) a repeating unit based on one or more kinds of fluoromonomers selected from the group consisting of a tetrafluoroethylene, a hexafluoropropylene, a vinylidene fluoride and CF<SB>2</SB>=CF-O-R<SP>f</SP>, (b) a repeating unit based on a vinyl ester monomer represented by formula: CR<SP>1</SP>R<SP>2</SP>=CR<SP>3</SP>COOCH=CH<SB>2</SB>(for example, a vinyl crotonate) and if necessary, (c) a repeating unit based on one or more kinds of hydrocarbon monomers selected from the group consisting of ethylene, propylene and CH<SB>2</SB>=CH-O-R<SP>4</SP>. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fluorine-containing copolymer.

  Fluoropolymers such as polytetrafluoroethylene, tetrafluoroethylene / hexafluoropropylene copolymer, tetrafluoroethylene / ethylene copolymer, and vinylidene fluoride / hexafluoropropylene copolymer Fluoro rubbers such as tetrafluoroethylene / propylene copolymer and tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer are known.

  Since these fluorine-containing copolymers are excellent in heat resistance and chemical resistance, they are applied to harsh environments where ordinary materials cannot withstand. However, since the fluorine-containing copolymer is poor in reactivity, crosslinking reactivity and adhesion to other materials are not sufficient, and a method for improving reactivity by introducing a reactive functional group has been proposed conventionally. (For example, see Patent Document 1).

  In general, a rubber material needs to exhibit appropriate physical properties by a cross-linking reaction, except for some thermoplastic elastomers. In the fluororubber, a crosslinkable functional group is introduced into the molecule. For vinylidene fluoride / hexafluoropropylene-based copolymers, iodine atoms (for example, see Non-Patent Document 1) and unsaturated bonds (for example, see Patent Document 2) are proposed as reactive functional groups. Has been.

  For a tetrafluoroethylene / propylene copolymer (see, for example, Patent Document 3), which is more excellent in chemical resistance than vinylidene fluoride / hexafluoropropylene copolymer, particularly amine resistance and high temperature steam resistance. A method of copolymerizing a monomer containing a crosslinkable functional group has been proposed, but the effect is not sufficient (see, for example, Patent Document 4). Therefore, there is a demand for the development of a method for introducing a cross-linking reactive functional group into a fluororubber molecule without containing an iodine atom and without a complicated process.

JP-A-11-116634 JP-A 62-56887 JP-A-6-306242 Japanese Examined Patent Publication No. 62-56887 Masayoshi Jianmoto, Polymer Papers, 49 (10), 765-783 (1992)

  An object of the present invention is to provide a fluorine-containing copolymer having excellent crosslinking reactivity and excellent crosslinked rubber properties and a crosslinked rubber thereof.

The present invention is tetrafluoroethylene, hexafluoropropylene, vinylidene _{fluoride, CF 2 = CF-O-} R f ( wherein, ^{R f} is a saturated perfluoroalkyl group or a perfluoro (alkoxyalkyl) group having 1 to 8 carbon atoms A repeating unit (a) based on one or more fluorine-containing monomers selected from the group consisting of: general formula CR ¹ R ² = CR ³ COOCH = CH ₂ (wherein R ¹ and R ² are each Independently, it is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or an alkoxyalkyl group having 1 to 10 carbon atoms containing an etheric oxygen atom, and R ³ is a hydrogen atom, a fluorine atom or a methyl group.) A repeating unit (b) based on a vinyl ester monomer represented by: and, if necessary, ethylene, propylene, CH ₂ ═CH—O—R ⁴ (R ⁴ is a repeating unit (c) based on one or more hydrocarbon monomers selected from the group consisting of a saturated alkyl group or alkoxyalkyl group having 1 to 8 carbon atoms), and (b) / ((a ) + (C)) = 0.0001 to 0.1 (molar ratio). A fluorine-containing copolymer is provided.

Further, the present invention provides the fluorine-containing copolymer, wherein the fluorine-containing copolymer, the vinyl ester monomer and, if necessary, the hydrocarbon monomer are subjected to radical copolymerization in the presence of a radical polymerization initiator. A manufacturing method is provided.
The present invention also provides a crosslinked rubber obtained by crosslinking the fluorine-containing copolymer.

  The fluorine-containing copolymer of the present invention is a fluororubber excellent in rubber elasticity and excellent in cross-linking reactivity, and the cross-linked rubber is excellent in physical properties of the cross-linked rubber and excellent in heat resistance, chemical resistance, weather resistance and the like.

The fluorine-containing copolymer of the present invention contains tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, CF ₂ ═CF—O—R ^f (where R ^f is a saturated perfluoroalkyl group having 1 to 8 carbon atoms, or A repeating unit (a) based on at least one fluorine-containing monomer selected from the group consisting of a perfluoro (alkoxyalkyl) group, a general formula CR ¹ R ² = CR ³ COOCH = CH ₂ (where R ¹ And R ² are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an alkoxyalkyl group having 1 to 10 carbon atoms including an etheric oxygen atom, and R ³ is a hydrogen atom, a fluorine atom or A repeating unit (b) based on a vinyl ester monomer represented by a methyl group), and, if necessary, ethylene, propylene, CH ₂ = CH—O—R ⁴ (R ⁴ is a saturated alkyl group having 1 to 8 carbon atoms or an alkoxyalkyl group) and contains a repeating unit (c) based on one or more hydrocarbon monomers selected from the group consisting of: (B) / ((a) + (c)) = 0.0001 to 0.1 (molar ratio).

