Heat-treatment oil composition

Abstract

The present invention addresses the problem of providing a heat-treatment oil composition that, even when using a sulfur compound which has poor effects for achieving good brightness in a metal material after a heat-treatment such as quenching, can achieve a good brightness, and that, moreover, has excellent oxidation stability. The problem was solved by providing a heat-treatment oil composition containing: one or more base oils (A) selected from the group consisting of a mineral oil (A1), a synthetic oil (A2), and a plant oil (A3); a sulfur compound (B); and a carboxylic acid compound (C). The sulfur compound (B) comprises a specific sulfide, and the carboxylic acid compound (C) is one or more selected from a compound having at least one carboxy group and an anhydride thereof.

Description

Heat-treated oil composition

[0001] The present invention relates to a heat-treating oil composition.

[0002] Metallic materials such as steel are often subjected to heat treatments such as quenching, tempering, annealing, and normalizing to improve their properties. Among these heat treatments, quenching is a process in which a heated metallic material is immersed in a coolant to transform it into a predetermined quenched structure. Quenching makes the metallic material very hard and improves its mechanical strength.

[0003] Heat treatment oil compositions are widely used as coolants for quenching. In addition to their performance as coolants, heat treatment oil compositions are also required to maintain the surface gloss of metal materials before quenching after quenching, in order to increase the commercial value of the metal materials after quenching. In other words, heat treatment oil compositions are required to have the performance of improving the brightness of metal materials after quenching.

[0004] As such a heat-treated oil composition, for example, a heat-treated oil composition using a base oil in which at least one of a mineral oil and a synthetic oil having a sulfur content of 300 ppm or less is blended with at least one of sulfur and a sulfur compound to adjust the total sulfur content to 3 to 1,000 ppm has been proposed (see, for example, Patent Document 1).

[0005] Japanese Patent Application Publication No. 7-70632

[0006] However, as a result of intensive research by the present inventors, it was found that some of the sulfur compounds listed in Patent Document 1 (e.g., diphenyl disulfide) are less effective at improving the luster of metal materials after quenching. From the perspective of making various sulfur compounds widely available, it is considered desirable to establish a formulation for a heat treatment oil composition that can improve luster even when using a sulfur compound that is less effective at improving the luster of metal materials after quenching. Furthermore, it is also desirable for the heat treatment oil composition to have excellent oxidation stability, assuming contact with air when used in an open oil tank.

[0007] Therefore, the present invention aims to provide a heat treatment oil composition that can improve the luster of metal materials after heat treatment such as quenching, even when a sulfur compound that is less effective in improving the luster of metal materials is used, and that also has excellent oxidation stability.

[0008] According to the present invention, the following items [1] to [3] are provided: [1] A heat treatment oil composition comprising one or more base oils (A) selected from the group consisting of mineral oils (A1), synthetic oils (A2), and vegetable oils (A3), a sulfur compound (B), and a carboxylic acid compound (C), wherein the sulfur compound (B) comprises one or more compounds selected from the group consisting of sulfides (B1) represented by the following general formula (b1), sulfides (B2) represented by the following general formula (b2), sulfides (B3) represented by the following general formula (b3), and sulfides (B4) represented by the following general formula (b4), and the carboxylic acid compound (C) is one or more compounds selected from the group consisting of compounds having at least one carboxy group and anhydrides thereof. [In the general formula (b1), Ar １１ represents an aryl group having 6 to 15 carbon atoms and at least a hydroxyl group. １１ represents a substituted or unsubstituted hydrocarbon group (X1). The hydrocarbon group (X1) represents an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, a cycloalkenyl group having 3 to 15 carbon atoms, a cycloalkylalkyl group having 4 to 15 carbon atoms, a cycloalkenylalkyl group having 4 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, or an arylalkyl group having 7 to 15 carbon atoms. In the general formula (b2), Ar １２ is an arylene group having 6 to 15 carbon atoms and at least a hydroxyl group. １２ and R １３each independently represents a substituted or unsubstituted hydrocarbon group (X2). The hydrocarbon group (X2) represents an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, a cycloalkenyl group having 3 to 15 carbon atoms, a cycloalkylalkyl group having 4 to 15 carbon atoms, a cycloalkenylalkyl group having 4 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, or an arylalkyl group having 7 to 15 carbon atoms. In the general formula (b3), Ar １３ represents an aryl group having 6 to 15 carbon atoms and at least a hydroxyl group. １４ represents a substituted or unsubstituted aryl group having 6 to 15 carbon atoms. １５ and Ar １６ and each independently represent a substituted or unsubstituted aryl group having 6 to 15 carbon atoms.] [2] A method for using the heat treatment oil composition according to [1] above as a quenching oil or tempering oil. [3] A method for producing a heat treatment oil composition, comprising the step of mixing one or more base oils (A) selected from the group consisting of mineral oils (A1), synthetic oils (A2), and vegetable oils (A3), with a sulfur compound (B), and a carboxylic acid compound (C), wherein the sulfur compound (B) comprises one or more selected from the group consisting of sulfides (B1) represented by the following general formula (b1): [In the general formula (b1), Ar １１ R each independently represents an aryl group having 6 to 15 carbon atoms and at least a hydroxyl group. １１ represents a substituted or unsubstituted hydrocarbon group (X1). The hydrocarbon group (X1) represents an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, a cycloalkenyl group having 3 to 15 carbon atoms, a cycloalkylalkyl group having 4 to 15 carbon atoms, a cycloalkenylalkyl group having 4 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, or an arylalkyl group having 7 to 15 carbon atoms. In the general formula (b2), Ar１２ represents an arylene group having 6 to 15 carbon atoms and at least a hydroxyl group. １２ and R １３ each independently represents a substituted or unsubstituted hydrocarbon group (X2). The hydrocarbon group (X2) represents an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, a cycloalkenyl group having 3 to 15 carbon atoms, a cycloalkylalkyl group having 4 to 15 carbon atoms, a cycloalkenylalkyl group having 4 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, or an arylalkyl group having 7 to 15 carbon atoms. In the general formula (b3), Ar １３ represents an aryl group having 6 to 15 carbon atoms and at least a hydroxyl group. １４ represents a substituted or unsubstituted aryl group having 6 to 15 carbon atoms. １５ and Ar １６ each independently represents a substituted or unsubstituted aryl group having 6 to 15 carbon atoms.

