New compound, crosslinking agent and crosslinked fluoroelastomer

Abstract

To provide a crosslinked fluoroelastomer improved in high-temperature steam resistance.SOLUTION: The crosslinked fluoroelastomer does not contain an unsaturated bond other than aromatic rings in a crosslinked structure, and a linking group linking the aromatic rings is a perfluoroalkylene. The crosslinked fluoroelastomer preferably has a gel fraction of 45% or more after being exposed to saturated water vapor at 330°C for 24 hours. The crosslinked fluoroelastomer can be used as a sealing material by being formed into a molding.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to novel compounds useful as crosslinking agents, and to crosslinked fluoroelastomers obtained using said agents. [Background technology]

[0002] Sealing materials made of crosslinked fluoroelastomers are used as sealing materials suitable for heat resistance, steam resistance, and rapid decompression resistance. Various crosslinking agents are known as crosslinking agents for crosslinked fluoroelastomers. For example, there are triallyl isocyanurate (TAIC) and 1,6-divinylperfluorohexane (see Patent Documents 1 and 2).

[0003] In recent years, power plants have tended to raise the temperature of steam to higher levels than before in order to improve power generation efficiency, and as a result, sealing materials are also required to be resistant to higher temperature steam. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 98 / 00407 [Patent Document 2] JP 2006-9010 A Summary of the Invention

[0005] The fluoroelastomer, which is the base material of the crosslinked fluoroelastomer, has sufficient resistance to high-temperature steam. On the other hand, the crosslinking points, which are the bonding parts between the crosslinking agent and the fluoroelastomer in Patent Documents 1 and 2, contain bonds that are weak against heat and steam, so they cannot be said to have sufficient resistance to high-temperature steam, and are the cause of decomposition and deterioration. An object of the present invention is to provide a crosslinking agent capable of improving the high temperature steam resistance of crosslinked fluoroelastomers, and a crosslinked fluoroelastomer having improved high temperature steam resistance.

[0006] According to the present invention, the following compounds and the like are provided: 1. A compound having a structure represented by the following formula (1): [ka] (In the formula, R 1 ~R 6 are each hydrogen, a substituent or a leaving group, R 1 ~R 6 Two or more of R are leaving groups. a ~R c are each hydrogen or a substituent, and n is an integer of 2 to 5. 2. The compound according to 1, which is a compound represented by the following formula (2A): [ka] (In the formula, R 1 ~R 6 , R 11 ~R 16 are each hydrogen, a substituent or a leaving group, R 1 ~R 6 are leaving groups, and R 11 ~R 16 At least two of A are leaving groups. 1 is a single bond or a linking group. 3. The compound according to 2, which is a compound represented by the following formula (2B): [ka] (In the formula, R 1 , R 6 , R 11 and R 16 are leaving groups. A 1 is the same as formula (2A). 4.A 1 is a single bond, -O-, -S-, a heteroatom-containing group, a straight-chain alkylene group, a branched alkylene group, a cycloalkylene group, a fluorinated alkylene group or an arylene group. 5. The compound according to any one of 1 to 4, wherein the leaving group is a group selected from a halogen atom, a hydroxyl group, an alkoxy group, a carbonyl-containing group, a phosphorus-based substituent, a sulfur-based substituent, primary to tertiary amino groups, a cyano group, and a nitro group. 6. A crosslinking agent comprising the compound according to any one of 1 to 5. 7. A composition comprising a fluoroelastomer, a crosslinking initiator, and the crosslinking agent according to 6. 8. A crosslinked fluoroelastomer obtained by crosslinking the composition according to 7. 9. A method for producing a crosslinked fluoroelastomer, comprising the steps of heating the composition described in 7 to react the fluoroelastomer with the crosslinking agent, and converting the cyclohexane rings derived from the crosslinking agent into aromatic rings. 10. A crosslinked fluoroelastomer produced by the method of 9, having a gel fraction of 45% or more after exposure to saturated water vapor at 330°C for 24 hours. 11. A crosslinked fluoroelastomer having a gel fraction of 45% or more after exposure to saturated water vapor at 330°C for 24 hours. 12. The crosslinked fluoroelastomer according to 11, which does not contain any unsaturated bond other than an aromatic ring in the crosslinked structure. 13. A molded article obtained from the crosslinked fluoroelastomer according to any one of 8 and 10 to 12. 14. The molded article according to 13, which is a sealing material.