  In the fluorine-containing copolymer of the present invention, (c) / (a) = 1/99 to 70/30 (molar ratio) is preferable, and 60/40 to 40/60 (molar ratio) is more preferable. Within this range, the fluorinated copolymer has excellent cross-linked rubber properties, and good heat resistance, chemical resistance, and low-temperature characteristics. Further, as the hydrocarbon monomer, ethylene (hereinafter referred to as E) and propylene (hereinafter referred to as P) are more preferable, and P is most preferable.

Hereinafter, in the fluoromonomer, tetrafluoroethylene is TFE, hexafluoropropylene is HFP, vinylidene fluoride is VdF, CF ₂ = CF—O—R ^f is PAVE, perfluoro (methyl vinyl ether) is PMVE, perfluoro (propyl vinyl ether) Is called PPVE.

Examples of the fluorine-containing copolymer include a TFE / P copolymer, a TFE / P / VdF copolymer, a VdF / HFP copolymer, a TFE / VdF / HFP copolymer, and a TFE / PAVE copolymer. Polymer, TFE / PMVE copolymer, TFE / PPVE copolymer, TFE / PMVE / PPVE copolymer, VdF / PAVE copolymer, E / PAVE copolymer, E / HFP copolymer A polymer etc. are mentioned.
TFE / P copolymer, TFE / P / VdF copolymer, VdF / HFP copolymer, TFE / VdF / HFP copolymer, TFE / PPVE copolymer, TFE / PMVE / PPVE system A copolymer or the like is preferred.

  More preferably, the fluorine-containing copolymer has the following copolymer composition. When the copolymer composition is in the following range, the crosslinked rubber is excellent in physical properties of the crosslinked rubber, and has good heat resistance and chemical resistance, low temperature characteristics, and rubber elasticity.

In TFE / P copolymer, repeating unit based on TFE / repeating unit based on P = 40/60 to 60/40 (molar ratio),
In TFE / P / VdF copolymer, repeating unit based on TFE / repeating unit based on P / repeating unit based on VdF = 40 to 60/60 to 40/1 to 10 (molar ratio),
In the VdF / HFP copolymer, the repeating unit based on VdF / the repeating unit based on HFP = 20/80 to 95/5 (molar ratio),
In TFE / VdF / HFP copolymer, repeating unit based on TFE / repeating unit based on VdF / repeating unit based on HFP = 20-40 / 20-40 / 20-40 (molar ratio),
In TFE / PAVE copolymer, repeating unit based on TFE / repeating unit based on PAVE = 40/60 to 70/30 (molar ratio),
In TFE / PMVE copolymer, repeating unit based on TFE / repeating unit based on PMVE = 40/60 to 70/30 (molar ratio),
In TFE / PPVE copolymer, repeating unit based on TFE / repeating unit based on PPVE = 40/60 to 70/30 (molar ratio),
In TFE / PMVE / PPVE copolymer, repeating unit based on TFE / repeating unit based on PMVE / repeating unit based on PPVE = 40 to 70/3 to 57/3 to 57 (molar ratio),
In the VdF / PAVE copolymer, the repeating unit based on VdF / the repeating unit based on PAVE = 60/40 to 95/5,
In the E / PAVE copolymer, the repeating unit based on E / the repeating unit based on PAVE = 40/60 to 60/40 (molar ratio),
In the E / HFP copolymer, the repeating unit based on E / the repeating unit based on HFP = 40/60 to 60/40 (molar ratio).

In the general formula ^{CR 1 R 2 = CR 3 COOCH} = CH 2 ( wherein in the present invention, ^{R 1} and ^{R 2} include independently a hydrogen atom, an alkyl group or an etheric oxygen atom having 1 to 10 carbon atoms The content of the repeating unit (b) based on the vinyl ester monomer represented by (C) is an alkoxyalkyl group having 1 to 10 carbon atoms, and R ³ is a hydrogen atom, a fluorine atom or a methyl group. /((A)+(c))=0.0001 to 0.1 (molar ratio), (b) / ((a) + (c)) = 0.0001 to 0.05 (molar ratio) Is preferable, and (b) / ((a) + (c)) = 0.005 to 0.05 (molar ratio) is more preferable. Within this range, the fluorinated copolymer is excellent in cross-linking reactivity, and the resulting cross-linked rubber is excellent in cross-linked rubber properties such as tensile strength, chemical resistance, heat resistance, and compression set.

As the vinyl ester monomer, R ² and R ³ are preferably hydrogen atoms. Specific examples include vinyl crotrate in which R ¹ is a methyl group and R ² and R ³ are hydrogen atoms, vinyl pivalate in which R ¹ is a tert-butyl group and R ² and R ³ are hydrogen atoms, and Vinyl methacrylate in which R ¹ , R ² and R ³ are hydrogen atoms is preferable, and vinyl crotonic acid is more preferable.

