sealing material

Abstract

Provided is a sealing material that has excellent crosslinkability of an uncrosslinked rubber composition and that has a small compression set of the crosslinked rubber composition. The sealing material is formed from a rubber composition obtained by crosslinking an uncrosslinked rubber composition. The uncrosslinked rubber composition contains an FKM, a peroxide, an acidic or neutral reinforcing filler, and a basic filler.

Description

[Technical Field]

[0001] The present invention relates to a sealing material. [Background technology]

[0002] A sealing material formed from a rubber composition in which silica is compounded in an FKM is known (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2024-089962 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a sealing material which has excellent crosslinkability of an uncrosslinked rubber composition and which has a small compression set of the crosslinked rubber composition. [Means for solving the problem]

[0005] The present invention provides a sealing material formed from a rubber composition obtained by heating an uncrosslinked rubber composition to crosslink it, the uncrosslinked rubber composition containing an FKM, a peroxide, an acidic or neutral reinforcing filler, and a basic filler. The basic filler contains fumed silica and / or basic wet silica whose surface has been modified with a basic group. . [Effects of the Invention]

[0006] According to the present invention, the uncrosslinked rubber composition before crosslinking of the rubber composition forming the sealing material contains an FKM, a peroxide, an acidic or neutral reinforcing filler, and a basic filler, thereby making it possible to obtain excellent crosslinkability of the uncrosslinked rubber composition and to reduce the compression set of the rubber composition after crosslinking that forms the sealing material. DETAILED DESCRIPTION OF THE INVENTION

[0007] The embodiments will be described in detail below.

[0008] The sealing material according to the embodiment is formed from a rubber composition X obtained by heating and crosslinking an uncrosslinked rubber composition X'. The uncrosslinked rubber composition X' contains an FKM, a peroxide, an acidic or neutral reinforcing filler, and a basic filler.

[0009] According to the sealing material of the embodiment, the uncrosslinked rubber composition X' before crosslinking of the rubber composition X that forms it contains an FKM, a peroxide, an acidic or neutral reinforcing filler, and a basic filler, thereby making it possible to obtain excellent crosslinkability of the uncrosslinked rubber composition X' and to reduce the compression set CS of the rubber composition X that forms the sealing material after crosslinking.

[0010] In this application, "FKM" refers to a copolymer containing one or more of vinylidene fluoride (VdF), hexafluoropropylene (HFP), tetrafluoroethylene (TFE), and perfluoromethyl vinyl ether (PMVE) as monomers. Examples of FKM include a binary FKM of vinylidene fluoride (VdF)-hexafluoropropylene (HFP) binary copolymer, a ternary FKM of vinylidene fluoride (VdF)-hexafluoropropylene (HFP)-tetrafluoroethylene (TFE) terpolymer, and a quaternary FKM of 4-bromo-3,3,4,4-tetrafluoro-1-butene-ethylene (E), tetrafluoroethylene (TFE), and perfluoromethyl vinyl ether (PMVE) tetrapolymer. The FKM preferably contains one or more of a binary FKM, a ternary FKM, and a quaternary FKM, and more preferably contains a binary FKM from the viewpoints of obtaining excellent crosslinkability of the uncrosslinked rubber composition X' and reducing the compression set CS of the crosslinked rubber composition X that forms the sealing material.

[0011] Examples of peroxides include dialkyl peroxides, peroxyketals, and peroxyesters. Examples of dialkyl peroxides include dicumyl peroxide, 1,3-di(t-butylperoxy)diisopropylbenzene, 1,4-di(t-butylperoxy)diisopropylbenzene, t-butylcumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane-3. Examples of peroxyketals include 1,1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-butylperoxy)cyclohexane, and n-butyl-4,4-di(t-butylperoxy)valerate. Examples of peroxyesters include 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-hexylperoxybenzoate, and t-butylperoxybenzoate. The peroxide preferably contains one or more of these, and from the viewpoint of obtaining excellent crosslinkability of the uncrosslinked rubber composition X' and reducing the compression set CS of the crosslinked rubber composition X that forms the sealing material, it is more preferable that the peroxide contains a dialkyl peroxide and / or a peroxy ester, and it is even more preferable that the peroxide contains 2,5-dimethyl-2,5-di(t-butylperoxy)hexane and / or t-butylperoxybenzoate.