[0007] According to the present invention, there can be provided a crosslinking agent capable of improving the high-temperature steam resistance of a crosslinked fluoroelastomer, and a crosslinked fluoroelastomer having improved high-temperature steam resistance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [Compounds and crosslinked bodies] A compound according to one embodiment of the present invention has a structure represented by formula (1): [ka] (In the formula, R 1 ~R 6 are each hydrogen, a substituent or a leaving group, R 1 ~R6 Two or more of R are leaving groups. a ~R c are each hydrogen or a substituent, and n is an integer of 2 to 5.

[0009] The compound of the present embodiment is useful, for example, as a crosslinking agent. In the above structure, the double bond of the cyclohexene ring reacts with the reactive site of the fluoroelastomer, resulting in a structure in which the fluoroelastomer and the cyclohexane ring are directly bonded. After that, the cyclohexane ring is converted into an aromatic ring, and compared with the conventional crosslinking structure, for example, the crosslinking structure obtained by a crosslinking agent having a vinyl group or a fluorovinyl group, the high-temperature steam resistance is improved because it does not contain a bond that is weak against heat or steam.

[0010] In formula (1), R 1 ~R 6 are each hydrogen, a substituent, or a leaving group. The substituent is not particularly limited as long as it is a group other than the leaving group described later and does not impair the effects of the present invention. Examples of the substituent include an alkyl group, a cycloalkyl group, and an aryl group. The alkyl group may be linear or branched and preferably has 1 to 15 carbon atoms (more preferably has 1 to 6 carbon atoms). The cycloalkyl group preferably has 3 to 8 carbon atoms (more preferably has 3 to 6 carbon atoms). The aryl group preferably has 6 to 18 carbon atoms (more preferably has 6 to 12 carbon atoms). Examples of the aryl group include phenyl and naphthyl. The carbon atoms of the substituents may be partially or fully fluorinated.

[0011] The leaving group is a group that has a function of being eliminated from a cyclohexane ring by an operation such as heating, thereby converting the cyclohexane ring into an aromatic ring. Specific examples thereof include a halogen atom, a hydroxyl group, an alkoxy group, a carbonyl-containing group, a phosphorus-based substituent, a sulfur-based substituent, a primary to tertiary amino group, a cyano group, and a nitro group.

[0012] Examples of the halogen atom include I, Br, Cl, and F. The alkoxy group is -OR x1R x1 Examples of the alkyl group include an alkyl group, a cycloalkyl group, and an aryl group. Preferred are alkyl groups such as a methyl group, an ethyl group, an n-propyl group, and an isopropyl group.

[0013] The carbonyl-containing group is preferably a formyl group, a carboxy group, -C(=O)R x2 A carbonyl group represented by -C(=O)OR x2 R is an alkoxycarbonyl group represented by the formula: x2 Examples of the alkyl group include an alkyl group, a cycloalkyl group, and an aryl group. R x2 is preferably an alkyl group such as a methyl group, an ethyl group, an n-propyl group, or an isopropyl group.

[0014] Examples of the phosphorus-based substituent include a phosphoryl group, a phosphinyl group, and a phosphanyl group. Examples of the sulfur-based substituent include a sulfonic acid group, a sulfonyl group, a sulfinyl group, a sulfenyl group, and a mercapto group. Specifically, the sulfonyl group is -S(=O)R x3 , sulfinyl group is -S(=O)R x3 , sulfenyl group is -SR x3 R is preferably a group represented by the formula: x3 Examples of the alkyl group include an alkyl group, a cycloalkyl group, and an aryl group. R x3 is preferably an alkyl group such as a methyl group, an ethyl group, an n-propyl group, or an isopropyl group.

[0015] The leaving group is particularly preferably a hydroxyl group or an alkoxy group.

[0016] In one embodiment, the compound having the structure represented by formula (1) is represented by formula (2): [ka] (In the formula, R 1 ~R 6 , R a ~Rc is the same as equation (1). A 1 is a single bond or a linking group. 1 ~R 6 and R a ~R c may be the same or different.)

[0017] Examples of the linking group include -O-, -S-, a heteroatom-containing group, a straight-chain alkylene group, a branched alkylene group, a cycloalkylene group, a fluorinated alkylene group, and an arylene group. The linear or branched alkylene group preferably has 1 to 15 carbon atoms (more preferably 1 to 6 carbon atoms). The cycloalkylene group preferably has 3 to 8 carbon atoms (more preferably 3 to 6 carbon atoms). The arylene group preferably has 6 to 18 carbon atoms (more preferably 6 to 12 carbon atoms). These groups may be partially or fully fluorinated, for example, the cycloalkylene group or the arylene group.

