Crosslinkable composition, member and use of crosslinkable composition

Abstract

To provide a cross-linkable composition capable of providing a member excellent in resistance to nitric acid for an air control system of an ammonia combustion engine.SOLUTION: A cross-linkable composition to be used for a member of an air control system of an ammonia combustion engine contains fluororubber and a cross-linking agent. The composition further contains hydrotalcite as an acid acceptor or contains or does not contain an acid acceptor other than hydrotalcite. The content of the acid acceptor other than hydrotalcite is 0 pt.mass or more and less than 1 pt.mass relative to 100 pts.mass of the fluororubber.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to crosslinkable compositions for use in components of air management systems of ammonia-burning engines, components of air management systems of ammonia-burning engines, and uses of the crosslinkable compositions. [Background technology]

[0002] Patent Document 1 describes a curable fluoroelastomer composition comprising: A) a curable fluoroelastomer; B) a curing agent; and C) an acid acceptor selected from the group consisting of hydrous bismuth nitrate compounds and bismuth oxide. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2013-534271 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present disclosure is to provide a crosslinkable composition capable of providing a component of an air management system for an ammonia combustion engine, the component having excellent resistance to nitric acid. [Means for solving the problem]

[0005] According to the present disclosure, there is provided a crosslinkable composition for use in a component of an air management system for an ammonia combustion engine, the composition comprising a fluororubber and a crosslinking agent, the composition further comprising: (a) containing hydrotalcite as an acid acceptor, or (b) A crosslinkable composition is provided which contains, or does not contain, an acid acceptor other than hydrotalcite as an acid acceptor, and the content of the acid acceptor other than hydrotalcite is 0 part by mass or more and less than 1 part by mass per 100 parts by mass of the fluororubber.

[0006] In the case of (a), the content of the hydrotalcite is preferably 0.1 to 10 parts by mass based on 100 parts by mass of the fluororubber. In the case of (a), the content of the acid acceptor other than hydrotalcite is preferably 0 part by mass or more and less than 1 part by mass per 100 parts by mass of the fluororubber. In the case of (b), the content of the hydrotalcite is preferably less than 0.1 part by mass based on 100 parts by mass of the fluororubber. In the case of (b), the acid acceptor other than hydrotalcite is preferably at least one selected from the group consisting of metal oxides, metal hydroxides, alkali metal silicates, and metal salts of weak acids. The fluororubber is preferably a peroxide crosslinkable fluororubber. The fluororubber is preferably at least one selected from the group consisting of vinylidene fluoride-based fluororubbers, tetrafluoroethylene / propylene-based fluororubbers, and perfluororubbers. The fluororubber comprises a vinylidene fluoride unit and a fluorocarbon polymer having the following general formula (1): CHX 1 =CX 2 Rf (1) (In the formula, X 1 and X 2 one of which is H and the other is F, and Rf is a linear or branched fluoroalkyl group having 1 to 12 carbon atoms.) and tetrafluoroethylene / propylene fluororubbers are preferably at least one selected from the group consisting of fluororubbers (1) containing a fluorine-containing monomer (1) unit represented by the following formula (1): The fluorine-containing monomer (1) is preferably 2,3,3,3-tetrafluoropropene. It is preferable that the fluororubber (1) has at least one of iodine atoms and bromine atoms, and the total content of iodine atoms and bromine atoms is 0.001 to 10 mass %. The crosslinking agent is preferably a peroxide. It is preferable that the composition further contains a co-crosslinking agent.

[0007] The present disclosure also provides a component for an air management system of an ammonia combustion engine, the component comprising a cross-linked fluororubber product obtained by cross-linking the above-mentioned cross-linkable composition.

[0008] The present disclosure also provides the use of the above crosslinkable composition to form a component of an air management system of an ammonia-burning engine. Effect of the Invention

[0009] According to the present disclosure, it is possible to provide a crosslinkable composition that can provide a component for an air management system of an ammonia combustion engine, the component having excellent resistance to nitric acid. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Specific embodiments of the present disclosure will be described in detail below, but the present disclosure is not limited to the following embodiments.

[0011] Ammonia is expected to be an alternative fuel for combustion engines because it does not produce carbon dioxide when burned. When ammonia is burned in a combustion engine, the exhaust gas emitted from the combustion engine usually contains a higher concentration of nitrogen oxides than that of a combustion engine that uses only conventional fossil fuels, and nitrogen oxides are easily converted to nitric acid by moisture. The nitric acid thus generated poses the problem of swelling rubber components used in the air management systems of combustion engines.

[0012] Patent Document 1 describes that fluororubber articles obtained from the curable fluoroelastomer composition having the above-mentioned composition surprisingly exhibit low volume swelling, i.e., less than 10% by volume, preferably less than 5% by volume, when exposed to dilute acid, coolant fluid or biofuel for a long period of time and / or at high temperature.

[0013] However, conventional components of the air management system of a combustion engine using a biofuel do not have sufficient resistance to swelling in high concentrations of nitric acid. Therefore, a crosslinkable composition is required that has sufficient resistance to swelling in high concentrations of nitric acid and provides a component that will not swell or be damaged when used as a component of the air management system of an ammonia combustion engine.

[0014] It has now been found that by appropriately selecting the type of acid acceptor used in the crosslinkable composition, the content of the acid acceptor, etc., the swelling resistance of the resulting crosslinked product to nitric acid is significantly improved, and the crosslinked product exhibits excellent swelling resistance even when contacted with high-concentration nitric acid generated from an ammonia combustion engine. According to the newly discovered findings, a crosslinked product obtained from a crosslinkable composition in which the type of acid acceptor, the content of the acid acceptor, etc. are appropriately selected does not swell significantly and maintains its original shape, for example, even when immersed for a long period of time in a high-concentration aqueous nitric acid solution of 5 mass% or more at a temperature of 80°C or more.

[0015] In other words, the crosslinkable composition of the present disclosure is a composition used for forming a component of an air management system of an ammonia combustion engine, and by appropriately selecting the type of acid acceptor, the content of the acid acceptor, and the like, it is possible to give a crosslinked product having significantly improved swelling resistance to nitric acid generated from an ammonia combustion engine.

[0016] The ammonia combustion engine means an engine that converts heat generated by burning ammonia into mechanical energy, and may be an internal combustion engine or an external combustion engine as long as it uses ammonia as fuel. The ammonia combustion engine may be a combustion engine that burns only ammonia as fuel, or may be a combustion engine that burns a mixture of ammonia and other compounds such as methane or coal. The ammonia combustion engine is used, for example, in automobiles, ships, generators, etc. The ammonia combustion engine may be a small diesel combustion engine used in automobiles and ships. The concentration of ammonia in the fuel is 1 to 100% by volume.

[0017] An air management system is a system through which gas circulates. Examples of such systems include air filters, turbochargers, intercoolers, intake manifolds, and exhaust gas recirculation coolers that are attached to general engines (such as automobiles, ships, and construction machinery).

[0018] The members of the air management system are members constituting the air management system, and include members directly connected to the air management system. Examples include air ducts, turbocharger hoses, EGR (exhaust gas recirculation) hoses and seals, intercooler hoses and seals, intake manifold seals, oxygen sensor hoses and seals, other sensor hoses and seals, etc. The environmental temperature in which the members of the air management system are used is not particularly limited, but is preferably 0 to 200°C, more preferably 0 to 150°C.

[0019] The gas circulating inside the air management system contains nitrogen oxides contained in the combustion gas of ammonia, nitric acid generated from the nitrogen oxides, etc. The fluororubber cross-linked product obtained from the cross-linkable composition of the present disclosure has excellent swelling resistance to nitric acid, and therefore is less likely to swell even when in contact with combustion gas containing nitric acid. Therefore, the cross-linkable composition of the present disclosure can be suitably used in particular for members that come into contact with exhaust gas discharged from an ammonia combustion engine. Examples of members that come into contact with exhaust gas include members that are commonly used in the exhaust system of a combustion engine, such as hoses and seal materials.

[0020] The crosslinkable composition of the present disclosure contains a fluororubber and a crosslinking agent.

[0021] Furthermore, the first crosslinkable composition of the present disclosure contains hydrotalcite as an acid acceptor. By containing hydrotalcite in the crosslinkable composition, the swelling resistance of the crosslinked product obtained from the crosslinkable composition to high-concentration nitric acid is significantly improved compared to the case of using other acid acceptors, and the crosslinked product has excellent ammonia resistance and urea resistance, so that the first crosslinkable composition of the present disclosure can be suitably used as a material for forming a member of an air management system of an ammonia combustion engine. Urea resistance is a property required for a member when a urea catalyst is used in a urea SCR system or the like.

[0022] In the first crosslinkable composition of the present disclosure, the content of the hydrotalcite is preferably 0.1 to 10 parts by mass, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, more preferably 8 parts by mass or less, and even more preferably 6 parts by mass or less, relative to 100 parts by mass of the fluororubber, in order to provide the member with excellent ammonia resistance and urea resistance.