[0012] The content A of peroxide in the uncrosslinked rubber composition X' is preferably 0.5 parts by mass or more and 3 parts by mass or less, more preferably 1 part by mass or more and 2 parts by mass or less, relative to 100 parts by mass of FKM, from the viewpoint of obtaining excellent crosslinkability of the uncrosslinked rubber composition X' and reducing the compression set CS of the crosslinked rubber composition X that forms the sealing material.

[0013] The reinforcing filler is acidic or neutral. "Acidic or neutral" means that the pH of a dispersion of the reinforcing filler dispersed in water is 7 or less. Examples of reinforcing fillers include acidic or neutral fumed silica, acidic or neutral carbon black, and acidic or neutral resin powder. Examples of acidic or neutral fumed silica include untreated hydrophilic fumed silica, hydrophobic fumed silica surface-treated with dimethyldichlorosilane, hydrophobic fumed silica surface-modified with trimethylsilyl groups, hydrophobic fumed silica surface-treated with octylsilane, and hydrophobic fumed silica surface-treated with dimethylsilicone oil. The reinforcing filler preferably contains one or more of these, and from the viewpoint of obtaining excellent crosslinkability of the uncrosslinked rubber composition X' and reducing the compression set CS of the crosslinked rubber composition X that forms the sealing material, it is more preferable to contain acidic or neutral fumed silica, and even more preferable to contain hydrophobic fumed silica that has been surface-treated with dimethyldichlorosilane. The average particle diameter of the reinforcing filler is, for example, 10 μm or more and 20 μm or less. In the case of acidic or neutral fumed silica, its specific surface area by the BET method is, for example, 70 m 2 / g or more 150m 2 / g.

[0014] The content B of the reinforcing filler in the uncrosslinked rubber composition X' is preferably 3 parts by mass or more and 25 parts by mass or less, more preferably 5 parts by mass or more and 15 parts by mass or less, and even more preferably 10 parts by mass or more and 12 parts by mass or less, relative to 100 parts by mass of FKM, from the viewpoint of obtaining excellent crosslinkability of the uncrosslinked rubber composition X' and reducing the compression set CS of the crosslinked rubber composition X that forms the sealing material.

[0015] The basic filler is basic. The term "basic" means that the pH of a dispersion of the basic filler in water is greater than 7. Examples of basic fillers include hydrophobic fumed silica, basic wet silica, basic phenolic resin powder, metal oxide powder, and powdery metal hydroxide, all surface-modified with a basic group such as an amino group. The basic filler preferably contains one or more of these. From the viewpoints of achieving excellent crosslinkability of the uncrosslinked rubber composition X' and reducing the compression set CS of the crosslinked rubber composition X that forms the sealing material, it is more preferable to contain hydrophobic fumed silica and / or basic wet silica surface-modified with a basic group. The average particle diameter of the basic filler is, for example, 5 μm or more and 15 μm or less. In the case of hydrophobic fumed silica or basic wet silica surface-modified with a basic group, its specific surface area measured by the BET method is, for example, 100 m 2 / g or more 200m 2 / g or less.

[0016] The content C of the basic filler in the uncrosslinked rubber composition X' is preferably 0.1 parts by mass or more and 3 parts by mass or less, more preferably 0.3 parts by mass or more and 1.5 parts by mass or less, and even more preferably 0.5 parts by mass or more and 1 part by mass or less, per 100 parts by mass of FKM, from the viewpoint of obtaining excellent crosslinkability of the uncrosslinked rubber composition X' and reducing the compression set CS of the crosslinked rubber composition X that forms the sealing material.

