Peroxide-crosslinked fluororubber composition, rubber molded article, and fluororubber cured product

Abstract

This peroxide-crosslinked fluororubber composition includes: (a) a peroxide-crosslinked fluoropolymer; and (b) a reinforcing filler that is surface-treated with a surface treatment agent which is a silane coupling agent having an aliphatic hydrocarbon group with 3-40 carbon atoms. The peroxide-crosslinked fluororubber composition provides a cured product having excellent compression set resistance and rubber physical properties.

Description

Peroxide crosslinked fluororubber composition, rubber molded articles, and cured fluororubber products

[0001] The present invention relates to a peroxide crosslinked fluororubber composition that provides a cured product having excellent compression set resistance (exhibiting low compression set), a rubber molded article obtained by curing the composition, and a cured fluororubber product.

[0002] Patent Document 1 (Japanese Patent Application Publication No. 2000-7835) discloses a perfluoropolyether-based fluororubber composition that yields a cured product with excellent heat resistance, chemical resistance, solvent resistance, and low-temperature properties. However, there was room for improvement in the compression set resistance of the cured product.

[0003] Japanese Patent Publication No. 2000-7835

[0004] The present invention has been made in view of the above circumstances, and aims to provide a peroxide crosslinked fluororubber composition that provides a cured product with excellent heat resistance, chemical resistance, solvent resistance, low-temperature properties, and other characteristics, and further provides a cured product with even better compression set resistance, as well as a rubber molded article and a cured fluororubber product obtained by curing the composition.

[0005] As a result of diligent research to achieve the above objective, the present inventors have found that a peroxide-crosslinked fluororubber composition comprising (a) a peroxide-crosslinked fluoropolymer and (b) a reinforcing filler surface-treated with a surface treatment agent, wherein the surface treatment agent is a silane coupling agent having aliphatic hydrocarbon groups with 3 to 40 carbon atoms, yields a cured product with excellent compression set resistance and rubber properties, thus leading to the present invention.

[0006] Accordingly, the present invention provides the following peroxide-crosslinked fluororubber compositions, rubber molded articles, and cured fluororubber products. [1] A peroxide-crosslinked fluororubber composition comprising (a) a peroxide-crosslinked fluoropolymer and (b) a reinforcing filler surface-treated with a surface treatment agent, wherein the surface treatment agent is a silane coupling agent having aliphatic hydrocarbon groups having 3 to 40 carbon atoms. [2] The peroxide-crosslinked fluororubber composition according to [1], wherein component (a) is a perfluoropolyether-based fluoropolymer. [3] The peroxide-crosslinked fluororubber composition according to [2], wherein the perfluoropolyether-based fluoropolymer is an addition reaction product of a perfluoro compound (I) having at least two alkenyl groups in the molecule and a perfluoroalkylene group or a divalent perfluoropolyether group in the main chain and an organosilicon compound (II) having at least two SiH groups in the molecule. [4] Component (I) is the following general formula (2) Rf[-U-Z(-Y-X) β ]2 (2) A peroxide crosslinked fluororubber composition according to [3], wherein Rf in formula (2) is a perfluoroalkylene group or a divalent perfluoropolyether group, U is independently a single bond, a carbonyl bond, or a divalent organic group, Z is independently a single bond, a nitrogen atom, a silicon atom, a carbon atom, a phosphorus atom, or a 3- to 8-valent organic group, Y is independently a single bond or a divalent organic group, X is independently an alkenyl group, and β is an integer from 1 to 7. However, U and Z cannot be single bonds at the same time. [5] The peroxide crosslinked fluororubber composition according to [3], wherein Rf in formula (2) above is -C a F 2a The peroxide crosslinked fluororubber composition according to [4], comprising one or more repeating units (perfluorooxyalkylene units) represented by O- (wherein a is an integer from 1 to 6). [6] The above component (II) comprises the following general formula (3) (In the formula, R 4is an unsubstituted or substituted monovalent hydrocarbon group that independently does not contain an aliphatic unsaturated bond. W is a divalent organic group.) The peroxide crosslinked fluororubber composition according to any one of [3] to [5]. [7] In the above formula (3), W is the formula (i) or (ii) [In the formula, R 5 is independently an oxygen atom, or an unsubstituted or substituted divalent hydrocarbon group, and R 6 is independently an unsubstituted or substituted monovalent hydrocarbon group, Rf” is a perfluoroalkylene group or a divalent perfluoropolyether group, and R 7 is an unsubstituted or substituted monovalent hydrocarbon group, or a dimethylsiloxy group, D is independently -CH2-, -CH2O-, -CH2OCH2-, -E-NR 8 SO2- or -E-NR 8 -CO- (where E is -CH2- or the group represented by the following formula (In the formula, Me is a methyl group.) and R 8 is a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group.) and z is independently 0 or 1. ] The peroxide crosslinked fluororubber composition according to [6]. [8] In the above component (b), the surface treatment agent is a silane coupling agent having an aliphatic hydrocarbon group with 4 to 20 carbon atoms, the peroxide crosslinked fluororubber composition according to any one of [1] to [7]. [9] In the above component (b), the surface treatment agent is the following formula (1-1) R 4-m SiX 1 m (1-1) (In the formula, m is 1 to 3, R is an alkyl group having 3 to 40 carbon atoms, and X 1A peroxide crosslinked fluororubber composition according to any one of [1] to [7], wherein is a hydrolyzable group.

[10] A peroxide crosslinked fluororubber composition according to any one of [1] to [9], which is a kneaded product of the above components (a) and (b).

[11] A peroxide crosslinked fluororubber composition according to any one of [1] to

[10] , wherein the Mooney viscosity (ML(1+4)) (100°C) is 5 or more.

[12] A peroxide crosslinked fluororubber composition according to any one of [1] to

[11] , further containing a peroxide crosslinking agent.

[13] A rubber molded article obtained by curing the peroxide crosslinked fluororubber composition according to any one of [1] to

[12] .

[14] A cured fluororubber product obtained by curing a peroxide crosslinked fluororubber composition described in any of [1] to

[12] , conforming to JIS K 6262:2013, having a compressibility of 25% and a compression set of 40% or less after compression at 200°C for 70 hours.

[0007] According to the present invention, it is possible to provide a peroxide crosslinked fluororubber composition that yields a cured product having excellent resistance to compression set (exhibiting low compression set, particularly low high-temperature compression set).

[0008] The present invention will be described in detail below. The peroxide crosslinked fluororubber composition of the present invention comprises the following components (a) and (b): (a) a peroxide crosslinked fluoropolymer, and (b) a reinforcing filler surface-treated with a surface treatment agent, wherein the surface treatment agent is a silane coupling agent having aliphatic hydrocarbon groups having 3 to 40 carbon atoms.

[0009] [(a) Peroxide-crosslinked fluoropolymer] The peroxide-crosslinked fluoropolymer of component (a) may be a perfluorofluoropolymer or a partially fluorinated fluoropolymer. Examples of peroxide-crosslinked fluoropolymers of component (a) include vinylidene fluoride-based fluoropolymers, tetrafluoroethylene / propylene-based polymers, ethylene / hexafluoropropylene-based fluoropolymers, ethylene / hexafluoropropylene / tetrafluoroethylene-based fluoropolymers, tetrafluoroethylene (TFE) / propylene / vinylidene fluoride (VdF)-based fluoropolymers, ethylene / hexafluoropropylene / vinylidene fluoride-based fluoropolymers, perfluoropolyether-based fluoropolymers, etc., among which perfluoropolyether-based fluoropolymers are preferred.