[0023] The first crosslinkable composition of the present disclosure may or may not contain an acid acceptor other than hydrotalcite. The content of the acid acceptor other than hydrotalcite is preferably 0 to 1 part by mass, more preferably 0 part by mass or more and less than 1 part by mass, even more preferably 0 to 0.5 parts by mass or less, still more preferably 0 to 0.1 parts by mass, and particularly preferably 0 part by mass, relative to 100 parts by mass of the fluororubber, since the nitric acid resistance of the member is further improved.

[0024] In addition, the second crosslinkable composition of the present disclosure may contain an acid acceptor other than hydrotalcite, or may not contain an acid acceptor other than hydrotalcite, and when an acid acceptor other than hydrotalcite is contained, the content is less than 1 part by mass per 100 parts by mass of the fluororubber. By reducing the content of the acid acceptor other than hydrotalcite in the crosslinkable composition, the swelling resistance of the crosslinked product obtained from the crosslinkable composition to high-concentration nitric acid is significantly improved, and therefore the second crosslinkable composition of the present disclosure can be suitably used as a material for forming a member of an air management system for an ammonia combustion engine.

[0025] In the second crosslinkable composition of the present disclosure, the content of the acid acceptor other than hydrotalcite is, since the nitric acid resistance of the member is further improved, 0 part by mass or more and less than 1 part by mass, more preferably 0 to 0.5 parts by mass or less, even more preferably 0 to 0.1 parts by mass, and particularly preferably 0 part by mass, relative to 100 parts by mass of the fluororubber.

[0026] The second crosslinkable composition of the present disclosure preferably does not substantially contain hydrotalcite. The content of hydrotalcite in the second crosslinkable composition of the present disclosure is preferably 0 part by mass or more and less than 1 part by mass, more preferably 0 to 0.5 parts by mass or less, even more preferably 0 to 0.1 parts by mass, still more preferably less than 0.1 parts by mass, and particularly preferably 0 part by mass, relative to 100 parts by mass of fluororubber.

[0027] The hydrotalcite used in the present disclosure is not particularly limited, but may be represented by the general formula: [(M1 2+ ) 1-x M 3+ x (OH)2] x+ [A n- x / n mH2O] x- (In the formula, M1 2+ is a divalent metal ion, M 3+ is a trivalent metal ion, and A n-is an n-valent anion, x is a number satisfying 0 < x < 0.5, and m is a number satisfying 0 ≦ m. A compound represented by ) is more preferable in terms of easy availability. The hydrotalcites may be natural or synthetic.

[0028] M1 2+ represents a divalent metal ion, for example, Mg 2+ , Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ or Zn 2+ can be mentioned. Among these, Mg 2+ and / or Zn 2+ are preferable in terms of easy availability.

[0029] M 3+ represents a trivalent metal ion, for example, Al 3+ , Fe 3+ , Cr 3+ , Co 3+ or In 3+ can be mentioned. Among these, Al 3+ is preferable in terms of easy availability.

[0030] A n- represents an n-valent anion, for example, OH - , F - , Cl - , Br - , NO3 - , CO3 2- , SO4 2- , Fe(CN)6 3- , CH3COO - , oxalate ion or salicylate ion can be mentioned. Among these, CO3 2- is preferable in terms of easy availability.

[0031] In the above formula, M1 2+ is Mg 2+ and / or Zn 2+ and M 3+ is Al3+ and A n- is particularly preferably CO3 2- is particularly preferred.

[0032] x is a number satisfying 0 < x < 0.5, preferably a number satisfying 0.2 ≤ x ≤ 0.4, and more preferably a number satisfying 0.2 ≤ x ≤ 0.33. If x is within this range, the formation of hydrotalcite is stable.

[0033] m is a number satisfying 0 ≤ m, preferably a number satisfying 0 ≤ m ≤ 1.

[0034] Hydrotalcite is a non-stoichiometric compound represented by the above formula. Among these, from the viewpoint of easy availability, Mg6Al2(OH) 16 CO3·4H2O, Mg 4.5 Al2(OH) 13 CO3·mH2O (0 ≤ m), Mg4Al2(OH) 12 CO3·3.5H2O, Mg 4.3 Al2(OH) 12.6 CO3·mH2O (0 ≤ m), Mg5Al2(OH) 14 CO3·4H2O, Mg3Al2(OH) 10 CO3·1.7H2O, and Mg3ZnAl2(OH) 12 CO3·mH2O (0 ≤ m) selected from the group consisting of at least one compound is preferred, and Mg6Al2(OH) 16 CO3·4H2O, Mg 4.5 Al2(OH) 13 CO3·3.5H2O, Mg 4.3 Al2(OH) 12.6 CO3·mH2O (0 ≤ m), and Mg3ZnAl2(OH) 12 CO3·mH2O (0 < m) selected from the group consisting of at least one compound is more preferred.

[0035] The first crosslinkable composition of the present disclosure and the second crosslinkable composition of the present disclosure may or may not contain an acid acceptor other than hydrotalcite. Examples of acid acceptors other than hydrotalcite include metal oxides such as magnesium oxide, calcium oxide, bismuth oxide, and zinc oxide, metal hydroxides such as calcium hydroxide, alkali metal silicates such as sodium metasilicate described in JP-T-2011-522921, and metal salts of weak acids described in JP-A-2003-277563. Examples of metal salts of weak acids include carbonates, benzoates, oxalates, and phosphites of Ca, Sr, Ba, Na, and K.

[0036] The acid acceptor is preferably at least one selected from the group consisting of metal oxides, metal hydroxides, alkali metal silicates, and metal salts of weak acids.

[0037] The crosslinkable composition of the present disclosure contains a fluororubber. In the present disclosure, the fluororubber is an amorphous fluoropolymer. "Amorphous" means that the magnitude of the melting peak (ΔH) that appears in the differential scanning calorimetry (DSC) (heating rate 10°C / min) or differential thermal analysis (DTA) (heating rate 10°C / min) of the fluoropolymer is 4.5 J / g or less. The fluororubber exhibits elastomeric properties by crosslinking. Elastomeric properties refer to the property that the polymer can be stretched and can retain its original length when the force required to stretch the polymer is no longer applied.

[0038] The fluororubber may be a partially fluorinated rubber or a perfluororubber.

[0039] In the present disclosure, the partially fluorinated rubber is a fluoropolymer that contains fluoromonomer units and has a perfluoromonomer unit content of less than 90 mol% relative to all polymerized units, has a glass transition temperature of 20°C or less, and has a melting peak (ΔH) magnitude of 4.5 J / g or less.

[0040] In the present disclosure, perfluororubber (perfluoroelastomer) is a fluoropolymer having a perfluoromonomer unit content of 90 mol% or more, preferably 91 mol% or more, relative to the total polymerized units, a glass transition temperature of 20°C or less, a melting peak (ΔH) of 4.5 J / g or less, and a fluorine atom concentration of 71 mass% or more, preferably 71.5 mass% or more. In the present disclosure, the fluorine atom concentration of the fluoropolymer is calculated from the type and content of each monomer constituting the fluoropolymer to determine the concentration of fluorine atoms (mass%).

[0041] In the present disclosure, a perfluoromonomer is a monomer that does not contain a carbon atom-hydrogen atom bond in the molecule. The perfluoromonomer may be a monomer in which some of the fluorine atoms bonded to the carbon atom are replaced with chlorine atoms, in addition to carbon atoms and fluorine atoms, and may also have nitrogen atoms, oxygen atoms, sulfur atoms, phosphorus atoms, boron atoms, or silicon atoms in addition to carbon atoms. The perfluoromonomer is preferably a monomer in which all hydrogen atoms are replaced with fluorine atoms. The perfluoromonomer does not include a monomer that provides a crosslinking site.

[0042] The monomer that provides a crosslinking site is a monomer (cure site monomer) having a crosslinkable group that provides a crosslinking site to the fluoropolymer for forming a crosslink with a crosslinking agent.

[0043] The fluororubber used in the present disclosure is not particularly limited, and examples thereof include peroxide-crosslinkable fluororubber, polyol-crosslinkable fluororubber, etc. In addition, it may be a fluororubber that can be crosslinked using a pyridinium-type salt described in JP-A-2018-514627.

[0044] The polyol-crosslinkable fluororubber is a fluororubber having a polyol-crosslinkable site. The polyol-crosslinkable fluororubber is preferably a polyol-crosslinkable partially fluorinated rubber. The polyol-crosslinkable fluororubber is not particularly limited, and may be a vinylidene fluoride (VdF)-based fluororubber.

[0045] As the fluororubber, peroxide-crosslinkable fluororubber is preferable. The peroxide-crosslinkable fluororubber is not particularly limited, and may be any fluororubber having a peroxide-crosslinkable site. The peroxide-crosslinkable site is not particularly limited, and may be, for example, an iodine atom, a bromine atom, or a CN group contained in the fluororubber; or a carbon-carbon unsaturated bond present in the main chain or side chain of the fluororubber; or the like.