[0009] According to the present invention, even when a sulfur compound that is less effective in improving the luster of metal materials after heat treatment such as quenching is used, it is possible to provide a heat treatment oil composition that can improve the luster and also has excellent oxidation stability.

[0010] 1 is a diagram showing the positions of the "ends" and "contact parts" where visual observation was performed for the test pieces used in the examples. 2 is a photograph, substituted for a drawing, showing the state of the test pieces after a quenching test using the heat treatment oil compositions of Examples 1 to 4 and Comparative Examples 1 to 7. 3 is a photograph, substituted for a drawing, showing the state of the test pieces after a quenching test using the heat treatment oil compositions (new oils) of Examples 5 to 8 and Comparative Examples 8 to 9.

[0011] In this specification, for preferred numerical ranges (e.g., ranges of content, etc.), the lower limit and upper limit values ​​described in stages can be independently combined. For example, the description "preferably 10 to 90, more preferably 30 to 60" can be combined with the "preferable lower limit (10)" and the "more preferable upper limit (60)" to form "10 to 60." Furthermore, unless otherwise specified, the numerical range "lower limit to upper limit" described in this specification means not less than the lower limit and not more than the upper limit. In this specification, the numerical values ​​in the examples are numerical values ​​that can be used as upper or lower limits. In this specification, "kinematic viscosity at 40°C" is also referred to as "40°C kinematic viscosity."

[0012] [Embodiments of Heat Treatment Oil Composition] The heat treatment oil composition of this embodiment contains one or more base oils (A) selected from the group consisting of mineral oils (A1), synthetic oils (A2), and vegetable oils (A3), a sulfur compound (B), and a carboxylic acid compound (C). The sulfur compound (B) includes one or more compounds selected from the group consisting of sulfides (B1) represented by the following general formula (b1), sulfides (B2) represented by the following general formula (b2), sulfides (B3) represented by the following general formula (b3), and sulfides (B4) represented by the following general formula (b4). The carboxylic acid compound (C) is one or more compounds selected from the group consisting of compounds having at least one carboxy group and their anhydrides. [In the general formula (b1), Ar １１ represents an aryl group having 6 to 15 carbon atoms and at least a hydroxyl group. １１ represents a substituted or unsubstituted hydrocarbon group (X1). The hydrocarbon group (X1) represents an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, a cycloalkenyl group having 3 to 15 carbon atoms, a cycloalkylalkyl group having 4 to 15 carbon atoms, a cycloalkenylalkyl group having 4 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, or an arylalkyl group having 7 to 15 carbon atoms. In the general formula (b2), Ar １２ represents an arylene group having 6 to 15 carbon atoms and at least a hydroxyl group. １２ and R１３ each independently represents a substituted or unsubstituted hydrocarbon group (X2). The hydrocarbon group (X2) represents an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, a cycloalkenyl group having 3 to 15 carbon atoms, a cycloalkylalkyl group having 4 to 15 carbon atoms, a cycloalkenylalkyl group having 4 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, or an arylalkyl group having 7 to 15 carbon atoms. In the general formula (b3), Ar １３ represents an aryl group having 6 to 15 carbon atoms and at least a hydroxyl group. １４ represents a substituted or unsubstituted aryl group having 6 to 15 carbon atoms. １５ and Ar １６ each independently represents a substituted or unsubstituted aryl group having 6 to 15 carbon atoms.

[0013] The present inventors have conducted extensive research to solve the above-mentioned problems. As a result, they have found that the above-mentioned problems can be solved by combining a sulfur compound (B), which has a poor effect of improving the brilliance of metal materials after heat treatment such as quenching, with a carboxylic acid compound (C). According to the inventors' research, no brilliance-improving effect was observed when only the carboxylic acid compound (C) was blended with the base oil (A). From this, it is presumed that in the present invention, by using the sulfur compound (B) and the carboxylic acid compound (C) in combination, some kind of interaction occurs between these compounds, thereby bringing out the brilliance-improving effect of the sulfur compound (B), thereby achieving the effects of the present invention.

[0014] The heat-treated oil composition of this embodiment may be composed only of the base oil (A), the sulfur compound (B), and the carboxylic acid compound (C), but may also contain other components in addition to the base oil (A), the sulfur compound (B), and the carboxylic acid compound (C) as long as the effects of the present invention are not impaired. In this embodiment, the total content of the base oil (A), the sulfur compound (B), and the carboxylic acid compound (C) is preferably 75% by mass to 100% by mass, more preferably 80% by mass to 100% by mass, even more preferably 85% by mass to 100% by mass, still more preferably 90% by mass to 100% by mass, and even more preferably 95% by mass to 100% by mass, based on the total amount of the heat-treated oil composition.

[0015] Each component contained in the heat-treated oil composition of the present invention will be described in detail below.

