Fluoroelastomer composition, fluororubber molded body, crosslinking agent for producing fluororubber molded body, and compound

Abstract

Provided is a fluoroelastomer composition which comprises: a fluororubber (a) that can be crosslinked with a polyhydroxy compound; and a polyhydroxy compound (b) that has a fluorine atom and a structure in which two aromatic rings are linked by -CH2-.

Description

Fluoroelastomer composition, fluororubber molded product, crosslinking agent and compound for producing fluororubber molded product

[0001] The present invention relates to a fluoroelastomer composition, a fluororubber molded article, and a crosslinking agent and compound for producing the fluororubber molded article.

[0002] Fluororubber is usually used after crosslinking. In order to crosslink fluororubber (fluorine-based resin), it is known to compound a crosslinking agent, a crosslinking accelerator, an acid acceptor, etc. with the fluororubber. Examples of crosslinking agents include polyamine crosslinking agents, polyhydroxy compound crosslinking agents, and peroxide crosslinking agents. Among these, crosslinking agents having a phenolic hydroxy group, such as 2,2-bis(4-hydroxyphenyl)-1,1,1,3,3,3-hexafluoropropane (commonly known as bisphenol AF), are often used as polyhydroxy compound crosslinking agents because they provide good physical properties (Patent Document 1).

[0003] JP 2017-165866 A

[0004] One of the properties required for fluororubber is a high crosslinking rate (a short time required to form sufficient crosslinks). However, in the past, attempts to increase the crosslinking rate of fluororubber sometimes resulted in a decrease in the physical properties of the final fluororubber molded product. In other words, it was sometimes difficult to achieve both an increase in the crosslinking rate during the production of a fluororubber molded product and the production of a fluororubber molded product with good physical properties.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fluoroelastomer composition (composition for producing a fluororubber molded article) that has a high crosslinking rate during production of the fluororubber molded article and is capable of giving a fluororubber molded article with good physical properties.

[0006] The present inventors have completed the invention provided below and solved the above problems.

[0007] 1. Fluorine rubber (a) that can be crosslinked with a polyhydroxy compound, and a compound having two aromatic rings each having -CH ２A fluoroelastomer composition comprising: a polyhydroxy compound (b) having a -linked structure and having fluorine atoms; and 2. The fluoroelastomer composition according to 1., wherein the polyhydroxy compound (b) has 4 to 8 fluorine atoms per molecule. 3. The fluoroelastomer composition according to 1. or 2., wherein at least one aromatic ring in the polyhydroxy compound (b) has at least one group selected from the group consisting of a fluoro group and a fluoroalkoxy group. 4. The fluoroelastomer composition according to any one of 1. to 3., wherein the polyhydroxy compound (b) comprises a compound represented by the following general formula (b1): In general formula (b1), when a plurality of Rf's are present, each independently represents at least one group selected from the group consisting of a fluoro group and a fluoroalkoxy group, １represents, when there are a plurality of y1 and y2, each independently represents a monovalent organic group, a nitro group, or a halogeno group, y1 and y2 each independently represent a number from 1 to 4, z1 and z2 each independently represent a number from 0 to 4, and 1≦y1+z1≦4, and 1≦y2+z2≦4. 5. The fluoroelastomer composition according to any one of 1. to 4., wherein the fluororubber (a) is at least one selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride-trifluorochloroethylene binary copolymer, vinylidene fluoride-hexafluoropropylene binary copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, and vinylidene fluoride-tetrafluoroethylene-perfluorovinyl ether terpolymer. 6. 1. to 5. 6. The fluoroelastomer composition according to any one of the above items 1 to 5, further comprising at least one crosslinking accelerator (c) selected from the group consisting of ammonium compounds, phosphonium compounds, oxonium compounds, sulfonium compounds, and amine compounds. 7. A fluororubber molded article obtained by heating the fluoroelastomer composition according to any one of items 1 to 5. 8. A fluororubber molded article obtained by heating the fluoroelastomer composition according to any one of items 1 to 5, wherein two aromatic rings are -CH ２ A crosslinking agent for producing a fluororubber molded article, comprising a polyhydroxy compound having a -linked structure and having fluorine atoms, which is crosslinkable with fluororubber. 9. The crosslinking agent for producing a fluororubber molded article according to item 8., wherein the polyhydroxy compound has 4 to 8 fluorine atoms per molecule. 10. The crosslinking agent for producing a fluororubber molded article according to item 8. or 9., wherein at least one aromatic ring in the polyhydroxy compound has at least one group selected from the group consisting of a fluoro group and a fluoroalkoxy group. 11. The crosslinking agent for producing a fluororubber molded article according to any one of items 8. to 10., wherein the polyhydroxy compound comprises a compound represented by the following general formula (b1): In general formula (b1), when a plurality of Rf's are present, each independently represents at least one group selected from the group consisting of a fluoro group and a fluoroalkoxy group, １ When there are multiple y1 and y2, they each independently represent a monovalent organic group, a nitro group, or a halogeno group, y1 and y2 each independently represent a number from 1 to 4, z1 and z2 each independently represent a number from 0 to 4, and 1≦y1+z1≦4 and 1≦y2+z2≦4. 12. A compound represented by the following general formula (b2): In general formula (b2), R １ When there are multiple y1 and y2, they each independently represent a monovalent organic group, a nitro group, or a halogeno group, y1 and y2 each independently represent a number from 1 to 4, z1 and z2 each independently represent a number from 0 to 4, and 1≦y1+z1≦4 and 1≦y2+z2≦4. 13. A compound represented by the following general formula (b3): In general formula (b3), R １ When there are two or more y1 and y2, they each independently represent a monovalent organic group, a nitro group, or a halogeno group; y1 and y2 each independently represent a number from 1 to 4; z1 and z2 each independently represent a number from 0 to 4; and 1≦y1+z1≦4, and 1≦y2+z2≦4.

