JP7740225B2 - Diarylamine compound, surface-treated filler, and polymer composition - Google Patents

Description

The present invention relates to novel diarylamine compounds that can provide surface-treated fillers that exhibit excellent anti-aging properties for polymer materials, surface-treated fillers obtained using such diarylamine compounds, and polymer compositions containing such surface-treated fillers.

With the development of petrochemistry, polymers composed of organic compounds have contributed to human development in various forms, such as plastics, rubber, fibers, and films. Because these are used in a variety of environments depending on their application, they have been improved to ensure long-term use by giving each product durability in the expected environments. For example, products have been developed that are UV-resistant for plastics used outdoors, and cold-resistant for rubber that functions in extremely cold regions.

Meanwhile, internal combustion engines, such as engines, have seen an increase in use as a result of industrial development. Because they require lubricating oil and generate a great deal of heat, the polymers used in them must be resistant to oil and high temperatures. Polymers used in automobile engines, in particular, must be able to maintain flexibility for long periods of time even when exposed to oil and high temperatures, and must not develop defects such as cracks. To meet these requirements, various oil- and heat-resistant rubbers have been developed. Among these, acrylic rubber, a polymer with rubber elasticity and excellent oil and heat resistance and flexibility, is widely used in components such as seals, gaskets, packings, and hoses used in automobile engines. Depending on the required properties, its oil and heat resistance are further enhanced by modifying the crosslinking structure, antioxidants, and compounding agents.

For example, Patent Document 1 discloses an antioxidant that improves heat resistance. However, such an antioxidant alone cannot suppress the polymer's low molecular weight and unintended crosslinking reactions caused by heat, and is therefore insufficient to meet the heat resistance requirements at even higher temperatures, such as 190°C and above.

Patent No. 5682575

The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a novel diarylamine-based compound that can provide a surface-treated filler that exhibits excellent anti-aging properties for polymer materials, a surface-treated filler obtained using such a diarylamine-based compound, and a polymer composition containing such a surface-treated filler.

The inventors conducted research to achieve the above objective and discovered that the above objective could be achieved by using a specific diarylamine compound having a group capable of bonding to a hydroxyl group, thereby completing the present invention.

That is, according to the present invention, there is provided a diarylamine compound represented by the following general formula (1).
(A ¹ ) _m −A ² −(A ³ −A ⁴ ) _n (1)
(In the above general formula (1), A ¹ is a group capable of bonding to a hydroxyl group, A ² is an organic group having 1 to 30 carbon atoms and a valence of (m+n), which may have a substituent, A ³ is a divalent group containing a chemical single bond or a group selected from an ether group, a keto group, an ester group, and an amide group, A ⁴ is a monovalent group having a structure in which one hydrogen atom forming a carbon-hydrogen bond in a compound selected from the following formulas (2) to (8) has been removed, m is an integer of 1 to 5, and n is an integer of 1 to 5.)
(In the above formulas (2) to (8), a hydrogen atom bonded to a carbon atom forming an aromatic ring may be substituted with a monovalent organic group having 1 to 30 carbon atoms which may have a substituent.)

In the diarylamine compound of the present invention, ^A4 is preferably a group represented by the following formula (9).
(In the above formula (9), "*" indicates the bonding position with the group represented by ^A3 , and in the above formula (9), a hydrogen atom bonded to a carbon atom forming an aromatic ring may be substituted with a monovalent organic group having 1 to 30 carbon atoms.)
In the diarylamine compound of the present invention, A ¹ is preferably a silyl group having at least one alkoxy group.
In the diarylamine compound of the present invention, ^A3 is preferably an amide group.

Furthermore, according to the present invention, there is provided a surface-treated filler obtained by immobilizing the above diarylamine compound on the surface of a filler.
The surface-treated filler of the present invention is preferably one in which a diarylamine compound is fixed to the surface of silica.

Furthermore, according to the present invention, there is provided a polymer composition containing a polymer and the above-mentioned surface-treated filler.
In the polymer composition of the present invention, the polymer is preferably a rubber.
In the polymer composition of the present invention, the rubber is preferably an acrylic rubber.

The present invention provides novel diarylamine compounds that can provide surface-treated fillers that exhibit excellent anti-aging properties for polymer materials, surface-treated fillers obtained using such diarylamine compounds, and polymer compositions containing such surface-treated fillers.

<Diarylamine compounds>
The diarylamine compound of the present invention is a compound represented by the following general formula (1): When the diarylamine compound of the present invention is fixed to the surface of a filler and used as a surface-treated filler having the compound represented by the following general formula (1) fixed to the surface, the filler can exhibit excellent antiaging properties against polymer materials, and the surface-treated filler obtained using such a diarylamine compound of the present invention is suitably used as an antiaging agent.
(A ¹ ) _m −A ² −(A ³ −A ⁴ ) _n (1)
(In the above general formula (1), A ¹ is a group capable of bonding to a hydroxyl group, A ² is an organic group having 1 to 30 carbon atoms and a valence of (m+n), which may have a substituent, A ³ is a divalent group containing a chemical single bond or a group selected from an ether group, a keto group, an ester group, and an amide group, A ⁴ is a monovalent group having a structure in which one hydrogen atom forming a carbon-hydrogen bond in a compound selected from the following formulas (2) to (8) has been removed, m is an integer of 1 to 5, and n is an integer of 1 to 5.)
(In the above formulas (2) to (8), a hydrogen atom bonded to a carbon atom forming an aromatic ring may be substituted with a monovalent organic group having 1 to 30 carbon atoms which may have a substituent.)

In the above general formula (1), A ¹ is a group capable of bonding to a hydroxyl group, and may be any group capable of reacting with a hydroxyl group to form a chemical bond, and examples thereof include, but are not limited to, an alkoxysilyl group, an isocyanate group, an isothiocyanate group, an epoxy group, and a carboxyl group. A ¹ reacts with the hydroxyl group of the filler, thereby contributing to the immobilization of the diarylamine compound of the present invention to the filler surface. Among these, A ¹ is preferably an alkoxysilyl group, i.e., a silyl group having at least one alkoxy group, and more preferably an alkoxysilyl group represented by the following general formula (10):
-Si(R ¹ ) _x (OR ² ) _3-x (10)
In the above general formula (10), R ¹ is an alkyl group having 1 to 5 carbon atoms, preferably an alkyl group having 1 to 3 carbon atoms, more preferably an alkyl group having 1 to 2 carbon atoms, and even more preferably an alkyl group having 2 carbon atoms. R ² is an alkyl group having 1 to 5 carbon atoms, preferably an alkyl group having 1 to 3 carbon atoms, more preferably an alkyl group having 1 to 2 carbon atoms, and even more preferably an alkyl group having 2 carbon atoms. x is an integer from 0 to 2, preferably 0 or 1, and more preferably 0. When there are multiple ^{R 1s} and multiple R ^2s , the multiple R ^1s and multiple R ^2s may be the same or different.

