JP4333514B2 - Method for producing vulcanizable fluorine-containing elastomer - Google Patents

Description

  The present invention relates to a method for producing a fluorine-containing elastomer by iodine transfer polymerization under high pressure. Furthermore, it is related with the fluorine-containing elastomer with the high terminal iodine content rate manufactured by this method.

  Since vinylidene fluoride-hexafluoropropylene (VdF-HFP) -based and tetrafluoroethylene (TFE) -perfluorovinyl ether-based fluorine-containing elastomers exhibit their outstanding chemical resistance, solvent resistance, and heat resistance, O-rings, gaskets, hoses, stem seals, shaft seals, diaphragms and the like used in harsh environments are widely used in fields such as the automobile industry, semiconductor industry, and chemical industry.

  As a fluorine-containing elastomer used for such applications, there is an iodine-containing fluorine-containing elastomer having a highly active iodine atom at the molecular end. This iodine-containing fluorine-containing elastomer can have good vulcanization efficiency due to iodine atoms at the molecular terminals, and is excellent in vulcanizability. Further, since it is not necessary to add a chemical substance having a metal component, it is widely used as a peroxide vulcanized product.

  The peroxide vulcanization system (see, for example, Patent Document 1) is excellent in chemical resistance and steam (hot water) resistance, but the compression set resistance is inferior to that of the polyol vulcanization system. It was not suitable as a sealing material. This problem is solved by introducing a vulcanization site into the elastomer main chain (see, for example, Patent Document 2). However, since the vulcanization density increased, the tensile elongation at break was sacrificed. Therefore, it was very difficult to combine both compression set and tensile elongation at break.

In addition, as a method for producing a fluorine-containing elastomer by high-pressure polymerization, a polymerization method in which at least one monomer is in a supercritical state (for example, refer to Patent Document 3), or an emulsification weight in which the monomer concentration in the polymer particles exceeds a reference value. There is a law (for example, see Patent Document 4). However, although there is a description in any patent document that the polymerization in the presence of R _f ¹ · I _x described in the present invention is possible, there is no specific example, and the effects disclosed in the present invention are not mentioned at all. It is not done.

  The iodine-containing fluorine-containing elastomer is produced by an emulsion polymerization method such as a so-called iodine transfer polymerization method (see, for example, Patent Document 5), but in order to achieve a high terminal iodination rate, the amount of polymerization initiator used must be reduced. It is necessary to suppress (see, for example, Non-Patent Document 1), and productivity cannot be increased accordingly. In polymerization systems where there is no restriction on the amount of polymerization initiator used, it is possible to easily increase the polymerization rate by increasing the amount of initiator, but in iodine transfer polymerization systems, the initiator end concentration is large in the physical properties of the final product. It is not possible to increase the amount of initiator used due to the influence.

  Various proposals have been made to improve productivity. For example, a method for improving productivity by continuously performing emulsion polymerization (see, for example, Patent Documents 6 and 7) has been proposed, but good tensile strength and compression that are characteristics of an iodine-containing fluorine-containing elastomer are proposed. Permanent strain cannot be obtained.

  Further, a method of polymerizing at a high pressure of 1.7 MPa or more (gauge pressure; the same applies hereinafter) (for example, see Patent Document 8) has been proposed, but a pressure in the range of 2.6 to 2.7 MPa is considered suitable. In the embodiments, the disclosure is limited to that range. Further, the polymerization time exceeds 15 hours. Furthermore, a microemulsion polymerization method (see, for example, Patent Document 9) has been proposed, but it is necessary to use fluorine oil or the like in order to form a microemulsion in the initial stage. Therefore, cleaning removal is required.

  In order to stabilize the polymerization system or increase the polymerization rate, the amount of emulsifier used may be increased. However, since the emulsifier itself causes vulcanization inhibition, washing and removal are required, and the cost and environment are also reduced. It is not preferable also in terms.

  In order to solve these problems, it has been proposed to perform iodine transfer polymerization by a two-stage emulsion polymerization method (see, for example, Patent Document 10). In the two-stage emulsion polymerization, a large amount of emulsifier is used in the first stage polymerization to synthesize a large number of polymer particles, and then the obtained emulsion is diluted to lower the polymer particle concentration and the emulsifier concentration. This is a method of performing the second stage polymerization using this diluted emulsion. In this method, the polymerization rate can be shortened more than twice while maintaining the original characteristics with a uniform particle size without greatly changing the equipment for emulsion polymerization so far, but no iodine compound is used yet. Productivity is inferior compared with the polymerization method. In addition, the elastomer obtained by this polymerization method does not have a particularly improved portion as compared with the conventional iodine transfer polymerization method, and the above-described problem in sealing performance remains.

  Furthermore, these fluorine-containing elastomers have a large rate of change in viscosity with respect to temperature and are considered to be problematic in terms of workability. In order to reduce such a rate of change in viscosity with respect to temperature, It has been proposed to increase the number of cross-linking sites (see, for example, Patent Documents 11 and 12). In Patent Document 11, a specific bis-olefin is used, and in Patent Document 12, a specific iodine compound is used to increase the number of cross-linking sites. Although polymerization is performed, the processability is improved, but there are problems that the polymerization rate is low and it is difficult to suppress the initiator-derived end groups of the polymer.

  Accordingly, there is no method for producing a fluorine-containing elastomer that satisfies the maintenance of productivity, processability, and various physical properties of the iodine-containing fluorine-containing elastomer.

JP-A-53-125491 JP 62-12734 A International Publication No. 00/47641 Pamphlet International Publication No. 01/34666 Pamphlet Japanese Examined Patent Publication No. 63-41928 JP-A-3-33108 JP-A-3-221510 JP-A-5-222130 Japanese Unexamined Patent Publication No. 63-8406 International Publication No. 00/01741 Pamphlet JP-A-8-12726 International Publication No. 2004/007577 Pamphlet Masayoshi Jianmoto P19, 86/6 Microsymposium, Structural regulation of polymers in radical polymerization, Society of Polymer Science (1986)

  The present invention is a method for producing a fluorine-containing elastomer having a high productivity comparable to the non-iodine transfer polymerization method by performing iodine transfer polymerization under a high pressure, thereby greatly increasing the polymerization rate despite a small amount of polymerization initiator. I will provide a. Furthermore, the fluorine-containing elastomer with high terminal iodine content manufactured by this method is provided.