[0017] The content B of the reinforcing filler in the uncrosslinked rubber composition X' is preferably greater than the content C of the basic filler, from the viewpoints of obtaining excellent crosslinkability of the uncrosslinked rubber composition X' and reducing the compression set CS of the crosslinked rubber composition X that forms the sealing material. From the same viewpoint, the mass ratio of the content B of the reinforcing filler to the content C of the basic filler in the uncrosslinked rubber composition X' is preferably 4 or more and 50 or less, more preferably 5 or more and 40 or less, and even more preferably 10 or more and 25 or less.

[0018] The sum of the content B of the reinforcing filler and the content C of the basic filler in the uncrosslinked rubber composition X' is preferably 3 parts by mass or more and 30 parts by mass or less, more preferably 5 parts by mass or more and 20 parts by mass or less, and even more preferably 10 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of FKM, from the viewpoint of obtaining excellent crosslinkability of the uncrosslinked rubber composition X' and reducing the compression set CS of the crosslinked rubber composition X that forms the sealing material.

[0019] The uncrosslinked rubber composition X' may further contain a crosslinking aid. Examples of the crosslinking aid include triallyl cyanurate, trimethallyl isocyanurate, triallyl isocyanurate, triacryl formal, 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), and the like. Examples of suitable crosslinking aids include methyltrimethylsiloxane, ...

[0020] The content D of the cross-linking aid in the uncross-linked rubber composition is preferably 1 part by mass or more and 10 parts by mass or less, more preferably 3 parts by mass or more and 5 parts by mass or less, relative to 100 parts by mass of FKM, from the viewpoint of obtaining excellent cross-linkability of the uncross-linked rubber composition X' and reducing the compression set CS of the cross-linked rubber composition X that forms the sealing material.

[0021] The uncrosslinked rubber composition X' may further contain rubber components other than FKM, plasticizers, processing aids, vulcanization accelerators, antioxidants, surfactants, and the like.

[0022] In accordance with JIS K6300-2:2001, the time from the start of vulcanization to the time when 90% of the maximum torque is obtained is determined from a vulcanization curve obtained by using a torsional vibration type flat die vulcanization tester (e.g., Curastometer (registered trademark) manufactured by ENEOS Material Trading Co., Ltd.) based on the uncrosslinked rubber composition X' in die vulcanization test method A, with the heating temperature (primary crosslinking temperature) of the uncrosslinked rubber composition X' as the test temperature. From the viewpoint of obtaining excellent crosslinkability of the uncrosslinked rubber composition X', the time (t90) from the start of vulcanization to the time when 90% of the maximum torque is obtained is preferably 7 minutes or less, more preferably 5 minutes or less, and even more preferably 3 minutes or less.

[0023] The sealing material according to the embodiment can be produced by molding the uncrosslinked rubber composition X′ into a sealing material shape and heating it to crosslink it, thereby obtaining the rubber composition X.

[0024] Specifically, first, an uncrosslinked rubber composition X' is prepared by kneading using an open-type rubber kneader such as an open roll or a closed-type rubber kneader such as a kneader. Next, a predetermined amount of the uncrosslinked rubber composition X' is filled into a cavity of a preheated mold shaped like a sealing material, and the mold is closed. In this state, the composition is heated and maintained at a predetermined temperature and pressure for a predetermined time, thereby causing primary crosslinking. This primary crosslinking may be performed by press molding or injection molding. The primary crosslinking temperature is, for example, 150°C or higher and 180°C or lower. The primary crosslinking pressure is, for example, 0.1 MPa or higher and 25 MPa or lower. The primary crosslinking time is, for example, 3 minutes or higher and 20 minutes or lower. The mold is then opened, and the sealing material formed from the rubber composition X crosslinked with the uncrosslinked rubber composition X' is demolded and removed from the inside.

[0025] Alternatively, the sealing material of the molded article removed from the mold may be placed in a preheated oven and heated at a predetermined temperature for a predetermined time to cause secondary crosslinking. The secondary crosslinking temperature is higher than the primary crosslinking temperature, for example, 190°C or higher and 210°C or lower. The secondary crosslinking time is longer than the primary crosslinking time, for example, 3 hours or higher and 5 hours or lower.