[0018] Examples of the alkylene group include a methylene group, an ethylene group, a propylene group, etc. Examples of the arylene group include a phenylene group, a naphthalenylene group, etc. The fluorinated alkylene group is a group in which some or all of the hydrogen atoms of the alkylene group are fluorinated. Preferably, the alkylene group is -(CF2). m - (wherein m is an integer of 1 to 15 (preferably 1 to 6)).

[0019] In one embodiment, the compound having the structure represented by formula (1) is represented by the following formula (3): [ka] (In the formula, R 1 ~R 6 , R a ~R c is the same as equation (1). A 2 is a linking group. Three R 1 ~R 6 and R a ~R cmay be the same or different.)

[0020] Examples of the linking group include groups capable of linking three structures represented by formula (1), such as boron (B), ≡CH, a cycloalkane ring, an aromatic ring, a heterocycle, and an aromatic heterocycle.

[0021] The compound of this embodiment is preferably a compound represented by the following formula (2A). [ka] (In the formula, R 1 ~R 6 , R 11 ~R 16 are each hydrogen, a substituent or a leaving group, R 1 ~R 6 are leaving groups, and R 11 ~R 16 At least two of A are leaving groups. 1 is a single bond or a linking group.

[0022] Moreover, a compound represented by the following formula (2B) is preferred. [ka] (In the formula, R 1 , R 6 , R 11 and R 16 are leaving groups. A 1 is the same as equation (2). In formula (2B), the hydrogen attached to the cyclohexene ring is omitted. Specific examples of the compound of this embodiment are shown below.

[0023] [ka] (In the formula, m is an integer of 1 to 15 (preferably 1 to 6).)

[0024] The compound of this embodiment can be synthesized, for example, by referring to the examples described below.

[0025] [Composition] The composition according to this embodiment contains the above-mentioned crosslinking agent (compound), fluoroelastomer, and crosslinking initiator.

[0026] The crosslinking agent is preferably added in an amount of 0.5 to 50 mmol, more preferably 0.5 to 40 mmol, more preferably 1 to 30 mmol, more preferably 1 to 25 mmol, and even more preferably 2.0 to 20 mmol, per 100 g of fluoroelastomer. The more the amount added, the more the steam resistance and heat resistance tend to be improved. However, if the amount is too large, the composition may become hard.

[0027] The fluoroelastomer may be a perfluoroelastomer or a partially fluorinated elastomer. For example, repeating units derived from the following monomers can be exemplified. The repeating units may include repeating units derived from one or more monomers. CF2=CH2 (vinylidene fluoride), CF2=CF2 (tetrafluoroethylene), CF2=CFCF3 (hexafluoropropylene), CH2=CH2, CH2=CHCH3

[0028] The fluoroelastomer used in the present embodiment preferably contains iodine and / or bromine, more preferably iodine, as a radical attack site during crosslinking (curing). Perfluoroelastomers that can be cured with peroxides are described in, for example, JP 2006-9010 A.

[0029] (Per)fluoroelastomers generally contain from 0.001% to 5% by weight of iodine relative to the total polymer weight, preferably from 0.01% to 2.5% by weight. The iodine atoms may be present along the chain and / or in terminal positions.

[0030] The (per)fluoroelastomers are prepared from copolymers such as (per)fluorinated olefins having one unsaturation of ethylene type, preferably in a terminal position. Examples of the comonomer include the following. CF2=CFOR 2f (Per)fluoroalkyl vinyl ethers (PAVE) (In the formula, R 2f is (per)fluoroalkyl having 1 to 6 carbon atoms, for example, trifluoromethyl or pentafluoropropyl. CF2=CFOX o (Per)fluorooxyalkyl vinyl ethers (In the formula, X o is (per)fluorooxyalkyl having 1 to 12 carbon atoms containing one or more ether groups, for example, perfluoro-2-propoxypropyl. CFX2=CX2OCF2OR'' f (IB) (In the formula, R'' f is a linear or branched (per)fluoroalkyl having 2 to 6 carbon atoms, a cyclic (per)fluoroalkyl having 5 or 6 carbon atoms, or a linear or branched (per)fluorooxyalkyl having 2 to 6 carbon atoms and containing 1 to 3 oxygen atoms, and X2 is F or H.