That is, according to the present invention, the conversion temperature of the critical constant calculated using the Peng-Robinson equation from the critical temperature, the critical pressure, and the composition ratio of each monomer in the gas phase portion in the reaction vessel is 0.95 or more. A method for producing a fluorine-containing elastomer by a batch copolymerization method, which is carried out under a pressure of 0.80 or more, wherein the general formula (1):
R _f ¹ · I _x (1)
(In the formula, R _f ¹ is a saturated or unsaturated fluorohydrocarbon group or chlorofluorohydrocarbon group having ¹ to 16 carbon atoms, and x is the number of bonds of R _f ¹ and is 1 or more and 4 or less. An ethylenically unsaturated compound containing at least one fluoroolefin in the presence of an iodine compound represented by the general formula (2):
CH ₂ = CH (CF ₂ ) _n I (2)
It is related with the manufacturing method of the fluorine-containing elastomer which copolymerizes the compound shown by (In formula, n is an integer of 2-8).

  It is preferable that the tank internal pressure at the time of polymerization is 3 MPa or more.

At the end of the polymerization, the number of fluorine-containing elastomer particles is preferably 5 × 10 ¹³ or more per 1 g of water.

The fluoroolefin is represented by the general formula (3):
CX ¹ X ² = CX ³ X ⁴ (3)
(X ^{1 to} X ³ are a hydrogen atom or a halogen atom, X ⁴ is a hydrogen atom, a halogen atom, a carboxyl group, or an ether bond in which some or all of the hydrogen atoms are substituted with fluorine atoms. An alkyl group which may contain a reactive oxygen atom, or an alkoxy group which may contain an ether-bonded oxygen atom having 1 to 9 carbon atoms and part or all of the hydrogen atoms substituted with fluorine atoms, The olefin is preferably a compound represented by (containing at least one fluorine atom).

  The fluoroolefin is hexafluoropropylene, tetrafluoroethylene, trifluoroethylene, pentafluoropropylene, vinyl fluoride, hexafluoroisobutene, perfluoro (alkyl vinyl ether) s, polyfluorodienes, and general formula (4):

Wherein Y is —CH ₂ I, —OH, —COOH, —SO ₂ F, —SO ₃ M (M is hydrogen, NH ₄ group or alkali metal), carboxylate, carboxyester group, epoxy group, A cyano group, an iodine atom, X ⁵ and X ⁶ are the same or different and each is a hydrogen atom or a fluorine atom; R _f ² is a divalent fluorine-containing alkylene group having 1 to 40 carbon atoms; However, it is preferable to include a compound selected from the group consisting of the same as those in the general formula (2).

  Moreover, this invention relates to the fluorine-containing elastomer obtained by the said manufacturing method.

  The present invention is a method for producing a fluorine-containing elastomer having a high productivity comparable to the non-iodine transfer polymerization method by performing iodine transfer polymerization under a high pressure, thereby greatly increasing the polymerization rate despite a small amount of polymerization initiator. Can be provided. Furthermore, the fluorine-containing elastomer with a high terminal iodine content rate manufactured by this method can be provided.

In the method for producing a fluorine-containing elastomer of the present invention, the conversion temperature of the critical constant calculated from the critical temperature, critical pressure, and composition ratio of each monomer in the gas phase portion in the reaction tank using the Peng-Robinson equation is 0. A method for producing a fluorine-containing elastomer by a batch copolymerization method, which is carried out under a condition of 0.95 or more and a converted pressure of 0.80 or more, wherein the general formula (1):
R _f ¹ · I _x (1)
(In the formula, R _f ¹ is a saturated or unsaturated fluorohydrocarbon group or chlorofluorohydrocarbon group having ¹ to 16 carbon atoms, and x is the number of bonds of R _f ¹ and is 1 or more and 4 or less. An ethylenically unsaturated compound containing at least one fluoroolefin in the presence of an iodine compound represented by the general formula (2):
CH ₂ = CH (CF ₂ ) _n I (2)
It is related with the manufacturing method of the fluorine-containing elastomer which copolymerizes the compound shown by (In formula, n is an integer of 2-8).

  The present invention is a method for producing a fluorine-containing elastomer having a high productivity comparable to the non-iodine transfer polymerization method by performing iodine transfer polymerization under a high pressure, thereby greatly increasing the polymerization rate despite a small amount of polymerization initiator. About. Further, the elastomer produced by this method is copolymerized with the compound represented by the general formula (2), so that the terminal iodine content is high, the compression set is small, the tensile elongation at break is good, and excellent. A fluorine-containing molded product can be provided.

  One feature of the production method of the present invention is that the iodine transfer polymerization method is carried out under high pressure. The iodine transfer polymerization method is not particularly defined, but it is preferable from the viewpoint of productivity to increase the number of fluorine-containing polymer particles at the end of the polymerization. As a means for that, the seed described in International Publication No. 00/01741 pamphlet is used. A polymerization method is preferred.

  Since the reaction vessel used in the present invention performs polymerization under pressure, a pressure vessel is used. An aqueous medium (usually pure water) containing polymer particles having the same composition as that of the target polymer for emulsion polymerization is placed in this reaction tank to form a liquid phase portion.

  The reaction tank is composed of a liquid phase portion and a gas phase portion. After the gas phase portion is replaced with nitrogen or the like, a polymerizable monomer is introduced. Next, the polymerizable monomer is supplied from the gas phase portion to the liquid phase portion by stirring the inside of the reaction vessel, particularly the liquid phase portion. The monomer supplied to the liquid phase part penetrates into the polymer particles and raises the concentration of the polymerizable monomer in the polymer particles. By continuously supplying the monomer to the gas phase part, the monomer concentration in the polymer particles becomes saturated (it can be said that the monomer supply rate to the liquid phase part is in an equilibrium state), so the polymerization initiator and iodine compound are added. To start the polymerization.

  As the polymerization is continued, the monomer is consumed and the monomer concentration in the produced polymer particles decreases, so the monomer (additional monomer) is always supplied into the polymer particles.

  The ratio of the additional monomer depends on the composition of the added monomer and the target polymer, but is preferably a ratio that keeps the monomer composition in the reaction vessel at the initial stage of polymerization constant.

Further, the number of fluoropolymer particles is preferably 5 × 10 ¹³ or more per 1 g of water at the end of the polymerization, and more preferably 1.0 × 10 ¹⁴ or more per 1 g of water. When the number of particles is less than 5 × 10 ¹³ , not only the reaction rate decreases, but also the particle size becomes large and unstable, and the polymer adhesion to the polymerization tank tends to increase.

  As a polymerization method for increasing the number of particles at the end of the polymerization, in addition to the seed polymerization method, a microemulsion method described in JP-B 63-8406, JP-B 62-288609, or a general method As an example, the amount of emulsifier can be increased. Of these, the microemulsion method requires the use of fluorine oil or the like in order to form a microemulsion in the initial stage, so that the oil remains in the product and becomes a source of contamination, which requires cleaning and removal. In addition, an increase in emulsifier is effective for simply stabilizing the polymerization system or increasing the polymerization rate, but foaming is likely to occur before and after polymerization, and the emulsifier remaining in the resulting elastomer is vulcanized. Easy to block. In addition, this method is not preferable in terms of cost and environment. On the other hand, the seed polymerization method does not have the above-described problem, and exhibits an excellent effect in an iodine transfer system.