  The Mooney viscosity of the fluorinated copolymer of the present invention is preferably 20 to 150, more preferably 30 to 150. Mooney viscosity is a measure of molecular weight. A large molecular weight indicates a high molecular weight, and a small molecular weight indicates a low molecular weight. Within this range, the processability of the fluorinated copolymer and the physical properties of the crosslinked rubber are good. The Mooney viscosity is measured according to JIS K6300 using a large rotor with a diameter of 38.1 mm and a thickness of 5.54 mm at 100 ° C. with a preheating time of 1 minute and a rotor rotation time of 4 minutes. Value.

  Examples of the method for producing the fluorinated copolymer of the present invention include emulsion polymerization, solution polymerization, suspension polymerization, bulk polymerization and the like. Moreover, a radical polymerization initiator, a redox polymerization initiator, heat, radiation, etc. can be used for the initiation reaction. Emulsion polymerization is preferred because it is excellent in adjusting the molecular weight and copolymer composition and in productivity.

  As a method for producing the fluorine-containing copolymer of the present invention, radical copolymerization is performed on the fluorine-containing monomer, the vinyl ester monomer, and, if necessary, the hydrocarbon monomer in the presence of a radical polymerization initiator. Moreover, it is preferable to implement radical copolymerization in presence of a chain transfer agent. Furthermore, the radical polymerization is more preferably emulsion polymerization in the presence of an aqueous medium and an emulsifier.

  As the aqueous medium, water or water containing a water-soluble organic solvent is preferable. Examples of the water-soluble organic solvent include tert-butanol, propylene glycol, dipropylene glycol, dipropylene glycol monomethyl ether, and tripropylene glycol. Tert-butanol, propylene glycol, and dipropylene glycol monomethyl ether are preferred. When the aqueous medium contains a water-soluble organic solvent, the content is preferably 1 to 50 parts by mass, more preferably 3 to 20 parts by mass with respect to 100 parts by mass of water.

As the emulsifier, an ionic emulsifier excellent in mechanical and chemical stability of the latex is preferable, and an anionic emulsifier is more preferable. Examples of the anionic emulsifier include hydrocarbon emulsifiers such as sodium lauryl sulfate and sodium dodecylbenzene sulfonate, fluorine-containing alkyl carboxylates such as ammonium perfluorooctanoate and ammonium perfluorohexanoate, and a general formula F (CF ₂ ) _n O ( CF (X) CF ₂ O) _m CF (X) COOA (where X is a fluorine atom or a perfluoroalkyl group having 1 to 3 carbon atoms, A is a hydrogen atom, an alkali metal, NH ₄ , and n is 3 to 10 And m is an integer of 0 or 1 to 3).

As the fluorine-containing emulsifier represented by F (CF ₂ ) _n O (CF (X) CF ₂ O) _m CF (X) COOA, F (CF ₂ ) ₃ O (CF (CF ₃ ) CF ₂ O) ₂ CF (CF ₃ ) COONH ₄ ,
_{F (CF 2) 3 OCF 2} CF 2 OCF 2 COONH 4, F (CF 2) 3 O (CF 2 CF 2 O) 2 CF 2 COONH 4, F (CF 2) 4 OCF 2 CF 2 OCF 2 COONH 4, _{F (CF 2) 4 O (} CF 2 CF 2 O) 2 CF 2 COONH 4, F (CF 2) 3 OCF 2 CF 2 OCF 2 COONa, F (CF 2) 3 O (CF 2 CF 2 O) 2 CF ₂ COONa, F (CF ₂ ) ₄ OCF ₂ CF ₂ OCF ₂ COONa, F (CF ₂ ) ₄ O (CF ₂ CF ₂ O) ₂ CF ₂ COONa, and the like.

As the emulsifier, ammonium perfluorooctanoate, F (CF ₂ ) ₄ OCF ₂ CF ₂ OCF ₂ COONH ₄ , and F (CF ₂ ) ₃ OCF ₂ CF ₂ OCF ₂ COONH ₄ are more preferable.
0.01-15 mass parts is preferable with respect to 100 mass parts of an aqueous medium, and, as for content of an emulsifier, 0.1-10 mass parts is more preferable.

  The radical polymerization initiator used in the emulsion polymerization is preferably a water-soluble initiator, and specific examples thereof include persulfates such as ammonium persulfate, hydrogen peroxide, disuccinic acid peroxide, azobisisobutylamidine disulfide. Organic initiators such as hydrochlorides, redox initiators consisting of a combination of persulfates or hydrogen peroxide and reducing agents such as sodium hydroxymethanesulfinate, sodium bisulfite, sodium thiosulfate, and a small amount of iron Inorganic initiators in which a ferrous salt, silver sulfate and the like are allowed to coexist. Preferred is ammonium persulfate / sodium hydroxymethanesulfinate / ferrous sulfate, and it is more preferable to add ethylenediaminetetraacetic acid disodium salt as a chelating agent to this system. The content of the polymerization initiator is preferably 0.0001 to 3% by mass, more preferably 0.001 to 1% by mass with respect to the monomer used for copolymerization.

  In addition, when using a redox-type initiator, it is preferable to use a pH buffer together. As the pH buffering agent, inorganic salts such as disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium carbonate can be used, disodium hydrogen phosphate dihydrate, disodium hydrogen phosphate dodecahydrate, etc. Is mentioned.