[0046] The fluororubber may be a partially fluorinated rubber or a perfluororubber. As the fluororubber, the partially fluorinated rubber is preferable, and the peroxide-crosslinkable partially fluorinated rubber is more preferable. The monomer composition of the fluororubber will be described in detail below, and the monomer composition described in detail below is suitable as the monomer composition of the peroxide-crosslinkable fluororubber and the polyol-crosslinkable fluororubber, and is particularly suitable as the monomer composition of the peroxide-crosslinkable fluororubber.

[0047] Partially fluorinated rubbers include, for example, tetrafluoroethylene (TFE), vinylidene fluoride (VdF) and the general formula: CF2=CF-Rf a (In the formula, Rf a -CF3 or -ORf b (Rf b It is preferable that the partially fluorinated rubber contains a monomer unit based on at least one monomer selected from the group consisting of perfluoroethylenically unsaturated compounds represented by the formula (I) (wherein R is a perfluoroalkyl group having 1 to 5 carbon atoms) (e.g., hexafluoropropylene (HFP), perfluoro(alkyl vinyl ether) (PAVE), etc.). In particular, it is preferable that the partially fluorinated rubber contains a VdF unit or a TFE unit.

[0048] Examples of partially fluorinated rubber include vinylidene fluoride (VdF)-based fluororubber, tetrafluoroethylene (TFE) / propylene (Pr)-based fluororubber, tetrafluoroethylene (TFE) / propylene / vinylidene fluoride (VdF)-based fluororubber, ethylene / hexafluoropropylene (HFP)-based fluororubber, ethylene / hexafluoropropylene (HFP) / vinylidene fluoride (VdF)-based fluororubber, ethylene / hexafluoropropylene (HFP) / tetrafluoroethylene (TFE)-based fluororubber, etc. Among these, at least one selected from the group consisting of vinylidene fluoride-based fluororubber and tetrafluoroethylene / propylene-based fluororubber is preferable.

[0049] As the fluororubber, at least one selected from the group consisting of vinylidene fluoride-based fluororubber, tetrafluoroethylene / propylene-based fluororubber, and perfluoro fluororubber is preferable.

[0050] The vinylidene fluoride-based fluororubber is preferably a copolymer consisting of 45 to 85 mol % of vinylidene fluoride and 55 to 15 mol % of at least one other monomer copolymerizable with vinylidene fluoride, and more preferably a copolymer consisting of 50 to 80 mol % of vinylidene fluoride and 50 to 20 mol % of at least one other monomer copolymerizable with vinylidene fluoride.

[0051] At least one other monomer copolymerizable with vinylidene fluoride is, for example, tetrafluoroethylene (TFE), hexafluoropropylene (HFP), fluoroalkyl vinyl ether, chlorotrifluoroethylene (CTFE), trifluoroethylene, trifluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutene, hexafluoroisobutene, vinyl fluoride, or a monomer represented by the general formula (100): CHX 101 =CX 102 Rf 101 (In the formula, X101 and X 102 is H on one side and F on the other side, and Rf 101 is a straight-chain or branched fluoroalkyl group having 1 to 12 carbon atoms), a fluoromonomer represented by the general formula (170): CH2=CH-(CF2) n -X 171 (In the formula, X 171 is H or F, and n is an integer of 3 to 10.) and monomers such as monomers that provide crosslinking sites; and non-fluorinated monomers such as ethylene, propylene, and alkyl vinyl ethers. These can be used alone or in any combination.

[0052] Specific examples of vinylidene fluoride-based fluororubbers include VdF / HFP-based rubbers, VdF / HFP / TFE-based rubbers, VdF / CTFE-based rubbers, VdF / CTFE / TFE-based rubbers, VDF / fluoromonomer-based rubbers represented by general formula (100), VDF / fluoromonomer-based rubbers represented by general formula (100) / TFE-based rubbers, VDF / perfluoro(methyl vinyl ether) [PMVE]-based rubbers, VDF / PMVE / TFE-based rubbers, and VDF / PMVE / TFE / HFP-based rubbers.

[0053] The above-mentioned tetrafluoroethylene / propylene-based fluororubber is preferably a copolymer consisting of 45 to 70 mol % of tetrafluoroethylene, 55 to 30 mol % of propylene, and 0 to 5 mol % of a fluoromonomer that provides a crosslinking site.

[0054] The perfluororubber is preferably at least one selected from the group consisting of perfluororubbers containing TFE, such as TFE / fluoromonomer copolymers represented by general formula (11), (12) or (13) and TFE / fluoromonomer copolymers represented by general formula (11), (12) or (13) / monomer copolymers providing crosslinking sites. General formula (11): CF2=CF-ORf 111 (In the formula, Rf 111Rf represents a perfluoroalkyl group having 1 to 10 carbon atoms. 111 is preferably a perfluoroalkyl group having 1 to 5 carbon atoms. General formula (12): CF2=CFOCF2ORf 121 (In the formula, Rf 121 is a straight-chain or branched perfluoroalkyl group having 1 to 6 carbon atoms, a cyclic perfluoroalkyl group having 5 to 6 carbon atoms, or a straight-chain or branched perfluorooxyalkyl group having 2 to 6 carbon atoms and containing 1 to 3 oxygen atoms. General formula (13): CF2=CFO(CF2CF(Y 131 )O) m (CF2) n F (In the formula, Y 131 represents a fluorine atom or a trifluoromethyl group; m is an integer of 1 to 4; and n is an integer of 1 to 4.

[0055] The fluoromonomer represented by general formula (11) is preferably at least one selected from the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), and perfluoro(propyl vinyl ether), and more preferably at least one selected from the group consisting of perfluoro(methyl vinyl ether) and perfluoro(propyl vinyl ether).

[0056] The fluoromonomer represented by general formula (12) is preferably at least one selected from the group consisting of CF2=CFOCF2OCF3, CF2=CFOCF2OCF2CF3, and CF2=CFOCF2OCF2CF2OCF3.

[0057] The fluoromonomer represented by general formula (13) is preferably at least one selected from the group consisting of CF2=CFOCF2CF(CF3)O(CF2)3F, CF2=CFO(CF2CF(CF3)O)2(CF2)3F, and CF2=CFO(CF2CF(CF3)O)2(CF2)2F.

[0058] The composition of the TFE / PMVE copolymer is preferably 45-90 / 10-55 (mol %), more preferably 55-80 / 20-45, and further preferably 55-70 / 30-45.

[0059] The composition of the copolymer of TFE / PMVE / monomer that provides a crosslinking site is preferably 45-89.9 / 10-54.9 / 0.01-4 (mol %), more preferably 55-77.9 / 20-49.9 / 0.1-3.5, and further preferably 55-69.8 / 30-44.8 / 0.2-3.

[0060] The composition of TFE / fluoromonomer copolymer having 4 to 12 carbon atoms and represented by general formula (11), (12) or (13) is preferably 50 to 90 / 10 to 50 (mol %), more preferably 60 to 88 / 12 to 40, and further preferably 65 to 85 / 15 to 35.

[0061] The composition of TFE / fluoromonomer having 4 to 12 carbon atoms represented by general formula (11), (12) or (13) / monomer copolymer providing a crosslinking site is preferably 50 to 89.9 / 10 to 49.9 / 0.01 to 4 (mol %), more preferably 60 to 87.9 / 12 to 39.9 / 0.1 to 3.5, and still more preferably 65 to 84.8 / 15 to 34.8 / 0.2 to 3.

[0062] Outside these composition ranges, the rubber elastic properties are lost and the properties tend to become more like those of a resin.

[0063] The perfluororubber is preferably at least one selected from the group consisting of TFE / fluoromonomer copolymer represented by general formula (13) / which provides a crosslinking site, TFE / perfluorovinyl ether copolymer represented by general formula (13), TFE / fluoromonomer copolymer represented by general formula (11), and TFE / fluoromonomer copolymer represented by general formula (11) / which provides a crosslinking site.

[0064] Examples of the perfluororubber include those described in International Publication No. 97 / 24381, Japanese Patent Publication No. 61-57324, Japanese Patent Publication No. 4-8118, and Japanese Patent Publication No. 5-13961.

[0065] As the fluororubber, in particular, a fluororubber having a vinylidene fluoride unit and the following general formula (1): CHX 1 =CX 2 Rf (1) (In the formula, X 1 and X 2 one of which is H and the other is F, and Rf is a linear or branched fluoroalkyl group having 1 to 12 carbon atoms.) and at least one selected from the group consisting of tetrafluoroethylene / propylene fluororubbers are preferred.

[0066] Rf in the above general formula (1) is preferably a linear fluoroalkyl group, more preferably a linear perfluoroalkyl group, and preferably has 1 to 6 carbon atoms.

[0067] In the above general formula (1), X 1 is H and X 2 It is preferred that F.

[0068] Examples of the fluorine-containing monomer (1) include CH2=CFCF3, CH2=CFCF2CF3, CH2=CFCF2CF2CF3, CH2=CFCF2CF2CF2CF3, CHF=CHCF3 (1,3,3,3-tetrafluoropropene), and the like, and among these, CH2=CFCF3 (2,3,3,3-tetrafluoropropene) is preferred. As the fluorine-containing monomer (1), one or more kinds of monomers may be used.