In the production method of the present invention, a slight error is corrected from the critical temperature and critical pressure of the gas phase monomer mixture derived from the critical temperature, critical pressure and initial monomer composition ratio of each monomer by the Peng-Robinson equation. Conversion temperature 0.95 or more, preferably 0.97 or more, more preferably 0.98 or more, more preferably 1.00 or more, conversion pressure 0.80 or more, preferably 0.85 or more, more preferably 0 Batch polymerization is performed under a condition of .90 or more, more preferably 1.00 or more. When the mixed monomer in the gas phase exceeds both the converted temperature and the converted pressure, it is possible to polymerize at a high monomer density, and the polymerization rate is increased. In addition, the polymer has few main chain branches and ion ends. Therefore, compression set is greatly improved. Here, the converted temperature is
Conversion temperature T _R = T / T _c
(Where T is the actual temperature during polymerization and T _c is the critical temperature calculated using the Peng-Robinson equation)
Similarly, the equivalent pressure is
Conversion pressure P _R = P / P _c
(Where P is the actual pressure during polymerization and P _c is the critical pressure calculated using the Peng-Robinson equation)
Is determined by

  Here, the Peng-Robinson equation for determining the critical temperature and the critical pressure will be described. In general, it is known that the higher the initial monomer density in the polymerization tank, the easier the composition distribution occurs in the polymer obtained, and that the monomer density increases rapidly from the critical point of the initial monomer. However, when copolymerizing two or more monomers, the critical point of the gas phase monomer mixture varies depending on the type and composition ratio of the monomers. The Peng-Robinson equation was employed as a method for calculating the critical point of the mixed monomer from the critical temperature, critical pressure and initial monomer composition ratio of each monomer alone. The principle of this equation is Y. Peng and D.C. B. Robinson, “A New Two-Constant Equation of state”, Ind. Eng. Chem. Fund. , Vol. 15, (1976), p.59-64. The outline is based on the following formula, and a process simulator such as Aspen Plus (manufactured by Aspen Tech) can be used for actual calculation.

  The outline of the Peng-Robinson formula is as follows.

Here, a _i and b _i in the above formula are respectively defined as follows.
a _i = α _i 0.45724R ² T _ci ² / P _ci
α _i (T) = [1 + m _i (1−T _ci ^0.5 )] ²
m _i = 0.37464 + 1.54226ω _i −0.26992ω _i ²
b _i = 0.0778RT _ci / P _ci

Each parameter represents the following.
P: Pressure T: Temperature V _m: volume R: gas constant X _i: composition ratio of the monomer component i T _ci: critical temperature P _ci of the monomer component i: critical pressure of the monomer component i omega _i: eccentricity factor of monomer component i

As a specific calculation example, the critical temperature and critical pressure calculation according to the Peng-Robinson equation when the composition in the polymerization tank is VdF / HFP = 36/64 (mol%) is calculated using Aspen Plus Ver. As a result of using 11.1, T _c = 87.7 ° C. and P _c = 3.05 MPa. When conversion is performed at a conversion temperature of 0.95 and a conversion pressure of 0.80, the polymerization conditions in this case are T = 69.7 ° C. or higher and P = 2.44 MPa or higher.

  Moreover, about the monomer which is 4 weight% or less in a superposition | polymerization tank composition, it is not necessary to consider in calculation by a Peng-Robinson formula.

  When the conversion temperature is less than 0.95 or the conversion pressure is less than 0.80, the monomer concentration in the polymer particles does not reach saturation, the polymerization rate is decreased, and the target polymer tends not to be obtained. There is. Further, among the temperature and pressure satisfying the conditional expression calculated from the above formula, a more preferable polymerization temperature is 10 to 120 ° C, particularly preferably 30 to 100 ° C, and a preferable polymerization pressure is 3 MPa or more, More preferably, it is 3.5 MPa or more, More preferably, it is 4 MPa or more. The upper limit value of the pressure is not particularly limited, but is preferably 15 MPa or less, more preferably 12 MPa or less in consideration of handling of the monomer, reaction equipment cost, and the like.

  Furthermore, it is preferable to stir. This is because the monomer concentration in the polymer particles can be kept high throughout the polymerization by stirring.

  As a means for stirring, for example, an anchor blade, a turbine blade, an inclined blade, or the like can be used. From the viewpoint of good monomer diffusion and polymer dispersion stability, stirring with a large blade called full zone or max blend is preferable.

  The stirring device may be a horizontal stirring device or a vertical stirring device.

  The reaction system has a monomer phase portion substantially. Here, having substantially a monomer phase means that the polymerization is carried out in a state where the volume occupied by a medium such as water is 90% or less, preferably 80% or less, with respect to the volume of the polymerization vessel. When the volume exceeds 90%, it is difficult for the monomer to be supplied to the medium, the polymerization rate tends to decrease, or the polymer physical properties tend to deteriorate.

General formula (1) used in the present invention:
R _f ¹ · I _x (1)
R _f ¹ of the iodine compound represented by the above is a saturated or unsaturated fluorohydrocarbon group or chlorofluorohydrocarbon group having ^{1 to} 16 carbon atoms, and preferably a perfluoroalkyl group having 4 to 8 carbon atoms. . When the carbon number exceeds 16, the reactivity tends to decrease.

X of the iodine compound represented by the general formula (1) is the number of bonds of R _f ¹ , is an integer of 1 or more and 4 or less, and preferably 2 or more and 3 or less. Although it can be used even if x exceeds 4, it is not preferable in terms of synthesis cost. X is most preferably 2 in terms of few polymer branches.

  The carbon-iodine bond of this iodine compound is a relatively weak bond and is cleaved as a radical in the presence of a radical source. Due to the high reactivity of the radicals generated, the monomer undergoes an additional growth reaction, and then the reaction is stopped by extracting iodine from the iodine compound. The fluorine-containing elastomer in which iodine is bonded to the carbon at the molecular terminal thus obtained can be efficiently vulcanized with the terminal iodine as an effective vulcanization point.