[0016] <Base oil (A)> The heat-treated oil composition of this embodiment contains base oil (A). The base oil (A) is one or more selected from the group consisting of mineral oil (A1), synthetic oil (A2), and vegetable oil (A3). The mineral oil (A1), synthetic oil (A2), and vegetable oil (A3) will be described in detail below.

[0017] (Mineral oil (A1)) As the mineral oil (A1), any mineral oil commonly used in heat-treated oil compositions can be used without any particular limitation. Specific examples of the mineral oil (A1) include atmospheric residue obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate crude oil, naphthenic crude oil, etc.; distillates obtained by vacuum distillation of these atmospheric residues; mineral oils obtained by subjecting the distillates to one or more treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining; wax isomerized mineral oil, etc.

[0018] The mineral oil (A1) is preferably a highly refined mineral oil whose sulfur content has been reduced by performing a refining process including at least one selected from hydrocracking and hydrorefining. The sulfur content of the highly refined mineral oil is preferably less than 10 ppm by mass, more preferably less than 5 ppm by mass, and even more preferably less than 3 ppm by mass, based on the total amount of the highly refined mineral oil.

[0019] The mineral oil (A1) may be bright stock having a low sulfur content. In this specification, the term "bright stock" refers to a high-viscosity mineral oil (kinematic viscosity at 40°C: 350 mmHg) obtained by subjecting a crude oil such as paraffinic crude oil, intermediate crude oil, or naphthenic crude oil to atmospheric distillation to obtain atmospheric residual oil, followed by deasphalting the distillate to obtain deasphalted oil, and then subjecting the deasphalted oil to one or more refining treatments selected from solvent refining, hydrorefining, and the like. ２ / s ~ 550 mm ２ The low-sulfur bright stock is preferably a hydrorefined product, and the sulfur content is preferably less than 10 ppm by mass, more preferably less than 5 ppm by mass, and even more preferably less than 3 ppm by mass, based on the total amount of the bright stock. Preferably, the low-sulfur bright stock is classified as Group II in the API category.

[0020] The mineral oil (A1) may be used alone or in combination of two or more.

[0021] (Synthetic Oil (A2)) As the synthetic oil (A2), any synthetic oil commonly used in heat treatment oil compositions can be used without particular limitation. Specific examples of the synthetic oil (A2) include poly-α-olefins, polyphenyl ethers, alkylbenzenes, alkylnaphthalenes, polyphenyl hydrocarbons, ester oils (for example, fatty acid esters of polyhydric alcohols such as neopentyl glycol, trimethylolpropane, and pentaerythritol), glycol-based synthetic oils, and GTL base oils obtained by isomerizing wax produced from natural gas by the Fischer-Tropsch process or the like (GTL wax (Gas To Liquids WAX)). Among these, GTL base oils are preferred. One type of synthetic oil (A2) may be used alone, or two or more types may be used in combination.

[0022] (Vegetable oil (A3)) As the vegetable oil (A3), any vegetable oil commonly used in heat treatment oil compositions can be used without any particular restrictions. Specific examples of the vegetable oil (A3) include linseed oil, safflower oil, sunflower oil, soybean oil, corn oil, cottonseed oil, sesame oil, olive oil, castor oil, peanut oil, coconut oil, palm kernel oil, palm oil, coconut oil, rapeseed oil, and rice bran oil. One type of vegetable oil (A3) may be used alone, or two or more types may be used in combination.

[0023] (Preferred Aspects of Base Oil (A)) In this embodiment, the base oil (A) may be one or more selected from the group consisting of mineral oil (A1), synthetic oil (A2), and vegetable oil (A3), but is preferably one or more selected from the group consisting of mineral oil (A1) and synthetic oil (A2). Furthermore, the base oil (A) preferably contains a mineral oil (A1). When the base oil (A) contains a mineral oil (A1), the content of the mineral oil (A1) is preferably 20% by mass to 100% by mass, more preferably 30% by mass to 100% by mass, even more preferably 40% by mass to 100% by mass, still more preferably 50% by mass to 100% by mass, even more preferably 60% by mass to 100% by mass, still more preferably 70% by mass to 100% by mass, even more preferably 80% by mass to 100% by mass, and even more preferably 90% by mass to 100% by mass, based on the total amount of the base oil (A).

[0024] (Kinematic viscosity at 40°C of base oil (A)) The kinematic viscosity at 40°C of the base oil (A) used in this embodiment is preferably 5 mm ２ / s ~ 600 mm ２ / s, more preferably 6 mm ２ / s ~ 570 mm ２ / s, more preferably 7 mm ２ / s ~ 540 mm ２ / s, and even more preferably 8 mm ２ / s ~ 520 mm ２ / s, and even more preferably 9 mm ２ / s ~ 500 mm ２ The kinematic viscosity of the base oil (A) at 40°C is 5 mm ２On the other hand, if the kinematic viscosity at 40°C of the base oil (A) is 600 mm / s or more, it is easy to obtain a heat-treated oil composition that suppresses the generation of oily smoke. ２ / s or less, it is easy to obtain a heat-treated oil composition with good cooling performance. In this specification, the 40 ° C. kinematic viscosity is a value measured in accordance with JIS K2283:2000. In addition, in the heat-treated oil composition of this embodiment, it is preferable to use a mixture of multiple base oils with different 40 ° C. kinematic viscosities, taking into account the ease of adjusting the 40 ° C. kinematic viscosity of the base oil (A).