In order to adjust the molecular weight of the fluorine-containing copolymer of the present invention, it is preferable to use a chain transfer agent during polymerization. Examples of the chain transfer agent include alcohols, hydrocarbons, mercaptans, chlorofluorohydrocarbons, R ^f2 I ₂ (where R ^f2 is a saturated polyfluoroalkylene group having 1 to 16 carbon atoms), R ^f3 IBr ( Here, R ^f3 may be a saturated polyfluoroalkylene group having 1 to 16 carbon atoms.

  Examples of alcohols include primary alcohols such as methanol and ethanol, 1-methylpropanol (also referred to as 2-butanol), 1-methylbutanol (also referred to as 2-pentanol), and 1-methylpentanol (also referred to as 2-hexanol). 1) -methylhexanol (also called 2-heptanol), 1-methylheptanol (also called 2-octanol), 1-ethylhexanol (also called 3-octanol), 1-propylpentanol (also called 4-octanol) Secondary alcohols and the like.

Hydrocarbons include methane, ethane, propane, butane, pentane, hexane, cyclohexane and the like.
Examples of mercaptans include tert-dodecyl mercaptan, n-dodecyl mercaptan, and n-octadecyl mercaptan.
Examples of chlorofluorohydrocarbons include 1,3-dichloro-1,1,2,2,3-pentafluoropropane and 1,1-dichloro-1-fluoroethane.

^{Examples of} R ^f2 I ₂ include 1,4-diiodoperfluorobutane. Examples of R ^f3 IBr include 1-bromo-4-iodoperfluorobutane.
As the chain transfer agent, alcohols or hydrocarbons are preferable, and at least one selected from the group consisting of 1-methylpropanol, 1-methylheptanol and propane is more preferable.

  Polymerization conditions such as polymerization pressure and temperature are appropriately selected depending on the monomer composition, the decomposition temperature of the radical polymerization initiator, and the like. Usually, the polymerization pressure is preferably from 0.1 to 20 MPaG, more preferably from 0.3 to 10 MPaG, most preferably from 0.3 to 5 MPaG. The polymerization temperature is preferably 0 to 100 ° C, more preferably 10 to 90 ° C, and most preferably 20 to 80 ° C.

  The fluorine-containing copolymer latex obtained by the emulsion polymerization is aggregated by a known method to isolate the fluorine-containing copolymer. For aggregation, methods such as addition of a metal salt, addition of an inorganic acid such as hydrochloric acid, mechanical shearing, freezing and thawing are used.

  The crosslinked rubber of the present invention is obtained by crosslinking a fluorine-containing copolymer. Usually, a fluorine-containing copolymer is blended with a crosslinking agent, a filler, a crosslinking aid and the like to form a blend, which is molded and thermally crosslinked. As the crosslinking agent, organic peroxides, polyols, amine compounds, and the like are used, and organic peroxides that are particularly excellent in productivity, heat resistance, and chemical resistance of the crosslinked rubber are preferable.

  Specific examples of the organic peroxide include ditert-butyl peroxide, tert-butylcumyl peroxide, dicumyl peroxide, α, α-bis (tert-butylperoxy) -p-diisopropylbenzene, 2,5-dimethyl- Dialkyl peroxides such as 2,5-di (tert-butylperoxy) hexane and 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane-3, 1,1-di (tert-butylperoxy) -3,3,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroxyperoxide, benzoyl peroxide, tert-butylperoxybenzene, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, tert-butylperoxymaleic acid, tert -Butyl peroxy propyl carbonate etc. are mentioned. Dialkyl peroxides are preferred.

  The content of the organic peroxide is preferably 0.3 to 10 parts by mass, more preferably 0.3 to 5 parts by mass, and 0.5 to 3 parts by mass with respect to 100 parts by mass of the fluorine-containing copolymer. Is most preferred. Within this range, a crosslinked rubber having an excellent balance between tensile strength and elongation can be obtained.

  When the fluorine-containing copolymer of the present invention is crosslinked, it is preferable to contain a crosslinking aid. When a crosslinking aid is contained, crosslinking efficiency is high. Specific examples of the crosslinking aid include triallyl cyanurate, triallyl isocyanurate, trimethacryl isocyanurate, 1,3,5-triacryloylhexahydro-1,3,5-triazine, triallyl trimellitate, m -Phenylenediamine bismaleimide, p-quinone dioxime, p, p'-dibenzoylquinone dioxime, dipropargyl terephthalate, diallyl phthalate, N, N ', N ", N" "-tetraallyl terephthalamide, Examples thereof include vinyl group-containing siloxane oligomers such as polymethylvinylsiloxane and polymethylphenylvinylsiloxane. In particular, triallyl cyanurate, triallyl isocyanurate, and trimethallyl isocyanurate are preferable, and triallyl isocyanurate is more preferable.

  0.1-10 mass parts is preferable with respect to 100 mass parts of fluorine-containing copolymers, and, as for content of a crosslinking adjuvant, 0.5-5 mass parts is more preferable. Within this range, crosslinked rubber properties with a good balance between strength and elongation can be obtained.