Examples of the iodine compound represented by the general formula: R _f ¹ · I _x include monoiodoperfluoromethane, monoiodoperfluoroethane, monoiodoperfluoropropane, monoiodoperfluorobutane [for example, 2-iodoperfluorobutane, 1-iodoperfluoro (1,1-dimethylethane)], monoiodoperfluoropentane [for example, 1-iodoperfluoro (4-methylbutane)], 1-iodoperfluoro-n-octane, monoiodoperfluorocyclobutane, Monoiodoperfluorocyclohexane, monoiodotrifluorocyclobutane, monoiododifluoromethane, monoiodomonofluoromethane, 2-iodo-1-hydroperfluoroethane, 3-iodo-1-hydroperfluoropropane, monoiodomonochloro Fluoromethane, monoiododichloromonofluoromethane, 2-iodo-1,2-dichloro-1,1,2-trifluoroethane, 4-iodo-1,2-dichloroperfluorobutane, 6-iodo-1,2 -Dichloroperfluorohexane, 4-iodo-1,2,4-trichloroperfluorobutane, 1-iodo-2,2-dihydroperfluoropropane, 1-iodo-2-hydroperfluoropropane, monoiodotrifluoro Ethylene, 3-iodoperfluoropropene-1, 4-iodoperfluoropentene-1, 4-iodo-5-chloroperfluoropentene-1, 2-iodoperfluoro (1-cyclobutenylethane), 1,3 -Diiodoperfluoropropane, 1,4-diiodoperfluoro-n-butane, 1,3-diiod 2-chloroperfluoropropane, 1,5-diiodo-2,4-dichloroperfluoro-n-pentane, 1,7-diiodoperfluoro-n-octane, 1,2-di (iododifluoromethyl) per Fluorocyclobutane, 2-iodo-1,1,1-trifluoroethane, 1-iodo-1-hydroperfluoro (2-methylethane), 2-iodo-2,2-dichloro-1,1,1-trifluoro Examples include ethane and 2-iodo-2-chloro-1,1,1-trifluoroethane. Furthermore, the hydrocarbon group of R _f ¹ may contain a functional group such as an ether-bonded oxygen atom, a thioether-bonded sulfur atom, or a carboxyl group, such as 2-iodoperfluoro (ethyl vinyl ether), 2-iodo. Examples thereof include perfluoro (ethyl isopropyl ether), 3-iodo-2-chloroperfluoro (butylmethylthioether), 3-iodo-4-chloroperfluorobutyric acid, and the like.

  Among these, 1,4-diiodoperfluoro-n-butane is preferable from the viewpoint of ease of synthesis, reactivity, economy, and stability.

  These iodine compounds can be appropriately produced by known methods. For example, 2-iodoperfluoropropane is obtained by reacting hexafluoropropene with iodine in the presence of potassium fluoride, and 1,5-diiodo-2,4-dichloroperfluoro-n-pentane is By reacting the silver salt of 5-dichloroperfluoro-1,7-heptanedioic acid with iodine, 4-iodo-5-chloroperfluoro-1-pentene can also be converted to perfluoro-1,4-pentadiene. It can be produced by reacting with iodine chloride.

  The addition amount of the iodine compound is preferably 0.05 to 2.0% by weight with respect to the fluorine-containing elastomer. If the addition amount is less than 0.05% by weight, the vulcanization becomes insufficient and the compression set (CS) tends to deteriorate, and if it exceeds 2.0% by weight, the vulcanization density increases too much. In addition, the rubber performance such as elongation tends to be impaired.

  The iodine compound may be added all at once in the initial stage of polymerization, or may be added in several times.

In addition, the method for producing the fluorine-containing elastomer of the present invention has the general formula (2):
CH ₂ = CH (CF ₂ ) _n I (2)
(Wherein n is an integer of 2 to 8) is copolymerized. Since the fluorine-containing elastomer produced by the production method of the present invention contains the compound represented by the above general formula (2), the crosslink density is increased, the compression permanent strain is small with a high terminal iodine content, and tensile fracture An excellent fluorine-containing molded article having good elongation can be provided.

Compounds represented by the general formula (2) include CH ₂ ═CH (CF ₂ ) ₂ I, CH ₂ ═CH (CF ₂ ) ₃ I, CH ₂ ═CH (CF ₂ ) ₄ I, CH ₂ ═CH ( CF ₂ ) ₅ I, CH ₂ ═CH (CF ₂ ) ₆ I, and the like. Among these, from the viewpoint of handleability, CH ₂ ═CH (CF ₂ ) ₂ I, CH ₂ ═CH (CF _{2 3} I is preferred.

  The compound represented by the general formula (2) is 0.05 to 4% by weight, preferably 0.3 to 3% by weight, more preferably 0.5 to 2% by weight based on the total amount of the obtained fluorine-containing elastomer. % Is preferably included.

  The compound represented by the general formula (2) may be added all at once in the initial stage of polymerization, or may be added in several times.

Examples of the monomer that forms the fluorine-containing elastomer with the iodine compound include at least one fluoroolefin and the general formula (2):
CH ₂ = CH (CF ₂ ) _n I (2)
(Wherein n is an integer of 2 to 8), and may contain an ethylenically unsaturated compound other than the fluoroolefin.

The fluoroolefin used in the present invention, those represented by ^{CX 1 X 2 = CX 3 X} 4 are preferred. In the formula, X ^{1 to} X ³ are a hydrogen atom or a halogen atom, X ⁴ is a hydrogen atom, a halogen atom, a carboxyl group, 1 to 9 carbon atoms, and part or all of the hydrogen atoms are substituted with fluorine atoms The olefin contains at least one fluorine atom, which is an alkyl group or an alkoxy group having 1 to 9 carbon atoms, in which part or all of the hydrogen atoms are substituted with fluorine atoms.

Examples of the fluoroolefin represented by CX ¹ X ² = CX ³ X ⁴ include hexafluoropropylene (HFP), vinylidene fluoride (VdF), tetrafluoroethylene (TFE), trifluoroethylene, pentafluoropropylene, vinyl fluoride, Hexafluoroisobutene, chlorotrifluoroethylene (CTFE), trifluoropropylene, pentafluoropropylene, tetrafluoropropylene, hexafluoroisobutene, perfluoro (alkyl vinyl ether) (PAVE) and the like, but an elastomer composition is easily obtained From vinylidene fluoride (VdF), hexafluoropropylene (HFP), tetrafluoroethylene (TFE), perfluoro (alkyl vinyl ether) (PAVE), Fluoroethylene, hexafluoropropylene, vinyl fluoride, hexafluoroisobutene are preferred.

  Perfluoro (alkyl vinyl ethers) are also preferable in terms of cold resistance and chemical resistance.

  Examples of perfluoro (alkyl vinyl ether) include perfluoro (methyl vinyl ether) (PMVE), perfluoro (ethyl vinyl ether) (PEVE), perfluoro (propyl vinyl ether) (PPVE), and the like.

Moreover, as fluoroolefins other than CX ¹ X ² = CX ³ X ⁴ ,

Or a general formula (4):

Wherein Y is —CH ₂ I, —OH, —COOH, —SO ₂ F, —SO ₃ M (M is hydrogen, NH ₄ group or alkali metal), carboxylate, carboxyester group, epoxy group, A cyano group, an iodine atom, X ⁵ and X ⁶ are the same or different and each is a hydrogen atom or a fluorine atom; R _f ² is a divalent fluorine-containing alkylene group having 1 to 40 carbon atoms; However, the functional group-containing fluoroolefins and polyfluorodienes represented by the general formula (2) are excluded.