Examples of the alkoxysilyl group constituting ^A1 include a trimethoxysilyl group, a triethoxysilyl group, a triisopropoxysilyl group, a methyldimethoxysilyl group, a dimethylmethoxysilyl group, an ethyldimethoxysilyl group, a diethylmethoxysilyl group, a methyldiethoxysilyl group, a dimethylethoxysilyl group, an ethyldiethoxysilyl group, a diethylethoxysilyl group, etc. Among these, from the viewpoint of more suitably immobilizing the filler on the surface, a trimethoxysilyl group, a triethoxysilyl group, and a triisopropoxysilyl group are preferred, and a triethoxysilyl group is particularly preferred.

^A2 is an (m+n)-valent organic group having 1 to 30 carbon atoms which may have a substituent. That is, ^A2 is an organic group having a valence corresponding to the numbers m and n in the above general formula (1). For example, when m = 1 and n = 1, ^A2 is a divalent organic group having 1 to 30 carbon atoms which may have a substituent. Examples of the (m+n)-valent organic group having 1 to 30 carbon atoms which may have a substituent include an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, or an aromatic hydrocarbon ring group having 6 to 30 carbon atoms which may have a substituent. When the (m+n)-valent organic group having 1 to 30 carbon atoms has a substituent, the position of the substituent can be any position. Examples of the substituent include halogen atoms such as a fluorine atom, a chlorine atom, and a bromine atom; alkoxy groups having 1 to 10 carbon atoms such as a methoxy group, an ethoxy group, and an isopropoxy group; a nitro group; a cyano group; and alkyl groups having 1 to 10 carbon atoms such as a methyl group, an ethyl group, and a t-butyl group.

Specific examples of the aliphatic hydrocarbon group constituting ^A2 include alkylene groups having 1 to 20 carbon atoms, such as methylene, ethylene, trimethylene, propylene, tetramethylene, butylene, pentamethylene, hexamethylene, octamethylene, and decamethylene. Specific examples of the aromatic hydrocarbon ring group constituting ^A2 include 1,2-phenylene, 1,3-phenylene, 1,4-phenylene, 1,4-naphthylene, 1,5-naphthylene, 2,6-naphthylene, and 4,4'-biphenylene. Of these, alkylene groups having 1 to 20 carbon atoms are preferred, and alkylene groups having 2 to 5 carbon atoms are more preferred.

In the general formula (1), ^A3 is a chemical single bond or a divalent group containing a group selected from an ether group, a keto group, an ester group, and an amide group. Specific examples of ^A3 include a chemical single bond, -O-, -C(=O)-, -C(=O)-O-, -O-C(=O)-, ^-NR3 -C(=O)-, -C(=O) ^-NR3- , -O-C(=O)-O-, ^-NR3 -C(=O) ^-O- , -O-C(=O) ^-NR3- , and -NR3-C(=O) ^-NR4- . ^R3 and ^R4 each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Among these, from the viewpoint of further enhancing the anti-aging effect, an amide group is preferred, -NR ³ -C(=O)- is more preferred, and -NH-C(=O)- is particularly preferred.

In the above general formula (1), m is an integer from 1 to 5, preferably 1 or 2, and more preferably 1. Also, n is an integer from 1 to 5, preferably 1 or 2, and more preferably 1.

In the above general formula (1), ^A4 is a monovalent group having a structure in which one hydrogen atom forming a carbon-hydrogen bond in a compound selected from the following formulas (2) to (8) has been removed.
In the above formulas (2) to (8), a hydrogen atom bonded to a carbon atom forming an aromatic ring may be substituted with a monovalent organic group having 1 to 30 carbon atoms which may have a substituent.
In the above, "*" indicates the position of the carbon atom in general formula (1) that bonds to ^A3 . That is, in the compounds represented by formulas (2) to (8) above, the carbon atom marked with "*" becomes a monovalent substituent having a structure in which one hydrogen atom has been removed, and a chemical bond can be formed with A3 at the carbon atom marked with "*" (or at any one of the carbon atoms marked with " ^* " in the case of a compound with multiple "*"s).

In the above formulas (2) to (8), the hydrogen atoms bonded to the carbon atoms forming the aromatic ring may be substituted with a monovalent organic group having 1 to 30 carbon atoms. Examples of such organic groups having 1 to 30 carbon atoms include alkyl groups having 1 to 30 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl; and cyclopropyl groups. cycloalkyl groups having 3 to 30 carbon atoms such as cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl; aryl groups having 6 to 30 carbon atoms such as phenyl, biphenyl, naphthyl, and anthranyl; and alkoxy groups having 1 to 30 carbon atoms such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, t-butoxy, n-pentyloxy, and n-hexyloxy.

The organic group having 1 to 30 carbon atoms may have a substituent, and the position of the substituent may be any position. Examples of the substituent include halogen atoms such as fluorine, chlorine, and bromine atoms; alkoxy groups having 1 to 10 carbon atoms such as methoxy, ethoxy, and isopropoxy; nitro groups; cyano groups; alkyl groups having 1 to 10 carbon atoms such as methyl, ethyl, and t-butyl groups; and the like.

Among the compounds represented by the above formulas (2) to (8), from the viewpoint of being able to further enhance the anti-aging effect, the compounds represented by the above formula (2), the compounds represented by the above formula (3), the compounds represented by the above formula (5), and the compounds represented by the above formula (6) are preferred, and the compounds represented by the above formula (2) are particularly preferred. That is, ^A4 is preferably a group represented by the following formula (9) (a compound represented by the above formula (2) in which the position of the carbon atom bonded to ^A3 is the position shown in the following formula (9)).
In the above formula (9), "*" indicates the bonding position with the group represented by ^A3 , and in the above formula (9), a hydrogen atom bonded to a carbon atom forming an aromatic ring may be substituted with a monovalent organic group having 1 to 30 carbon atoms, and examples of the monovalent organic group having 1 to 30 carbon atoms include those mentioned above.

Specific examples of the diarylamine compound represented by the above general formula (1) are not particularly limited, but the compound represented by the following general formula (11) is particularly suitable.
In the above general formula (11), ^R5 is an alkyl group having 1 to 5 carbon atoms, preferably an alkyl group having 1 to 3 carbon atoms, more preferably an alkyl group having 1 to 2 carbon atoms, and even more preferably an alkyl group having 2 carbon atoms; ^R6 is an alkyl group having 1 to 5 carbon atoms, preferably an alkyl group having 1 to 3 carbon atoms, more preferably an alkyl group having 1 to 2 carbon atoms, and even more preferably an alkyl group having 2 carbon atoms; p is an integer of 1 to 30, preferably an integer of 1 to 20, more preferably an integer of 2 to 5, and even more preferably 3; and q is an integer of 0 to 2, preferably 0 or 1, and more preferably 0.

The method for producing the diarylamine compound represented by the above general formula (1) is not particularly limited. For example, when the diarylamine compound represented by the above general formula (1) is a compound represented by the above general formula (11), the following method can be mentioned.