[0069] The fluororubber (1) may further contain other monomer units other than the vinylidene fluoride units and the fluorine-containing monomer (1) units. The other monomers are not particularly limited as long as they are copolymerizable with the vinylidene fluoride and the fluorine-containing monomer (1), and one or more kinds of monomers may be used.

[0070] As the other monomer, at least one selected from the group consisting of tetrafluoroethylene [TFE], hexafluoropropylene [HFP], perfluoro (methyl vinyl ether), perfluoro (ethyl vinyl ether), perfluoro (propyl vinyl ether), chlorotrifluoroethylene, trifluoroethylene, hexafluoroisobutene, vinyl fluoride, ethylene, propylene, alkyl vinyl ether, and monomers that provide crosslinking sites is preferred, at least one selected from the group consisting of TFE, hexafluoropropylene, perfluoro (methyl vinyl ether), perfluoro (ethyl vinyl ether), perfluoro (propyl vinyl ether), chlorotrifluoroethylene, trifluoroethylene, hexafluoroisobutene, vinyl fluoride, ethylene, alkyl vinyl ether, and monomers that provide crosslinking sites is more preferred, and TFE is even more preferred.In addition, as the other monomer, it is also one of the preferred forms to use only TFE.

[0071] Examples of the monomer that provides the crosslinking site include: General formula (2):CX 3 2=CX 3 -Rf 1 CHR 1 X 4 (In the formula, X 3 are the same or different and are H, F or -CH3, Rf 1 represents a fluoroalkylene group, a perfluoroalkylene group, a fluoro(poly)oxyalkylene group or a perfluoro(poly)oxyalkylene group; R 1 is H or -CH3, X 4 is I or Br; General formula (3):CX 5 2=CX 5 -Rf 2 X 6 (In the formula, X 5 are the same or different and are H, F or -CH3, Rf 2 represents a fluoroalkylene group, a perfluoroalkylene group, a fluoro(poly)oxyalkylene group or a perfluoro(poly)oxyalkylene group; X 6 is I or Br.) (preferably, a monomer containing iodine or bromine represented by the general formula: CH2=CH(CF2) n I (n is an integer of 2 to 8), General formula (4): CF2=CFO(CF2CF(CF3)O) m (CF2) n -X 7 (In the formula, m is an integer of 0 to 5, n is an integer of 1 to 3, X 7 is a cyano group, a carboxyl group, an alkoxycarbonyl group, I or Br; General formula (5): CH2=CFCF2O(CF(CF3)CF2O) m (CF(CF3)) n -X 8 (In the formula, m is an integer of 0 to 5, n is an integer of 1 to 3, X 8 is a cyano group, a carboxyl group, an alkoxycarbonyl group, I, Br or -CHOH; General formula (6):CR 2 R 3 =CR 4 -Z-CR 5 =CR 6 R 7 (In the formula, R 2 ~R 7 are the same or different and each is H or an alkyl group having 1 to 5 carbon atoms. Z is a linear or branched alkylene group having 1 to 18 carbon atoms, which may have an oxygen atom, a cycloalkylene group having 3 to 18 carbon atoms, an at least partially fluorinated alkylene or oxyalkylene group having 1 to 10 carbon atoms, or -(Q) p -CF2O-(CF2CF2O) m (CF2O) n -CF2-(Q) p - (wherein Q is an alkylene or oxyalkylene group, p is 0 or 1, and m / n is 0.2 to 5), and is a (per)fluoropolyoxyalkylene group having a molecular weight of 500 to 10,000.

[0072] Examples of the monomer represented by the general formula (6) include CH2=CH-(CF2)2-CH=CH2, CH2=CH-(CF2)4-CH=CH2, CH2=CH-(CF2)6-CH=CH2, and the general formula: CH2=CH-Z 1 -CH=CH2(wherein, Z 1 is -CH2OCH2-CF2O-(CF2CF2O) m1 (CF2O) n1 It is a fluoropolyoxyalkylene group represented by --CF2--CH2OCH2--, m1 / n1 is 0.5, and the molecular weight is 2000.

[0073] As the monomer providing the above-mentioned crosslinking site, at least one selected from the group consisting of CF2=CFOCF2CF(CF3)OCF2CF2CN, CF2=CFOCF2CF(CF3)OCF2CF2COOH, CF2=CFOCF2CF2CH2I, CF2=CFOCF2CF(CF3)OCF2CF2CH2I, CH2=CFCF2OCF(CF3)CF2OCF(CF3)CN, CH2=CFCF2OCF(CF3)CF2OCF(CF3)COOH, and CH2=CFCF2OCF(CF3)CF2OCF(CF3)CH2OH are preferred.

[0074] As the monomer that provides the above crosslinking site, CF2=CFOCF2CF2CH2I is particularly preferred since it can improve the crosslinking density in crosslinking using peroxide.

[0075] The molar ratio of vinylidene fluoride units / fluorine-containing monomer (1) units in the fluororubber (1) is preferably 87 / 13 to 20 / 80, the lower limit of the molar ratio of vinylidene fluoride units is more preferably 22 / 78 or more, further preferably 50 / 50 or more, particularly preferably 60 / 40 or more, and the upper limit of the molar ratio of vinylidene fluoride units is more preferably 78 / 22 or less. The content of other monomer units is preferably 0 to 50 mol %, more preferably 1 to 40 mol %, of the total monomer units.

[0076] The fluororubber (1) is preferably a copolymer consisting of only vinylidene fluoride units, fluorine-containing monomer (1) units and other monomer units.

[0077] The fluororubber (1) preferably has at least one of an iodine atom and a bromine atom, and more preferably has an iodine atom. The total content of the iodine atom and the bromine atom in the fluororubber (1) is preferably 0.001 to 10% by mass, since the compression set property of the member is further improved. The upper limit of the total content of the iodine atom and the bromine atom is more preferably 5.0% by mass or less, even more preferably 1.0% by mass or less, particularly preferably 0.7% by mass or less, and most preferably 0.5% by mass or less. The lower limit of the total content of the iodine atom and the bromine atom is more preferably 0.01% by mass or more, even more preferably 0.05% by mass or more, particularly preferably 0.08% by mass or more, and most preferably 0.1% by mass or more. The bonding position of the iodine atom and the bromine atom in the fluororubber (1) may be the terminal of the main chain or the terminal of the side chain of the fluororubber (1), or of course both. In such fluororubber, the iodine terminals or bromine terminals become crosslinking points (crosslinking sites), which not only allows a crosslinked product with high crosslinking density to be obtained, but also makes it easier to carry out peroxide crosslinking.

[0078] The fluororubber (1) may be a copolymer (I) containing only vinylidene fluoride units and fluorine-containing monomer (1) units, with the molar ratio of vinylidene fluoride units / fluorine-containing monomer (1) units being 87 / 13 to 22 / 78; a copolymer (I) containing only vinylidene fluoride units, fluorine-containing monomer (1) units, and other monomer units copolymerizable with vinylidene fluoride and the fluorine-containing monomer (1), with the molar ratio of vinylidene fluoride units / fluorine-containing monomer (1) units being 85 / 15 to 20 / 80, with the other monomer units accounting for 1 to 50 mol % of the total monomer units; and a copolymer (III) which contains vinylidene fluoride units, fluorine-containing monomer (1) units, and other monomer units copolymerizable with vinylidene fluoride and the fluorine-containing monomer (1), in which the molar ratio of vinylidene fluoride units / fluorine-containing monomer (1) units is 85 / 15 to 20 / 80, the other monomer units account for 0 to 50 mol % of the total monomer units, and which has at least one of iodine atoms and bromine atoms, and the total content of iodine atoms and bromine atoms is 0.001 to 10 mass %.

[0079] The copolymer (I) contains only vinylidene fluoride units and fluorine-containing monomer (1) units, and the molar ratio of vinylidene fluoride units / fluorine-containing monomer (1) units is 87 / 13 to 22 / 78. The molar ratio of vinylidene fluoride units / fluorine-containing monomer (1) units in the copolymer (I) is preferably 82 / 18 to 60 / 40.

[0080] The copolymer (II) contains only vinylidene fluoride units, fluorine-containing monomer (1) units, and other monomer units copolymerizable with vinylidene fluoride and the fluorine-containing monomer (1), the molar ratio of vinylidene fluoride units / fluorine-containing monomer (1) units is 85 / 15 to 20 / 80, and the other monomer units account for 1 to 50 mol % of the total monomer units.

[0081] The molar ratio of vinylidene fluoride units / fluorine-containing monomer (1) units in the copolymer (II) is preferably from 85 / 15 to 50 / 50, more preferably from 85 / 15 to 60 / 40.

[0082] The content of other monomer units in the copolymer (II) is preferably 1 to 40 mol % of the total monomer units. As the other monomers contained in the copolymer (II), those mentioned above are suitable.