  Functional group-containing fluoroolefins are preferred as functional monomers for surface modification and vulcanization density increase, and polyfluorodienes are preferred from the viewpoint of vulcanization efficiency.

  As the functional group-containing fluoroolefin represented by the general formula (4),

Etc.

Moreover, the monomer currently disclosed by patent document 2 as a functional group containing fluoroolefin
CF ₂ = CFOCF ₂ CF ₂ CH ₂ I
Is preferable for the purpose of increasing the crosslinking density, and in particular, when used in combination with the compound represented by the general formula (2), the compression set at a high terminal iodine content is further reduced, and the tensile elongation at break is good. An excellent fluorine-containing molded product can be provided.

Examples of polyfluorodienes include CF ₂ ═CFCF═CF ₂ , CF ₂ ═CFCF ₂ OCF═CF _{2, and the} like.

  Although it does not specifically limit as ethylenically unsaturated compounds other than a fluoro olefin, C2-C10 alpha olefin monomers, such as ethylene (ET), propylene, butene, pentene, methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, cyclohexyl Examples thereof include alkyl vinyl ethers having an alkyl group having 1 to 20 carbon atoms such as vinyl ether, hydroxybutyl vinyl ether and butyl vinyl ether.

  These are preferable in terms of low cost and amine resistance.

Examples of the combination of monomers forming the fluoroelastomer of the present invention, the ^{CX 1 X 2 = CX 3 X} 4 in fluoroolefins represented one or more, the fluoroolefin other than ^{CX 1 X 2 = CX 3 X} 4 1 seed above, there is ^{CX 1 X 2 = CX 3 X} 4 in fluoroolefins one or more indicated and ^{CX 1 X 2 = CX 3 X} 4 other than the fluoroolefin combination comprising at least one, and where each of the combinations As the copolymerization monomer, an ethylenically unsaturated compound other than the fluoroolefin may be contained.

  Among the above-mentioned fluoroolefins and ethylenically unsaturated compounds other than fluoroolefins, an ethylenically unsaturated copolymerizable with vinylidene fluoride (VdF) is used for the purpose of forming a fluorine-containing elastomer having good vulcanizability at low cost. It is preferable to consist of a saturated compound.

  The Mooney viscosity at 100 ° C. of the fluorine-containing elastomer produced by the production method of the present invention is preferably 30 or more, more preferably 35 or more. Compared with a conventional product having the same viscosity by performing peroxide vulcanization. Elongation is large, and compression set (CS) and roll processability are excellent. The higher the viscosity range, the greater the difference from the conventional product in terms of compression set (CS).

  When the Mooney viscosity is less than 30, even in the conventional product, the vulcanization efficiency is increased at the same viscosity, so that the difference from the conventional product tends to be small, but it is not worse than the conventional product.

  The production method of the present invention is suitable for producing a VdF elastomer comprising VdF and other monomers.

  Specifically, in the VdF elastomer, the vinylidene fluoride repeating unit is 20 mol% or more of the total number of moles of the vinylidene fluoride repeating unit and the repeating unit derived from another comonomer in the VdF elastomer. 90 mol% or less is preferable, and 40 mol% or more and 85 mol% or less is more preferable. A more preferred lower limit is 45 mol%, a particularly preferred lower limit is 50 mol%, and a more preferred upper limit is 80 mol%.

The other monomer in the VdF elastomer is not particularly limited as long as it is copolymerizable with VdF. For example, tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoro (alkyl vinyl ether) ( PAVE), chlorotrifluoroethylene (CTFE), trifluoroethylene, trifluoropropylene, tetrafluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutene, vinyl fluoride, iodine-containing fluorinated vinyl ether, etc. Body: non-fluorine-containing monomers such as ethylene (Et), propylene (Pr), alkyl vinyl ether, etc., and one or more of these fluorine-containing monomers and non-fluorine-containing monomers Assembling It can be used Te Align. The PAVE has the general formula (5):
_{CF 2 = CFO (CF 2 CFY} 1 O) p - (CF 2 CF 2 CF 2 O) q -R f 3 (5)
(In the formula, Y ¹ represents a fluorine atom or —CF ₃ , R _f ³ represents a perfluoroalkyl group having 1 to 5 carbon atoms, p represents an integer of 0 to 5, and q represents 0 to 0. 1 can be used alone or in combination of two or more. Among those represented by the general formula (5), perfluoro (methyl vinyl ether) and perfluoro (propyl vinyl ether) are preferable, and perfluoro (methyl vinyl ether) is particularly preferable.

  Examples of the VdF elastomer include VdF / HFP copolymer, VdF / HFP / TFE copolymer, VdF / CTFE copolymer, VdF / CTFE / TFE copolymer, VdF / PAVE copolymer, VdF / TFE / PAVE copolymer, VdF / HFP / PAVE copolymer, VdF / HFP / TFE / PAVE copolymer, VdF / TFE / Pr copolymer, or VdF / Et / HFP copolymer are preferred, but other More preferably, the monomer has TFE, HFP, and / or PAVE, and in particular, VdF / HFP copolymer, VdF / HFP / TFE copolymer, VdF / PAVE copolymer, VdF / TFE / PAVE copolymer, VdF / HFP / PAVE copolymer, or VdF / HFP / TFE / PAVE copolymer If is preferred.

  The VdF / HFP copolymer preferably has a VdF / HFP composition of 45 to 85/55 to 15 (mol%), more preferably 50 to 80/50 to 20 (mol%). More preferably, it is 60-80 / 40-80 (mol%).

  The VdF / HFP / TFE copolymer preferably has a VdF / HFP / TFE composition of 40 to 80/10 to 35/10 to 25 (mol%).

  As the VdF / PAVE copolymer, those having a composition of VdF / PAVE of 65 to 90/10 to 35 (mol%) are preferable.

  As the VdF / TFE / PAVE copolymer, those having a composition of VdF / TFE / PAVE of 40 to 80/3 to 40/15 to 35 (mol%) are preferable.

  As the VdF / HFP / PAVE copolymer, a VdF / HFP / PAVE composition having a composition of 65 to 90/3 to 25/3 to 25 (mol%) is preferable.

  As VdF / HFP / TFE / PAVE copolymer, the composition of VdF / HFP / TFE / PAVE is preferably 40 to 90/0 to 25/0 to 40/3 to 35 (mol%), preferably 40 to 80 More preferable is / 3 to 25/3 to 40/3 to 25 (mol%).

  As described above, the compound represented by the general formula (2) is 0.05 to 4% by weight, preferably 0.3 to 3% by weight, based on the total amount of the VdF-based fluorine-containing elastomer. Preferably 0.5 to 2 wt% is contained.