That is, first, as shown in the following reaction formula, trimellitic anhydride and 4-aminodiphenylamine are reacted in a solvent to obtain a reaction solution containing a compound represented by the following formula (12) and/or a compound represented by the following formula (13).

Next, the reaction solution containing the compound represented by formula (12) and/or the compound represented by formula (13) obtained by the above reaction is heated to proceed with the imidization reaction as shown in the following reaction formula, thereby obtaining a compound represented by formula (14) below.

The above imidization reaction is typically carried out in the presence of an acid catalyst or a base catalyst. Acids used as acid catalysts include, but are not limited to, inorganic acids such as hydrochloric acid, sulfuric acid, and phosphoric acid; and organic acids such as p-toluenesulfonic acid, 10-camphorsulfonic acid, and acetic acid. Bases used as base catalysts include, but are not limited to, tertiary amines such as triethylamine, diisopropylethylamine, and N-methylmorpholine; pyridines such as pyridine, picoline, lutidine, and 4-(dimethylamino)pyridine; and inorganic bases such as sodium hydroxide, potassium hydroxide, and potassium carbonate. The reaction between trimellitic anhydride and 4-aminodiphenylamine and the imidization reaction may proceed simultaneously.

Next, as shown in the reaction formula below, the compound represented by formula (14) obtained by the above reaction is reacted with an amino group-containing silane compound represented by general formula (15) below (in general formula (15) below, R ⁵ , R ⁶ , p, and q are the same as in general formula (11) above), thereby obtaining the compound represented by general formula (11) above.

Furthermore, for example, when the diarylamine compound represented by the above general formula (1) is a compound represented by the following general formula (16), the following method can be mentioned.
In the general formula (16), R ⁵ , R ⁶ , p, and q are the same as those in the general formula (11).

That is, as shown in the following reaction formula, trimellitic anhydride and 4,4'-diaminodiphenylamine are reacted in a solvent and imidization is promoted by heating to obtain a compound shown in the following formula (17). Note that the reaction and imidization of trimellitic anhydride and 4,4'-diaminodiphenylamine in the following reaction formula can be carried out in the same manner as in the case of the compound represented by the above general formula (11).

Next, as shown in the following reaction formula, the compound represented by formula (17) obtained by the above reaction is reacted with phthalic anhydride in a solvent, and imidization is promoted by heating to obtain a compound represented by formula (18). Note that the reaction and imidization of phthalic anhydride with the compound represented by formula (17) in the following reaction formula can be carried out in the same manner as in the case of the compound represented by general formula (11).

Next, the compound represented by the formula (18) obtained by the above reaction is reacted with an amino group-containing silane compound represented by the following general formula (15) (in the following general formula (15), R ⁵ , R ⁶ , p, and q are the same as in the general formula (16)), thereby obtaining the compound represented by the general formula (16).

[0062] Note that, in the above, examples have been given of production methods when the diarylamine compound represented by general formula (1) is the compound represented by general formula (11) above, and when it is the compound represented by general formula (16) above (i.e., when ^A4 is a group derived from the compound represented by formula (2) above, and when it is a group derived from the compound represented by formula (3) above). However, when ^A4 is a group derived from the compounds represented by formulas (4) to (8) above, the diarylamine compound can be produced, for example, by combining the method described in WO 2018/159459, WO 2011/058918, or WO 2011/093443 with the above method or a known synthesis method.

<Surface treatment filler>
The surface-treated filler of the present invention is a filler that has been surface-treated with the diarylamine compound represented by the general formula (1), which is obtained by fixing the diarylamine compound represented by the general formula (1) on the surface of a filler. When blended with a polymer material, the surface-treated filler of the present invention can exhibit an excellent antiaging effect on the polymer material, and is therefore suitable as an antiaging agent.

The filler used in the present invention is not particularly limited, but silica is preferred from the viewpoint of being able to suitably fix the diarylamine compound represented by the above general formula (1) to its surface.

Examples of silica include dry-process white carbon, wet-process white carbon, colloidal silica, and precipitated silica. Among these, wet-process white carbon, primarily composed of hydrous silicic acid, is preferred. Carbon-silica dual-phase fillers, in which silica is supported on the surface of carbon black, may also be used. These silicas may be used alone or in combination of two or more. The nitrogen adsorption specific surface area of the silica (measured by the BET method in accordance with ASTM D3037-81) is preferably 50 to 300 ^{m 2} /g, more preferably 80 to 220 ^{m 2} /g, and particularly preferably 100 to 170 m ² /g. The pH of the silica is preferably 5 to 10.

The method for immobilizing the diarylamine compound represented by the general formula (1) on the surface of the filler is not particularly limited, and any method capable of reacting a group capable of bonding to a hydroxyl group, which constitutes ^A1 in the diarylamine compound represented by the general formula (1), with a hydroxyl group present on the surface of the filler may be employed. For example, when the group capable of bonding to a hydroxyl group, which constitutes ^A1 in the diarylamine compound represented by the general formula (1), is an alkoxysilyl group, a method of mixing the diarylamine compound represented by the general formula (1) with the filler in the presence of an acid catalyst may be employed.

In the surface-treated filler of the present invention, the amount of the diarylamine compound represented by the general formula (1) fixed to the filler is not particularly limited, but is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 7 parts by weight, even more preferably 1 to 5 parts by weight, and particularly preferably 1.2 to 3 parts by weight, per 100 parts by weight of filler. By setting the amount of the diarylamine compound represented by the general formula (1) fixed to the filler within this range, the anti-aging effect on polymer materials can be further enhanced. Note that in the present invention, it is preferable to set the amount of the diarylamine compound represented by the general formula (1) fixed to the filler (or the state after the molecules have been detached, if the detachment of molecules occurs due to the fixation reaction) within the above range, per 100 parts by weight of filler.

<Polymer Composition>
The polymer composition of the present invention is obtained by blending the above-described surface-treated filler with a polymer. The surface-treated filler usually acts as an antioxidant for the polymer in the polymer composition of the present invention.

Examples of polymers used in the present invention include synthetic resins and rubbers. Synthetic resins can be used without particular limitations as long as they are used in applications requiring heat resistance, and examples include polyolefins, polystyrene-based resins, polyesters, polycarbonates, and polyamides. These synthetic resins may be used alone or in combination of two or more.

Any rubber may be used for applications requiring heat resistance, without particular limitations. Examples include rubbers containing conjugated diene units such as natural rubber, isoprene rubber, butadiene rubber, butyl rubber, chloroprene rubber, styrene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber (nitrile rubber), styrene-butadiene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, and acrylonitrile-styrene-butadiene copolymer rubber; acrylic rubber; hydrin rubber; and ethylene propylene rubber. These rubbers may contain hydroxyl groups, carboxyl groups, alkoxysilyl groups, amino groups, and epoxy groups. These rubbers may also be hydrogenated, such as hydrogenated acrylonitrile-butadiene copolymer rubber (hydrogenated nitrile rubber). These rubbers may be used alone or in combination of two or more, or may be used in combination with the synthetic resins listed above. Among these, acrylic rubber is particularly preferred because it has a significant effect of improving heat resistance when applied to acrylic rubber or hydrogenated nitrile rubber, which are required to have high heat resistance.