[0010] (a) The peroxide-crosslinked fluoropolymer of component (a) may contain halogen atoms such as iodine and bromine, and alkenyl groups as crosslinking sites, and it is particularly preferable that it contains alkenyl groups.

[0011] The above-mentioned perfluoropolyether-based fluoropolymer is preferably an addition product of a perfluoro compound (I) having at least two alkenyl groups in its molecule and a perfluoroalkylene group or a divalent perfluoropolyether group in its main chain, and an organosilicon compound (II) having at least two SiH groups in its molecule.

[0012] Furthermore, the addition reaction product is preferably a high molecular weight polymer, and is a non-liquid (raw rubber-like) perfluoropolyether-based fluoropolymer that does not self-flow (high viscosity) at room temperature (25°C ± 15°C).

[0013] The addition reaction product of component (I) and component (II) described below. <Component (I)> Component (I) is a perfluoro compound having at least two alkenyl groups in its molecule and a perfluoroalkylene group or a divalent perfluoropolyether group in its main chain. The perfluoro compound of component (I) is a compound that is technically difficult to synthesize into high molecular weight polymers such as resins or rubber on its own, and has at least two (e.g., 2 to 14), preferably 2 to 6, particularly preferably 2 alkenyl groups in its molecule, and a perfluoroalkylene group or a divalent perfluoropolyether group in its main chain, and preferably has a kinematic viscosity of 25 to 1,000,000 mm at 25°C. 2 It is a linear perfluoro compound with a s property of / s.

[0014] The (I) component is preferably a perfluoro compound represented by the following general formula (2): Rf[-U-Z(-Y-X)] β ] 2 (2) (In the formula, Rf is a perfluoroalkylene group or a divalent perfluoropolyether group, U is independently a single bond, a carbonyl bond, or a divalent organic group, Z is independently a single bond, a nitrogen atom, a silicon atom, a carbon atom, a phosphorus atom, or a 3- to 8-valent organic group, Y is independently a single bond or a divalent organic group, X is independently an alkenyl group, and β is an integer from 1 to 7. However, U and Z cannot be single bonds at the same time.)

[0015] In the above formula (2), Rf is a perfluoroalkylene group or a divalent perfluoropolyether group, and is preferably a divalent perfluoropolyether group.

[0016] As for perfluoroalkylene groups, -C n F 2n It is preferable that n is an integer from 1 to 6, preferably an integer from 2 to 4, and the following are examples: -CF2- -CF2CF2- -CF2CF2CF2- -CF2CF2CF2CF2CF2- -CF2CF2CF2CF2CF2CF2- -CF2CF2CF2CF2CF2CF2CF2CF2-

[0017] Furthermore, the divalent perfluoropolyether group is represented by the following formula -C a F 2a This includes repeating units (perfluorooxyalkylene units) represented by O- (where a is an integer from 1 to 6), such as those represented by the following general formula (4). -(C a F 2a O) b - (4) (In the formula, a is an integer from 1 to 6, and b is an integer from 1 to 300, preferably an integer from 1 to 200.)

[0018] The above -CC a F 2a Examples of repeating units represented by O- include the units shown in the following formulas: -CF2O- -CF2CF2O- -CF2CF2CF2O- -CF(CF3)CF2O- -CF(CF3)OCF2- -CF2OCF(CF3)- -CF2CF2CF2CF2O- -CF2CF2CF2CF2CF2CF2O- -CF2CF2CF2CF2CF2CF2CF2O- -C(CF3)2O-

[0019] Among these, the repeating unit represented by the following formula is particularly suitable: -CF2O- -CF2CF2O- -CF2CF2CF2O- -CF(CF3)CF2O- -CF(CF3)OCF2- -CF2OCF(CF3)-

[0020] The divalent perfluoropolyether group may consist of one of the repeating units described above, or it may consist of a combination of two or more of them.

[0021] For Rf, a group represented by the following formula is preferred, for example. (In the formula, p', q', r', s', c', and d' are each integers greater than or equal to 1, and the sum of these p', q', r', s', c', and d' is between 2 and 300. e is an integer between 0 and 6. Also, the repeating units shown in the parentheses enclosed by p', q', r', and s' may be combined randomly.)

[0022] In formula (2) above, U is independently a single bond, a carbonyl bond, or a divalent organic group. Preferably, the divalent organic group is an unsubstituted or substituted C2-C12 divalent hydrocarbon group, such as an ethylene group, a propylene group (trimethylene group, methylethylene group), a butylene group (tetramethylene group, methylpropylene group), an alkylene group such as a hexamethylene group or an octamethylene group, an arylene group such as a phenylene group, or a combination of two or more of these groups (alkylene-arylene group, etc.). The C2-C12 divalent hydrocarbon group may be an amide bond, an ether bond, a carbonyl bond, an ester bond, a diorganosilylene group such as a dimethylsilylene group, or -Si[OH][(CH2) f The group may contain one or more structures selected from the group consisting of groups represented by Si(CH3)3]- (where f is an integer from 2 to 4), and may also contain a group in which some or all of the hydrogen atoms bonded to the carbon atom are substituted with halogen atoms such as fluorine or iodine. The number of carbon atoms in a divalent hydrocarbon group having 2 to 12 carbon atoms, which is preferred as a divalent organic group, is the number of carbon atoms in an unsubstituted divalent hydrocarbon group. For example, if the above structure such as a dimethylsilylene group is interposed in the divalent hydrocarbon group, the number of carbon atoms in the above structure is not counted.

[0023] Examples of U include the group shown in the following structure. In the following structure, it is preferable that the left bond is bonded to Rf and the right bond is bonded to Z. - (CH2) u -O-(CH2) v - -CF2- -OCF2- -OCF(CF3)- (In the formula, f is an integer between 2 and 4, h is an integer between 2 and 6, preferably between 2 and 4, u and v are each independently integers between 1 and 4, g is an integer between 2 and 4, and Me is a methyl group.)

[0024] In formula (2) above, Z is independently a single bond, a nitrogen atom, a silicon atom, a carbon atom, a phosphorus atom, or a 3- to 8-valent organic group, and the 3- to 8-valent (the above (β+1) valent) organic group may include at least one of a nitrogen atom, an oxygen atom, a silicon atom, a carbon atom, and a phosphorus atom. Specifically, Z may be a single bond, a trivalent group represented by -N=, a trivalent group represented by -P=, a trivalent group represented by -PO=, or -R 1 The trivalent group represented by C=, -R 3 Examples include trivalent groups represented by Si=, tetravalent groups represented by -C≡, tetravalent groups represented by -O-C≡, and tetravalent groups represented by -Si≡, or siloxane residues with 3 to 8 valencies. Note that U and Z cannot be single-bonded simultaneously.