[0025] (Content of base oil (A)) In the heat-treated oil composition of this embodiment, the content of base oil (A) is preferably 80.0 mass% or more, more preferably 82.0 mass% or more, and even more preferably 83.0 mass% or more, based on the total amount of the heat-treated oil composition. It is also preferably 98.99 mass% or less. The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, it is preferably 80.0 mass% to 98.99 mass%, more preferably 82.00 mass% to 98.99 mass%, and even more preferably 83.0 mass% to 98.99 mass%.

[0026] <Sulfur Compound (B)> The heat treatment oil composition of this embodiment contains a sulfur compound (B). The sulfur compound (B) is poor at improving the luster of metal materials after heat treatment such as quenching. However, by using it in combination with a carboxylic acid compound (C), the luster of metal materials after heat treatment such as quenching can be improved. In this embodiment, the sulfur compound (B) includes one or more selected from the group consisting of sulfides (B1), sulfides (B2), sulfides (B3), and sulfides (B4). In this embodiment, the sulfur compound (B) may consist of only one or more selected from the group consisting of sulfides (B1), sulfides (B2), sulfides (B3), and sulfides (B4). However, the sulfur compound (B) may contain sulfur compounds other than the sulfides (B1), sulfides (B2), sulfides (B3), and sulfides (B4) as long as the effects of the present invention are not impaired. In the present embodiment, the one or more selected from the group consisting of sulfides (B1), sulfides (B2), sulfides (B3), and sulfides (B4) encompasses the following embodiments.Sulfides (B1) only Sulfides (B2) only Sulfides (B3) only Sulfides (B4) only A combination of sulfides (B1) and sulfides (B2) A combination of sulfides (B1) and sulfides (B3) A combination of sulfides (B1) and sulfides (B4) A combination of sulfides (B2) and sulfides (B3) A combination of sulfides (B2) and sulfides (B4) A combination of sulfides (B3) and sulfides (B4) A combination of sulfides (B1), sulfides (B2) and sulfides (B3) A combination of sulfides (B1), sulfides (B2) and sulfides (B4) Combination of sulfides (B1), sulfides (B3), and sulfides (B4) Combination of sulfides (B2), sulfides (B3), and sulfides (B4) Combination of sulfides (B1), sulfides (B2), sulfides (B3), and sulfides (B4) In this embodiment, the content of one or more compounds selected from the group consisting of sulfides (B1), sulfides (B2), sulfides (B3), and sulfides (B4) is preferably 70% by mass to 100% by mass, more preferably 80% by mass to 100% by mass, even more preferably 90% by mass to 100% by mass, and still more preferably 95% by mass to 100% by mass, based on the total amount of sulfur compound (B). Hereinafter, sulfides (B1), sulfides (B2), sulfides (B3), and sulfides (B4) will be described in detail.

[0027] (Sulfides (B1)) The sulfides (B1) are compounds represented by the following general formula (b1).

[0028] In the general formula (b1), Ar １１is an aryl group having 6 to 15 carbon atoms and at least a hydroxyl group. Compounds having a structure in which a sulfur atom and an aryl group are bonded via a methylene group, such as the compound represented by general formula (b1), tend to be less effective in improving the luster of metal materials after heat treatments such as quenching. However, by using them in combination with a carboxylic acid compound (C), the luster of metal materials after heat treatments such as quenching can be improved. Note that when the number of carbon atoms in the aryl group exceeds 15, the luster of metal materials after heat treatments such as quenching may not be improved even when combined with a carboxylic acid compound (C).

[0029] In the general formula (b1), Ar １１ Examples of the aryl group having 6 to 15 carbon atoms constituting the formula (I) include a phenyl group, a biphenyl group, a naphthyl group, a phenanthryl group, a fluorenyl group, and an anthryl group. Note that the "6 to 15 carbon atoms" in the "aryl group having 6 to 15 carbon atoms" means that the ring carbon atoms are 6 to 15. From the viewpoint of more easily exerting the effect of the combination with the carboxylic acid compound (C), the number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6.

[0030] In the general formula (b1), Ar １１The aryl group having 6 to 15 carbon atoms constituting the formula (I) has at least one hydroxyl group. If the aryl group does not have a hydroxyl group, the oxidation stability of the heat treatment oil composition may be insufficient. Here, the aryl group may further have a substituent other than a hydroxyl group, or may not have a substituent other than a hydroxyl group. Examples of the substituent include a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a hydroxyl group, an amino group, a nitro group, an amide group, a benzamide group, a carboxy group, a residue obtained by removing a hydrogen atom from one of the hydroxyl groups of a dicarboxylic acid, and a halogen atom. The monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms is preferably a linear or branched alkyl group having 3 to 10 carbon atoms, more preferably a branched alkyl group having 3 to 10 carbon atoms. The halogen atom is, for example, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom, and preferably a chlorine atom. The number of hydroxyl groups in the aryl group may be one or more, but is preferably one. When the aryl group has a substituent other than a hydroxyl group, the number of the substituent may be one or more. When the aryl group has a plurality of substituents, the plurality of substituents may be the same or different.

[0031] In the general formula (b1), R １１represents a substituted or unsubstituted hydrocarbon group (X1). When the hydrocarbon group (X1) has a substituent, examples of the substituent include a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a hydroxyl group, an amino group, a nitro group, an amide group, a benzamide group, a carboxy group, a residue obtained by removing a hydrogen atom from one hydroxyl group of a dicarboxylic acid, and a halogen atom. The monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms is preferably a linear or branched alkyl group having 3 to 10 carbon atoms, more preferably a branched alkyl group having 3 to 10 carbon atoms. The halogen atom is, for example, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom, and preferably a chlorine atom. When the hydrocarbon group (X1) has a substituent, the number of the substituent may be one or more. Furthermore, when the hydrocarbon group (X1) has a plurality of substituents, the plurality of substituents may be the same or different.