There are no particular limitations on the method for incorporating the surface-treated filler into the polymer, and examples include incorporating it into a polymer latex or polymer solution, as well as incorporating it in any step after precipitating the polymer by coagulating the polymer latex or polymer solution. For example, the filler may be incorporated during the production of polymer pellets, during the blending and kneading of various compounding ingredients, or during the molding step using a molding machine. The timing of incorporation can be selected as needed to ensure sufficiently uniform dispersion throughout the polymer.

The amount of surface-treated filler to be blended is preferably 20 to 90 parts by weight, more preferably 30 to 80 parts by weight, and even more preferably 40 to 70 parts by weight, per 100 parts by weight of polymer. By keeping the blending amount within this range, it is possible to obtain sufficient anti-aging effects while ensuring the reinforcing effect of the filler.

<Acrylic rubber>
Acrylic rubber, an example of a polymer constituting the polymer composition of the present invention, is a rubber having 50 to 100% by weight of (meth)acrylic acid ester monomer units, 10 to 0% by weight of crosslinkable monomer units, and, if necessary, 50 to 0% by weight of units of other monomers copolymerizable with the monomers that form these monomer units, and the physical properties of the rubber can be adjusted by adjusting the proportions of the monomer units that constitute the acrylic rubber. Note that, in the present invention, "(meth)acrylic" refers to acrylic and/or methacrylic.

Acrylic rubber is known for its excellent oil resistance, especially at high temperatures, and good heat resistance, and demand is increasing for its use in automotive hoses, oil seals, O-rings, and conveyor belts built into equipment and machinery.

The (meth)acrylic acid ester monomer that forms the (meth)acrylic acid ester monomer unit, which is the main component of acrylic rubber, is not particularly limited, but preferred examples include (meth)acrylic acid alkyl ester monomers and (meth)acrylic acid alkoxyalkyl ester monomers.

The (meth)acrylic acid alkyl ester monomer is not particularly limited, but is preferably an ester of an alkanol having 1 to 8 carbon atoms with (meth)acrylic acid. Specific examples include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate. Of these, ethyl (meth)acrylate and n-butyl (meth)acrylate are preferred, with ethyl acrylate and n-butyl acrylate being more preferred. These may be used alone or in combination of two or more.

The (meth)acrylic acid alkoxyalkyl ester monomer is not particularly limited, but is preferably an ester of an alkoxyalkyl alcohol having 2 to 8 carbon atoms with (meth)acrylic acid. Specific examples include methoxymethyl (meth)acrylate, ethoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-propoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, and 4-methoxybutyl (meth)acrylate. Of these, 2-ethoxyethyl (meth)acrylate and 2-methoxyethyl (meth)acrylate are preferred, with 2-ethoxyethyl acrylate and 2-methoxyethyl acrylate being particularly preferred. These may be used alone or in combination of two or more.

The content of (meth)acrylic acid ester monomer units in the acrylic rubber is 50 to 100% by weight, preferably 60 to 99.5% by weight, and more preferably 70 to 99.5% by weight. If the content of (meth)acrylic acid ester monomer units is too low, the weather resistance, heat resistance, and oil resistance of the resulting cross-linked rubber may be reduced.

The breakdown of the (meth)acrylic acid ester monomer units is preferably 30 to 100% by weight of (meth)acrylic acid alkyl ester monomer units and 70 to 0% by weight of (meth)acrylic acid alkoxyalkyl ester monomer units.

The crosslinkable monomer that forms the crosslinkable monomer unit is not particularly limited, but includes α,β-ethylenically unsaturated carboxylic acid monomers; monomers having halogen atoms or epoxy groups; diene monomers; and the like.

The α,β-ethylenically unsaturated carboxylic acid monomer is not particularly limited, but examples include α,β-ethylenically unsaturated monocarboxylic acids having 3 to 12 carbon atoms, α,β-ethylenically unsaturated dicarboxylic acids having 4 to 12 carbon atoms, and monoesters of α,β-ethylenically unsaturated dicarboxylic acids having 4 to 12 carbon atoms with alkanols having 1 to 8 carbon atoms. Examples of α,β-ethylenically unsaturated monocarboxylic acids having 3 to 12 carbon atoms include acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid, and cinnamic acid. Examples of α,β-ethylenically unsaturated dicarboxylic acids having 4 to 12 carbon atoms include butenedioic acids such as fumaric acid and maleic acid, itaconic acid, citraconic acid, and chloromaleic acid. Examples of monoesters of α,β-ethylenically unsaturated dicarboxylic acids having 4 to 12 carbon atoms and alkanols having 1 to 8 carbon atoms include butenedioic acid mono-chain alkyl esters such as monomethyl fumarate, monoethyl fumarate, monobutyl fumarate, monomethyl maleate, monoethyl maleate, and monobutyl maleate; butenedioic acid monoesters having an alicyclic structure such as monocyclopentyl fumarate, monocyclohexyl fumarate, monocyclohexenyl fumarate, monocyclopentyl maleate, monocyclohexyl maleate, and monocyclohexenyl maleate; and itaconic acid monoesters such as monomethyl itaconate, monoethyl itaconate, monobutyl itaconate, and monocyclohexyl itaconate. Among these, butenedioic acid mono-chain alkyl esters or butenedioic acid monoesters having an alicyclic structure are preferred, and monobutyl fumarate, monobutyl maleate, monocyclohexyl fumarate, and monocyclohexyl maleate are more preferred. These α,β-ethylenically unsaturated carboxylic acid monomers can be used alone or in combination of two or more. Among the above monomers, dicarboxylic acids may be copolymerized as anhydrides, and may be any monomers that hydrolyze to generate carboxyl groups during crosslinking.