[0025] In the above, R 1 These are, independently of each other, preferably groups having repeating units of an alkyl group having 1 to 3 carbon atoms, a hydroxyl group, or an oxyalkylene group having 1 to 3 carbon atoms, which may have a diorganosiloxane structure with 2 to 51 silicon atoms interposed therein, or R 2 It is a silyl ether group represented by 3SiO-, R 2 R is independently a hydrogen atom, preferably an alkyl group having 1 to 3 carbon atoms, an aryl group such as a phenyl group, or an alkoxy group having 1 to 3 carbon atoms. 3 These are, independently of each other, preferably an alkyl group having 1 to 3 carbon atoms, an alkenyl group having 2 or 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a hydroxyl group, or a chloro group. When Z is a siloxane residue, it is preferable to have a linear, branched, or cyclic organopolysiloxane structure having 2 to 51 silicon atoms, preferably 2 to 13 silicon atoms, more preferably 2 to 11 silicon atoms, and even more preferably 2 to 5 silicon atoms. The organopolysiloxane is preferably one having methyl, ethyl, propyl, butyl groups having 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms, and an unsubstituted or fluorine-substituted alkyl group such as C3F7-C3H6- or a phenyl group. Also, a sylalkylene structure in which two silicon atoms are bonded by an alkylene group, i.e., Si-(CH2) h -Si may be included. In the above formula, h is an integer from 2 to 6, preferably from 2 to 4.

[0026] Examples of such Z are shown below. In the structure below, it is preferable that the leftmost bond connects to U, and the other bond connects to Y. (In the formula, i is an integer between 1 and 20, k is an integer between 1 and 50, and Me is a methyl group.)

[0027] In formula (2) above, Y is independently a single bond or a divalent organic group, and as a divalent organic group, preferably -C(=O)-NR'- (R' is a hydrogen atom, a methyl group, or a phenyl group), -C(=O)-O-, or an unsubstituted or substituted divalent hydrocarbon group having 2 to 12 carbon atoms, and as an unsubstituted or substituted divalent hydrocarbon group having 2 to 12 carbon atoms, examples include an ethylene group, a propylene group (trimethylene group, methylethylene group), a butylene group (tetramethylene group, methylpropylene group), an alkylene group such as a hexamethylene group or an octamethylene group, an arylene group such as a phenylene group, or a combination of two or more of these groups (alkylene-arylene group, etc.). The C2-C12 divalent hydrocarbon group may include one or more structures selected from the group consisting of amide bonds, ether bonds, carbonyl bonds, ester bonds, and diorganosilylene groups such as dimethylsilylene groups. Furthermore, Y is preferably a single bond when Z is a single bond.

[0028] Examples of Y include the group shown in the following structure. In the following structure, it is preferable that the left bond is bonded to Z and the right bond is bonded to X. (In the formula, f is an integer between 2 and 4, u is an integer between 1 and 4, g is an integer between 2 and 4, and Me is a methyl group.)

[0029] In formula (2) above, X is independently an alkenyl group, preferably having 2 to 8 carbon atoms, particularly 2 to 6 carbon atoms, and having a CH2=CH- structure. Examples include vinyl groups, allyl groups, propenyl groups, isopropenyl groups, butenyl groups, hexenyl groups, etc., with vinyl groups and allyl groups being particularly preferred.

[0030] In formula (2) above, β is an integer from 1 to 7, preferably an integer from 1 to 3, and more preferably 1.

[0031] Examples of perfluoro compounds represented by the above formula (2) include the following: (In the formula, p1, q1, r1, and s1 are each independent integers between 1 and 200, and the sum of p1, q1, r1, and s1 is between 3 and 300. Each repeating unit shown in parentheses may be randomly combined. Me is a methyl group.)

[0032] (In the formula, c1 and d1 are integers from 1 to 150, and the sum of c1 and d1 is from 2 to 300. Me is a methyl group, and Et is an ethyl group.)

[0033] (In the formula, c2 and d2 are integers between 1 and 150, and the sum of c2 and d2 is between 2 and 300. Me is a methyl group.)

[0034] The kinematic viscosity of the perfluoro compound, which is component (I) above, at 25°C is 25 to 1,000,000 mm². 2 It is preferably / s, and 100 to 100,000 mm 2 It is more preferable that the kinematic viscosity is 25 mm². 2If the reaction rate is less than 1,000,000 mm, the above addition reaction product may not be obtained in a raw rubber-like form. 2 If the kinematic viscosity exceeds / s, the handling properties when preparing the above addition reaction product may become significantly worse. The kinematic viscosity was measured using a Cannon-Fenske viscometer according to the method described in JIS Z8803:2011.

[0035] (I) The components may be used individually or in combination of two or more.

[0036] <Component (II)> Component (II) is an organosilicon compound having at least two SiH groups in its molecule, and is preferably an organosilicon compound represented by the following general formula (3). (In the formula, R 4 (A is an unsubstituted or substituted monovalent hydrocarbon group that does not contain an aliphatic unsaturated bond. W is a divalent organic group.)

[0037] In the above formula (3), R 4 The group is an unsubstituted or substituted monovalent hydrocarbon group that does not contain an aliphatic unsaturated bond, preferably having 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms. Specifically, examples include alkyl groups such as methyl, ethyl, propyl, and butyl groups, aryl groups such as phenyl and tolyl groups, aralkyl groups such as benzyl groups, and trifluoropropyl groups in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms, etc. Among these, the methyl group is preferred.

[0038] In formula (3) above, W is a divalent organic group, and is preferably a group represented by the following formula (i) or (ii). [In the formula, R 5 R is independently an oxygen atom or an unsubstituted or substituted divalent hydrocarbon group. 6 R is independently an unsubstituted or substituted monovalent hydrocarbon group, Rf'' is a perfluoroalkylene group or a divalent perfluoropolyether group, 7 is an unsubstituted or substituted monovalent hydrocarbon group or a dimethylsiloxy group, and D is independently -CH2-, -CH2O-, -CH2OCH2-, -E-NR 8 SO2- or -E-NR8 -CO- (where E is -CH2- or the following formula) (In the formula, Me is a methyl group.) This is a group represented by R 8 is a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group, and z is independently 0 or 1.

[0039] In the above equation (i), R 5 R is independently an oxygen atom or an unsubstituted or substituted divalent hydrocarbon group, and as an unsubstituted or substituted divalent hydrocarbon group, preferably having 1 to 8 carbon atoms, examples of alkylene groups such as methylene group, ethylene group, propylene group (trimethylene group, methylethylene group), butylene group (tetramethylene group, methylpropylene group), hexamethylene group, octamethylene group, etc., cycloalkylene groups such as cyclopropylene group, cyclobutylene group, cyclopentylene group, cyclohexylene group, cyclooctylene group, cyclononylene group, cyclodecylene group, etc., arylene group such as phenylene group, combinations of two or more of these groups (alkylene-arylene group, etc.), and groups in which some of the hydrogen atoms of these groups are substituted with halogen atoms, etc. 5 As such, oxygen atoms and methylene groups are preferred.

[0040] In the above equation (i), R 6 These are independently unsubstituted or substituted monovalent hydrocarbon groups, preferably having 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms. Specifically, examples include alkyl groups such as methyl, ethyl, propyl, and butyl groups; alkenyl groups such as vinyl and allyl groups; aryl groups such as phenyl and tolyl groups; aralkyl groups such as benzyl groups; and groups in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms, such as trifluoropropyl groups, C3F7C2H4- groups, C4F9C2H4- groups, CH2=CHC3F6C2H4- groups, or CH2=CHC4F8C2H4- groups. Among these, preferred are methyl groups, C4F9C2H4- groups, or CH2=CHC4F8C2H4- groups.