[0083] The copolymer (III) contains vinylidene fluoride units, fluorine-containing monomer (1) units, and other monomer units copolymerizable with vinylidene fluoride and the fluorine-containing monomer (1), the molar ratio of vinylidene fluoride units / fluorine-containing monomer (1) units is 85 / 15 to 20 / 80, the other monomer units account for 0 to 50 mol % of the total monomer units, and has at least one of iodine atoms and bromine atoms, with the total content of iodine atoms and bromine atoms being 0.001 to 10 mass %.

[0084] The copolymer (III) is preferably a copolymer that contains substantially only vinylidene fluoride units and fluorine-containing monomer (1), or a copolymer that contains substantially only vinylidene fluoride units, fluorine-containing monomer (1) units, and other monomer units copolymerizable with vinylidene fluoride and fluorine-containing monomer (1). In this case, the copolymer (III) may be produced using a reactive emulsifier within a range that does not impair the effects of the present disclosure. In addition, it may contain I terminals derived from a chain transfer agent.

[0085] It is more preferable that the copolymer (III) contains substantially only vinylidene fluoride units and fluorine-containing monomer (1) units, with the molar ratio of vinylidene fluoride units / fluorine-containing monomer (1) units being 80 / 20 to 20 / 80.

[0086] It is also more preferable that the copolymer (III) contains substantially only vinylidene fluoride units, fluorine-containing monomer (1) units, and other monomer units copolymerizable with vinylidene fluoride and the fluorine-containing monomer (1), the molar ratio of vinylidene fluoride units / fluorine-containing monomer (1) units is 85 / 15 to 50 / 50, and the other monomer units account for 1 to 50 mol % of the total monomer units.

[0087] In the present disclosure, the content of each monomer unit is a value measured by NMR.

[0088] The copolymer (III) has at least one of iodine atoms and bromine atoms, and the total content of iodine atoms and bromine atoms is 0.001 to 10 mass%. The upper limit of the total content of iodine atoms and bromine atoms is more preferably 5.0 mass% or less, even more preferably 1.0 mass% or less, particularly preferably 0.7 mass% or less, and most preferably 0.5 mass% or less, and the lower limit of the total content of iodine atoms and bromine atoms is more preferably 0.01 mass% or more, even more preferably 0.05 mass% or more, particularly preferably 0.08 mass% or more, and most preferably 0.1 mass% or more.

[0089] The iodine content can be measured by the following method: Na2CO3 and K2CO3 are mixed in a 1:1 ratio (by weight), and the resulting mixture is dissolved in 20 ml of pure water to prepare an absorbing solution, and 5 mg of Na2SO3 is mixed with 12 mg of a sample (fluoropolymer) to prepare a mixture, which is then burned in oxygen in a quartz flask, and the generated combustion gas is introduced into the absorbing solution, and the resulting absorbing solution is left to stand for 30 minutes, after which the concentration of iodine ions in the absorbing solution is measured using a Shimadzu 20A ion chromatograph, and the iodine ion content can be determined from the measured value using a calibration curve prepared using a KI standard solution containing 0.5 ppm iodine ions and a KI standard solution containing 1.0 ppm iodine ions.

[0090] The bonding positions of the iodine atom and the bromine atom in the copolymer (III) may be the terminals of the main chain or the terminals of the side chain of the copolymer (III), or may be both. In such a copolymer, the iodine terminals or the bromine terminals become crosslinking points (crosslinking sites), and a crosslinked product with high crosslinking density can be obtained, and peroxide crosslinking can be performed more easily.

[0091] The copolymer (III) can be produced by a production method using an iodine- or bromine-containing monomer as a monomer that provides a crosslinking site, a production method using a bromine compound or an iodine compound as a polymerization initiator or chain transfer agent, or the like.

[0092] In the copolymer (III), the other monomers are not particularly limited so long as they are monomers copolymerizable with vinylidene fluoride and the fluorine-containing monomer (1), and one or more kinds of monomers may be used.

[0093] The content of other monomer units in the copolymer (III) is preferably 0 to 50 mol % of the total monomer units, and more preferably 1 to 50 mol % of the total monomer units.

[0094] In the copolymer (III), examples of the monomer that provides the crosslinking site include the monomers represented by the above general formulas (2) to (6).

[0095] In the copolymer (III), the monomer providing the crosslinking site is preferably at least one selected from the group consisting of CF2=CFOCF2CF(CF3)OCF2CF2CN, CF2=CFOCF2CF(CF3)OCF2CF2COOH, CF2=CFOCF2CF(CF3)OCF2CF2CH2I, CF2=CFOCF2CF2CH2I, CH2=CFCF2OCF(CF3)CF2OCF(CF3)CN, CH2=CFCF2OCF(CF3)CF2OCF(CF3)COOH, CH2=CFCF2OCF(CF3)CF2OCF(CF3)CH2OH, CH2=CHCF2CF2I, and CH2=CH(CF2)2CH=CH2.

[0096] In the copolymer (III), as a monomer that provides a crosslinking site, CF2=CFOCF2CF2CH2I is particularly preferred because it can improve the crosslinking density in crosslinking using peroxide.

[0097] In the copolymer (III), the content of the monomer providing the crosslinking site is preferably from 0.01 to 10 mol %, more preferably from 0.01 to 2 mol %, of the total monomer units.

[0098] As the fluororubber (1), the copolymer (III) is more preferable.

[0099] The glass transition temperature of the fluororubber (1) may be 25° C. or lower, preferably 0° C. or lower, more preferably −5° C. or lower, and even more preferably −10° C. or lower. It can also be −20° C. or lower.

[0100] The glass transition temperature is determined by obtaining a DSC curve using a differential scanning calorimeter (Hitachi High-Tech Science Corporation, X-DSC7000) by cooling 10 mg of a sample to -75°C and then heating at 20°C / min, and determining the glass transition temperature as the temperature indicating the intersection between an extension of the baseline before and after the second-order transition of the DSC curve and a tangent to the inflection point of the DSC curve.

[0101] In view of excellent sealing properties, the fluororubber (1) preferably has a number average molecular weight (Mn) of 7,000 to 500,000, a weight average molecular weight (Mw) of 10,000 to 1,000,000, and Mw / Mn of 1.3 to 8.0. The number average molecular weight (Mn), weight average molecular weight (Mw), and Mw / Mn are values ​​measured by a GPC method.

[0102] The Mooney viscosity (ML1+10(100°C)) of the fluororubber (1) at 100°C is preferably 2 or more, more preferably 5 or more, and even more preferably 10 or more, because a good molding state can be obtained. Also, it is preferably 200 or less, more preferably 120 or less, even more preferably 100 or less, and particularly preferably 80 or less. The Mooney viscosity is a value measured in accordance with ASTM-D1646-15 and JIS K6300-1:2013.

[0103] The fluororubber (1) can be produced by a general radical polymerization method. The polymerization form may be any of bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization, but emulsion polymerization is preferred because it is easy to carry out industrially.

[0104] In the above polymerization, a polymerization initiator, a chain transfer agent, a surfactant, and a solvent can be used, and conventionally known polymerization initiators, chain transfer agents, surfactants, and solvents can be used.

[0105] Examples of chain transfer agents include esters such as dimethyl malonate, diethyl malonate, methyl acetate, ethyl acetate, butyl acetate, and dimethyl succinate, as well as isopentane, methane, ethane, propane, 2-propanol, acetone, various mercaptans, carbon tetrachloride, and cyclohexane.

[0106] Bromine compounds or iodine compounds may be used as chain transfer agents. Polymerization methods using bromine compounds or iodine compounds include, for example, emulsion polymerization in an aqueous medium under pressure in the presence of a bromine compound or iodine compound in a substantially oxygen-free state (iodine transfer polymerization method). Representative examples of bromine compounds or iodine compounds to be used include, for example, General formula: R 8 I x Br y (In the formula, x and y are each an integer of 0 to 2, and 1≦x+y≦2 is satisfied; R 8is a saturated or unsaturated fluorohydrocarbon group or chlorofluorohydrocarbon group having 1 to 16 carbon atoms, or a hydrocarbon group having 1 to 3 carbon atoms, which may contain an oxygen atom). By using a bromine compound or an iodine compound, an iodine atom or a bromine atom is introduced into the polymer and functions as a crosslinking point.

[0107] Examples of bromine compounds and iodine compounds include 1,3-diiodoperfluoropropane, 2-iodoperfluoropropane, 1,3-diiodo-2-chloroperfluoropropane, 1,4-diiodoperfluorobutane, 1,5-diiodo-2,4-dichloroperfluoropentane, 1,6-diiodoperfluorohexane, 1,8-diiodoperfluorooctane, 1,12-diiodoperfluorododecane, 1,16-diiodoperfluorohexadecane, diiodomethane, 1,2-diiodoethane, 1,3-diiodo-n-propane, CF2Br2, BrCF2CF2Br, CF3CFBrCF2Br, CFClBr2, BrCF2 Examples of the iodoperfluoroalkyl group include CFClBr, CFBrClCFClBr, BrCF2CF2CF2Br, BrCF2CFBrOCF3, 1-bromo-2-iodoperfluoroethane, 1-bromo-3-iodoperfluoropropane, 1-bromo-4-iodoperfluorobutane, 2-bromo-3-iodoperfluorobutane, 3-bromo-4-iodoperfluorobutene-1, 2-bromo-4-iodoperfluorobutene-1, monoiodomonobromo-substituted benzene, diiodomonobromo-substituted benzene, and (2-iodoethyl) and (2-bromoethyl)-substituted benzene. These compounds may be used alone or in combination with each other.