[0031] The (per)fluorovinyl ethers of formula (IB) are preferably represented by the following formula: CFX2=CX2OCF2OCF2CF2Y (II-B) (wherein Y is F or OCF3, and X2 is as defined above.)

[0032] Perfluorovinyl ethers of the following formula are more preferred. CF2=CFOCF2OCF2CF3(MOVE1) CF2=CFOCF2OCF2CF2OCF3(MOVE2)

[0033] As preferred monomer compositions, the following can be exemplified. Tetrafluoroethylene (TFE) 50-85 mol %, PAVE 15-50 mol %; TFE 50-85 mol %, MOVE 15-50 mol %.

[0034] The fluoroelastomer may also contain units derived from vinylidene fluoride, fluoroolefins having 3 to 8 carbon atoms which may contain chlorine and / or bromine, and non-fluorinated olefins having 3 to 8 carbon atoms.

[0035] The crosslinking initiator may be any commonly used one, such as a peroxide or an azo compound.

[0036] The crosslinking initiator is preferably added in an amount of 0.3 to 35 mmol, more preferably 1 to 15 mmol, and further preferably 1.5 to 10 mmol, per 100 g of fluoroelastomer. The more the amount added, the more the steam resistance and heat resistance tend to improve. However, if the amount is too much, scorching or foaming may occur.

[0037] In one embodiment, the composition may include a crosslinking aid. Examples of the crosslinking auxiliary include zinc oxide, activated alumina, magnesium oxide, quaternary ammonium salts, quaternary phosphonium salts, and amines. By including the crosslinking auxiliary, crosslinking efficiency and heat resistance can be improved. The crosslinking auxiliary is usually added in an amount of 0.1 to 10 g per 100 g of fluoroelastomer.

[0038] In one embodiment, the composition may include an aromatization promoter. The aromatization promoter includes an acid and a base. The acid may be either an organic acid or an inorganic acid. Preferred organic acids include carboxylic acids and sulfonic acids. Preferred inorganic acids include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, boric acid, chromic acid, oxoacids, hydrogen halides, and thionyl chloride. Examples of the base include hydroxides, primary to tertiary amines, and oxides. Either the acid or the base or both of them may be reacted in advance to form a salt and then added. The aromatization accelerator is usually added in an amount of 0.1 to 10 g per 100 g of the fluoroelastomer.

[0039] In addition, a filler can be blended in the composition to increase the mechanical strength. As long as the effect of the present invention is not impaired, any filler generally known as a filler for elastomers can be used. Examples of the filler include carbon black, silica, barium sulfate, titanium dioxide, semicrystalline fluoropolymer, and perfluoropolymer.

[0040] If necessary, it is also possible to add appropriate amounts of thickeners, pigments, coupling agents, antioxidants, stabilizers, etc.

[0041] [Crosslinked fluoroelastomers and molded articles] The crosslinked fluoroelastomer according to the present embodiment can be obtained by crosslinking the above-mentioned composition. For example, it can be produced by a process including the following steps 1 and 2. Step 1: Heating the composition to react the fluoroelastomer with the crosslinking agent. Step 2: A step of converting the cyclohexane ring derived from the crosslinking agent into an aromatic ring

[0042] The heating conditions in the above step 1 can be appropriately set according to the crosslinking agent used, etc. In general, the heating temperature is 100 to 200° C., and the heating time is 5 to 60 minutes. In this step, the fluoroelastomer reacts with the crosslinking agent and bonds with it, and as a result, the cyclohexene rings of the crosslinking agent become cyclohexane rings. Step 1 may be carried out, for example, by placing the composition in a mold and pressing it.

[0043] In step 2, the cyclohexane ring formed in step 1 is converted to an aromatic ring. The heating conditions can be appropriately adjusted depending on whether an aromatization promoter is used or not. For example, heating is performed at 100 to 350° C. for 1 to 100 hours. This heating can be performed using an electric furnace or the like.

[0044] As an example of the production method, a method including the above steps 1 and 2 has been described, but the present invention is not limited to this. For example, by optimizing heating conditions, etc., the above steps 1 and 2 may be performed together.

[0045] The heating may be carried out in an inert gas atmosphere or in air. As the inert gas, nitrogen, helium, argon, etc. can be used, and nitrogen is preferable. In the inert gas atmosphere, the oxygen concentration is preferably 10 ppm or less, more preferably 5 ppm or less.