[0041] In the above formula (ii), Rf'' is a perfluoroalkylene group or a divalent perfluoropolyether group, and examples similar to Rf in formula (2) described above can be given. A perfluoroalkylene group is preferred as Rf'', and a -CF2CF2CF2CF2- group is particularly preferred.

[0042] In the above equation (ii), R 7 R is an unsubstituted or substituted monovalent hydrocarbon group, or a dimethylsiloxy group, and as an unsubstituted or substituted monovalent hydrocarbon group, the above-mentioned R 6 Examples of unsubstituted or substituted monovalent hydrocarbon groups are given. 7 Preferably, the group is a methyl group, a C4F9C2H4- group, or a CH2=CHC4F8C2H4- group.

[0043] In the above formula (ii), D is independently -CH2-, -CH2O-, -CH2OCH2-, -E-NR 8 SO2- or -E-NR 8 -CO- (where E is -CH2- or the following formula) (In the formula, Me is a methyl group.) This is a group represented by R 8 (This is a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group.)

[0044] Here, R 8 R is a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group, and as an unsubstituted or substituted monovalent hydrocarbon group, the above R 6 Examples of unsubstituted or substituted monovalent hydrocarbon groups are given. 8 Preferred groups include methyl groups, ethyl groups, trifluoromethyl groups, trifluoroethyl groups, pentafluoroethyl groups, phenyl groups, and pentafluorophenyl groups.

[0045] In the above formula (ii), z is independently 0 or 1, preferably 0.

[0046] Specific examples of organosilicon compounds represented by formula (3), where W is formula (i), are shown below. (In the formula, Me represents a methyl group.)

[0047] Specific examples of organosilicon compounds represented by formula (3), where W is formula (ii), are shown below. (In the formula, Me represents a methyl group.)

[0048] (II) Component (II) may be used alone or in combination of two or more components.

[0049] Furthermore, it is preferable to use a component (II) that has an alkenyl group in its molecule, and it is even more preferable to use a combination of a component with an alkenyl group and a component without an alkenyl group. When using a combination of a component with an alkenyl group and a component without an alkenyl group, it is preferable that the amounts used be such that the molar ratio of the component with an alkenyl group to the component without an alkenyl group is 99:1 to 1:99, and particularly 80:20 to 20:80.

[0050] <Preparation of Addition Product> The addition product is obtained by an addition reaction (hydrosilylation reaction) between the alkenyl group in component (I) and the SiH group in component (II). Specifically, the addition product can be prepared by adding a hydrosilylation reaction catalyst to a mixture of components (I) and (II) and carrying out a hydrosilylation reaction.

[0051] The reaction ratio of component (I) to component (II) is preferably such that there are 1.00 to 2.00 mol of SiH groups in component (II) per 1 mol of alkenyl groups in component (I), and more preferably 1.01 to 1.50 mol. If the ratio is less than 1.00 mol, the resulting addition reaction product may not be in the form of raw rubber, and if it exceeds 2.00 mol, the heat resistance of the cured product of the resulting composition may decrease.

[0052] Hydrosilylation catalysts are generally precious metals (especially platinum group metals) or compounds thereof, and because they are expensive, relatively readily available platinum or platinum compounds are often used. Examples of platinum compounds include chloroplatinic acid; complexes of chloroplatinic acid with olefins such as ethylene; complexes of chloroplatinic acid with alcohols or vinylsiloxanes; and metallic platinum supported on silica, alumina, carbon, etc. Other hydrosilylation catalysts besides platinum or platinum compounds include rhodium, ruthenium, iridium, and palladium compounds, such as RhCl(PPh3)3, RhCl(CO)(PPh3)2, and Ru3(CO). 12 Examples include IrCl(CO)(PPh3)2, Pd(PPh3)4, etc. In the above formula, Ph represents a phenyl group.

[0053] When using these catalysts, if they are solid catalysts, they can be used in solid form. However, to obtain a more uniform cured product, it is preferable to use chloroplatinic acid or complexes dissolved in a suitable solvent such as toluene or ethanol.

[0054] This hydrosilylation reaction catalyst may be used alone or in combination of two or more types. The amount of these catalysts used is not particularly limited, and the desired curing rate can be obtained with the amount of catalyst. However, from an economic standpoint or to obtain a good cured product, the amount is usually 0.1 to 2,000 ppm, preferably 0.1 to 500 ppm, and particularly preferably 0.5 to 200 ppm (in terms of the mass of platinum group metal atoms) relative to the total mass of components (I) and (II), and can be appropriately increased or decreased depending on the desired curing rate.

[0055] The conditions for the above addition reaction (hydrosilylation reaction) can be selected as appropriate. The reaction may be carried out at room temperature, but it can also be accelerated by heating to 50-200°C. The reaction time can be 10 minutes to 12 hours, and especially 1-2 hours.

[0056] The addition reaction product obtained by the above method preferably has an alkenyl group derived from component (II) in its molecule. The amount of this alkenyl group is 5.0 × 10⁻⁶. -5~1.2 x 10 -2 Preferably, it is mol / 100g, and 1.0 × 10 -4 ~1.0 x 10 -2 It is more preferable that the amount is mol / 100g. If there are too few alkenyl groups, the heat resistance of the cured product of the resulting composition may decrease, and if there are too many, the roll processability of the resulting composition may deteriorate significantly. The amount of alkenyl groups is 1 It can be measured by H-NMR, FT-IR, etc.

[0057] The addition reaction product obtained by the above method has a dissolution kinematic viscosity of 1 to 100 mmHg at 25°C with 10% by mass HFE-7200 (Novec®, manufactured by 3M). 2 It is preferable that it be / s, and 5 to 50 mm 2 It is more preferable that the kinematic viscosity of dissolution be / s. If the above kinematic viscosity of dissolution is too low, the rollability of the resulting composition may be significantly impaired, and if it is too high, the dispersibility of component (b) in relation to the addition reaction product may be poor. The above kinematic viscosity of dissolution can be measured using a Cannon-Fenske viscometer by the method described in JIS Z8803:2011. Note that since the above addition reaction product has a gum-like appearance, it may be difficult to measure its viscosity using a rotational viscometer or the like, so measurement by kinematic viscosity of dissolution is preferred.

[0058] [Component (b)] Component (b) is a reinforcing filler surface-treated with a surface treatment agent, wherein the surface treatment agent is a silane coupling agent having aliphatic hydrocarbon groups having 3 to 40 carbon atoms (a silane compound having aliphatic hydrocarbon groups having 3 to 40 carbon atoms and a hydrolyzable group), and the aliphatic hydrocarbon groups preferably have 4 to 20 carbon atoms, more preferably 6 to 16 carbon atoms, and even more preferably 8 to 12 carbon atoms.

[0059] As the silane coupling agent having an aliphatic hydrocarbon group with 3 to 40 carbon atoms, the compound represented by the following general formula (1-1) can be used. 4-m Six 1 m (1-1) (wherein m is 1 to 3, R is an alkyl group having 3 to 40 carbon atoms, X 1(This is a hydrolyzable group.)

[0060] In the above formula, R is an alkyl group having 3 to 40 carbon atoms, preferably an alkyl group having 4 to 20 carbon atoms, more preferably an alkyl group having 6 to 16 carbon atoms, and even more preferably an alkyl group having 8 to 12 carbon atoms. Specifically, examples include n-propyl group, n-butyl group, n-hexyl group, n-octyl group, n-decyl group, n-dodecyl group, etc.