[0026] The sealing material after the primary crosslinking or the secondary crosslinking may be irradiated with radiation to perform post-crosslinking. In this case, examples of the radiation include α-rays, β-rays, γ-rays, electron beams, ions, etc. Of these, electron beams or γ-rays are preferred as the radiation. The radiation dose is, for example, 20 kGy or more and 100 kGy or less.

[0027] The hardness HA of the rubber composition X forming the sealing material according to the embodiment is preferably A65 or more and A75 or less, more preferably A68 or more and A72 or less, as measured by a type A durometer in accordance with JIS K6253-3:2012.

[0028] The tensile strength at break Tb of the rubber composition X is preferably 15 MPa or more, more preferably 25 MPa or more. The elongation at break Eb is preferably 400% or more, more preferably 500% or more. The 100% modulus S100 (tensile stress at 100% elongation) is preferably 1.5 MPa or more and 3 MPa or less, more preferably 2 MPa or more and 2.5 MPa or less. The tensile strength at break Tb, elongation at break Eb, and 100% modulus S100 are measured by a tensile test based on JIS K6251:2023.

[0029] The compression set CS of the rubber composition X is preferably 30% or less, more preferably 20% or less, and even more preferably 15% or less, as measured in accordance with JIS K6262:2013 at a test time of 72 hours and a test temperature of 200°C.

[0030] The sealing material according to the embodiment preferably has a surface color tone that is not black, such as beige, brown, or dark brown. [Example]

[0031] (Uncrosslinked rubber composition) The crosslinked rubber compositions of the following Examples and Comparative Examples were prepared, the respective constitutions of which are also shown in Tables 1 to 5.

[0032] <Example 1-1> The mixture was 100 parts by mass of binary FKM (Dai-el® G801, manufactured by Daikin Corporation) with 1.5 parts by mass of peroxide 1, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (Perhexa® 25B, manufactured by NOF Corporation), and a reinforcing filler, hydrophobic fumed silica surface-treated with dimethyldichlorosilane (Aerosil® R972, manufactured by Nippon Aerosil Co., Ltd., specific surface area by BET method: 90 to 130 m). 2 / g, average particle size (primary): 16 μm) 11.7 parts by mass, basic filler 1 wet silica (Carplex (registered trademark) #1120 manufactured by DSL Japan Co., Ltd., specific surface area by BET method: 120 m 20.3 parts by mass of 1 / g of cellulose acetate copolymer (average particle size (primary): 12 μm) and 4 parts by mass of triallyl isocyanurate (TAIC (registered trademark) manufactured by Mitsubishi Chemical Corporation) as a crosslinking aid were blended and kneaded to prepare an uncrosslinked rubber composition, which was designated Example 1-1.

[0033] <Examples 1-2 to 1-4 and Comparative Example 1> An uncrosslinked rubber composition was prepared in the same manner as in Example 1-1, except that the amounts of the reinforcing filler and basic filler 1 were 11.5 parts by mass and 0.5 parts by mass, respectively, per 100 parts by mass of binary FKM, and this was designated Example 1-2.

[0034] An uncrosslinked rubber composition was prepared in the same manner as in Example 1-1, except that the amounts of the reinforcing filler and basic filler 1 were 11.3 parts by mass and 0.7 parts by mass, respectively, per 100 parts by mass of binary FKM, and this was designated Example 1-3.

[0035] An uncrosslinked rubber composition was prepared in the same manner as in Example 1-1, except that the amounts of the reinforcing filler and basic filler 1 were 11.0 parts by mass and 1.0 part by mass, respectively, per 100 parts by mass of binary FKM, and this was designated Example 1-4.

[0036] An uncrosslinked rubber composition was prepared in the same manner as in Example 1-1, except that basic filler 1 was not compounded and the amount of reinforcing filler compounded was 12.0 parts by mass relative to 100 parts by mass of binary FKM, and this was designated Comparative Example 1.