[0008] According to the present invention, there is provided a fluoroelastomer composition (composition for producing a fluororubber molded article) which has a high crosslinking rate during production of a fluororubber molded article and which can give a fluororubber molded article with good physical properties.

[0009] Hereinafter, embodiments of the present invention will be described in detail.

[0010] In this specification, unless otherwise specified, the expression "X to Y" in the description of a numerical range means at least X and at most Y. For example, "1 to 5% by mass" means "at least 1% by mass and at most 5% by mass."

[0011] In the description of groups (atomic groups) in this specification, when a notation does not specify whether the group is substituted or unsubstituted, it encompasses both unsubstituted and substituted groups. For example, the term "alkyl group" encompasses not only alkyl groups without a substituent (unsubstituted alkyl groups) but also alkyl groups with a substituent (substituted alkyl groups).

[0012] Unless otherwise specified, the term "organic group" as used herein means an atomic group obtained by removing one or more hydrogen atoms from an organic compound. For example, a "monovalent organic group" refers to an atomic group obtained by removing one hydrogen atom from any organic compound.

[0013] <Fluoroelastomer composition> The fluoroelastomer composition of the present embodiment comprises a fluororubber (a) that can be crosslinked with a polyhydroxy compound, and a fluoroelastomer (b) in which two aromatic rings are —CH ２ and a polyhydroxy compound (b) having a -linked structure and having a fluorine atom.

[0014] The crosslinking rate is high when a fluororubber molded article is produced using the fluoroelastomer composition of this embodiment. The reason for this is not entirely clear, but the present inventors speculate as follows (1) and (2). It should be noted that the present invention is not limited to the speculations described here.

[0015] (1) A —CH group connecting two aromatic rings in the polyhydroxy compound (b) ２ The -linked structure is a structure that is prone to rotational movement due to heat. For this reason, the polyhydroxy compound (b) is, for example, bisphenol AF (two aromatic rings are -C(CF) ３ ) ２ It is believed that the polyhydroxy compound (b) exhibits greater thermal mobility in the composition than the fluororubber (a) (linked with a -). It is presumed that the greater thermal mobility of the polyhydroxy compound (b) promotes the reaction with the fluororubber (a), resulting in a higher crosslinking rate.

[0016] (2) The fact that the polyhydroxy compound (b) has fluorine atoms improves its affinity and compatibility with the fluororubber (a), which is also thought to contribute to the improvement of the crosslinking reaction rate. In conventional bisphenol AF, the linking portion between the two aromatic rings contains a fluorine atom, but in polyhydroxy compound (b), the two aromatic rings are -CH ２ Since the linkage is by -, the linkage does not contain a fluorine atom. ２ It is believed that the presence of a fluorine atom-containing group in a portion other than the - structure (for example, an aromatic ring) improves the affinity and compatibility of the compound as a whole with the fluororubber (a). It is presumed that the good affinity and compatibility between the fluororubber (a) and the polyhydroxy compound (b) makes it easier for the crosslinking reaction between these two components to proceed, increasing the crosslinking rate.

[0017] Furthermore, the polyhydroxy compound (b) has a structure in which two aromatic rings are linked by a linking group, similar to that of conventional crosslinking agents such as bisphenol AF. This is probably due to the fact that the fluororubber molded article produced using the fluoroelastomer composition of this embodiment has good physical properties.

[0018] In other words, by using the fluoroelastomer composition of the present embodiment, it is possible to achieve both (1) an increase in the crosslinking rate during production of a fluororubber molded article and (2) the production of a fluororubber molded article with good physical properties, which have been difficult to achieve in some cases in the past.

[0019] The components contained in the fluoroelastomer composition of this embodiment will be further described below.

[0020] (Fluororubber (a)) The fluororubber (a) is not particularly limited as long as it is crosslinkable with a polyhydroxy compound (specifically, the polyhydroxy compound (b)). The fluoroelastomer composition of the present embodiment may contain only one fluororubber (a) or may contain two or more fluororubbers (a) of the present embodiment.

[0021] Specific examples of the fluororubber (a) include fluororubbers that have fluorine in the molecule, are crosslinkable, and can exhibit rubber elasticity through crosslinking, and are crosslinkable with a polyhydroxy compound. More specific examples of the fluororubber (a) include vinylidene fluoride-based rubbers (FKM) such as polyvinylidene fluoride (PVDF), vinylidene fluoride-trifluorochloroethylene binary copolymer (poly(VDF / CTFE)), vinylidene fluoride-hexafluoropropylene binary copolymer (poly(VDF / HFP)), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer (poly(VDF / HFP / TFE)), and vinylidene fluoride-tetrafluoroethylene-perfluorovinyl ether terpolymer (poly(VDF / TFE / PFVE)), tetrafluoroethylene-propylene-based rubbers (FEPM), and tetrafluoroethylene-perfluorovinyl ether-based rubbers (FFKM). The fluororubber (a) may be used alone, or two or more fluororubbers (a) may be used in any combination.