[0061] In the above formula, X 1 Examples of hydrolyzable groups include alkoxy groups with 1 to 12 carbon atoms, particularly 1 to 10 carbon atoms, such as methoxy, ethoxy, propoxy, and butoxy groups; alkoxyalkoxy groups with 2 to 12 carbon atoms, particularly 2 to 10 carbon atoms, such as methoxymethoxy and methoxyethoxy groups; acyloxy groups with 1 to 10 carbon atoms, such as acetoxy groups; alkenyloxy groups with 2 to 10 carbon atoms, such as isopropenoxy groups; halogen groups such as chlorine, bromo, and iodine groups; and amino groups. Among these, methoxy and ethoxy groups are preferred. Also, m is an integer from 1 to 3, preferably 3.

[0062] Specific examples of silane coupling agents having aliphatic hydrocarbon groups with 3 to 40 carbon atoms include n-propyltrimethoxysilane, n-hexyltrimethoxysilane, n-octyltrimethoxysilane, n-decyltrimethoxysilane, and n-dodecyltrimethoxysilane. These can be commercially available, and examples include KBM-3033, KBM-3063, KBE-3063, KBM-3103C, and KBE-3083 (all manufactured by Shin-Etsu Chemical Co., Ltd.).

[0063] Examples of reinforcing fillers to be surface-treated with the above-mentioned surface treatment agent include silica-based reinforcing fillers, quartz powder, fused quartz powder, diatomaceous earth, calcium carbonate, and other reinforcing or semi-reinforcing fillers. Silica-based reinforcing fillers may include silica powders such as fumed silica (fumed silica or dry silica), precipitated silica (wet silica), spherical silica (fused silica), sol-gel silica, and silica aerogel. Among these, fumed silica is particularly preferred as component (b) from the viewpoint of improving the mechanical strength of the resulting cured product and improving the dispersion stability of each composition.

[0064] It is preferable that the reinforcing filler is directly surface-treated in its powder form beforehand. As a method for surface-treating the reinforcing filler with a surface treatment agent, generally known techniques can be employed. For example, the untreated reinforcing filler and the surface treatment agent may be placed in a sealed mechanical kneading apparatus or fluidized bed at atmospheric pressure, and a catalyst and water to promote hydrolysis may be used as needed. The mixture may be mixed at room temperature or by heat treatment in the presence of an inert gas as necessary, and after kneading, it can be dried to prepare the product. The amount of surface treatment agent should be equal to or greater than the amount calculated from the area on which the surface treatment agent can cover the surface of the reinforcing filler.

[0065] In the above surface treatment method, the method of contacting the reinforcing filler with the surface treatment agent is not particularly limited, but a dry method is preferred from the viewpoint of productivity. Specifically, a method of spraying the undiluted surface treatment agent onto the reinforcing filler while it is being stirred in a mixer, or a method of heating and vaporizing the surface treatment agent and introducing it into the mixer, is simple and preferred. The undiluted surface treatment agent may also be used after being diluted with a solvent.

[0066] When the stock solution is diluted before use, suitable solvents include alcohol-based solvents such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol; hydrocarbon-based solvents such as pentane, hexane, cyclohexane, heptane, isooctane, toluene, xylene, and mesitylene; aprotic polar solvents such as ethyl acetate, acetonitrile, propionitrile, N,N-dimethylformamide, and N-methylpyrrolidone; halogenated hydrocarbon-based solvents such as dichloromethane, dichloroethane, and chlorobenzene; and ether-based solvents such as diethyl ether, tetrahydrofuran, dioxane, and dimethoxyethane. These solvents may be used individually or in combination of two or more. Among the above solvents, methanol, ethanol, 2-propanol, toluene, and tetrahydrofuran are particularly preferred.

[0067] In the present invention, the surface treatment is preferably performed by mixing a reinforcing filler and a surface treatment agent, followed by a predetermined standing or heat treatment. The standing or heat treatment temperature is not particularly limited, but from the viewpoint of reactivity, it is preferably 0 to 500°C, more preferably 20 to 300°C, and even more preferably 100 to 250°C. The reaction time is not particularly limited, but is preferably 0.1 to 30 hours, more preferably 0.5 to 10 hours, and even more preferably 1 to 2 hours. Furthermore, from the viewpoint of safety, the above surface treatment is preferably performed in an inert gas atmosphere such as nitrogen or argon.

[0068] The specific surface area of ​​the reinforcing filler surface-treated with a surface treatment agent, calculated by the BET method, is 50 m² to improve its mechanical properties. 2 / g or more, especially 100m 2 It is preferable that the amount be 300 m or more, and furthermore, because the thickening of the composition when component (b) is added may increase and make blending difficult, 2 / g or less, especially 250m 2 It is preferable that the value is less than or equal to / g. In this invention, the specific surface area obtained by the BET method is a value calculated using the BET formula from the isothermal adsorption curve measured by the nitrogen gas adsorption method.

[0069] The reinforcing filler surface-treated with a surface treatment agent preferably has a bulk density of 20 to 200 g / L, and more preferably 40 to 180 g / L. If the bulk density of the reinforcing filler surface-treated with a surface treatment agent is less than 20 g / L, the viscosity of the resulting composition will increase, making formulation difficult. If it exceeds 200 g / L, a sufficient reinforcing effect may not be provided. In this invention, the bulk density is a value measured by the tap method or the like.

[0070] The degree of hydrophobicity of the reinforcing filler surface-treated with a surface treatment agent is preferably 1 to 99%, more preferably 10 to 90%, and even more preferably 20 to 70%. If the degree of hydrophobicity is too low, integration with component (a) may be insufficient, and if it is too high, the strength of the resulting cured product may be low. In this invention, the degree of hydrophobicity is determined by the methanol titration method shown below. (1) The sample is floated in a predetermined amount of pure water, and methanol is added dropwise while stirring. (2) The amount of methanol added when the entire amount of the sample is suspended in pure water is read. (3) The value obtained by [{Amount of methanol added (mL)} / {Amount of methanol added (mL) + Amount of pure water (mL)}] × 100 is the degree of hydrophobicity.

[0071] Furthermore, the surface carbon content (carbon content: mass%) of the reinforcing filler surface-treated with a surface treatment agent is preferably in the range of 0.1 to 50 mass%, and more preferably in the range of 0.5 to 30 mass%. If the surface carbon content is less than 0.1 mass%, uniform mixing with the addition reaction product may be difficult, and if the surface carbon content exceeds 50 mass%, sufficient mechanical strength may not be obtained in the cured product of the resulting composition. In this invention, the surface carbon content is a value measured by a known elemental analysis method.

[0072] (b) The component may be used alone or in combination of two or more components.

[0073] The amount of component (b) is preferably 10 to 60 parts by mass, and more preferably 15 to 50 parts by mass, relative to 100 parts by mass of component (a). If the amount of component (b) is less than 10 parts by mass, the mechanical strength of the resulting cured product may be insufficient, and if it is more than 60 parts by mass, the cured product may become brittle and its mechanical strength may decrease.