Halogen atom-containing monomers include, but are not limited to, unsaturated alcohol esters of halogen-containing saturated carboxylic acids, (meth)acrylic acid haloalkyl esters, (meth)acrylic acid haloacyloxyalkyl esters, (meth)acrylic acid (haloacetylcarbamoyloxy)alkyl esters, halogen-containing unsaturated ethers, halogen-containing unsaturated ketones, halomethyl group-containing aromatic vinyl compounds, halogen-containing unsaturated amides, and haloacetyl group-containing unsaturated monomers. Examples of unsaturated alcohol esters of halogen-containing saturated carboxylic acids include vinyl chloroacetate, vinyl 2-chloropropionate, and allyl chloroacetate. Examples of (meth)acrylic acid haloalkyl esters include chloromethyl (meth)acrylate, 1-chloroethyl (meth)acrylate, 2-chloroethyl (meth)acrylate, 1,2-dichloroethyl (meth)acrylate, 2-chloropropyl (meth)acrylate, 3-chloropropyl (meth)acrylate, and 2,3-dichloropropyl (meth)acrylate. Examples of (meth)acrylic acid haloacyloxyalkyl esters include 2-(chloroacetoxy)ethyl (meth)acrylate, 2-(chloroacetoxy)propyl (meth)acrylate, 3-(chloroacetoxy)propyl (meth)acrylate, and 3-(hydroxychloroacetoxy)propyl (meth)acrylate. Examples of (meth)acrylic acid (haloacetylcarbamoyloxy)alkyl esters include 2-(chloroacetylcarbamoyloxy)ethyl (meth)acrylate and 3-(chloroacetylcarbamoyloxy)propyl (meth)acrylate. Examples of halogen-containing unsaturated ethers include chloromethyl vinyl ether, 2-chloroethyl vinyl ether, 3-chloropropyl vinyl ether, 2-chloroethyl allyl ether, and 3-chloropropyl allyl ether. Examples of halogen-containing unsaturated ketones include 2-chloroethyl vinyl ketone, 3-chloropropyl vinyl ketone, and 2-chloroethyl allyl ketone. Examples of halomethyl group-containing aromatic vinyl compounds include p-chloromethylstyrene and p-chloromethyl-α-methylstyrene. Examples of halogen-containing unsaturated amides include N-chloromethyl(meth)acrylamide, etc. Examples of haloacetyl group-containing unsaturated monomers include 3-(hydroxychloroacetoxy)propyl allyl ether, p-vinylbenzyl chloroacetic acid ester, etc.

Epoxy group-containing monomers are not particularly limited, but examples include epoxy group-containing (meth)acrylic acid esters and epoxy group-containing ethers. Epoxy group-containing (meth)acrylic acid esters include glycidyl (meth)acrylate, and epoxy group-containing ethers include allyl glycidyl ether.

Diene monomers include conjugated and non-conjugated diene monomers. Conjugated diene monomers include 1,3-butadiene, isoprene, and piperylene. Non-conjugated diene monomers include ethylidene norbornene, dicyclopentadiene, dicyclopentadienyl (meth)acrylate, and 2-dicyclopentadienylethyl (meth)acrylate.

These cross-linkable monomers can be used alone or in combination of two or more. The content of cross-linkable monomer units in the acrylic rubber is 0 to 10% by weight, preferably 0.5 to 7% by weight, and more preferably 0.5 to 5% by weight. If the content of cross-linkable monomer units is too high, the elongation of the resulting cross-linked rubber product may decrease and the compression set rate may increase.

Other monomers copolymerizable with the above-mentioned monomers are not particularly limited, but examples include aromatic vinyl monomers, α,β-ethylenically unsaturated nitrile monomers, monomers having two or more acryloyloxy groups, olefin-based monomers, and vinyl ether compounds.

Aromatic vinyl monomers include styrene, α-methylstyrene, and divinylbenzene. α,β-ethylenically unsaturated nitrile monomers include acrylonitrile and methacrylonitrile. Polyfunctional (meth)acrylic monomers include (meth)acrylic acid diesters of ethylene glycol and (meth)acrylic acid diesters of propylene glycol. Olefin monomers include ethylene, propylene, 1-butene, and 1-octene. Vinyl ether compounds include vinyl acetate, ethyl vinyl ether, and butyl vinyl ether. Among these, styrene, acrylonitrile, and methacrylonitrile are preferred, with acrylonitrile and methacrylonitrile being more preferred.

These copolymerizable other monomers can be used alone or in combination of two or more. The content of units of other monomers in the acrylic rubber is 0 to 50% by weight, preferably 0 to 39.5% by weight, and more preferably 0 to 29.5% by weight.

The acrylic rubber used in the present invention can be obtained by polymerizing the above-mentioned monomers. The polymerization reaction can be carried out using any of the following methods: emulsion polymerization, suspension polymerization, bulk polymerization, and solution polymerization. However, due to the ease of control of the polymerization reaction, it is preferable to use emulsion polymerization under atmospheric pressure, which is a commonly used method for producing conventional acrylic rubber.

Emulsion polymerization may be performed in a batch, semi-batch, or continuous manner. Polymerization is usually carried out at a temperature ranging from 0 to 70°C, preferably from 5 to 50°C.

The Mooney viscosity [ML1+4, 100°C] (polymer Mooney) of the acrylic rubber used in the present invention produced in this manner is preferably 10 to 80, more preferably 20 to 70, and particularly preferably 25 to 60.

<Other antioxidants>
Furthermore, the polymer composition of the present invention may contain, in addition to the polymer and the surface-treated filler as an antioxidant, other antioxidants other than the surface-treated filler.

The other antioxidants are not particularly limited, but a compound represented by the following general formula (19) is preferably used.
In the general formula (19), R ^a and R ^b each independently represent an organic group having 1 to 30 carbon atoms which may have a substituent. Z ^a and Z ^b each independently represent a chemical single bond or —SO ₂ —. r and s each independently represent 0 or 1, provided that at least one of r and s is 1.

In the above general formula (19), R ^a and R ^b each independently represent an organic group having 1 to 30 carbon atoms which may have a substituent.
R ^a and R The organic group having 1 to 30 carbon atoms constituting ^b is not particularly limited, and examples thereof include alkyl groups having 1 to 30 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl; cycloalkyl groups having 3 to 30 carbon atoms such as cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl; aryl groups having 6 to 30 carbon atoms such as phenyl, biphenyl, naphthyl, and anthranyl; and alkoxy groups having 1 to 30 carbon atoms such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, t-butoxy, n-pentyloxy, and n-hexyloxy.

The organic groups constituting the above-mentioned R ^a and R ^b may have a substituent, and the position of the substituent may be any position.
When the organic group is an alkyl group, such a substituent includes a halogen atom such as a fluorine atom, a chlorine atom, or a bromine atom; an alkoxy group having 1 to 10 carbon atoms such as a methoxy group, an ethoxy group, or an isopropoxy group; a nitro group; a cyano group; a phenyl group, a 4-methylphenyl group, a 2-chlorophenyl group, or another substituted phenyl group; and the like.
Furthermore, when the organic group is a cycloalkyl group or an aryl group, examples of the substituent include halogen atoms such as a fluorine atom, a chlorine atom, and a bromine atom; alkoxy groups having 1 to 10 carbon atoms such as a methoxy group, an ethoxy group, and an isopropoxy group; a nitro group; a cyano group; and alkyl groups having 1 to 10 carbon atoms such as a methyl group, an ethyl group, and a t-butyl group.
Furthermore, when the organic group is an alkoxy group, examples of the substituent include halogen atoms such as fluorine atoms, chlorine atoms, and bromine atoms; a nitro group; and a cyano group.
In addition, in the general formula (19), when the organic groups constituting R ^a and R ^b have a substituent, the number of carbon atoms of the substituent is not included in the number of carbon atoms of the organic group.