[0046] The crosslinked fluoroelastomer according to this embodiment preferably does not contain any unsaturated bonds other than those in aromatic rings. Moreover, the crosslinked fluoroelastomer according to the present embodiment preferably has a gel fraction of 35% or more, more preferably 45% or more, after 24 hours of exposure to saturated steam at 330° C. The gel fraction can be calculated from the following formula by measuring the mass (A) of the crosslinked fluoroelastomer before exposure to the saturated steam, immersing the crosslinked fluoroelastomer after 24 hours of exposure to the saturated steam in a solvent (e.g., Fluorinert FC-3283 (3M)) and measuring the mass (B) of the remaining solid content. Gel fraction = mass(B) / mass(A)×100

[0047] The crosslinked fluoroelastomer obtained by the above-mentioned method can be used as a sealing material, and can be used in the form of a molded article such as an O-ring, a gasket, or a seal ring. EXAMPLES

[0048] Steam resistance calculation results for bridge structure model The activation energy required for the water molecules to react was calculated by molecular orbital calculation. The results are shown in Table 1. The calculation was performed using Gaussian 09W (Rev. C.01) with the basis set of B3LYP / 6-31+G*. The larger the activation energy, the less likely the reaction with steam will occur, and the higher the resistance of the crosslinked structure to high-temperature steam. The crosslinked structure (i) that can be derived from the crosslinking agent of the present invention does not contain unsaturated bonds other than aromatic rings, so it has a large activation energy and is excellent in steam resistance. On the other hand, the crosslinked structures (ii) and (iii) derived from conventional crosslinking agents contain unsaturated bonds such as vinyl groups that are vulnerable to steam, so they have a small activation energy and are poor in steam resistance. [Table 1]

[0049] Example 1 [Synthesis of compound 1] The following compound 1 was synthesized. The compound and catalyst used were both commercially available reagents. [ka]

[0050] (1) Synthesis of intermediate 1 In a 200 mL two-necked flask equipped with a stirrer, magnesium turnings (1.10 g, 45.3 mmol) and diethyl ether (20 mL) were charged under a nitrogen atmosphere. 4-Bromo-1-butene (5.43 g, 40.2 mmol) dissolved in diethyl ether (20 mL) was slowly added dropwise to the flask while stirring at room temperature. The mixture was then stirred at room temperature for an additional 30 minutes. The obtained solution (34 mL, 20.4 mmol) was placed in another 100 mL two-neck flask under a nitrogen atmosphere, and dodecafluorosuberic acid (1.57 g, 4.0 mmol) dissolved in diethyl ether (4 mL) was slowly added dropwise to the mixture while stirring at room temperature. After the dropwise addition, the mixture was stirred at 45°C for 1.25 hours, and then stirred for 15 hours after returning to room temperature. After slowly adding 50% hydrochloric acid containing ice, the organic layer was extracted with diethyl ether (15 mL x 3 times). The organic layer was washed with a saturated solution of sodium bicarbonate (20 mL x 3 times) and water (20 mL x 3 times), dried over anhydrous sodium sulfate, and the filtrate was concentrated under reduced pressure. The obtained concentrate was purified by silica gel chromatography to obtain 1.19 g of the following intermediate 1, which is a diketone compound.

[0051] [ka]

[0052] (2) Synthesis of intermediate 2 In a 50 mL two-neck flask equipped with a stirrer, magnesium turnings (0.53 g, 21.9 mmol) and diethyl ether (10 mL) were charged under a nitrogen atmosphere, and allyl bromide (2.43 g, 20.1 mmol) dissolved in diethyl ether (10 mL) was slowly added dropwise to the mixture while stirring at room temperature. The mixture was then stirred at room temperature for an additional 30 minutes. The obtained solution (11 mL, 6.3 mmol) was placed in another 30 mL two-neck flask under a nitrogen atmosphere and cooled to -78°C. Intermediate 1 (1.19 g) dissolved in diethyl ether (2 mL) was slowly added dropwise to the flask while stirring at -78°C. After stirring for 1 hour, the mixture was returned to room temperature and the reaction solution was added to 10% hydrochloric acid, after which the organic layer was extracted with diethyl ether (15 mL x 3 times). The organic layer was dried over anhydrous sodium sulfate, and the filtrate was concentrated under reduced pressure. The obtained concentrate was purified by silica gel chromatography to obtain 1.13 g of the following intermediate 2, which is a diol compound.