[0022] Among the fluororubbers (a), vinylidene fluoride rubbers are preferably used because they are excellent in versatility and ease of handling, and also because they can easily give fluororubber molded articles that are excellent in rubber elasticity, abrasion resistance, tensile strength, and the like.

[0023] Generally, fluororubbers are classified into a pre-compound type, which is supplied in a state in which a crosslinking agent such as a polyhydroxy compound has been added in advance, and a raw rubber type, which is supplied in a state of raw rubber without adding a crosslinking agent such as a polyhydroxy compound. In the present embodiment, the raw rubber type is preferably used.

[0024] Specific examples of vinylidene fluoride rubbers include the A, B, F, and AL types of "Viton (registered trademark)" manufactured by DuPont Elastomers Co., Ltd., and the G-700, G-800, and G-550 series of "Dai-El (registered trademark)" manufactured by Daikin Industries, Ltd. Among vinylidene fluoride rubbers, vinylidene fluoride-hexafluoropropylene binary copolymers are preferred. These are commercially available as "A-200" (manufactured by DuPont Elastomers Co., Ltd.), "G-701" (manufactured by Daikin Industries, Ltd.), and "G-801" (manufactured by Daikin Industries, Ltd.), for example.

[0025] (Polyhydroxy Compound (b)) The fluoroelastomer composition of the present embodiment may contain only one polyhydroxy compound (b), or may contain two or more polyhydroxy compounds (b). The polyhydroxy compound (b) usually functions as a crosslinking agent for the fluororubber (a). In other words, the polyhydroxy compound (b) is a compound in which "two aromatic rings are -CH ２ The polyhydroxy compound (b) can also be expressed as a "crosslinking agent for producing a fluororubber molded article, which contains a polyhydroxy compound having a partial structure linked by - and having a fluorine atom, and which is capable of crosslinking with fluororubber." ２ There are no particular limitations on the polyhydroxy compound (b) as long as it has a -linked partial structure, a fluorine atom, and two or more hydroxy groups. The hydroxy groups in the polyhydroxy compound (b) may be alcoholic hydroxy groups or phenolic hydroxy groups.

[0026] From the viewpoints of appropriate affinity with the fluororubber (a) and optimization of properties after crosslinking, the polyhydroxy compound (b) preferably has 4 to 8, more preferably 4 to 6, fluorine atoms per molecule.

[0027] At least one of the aromatic rings in the polyhydroxy compound (or all of the aromatic rings) preferably has at least one group selected from the group consisting of a fluoro group and a fluoroalkoxy group. Examples of the fluoroalkoxy group include n-butoxy, s-butoxy, isobutoxy, t-butoxy, n-propoxy, i-propoxy, ethoxy, and methoxy groups in which some or all of the hydrogen atoms of the alkoxy group have been substituted with fluorine atoms. The fluoroalkoxy group may be a perfluoroalkoxy group. The fluoroalkoxy group is preferably a linear or branched fluoroalkoxy group having 1 to 6 carbon atoms.

[0028] The polyhydroxy compound (b) preferably contains a compound represented by the following general formula (b1): Furthermore, the polyhydroxy compound (b) may essentially consist of a compound represented by the following general formula (b1):

[0029]

[0030] In general formula (b1), when a plurality of Rf's are present, each independently represents at least one group selected from the group consisting of a fluoro group and a fluoroalkoxy group, １ When there are two or more y1 and y2, they each independently represent a monovalent organic group, a nitro group, or a halogeno group; y1 and y2 each independently represent a number from 1 to 4; z1 and z2 each independently represent a number from 0 to 4; and 1≦y1+z1≦4, and 1≦y2+z2≦4.

[0031] Specific examples of the fluoroalkoxy group for Rf are as described above.

[0032] R １Examples of the monovalent organic group include alkyl groups, alkoxy groups, alkenyl groups, alkynyl groups, aryl groups, aryloxy groups, amino groups, cyano groups, and silyl groups. The alkyl group is not limited, but is preferably a linear or branched alkyl group having 1 to 6 carbon atoms. Among these, n-butyl, s-butyl, isobutyl, t-butyl, n-propyl, i-propyl, ethyl, and methyl groups are preferred, with ethyl and methyl being particularly preferred. The alkoxy group is not limited, but is preferably a linear or branched alkoxy group having 1 to 6 carbon atoms. Among these, n-butoxy, s-butoxy, isobutoxy, t-butoxy, n-propoxy, i-propoxy, ethoxy, and methoxy groups are preferred, with ethoxy and methoxy being particularly preferred. The alkenyl group is not limited, but is preferably a linear or branched alkenyl group having 2 to 6 carbon atoms. Of these, vinyl, allyl, and 1-butenyl groups are preferred, with vinyl being particularly preferred. The alkynyl group is not limited, but is preferably a linear or branched alkynyl group having 2 to 6 carbon atoms. Of these, ethynyl and propargyl groups are preferred, with ethynyl being particularly preferred. The aryl group is not limited, but is preferably one having 6 to 12 carbon atoms. Of these, phenyl and naphthyl groups are preferred, with phenyl being particularly preferred. The aryloxy group is not limited, but is preferably one having 6 to 12 carbon atoms. Of these, phenoxy and naphthoxy groups are preferred, with phenoxy being particularly preferred.