R ^a and R ^b are each preferably an optionally substituted alkyl group having 2 to 20 carbon atoms or an optionally substituted aryl group having 6 to 30 carbon atoms, more preferably an optionally substituted linear or branched alkyl group having 2 to 20 carbon atoms, or an optionally substituted phenyl group, or an optionally substituted naphthyl group, still more preferably an optionally substituted linear or branched alkyl group having 2 to 8 carbon atoms or an optionally substituted phenyl group, and particularly preferably an optionally substituted linear or branched alkyl group having 2 to 8 carbon atoms. Examples of these substituents include the same as those exemplified as the substituents of the optionally substituted alkyl group having 1 to 30 carbon atoms and the optionally substituted aryl group having 6 to 30 carbon atoms of the organic group.

Preferred specific examples of the organic group constituting R ^a and R ^b include an α-methylbenzyl group, an α,α-dimethylbenzyl group, a t-butyl group, a phenyl group, or a 4-methylphenyl group, and among these, an α,α-dimethylbenzyl group or a 4-methylphenyl group is more preferred, and an α,α-dimethylbenzyl group is even more preferred. These may be independent of each other.

In the general formula (19), Z ^a and Z ^b are each independently a chemical single bond or —SO ₂ —, and are preferably a chemical single bond.

Furthermore, in the above general formula (19), r and s are each independently 0 or 1, and at least one of r and s is 1. It is preferable that both r and s are 1.

In the present invention, the compound represented by the above general formula (19) is preferably any of the compounds represented by the following general formulas (20) to (22).
In the above general formulas (20) to (22), R ^a , R ^b , Z ^a and Z ^b are the same as those in the above general formula (19).

Of the compounds represented by the above general formulas (20) to (22), compounds represented by general formulas (20) and (22) are preferred, and compounds represented by general formula (22) are more preferred.

In the above general formulas (20) to (22), -Z ^a -R ^a and -Z ^b -R ^b are each preferably independently an α-methylbenzyl group, an α,α-dimethylbenzyl group, a t-butyl group, a phenylsulfonyl group, or a 4-methylphenylsulfonyl group, more preferably an α,α-dimethylbenzyl group or a 4-methylphenylsulfonyl group, and even more preferably an α,α-dimethylbenzyl group.

That is, in the present invention, in the above general formula (19), it is preferred that R ^a and R ^b each independently represent a linear or branched alkyl group having 2 to 8 carbon atoms which may have a substituent, Z ^a and Z ^b represent a chemical single bond, and r and s are 1.

The compound represented by the above general formula (19) can be produced by applying a known method for producing phenothiazine compounds to obtain a precursor phenothiazine compound, and then oxidizing the resulting compound.

Specifically, the compound represented by the above general formula (19) can be obtained by using a compound (phenothiazine) represented by the following general formula (23) as a starting material, by the reaction method described in WO 2011/093443, introducing substituents (-Z ^a -R ^a , -Z ^b -R ^b ) into the 1-, 3-, 6-, and/or 8-positions of the phenothiazine ring in general formula (23), and oxidizing S on the phenothiazine ring to convert it to —SO ₂ —.

In the general formula (19), R ^a and R ^b each independently represent an organic group having 1 to 30 carbon atoms which may have a substituent, and are preferably an aromatic group or cycloaliphatic group having 1 to 30 carbon atoms which may have a substituent.
The aromatic group having 1 to 30 carbon atoms is not particularly limited, but examples thereof include aromatic hydrocarbon groups such as a phenyl group, a biphenyl group, a naphthyl group, a phenanthryl group, and an anthranyl group, and aromatic heterocyclic groups such as a furyl group, a pyrrolyl group, a thienyl group, a pyridyl group, and a thiazolyl group.
The cycloaliphatic group having 1 to 30 carbon atoms is not particularly limited, and examples thereof include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, etc. Of these, it is preferable that R ^a and R ^b are each independently a phenyl group or a 4-methylphenyl group.
The organic groups constituting the above-mentioned R ^a and R ^b may have a substituent, and the position of the substituent may be any position. Examples of such a substituent include halogen atoms such as fluorine, chlorine, and bromine; alkoxy groups having 1 to 10 carbon atoms such as methoxy, ethoxy, and isopropoxy; nitro groups; cyano groups; and alkyl groups having 1 to 10 carbon atoms such as methyl, ethyl, and t-butyl groups.

The amount of the compound represented by general formula (19) in the polymer composition of the present invention is preferably 0.1 to 10 parts by weight, more preferably 0.3 to 5 parts by weight, and even more preferably 0.5 to 3 parts by weight, per 100 parts by weight of the polymer. By keeping the amount in this range, the anti-aging effect achieved by adding the compound represented by general formula (19) can be more appropriately enhanced.

Antiaging agents other than the compound represented by the general formula (19) above may also be blended. Examples of such antioxidants include monophenolic antioxidants such as 2,6-di-t-butyl-p-cresol, 2,6-di-t-butyl-4-ethylphenol, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-sec-butylphenol, 2-(1-methylcyclohexyl)-4,6-dimethylphenol, 2,6-di-t-butyl-α-dimethylamino-p-cresol, 2,4-bis[(octylthio)methyl]-o-cresol, styrenated phenol, and alkylated phenols; 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-methylenebis(2,6-di-t-butyl) Bis-, tris-, or polyphenol-based antioxidants such as 4,4'-thiobis(6-t-butyl-m-cresol), 2,2'-methylenebis(6-α-methylbenzyl-p-cresol), methylene-bridged polyhydric alkylphenols, 4,4'-butylidenebis(6-t-butyl-m-cresol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 2,2'-ethylidenebis(4,6-di-t-butylphenol), 1,1-bis-(4-hydroxyphenyl)cyclohexane, 2,2'-dihydroxy-3,3'-(α-methylcyclohexyl)-5,5'-dimethyldiphenylmethane, alkylated bisphenols, butylated reaction products of p-cresol and dicyclopentadiene, 2,5-di-t-butylhydroquinone, and 2,5-di-t-amylhydroquinone; phenolic antioxidants such as thiobisphenol-based antioxidants (4,4'-thiobis(6-t-butyl-o-cresol), 4,4'-thiobis(3-methyl-6-t-butylphenol), and bis(3,5-di-t-butyl-4-hydroxybenzyl) sulfide; phenolic antioxidants such as phenyl-α-naphthylamine, octylated diphenylamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, p-(p-toluenesulfonylamido)diphenylamine, p-isopropoxy diphenylamine, bis(phenyl isopropylidene)-4,4-diphenylamine, N,N'-diphenyl ethylenediamine, N,N'-diphenyl propylenediamine, N,N'-diphenyl-p-phenylenediamine, and N-isopropyl-N'-phenyl-p-phenylenediamine; Examples of aromatic secondary amine compounds that can be used include: aromatic secondary amine compounds such as diphenyldiamine, N,N'-di-2-naphthyl-p-phenyldiamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine, N,N'-bis(1-methylheptyl)-p-phenylenediamine, N,N-bis(1,4-dimethylpentyl)-p-phenylenediamine, 4-(α-phenylethyl)diphenylamine, 4,4'-bis(α-phenylethyl)diphenylamine, and 4,4'-bis(4-methylphenyl)sulfonyl)diphenylamine; and nickel dialkyldithiocarbamates such as nickel dimethyldithiocarbamate, nickel diethyldithiocarbamate, and nickel dibutyldithiocarbamate.