[0108] Among these, it is preferable to use 1,4-diiodoperfluorobutane, 1,6-diiodoperfluorohexane, and 2-iodoperfluoropropane in terms of polymerization reactivity, crosslinking reactivity, availability, and the like.

[0109] In the polymerization for producing the fluororubber (1), particularly the copolymer (III), it is preferable to use a bromine compound or an iodine compound as a chain transfer agent.

[0110] The fluororubber (1) may be used either alone or in combination of two or more kinds, particularly in the form of a combination of two kinds of copolymers having different molecular structures.

[0111] Examples of the combined use of two copolymers having different molecular structures include the combined use of two copolymers (I) having different molecular structures, the combined use of two copolymers (II) having different molecular structures, the combined use of two copolymers (III) having different molecular structures, the combined use of one type of copolymer (I) and one type of copolymer (II), the combined use of one type of copolymer (I) and one type of copolymer (III), and the combined use of one type of copolymer (II) and one type of copolymer (III).

[0112] The crosslinkable composition of the present disclosure contains a crosslinking agent. Examples of the crosslinking agent include crosslinking agents that are usually used in polyol crosslinking and peroxide crosslinking. The crosslinking agent is preferably at least one selected from the group consisting of polyhydroxy compounds and peroxides, and more preferably peroxides. When the nitric acid resistance of the member is important, peroxide crosslinking is suitable, but when a laminate or composite part is formed by vulcanizing and bonding a fluororubber crosslinked product with another material, and sufficient vulcanization bonding is difficult to achieve with peroxide crosslinking, it may be necessary to select polyol crosslinking to achieve both nitric acid resistance and adhesion.

[0113] When the crosslinkable composition of the present disclosure contains a polyol-crosslinkable fluororubber, it is preferable to contain a polyhydroxy compound as a crosslinking agent. When the crosslinkable composition of the present disclosure contains a peroxide-crosslinkable fluororubber, it is preferable to contain a peroxide as a crosslinking agent. In addition, when using a fluororubber that can be crosslinked using a pyridinium-type salt described in JP-A-2018-514627 as the fluororubber, a pyridinium salt can be used as a crosslinking agent.

[0114] The crosslinkable composition of the present disclosure may also contain a crosslinking accelerator, a basic compound, a co-crosslinking agent, and the like.

[0115] As the polyhydroxy compound, a polyhydroxy aromatic compound is preferably used because of its excellent heat resistance.The polyhydroxy aromatic compound is not particularly limited, and examples thereof include 2,2-bis(4-hydroxyphenyl)propane (hereinafter referred to as bisphenol A), 2,2-bis(4-hydroxyphenyl)perfluoropropane (hereinafter referred to as bisphenol AF), resorcin, 1,3-dihydroxybenzene, 1,7-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxystilbene, 2,6-dihydroxyanthracene, hydroquinone, catechol, 2,2-bis(4-hydroxyphenyl)butane (hereinafter referred to as bisphenol AF), and the like. phenol B), 4,4-bis(4-hydroxyphenyl)valeric acid, 2,2-bis(4-hydroxyphenyl)tetrafluorodichloropropane, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl ketone, tri(4-hydroxyphenyl)methane, 3,3',5,5'-tetrachlorobisphenol A, 3,3',5,5'-tetrabromobisphenol A, 2,6-dihydroxy-9H-fluoren-9-one, 3,6-dihydroxy-9H-fluoren-9-one, 2,7-dihydroxy-9H-fluoren-9-one, spiro[fluorene-9,9'-xanthene]-3',6'-diol, fluorescein (CAS No. 2321-07-5), 9,9-bis(4-hydroxyphenyl)fluorene, 2,2'-biphenol, 2,3'-biphenol, 2,4'-biphenol, 3,3'-biphenol, 3,4'-biphenol, 2,6-dihydroxyanthraquinone, 2,7-dihydroxyanthraquinone, 1,1,1-trifluoro-2,2,2-tris(4-hydroxyphenyl)ethane, 4,4',4"-trihydroxytriphenylmethane, 1,1,1-tris(4-hydroxyphenyl)ethane, 3,6-dihydroxy-9H-xanthen-9-one, 4-fluororesorcinol, 5-fluororesorcinol, 4-chlororesorcinol, 4',7-dihydroxyisoflavone, 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol, and 6-hydroxy-3-coumaranone.

[0116] The content of the polyhydroxy compound is preferably from 0.05 to 10 parts by mass, and more preferably from 0.5 to 5 parts by mass, based on 100 parts by mass of the fluororubber.

[0117] A crosslinking agent such as a polyhydroxy compound can be mixed with other compounds. Examples of mixtures containing a crosslinking agent include a solid solution of a crosslinking agent and a crosslinking promoter, and a mixture of a crosslinking agent and a compound that can dissolve the crosslinking agent. A preferred solid solution is a solid solution of a crosslinking agent and a quaternary phosphonium salt. A preferred quaternary phosphonium salt is benzyltriphenylphosphonium chloride.

[0118] When the crosslinking agent is a polyhydroxy compound, the crosslinkable composition of the present disclosure preferably contains a crosslinking accelerator, which accelerates the formation of intramolecular double bonds in the dehydrofluorination reaction of the polymer main chain and the addition of the polyhydroxy compound to the double bonds thus formed.

[0119] The crosslinking accelerator may be an onium compound. Among the onium compounds, at least one selected from the group consisting of ammonium compounds such as quaternary ammonium salts, phosphonium compounds such as quaternary phosphonium salts, oxonium compounds, sulfonium compounds, cyclic amines, and monofunctional amine compounds is preferred, and at least one selected from the group consisting of quaternary ammonium salts and quaternary phosphonium salts is more preferred.

[0120] The quaternary ammonium salt is not particularly limited, and examples thereof include 8-methyl-1,8-diazabicyclo[5.4.0]-7-undecenium chloride, 8-methyl-1,8-diazabicyclo[5.4.0]-7-undecenium iodide, 8-methyl-1,8-diazabicyclo[5.4.0]-7-undecenium hydroxide, 8-methyl-1,8-diazabicyclo[5.4.0]-7-undecenium methyl sulfate, 8-ethyl-1,8-diazabicyclo[5.4.0]-7-undecenium bromide, 8-propyl-1,8-diazabicyclo[5.4.0]-7-undecenium bromide, 8-dodecyl-1,8-diazabicyclo[5.4.0]-7-undecenium chloride, 8-dodecyl Examples of the DBU-B include 8-benzyl-1,8-diazabicyclo[5.4.0]-7-undecenium hydroxide, 8-eicosyl-1,8-diazabicyclo[5.4.0]-7-undecenium chloride, 8-tetracosyl-1,8-diazabicyclo[5.4.0]-7-undecenium chloride, 8-benzyl-1,8-diazabicyclo[5.4.0]-7-undecenium chloride (hereinafter referred to as DBU-B), 8-benzyl-1,8-diazabicyclo[5.4.0]-7-undecenium hydroxide, 8-phenethyl-1,8-diazabicyclo[5.4.0]-7-undecenium chloride, and 8-(3-phenylpropyl)-1,8-diazabicyclo[5.4.0]-7-undecenium chloride. Among these, DBU-B is preferred because of its excellent crosslinkability and various physical properties.

[0121] The quaternary phosphonium salt is not particularly limited, and examples thereof include tetrabutyl phosphonium chloride, benzyl triphenyl phosphonium chloride (hereinafter referred to as BTPPC), benzyl trimethyl phosphonium chloride, benzyl tributyl phosphonium chloride, tributyl allyl phosphonium chloride, tributyl-2-methoxypropyl phosphonium chloride, and benzyl phenyl (dimethylamino) phosphonium chloride. Among these, benzyl triphenyl phosphonium chloride (BTPPC) is preferred because of its excellent crosslinkability and various physical properties.

[0122] When the crosslinking agent is a polyhydroxy compound, a vulcanization accelerator for fluorine-containing elastomers containing bisphenol AF as a crosslinking agent, as disclosed in JP-A-11-147891, or an adduct of a quaternary phosphonium salt and a polyhydroxy compound containing a polyhydroxy compound as a crosslinking agent, as described in JP-A-2010-150563, can also be used. When these compounds (mixtures) are used as the crosslinking agent and crosslinking accelerator, the content (parts by mass) of the crosslinking agent is the value obtained by subtracting the content of the crosslinking accelerator in the compound from the content of the compound relative to 100 parts by mass of fluororubber.