[0032] In the general formula (b1), the hydrocarbon group (X1) represents an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, a cycloalkenyl group having 3 to 15 carbon atoms, a cycloalkylalkyl group having 4 to 15 carbon atoms, a cycloalkenylalkyl group having 4 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, or an arylalkyl group having 7 to 15 carbon atoms. The number of carbon atoms in the hydrocarbon group (X1) does not include the number of carbon atoms in the substituents that the hydrocarbon group (X1) may have. Note that if the number of carbon atoms in a group that can be selected as the hydrocarbon group (X1) exceeds 15, the luster of the metal material after heat treatment such as quenching may not be good even when combined with a carboxylic acid compound (C).

[0033] Examples of alkyl groups having 1 to 15 carbon atoms that can be selected as the hydrocarbon group (X1) include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, and pentadecyl groups. The alkyl group may be linear or branched.

[0034] Examples of alkenyl groups having 2 to 15 carbon atoms that can be selected as the hydrocarbon group (X1) include ethenyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, and pentadecenyl groups. The alkenyl group may be linear or branched.

[0035] Examples of cycloalkyl groups having 3 to 15 carbon atoms that can be selected as the hydrocarbon group (X1) include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group. The term "3 to 15 carbon atoms" in the "cycloalkyl group having 3 to 15 carbon atoms" means that the ring carbon atoms are 3 to 15. From the viewpoint of more easily exerting the effect of the combination with the carboxylic acid compound (C), the cycloalkyl group preferably has 5 to 10 carbon atoms, and more preferably 5 to 6 carbon atoms.

[0036] Examples of cycloalkenyl groups having 3 to 15 carbon atoms that can be selected as the hydrocarbon group (X1) include a cyclopropenyl group, a cyclobutenyl group, a cyclopentenyl group, a cyclohexenyl group, and a cycloheptenyl group. Note that the "3 to 15 carbon atoms" in the "cycloalkenyl group having 3 to 15 carbon atoms" means that the "cycloalkenyl group has 3 to 15 ring carbon atoms." From the viewpoint of more easily exerting the effect of the combination with the carboxylic acid compound (C), the cycloalkenyl group preferably has 5 to 10 carbon atoms, more preferably 5 to 6 carbon atoms.

[0037] Examples of cycloalkylalkyl groups having 4 to 15 carbon atoms that can be selected as the hydrocarbon group (X1) include a cyclopropylmethyl group, a cyclopropylethyl group, a cyclopropylpropyl group, a cyclopropylbutyl group, a cyclobutylmethyl group, a cyclopentylmethyl group, a cyclopentylethyl group, a cyclopentylpropyl group, a cyclohexylmethyl group, a cyclohexylethyl group, and a cyclohexylpropyl group. The cycloalkylalkyl group is a group represented by the following general formula (c1), in which one of the hydrogen atoms of an alkyl group is substituted with a cycloalkyl group: In the general formula (c1), the circle represents a cycloalkyl group, and R ３１ is an alkylene group. The wavy line indicates the bonding position with the carbon atom in the general formula (b1). The "4 to 15 carbon atoms" in the "cycloalkylalkyl group having 4 to 15 carbon atoms" refers to the number of ring carbon atoms of the cycloalkyl group and the number of alkylene groups (R ３１ ) means the total number of carbon atoms. From the viewpoint of more easily exerting the effect of the combination with the carboxylic acid compound (C), the number of carbon atoms (number of ring carbon atoms) of the cycloalkyl group constituting the cycloalkylalkyl group is preferably 5 to 10, more preferably 5 to 6. Furthermore, from the viewpoint of more easily exerting the effect of the combination with the carboxylic acid compound (C), the number of carbon atoms of the alkylene group constituting the cycloalkylalkyl group is preferably 1 to 6, more preferably 1 to 4, and even more preferably 1 to 2.

[0038] Examples of cycloalkenylalkyl groups having 4 to 15 carbon atoms that can be selected as the hydrocarbon group (X1) include a cyclopropenylmethyl group, a cyclopropenylethyl group, a cyclopropenylpropyl group, a cyclopropenylbutyl group, a cyclobutenylmethyl group, a cyclopentenylmethyl group, a cyclopentenylethyl group, a cyclopentenylpropyl group, a cyclohexenylmethyl group, a cyclohexenylethyl group, and a cyclohexenylpropyl group. The cycloalkenylalkyl group is a group represented by the following general formula (c2), in which one of the hydrogen atoms of an alkyl group is substituted with a cycloalkenyl group. In the general formula (c2), the circle represents a cycloalkenyl group, and R ３２ is an alkylene group. The wavy line indicates the bonding position with the carbon atom in the general formula (b1). The "4 to 15 carbon atoms" in the "cycloalkenylalkyl group having 4 to 15 carbon atoms" refers to the number of ring carbon atoms of the cycloalkenyl group and the number of alkylene groups (R ３２ ) means the total number of carbon atoms. From the viewpoint of more easily exerting the effect of the combination with the carboxylic acid compound (C), the number of carbon atoms (number of ring carbon atoms) of the cycloalkenyl group constituting the cycloalkenylalkyl group is preferably 5 to 10, more preferably 5 to 6. Furthermore, from the viewpoint of more easily exerting the effect of the combination with the carboxylic acid compound (C), the number of carbon atoms of the alkylene group constituting the cycloalkenylalkyl group is preferably 1 to 6, more preferably 1 to 4, and even more preferably 1 to 2.