[0033] y1 is preferably 1 or 2, more preferably 1. y2 is preferably 1 or 2, more preferably 1. When multiple Rfs are present in general formula (b1), it is preferable that all of the Rfs have the same chemical structure, in terms of ease of compound synthesis and availability. z1 is preferably 0 or 1. z2 is preferably 0 or 1.

[0034] Among the compounds represented by general formula (b1), more preferred compounds are compounds represented by the following general formula (b1-1): The definitions and preferred embodiments of each group and character in general formula (b1-1) are the same as those for general formula (b1).

[0035]

[0036] Among the compounds represented by general formula (b1), more preferred compounds are compounds represented by the following general formula (b2). The definitions and preferred embodiments of each group and character in general formula (b2) are the same as those for general formula (b1). Compounds represented by general formula (b2) are considered to be very useful industrially.

[0037]

[0038] Among the compounds represented by general formula (b1), a particularly preferred compound is a compound represented by the following general formula (b3). The definitions and preferred embodiments of each group and character in general formula (b3) are the same as those for general formula (b1). The compound represented by general formula (b3) is considered to be very useful industrially.

[0039]

[0040] Examples of polyhydroxy compounds that can be preferably used as the polyhydroxy compound (b) are shown below.

[0041]

[0042] (Combined Crosslinking Agent (b')) The fluoroelastomer composition of the present embodiment may further contain a crosslinking agent (combined crosslinking agent (b')) capable of crosslinking the fluororubber (a), other than the polyhydroxy compound (b). Examples of the combined crosslinking agent (b') include known polyhydroxy compounds. In particular, polyhydroxy aromatic compounds are preferably used because of their excellent thermal stability. When a combined crosslinking agent (b') is used, only one combined crosslinking agent (b') may be used, or two or more combined crosslinking agents (b') may be used.

[0043] Examples of polyhydroxy aromatic compounds include 4,4'-dihydroxydiphenylmethane, 2,2-bis(4-hydroxyphenyl)propane, bisphenol AF, 1,3-dihydroxybenzene, 1,7-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxystilbene, 2,6-dihydroxyanthracene, hydroquinone, catechol, 2,2-bis(4-hydroxyphenyl)butane, 2,2-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, and 3,3',5,5'-tetrabromobisphenol A. These may be used alone or in any combination of two or more. Among these, bisphenol AF is preferred because the resulting molded article has excellent thermal stability.

[0044] The total amount of the polyhydroxy compound (b) and the combined crosslinking agent (b') in the fluoroelastomer composition of this embodiment is preferably 0.5 to 15 parts by mass, more preferably 0.5 to 10 parts by mass, and even more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the fluororubber (a), from the viewpoint of balancing steam resistance, thermal stability, and hardness of the rubber molded article. Incidentally, when the combined crosslinking agent (b') is used, from the viewpoint of ensuring a reliable improvement in performance, the amount used is, for example, 1 to 100 parts by mass, preferably 1 to 50 parts by mass, per 100 parts by mass of the polyhydroxy compound (b). Of course, if the desired effect can be obtained, the fluoroelastomer composition of this embodiment does not need to contain the combined crosslinking agent (b').

[0045] (Crosslinking Accelerator (c)) The fluoroelastomer composition of the present embodiment preferably further contains a crosslinking accelerator (c). Examples of the crosslinking accelerator (c) include onium compounds. Specific examples include ammonium compounds such as quaternary ammonium salts, phosphonium compounds such as quaternary phosphonium salts, oxonium compounds, and sulfonium compounds. Other examples include amine compounds. As the crosslinking accelerator, quaternary ammonium salts or quaternary phosphonium salts are particularly preferred. From another perspective, onium halides are also preferred as the crosslinking accelerator. These may be used alone or in combination.

[0046] The quaternary ammonium salt is not particularly limited, and examples thereof include quaternary ammonium halides such as tetramethylammonium chloride, tetraethylammonium chloride, tetrapropylammonium chloride, tetrabutylammonium chloride, tetrabutylammonium bromide, 8-methyl-1,8-diazabicyclo[5,4,0]-7-undecenium chloride, 8-methyl-1,8-diazabicyclo[5,4,0]-7-undecenium bromide, 8-ethyl-1,8-diazabicyclo[5,4,0]-7-undecenium chloride, 8-dodecyl-1,8-diazabicyclo[5,4,0]-7-undecenium chloride, and 8-benzyl-1,8-diazabicyclo[5,4,0]-7-undecenium chloride. In particular, 8-benzyl-1,8-diazabicyclo[5,4,0]-7-undecenium chloride is preferred.

[0047] The quaternary phosphonium salt is not particularly limited, and examples thereof include quaternary phosphonium halides such as tetrabutylphosphonium chloride, tetraoctylphosphonium chloride, tetraphenylphosphonium chloride, benzyltriphenylphosphonium chloride, benzyltriphenylphosphonium bromide, trioctylmethylphosphonium chloride, trioctylbenzylphosphonium chloride, tetravinylphosphonium chloride, and tetraallylphosphonium chloride. Benzyltriphenylphosphonium chloride is particularly preferred.