[0053] [ka]

[0054] (3) Synthesis of intermediate 3 In a 100 mL two-neck flask equipped with a stirrer, intermediate 2 (1.13 g, 2.05 mmol), dichloromethane (41 mL), and first-generation Grubbs catalyst (0.086 g, 0.105 mmol) were charged under a nitrogen atmosphere and stirred at 50° C. for 21 hours. After returning to room temperature, the reaction solution was purified by silica gel chromatography to obtain 0.853 g of intermediate 3 below.

[0055] [ka]

[0056] Regarding the obtained compound, 1 H-NMR and 19 The structure was analyzed by F-NMR (AVANCE II 400, manufactured by BRUKER). The results are shown below. · 1 H-NMR (CDCl3,400MHz): δ=1.79(td,J=25.30Hz,6.07Hz,2H),1.90~2.08(m,2H),1.97(s ,2H),2.09~2.37(m,6H),2.57(d,J=17.41Hz,2H),5.53~5.67(m,2H),5.73~5.86(m,2H) · 19 F-NMR(CDCl3,CFCl3,376MHz):δ=-119.60(d,J=8.70Hz,4F),-121.09~-125.29(m,4F),-121.82~-122.30(m,4F)

[0057] (4) Synthesis of Compound 1 In a 30 mL two-neck flask equipped with a stirrer, compound 1 (0.148 g, 0.3 mmol), N-bromosuccinimide (0.112 g, 0.63 mmol), azobisisobutyronitrile (AIBN: 0.0014 g, 0.009 mmol), and carbon tetrachloride (3 mL) were charged under an argon atmosphere and stirred at 80° C. for 2 hours. After returning to room temperature, the mixture was concentrated under reduced pressure, and the resulting concentrate was purified by silica gel column chromatography to obtain compound 1. 1 H-NMR, 19 The synthesis of compound 1 was confirmed by F-NMR and mass spectrometry (MS). The same applies to the following compounds.

[0058] Example 2 [Synthesis of compound 2] The following compound 2 was synthesized. [ka] (In the formula, Me is a methyl group.)

[0059] In a 500mL two-necked flask equipped with a stirrer, 1,4-cyclohexadiene (8.01g, 100.0mmol) and dichloromethane (250mL) were charged under a nitrogen atmosphere, and while stirring at 0°C, metachloroperbenzoic acid (23% water content, 23.55g, 105.1mmol) was slowly added and stirred at room temperature for 48 hours. After stirring, sodium carbonate solution (2.5M, 100mL) was added at 0°C and stirred for 15 minutes. Next, after raising the temperature to room temperature, the organic layer was washed with saturated sodium bicarbonate solution (200mL) and 20% saline (100mL x 3 times), dried over anhydrous sodium sulfate, and the filtrate was concentrated under reduced pressure to obtain 6.62g of 1,2-epoxy-4-cyclohexene as a colorless transparent liquid.

[0060] Next, the above 1,2-epoxy-4-cyclohexene (8.63 g, 89.8 mmol), methanol (180 mL), and 2,3-dichloro-5,6-dicyano-p-benzoquinone (0.509 g, 2.2 mmol) were charged in a 500 mL two-neck flask equipped with a stirrer under a nitrogen atmosphere and stirred at room temperature for 17 hours. After stirring, the mixture was concentrated under reduced pressure, and the resulting concentrate was purified by silica gel chromatography to obtain 8.43 g of 1-hydroxy-2-methoxy-4-cyclohexene as a pale yellow oil.

[0061] Next, in a 500 mL two-necked flask equipped with a stirrer, the above-mentioned 1-hydroxy-2-methoxy-4-cyclohexene (2.95 g, 22.9 mmol), acetonitrile (115 mL), potassium peroxymonosulfate (12.69 g, 20.6 mmol), and sodium 2-iodo-5-nitro-benzenesulfonate (0.804 g, 2.29 mmol) were charged under a nitrogen atmosphere and stirred at 70 ° C for 14 hours. The mixture was returned to room temperature, and the salt was removed using a silica gel short column (diethyl ether), followed by concentration under reduced pressure. The concentrate was purified by silica gel chromatography to obtain 0.913 g of 2-methoxy-4-cyclohexen-1-one as a pale yellow oil.