  Further, when the fluorine-containing copolymer of the present invention is crosslinked, it is also preferable to contain a metal oxide as necessary. By including the metal oxide, the crosslinking reaction can be advanced promptly and reliably. As specific examples of the metal oxide, oxides of divalent metals such as magnesium oxide, calcium oxide, zinc oxide and lead oxide are preferable. 0.1-10 mass parts is preferable with respect to 100 mass parts of a fluorine-containing copolymer, and, as for content of a metal oxide, 0.5-5 mass parts is more preferable. Within this range, crosslinked rubber properties with an excellent balance between strength and elongation can be obtained.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these. The copolymer composition of the fluorinated copolymer, the Mooney viscosity, and the physical properties of the crosslinked rubber were measured by the following methods.
[Copolymerization composition of fluorine-containing copolymer] The fluorine-containing copolymer was dissolved in deuterated tetrahydrofuran, and ¹³ C-NMR was measured to analyze the copolymerization composition.

  [Mooney Viscosity] Viscosity measured according to JIS K6300 using a large rotor with a diameter of 38.1 mm and a thickness of 5.54 mm at 100 ° C. with a preheating time of 1 minute and a rotor rotation time of 4 minutes. Indicates. Larger values indicate higher molecular weight indirectly.

  [Physical Properties of Crosslinked Rubber] For 100 parts by mass of the fluorinated copolymer, 25 parts by mass of carbon black, 3 parts by mass of triallyl isocyanurate, 1,3-bis (tert-butylperoxyisopropyl) benzene (Nippon Oils and Fats) 1 part by mass of Parkardox 14) was kneaded with two rolls, subjected to primary crosslinking for 20 minutes with a hot press at 170 ° C., and subjected to secondary crosslinking for 4 hours in an oven at 200 ° C. The tensile strength and elongation at break of the obtained crosslinked rubber were measured according to JIS K6251. The hardness was measured according to JIS K6253.

[Example 1 (TFE / P / vinyl crotonate copolymer)]
After degassing a 3200 mL stainless steel pressure-resistant reactor equipped with a stirring anchor blade, 1600 g of ion exchange water, 40 g of disodium hydrogen phosphate dodecahydrate, 0.5 g of sodium hydroxide, 97 g of Tert-butanol, 9 g sodium lauryl sulfate, 2.5 g ammonium persulfate were added. Furthermore, an aqueous solution in which 0.4 g of ethylenediaminetetraacetic acid disodium salt dihydrate (hereinafter referred to as EDTA) and 0.3 g of ferrous sulfate heptahydrate was dissolved in 200 g of ion-exchange water in advance. did. Subsequently, a monomer mixed gas of TFE / P = 85/15 (molar ratio) was injected at 40 ° C. so that the internal pressure of the reactor was 2.50 MPaG. An anchor blade was rotated at 300 rpm, and a 2.5% by mass aqueous solution of sodium hydroxymethanesulfinate dihydrate (hereinafter also referred to as Rongalite) adjusted to pH 10.0 with sodium hydroxide (hereinafter referred to as Rongalite 2.). 5% by weight aqueous solution) was added to initiate the polymerization reaction. Thereafter, a 2.5% by mass aqueous solution of Rongalite was continuously added using a high-pressure pump.

  Since the pressure decreases as the polymerization proceeds, when the reactor internal pressure drops to 2.49 MPaG, a mixed gas of TFE / P = 56/44 (molar ratio) is injected under its own pressure, and the reactor internal pressure is reduced to 2 The pressure was increased to 51 MPaG. This was repeated and the internal pressure of the reactor was maintained at 2.49 to 2.51 MPaG, and the polymerization reaction was continued. When the added amount of the TFE / P mixed gas reached 50 g, 4 mL of the previously prepared vinyl crotonate / tert-butanol = 5/95 (mass ratio) solution was injected into the reactor with nitrogen back pressure. did. Thereafter, 4 mL of the tert-butanol solution of vinyl crotonate was added every 20 g until the amount of TFE / P mixed gas added was 330 g, and a total of 60 mL was injected. When the total amount of the TFE / P mixed gas added reached 400 g, the addition of the Rongalite 2.5 mass% aqueous solution was stopped, the reactor internal temperature was cooled to 10 ° C., the polymerization reaction was stopped, and the TFE / P A P / vinyl crotonate copolymer latex was obtained. The amount of Rongalite 2.5 mass% aqueous solution used was 23 g. The polymerization time was about 3.5 hours.

  The latex was added to a 5% by mass aqueous solution of calcium chloride, and the latex was agglomerated by salting out to precipitate a TFE / P / vinyl crotonate copolymer. The copolymer was collected by filtration, washed with ion-exchanged water, and dried in an oven at 120 ° C. for 12 hours to obtain 398 g of a white TFE / P / vinyl crotonate copolymer.

In the infrared spectrum of the copolymer, absorption based on a carbon-carbon double bond was confirmed in the vicinity of 1700 cm ⁻¹ . The composition of the copolymer was repeating unit based on TFE / repeating unit based on P / repeating unit based on vinyl crotonate = 55.3 / 44.7 / 0.17 (molar ratio). The Mooney viscosity was 135. Table 1 shows the physical properties of the crosslinked rubber of the TFE / P / vinyl crotonate copolymer.