[0037] [Table 1]

[0038] <Examples 2-1 to 2-5 and Comparative Example 2> Instead of basic filler 1, basic filler 2 was replaced with hydrophobic fumed silica surface-modified with amino groups and trimethylsilyl groups (Aerosil (registered trademark) R504, manufactured by Nippon Aerosil Co., Ltd., specific surface area measured by BET method: 125 to 175 m). 2An uncrosslinked rubber composition was prepared in the same manner as in Example 1-1, except that the amounts of the reinforcing filler and the basic filler 2 were 11.5 parts by mass and 0.5 parts by mass, respectively, per 100 parts by mass of the binary FKM, and this was designated Example 2-1.

[0039] An uncrosslinked rubber composition was prepared in the same manner as in Example 2-1, except that the amounts of the reinforcing filler and basic filler 2 were 11.0 parts by mass and 1.0 part by mass, respectively, per 100 parts by mass of binary FKM, and this was designated Example 2-2.

[0040] An uncrosslinked rubber composition was prepared in the same manner as in Example 2-1, except that the amounts of the reinforcing filler and basic filler 2 were 10.5 parts by mass and 1.5 parts by mass, respectively, per 100 parts by mass of binary FKM, and this was designated Example 2-3.

[0041] An uncrosslinked rubber composition was prepared in the same manner as in Example 2-2, except that peroxide 1 was replaced with peroxide 2, t-butyl peroxybenzoate (Perbutyl (registered trademark) Z, manufactured by NOF Corporation), in an amount of 1 part by mass per 100 parts by mass of the binary FKM, and this was designated Example 2-4.

[0042] An uncrosslinked rubber composition was prepared in the same manner as in Example 2-3, except that Peroxide 2 was used instead of Peroxide 1 and its compounding amount was 1 part by mass per 100 parts by mass of binary FKM, and this was designated Example 2-5.

[0043] An uncrosslinked rubber composition was prepared in the same manner as in Example 2-1, except that no reinforcing filler was added and the amount of basic filler 2 added was 10.0 parts by mass relative to 100 parts by mass of binary FKM, and this was designated Comparative Example 2-1.

[0044] [Table 2]

[0045] <Examples 3-1 to 3-3> An uncrosslinked rubber composition was prepared in the same manner as in Example 1-1, except that basic filler 1 was replaced with basic phenolic resin powder (Bellpearl (registered trademark) R200, manufactured by Air Water Performance Chemicals, average particle size: 6 μm) of basic filler 3, and the compounding amounts of the reinforcing filler and basic filler 3 were 11.5 parts by mass and 0.5 parts by mass, respectively, per 100 parts by mass of binary FKM. This was designated Example 3-1.

[0046] An uncrosslinked rubber composition was prepared in the same manner as in Example 3-1, except that the amounts of the reinforcing filler and basic filler 3 were 11.0 parts by mass and 1.0 part by mass, respectively, per 100 parts by mass of binary FKM, and this was designated Example 3-2.

[0047] An uncrosslinked rubber composition was prepared in the same manner as in Example 3-1, except that the amounts of the reinforcing filler and basic filler 3 were 10.5 parts by mass and 1.5 parts by mass, respectively, per 100 parts by mass of binary FKM, and this was designated Example 3-3.

[0048] [Table 3]

[0049] <Examples 4-1 to 4-4 and Comparative Examples 4-1 to 4-2> An uncrosslinked rubber composition was prepared in the same manner as in Example 2-1, except that a ternary FKM (Solvay (registered trademark) PX989S manufactured by Nippon Solvay K.K.) was used instead of the binary FKM, and the compounding amounts of the reinforcing filler and basic filler 2 were 9.0 parts by mass and 1.0 part by mass, respectively, per 100 parts by mass of the ternary FKM, and this was designated Example 4-1.

[0050] An uncrosslinked rubber composition was prepared in the same manner as in Example 4-1, except that the amounts of the reinforcing filler and basic filler 2 were 8.5 parts by mass and 1.5 parts by mass, respectively, per 100 parts by mass of the ternary FKM, and this was designated Example 4-2.