[0074] [Peroxide Crosslinking Agent] The peroxide crosslinked fluororubber composition of the present invention may optionally contain a peroxide crosslinking agent for curing the peroxide crosslinked fluororubber composition. There are no particular restrictions on the peroxide crosslinking agent, but examples include dibenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butyl peroxyacetate, t-butyl peroxybenzoate, t-butyl peroxyisopropyl monocarbonate, and 2,5-dimethyl-2,5-di-t-butyl peroxyhexane. 2,5-dimethyl-2,5-di-t-butyl peroxyhexane is preferred from the viewpoint of storage stability and scorch prevention.

[0075] When adding a peroxide crosslinking agent, the amount added should be sufficient to cure the peroxide crosslinked fluororubber composition of the present invention, but preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass, per 100 parts by mass of component (a). If the amount is less than 0.1 parts by mass, crosslinking may be insufficient or delayed, and if it exceeds 10 parts by mass, it may adversely affect the physical properties.

[0076] [Other Components] In order to enhance the practicality of the peroxide crosslinked fluororubber composition of the present invention, in addition to the above components (a) and (b), the following optional components may be added as needed: fillers other than component (b), adhesion modifiers, plasticizers, viscosity modifiers, flexibility modifiers, inorganic pigments such as titanium dioxide, iron oxide, carbon black, and cobalt aluminate, heat resistance improvers such as titanium dioxide, iron oxide, carbon black, cerium oxide, cerium hydroxide, zinc carbonate, magnesium carbonate, and manganese carbonate, thermal conductivity modifiers such as alumina, boron nitride, silicon carbide, and metal powders, and conductivity modifiers such as carbon black, silver powder, and conductive zinc oxide. The amount of these additives added is arbitrary as long as it does not impair the purpose of the present invention. These components may be added at any stage during composition preparation.

[0077] As plasticizers, viscosity modifiers, and flexibility imparters, non-reactive (non-functional) linear polyfluoro compounds that do not contain functional groups (alkenyl groups and hydrosilyl groups) involved in the hydrosilylation reaction in their molecules, as represented by the following general formulas (5) and (6), can be used.

[0078] F-(CF2CF2CF2O) v' -J (5) (wherein J is C) w' F 2w'+1 (The base is represented by -(w' is an integer from 1 to 3), and v' is an integer from 1 to 500, preferably an integer from 2 to 300.)

[0079] J-{(OCF(CF3)CF2) x' - (OCF2CF2) y' - (OCF2) z’}-O-J (6) (In the formula, J is the same as above, and x' and y' are integers from 0 to 300, preferably from 0 to 150, except when both x' and y' are 0. Also, z' is an integer from 1 to 300, preferably from 1 to 150. Each repeating unit may be randomly combined with others.)

[0080] Specific examples of linear polyfluoro compounds represented by the above general formula (5) or (6) include the following: F-(CF2CF2CF2O) v''-CF2CF3 (v'' is an integer between 1 and 200.) CF3-{(OCF(CF3)CF2) x'' - (OCF2) z''}-O-CF3 (x'' is an integer from 1 to 200, z'' is an integer from 1 to 200. Each repeating unit may be randomly combined with others.) CF3-{(OCF2CF2) y'' - (OCF2) z''}-O-CF3 (where y'' is an integer between 1 and 200, and z'' is an integer between 1 and 200. Each repeating unit may be randomly combined with others.)

[0081] The linear polyfluoro compounds represented by the above general formula (5) or (6) may be used individually or in combination of two or more.

[0082] The peroxide crosslinked fluororubber composition of the present invention can be obtained by uniformly kneading predetermined amounts of the above components (a) and (b), and optionally a peroxide crosslinking agent and other components. As for the kneading method, two rolls, kneaders, pressure kneaders, Banbury mixers, etc., which are commonly used in rubber mixing, can be used. Among these, closed-type kneaders such as pressure kneaders and Banbury mixers are preferred from the viewpoint of workability and productivity. A particularly preferred kneading method when incorporating a peroxide crosslinking agent is to knead the above components (a) and (b) in a closed-type kneader to obtain a base compound, and then mix in the peroxide crosslinking agent with two rolls.

[0083] When obtaining a base compound of component (a) and component (b) as described above, it is preferable that component (b) has been pre-treated with the surface treatment agent described above on the reinforcing filler. If the untreated reinforcing filler and the surface treatment agent are mixed simultaneously during the base compound mixing process, the surface treatment agent may not adequately coat the reinforcing filler, resulting in the inability to obtain the effects of the present invention, or the base compound may not be obtained because it does not integrate with component (a).

[0084] The peroxide-crosslinked fluororubber composition of the present invention, preferably a peroxide-crosslinked fluororubber composition (base compound) without a peroxide crosslinking agent, preferably has a Mooney viscosity ML(1+4)(100°C) of 5 or higher, more preferably 5 to 100, even more preferably 10 to 90, and particularly preferably 20 to 80. When the Mooney viscosity of the base compound is within the above range, the processability and moldability are good. Mooney viscosity is an indicator of the moldability of the material and can be measured with reference to JIS K6300-1:2013. In the present invention, the Mooney viscosity can be set within the above range by adding 10 to 60 parts by mass of component (b), which has a surface carbon content in the range of 0.1 to 50% by mass, to 100 parts by mass of component (a).

[0085] The molding method for the peroxide crosslinked fluororubber composition of the present invention is not particularly limited, and examples include press molding, compression molding, and injection molding. As for the curing conditions, the temperature and time at which the crosslinking reaction is completed can be appropriately selected, but it can be 100 to 200°C, particularly 120 to 170°C for 1 minute to 2 hours, and especially 5 minutes to 1 hour. Furthermore, in order to stabilize the physical properties of this composition, it is preferable to perform a secondary cure by heat treatment at 100 to 230°C, particularly 150 to 200°C for 1 to 24 hours, and especially 1 to 20 hours. Secondary curing is less effective below 100°C, and there is a risk of thermal decomposition above 230°C.

[0086] The cured fluororubber product obtained by curing the peroxide crosslinked fluororubber composition of the present invention preferably has a compressibility of 25% and a compression set of 40% or less, and more preferably 38% or less, after compression at 200°C for 70 hours, in accordance with JIS K 6262:2013. If the compression set exceeds 40%, the sealing performance of the cured product obtained in the present invention may be insufficient when used as an O-ring. In the present invention, the compression set can be kept within the above range by using a silane coupling agent having an aliphatic hydrocarbon group with 3 to 40 carbon atoms as a surface treatment agent in component (b).

[0087] A rubber molded article obtained by curing the peroxide crosslinked fluororubber composition of the present invention has excellent compression set resistance and rubber properties.

[0088] Rubber molded articles obtained by curing the peroxide crosslinked fluororubber composition of the present invention include, for example, diaphragms such as fuel regulator diaphragms, pulsation damper diaphragms, oil pressure switch diaphragms, and EGR diaphragms; valves such as canister valves and power control valves; O-rings such as quick connector O-rings and injector O-rings; and sealing parts such as oil seals and cylinder head gaskets; rubber parts for chemical plants, specifically pump diaphragms, valves, and O-rings. Examples of applications include sealing components such as hoses, packings, oil seals, and gaskets; rubber components for inkjet printers; rubber components for semiconductor manufacturing lines, specifically diaphragms, valves, O-rings, packings, and gaskets for equipment that comes into contact with chemicals; valves requiring low friction and wear resistance; rubber components for analytical and scientific instruments, specifically diaphragms, valves, and sealing components (O-rings, packings, etc.) for pumps; rubber components for medical devices, specifically pumps, valves, and joints; as well as molded parts, extruded parts, copier rolls, sealing components for fuel cells, and laminated rubber cloth. In addition, the peroxide crosslinked fluororubber composition of the present invention can also be used as a coating material.