The fluorine-containing elastomer in the present invention is
(A) containing 0.01 to 10% by weight of iodine atoms in the elastomer;
(B) The polymer number average molecular weight is 1,000 to 300,000,
(C) A fluorine-containing elastomer capable of peroxide vulcanization is preferable.

  Moreover, it is preferable that a fluorine-containing elastomer contains 0.01-10 weight% iodine atom in an elastomer, and it is more preferable that 0.05-2 weight% is included. When the iodine atom content is less than 0.01% by weight, the vulcanization becomes insufficient and the compression set tends to deteriorate, and when it exceeds 10% by weight, the vulcanization density is too high and the elongation is too small. , Rubber performance tends to deteriorate.

  Furthermore, the number average molecular weight of the elastomer is preferably 1,000 to 300,000, and more preferably 10,000 to 200,000. If the molecular weight is less than 1,000, the viscosity tends to be too low and the handleability tends to deteriorate, and if it exceeds 300,000, the viscosity tends to increase and the handleability tends to deteriorate.

  The molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn) is preferably 1.3 or more, and more preferably 1.5 or more. The upper limit of the molecular weight distribution is not particularly limited, but is preferably 8 or less. If the molecular weight distribution is less than 1.3, there is no problem in terms of physical properties, but the roll processability tends to deteriorate. If the molecular weight distribution exceeds 8, there is a tendency for heat generation during the roll process and adhesion to the roll to occur. .

  Moreover, the segmented elastomer obtained by sequentially polymerizing the crystalline segment to the obtained fluorine-containing elastomer is suitably used for thermoplastics and the like.

  The crystalline segment is not particularly limited, and examples thereof include tetrafluoroethylene, perfluoro (propyl) vinyl ether, hexafluoropropylene, ethylene (ET), propylene, and butene.

  In the production method of the present invention, an oil-soluble radical polymerization initiator or a water-soluble radical initiator can be used as the polymerization initiator.

  As the oil-soluble radical polymerization initiator used in the present invention, generally known oil-soluble peroxides are used. For example, dialkyl peroxycarbonates such as diisopropyl peroxydicarbonate and di-sec-butylperoxydicarbonate, Peroxyesters such as t-butylperoxyisobutyrate and t-butylperoxypivalate, dialkyl peroxides such as di-t-butylperoxide, and the like, and di (ω-hydro-dodecafluorohepta) Noyl) peroxide, di (ω-hydro-tetradecafluorooctanoyl) peroxide, di (ω-hydro-hexadecafluorononanoyl) peroxide, di (perfluorobutyryl) peroxide, di (perfluorovale) Ril) peroxide, di (par Fluorohexanoyl) peroxide, di (perfluoroheptanoyl) peroxide, di (perfluorooctanoyl) peroxide, di (perfluorononanoyl) peroxide, di (ω-chloro-hexafluorobutyryl) peroxide Di (ω-chloro-decafluorohexanoyl) peroxide, di (ω-chloro-tetradecafluorooctanoyl) peroxide, ω-hydro-dodecafluoroheptanoyl-ω-hydrohexadecafluorononanoyl peroxide , Ω-chloro-hexafluorobutyryl-ω-chloro-decafluorohexanoyl-peroxide, ω-hydrododecafluoroheptanoyl-perfluorobutyryl-peroxide, di (dichloropentafluorobutanoyl) peroxide , Di (trichlorooctafluorohexanoyl) peroxide, di (tetrachloroundecafluorooctanoyl) peroxide, di (pentachlorotetradecafluorodecanoyl) peroxide, di (undecachlorodotriacontafluorodocosanoyl) Representative examples thereof include di [perfluoro (or fluorochloro) acyl] peroxides such as peroxide.

  However, typical oil-soluble initiators such as di-isopropyl peroxycarbonate (IPP) and di-n-propyl peroxycarbonate (NPP) are explosive and expensive. In addition, since there is a problem that scales such as the wall of the polymerization tank are easily deposited during the polymerization reaction, it is preferable to use a water-soluble radical polymerization initiator.

  As the water-soluble radical polymerizable initiator, generally known water-soluble peroxides are used. For example, ammonium salts such as persulfuric acid, perboric acid, perchloric acid, perphosphoric acid, percarbonate, potassium salts, Examples thereof include sodium salt, t-butyl permaleate, t-butyl hydroperoxide and the like.

  The addition amount of the water-soluble radical initiator is not particularly limited, but an amount that does not significantly reduce the polymerization rate (for example, several ppm with respect to water concentration) or more in the initial stage of polymerization, or sequentially, or What is necessary is just to add continuously. The upper limit is a range in which the heat of polymerization reaction can be removed from the surface of the apparatus.

  In the production method of the present invention, an emulsifier, a molecular weight adjusting agent, a pH adjusting agent and the like may be further added. The molecular weight modifier may be added all at once in the initial stage, or may be added continuously or dividedly.

As the emulsifier, nonionic surfactants, anionic surfactants, cationic surfactants and the like can be used. In particular, as an example of an anionic surfactant, perfluorooctanoic acid (CF ₃ (CF ₂ ) ₆ COOH 1,1,2,2-tetrahydroperfluorohexanesulfonic acid (CF ₃ (CF ₂ ) ₃ CH ₂ CH ₂ SO ₃ H), 1,1,2,2-tetrahydroperfluorooctane sulfonic acid (CF ₃ (CF ₂ ) ₅ CH ₂ CH ₂ SO ₃ H) or its ammonium salt or alkali metal salt is preferred.

  Examples of the molecular weight regulator include esters such as dimethyl malonate, diethyl malonate, methyl acetate, ethyl acetate, butyl acetate, dimethyl succinate, isopentane, isopropanol, acetone, various mercaptans, carbon tetrachloride, cyclohexane, mono Examples thereof include iodomethane, 1-iodoethane, 1-iodo-n-propane, isopropyl iodide, diiodomethane, 1,2-diiodoethane, 1,3-diiodo-n-propane and the like.

  In addition, a buffering agent or the like may be added as appropriate, but the amount is within a range that does not impair the effects of the present invention.

  The fluorine-containing elastomer composition of the present invention comprises such a fluorine-containing elastomer and a vulcanizing agent, and may contain a vulcanization aid.

  What is necessary is just to select suitably as a vulcanizing agent which can be used by this invention by the vulcanization system to employ | adopt. As the vulcanization system, any of a polyamine vulcanization system, a polyol vulcanization system, and a peroxide vulcanization system can be adopted, but the effect of the present invention can be remarkably exhibited especially when vulcanized in a peroxide vulcanization system.

  Examples of the vulcanizing agent include polyhydroxy compounds such as bisphenol AF, hydroquinone, bisphenol A, and diaminobisphenol AF in the polyol vulcanizing system, and α, α'-bis (t-butylperoxy) in the peroxide vulcanizing system. ) Organic peroxides such as diisopropylbenzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, dicumyl peroxide are polymethylene vulcanization systems such as hexamethylenediamine carbamate, N, N And polyamine compounds such as' -dicinnamylidene-1,6-hexamethylenediamine. However, it is not limited to these.