[0048] Furthermore, a mixture of a polyhydroxy compound (b) and the above-mentioned crosslinking accelerator can also be used as the crosslinking accelerator (c). Examples of the mixture of a polyhydroxy compound (b) and a crosslinking accelerator include a mixed salt of an onium salt, such as the above-mentioned quaternary ammonium salt or quaternary phosphonium salt, with a bisphenol compound. Incidentally, the "mixed salt" here refers to a mixture of the following components (X) and (Y). In the mixed salt, the number of moles of (X) relative to the number of moles of (Y) (molar ratio (X) / (Y)) is preferably 0.05 to 5, more preferably 0.06 to 4, and even more preferably 0.07 to 3. The inclusion of a polyhydroxy compound (b) in which the hydroxy groups are not anionized and are uncharged can sometimes provide desirable effects, such as a further reduction in the melting point of the mixture. (X) A polyhydroxy compound (b) in which the hydroxy groups are not anionized and are uncharged. (Y) A salt of a polyhydroxy compound (b) in which at least a portion of the hydroxy groups are anionized and an onium cation.

[0049] Furthermore, a compound in which hydrogen atoms of the hydroxy groups of the polyhydroxy compound (b) are substituted with cations of the onium compounds shown as the crosslinking accelerators above, i.e., an onium salt of the polyhydroxy compound (b), can also be used as the crosslinking accelerator (c). Specific examples include quaternary ammonium salts such as tetramethylammonium salts, tetraethylammonium salts, tetrapropylammonium salts, tetrabutylammonium salts, 8-methyl-1,8-diazabicyclo[5,4,0]-7-undecenium salts, 8-ethyl-1,8-diazabicyclo[5,4,0]-7-undecenium salts, 8-dodecyl-1,8-diazabicyclo[5,4,0]-7-undecenium salts, and 8-benzyl-1,8-diazabicyclo[5,4,0]-7-undecenium salts of bisphenol compounds; and quaternary phosphonium salts such as tetrabutylphosphonium salts, tetraoctylphosphonium salts, tetraphenylphosphonium salts, benzyltriphenylphosphonium salts, trioctylmethylphosphonium salts, trioctylbenzylphosphonium salts, tetravinylphosphonium salts, and tetraallylphosphonium salts of bisphenol compounds. In particular, a mixed salt of a bisphenol represented by general formula (1) and benzyltriphenylphosphonium chloride, or a benzyltriphenylphosphonium salt of a bisphenol represented by general formula (1) is preferred. That is, at least a portion of the crosslinking accelerator (c) may be a mixed salt of a polyhydroxy compound (b) and an onium salt, or an onium salt of the polyhydroxy compound (b). The onium salt here is preferably a phosphonium salt, and more preferably a benzyltriphenylphosphonium salt. In other words, a mixed salt of a polyhydroxy compound (b) and benzyltriphenylphosphonium chloride, or a benzyltriphenylphosphonium salt of the polyhydroxy compound (b) is preferably used as a crosslinking accelerator for producing a fluororubber molded article.

[0050] Incidentally, by using a mixed salt of the polyhydroxy compound (b) and an onium salt (such as an onium halide) and / or an onium salt of the polyhydroxy compound (b) as at least a part of the crosslinking accelerator (c), it is thought that, for example, it becomes easier to disperse the crosslinking agent and the crosslinking accelerator in a uniform ratio. It is also thought that it becomes easier to suppress the variation in the crosslinking properties within the fluoroelastomer composition. In addition, when forming a salt, depending on the compound, the melting point may be lowered compared to when each compound is used alone, and the reactivity (crosslinking properties) during heating may be improved.

[0051] Regarding the melting point, the melting point of the mixed salt of the polyhydroxy compound (b) and the onium salt, or the melting point of the onium salt of the polyhydroxy compound (b) is preferably 200°C or lower, more preferably 50 to 200°C, and even more preferably 75 to 180°C. For an example of a method for measuring the melting point, see the Examples below. Incidentally, when the melting point has a "range" and cannot be uniquely determined, the melting point is defined as (T2 + T1) / 2, where T1 is the temperature at which melting begins and T2 is the temperature at which melting ends under the measurement conditions of the Examples, and this value preferably falls within the above-mentioned range.

[0052] By including the crosslinking accelerator (c) in the fluoroelastomer of this embodiment, crosslinking efficiency can be improved, and the thermal stability of the resulting rubber molded article can be improved. When the crosslinking accelerator (c) is used, the amount thereof is usually 0.1 to 10 parts by mass, preferably 0.1 to 5 parts by mass, per 100 parts by mass of the fluororubber (a). When the crosslinking accelerator (c) is used, only one crosslinking accelerator (c) may be used, or two or more crosslinking accelerators (c) may be used.

[0053] (Acid Acceptor (d)) The fluoroelastomer composition of the present embodiment may contain an acid acceptor (d). As the acid acceptor (d), a metal oxide such as magnesium oxide or calcium oxide, or a metal hydroxide such as calcium hydroxide can be used. Magnesium oxide and calcium hydroxide are particularly preferred. These may be used alone or in combination. When an acid acceptor is used, the amount thereof is usually 1 to 30 parts by mass, preferably 1 to 15 parts by mass, per 100 parts by mass of the fluororubber (a).

[0054] (Filler (e)) The fluoroelastomer composition of the present embodiment may contain a filler (e). As the filler (e), known fillers that are conventionally compounded in fluororubbers, such as carbon black, talc, clay, silica, potassium carbonate, and barium sulfate, can be used. When the filler (e) is used, the amount thereof is preferably 0 to 150 parts by mass, and more preferably 1 to 100 parts by mass, per 100 parts by mass of the fluororubber (a). When the filler (e) is used, only one filler v may be used, or two or more fillers (e) may be used.