[0039] Examples of aryl groups having 6 to 15 carbon atoms that can be selected as the hydrocarbon group (X1) include a phenyl group, a biphenyl group, a naphthyl group, a phenanthryl group, a fluorenyl group, and an anthryl group. The term "6 to 15 carbon atoms" in the "aryl group having 6 to 15 carbon atoms" means that the group has 6 to 15 ring carbon atoms. From the viewpoint of more easily achieving the effect of the combination with the carboxylic acid compound (C), the aryl group preferably has 6 to 10 carbon atoms, and more preferably 6 carbon atoms.

[0040] Examples of arylalkyl groups having 7 to 15 carbon atoms that can be selected as the hydrocarbon group (X1) include a phenylmethyl group, a phenylethyl group, a phenylpropyl group, a biphenylmethyl group, a biphenylethyl group, a biphenylpropyl group, a naphthylmethyl group, a naphthylethyl group, a naphthylpropyl group, a phenanthrylmethyl group, a fluorenylmethyl group, a fluorenylethyl group, and an anthrylmethyl group. The arylalkyl group is a group represented by the following general formula (c3), in which one of the hydrogen atoms of an alkyl group is substituted with an aryl group. In the general formula (c3), the double circle represents an aryl group, and R ３３is an alkylene group. The wavy line indicates the bonding position with the carbon atom in the general formula (b1). The "7 to 15 carbon atoms" in the "arylalkyl group having 7 to 15 carbon atoms" refers to the number of ring carbon atoms in the aryl group and the number of ring carbon atoms in the alkylene group (R ３３ ) means the total number of carbon atoms. From the viewpoint of more easily exerting the effect of the combination with the carboxylic acid compound (C), the number of carbon atoms (number of ring carbon atoms) of the aryl group constituting the arylalkyl group is preferably 6 to 10, more preferably 6. Furthermore, from the viewpoint of more easily exerting the effect of the combination with the carboxylic acid compound (C), the number of carbon atoms of the alkylene group constituting the arylalkyl group is preferably 1 to 6, more preferably 1 to 4, and even more preferably 1 to 2.

[0041] Here, the hydrocarbon group (X1) is preferably an aryl group having 6 to 15 carbon atoms and at least a hydroxyl group. Specifically, the sulfides (B1) preferably contain a compound represented by the following general formula (b1-1). The compound represented by the following general formula (b1-1) tends to have better luster when combined with the carboxylic acid compound (C). From this viewpoint, the content of the compound represented by the following general formula (b1-1) is preferably 70% by mass to 100% by mass, more preferably 80% by mass to 100% by mass, even more preferably 90% by mass to 100% by mass, and still more preferably 95% by mass to 100% by mass, based on the total amount of the sulfides (B1).

[0042]

[0043] In the general formula (b1-1), R １５ and R １６ each independently represents an alkyl group having 1 to 10 carbon atoms. From the viewpoint of making it easier to improve the oxidation stability of the heat-treated oil composition, the alkyl group is preferably a linear or branched alkyl group having 3 to 10 carbon atoms, and more preferably a branched alkyl group having 3 to 10 carbon atoms. The branched alkyl group preferably has 4 to 8 carbon atoms, more preferably 4 to 6 carbon atoms, and even more preferably 4 carbon atoms.

[0044] In the general formula (b1-1), m1 represents an integer of 0 to 4. m1 is preferably 1 to 3, and more preferably 2. When m1 is 2 or more, a plurality of R １５ may be the same or different.

[0045] In the general formula (b1-1), m2 represents an integer of 0 to 4. m2 is preferably 1 to 3, and more preferably 2. When m2 is 2 or more, a plurality of R １６ may be the same or different.

[0046] In general formula (b1-1), the hydroxyl group is preferably located at the 4-position of the phenyl group. In addition, m1 and m2 are each preferably 2, and the two R １５ and two R １６ are preferably located at the 3-position and the 5-position of the phenyl group, respectively. １５ and two R １６ are preferably branched alkyl groups having 3 to 10 carbon atoms. The branched alkyl groups preferably have 4 to 8 carbon atoms, more preferably 4 to 6 carbon atoms, and even more preferably 4 carbon atoms.

[0047] Specific examples of the sulfides (B1) include bis(3,5-di-tert-butyl-4-hydroxybenzyl) sulfide, 2-ethylthiomethylphenol, etc. Among these, bis(3,5-di-tert-butyl-4-hydroxybenzyl) sulfide is preferred.

[0048] The sulfides (B1) may be used alone or in combination of two or more.

[0049] <Sulfides (B2)> The sulfides (B2) are compounds represented by the following general formula (b2).

[0050] In the general formula (b2), Ar １２is an arylene group having 6 to 15 carbon atoms and at least a hydroxyl group. When the compound has a structure in which the sulfur atom and the arylene group are bonded via a methylene group, as in the compound represented by general formula (b2), it tends to be less effective in improving the luster of the metal material after heat treatment such as quenching. However, by using it in combination with a carboxylic acid compound (C), it is possible to improve the luster of the metal material after heat treatment such as quenching. Note that when the number of carbon atoms in the arylene group exceeds 15, it may not be possible to improve the luster of the metal material after heat treatment such as quenching, even when combined with a carboxylic acid compound (C).