[Example 2 (TFE / P / vinyl methacrylate copolymer)]
A TFE / P / vinyl methacrylate copolymer latex was obtained in the same manner as in Example 1 except that vinyl methacrylate was used instead of vinyl crotonate. The amount of Rongalite 2.5 mass% aqueous solution used was 17 g. The polymerization time was about 3 hours.
In the same manner as in Example 1, the latex was salted out, and the precipitated copolymer was washed and dried to obtain 398 g of a white TFE / P / vinyl methacrylate copolymer. In the infrared spectrum of the copolymer, absorption based on a carbon-carbon double bond was confirmed at about 1700 cm ⁻¹ . The composition of the copolymer was a repeating unit based on TFE / a repeating unit based on P / a repeating unit based on vinyl methacrylate = 53.6 / 46.4 / 0.13 (molar ratio). The Mooney viscosity was 145. Table 1 shows the physical properties of the crosslinked rubber of the TFE / P / vinyl methacrylate copolymer.

[Comparative Example 1 (TFE / P copolymer)]
A latex of TFE / P copolymer was obtained in the same manner as in Example 1 except that vinyl crotonate was not used. The amount of Rongalite 2.5 mass% aqueous solution used was 28.5 g. The polymerization time was about 2.8 hours.
In the same manner as in Example 1, the latex was salted out, and the precipitated copolymer was washed and dried to obtain 398 g of a white TFE / P copolymer. The composition of the copolymer was a repeating unit based on TFE / a repeating unit based on P = 55.8 / 44.2 (molar ratio). The Mooney viscosity was 130. Absorption based on a carbon-carbon double bond was not confirmed in the infrared spectrum of the TFE / P copolymer. Table 1 shows the physical properties of the crosslinked rubber of the TFE / P copolymer.

[Example 3 (TFE / P / vinyl crotonate copolymer using 1-methylpropanol as a chain transfer agent)]
After degassing a stainless steel pressure-resistant reactor having an internal volume of 3200 mL equipped with an anchor blade for stirring, 1590 g of ion exchange water, 57 g of disodium hydrogen phosphate 12 hydrate, 1 g of sodium hydroxide, 97 g of tert- Butanol, 9 g sodium lauryl sulfate, 4.2 g ammonium persulfate, 9 g 1-methylpropanol were added. Furthermore, an aqueous solution in which 0.4 g of EDTA and 0.3 g of ferrous sulfate heptahydrate were dissolved in 200 g of ion-exchanged water in advance was added. Subsequently, a monomer mixed gas of TFE / P = 88/12 (molar ratio) was injected at 40 ° C. so that the internal pressure of the reactor was 2.50 MPaG. The anchor blade was rotated at 300 rpm, and a Rongalite 4.6 mass% aqueous solution adjusted to pH 10.0 with sodium hydroxide was added to initiate the polymerization reaction. Thereafter, Rongalite 4.6 mass% aqueous solution was continuously added using a high-pressure pump.

  Since the pressure decreases as the polymerization proceeds, when the reactor internal pressure drops to 2.49 MPaG, a mixed gas of TFE / P = 56/44 (molar ratio) is injected under its own pressure, and the reactor internal pressure is reduced to 2 The pressure was increased to 51 MPaG. This was repeated and the internal pressure of the reactor was maintained at 2.49 to 2.51 MPaG, and the polymerization reaction was continued. 1 mL of a vinyl crotonate / tert-butanol = 4/96 (mass ratio) solution prepared in advance when the added amount of the TFE / P mixed gas reached 10 g was injected into the reactor with nitrogen back pressure. . Thereafter, 1 mL of the vinyl crotonate / tert-butanol solution was added every 10 g until the addition amount of the TFE / P mixed gas was 390 g, and a total of 39 mL was injected. When the total amount of the TFE / P mixed gas added reached 400 g, the addition of the Rongalite 4.6 mass% aqueous solution was stopped, the reactor internal temperature was cooled to 10 ° C., the polymerization reaction was stopped, and the TFE / P A P / vinyl crotonate copolymer latex was obtained. The amount of Rongalite 4.6 mass% aqueous solution used was 26 g. The polymerization time was about 4 hours.

  In the same manner as in Example 1, the latex was salted out, and the precipitated copolymer was washed and dried to obtain 390 g of a white TFE / P / vinyl crotonate copolymer.

In the infrared spectrum of the copolymer, absorption based on a carbon-carbon double bond was confirmed in the vicinity of 1700 cm ⁻¹ . The composition of the copolymer was TFE-based repeating units / P-based repeating units / vinyl crotonate-based repeating units = 54.7 / 45.3 / 0.20 (molar ratio). The Mooney viscosity was 82. Table 1 shows the physical properties of the crosslinked rubber of the TFE / P / vinyl crotonate copolymer.

[Example 4 (TFE / P / vinyl crotonate copolymer using 1-methylheptanol as a chain transfer agent)]
A TFE / P / vinyl crotonate copolymer latex was obtained in the same manner as in Example 3 except that 5.4 g of 1-methylheptanol was used instead of 9 g of 1-methylpropanol. The amount of Rongalite 4.6 mass% aqueous solution used was 24 g. The polymerization time was about 3.5 hours.

  In the same manner as in Example 1, the latex was salted out, and the precipitated copolymer was washed and dried to obtain 390 g of a white TFE / P / vinyl crotonate copolymer.

In the infrared spectrum of the copolymer, absorption based on a carbon-carbon double bond was confirmed in the vicinity of 1700 cm ⁻¹ . The composition of the copolymer was: repeating unit based on TFE / repeating unit based on P / repeating unit based on vinyl crotonate = 55.5 / 44.5 / 0.19 (molar ratio). The Mooney viscosity was 70. Table 1 shows the physical properties of the crosslinked rubber of the TFE / P / vinyl crotonate copolymer.