[0089] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples. In the following examples, the kinematic viscosity of the 10% by mass solvent solution of the addition product is the value measured at 25°C using a Cannon-Fenske viscometer with an HFE-7200 (3M) solution according to the method described in JIS Z8803:2011. The amount of alkenyl groups (vinyl groups) in component (I) of the addition product. 1 The value was calculated from the results of analysis such as H-NMR, and the SiH group of component (II) 1 The values ​​were calculated based on analysis results such as 1H-NMR. The room temperature was 25°C. In the formula, Me represents a methyl group.

[0090] Furthermore, in the example below, the BET specific surface area, bulk density, degree of hydrophobicity, and surface carbon content (carbon content) of hydrophobic silica were measured using the following method.

[0091] <BET Specific Surface Area> The specific surface area of ​​the obtained hydrophobic silica was measured using the BET single-point method based on nitrogen adsorption amount, with a fully automatic BET specific surface area measuring instrument Macsorb (Model-1201) manufactured by Mountec Co., Ltd. A mixed gas (helium: 70 vol%, nitrogen: 30 vol%) was flowed into the instrument at 0.15 MPa at a rate of 25 mL / min. After degassing the hydrophobic silica at 300°C for 20 minutes, nitrogen was adsorbed onto the hydrophobic silica while cooling the cell with liquid nitrogen. The specific surface area was calculated from the amount of nitrogen adsorbed per unit mass.

[0092] <Bulk Density> The bulk density of the obtained hydrophobic silica was measured by the tap method.

[0093] <Hydrophobicity> The hydrophobicity of the obtained hydrophobic silica was measured as follows: 0.2 g of powder was weighed into a 200 mL beaker, 50 mL of pure water was added, and the mixture was stirred with a magnetic stirrer. Methanol was added dropwise using a burette, and the endpoint was reached when the powder was completely dispersed. The hydrophobicity was calculated from the amount of methanol added at the endpoint. Hydrophobicity (%) = (Amount of methanol added × 100) / (50 + Amount of methanol added)

[0094] <Surface Carbon Content> The surface carbon content of the obtained hydrophobic silica was measured using an EMIA-10 manufactured by Horiba, Ltd. Hydrophobic silica on a boat was burned at 1,350°C under an oxygen gas (purity 99.5% by volume or higher) airflow of 0.3 MPa, and the generated CO2 / CO was detected with an infrared detector. Calibration curves were created using JSS057-10 (carbon content 0.58% by mass) and JSS102-9 (carbon content 4.59% by mass) as standard samples, and the carbon content of the hydrophobic silica was quantified.

[0095] Components of the compositions used in the examples and comparative examples

[0096] [(a) component: peroxide crosslinked fluoropolymer] (a-1): An addition reaction product obtained by the following method. 100 g of the following component (I-1), 0.94 g of the following component (II-1), and 2.24 g of the following component (II-2) were charged into a 1-liter beaker, and after thoroughly mixing manually using a stirring rod at room temperature for 10 minutes, 0.2 g (platinum content 0.5 mass%) of a hydrosilylation reaction catalyst (trade name: CAT-PL-50T, manufactured by Shin-Etsu Chemical Co., Ltd.) was added, and mixing was continued for another 15 minutes. Then, an addition reaction product (peroxide crosslinked fluoropolymer, 10 mass% HFE-7200 (manufactured by 3M) solution kinematic viscosity: 10 mm 2 / s, alkenyl group content: 4.1×10 -3 mol / 100 g) was obtained by heating at 100 °C for 1 hour.

[0097] (a-2): An addition reaction product obtained by the following method. 100 g of the following component (I-2), 0.94 g of the following component (II-1), and 2.24 g of the following component (II-2) were charged into a 1-liter beaker, and after thoroughly mixing manually using a stirring rod at room temperature for 10 minutes, 0.2 g (platinum content 0.5 mass%) of a hydrosilylation reaction catalyst (trade name: CAT-PL-50T, manufactured by Shin-Etsu Chemical Co., Ltd.) was added, and mixing was continued for another 15 minutes. Then, an addition reaction product (peroxide crosslinked fluoropolymer, 10 mass% HFE-7200 (manufactured by 3M) solution kinematic viscosity: 9.8 mm 2 / s, alkenyl group content: 4.0×10 -3 mol / 100 g) was obtained by heating at 100 °C for 1 hour.

[0098] <(I) component> (I-1): A perfluorinated compound having alkenyl groups at both ends represented by the following formula (c + d = 90, alkenyl group content: 0.012 mol / 100 g)

[0099] (I-2): A perfluorinated compound having alkenyl groups at both ends represented by the following formula (c + d = 9, alkenyl group content: 0.012 mol / 100 g)

[0100] <(II) component> (II-1): A compound represented by the following formula (SiH group content: 4.6×10 -3mol / g

[0101] (II-2): A compound represented by the following formula (SiH group content: 4.6×10 -3 mol / g

[0102] [(b) component: a reinforcing filler surface-treated with a surface treatment agent] (b-1): In a mixer with a volume of 10 L of hydrophobic silica obtained by the following method, 200 g of hydrophilic fumed silica (BET specific surface area: about 300 m 2 / g) was charged, and the inside of the mixer was replaced with nitrogen. 14.8 g of water and 46.8 g of n-propyltrimethoxysilane were sequentially sprayed with a single-fluid nozzle while stirring. Then, it was heat-treated at 180°C for 1 hour, the volatile components were removed, and then cooled to obtain hydrophobic silica (BET specific surface area: about 229 m 2 / g, bulk density: about 64 g / L, degree of hydrophobization: 26%, surface carbon content (carbon content): 4.3% by mass).

[0103] (b-2): Hydrophobic silica (BET specific surface area: about 241 m 2 / g, bulk density: about 62 g / L, degree of hydrophobization: 48%, surface carbon content (carbon content): 4.3% by mass) was obtained in the same manner as (b-1), except that 51.6 g of n-hexyltrimethoxysilane was used as the hydrophobic silica surface treatment agent obtained by the following method.

[0104] (b-3): Hydrophobic silica (BET specific surface area: about 221 m 2 / g, bulk density: about 76 g / L, degree of hydrophobization: 38%, surface carbon content (carbon content): 10.6% by mass) was obtained in the same manner as (b-1), except that 58.6 g of n-octyltrimethoxysilane was used as the hydrophobic silica surface treatment agent obtained by the following method.

[0105] (b-4): Hydrophobic silica (BET specific surface area: about 178 m 2 / g, bulk density: about 82 g / L, degree of hydrophobization: 62%, surface carbon content (carbon content): 11.4% by mass) was obtained in the same manner as (b-1), except that 65.6 g of n-decyltrimethoxysilane was used as the hydrophobic silica surface treatment agent obtained by the following method.

[0106] (b-5): Except for using 36.3 g of n-dodecyltrimethoxysilane as the hydrophobic silica surface treatment agent obtained by the method described below, hydrophobic silica (BET specific surface area: approximately 185 m²) was prepared in the same manner as in (b-1). 2 The results obtained were: 1 / g, bulk density: approximately 85 g / L, degree of hydrophobicity: 58%, surface carbon content (carbon content): 15.2 mass%.