[0051] In the general formula (b2), Ar １２ Examples of the arylene group having 6 to 15 carbon atoms constituting the formula (I) include a phenylene group, a biphenylene group, a naphthylene group, a phenanthrylene group, a fluorenylene group, and an anthrylene group. Note that the "6 to 15 carbon atoms" in the "arylene group having 6 to 15 carbon atoms" means "6 to 15 ring carbon atoms." From the viewpoint of more easily exerting the effect of the combination with the carboxylic acid compound (C), the number of carbon atoms in the arylene group is preferably 6 to 10, more preferably 6.

[0052] In the general formula (b2), Ar １２The arylene group having 6 to 15 carbon atoms constituting the group has at least one hydroxyl group. If the arylene group does not have a hydroxyl group, the oxidation stability of the heat treatment oil composition may be insufficient. Here, the arylene group may further have a substituent other than a hydroxyl group, or may not have a substituent other than a hydroxyl group. Examples of the substituent include a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a hydroxyl group, an amino group, a nitro group, a carboxy group, and a halogen atom. The monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms is preferably a linear or branched alkyl group having 1 to 10 carbon atoms. The halogen atom is, for example, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom, and preferably a chlorine atom. The number of hydroxyl groups possessed by the arylene group may be one or more, but is preferably one. When the arylene group has a substituent other than a hydroxyl group, the number of the substituents may be one or more. When the arylene group has a plurality of substituents, the plurality of substituents may be the same or different.

[0053] In the general formula (b2), R １２ and R １３ each independently represents a substituted or unsubstituted hydrocarbon group (X2). When the hydrocarbon group (X2) has a substituent, examples of the substituent include a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a hydroxyl group, an amino group, a nitro group, a carboxy group, and a halogen atom. The monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms is preferably a linear or branched alkyl group having 3 to 10 carbon atoms, more preferably a branched alkyl group having 3 to 10 carbon atoms. The halogen atom is, for example, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom, and is preferably a chlorine atom. When the hydrocarbon group (X2) has a substituent, the number of the substituent may be one or more. Furthermore, when the hydrocarbon group (X2) has a plurality of substituents, the plurality of substituents may be the same or different.

[0054] In the general formula (b2), the hydrocarbon group (X2) represents an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, a cycloalkenyl group having 3 to 15 carbon atoms, a cycloalkylalkyl group having 4 to 15 carbon atoms, a cycloalkenylalkyl group having 4 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, or an arylalkyl group having 7 to 15 carbon atoms. The number of carbon atoms in the hydrocarbon group (X2) does not include the number of carbon atoms in the substituents that the hydrocarbon group (X2) may have. Note that if the number of carbon atoms in a group that can be selected as the hydrocarbon group (X2) exceeds 15, the luster of the metal material after heat treatment such as quenching may not be improved even when combined with a carboxylic acid compound (C).

[0055] Examples of the alkyl group having 1 to 15 carbon atoms, the alkenyl group having 1 to 15 carbon atoms, the cycloalkyl group having 3 to 15 carbon atoms, the cycloalkenyl group having 3 to 15 carbon atoms, the cycloalkylalkyl group having 4 to 15 carbon atoms, the cycloalkenylalkyl group having 4 to 15 carbon atoms, the aryl group having 6 to 15 carbon atoms, and the arylalkyl group having 7 to 15 carbon atoms that can be selected as the hydrocarbon group (X2) include the alkyl group having 1 to 15 carbon atoms, the alkenyl group having 1 to 15 carbon atoms, the cycloalkyl group having 3 to 15 carbon atoms, the cycloalkenyl group having 3 to 15 carbon atoms, the cycloalkylalkyl group having 4 to 15 carbon atoms, the cycloalkenylalkyl group having 4 to 15 carbon atoms, the aryl group having 6 to 15 carbon atoms, and the arylalkyl group having 7 to 15 carbon atoms that are listed above as the hydrocarbon group (X1). The preferred ranges for each group are also the same as those for the hydrocarbon group (X1) above.

[0056] Here, the sulfides (B2) preferably contain a compound represented by the following general formula (b2-1). The compound represented by the following general formula (b2-1) tends to have better brilliance when combined with the carboxylic acid compound (C). From this viewpoint, the content of the compound represented by the following general formula (b2-1) is preferably 70% by mass to 100% by mass, more preferably 80% by mass to 100% by mass, even more preferably 90% by mass to 100% by mass, and still more preferably 95% by mass to 100% by mass, based on the total amount of the sulfides (B2).

[0057]

[0058] In the general formula (b2-1), R １７ each independently represents a linear or branched alkyl group having 1 to 10 carbon atoms. From the viewpoint of further improving the oxidation stability of the heat-treated oil composition, the alkyl group is preferably a linear or branched alkyl group having 1 to 6 carbon atoms, and more preferably a linear alkyl group having 1 to 3 carbon atoms.

[0059] In the general formula (b2-1), m3 represents an integer of 0 to 3. m3 is preferably 1 or 2, and more preferably 1. When m3 is 2 or more, a plurality of R １５ may be the same or different.

[0060] In the general formula (b2-1), R １２ and R １３ each independently represents a substituted or unsubstituted hydrocarbon group (X2). Examples of the hydrocarbon group (X2) include the same groups as those exemplified in the description of general formula (b2) above, but among these, an unsubstituted hydrocarbon group (X2) is preferred, and an unsubstituted alkyl group having 1 to 15 carbon atoms is more preferred. The number of carbon atoms in the alkyl group is preferably 6 to 15, more preferably 6 to 14. The alkyl group may be linear or branched, but is preferably linear.

[0061] In general formula (b2-1), the hydroxyl group is preferably located at the 1-position of the phenylene group. Furthermore, m3 is preferably 1, and R １７ is preferably located at the 2-position of the phenylene group. １７ is preferably a linear alkyl group having 1 to 3 carbon atoms.