<Other additives, preparation method of polymer composition, etc.>
The polymer composition of the present invention may further contain other additives in addition to the polymer, the surface-treated filler, and other antioxidants such as the compound represented by the general formula (19) that are used as needed.

Other additives include additives commonly used in fields using synthetic polymer materials, such as reinforcing fillers such as carbon black, non-reinforcing fillers such as calcium carbonate and clay, light stabilizers, scorch inhibitors, plasticizers, processing aids, slip agents, adhesives, lubricants, flame retardants, mildew inhibitors, antistatic agents, colorants, silane coupling agents, crosslinking agents, crosslinking accelerators, crosslinking retarders, etc.
The amounts of these additives to be added are not particularly limited as long as they do not impair the object and effect of the present invention, and they can be added in amounts appropriate to the purpose of addition.

The polymer composition of the present invention can be prepared, for example, by mixing and kneading the components using a Banbury mixer or kneader, followed by further kneading using a kneading roll. The order in which the components are mixed is not particularly limited, but it is preferable to thoroughly mix the components that are resistant to reaction or decomposition by heat, and then mix components that are resistant to reaction or decomposition by heat, such as crosslinkers, in a short period of time at a temperature that will not cause reaction or decomposition.

For example, if a rubber such as acrylic rubber is used as the polymer constituting the polymer composition and a crosslinking agent is added, a crosslinked rubber product can be obtained by crosslinking the polymer. The crosslinked rubber product can be obtained by molding the desired shape using a molding machine, such as an extruder, injection molding machine, compressor, or roll, and then solidifying the shape of the crosslinked rubber product through a crosslinking reaction. In this case, crosslinking may be performed after molding or simultaneously with molding. The molding temperature is typically 10 to 200°C, preferably 25 to 120°C. The crosslinking temperature is typically 130 to 220°C, preferably 150 to 190°C, and the crosslinking time is typically 2 minutes to 10 hours, preferably 3 minutes to 6 hours. The heating method can be selected from methods commonly used for crosslinking rubber, such as press heating, steam heating, oven heating, and hot air heating.

Depending on the shape and size of the cross-linked rubber product, the surface may be cross-linked but not sufficiently cross-linked to the interior. Therefore, secondary cross-linking may be performed by further heating. The secondary cross-linking time varies depending on the heating method, cross-linking temperature, shape, etc., but is preferably 1 to 48 hours. The heating method and heating temperature may be selected as appropriate.

The cross-linked rubber obtained in this manner has excellent heat resistance. Therefore, by taking advantage of its properties, the cross-linked rubber obtained using the above rubber composition can be used in a variety of seals, including O-rings, packings, diaphragms, oil seals, shaft seals, bearing seals, mechanical seals, wellhead seals, seals for electrical and electronic equipment, and seals for pneumatic equipment; cylinder head gaskets attached to the joint between the cylinder block and cylinder head; rocker cover gaskets attached to the joint between the rocker cover and cylinder head; oil pan gaskets attached to the joint between the oil pan and cylinder block or transmission case; and fuel cell separator gaskets attached between a pair of housings sandwiching a unit cell comprising a positive electrode, an electrolyte plate, and a negative electrode. and gaskets for the top covers of hard disk drives; various belts; various hoses such as fuel hoses, turbo air hoses, oil hoses, radiator hoses, heater hoses, water hoses, vacuum brake hoses, control hoses, air conditioner hoses, brake hoses, power steering hoses, air hoses, marine hoses, risers, and flow lines; various boots such as CVJ boots, propeller shaft boots, constant velocity joint boots, and rack and pinion boots; and damping rubber parts such as cushioning materials, dynamic dampers, rubber couplings, air springs, and vibration isolators, and are particularly suitable for use in applications under severe high temperatures.

The present invention will be described in more detail below with reference to examples and comparative examples. In each example, "parts" is by weight unless otherwise specified.
Various physical properties were evaluated according to the following methods.

[Elongation at break before and after heating]
The rubber compositions obtained in each Example and Comparative Example were molded and crosslinked by press at 170°C for 20 minutes, and then further heated at 170°C for 4 hours to cause secondary crosslinking, thereby obtaining a sheet-like cross-linked rubber product. Next, dumbbell-shaped No. 3 test pieces were prepared from the obtained cross-linked rubber products, and the elongation at break before and after heating was measured for these test pieces in accordance with JIS K6251. The heating conditions were 190°C and 1008 hours, and the rate of change in elongation at break before and after heating was calculated according to the following formula. It can be determined that the smaller the rate of change in elongation at break, the more suppressed the deterioration due to heating.
Rate of change in breaking elongation (%) = [(breaking elongation after heating (%)) - (elongation before heating (%))] / (breaking elongation before heating (%))] × 100

[Synthesis Example 1]
In a four-neck reactor equipped with a condenser and a thermometer, 80 g of trimellitic anhydride and 76.7 g of 4-aminodiphenylamine were dissolved in 1 liter of acetic acid in a nitrogen stream. This solution was heated under reflux in an oil bath for 10 hours to cause a reaction. After completion of the reaction, the reaction solution was poured into 2 liters of water to precipitate a solid. The precipitated solid was then suction filtered. The residue was washed with water and then methanol, and then dried in a vacuum dryer to obtain 138.5 g of an intermediate represented by the following formula (14) in a yield of 92%. The structure of the obtained intermediate was identified by ₁ H-NMR. ₁ H-NMR (500MHz, THF-d8, TMS, δppm): 6.97 (t, 1H, J = 7.0Hz), 7.24-7.28 (m, 4H), 7.33-7.36 (m, 2 H), 7.40-7.42 (m, 2H), 7.68 (s, 1H), 8.11 (d, 1H, J=8.5Hz), 8.56-8.58 (m, 2H), 12.20 (bs, 1H).