[0123] The content of the crosslinking accelerator is not particularly limited, but is preferably 0.05 to 5 parts by mass, and more preferably 0.5 to 1 part by mass, based on 100 parts by mass of the fluororubber.

[0124] When the vulcanization accelerator for fluorine-containing elastomers disclosed in JP-A-11-147891 and the adduct of a quaternary phosphonium salt and a polyhydroxy compound described in JP-A-2010-150563 are used as the crosslinking agent and crosslinking accelerator, the content of the crosslinking accelerator is the value obtained by subtracting the content of the crosslinking agent in the compound from the content of these compounds per 100 parts by mass of the fluororubber.

[0125] Examples of pyridinium salts include those described in JP-T-2018-514627. As a suitable content of the pyridinium salt, the content described in JP-T-2018-514627 can also be applied to the crosslinkable composition of the present disclosure.

[0126] When the crosslinking agent is a pyridinium salt, the crosslinkable composition of the present disclosure preferably contains a basic compound. The basic compound may be the basic compound described in JP-T-2018-514627. The content of the basic compound described in JP-T-2018-514627 can also be applied to the crosslinkable composition of the present disclosure.

[0127] The peroxide is not particularly limited as long as it is a crosslinking agent that is usually used for peroxide crosslinking, and generally, it is preferable to use one that easily generates peroxy radicals in the presence of heat or an oxidation-reduction system.Specific examples include 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, α,α'-bis(t-butylperoxy)-p-diisopropylbenzene, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, 2,5-dimethyl-2,5-bis(t-butylperoxy)-hexyne-3, benzoyl peroxide, t-butylperoxybenzene, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxymaleic acid, t-butylperoxyisopropyl carbonate, and t-butylperoxybenzoate. Among these, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane and 2,5-dimethyl-2,5-bis(t-butylperoxy)-hexyne-3 are preferred.

[0128] The content of the peroxide is preferably from 0.05 to 10 parts by mass, and more preferably from 1.0 to 5 parts by mass, based on 100 parts by mass of the fluororubber.

[0129] When the crosslinking agent is a peroxide, the crosslinkable composition of the present disclosure preferably contains a co-crosslinking agent. Examples of the co-crosslinking agent include triallyl cyanurate, trimethallyl isocyanurate, triallyl isocyanurate (TAIC), triacrylformal, triallyl trimellitate, N,N'-m-phenylene bismaleimide, dipropargyl terephthalate, diallyl phthalate, tetraallyl terephthalate amide, triallyl phosphate, bismaleimide, fluorinated triallyl isocyanurate (1,3,5-tris(2,3,3-trifluoro-2-propenyl)-1,3,5-triazine, etc. Examples of the fluororubber include tris(diallylamine)-S-triazine, triallyl phosphite, N,N-diallylacrylamide, 1,6-divinyldodecafluorohexane, hexaallyl phosphoramide, N,N,N',N'-tetraallylphthalamide, N,N,N',N'-tetraallylmalonamide, trivinyl isocyanurate, 2,4,6-trivinylmethyltrisiloxane, tri(5-norbornene-2-methylene) cyanurate, and triallyl phosphite. Among these, triallyl isocyanurate (TAIC) is preferred. When kneading the fluororubber and the co-crosslinking agent, the co-crosslinking agent may be impregnated into an inactive inorganic powder or the like.

[0130] The content of the co-crosslinking agent is preferably from 0.1 to 10 parts by mass, and more preferably from 0.5 to 5 parts by mass, based on 100 parts by mass of the fluororubber.

[0131] The crosslinkable composition of the present disclosure may contain various additives, such as usual additives that are blended into fluororubber crosslinkable compositions as necessary, for example, fillers (carbon black, bituminous coal, barium sulfate, diatomaceous earth, calcined clay, talc, etc.), processing aids (wax, etc.), plasticizers, colorants, stabilizers, tackifiers (coumarone resins, coumarone-indene resins, etc.), release agents, electrical conductivity imparting agents, thermal conductivity imparting agents, surface non-tacky agents, flexibility imparting agents, heat resistance improving agents, flame retardants, foaming agents, and antioxidants described in WO 2012 / 023485, and may also contain one or more usual crosslinking agents and crosslinking accelerators different from the above.

[0132] Examples of the filler include metal oxides such as titanium oxide and aluminum oxide; metal hydroxides such as magnesium hydroxide and aluminum hydroxide; carbonates such as magnesium carbonate, aluminum carbonate, calcium carbonate, and barium carbonate; silicates such as magnesium silicate, calcium silicate, and aluminum silicate; sulfates such as aluminum sulfate, calcium sulfate, and barium sulfate; metal sulfides such as molybdenum disulfide, iron sulfide, and copper sulfide; diatomaceous earth, asbestos, lithopone (zinc sulfide / barium sulfide), graphite, carbon fluoride, calcium fluoride, coke, quartz fine powder, talc, mica powder, wollastonite, carbon fiber, aramid fiber, various whiskers, glass fiber, organic reinforcing agents, organic fillers, polytetrafluoroethylene, fluorine-containing thermoplastic resins, mica, silica, celite, clay, and the like.

[0133] The content of the filler such as carbon black is not particularly limited, but is preferably 0 to 300 parts by mass, more preferably 1 to 150 parts by mass, further preferably 2 to 100 parts by mass, and particularly preferably 2 to 75 parts by mass, relative to 100 parts by mass of the fluororubber.

[0134] The content of processing aids such as wax is preferably 0 to 10 parts by mass, more preferably 0 to 5 parts by mass, based on 100 parts by mass of fluororubber. When processing aids, plasticizers, and release agents are used, the mechanical properties and sealing properties of the resulting molded product tend to decrease, so it is necessary to adjust the content of these agents within a range that allows the properties of the desired molded product to be obtained.

[0135] The crosslinkable composition of the present disclosure may contain a dialkyl sulfone compound. Examples of the dialkyl sulfone compound include dimethyl sulfone, diethyl sulfone, dibutyl sulfone, methyl ethyl sulfone, diphenyl sulfone, and sulfolane. The content of the dialkyl sulfone compound is preferably 0 to 10 parts by mass, more preferably 0 to 5 parts by mass, and particularly preferably 0 to 3 parts by mass, relative to 100 parts by mass of the fluororubber. When the crosslinkable composition of the present disclosure contains a dialkyl sulfone compound, the lower limit of the content of the dialkyl sulfone compound may be, for example, 0.1 parts by mass or more relative to 100 parts by mass of the fluororubber.

[0136] The crosslinkable composition of the present disclosure can be obtained by kneading, using a commonly used rubber kneading device, the fluororubber, hydrotalcites, a crosslinking agent, a co-crosslinking agent, a crosslinking accelerator, a filler, etc. Examples of the rubber kneading device that can be used include a roll, a kneader, a Banbury mixer, an internal mixer, and a twin-screw extruder.

[0137] The method for crosslinking the crosslinkable composition of the present disclosure may be any of the commonly used methods such as press crosslinking, steam crosslinking, and oven crosslinking, as well as normal pressure, pressurized pressure, reduced pressure, and in air, and may be any condition. The crosslinking conditions may be appropriately determined depending on the type of crosslinking agent used, and are usually heated at a temperature of 150 to 300°C for 1 minute to 24 hours. In the case of press crosslinking and steam crosslinking, it is preferable to perform the crosslinking at a temperature of 150 to 180°C, and the crosslinking time may be at least up to the crosslinking time T90, for example, 1 minute to 2 hours. In the case of oven crosslinking after that (after press crosslinking or steam crosslinking), it is preferable to perform the crosslinking at a temperature of 170°C to 250°C, but this is not necessarily required, and the crosslinking time of oven crosslinking is preferably, for example, 0 to 48 hours.

[0138] The component of the air management system of the ammonia combustion engine of the present disclosure contains a fluororubber cross-linked product obtained by cross-linking the cross-linkable composition. The component of the present disclosure may be, for example, a hose, a sealing material, etc.

[0139] The members of the present disclosure can be suitably used, for example, as members of the intake and exhaust systems of an ammonia combustion engine.

[0140] Specific uses in the above intake and exhaust systems include packings used in intake manifolds, exhaust manifolds, etc., throttle body packings for throttles; EGR (exhaust gas recirculation), pressure control (BPT), wastegates, turbo wastegates, actuators, variable turbine geometry (VTG) turbo actuators, diaphragms used in exhaust purification valves, etc.; EGR (exhaust gas recirculation) control hoses, emission control hoses, turbocharger turbo oil hoses (supply), turbo oil hoses (return), turbo air hoses, intercooler hoses, etc. These include hoses such as hoses, turbocharger hoses, hoses connected to the compressor of a turbo engine equipped with an intercooler, exhaust gas hoses, air intake hoses, turbo hoses, DPF (diesel particulate filter) sensor hoses, etc.; air ducts and turbo air ducts; intake manifold gaskets; EGR sealing materials, afterburn prevention valve seats for AB valves, turbine shaft seals (for turbochargers, etc.), sealing materials used in grooved parts such as rocker covers and air intake manifolds used in automobile engines, and components for urea SCR systems.