[Example 5 (TFE / P / vinyl crotonate copolymer using propane as a chain transfer agent)]
After degassing a 3200 mL stainless steel pressure-resistant reactor equipped with a stirring anchor blade, 1600 g of ion exchange water, 40 g of disodium hydrogen phosphate dodecahydrate, 0.5 g of sodium hydroxide, 97 g of Tert-butanol, 9 g sodium lauryl sulfate, 2.5 g ammonium persulfate were added. Furthermore, an aqueous solution in which 0.4 g of EDTA and 0.3 g of ferrous sulfate heptahydrate were dissolved in 200 g of ion-exchanged water in advance was added. Next, at 40 ° C., a monomer mixed gas of TFE / P / propane = 85/12/3 (molar ratio) was injected so that the internal pressure of the reactor was 2.60 MPaG. The anchor blade was rotated at 300 rpm, and a Rongalite 4.6 mass% aqueous solution was added to initiate the polymerization reaction. Thereafter, Rongalite 4.6 mass% aqueous solution was continuously added using a high-pressure pump.

  Since the pressure decreases as the polymerization proceeds, when the reactor internal pressure drops to 2.59 MPaG, a mixed gas of TFE / P / propane = 51/40/9 (molar ratio) is injected under its own pressure to react. The internal pressure was increased to 2.61 MPaG. This was repeated and the internal pressure of the reactor was maintained at 2.59 to 2.61 MPaG to continue the polymerization reaction. 1 mL of a vinyl crotonate / tert-butanol = 3.9 / 96.1 (mass ratio) solution prepared in advance when the amount of the TFE / P / propane mixed gas reached 10 g was placed in the reactor. Injected with nitrogen back pressure. Thereafter, 1 mL of the tert-butanol solution of vinyl crotonate was added every 10 g until the addition amount of the TFE / P / propane mixed gas was 390 g, and a total of 39 mL was injected. When the total amount of the TFE / P / propane mixed gas reached 400 g, the addition of the Rongalite 4.6 mass% aqueous solution was stopped, the reactor internal temperature was cooled to 10 ° C., and the polymerization reaction was stopped. A TFE / P / vinyl crotonate copolymer latex was obtained. The amount of Rongalite 4.6 mass% aqueous solution used was 26 g. The polymerization time was about 4 hours.

  The latex was salted out in the same manner as in Example 1, and the precipitated copolymer was washed and dried to obtain 365 g of a white TFE / P / vinyl crotonate copolymer.

In the infrared spectrum of the copolymer, absorption based on a carbon-carbon double bond was confirmed in the vicinity of 1700 cm ⁻¹ . The composition of the copolymer was: repeating unit based on TFE / repeating unit based on P / repeating unit based on vinyl crotonate = 55.1 / 44.9 / 0.19 (molar ratio). The Mooney viscosity was 54. Table 1 shows the physical properties of the crosslinked rubber of the TFE / P / vinyl crotonate copolymer.

[Example 6 (TFE / P / vinyl crotonate copolymer using propane as a chain transfer agent)]
After degassing a 3200 mL stainless steel pressure-resistant reactor equipped with a stirring anchor blade, 1600 g of ion exchange water, 40 g of disodium hydrogen phosphate dodecahydrate, 0.5 g of sodium hydroxide, 97 g of Tert-butanol, 9 g sodium lauryl sulfate, 2.5 g ammonium persulfate were added. Furthermore, an aqueous solution in which 0.4 g of EDTA and 0.3 g of ferrous sulfate heptahydrate were dissolved in 200 g of ion-exchanged water in advance was added. Next, at 40 ° C., a monomer mixed gas of TFE / P / propane = 85/12/3 (molar ratio) was injected so that the internal pressure of the reactor was 2.60 MPaG. The anchor blade was rotated at 300 rpm, and a Rongalite 4.6 mass% aqueous solution was added to initiate the polymerization reaction. Thereafter, Rongalite 4.6 mass% aqueous solution was continuously added using a high-pressure pump.

  Since the pressure decreases as the polymerization proceeds, when the reactor internal pressure drops to 2.59 MPaG, a mixed gas of TFE / P = 56/44 (molar ratio) is injected under its own pressure, and the reactor internal pressure is reduced to 2 The pressure was increased to 61 MPaG. This was repeated and the internal pressure of the reactor was maintained at 2.59 to 2.61 MPaG to continue the polymerization reaction. 1 mL of a vinyl crotonate / tert-butanol = 4/96 (mass ratio) solution prepared in advance when the added amount of the TFE / P mixed gas reached 10 g was injected into the reactor with nitrogen back pressure. . Thereafter, 1 mL of the tert-butanol solution of vinyl crotonate was added every 10 g until the addition amount of the TFE / P mixed gas was 390 g, and a total of 39 mL was injected. When the total amount of the TFE / P mixed gas added reached 400 g, the addition of the Rongalite 4.6 mass% aqueous solution was stopped, the reactor internal temperature was cooled to 10 ° C., the polymerization reaction was stopped, and the TFE / P A P / vinyl crotonate copolymer latex was obtained. The amount of Rongalite 4.6 mass% aqueous solution used was 26 g. The polymerization time was about 4 hours.