[0055] (Other Components) In addition to the above components, the fluoroelastomer composition of the present embodiment may contain, if necessary, additives known to be compounded in fluororubbers. Examples of additives include processing aids (such as waxes), plasticizers, colorants, stabilizers, tackifiers, release agents, electrical conductivity imparting agents, thermal conductivity imparting agents, surface detackifying agents, flexibility imparting agents, thermal stability improvers, and flame retardants.

[0056] (Method for Producing Fluoroelastomer Composition) The fluoroelastomer composition of the present embodiment can be obtained, for example, by kneading the above-mentioned components using a commonly used rubber kneading device. 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.

[0057] To uniformly disperse each component, for example, the following two-stage kneading may be employed: (i) First, the fluororubber (a), polyhydroxy compound (b), and crosslinking accelerator (c) are kneaded while melting them at a high temperature of 100 to 200°C using a closed-type kneading device such as a kneader. (ii) Then, other components such as the acid acceptor (d), filler (e), and processing aid are kneaded at a low temperature equal to or lower than the temperature used in kneading in (i).

[0058] Furthermore, the dispersibility can be improved by kneading the components, leaving them at room temperature for 12 hours or more, and then kneading them again.

[0059] <Fluororubber Molded Article> A fluororubber molded article can be obtained by heating the above-mentioned fluoroelastomer composition to promote the crosslinking reaction. Known methods and conditions for molding and heating (crosslinking) can be appropriately adopted according to the shape of the molded article to be obtained. The order of molding and heating (crosslinking) is not particularly limited. Molding may be performed after heating (crosslinking), or molding may be performed after heating (crosslinking), or molding and heating (crosslinking) may be performed simultaneously.

[0060] As the molding method, various molding methods such as press molding, extrusion molding, transfer molding, and injection molding can be used. As the heating (crosslinking) method, for example, a method commonly used in the field of conventional fluororubbers, such as heating using a press or a vulcanizing can, can be used. The heating (crosslinking) conditions are usually a temperature of 140 to 250°C and a time of 1 minute to 24 hours. The conditions may be appropriately set depending on the types of polyhydroxy compound (b) and crosslinking accelerator (c), etc.

[0061] Alternatively, heating (crosslinking) may be performed in two stages: primary crosslinking and secondary crosslinking. For example, primary crosslinking may be performed simultaneously with molding by press molding or transfer molding, and then the resin may be demolded and secondary crosslinked using a vulcanizer or the like.

[0062] By the molding and heating (crosslinking) as described above, various products can be produced, such as hoses such as oil tubes, turbocharger hoses, EGR hoses, large computer cooling hoses, fuel hoses, air hoses, PCV hoses, inlet hoses, O-rings for chemical pumps, O-rings for semiconductor manufacturing equipment, intake manifold gaskets, gaskets for computers, gaskets for hydraulic equipment, head gaskets, packing for high-temperature vacuum dryers, sanitary pipe packing, thermos packing, packing for pressure cookers, hard disk packing, oil seals, bearing seals, valve stem seals, fuel sender seals, ventilation seals for liquid-sealed transformers, and chemical pumps. Seals for pumps, flow meters and piping, heat exchanger seals, gas piping seals, hydraulic and lubrication machine seals, dry cleaning equipment seals, automatic packaging machine seals, plate-type heat exchanger seals, solenoid valve seals for vending machines, water heater seals, stern tube seals, rotating shaft seals, firewall seals, and other sealing materials; rolls such as copier rolls, dyeing rolls, solvent rolls, and squeeze rolls for pickling; crankshafts, fuel pump diaphragms, needle tips, fluororubber electric wire, cleaning blades, insulating oil caps for Shinkansen bullet trains, oil well cable jackets, robot cables, coatings for plating jigs, valve seats for butterfly valves, O ２ Molded articles suitable for sensor bushings, pump linings, expansion joints, rubber plates, rods, paints, caulking, binders, etc. can be obtained. Fluororubber molded articles obtained by heating the fluoroelastomer composition of this embodiment have good flexibility. Therefore, the fluoroelastomer composition of this embodiment is preferably used for producing hoses, sealing materials, or rolls.

[0063] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention.

[0064] The embodiments of the present invention will be described in detail based on Examples and Comparative Examples. However, it should be noted that the present invention is not limited to the Examples.

[0065] <Synthesis of Polyhydroxy Compounds> [Synthesis Example 1] TFM-BPF: 4,4'-methylenebis(2-trifluoromethoxyphenol) was synthesized according to the following procedure. 35.6 g (0.2 mol) of 2-trifluoromethoxyphenol, 5.4 g (0.07 mol) of 37% formalin, and 2.53 g (0.01 mol) of p-toluenesulfonic acid were placed in a 200 mL flask equipped with a Dimroth tube and a thermometer, and the mixture was heated to 60°C and stirred for 6 hours. After stirring, 80 g of methyl isobutyl ketone (MIBK) was added to the flask, followed by washing three times with 80 g of water. The organic layer recovered by separation was then concentrated using a rotary evaporator. This yielded 20 g of the target crude TFM-BPF: 4,4'-methylenebis(2-trifluoromethoxyphenol) as a viscous liquid. The obtained crude product was placed in a 100 mL flask and recrystallized with a mixed solvent of 10 g of toluene and 60 g of heptane. The precipitated solid was then filtered off, and the resulting wet product was dried. In this way, 15.1 g of high-purity TFM-BPF was obtained (purity 99.8%, yield 60%). For reference, the above reaction scheme is shown below.