  Among these, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane is preferable from the viewpoints of vulcanizability and handleability.

  The compounding quantity of a vulcanizing agent is 0.01-10 weight part with respect to 100 weight part of elastomers, Preferably it is 0.1-5 weight part. If the vulcanizing agent is less than 0.01 parts by weight, the degree of vulcanization is insufficient, so the performance of the fluorine-containing molded product tends to be impaired. If the amount exceeds 10 parts by weight, the vulcanization density becomes too high. In addition to a long vulcanization time, there is a tendency to be economically undesirable.

  As the vulcanization aid for the polyol vulcanization system, organic bases usually used for vulcanization of elastomers such as various quaternary ammonium salts, quaternary phosphonium salts, cyclic amines and monofunctional amine compounds can be used. Specific examples include quaternary ammonium salts such as tetrabutylammonium bromide, tetrabutylammonium chloride, benzyltributylammonium chloride, benzyltriethylammonium chloride, tetrabutylammonium hydrogensulfate and tetrabutylammonium hydroxide; benzyltriphenylphosphonium chloride , Quaternary phosphonium salts such as tributylallylphosphonium chloride, tributyl-2-methoxypropylphosphonium chloride, benzylphenyl (dimethylamino) phosphonium chloride; monofunctional amines such as benzylmethylamine and benzylethanolamine; 1,8-diazabicyclo [ And cyclic amines such as 5.4.0] -undec-7-ene.

  Peroxide vulcanization aids include triallyl cyanurate, triallyl isocyanurate (TAIC), tris (diallylamine-s-triazine), triallyl phosphite, N, N-diallylacrylamide, hexaallylphospho. Luamide, N, N, N ′, N′-tetraallyltetraphthalamide, N, N, N ′, N′-tetraallylmalonamide, trivinyl isocyanurate, 2,4,6-trivinylmethyltrisiloxane , Tri (5-norbornene-2-methylene) cyanurate and the like. Among these, triallyl isocyanurate (TAIC) is preferable from the viewpoint of vulcanizability and physical properties of the vulcanizate.

  The compounding quantity of a vulcanization auxiliary is 0.01-10 weight part with respect to 100 weight part of elastomers, Preferably it is 0.1-5.0 weight part. If the vulcanization aid is less than 0.01 parts by weight, the vulcanization time tends to be unusable for practical use, and if it exceeds 10 parts by weight, the vulcanization time becomes extremely short and molding is performed. The compression set of the product also tends to decrease.

  Furthermore, usual additives such as fillers, processing aids, carbon black, inorganic fillers, metal oxides such as magnesium oxide, metal hydroxides such as calcium hydroxide, etc. do not impair the object of the present invention. As long as you use.

  The preparation method and vulcanization method of the composition of the present invention are not particularly limited, and conventionally known methods such as compression molding, extrusion molding, transfer molding and injection molding can be employed.

  It is preferable that the tensile elongation at break (Eb) of the molded product obtained by vulcanizing the fluorine-containing elastomer using a vulcanizing agent is 200 to 550%. If the tensile elongation at break is less than 200%, the so-called “rubberiness” is lost, and there is a tendency that it is not suitable as a sealing material. If it exceeds 550%, the vulcanization density is too low and the compression set (CS) deteriorates. Tend.

  Moreover, 5-30% is preferable and, as for the compression set (CS) in 200 degreeC and 72 hours of a molded article, 7-25% is more preferable. If the compression set is less than 5%, the sealing property is good, but generally the elongation tends to be too small, and if it exceeds 30%, the performance as a sealing material tends to deteriorate.

  Here, vulcanization in the present invention refers to vulcanization according to the following standard composition and standard vulcanization conditions.

(Standard formulation)
Fluorine-containing elastomer 100 parts by weight Triallyl isocyanurate (TAIC) 4 parts by weight Perhexa 25B 1.5 parts by weight Carbon black MT-C 20 parts by weight

(Standard vulcanization conditions)
Kneading method: Roll kneading press vulcanization: 10 minutes at 160 ° C Oven vulcanization: 4 hours at 180 ° C

  In the production method of the present invention, compared with the conventional iodine transfer polymerization reaction at a low pressure, the polymerization time was significantly shortened, and the roll processability of the obtained fluorine-containing elastomer was improved. For this reason, when the same Mooney viscosity product is compared between the fluorine-containing elastomer obtained by low-pressure iodine transfer polymerization and the product of the present invention, the vulcanizing agent (TAIC) is precipitated during kneading in the low-pressure product and the rubber is cut. Although there was a tendency to become easier, such a phenomenon was not observed in the product of the present invention.

  A composition comprising a fluorine-containing elastomer and a vulcanizing agent obtained by the present invention comprises a base material-integrated gasket formed by dispenser molding on a base material containing an inorganic material such as a coating agent, metal, ceramic, packing, metal, It is suitably used as a multilayer product formed by coating a base material containing an inorganic material such as ceramic, a gasket for a magnetic recording device, a sealing material for a fuel cell, and a sealing material for a clean facility.

  Next, the present invention will be described with reference to examples, but the present invention is not limited to such examples.

<Weight average molecular weight (Mw) and number average molecular weight (Mn)>
Apparatus: HLC-8000 (manufactured by Tosoh Corporation)
Showa Column: 2 GPC KF-806M
1 GPC KF-801
GPC KF-802 1 detector: Differential refractometer Developing solvent: Tetrahydrofuran Temperature: 35 ° C
Sample concentration: 0.1% by weight
Standard samples: Various monodisperse polystyrene ((Mw / Mn) = 1.14 (Max)), TSK standard POLYSTYRENE (manufactured by Tosoh Corporation)

<Mooney viscosity>
Measured according to ASTM-D1646 and JIS K6300.

Measuring equipment: ALPHA TECHNOLOGIES MV2000E type rotor rotation speed: 2rpm
Measurement temperature: 100 ° C

<Particle number calculation>
Using the measurement result of the average particle diameter of the polymer, the number of particles is calculated from the following formula.

<Composition analysis>
¹⁹ F-NMR (Bruker AC300P type) was used for measurement. However, the TFE-containing polymer was measured using ¹⁹ F-NMR (FX100 type manufactured by JEOL Ltd.).

<Elemental analysis>
Measurement was performed using Yokogawa Hewlett-Packard G2350A.