  In the same manner as in Example 1, the latex was salted out, and the precipitated copolymer was washed and dried to obtain 390 g of a white TFE / P / vinyl crotonate copolymer.

In the infrared spectrum of the copolymer, absorption based on a carbon-carbon double bond was confirmed in the vicinity of 1700 cm ⁻¹ . The composition of the copolymer was: repeating unit based on TFE / repeating unit based on P / repeating unit based on vinyl crotonate = 55.1 / 44.9 / 0.19 (molar ratio). The Mooney viscosity was 80. Table 1 shows the physical properties of the crosslinked rubber of the TFE / P / vinyl crotonate copolymer.

[Example 7 (TFE / P / vinyl pivalate copolymer)]
The same procedure as in Example 1 was used except that a vinyl pivalate / tert-butanol = 4.6 / 93.7 (mass ratio) solution was used instead of the vinyl crotonate / tert-butanol = 4/96 (mass ratio) solution. Thus, a TFE / P / vinyl pivalate copolymer latex was obtained. The amount of Rongalite 4.6 mass% aqueous solution used was 17 g. The polymerization time was about 3.5 hours.
The latex was salted out in the same manner as in Example 1, and the precipitated copolymer was washed and dried to obtain 392 g of a white TFE / P / vinyl pivalate copolymer. In the infrared spectrum of the copolymer, absorption based on a carbon-carbon double bond was confirmed at about 1700 cm ⁻¹ . The composition of the copolymer was: repeating unit based on TFE / repeating unit based on P / repeating unit based on vinyl pivalate = 56.1 / 43.9 / 0.18 (molar ratio). The Mooney viscosity was 99. Table 1 shows the physical properties of the crosslinked rubber of the TFE / P / vinyl pivalate copolymer.

  The TFE / P / vinyl crotonate copolymers of Examples 1 to 6 obtained by copolymerizing vinyl crotonate as the vinyl ester monomer were all excellent in cross-linking reactivity and exhibited excellent cross-linked rubber properties. On the other hand, the TFE / P copolymer of Comparative Example 1 that does not contain a unit based on a vinyl ester monomer has low tensile strength and hardness, and has insufficient crosslinked rubber properties and crosslinking reactivity. In the TFE / P / vinyl pivalate copolymer (Example 7) obtained by copolymerizing vinyl pivalate as a vinyl ester monomer, a crosslinked rubber excellent in elongation was obtained.

The crosslinked rubber of the fluorinated copolymer of the present invention is used for O-rings, sheets, gaskets, oil seals, diaphragms, and V-rings. It can also be applied to applications such as heat-resistant and chemical-resistant sealing materials, wire coating materials, semiconductor device sealing materials, corrosion-resistant rubber paints, and urea-based grease sealing materials.

Claims (9)

Tetrafluoroethylene, hexafluoropropylene, vinylidene _{fluoride, CF 2 = CF-O-} R f ( wherein, ^{R f} is a saturated perfluoroalkyl group or a perfluoro (alkoxyalkyl) group having 1 to 8 carbon atoms.) A repeating unit (a) based on one or more fluorine-containing monomers selected from the group consisting of: general formula CR ¹ R ² = CR ³ COOCH = CH ₂ (wherein R ¹ and R ² are each independently hydrogen An atom, an alkyl group having 1 to 10 carbon atoms, or an alkoxyalkyl group having 1 to 10 carbon atoms including an etheric oxygen atom, and R ³ is a hydrogen atom, a fluorine atom, or a methyl group. repeating units based on vinyl ester monomer (b), and optionally, ethylene, ^{_{propylene, CH 2 = CH-O-}} R 4 (R 4 A repeating unit (c) based on one or more hydrocarbon monomers selected from the group consisting of a saturated alkyl group having 1 to 8 carbon atoms or an alkoxyalkyl group), (b) / ((a) + (c) ) = 0.0001 to 0.1 (molar ratio).   2. The fluorine-containing copolymer according to claim 1, comprising the repeating unit (c), wherein (c) / (a) = 1/99 to 70/30 (molar ratio). The fluorine-containing copolymer according to claim 1, wherein R ² and R ³ are hydrogen atoms in the vinyl ester monomer.   The fluorine-containing copolymer according to claim 1 or 2, wherein the vinyl ester monomer is vinyl crotonate.   The fluorine-containing monomer is tetrafluoroethylene, the hydrocarbon monomer is propylene, and (c) / (a) = 40/60 to 60/40 (molar ratio), (b) / ((a) The fluorine-containing copolymer according to claim 1, wherein + (c)) = 0.0001 to 0.05 (molar ratio).   The fluorinated monomer, the vinyl ester monomer, and optionally the hydrocarbon monomer are subjected to radical copolymerization in the presence of a radical polymerization initiator. A method for producing a fluorine copolymer.   The method for producing a fluorinated copolymer according to claim 6, wherein the radical copolymerization is emulsion polymerization in the presence of an aqueous medium and an emulsifier.   The method for producing a fluorinated copolymer according to claim 6 or 7, wherein the radical copolymerization is polymerization in the presence of a chain transfer agent, and the chain transfer agent is an alcohol or a hydrocarbon. A crosslinked rubber obtained by crosslinking the fluorine-containing copolymer according to claim 1.