[0066]

[0067] [NMR data] TFM-BPF: 4,4'-methylenebis(2-trifluoromethoxyphenol) １ H-NMR (400MHz, CD ３ CN) δ (ppm): 1.91 (2H, q, 6.4Hz), 3.79 (2H, s), 6.89 (2H, d, J = 8.0Hz), 7.00 (2H, dd, 8.0Hz), 7.06 (2H, s) １９ F-NMR (400MHz) δ (ppm): -58.1 (6F, s)

[0068] <Preparation of Fluoroelastomer Composition> (Example 1) 100 parts by mass of a vinylidene fluoride-based crude rubber-type fluororubber capable of crosslinking with a polyhydroxy compound was placed into a mixing roll at room temperature. 30 parts by mass of carbon black was then added and kneaded until uniform. 6 parts by mass of calcium hydroxide and 3 parts by mass of magnesium oxide were then added, in that order, and kneaded until uniform. 2 parts by mass of the polyhydroxy compound (TFM-BPF) synthesized in Synthesis Example 1 and 0.5 parts by mass of the crosslinking accelerator benzyltriphenylphosphonium chloride (BTPCl) were then added and kneaded. These two components were thoroughly mixed before addition, and the crosslinking accelerator in the composition was a mixed salt of TFM-BPF and benzyltriphenylphosphonium chloride. The mixture was then added to the mixing roll. The mixture was then kneaded until uniform. In this manner, a fluoroelastomer composition was prepared.

[0069] Details of each component used are as follows: Fluorine rubber: trade name "Daiel G-801", manufactured by Daikin Industries, Ltd. Carbon black: trade name "Diablack H", manufactured by Mitsubishi Chemical Corporation Benzyltriphenylphosphonium chloride (BTPCl): manufactured by Tokyo Chemical Industry Co., Ltd. Calcium hydroxide: manufactured by Kanto Chemical Co., Ltd. Magnesium oxide: trade name "Kyowamag 150", manufactured by Kyowa Chemical Industry Co., Ltd.

[0070] Comparative Example 1 A fluoroelastomer composition was prepared in the same manner as in Example 1, except that bisphenol AF was used as the polyhydroxy compound instead of TFM-BPF.

[0071] Comparative Example 2 A fluoroelastomer composition was prepared in the same manner as in Example 1, except that (1,1-bis(4-hydroxyphenyl)-2,2,2-trifluoroethane) (bisphenol EF) was used instead of TFM-BPF as the polyhydroxy compound. For reference, (1,1-bis(4-hydroxyphenyl)-2,2,2-trifluoroethane) (bisphenol EF) was synthesized with reference to the description in Example 5 of WO 2020 / 162408.

[0072] <Evaluation of Crosslinking Properties (Crosslinking Rate) of Fluoroelastomer Composition> The crosslinking properties of the uncured fluoroelastomer composition were measured using a Curelastometer 7 Type P manufactured by JSR Trading Co., Ltd., and the crosslinking rate was evaluated. Specifically, in accordance with JIS K 6300-2 Method A, both the minimum torque (ML) and the flat or maximum torque (MH) obtained after a certain time at 177°C were measured. The time until the torque reached a value equal to ML + 0.1 (MH - ML) and ML + 0.9 (MH - ML), respectively (respectively, "t １０ " and "t ９０ ") was used as an index of crosslinking characteristics (crosslinking rate). The smaller these values, the higher the crosslinking rate (the faster the crosslinking reaction proceeds).

[0073] <Preparation of Fluororubber Molded Articles and Evaluation of Physical Properties> The fluoroelastomer compositions obtained in Example 1, Comparative Example 1, and Comparative Example 2 were each placed in a mold and pressed at 177°C and 10 MPa for 15 minutes to allow the crosslinking reaction to proceed. Sheet-shaped molded articles (length: 150 mm, width: 150 mm, thickness: 2 mm, or length: 100 mm, width: 100 mm, thickness: 4 mm) were obtained. The molded articles were then transferred to an oven and subjected to secondary crosslinking at 232°C for 24 hours.

[0074] The sheet-like molded article was punched out to obtain test pieces, which were then used to evaluate various properties. Specific evaluation methods were as follows.

[0075] (Tensile strength) A test piece in the shape of a No. 5 dumbbell was punched out from a 2 mm thick sheet-like molded product and set in an Instron universal testing machine, Model 5982. The tensile strength and elongation at break were measured in accordance with JIS K 6251-1:2015 under conditions of 23°C and 500 mm / min.

[0076] (Density) Density was measured in accordance with JIS K 7112 Method A using a molded article punched into a disk shape having a thickness of 2 mm and a diameter of 50 mm.

[0077] (Durometer hardness) Three molded bodies punched into a disk shape having a thickness of 2 mm and a diameter of 50 mm were stacked on top of each other, and the hardness was measured in accordance with JIS K 6253-3:2012 using a rubber / plastic hardness meter (durometer) GS-620R-G manufactured by Teclock Corporation.

[0078] (Compression Set) Three molded articles were punched into disks with a thickness of 4 mm and a diameter of 29 mm and stacked together, and the compression set was measured under the conditions of 23°C and 24 hours in accordance with JIS K 6262: 2006. The results were quantified as a percentage of the original compression deformation (assumed to be 10%).