[0107] (b-6): Except for using 61.0 g of methyltrimethoxysilane as the hydrophobic silica surface treatment agent obtained by the method described below, hydrophobic silica (BET specific surface area: approximately 211 m²) was prepared in the same manner as in (b-1). 2 The results obtained were: 1 / g, bulk density: approximately 50 g / L, degree of hydrophobicity: 0%, surface carbon content (carbon content): 1.8 mass%).

[0108] [Peroxide crosslinking agent] 2,5-dimethyl-2,5-di-t-butylperoxyhexane

[0109] [Examples 1-6, Comparative Example 1] Preparation of base compound The above components (a) and (b) were uniformly kneaded using a pressure kneader in the amounts shown in Table 1 below to obtain a base compound.

[0110] Mooney viscosity measurement Using the obtained base compound, the Mooney viscosity ML(1+4) (100°C) was measured in accordance with JIS K6300-1:2013. The results are shown in Table 1. The Mooney viscosity was measured by the following method: <Mooney viscosity> ・Measurement item: ML(1+4) (preheating 1 minute, rotation 4 minutes) ・Apparatus: SMV-301RT (manufactured by Shimadzu Corporation) ・Test temperature: 100°C ・Rotor: L-type

[0111] Preparation of Peroxide Crosslinked Fluororubber Composition The base compound obtained in the above preparation of the base compound was uniformly kneaded with the amount of peroxide crosslinking agent shown in Table 1 below using a 3.5-inch rubber two-roller to obtain a peroxide crosslinked fluororubber composition.

[0112] Molding of Peroxide Crosslinked Fluororubber Composition The peroxide crosslinked fluororubber composition obtained above was crosslinked in a 75-ton rubber press at 150°C for 15 minutes, followed by post-curing at 200°C for 4 hours to obtain a rubber sheet (size: 130 mm x 70 mm x 2 mm thick) and a large compression set test specimen (size: diameter 29.0 ± 0.5 mm, thickness 12.5 mm ± 0.5 mm).

[0113] Evaluation of normal physical properties: Using the rubber sheet obtained above, the normal physical properties (hardness (durometer type A), tensile strength, elongation at break, tear strength) were measured in accordance with JIS K6249. The results are shown in Table 1.

[0114] Evaluation of Compression Set: Using the compression set test specimens obtained above, the compression set (200°C, 70 hours, 25% compression) was measured in accordance with JIS K6262:2013. The results are shown in Table 1.

[0115]

[0116] As is clear from the above results, the peroxide crosslinked fluororubber compositions of Examples 1 to 6, which contain components (a) and (b) of the present invention, exhibit excellent physical properties and compression set resistance of the cured product, whereas the peroxide crosslinked fluororubber composition of Comparative Example 1, in which the surface treatment agent for the reinforcing filler is outside the scope of the present invention, exhibits inferior compression set resistance of the cured product.

[0117] [Comparative Example 2] Preparation of base compound 100 g of the addition reaction product (peroxide crosslinked fluoropolymer) from (a-1) above is transferred to a pressurized kneader, and hydrophilic fumed silica (BET specific surface area: approximately 300 m²) is used. 2 30 g of ( / g) and 8.9 g of n-propyltrimethoxysilane were added and kneaded. After kneading for 1 hour, the components did not integrate, and a base compound could not be obtained.

Claims

1. A peroxide-crosslinked fluororubber composition comprising (a) a peroxide-crosslinked fluoropolymer and (b) a reinforcing filler surface-treated with a surface treatment agent, wherein the surface treatment agent is a silane coupling agent having aliphatic hydrocarbon groups having 3 to 40 carbon atoms.

2. The peroxide crosslinked fluororubber composition according to claim 1, wherein component (a) is a perfluoropolyether-based fluoropolymer.

3. The peroxide crosslinked fluororubber composition according to claim 2, wherein the perfluoropolyether-based fluoropolymer is an addition reaction product of a perfluoro compound (I) having at least two alkenyl groups in its molecule and a perfluoroalkylene group or a divalent perfluoropolyether group in its main chain, and an organosilicon compound (II) having at least two SiH groups in its molecule.

4. The above component (I) is given by the following general formula (2) Rf[-U-Z(-Y-X)] β ]2 (2) The peroxide crosslinked fluororubber composition according to claim 3, wherein the perfluoro compound is represented by the formula: (wherein Rf is a perfluoroalkylene group or a divalent perfluoropolyether group, U is independently a single bond, a carbonyl bond, or a divalent organic group, Z is independently a single bond, a nitrogen atom, a silicon atom, a carbon atom, a phosphorus atom, or a 3- to 8-valent organic group, Y is independently a single bond or a divalent organic group, X is independently an alkenyl group, and β is an integer from 1 to 7. However, U and Z cannot be single bonds at the same time.) 5. Rf in equation (2) above is -C a F 2a The peroxide crosslinked fluororubber composition according to claim 4, comprising one or more repeating units (perfluorooxyalkylene units) represented by O- (wherein a is an integer from 1 to 6).

6. The above component (II) is the following general formula (3) (In the formula, R 4 The peroxide crosslinked fluororubber composition according to claim 3, wherein is an organosilicon compound represented by ) where is an unsubstituted or substituted monovalent hydrocarbon group that does not contain an aliphatic unsaturated bond, and W is a divalent organic group.

7. In the above formula (3), W is the formula (i) or (ii). [In the formula, R 5 is independently an oxygen atom, or an unsubstituted or substituted divalent hydrocarbon group, and R 6 is independently an unsubstituted or substituted monovalent hydrocarbon group, Rf” is a perfluoroalkylene group or a divalent perfluoropolyether group, and R 7 is an unsubstituted or substituted monovalent hydrocarbon group, or a dimethylsiloxy group, D is independently -CH2-, -CH2O-, -CH2OCH2-, -E-NR 8 SO2- or -E-NR 8 -CO- (where E is -CH2- or the following formula (where Me is a methyl group).) and R 8 is a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group.), and z is independently 0 or 1.] The peroxide crosslinkable fluororubber composition according to claim 6, which is a group represented by the following formula:

8. The peroxide crosslinked fluororubber composition according to claim 1, wherein in component (b) above, the surface treatment agent is a silane coupling agent having an aliphatic hydrocarbon group having 4 to 20 carbon atoms.

9. In component (b) above, the surface treatment agent is the following formula (1-1) R 4-m Six 1 m (1-1) (wherein m is 1 to 3, R is an alkyl group having 3 to 40 carbon atoms, X 1 The peroxide crosslinked fluororubber composition according to claim 1, wherein the silane coupling agent is represented by ) (where is a hydrolyzable group).

10. The peroxide crosslinked fluororubber composition according to claim 1, which is a mixture of component (a) and component (b) described above.

11. The peroxide crosslinked fluororubber composition according to claim 1, wherein the Mooney viscosity (ML(1+4)) (100°C) is 5 or more.

12. The peroxide-crosslinked fluororubber composition according to claim 1, further containing a peroxide crosslinking agent.

13. A rubber molded article obtained by curing a peroxide crosslinked fluororubber composition according to any one of claims 1 to 12.

14. A cured fluororubber product obtained by curing a peroxide crosslinked fluororubber composition according to any one of claims 1 to 12, having a compressibility of 25% and a compression set of 40% or less after compression at 200°C for 70 hours, in accordance with JIS K 6262:2013.

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