[0062] In a 30 mL two-neck flask equipped with a stirrer, 1,6-diiodododecafluorohexane (0.111 g, 0.2 mmol) and diethyl ether (2.5 mL) were charged under an argon atmosphere, and ethyl magnesium bromide (3.0 M: diethyl ether solvent, 0.146 mL, 0.44 mmol) was added dropwise while stirring at -78 ° C., and the mixture was stirred at -78 ° C. for 1.5 hours. Then, 2-methoxy-4-cyclohexen-1-one (0.0555 g, 0.44 mmol) dissolved in diethyl ether (1.0 mL) was added dropwise, and the mixture was stirred for 18 hours. After adding a saturated aqueous ammonium chloride solution, the mixture was returned to room temperature, and organic matter was extracted from the aqueous layer using diethyl ether, and the organic layer was dried over anhydrous sodium sulfate. Anhydrous sodium sulfate was removed by filtration, and the mixture was concentrated under reduced pressure. The resulting concentrate was purified by silica gel chromatography to obtain compound 2.

[0063] Example 3 [Synthesis of compound 3] The following compound 3 was synthesized. [ka]

[0064] Compound 3 was synthesized from compound 2 by the following procedure. Sodium hydride (0.072 g, 3 mmol) and tetrahydrofuran (7 mL) were charged in a 30 mL two-necked flask equipped with a stirrer under an argon atmosphere, and while stirring at 0 ° C, compound 2 (0.277 g, 0.5 mmol) was dissolved in tetrahydrofuran (2 mL) and dropped, and stirred at 0 ° C for 30 minutes. Iodomethane (0.426 g, 3 mmol) was dissolved in tetrahydrofuran (1 mL) and dropped, then the temperature was raised to room temperature and stirred for 21 hours. The reaction solution was diluted with hexane, a saturated aqueous ammonium chloride solution was added, and the organic matter was extracted from the water tank using hexane, and the organic layer was dried with anhydrous sodium sulfate. After removing the anhydrous sodium sulfate by filtration, the mixture was concentrated under reduced pressure, and the resulting concentrate was purified by silica gel chromatography to obtain compound 3.

[0065] Example 4 [Synthesis of compound 4] The following compound 4 was synthesized. [ka]

[0066] In a 30 mL two-necked flask equipped with a stirrer, the above compound 2 (0.291 g, 0.5 mmol) and methylene chloride (5 mL) were charged under an argon atmosphere, and boron tribromide (1 M: methylene chloride solvent, 5 mL, 5 mmol) was added and stirred at room temperature for 3 hours. Ammonia water was added at 0°C and stirred for 30 minutes. Organic matter was extracted from the aqueous layer using methylene chloride, and the organic layer was washed with saturated saline and then dried over anhydrous sodium sulfate. Anhydrous sodium sulfate was removed by filtration, and the mixture was concentrated under reduced pressure. The resulting concentrate was purified by silica gel chromatography to obtain compound 4.

[0067] Experimental Example It was confirmed by the following experiment that the structure represented by the formula (1) of the present invention forms a desired crosslinked structure. As a crosslinking agent, the following compound 2A having the structure of the above compound 2 was used. In addition, since fluoroalkyl iodide (-CF2CF2I) is introduced into the crosslinking reaction site of the fluoroelastomer, tridecafluoroiodide was used instead of perfluoroelastomer in the experiment. The two were reacted in the presence of a radical initiator to synthesize the following compound 2B in which the cyclohexene ring of compound 2A was converted to a cyclohexane ring. Then, the following compounds 2C and 2C' were synthesized in which the cyclohexane ring of compound 2B was converted to an aromatic ring by heating. This confirmed that the crosslinking agent of the present application crosslinks with the fluoroelastomer, and then aromaticized by heating. Compound 2A can be synthesized by using tridecafluoroiodide instead of 1,6-diiodododecafluorohexane in Example 2.

[0068] [ka]

[0069] Compound 1 (0.444 g, 1.0 mmol), ethylene dichloride (3.3 mL), and tridecafluorohexyl iodide (1.326 g, 3.0 mmol) were charged in a 20 mL two-neck flask equipped with a stirrer under an argon atmosphere, and benzoyl peroxide (0.102 g, 0.30 mmol) was added and stirred at 90° C. for 24 hours. The temperature was returned to room temperature, and the obtained concentrate was purified by silica gel chromatography to obtain compound 2B. Compound 2B (0.089 g, 0.10 mmol) and pyridine (1.0 mL) were charged in a 20 mL two-necked flask equipped with a stirrer under an argon atmosphere, and thionyl chloride (0.026 g, 0.22 mmol) was slowly added, followed by stirring at room temperature for 18 hours. The mixture was diluted with ether, and the organic layer was washed with dilute hydrochloric acid, aqueous sodium bicarbonate, and pure water, in that order, and then dried over anhydrous sodium sulfate. The anhydrous sodium sulfate was removed by filtration, and the mixture was concentrated under reduced pressure. The resulting concentrate was purified by silica gel chromatography to obtain compounds 2C and 2C'.