<Peng-Robinson formula calculation>
Aspen Plus Ver. 11.1 (Aspen Tech) was used. The values built into the software were used for the critical temperature, critical pressure, and eccentricity factor of each monomer.
T _c : VdF 29.65 ° C.
TFE 33.3 ° C,
HFP 85.0 ℃
P _c : VdF 4.46 MPa / SQCM,
TFE 3.94 MPa / SQCM,
HFP 3.21 MPa / SQCM
ω: VdF 0.136,
TFE 0.226,
HFP 0.382

Reference example 1
(Polymerization of seed polymer particles)
As a stirrer, a polymerization tank having an internal volume of 1.8 liters having an electromagnetic induction stirrer was charged with 809 g of pure water and 200 g of a 10 wt% ammonium perfluorooctanoate aqueous solution. I made it. This operation was repeated three times, 0.5 mL of isopentane was charged in a reduced pressure state, the composition in the phase at 80 ° C. was VdF / TFE / HFP = 29.0 / 13.0 / 58.0 (mol%), and the tank internal pressure was 1 Each monomer was charged to 4 MPa. After completion of the temperature increase, 0.67 g of ammonium persulfate (APS) dissolved in 20 g of pure water was injected with nitrogen gas to initiate polymerization. The polymerization pressure was set to 1.4 MPa, and in order to compensate for the pressure drop during the polymerization, a VdF / TFE / HFP mixed monomer (50/20/30 (mol%)) was continuously supplied to carry out the polymerization with stirring. By the end of the polymerization, 320 g of monomer was fed into the tank.

The weight of the obtained emulsion was 1285 g, the polymer concentration was 24.8 wt%, and the number of polymer particles was 1.0 × 10 ¹⁶ particles / water 1 g. After 360 minutes, the stirring was stopped and the monomer was released to stop the polymerization.

Example 1
In a polymerization tank having an internal volume of 1.8 liters having the same electromagnetic induction stirrer as in Reference Example 1, 970 g of pure water and 27 g of an aqueous dispersion of polymer particles prepared in Reference Example 1 were charged, and the system was sufficiently purged with nitrogen. After that, the pressure was reduced. This operation was repeated three times. Under reduced pressure, 18 g of VdF, 22 g of TFE, and 537 g of HFP were charged, and the temperature was raised to 80 ° C. with stirring. Next, 0.05 g of APS dissolved in 2.4 g of octafluoro-1,4-diiodobutane and 15 g of pure water was injected with nitrogen gas to start the polymerization, and the polymerization was continued under the conditions (a) to (d). After 3.4 hours, the stirring was stopped and the monomer was released to stop the polymerization.

(A) Calculation of critical temperature and critical pressure according to the Peng-Robinson equation for the composition VdF / TFE / HFP = 6.5 / 5.0 / 88.5 (mol%) in the polymerization vessel was carried out by Aspen Plus Ver. As a result of using 11.1, T _c = 78.8 ° C. and P _c = 3.32 MPa. Further, when conversion is performed at the conversion temperature T _R 0.95 and the conversion pressure P _R 0.80, T = 61.2 ° C. and P = 2.66 MPa, and the polymerization conditions of this example are equal to or higher than the conversion temperature and the conversion pressure. That's it.
(B) VdF / TFE / HFP (66.6 / 23.7 / 9.7 (mol%)) monomer mixture was continuously fed, and the pressure in the gas phase portion was maintained at 3.5 MPa. When the amount of charged monomer was 50%, 4.29 g of 4-iodo-3,3,4,4-tetrafluorobutene-1 was fed into the tank until the polymerization was completed.
(C) Every time the polymerization time exceeded 3 hours, 0.025 g of APS dissolved in 15 g of pure water was charged.
(D) The stirring speed was maintained at 560 rpm.

The weight of the obtained emulsion was 1414 g, the polymer concentration was 26.3% by weight, and the number of polymer particles was 4.5 × 10 ¹⁴ particles / g water. In addition, the fluorine-containing elastomer is 372 g, the weight average molecular weight Mw measured by GPC is 82,000, the number average molecular weight Mn is 48,000, Mw / Mn is 1.7, and the iodine content is elastomer. The content was 0.40% by weight. Further, the composition of the polymer measured by ¹⁹ F-NMR was VdF / TFE / HFP = 51.2 / 21.1 / 27.6 (mol%).

Claims (6)

The conversion temperature of the critical constant calculated using the Peng-Robinson equation from the critical temperature, critical pressure, and composition ratio of each monomer in the gas phase portion in the reaction vessel is 0.95 or more, and the conversion pressure is 0.80 or more. A process for producing a fluorine-containing elastomer by a batch-type copolymerization method, which is carried out under the conditions of general formula (1):
R _f ¹ · I _x (1)
(In the formula, R _f ¹ is a saturated or unsaturated fluorohydrocarbon group or chlorofluorohydrocarbon group having ¹ to 16 carbon atoms, and x is the number of bonds of R _f ¹ and is 1 or more and 4 or less. An ethylenically unsaturated compound containing at least one fluoroolefin in the presence of an iodine compound represented by the general formula (2):
CH ₂ = CH (CF ₂ ) _n I (2)
(Wherein n is an integer of 2 to 8). The method for producing a fluorine-containing elastomer according to claim 1, wherein the pressure in the tank at the time of polymerization is 3 MPa or more. The method for producing a fluorine-containing elastomer according to claim 1 or 2, wherein the number of the fluorine-containing elastomer particles is 5 x 10 ¹³ or more per 1 g of water at the end of the polymerization. The fluoroolefin is represented by the general formula (3):
CX ¹ X ² = CX ³ X ⁴ (3)
(X ^{1 to} X ³ are a hydrogen atom or a halogen atom, X ⁴ is a hydrogen atom, a halogen atom, a carboxyl group, or an ether bond in which some or all of the hydrogen atoms are substituted with fluorine atoms. An alkyl group which may contain a reactive oxygen atom, or an alkoxy group which may contain an ether-bonded oxygen atom having 1 to 9 carbon atoms and part or all of the hydrogen atoms substituted with fluorine atoms, The method for producing a fluorine-containing elastomer according to claim 1, 2 or 3, wherein the olefin comprises at least one fluorine atom). The fluoroolefin is hexafluoropropylene, tetrafluoroethylene, trifluoroethylene, pentafluoropropylene, vinyl fluoride, hexafluoroisobutene, perfluoro (alkyl vinyl ether) s, polyfluorodienes, and general formula (4):

Wherein Y is —CH ₂ I, —OH, —COOH, —SO ₂ F, —SO ₃ M (M is hydrogen, NH ₄ group or alkali metal), carboxylate, carboxyester group, epoxy group, A cyano group, an iodine atom, X ⁵ and X ⁶ are the same or different and each is a hydrogen atom or a fluorine atom; R _f ² is a divalent fluorine-containing alkylene group having 1 to 40 carbon atoms; 4. The method for producing a fluorine-containing elastomer according to claim 1, comprising a compound selected from the group consisting of: (excluding those identical to the formula (2)). A fluorine-containing elastomer obtained by the production method according to claim 1, 2, 3, 4 or 5.