[0051] An uncrosslinked rubber composition was prepared in the same manner as in Example 4-1, except that Peroxide 2 was used instead of Peroxide 1 and its compounding amount was 1 part by mass per 100 parts by mass of ternary FKM, and this was designated Example 4-3.

[0052] An uncrosslinked rubber composition was prepared in the same manner as in Example 4-2, except that Peroxide 2 was used instead of Peroxide 1 and its compounding amount was 1 part by mass per 100 parts by mass of ternary FKM, and this was designated Example 4-4.

[0053] An uncrosslinked rubber composition was prepared in the same manner as in Example 4-1, except that basic filler 2 was not compounded and the amount of reinforcing filler compounded was 10.0 parts by mass per 100 parts by mass of ternary FKM, and this was designated Comparative Example 4-1.

[0054] An uncrosslinked rubber composition was prepared in the same manner as in Example 4-3, except that basic filler 2 was not compounded and the amount of reinforcing filler compounded was 10.0 parts by mass per 100 parts by mass of ternary FKM, and this was designated Comparative Example 4-2.

[0055] [Table 4]

[0056] <Examples 5-1 to 5-2 and Comparative Example 5> An uncrosslinked rubber composition was prepared in the same manner as in Example 2-4, except that a quaternary FKM (Viton (registered trademark) VTR9213, manufactured by Chemours) was used instead of the binary FKM, and the compounding amounts of the reinforcing filler and basic filler 2 were 8.5 parts by mass and 1.5 parts by mass, respectively, per 100 parts by mass of the quaternary FKM. This was designated Example 5-1.

[0057] An uncrosslinked rubber composition was prepared in the same manner as in Example 5-1, except that the amounts of the reinforcing filler and basic filler 2 were 8.0 parts by mass and 2.0 parts by mass, respectively, per 100 parts by mass of the quaternary FKM, and this was designated Example 5-2.

[0058] An uncrosslinked rubber composition was prepared in the same manner as in Example 5-1, except that basic filler 2 was not compounded and the amount of reinforcing filler compounded was 10.0 parts by mass per 100 parts by mass of the quaternary FKM, and this was designated Comparative Example 5.

[0059] [Table 5]

[0060] (Rubber sheets for test specimens and test specimens for compression set tests) Each of the uncrosslinked rubber compositions of the above Examples and Comparative Examples was placed in a mold for molding rubber sheets, which was then placed in a press molding machine and heated and pressurized to cause primary crosslinking. The primary crosslinking temperature was 165°C for the case using Peroxide 1 and 155°C for the case using Peroxide 2. The primary crosslinking time was 10 minutes. The primary crosslinked product was then removed from the mold and placed in an oven where it was heated at 200°C for 4 hours to cause secondary crosslinking, thereby producing a rubber sheet for a test specimen. Test specimens for compression set tests were also prepared in the same manner.

[0061] (Test method and results) The following tests were carried out on the uncrosslinked rubber compositions of the above Examples and Comparative Examples, and the rubber sheets for test specimens and test specimens for compression set tests prepared by crosslinking the uncrosslinked rubber compositions. The test results are shown in Tables 1 to 5. In Comparative Example 4-1, crosslinking of the uncrosslinked rubber composition did not progress, and a crosslinked rubber composition could not be obtained.

[0062] <t90> For each of the uncrosslinked rubber compositions of the above Examples and Comparative Examples, the time from the start of vulcanization until 90% of the maximum torque was obtained (t90) was determined from the vulcanization curve obtained by die vulcanization test method A using a torsional vibration type flat die vulcanization tester (Curelastometer®, manufactured by ENEOS Material Trading Co., Ltd.) based on JIS K6300-2: 2001. The test temperature was 165°C for the case using Peroxide 1 and 155°C for the case using Peroxide 2.

[0063] <Hardness> The rubber sheets for test specimens prepared by crosslinking each of the uncrosslinked rubber compositions of the above Examples and Comparative Examples were stacked to form test specimens, and the hardness was measured using a Type A durometer in accordance with JIS K6253-3:2012.

[0064] <density> Test specimens were cut out from the rubber sheets for test specimens prepared by crosslinking each of the uncrosslinked rubber compositions of the above Examples and Comparative Examples, and the density was measured in accordance with JIS K6268:1998.