[0079] (Thermal Stability) The 5% weight loss temperature of the molded article was measured using a simultaneous thermogravimetry and differential thermal analyzer STA7200 manufactured by Hitachi High-Tech Science Corp. The measurement conditions were an air atmosphere and a temperature rise rate of 10°C / min.

[0080] Various information is summarized in Table 1. In Table 1, "-" indicates that the corresponding component is not contained in the composition.

[0081]

[0082] From Table 1, it can be seen that the fluoroelastomer composition of Example 1 using TFM-BPF as a crosslinking agent has superior crosslinking properties (higher crosslinking rate and curing in a relatively short time) than the fluoroelastomers of Comparative Example 1 using bisphenol AF or bisphenol EF as crosslinking agents. Specifically, the crosslinking rate is about twice as fast. This means that the fluoroelastomer composition of this embodiment is industrially useful in terms of productivity and handleability.

[0083] Furthermore, with regard to the physical properties of the obtained molded article, the evaluation results of Example 1 showed that flexibility, resistance to breakage, and thermal stability were comparable to those of the comparative examples in which bisphenol AF or bisphenol EF was used as a crosslinking agent. In other words, by using the fluoroelastomer composition of this embodiment, it was possible to achieve both (1) an increased crosslinking rate during the production of a fluororubber molded article and (2) the production of a fluororubber molded article with good physical properties.

[0084] Furthermore, the compression set value was better (smaller) in Example 1 than in Comparative Examples 1 and 2. This means that the fluoroelastomer composition of the present embodiment can be preferably used in applications where sealing properties are required.

[0085] This application claims priority based on Japanese Patent Application No. 2024-012526, filed January 31, 2024, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. Fluorine rubber (a) that can be crosslinked with polyhydroxy compounds and two aromatic rings that are -CH ２ A fluoroelastomer composition comprising: (b) a polyhydroxy compound having a -linked structure and having a fluorine atom; and 2. The fluoroelastomer composition according to claim 1, wherein said polyhydroxy compound (b) has 4 to 8 fluorine atoms per molecule.

3. A fluoroelastomer composition according to claim 1 or 2, wherein at least one of the aromatic rings in said polyhydroxy compound (b) has at least one group selected from the group consisting of a fluoro group and a fluoroalkoxy group.

4. A fluoroelastomer composition according to claim 1 or 2, wherein the polyhydroxy compound (b) comprises a compound represented by the following general formula (b1): In general formula (b1), when a plurality of Rf's are present, each independently represents at least one group selected from the group consisting of a fluoro group and a fluoroalkoxy group, １ When there are two or more y1 and y2, they each independently represent a monovalent organic group, a nitro group, or a halogeno group; y1 and y2 each independently represent a number from 1 to 4; z1 and z2 each independently represent a number from 0 to 4; and 1≦y1+z1≦4, and 1≦y2+z2≦4.

5. The fluoroelastomer composition according to claim 1 or 2, wherein the fluororubber (a) is at least one selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride-trifluorochloroethylene binary copolymer, vinylidene fluoride-hexafluoropropylene binary copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, and vinylidene fluoride-tetrafluoroethylene-perfluorovinyl ether terpolymer.

6. The fluoroelastomer composition according to claim 1 or 2, further comprising at least one crosslinking accelerator (c) selected from the group consisting of ammonium compounds, phosphonium compounds, oxonium compounds, sulfonium compounds and amine compounds.

7. A fluororubber molded article obtained by heating the fluoroelastomer composition according to claim 1 or 2.

8. Two aromatic rings are -CH ２ A crosslinking agent for producing a fluororubber molded article, comprising a polyhydroxy compound having a - bonded structure and containing fluorine atoms, which is crosslinkable with fluororubber.

9. A crosslinking agent for producing fluororubber molded articles according to claim 8, wherein the polyhydroxy compound has 4 to 8 fluorine atoms per molecule.

10. A crosslinking agent for producing fluororubber molded articles according to claim 8 or 9, wherein at least one of the aromatic rings in the polyhydroxy compound has at least one group selected from the group consisting of a fluoro group and a fluoroalkoxy group.

11. A crosslinking agent for producing a fluororubber molded article according to claim 8 or 9, wherein the polyhydroxy compound comprises a compound represented by the following general formula (b1): In general formula (b1), when a plurality of Rf's are present, each independently represents at least one group selected from the group consisting of a fluoro group and a fluoroalkoxy group, １ When there are two or more y1 and y2, they each independently represent a monovalent organic group, a nitro group, or a halogeno group; y1 and y2 each independently represent a number from 1 to 4; z1 and z2 each independently represent a number from 0 to 4; and 1≦y1+z1≦4, and 1≦y2+z2≦4.

12. A compound represented by the following general formula (b2): In general formula (b2), R １ When there are two or more y1 and y2, they each independently represent a monovalent organic group, a nitro group, or a halogeno group; y1 and y2 each independently represent a number from 1 to 4; z1 and z2 each independently represent a number from 0 to 4; and 1≦y1+z1≦4, and 1≦y2+z2≦4.

13. A compound represented by the following general formula (b3): In general formula (b3), R １ When there are two or more y1 and y2, they each independently represent a monovalent organic group, a nitro group, or a halogeno group; y1 and y2 each independently represent a number from 1 to 4; z1 and z2 each independently represent a number from 0 to 4; and 1≦y1+z1≦4, and 1≦y2+z2≦4.

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