[0141] Other applications include seals for vapor recovery canisters, catalytic converters, exhaust gas sensors, oxygen sensors, etc. in emission control components; seals for vapor recovery and vapor canister solenoid armatures; and intake manifold gaskets.

[0142] Although the embodiments have been described above, it will be understood that various changes in form and details are possible without departing from the spirit and scope of the claims. EXAMPLES

[0143] Next, embodiments of the present disclosure will be described with reference to examples, but the present disclosure is not limited to these examples.

[0144] The values ​​in the examples were measured by the following methods.

[0145] <Monomer composition of fluororubber> 19 The measurements were performed using an F-NMR (Bruker AC300P model).

[0146] <Mooney viscosity> Measurements were performed in accordance with ASTM D1646-15 and JIS K6300-1:2013 at a temperature of 100°C.

[0147] <Iodine content> An absorbing solution was prepared by mixing Na2CO3 and K2CO3 in a 1:1 ratio (by weight) and dissolving the resulting mixture in 20 ml of pure water. A mixture was prepared by mixing 12 mg of sample (fluororubber) with 5 mg of Na2SO3, and burning it in oxygen in a quartz flask, and the generated combustion gas was introduced into the absorbing solution. After leaving the resulting absorbing solution for 30 minutes, the concentration of iodine ions in the absorbing solution was measured using a Shimadzu 20A ion chromatograph. The iodine ion content was determined using a calibration curve created using a KI standard solution containing 0.5 ppm iodine ions and a KI standard solution containing 1.0 ppm iodine ions.

[0148] <Cross-linking characteristics (maximum torque (MH), optimal cross-linking time (T90))> For the crosslinkable composition, a crosslinking curve was obtained under the conditions described in Tables 1 to 3 using a vulcanization tester (MDR H2030, manufactured by M&K Co., Ltd.) or a vulcanization tester (RUBBER PROCESSANALYZER RPA2000, manufactured by Alpha Technologies Acquisition Co., Ltd.) during the primary crosslinking, and the maximum torque (MH) and optimal crosslinking time (T90) were obtained from the change in torque.

[0149] <Tensile strength and elongation at break> A test piece in the shape of a dumbbell No. 6 was prepared from a crosslinked sheet with a thickness of 2 mm. Using the obtained test piece and a tensile tester (A&D Corporation, Tensilon RTG-1310), the tensile strength and elongation at break were measured at 23°C under the condition of 500 mm / min in accordance with JIS K6251:2010.

[0150] <Hardness> Using three stacked crosslinked sheets each having a thickness of 2 mm, the hardness (Peak value, value after 3 seconds) was measured using a Type A durometer in accordance with JIS K6253-3:2012.

[0151] <Nitric acid resistance (1)> A crosslinked sheet having a thickness of 2 mm was immersed in a 5% by mass aqueous solution of nitric acid at 90°C for 72 hours, and the crosslinked sheet was collected. The specific gravity and mass of the crosslinked sheet before and after immersion were measured, and the volume change rate was calculated according to the following formula. The specific gravity was measured using an automatic specific gravity meter DMA-220H (manufactured by Shinko Denshi Co., Ltd.). Volume change rate (%) = {[(mass of crosslinked sheet after immersion) / (specific gravity of crosslinked sheet after immersion)] - [(mass of crosslinked sheet before immersion) / (specific gravity of crosslinked sheet before immersion)]} / [(mass of crosslinked sheet before immersion)] / (specific gravity of crosslinked sheet before immersion)] × 100

[0152] <Nitric acid resistance (2)> A crosslinked sheet having a thickness of 2 mm was immersed in a 60% by mass aqueous solution of nitric acid at 80° C. for 72 hours, and the crosslinked sheet was recovered. The specific gravity and mass of the crosslinked sheet before and after immersion were measured, and the volume change rate was calculated according to the following formula. Volume change rate (%) = {[(mass of crosslinked sheet after immersion) / (specific gravity of crosslinked sheet after immersion)] - [(mass of crosslinked sheet before immersion) / (specific gravity of crosslinked sheet before immersion)]} / [(mass of crosslinked sheet before immersion)] / (specific gravity of crosslinked sheet before immersion)] × 100

[0153] In the examples and comparative examples, the following materials were used. Fluorine Rubber A Peroxide crosslinkable fluororubber VdF / TFE / HFP=50 / 30 / 20 (molar ratio) Mooney Viscosity (ML(1+10)100℃):52 Iodine content: 0.23% by mass Fluorine Rubber B Peroxide crosslinkable fluororubber VdF / 2,3,3,3-tetrafluoropropene=77 / 23 (molar ratio) Mooney Viscosity (ML(1+10)100℃):45 Iodine content: 0.21% by mass Fluorine Rubber C Polyol crosslinkable fluororubber VdF / TFE / HFP=58 / 20 / 22 (molar ratio) Mooney Viscosity (ML(1+10)100℃):42 Fluorine Rubber D Polyol crosslinkable fluororubber VdF / HFP=78 / 22 (molar ratio) Mooney Viscosity (ML(1+10)100℃):55

[0154] Co-crosslinking agent A: Triallyl isocyanurate Peroxide-based crosslinking agent A: 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane Polyol crosslinker: Bisphenol AF Crosslinking accelerator: DBU-B Hydrotalcite: DHT-4A (Kyowa Chemical Industry Co., Ltd.), Mg 4.3 Al2(OH) 12.6 CO3 mH2O

[0155] Examples 1 to 8 and Comparative Examples 1 to 4 The components were mixed according to the recipes in Tables 1 to 3 and kneaded on an open roll to prepare a crosslinkable composition. The maximum torque (MH) and optimal crosslinking time (T90) of the obtained crosslinkable composition are shown in Tables 1 to 3. Next, the crosslinkable composition was crosslinked by primary crosslinking (press crosslinking) under the conditions shown in Tables 1 to 3 and secondary crosslinking (oven crosslinking) under the conditions shown in Tables 1 to 3 to obtain a crosslinked sheet (thickness 2 mm). The evaluation results of the obtained crosslinked sheet are shown in Tables 1 to 3.

[0156] [Table 1]

[0157] [Table 2]

[0158] [Table 3]

Claims

1. A crosslinkable composition for use in a component of an air management system of an ammonia combustion engine, in which the gas circulating inside the engine contains nitric acid produced from the ammonia combustion gas, comprising: Contains fluororubber and crosslinking agent. moreover, (a) containing hydrotalcite as an acid acceptor, the content of the hydrotalcite being 0.1 to 10 parts by mass per 100 parts by mass of the fluororubber, and the content of the acid acceptor other than the hydrotalcite being 0 to 0.1 parts by mass per 100 parts by mass of the fluororubber, or (b) the acid acceptor contains an acid acceptor other than hydrotalcite or does not contain an acid acceptor, the content of the acid acceptor other than hydrotalcite is 0 to 0.1 parts by mass relative to 100 parts by mass of the fluororubber, and the content of the hydrotalcite is 0 parts by mass or more and less than 0.1 parts by mass relative to 100 parts by mass of the fluororubber, Crosslinkable composition.

2. 2. The crosslinkable composition according to claim 1, wherein in the case of (b), the acid acceptor other than hydrotalcite is at least one selected from the group consisting of metal oxides, metal hydroxides, alkali metal silicates, and metal salts of weak acids.

3. 3. The crosslinkable composition according to claim 1, wherein the fluororubber is a peroxide-crosslinkable fluororubber.

4. 3. The crosslinkable composition according to claim 1, wherein the fluororubber is at least one selected from the group consisting of vinylidene fluoride-based fluororubbers, tetrafluoroethylene / propylene-based fluororubbers, and perfluororubbers.

5. The fluororubber comprises a vinylidene fluoride unit and a fluorocarbon polymer having the following general formula (1): CHX １ =CX ２ Rf (1) (In the formula, X １ and X ２ one of which is H and the other is F, and Rf is a linear or branched fluoroalkyl group having 1 to 12 carbon atoms; and tetrafluoroethylene / propylene fluororubbers.

6. The crosslinkable composition according to claim 5, wherein the fluorine-containing monomer (1) is 2,3,3,3-tetrafluoropropene.

7. The crosslinkable composition according to claim 5, wherein the fluororubber (1) has at least one of an iodine atom and a bromine atom, and the total content of the iodine atom and the bromine atom is 0.001 to 10 mass%.

8. 3. The crosslinkable composition according to claim 1, wherein the crosslinking agent is a peroxide.

9. The crosslinkable composition according to claim 8, further comprising a co-crosslinking agent.

10. A component of an air management system of an ammonia combustion engine, in which the gas circulating inside contains nitric acid produced from ammonia combustion gas, The part comprises a cross-linked fluororubber product obtained by cross-linking the cross-linkable composition according to claim 1 or 2.

11. 3. Use of a crosslinkable composition according to claim 1 or 2 for forming a component of an air management system of an ammonia-burning engine, the internal circulating gases of which contain nitric acid resulting from the ammonia combustion gases.

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