[0065] <Tensile properties> Test specimens were cut out from the rubber sheets for test specimens prepared by crosslinking each of the uncrosslinked rubber compositions of the above Examples and Comparative Examples, and the tensile strength at break Tb, elongation at break Eb, and 100% modulus S100 (tensile stress at 100% elongation) were measured in accordance with JIS K6251:2023.

[0066] <Compression set> The compression set CS of the test specimens for compression set test prepared by crosslinking each of the uncrosslinked rubber compositions of the above Examples and Comparative Examples was measured for a test time of 72 hours at a test temperature of 200°C in accordance with JIS K6262:2013.

[0067] <Surface color tone> The surface color tone of the rubber sheets for test specimens prepared by crosslinking each of the uncrosslinked rubber compositions of Examples 1-1 to 1-4 and Comparative Example 1, Examples 2-1 to 2-3 and Comparative Example 2, and Examples 3-1 to 3-3 was evaluated visually. [Industrial Applicability]

[0068] The present invention is useful in the technical field of sealing materials.

Claims

1. A sealing material formed from a rubber composition obtained by heating an uncrosslinked rubber composition to crosslink it, The uncrosslinked rubber composition contains FKM, a peroxide, an acidic or neutral reinforcing filler, and a basic filler, The sealing material, wherein the basic filler comprises fumed silica and / or basic wet silica whose surface has been modified with a basic group.

2. The sealing material according to claim 1, The sealing material wherein the FKM comprises a binary FKM.

3. The sealing material according to claim 1, The sealing material, wherein the peroxide contains 2,5-dimethyl-2,5-di(t-butylperoxy)hexane and / or t-butylperoxybenzoate.

4. The sealing material according to claim 1, A sealing material in which the reinforcing filler comprises acidic to neutral fumed silica.

5. The sealing material according to claim 1, The sealing material, wherein the content of the basic filler in the uncrosslinked rubber composition is 3 parts by mass or less per 100 parts by mass of the FKM.

6. The sealing material according to claim 1, A sealing material in which the time from the start of vulcanization to the attainment of 90% of the maximum torque, as determined from a vulcanization curve obtained by die vulcanization test method A based on JIS K6300-2:2001 for the uncrosslinked rubber composition using the heating temperature of the uncrosslinked rubber composition as the test temperature, is 7 minutes or less.

7. The sealing material according to claim 1, The sealing material has a hardness of the rubber composition measured with a type A durometer in accordance with JIS K6253-3:2012 of A65 or more and A75 or less.

8. The sealing material according to claim 1, The rubber composition has a compression set of 30% or less as measured in accordance with JIS K6262:2013 at a test time of 72 hours and a test temperature of 200°C.

9. The sealing material according to claim 1, The sealing material has a surface color tone that is not black.

10. The sealing material according to claim 4, The sealing material, wherein the reinforcing filler comprises one or more of surface-untreated hydrophilic fumed silica, hydrophobic fumed silica surface-treated with dimethyldichlorosilane, hydrophobic fumed silica surface-modified with trimethylsilyl groups, hydrophobic fumed silica surface-treated with octylsilane, and hydrophobic fumed silica surface-treated with dimethylsilicone oil.

11. The sealing material according to claim 1, The sealing material, wherein the content of the reinforcing filler in the uncrosslinked rubber composition is 3 parts by mass or more and 25 parts by mass or less per 100 parts by mass of the FKM.

12. The sealing material according to claim 1, The sealing material, wherein the content of the reinforcing filler in the uncrosslinked rubber composition is greater than the content of the basic filler.

13. The sealing material according to claim 12, The sealing material, wherein the mass ratio of the content of the reinforcing filler to the content of the basic filler in the uncrosslinked rubber composition is 4 or more and 50 or less.

14. The sealing material according to claim 1, The sealing material, wherein the sum of the content of the reinforcing filler and the content of the basic filler in the uncrosslinked rubber composition is 3 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the FKM.

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