[Synthesis Example 2]
In a four-neck reactor equipped with a thermometer, 5.38 g of the intermediate represented by formula (14) obtained in Synthesis Example 1 and 6.64 g of 3-aminopropyltriethoxysilane were dissolved in 400 mL of tetrahydrofuran (THF) under a nitrogen stream. This solution was cooled to 0°C in an ice bath, and 2.88 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (WSC) and 2.30 g of 1-hydroxybenzotriazole monohydrate were added. The reaction was then carried out at room temperature for 15 hours. After completion of the reaction, tetrahydrofuran was distilled off, and 200 mL of ethyl acetate and 100 mL of water were added. The organic layer was separated using a separatory funnel. The organic layer was concentrated and dried, and the resulting solid was purified by alumina column chromatography (chloroform:methanol = 50:1) to obtain 5.40 g of the compound represented by formula (24) below in a 64% yield. The structure of the resulting compound was identified by ¹ H-NMR. ¹ H-NMR (500MHz, CDCl3, TMS, δppm): 8.29 (m, 2H), 8.01 (d, 1H, J = 8.5Hz ), 7.30 (m, 4H), 7.15 (m, 4H), 7.00 (t, 1H, J=7.5Hz), 6.92 (t, 1H, J=5. 5Hz), 5.88 (s, 1H), 3.86 (q, 6H, J=7.0Hz), 3.52 (q, 2H, J=6.5Hz), 1,8 2 (quin, 2H, J=7.0Hz), 1.23 (t, 9H, J=7.0Hz), 0.75 (t, 2H, J=7.5Hz).

[Synthesis Example 3]
In a recovery flask, 0.96 g of the compound represented by formula (24) obtained in Synthesis Example 2 was dissolved in 640 mL of methanol. To this solution, 40 g of silica (trade name "Nipsil ER," manufactured by Tosoh Silica Corporation, specific surface area 70-120 ^{m 2} /g) and 160 mL of 0.2 wt % aqueous acetic acid solution were added, and the mixture was stirred at room temperature for 72 hours. The solvent was then removed by distillation, and the mixture was placed in a tray and allowed to air dry for 24 hours. The mixture was then heat-treated in an oven at 120°C for 24 hours, and then allowed to cool for 24 hours, thereby producing surface-treated silica in which the compound represented by formula (24) was fixed to the silica surface. The surface-treated silica was prepared by reacting 2.4 parts of the compound represented by formula (24) with 100 parts of silica (taking into account the ethanol molecules that were eliminated, 1.8 parts of the compound represented by formula (24) was reacted).

[Synthesis Example 4]
50.0 g of phenothiazine was added to a three-neck reactor equipped with a thermometer in a nitrogen stream and dissolved in 200 ml of toluene. Next, 59.31 g of α-methylstyrene and 1.19 g of p-toluenesulfonic acid monohydrate were added to this solution and reacted at 80°C for 1 hour. The reaction solution was then returned to room temperature, and 48 ml of acetic acid and 85.34 g of 30 wt% hydrogen peroxide solution were added, followed by a further reaction at 80°C for 2 hours. After the reaction, the resulting reaction solution was returned to room temperature and then poured into 630 ml of methanol to precipitate crystals. The precipitated crystals were then filtered and rinsed with 320 ml of methanol, yielding 85.7 g of the compound represented by the following formula (25) in a 73% yield. The structure of the resulting compound was identified by ¹ H-NMR. ^1H -NMR (500MHz, DMSO-d6, TMS, δppm): 1.67 (s, 12H), 7.15-7.32 (m, 12H), 7.43 (dd, 2H, J = 9.0, 2.0Hz), 7.68 (d, 2H, J=1.5Hz), 10.84 (s, 1H).

[Example 1]
100 parts of acrylic rubber (trade name "Hytemp AR212HR", manufactured by Zeon Corporation), 50.9 parts of the surface-treated silica obtained in Synthesis Example 3 (surface-treated silica having a compound represented by the above formula (24) fixed to the silica surface), 1 part of a silane coupling agent (trade name "KBM-403", manufactured by Shin-Etsu Silicones Co., Ltd.), 2 parts of stearic acid, 1 part of an ester wax (trade name "Greg G8205", manufactured by Dainippon Ink Co., Ltd.), and 1 part of the compound represented by the above formula (25) obtained in Synthesis Example 4 were kneaded at 50°C using an open roll, and then hexamethylenediamine carbamate (trade name "Diak No. 1", manufactured by DuPont Dow Chemical Co., Ltd.) was added as a crosslinking agent. 0.5 parts of di-o-tolylguanidine (trade name "Noccela DT", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) as a crosslinking accelerator were added, and the mixture was kneaded at 50°C with an open roll to obtain a rubber composition. The obtained rubber composition was then evaluated for elongation at break before and after heating according to the method described above. The results are shown in Table 1.

[Comparative Example 1]
A rubber composition was produced in the same manner as in Example 1, except that 50 parts of silica (trade name "Nipsil ER", manufactured by Tosoh Silica Corporation) was used instead of 50.9 parts of the surface-treated silica obtained in Synthesis Example 2, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 2]
A rubber composition was produced in the same manner as in Example 1, except that 50.9 parts of the surface-treated silica obtained in Synthesis Example 2 was replaced with 50 parts of silica (trade name "Nipsil ER", manufactured by Tosoh Silica Corporation), and 1.2 parts of the compound represented by formula (24) obtained in Synthesis Example 2 was used as is, and evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

As shown in Table 1, the cross-linked rubber obtained using an acrylic rubber blended with surface-treated silica in which the compound represented by the above formula (24) is fixed to the surface of the silica had a high breaking elongation after heating, and the rate of change in breaking elongation before and after heating was also small, meaning that deterioration due to heating was effectively suppressed (Example 1).
On the other hand, in both cases where silica was blended in place of the surface-treated silica and where surface-treated silica was blended together with silica, the cross-linked rubber products obtained had a small breaking elongation after heating, and the rate of change in breaking elongation before and after heating was also large, indicating that they were significantly deteriorated by heating (Comparative Examples 1 and 2).

Claims (7)

A diarylamine compound represented by the following general formula (1):
(A ¹ ) _m −A ² −(A ³ −A ⁴ ) _n (1)
(In the above general formula (1), A ¹ is a silyl group having at least one alkoxy group, A ² is an alkylene group having 1 to 20 carbon atoms, A ³ is an amide group, A ⁴ is a group represented by the following formula (3) or (9), m is an integer of 1 to 5, and n is an integer of 1 to 5.)
(In the above formulas (3) and (9), "*" indicates the bonding position with the group represented by ^A3 , and in the above formulas (3) and (9), a hydrogen atom bonded to a carbon atom forming an aromatic ring may be substituted with an alkyl group having 1 to 30 carbon atoms which may have a substituent, a cycloalkyl group having 3 to 30 carbon atoms which may have a substituent, an aryl group having 6 to 30 carbon atoms which may have a substituent, or an alkoxy group having 1 to 30 carbon atoms which may have a substituent , and the substituent is a halogen atom, a nitro group, or a cyano group .) The diarylamine compound according to claim 1, wherein ^A4 is a group represented by the formula (9). A surface-treated filler having the diarylamine compound according to claim 1 or 2 immobilized on the surface of the filler. A surface-treated filler in which the diarylamine compound according to claim 1 or 2 is immobilized on the surface of silica. A polymer composition containing a polymer and the surface-treated filler described in claim 3 or 4. The polymer composition according to claim 5, wherein the polymer is rubber. The polymer composition according to claim 6, wherein the rubber is an acrylic rubber.