[0070] [Structural analysis of compound 2B] · 1 H-NMR(CDCl3,400MHz):δ=1.70~3.59(m,9H),3.59~4.09(m,1H),4.21~4.82(m,1H) · 19 F-NMR(CDCl3,CFCl3,376MHz):δ=81.12~81.35(m,6F),106.10~124.41(m,16F),125.32~128.00(m,4F)

[0071] [Structural analysis of compound 2C] · 1 H-NMR(CDCl3,400MHz):δ=7.76(s,4H) · 19 F-NMR(CDCl3,CFCl3,376MHz):δ=-81.26(t,J=19.50Hz,3F),-111.77(t,J=28.46Hz,2F),-121.7 1~-122.08(m,2F),-122.12~-122.33(m,2F),-123.18~-123.46(m,2F),-126.52~-126.74(m,2F)

[0072] [Structural analysis of compound 2C'] · 1 H-NMR(CDCl3,400MHz):δ=7.70(t,J=7.76Hz,1H),7.82(s,2H),7.84(s,1H) · 19F-NMR(CDCl3,CFCl3,376MHz):δ=-81.49(t,J=19.69Hz,3F),-111.78(t,J=28.73Hz,2F),-121.8 1~-122.18(m,2F),-122.37~-122.68(m,2F),-123.23~-123.59(m,2F),-126.67~-126.92(m,2F)

[0073] Example 5 and Comparative Examples 1 and 2 [Synthesis of compound 5] The following compound 5 was synthesized. [ka]

[0074] In a 30 mL two-necked flask equipped with a stirrer, the above compound 4 (0.080 g, 0.15 mmol), methylene chloride (15 mL), triethylamine (0.090 g, 0.9 mmol), and 4-dimethylaminopyridine (2 mg, 0.015 mmol) were charged under an argon atmosphere and cooled to 0°C. Trifluoromethanesulfonyl chloride (0.103 g, 0.9 mmol) was added dropwise thereto and stirred at 40°C for 20 hours. The reaction vessel was returned to room temperature and the reaction was stopped with ammonia water. Organic matter was extracted from the aqueous layer using methylene chloride, the organic layer was washed with saturated saline, and then dried over anhydrous sodium sulfate. Anhydrous sodium sulfate was removed by filtration, and the mixture was concentrated under reduced pressure. The resulting concentrate was purified by silica gel chromatography to obtain compound 5. [Sample preparation method] Each sample was prepared as shown in Table 2 below. The components in the amounts shown in Table 2 were placed in a pressure vessel and purged with Ar. The vessel was left to stand until the perfluoroelastomer (PFE40z manufactured by 3M) was dissolved. The vessel was heated at 100°C for 30 min to crosslink the FFKM. The vessel was heated in a vacuum oven at 130°C for 2 hr to volatilize the solvent. The vessel was heated in a nitrogen-purged oven at 310°C for 4 hr. [Table 2]

[0075] [Steam resistance evaluation] The weight (A) of the sample (crosslinked molded product) prepared by the above method was measured and exposed to saturated water vapor at 330°C for 24 hours. After exposure to steam, the sample was immersed in Fluorinert FC-3283 at room temperature for 72 hours. After immersion, the sample remaining as a solid was removed and heated in a vacuum oven at 130°C for 2 hours to volatilize the solvent. The weight (B) after drying was measured and the gel fraction was calculated using the following formula. The results are shown in Table 3. Gel fraction = mass(B) / mass(A)×100 [Table 3] [Industrial Applicability]

[0076] The compound of the present invention can be used as a crosslinking agent for fluoroelastomers. The crosslinked fluoroelastomers of the present invention can be used as sealing materials (O-rings, etc.) that require chemical resistance and high-temperature steam resistance in power generation, semiconductor devices, chemical plants, etc.

Claims

1. A crosslinked fluoroelastomer containing no unsaturated bonds other than aromatic rings in the crosslinked structure, wherein the linking group linking the aromatic rings is a perfluoroalkylene; The crosslinked structure is represented by the following formula: (wherein m is an integer from 1 to 15). A crosslinked fluoroelastomer having a gel fraction of 45% or more after exposure to saturated water vapor at 330° C. for 24 hours.

2. A molding obtainable from the crosslinked fluoroelastomer according to claim 1.

3. The molded article according to claim 2, which is a sealing material.

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