[0062] Specific examples of the sulfides (B2) include 2-methyl-4,6-bis[(n-dodecylthio)methyl]phenol, 2-methyl-4,6-bis[(n-octylthio)methyl]phenol, and the like.

[0063] The sulfides (B2) may be used alone or in combination of two or more.

[0064] <Sulfides (B3)> The sulfides (B3) are compounds represented by the following general formula (b3).

[0065] In the general formula (b3), Ar １３ represents an aryl group having 6 to 15 carbon atoms and at least a hydroxyl group. １４ represents a substituted or unsubstituted aryl group having 6 to 15 carbon atoms. Compounds having a structure in which a sulfur atom and an aryl group are directly bonded and two sulfur atoms are bonded via one carbon atom, such as the compound represented by general formula (b3), tend to be less effective in improving the luster of metal materials after heat treatment such as quenching. However, by using them in combination with a carboxylic acid compound (C), the luster of metal materials after heat treatment such as quenching can be improved. Note that when the number of carbon atoms in the aryl group exceeds 15, the luster of metal materials after heat treatment such as quenching may not be improved even when combined with a carboxylic acid compound (C).

[0066] In the general formula (b3), Ar １３ As the Ar group, the Ar group described in the general formula (b1) can be used. １１ The preferred range is the same as Ar １１ is the same as:

[0067] In the general formula (b3), Ar １４ Examples of the aryl group having 6 to 15 carbon atoms constituting the formula (I) include a phenyl group, a biphenyl group, a naphthyl group, a phenanthryl group, a fluorenyl group, and an anthryl group. Note that the "6 to 15 carbon atoms" in the "aryl group having 6 to 15 carbon atoms" means that the ring carbon atoms are 6 to 15. From the viewpoint of more easily exerting the effects achieved by the combination with the carboxylic acid compound (C), the number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6.

[0068] When the aryl group has a substituent, examples of the substituent include a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a hydroxyl group, an amino group, a nitro group, an amide group, a benzamide group, a carboxy group, a residue obtained by removing a hydrogen atom from one hydroxyl group of a dicarboxylic acid, and a halogen atom. The monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms is preferably a linear or branched alkyl group having 3 to 10 carbon atoms, more preferably a branched alkyl group having 3 to 10 carbon atoms. The halogen atom is, for example, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom, and is preferably a chlorine atom. When the aryl group has a substituent, the number of the substituent may be one or more. Furthermore, when the aryl group has a plurality of substituents, the plurality of substituents may be the same or different.

[0069] Here, the sulfides (B3) preferably contain a compound represented by the following general formula (b3-1). The compound represented by the following general formula (b3-1) tends to have better brilliance when combined with the carboxylic acid compound (C). From this viewpoint, the content of the compound represented by the following general formula (b3-1) is preferably 70% by mass to 100% by mass, more preferably 80% by mass to 100% by mass, even more preferably 90% by mass to 100% by mass, and still more preferably 95% by mass to 100% by mass, based on the total amount of the sulfides (B3).

[0070] In the general formula (b3-1), R １８ and R １９ each independently represents an alkyl group having 1 to 10 carbon atoms. From the viewpoint of making it easier to improve the oxidation stability of the heat-treated oil composition, the alkyl group is preferably a linear or branched alkyl group having 3 to 10 carbon atoms, and more preferably a branched alkyl group having 3 to 10 carbon atoms. The branched alkyl group preferably has 4 to 8 carbon atoms, more preferably 4 to 6 carbon atoms, and even more preferably 4 carbon atoms.

[0071] In the general formula (b3-1), m4 represents an integer of 0 to 4. m4 is preferably 1 to 3, and more preferably 2. When m4 is 2 or more, a plurality of R １８ may be the same or different.

[0072] In the general formula (b3-1), m5 represents an integer of 0 to 4. m5 is preferably 1 to 3, and more preferably 2. When m5 is 2 or more, a plurality of R １９ may be the same or different.

[0073] In general formula (b3-1), the hydroxyl group is preferably located at the 4-position of the phenyl group. Furthermore, m4 and m5 are each preferably 2, and two R １８ and two R １９ are preferably located at the 3-position and the 5-position of the phenyl group, respectively. １８ and two R １９ are preferably branched alkyl groups having 3 to 10 carbon atoms. The branched alkyl groups preferably have 4 to 8 carbon atoms, more preferably 4 to 6 carbon atoms, and even more preferably 4 carbon atoms.

[0074] Specific examples of sulfides (B3) include 4,4'-[propane-2,2-diylbis(sulfanediyl)]bis[2,6-bis(1,1-dimethylethyl)phenol] (probucol), 4-[4-[2-(4-hydroxy-3,5-ditert-butyl-phenyl)sulfanylpropan-2-ylsulfanyl]-2,6-ditert-butyl-phenoxy]-4-oxobutanoic acid (succinobucol), etc. Among these, 4,4'-[propane-2,2-diylbis(sulfanediyl)]bis[2,6-bis(1,1-dimethylethyl)phenol] (probucol) is preferred.

[0075] The sulfides (B3) may be used alone or in combination of two or more.

[0076] <Sulfides (B4)> The sulfides (B4) are compounds represented by the following general formula (b4).

[0077] In the general formula (b4), Ar １５ and Ar １６ each independently represents a substituted or unsubstituted aryl group having 6 to 15 carbon atoms. Compounds having a structure in which a sulfur atom and an aryl group are directly bonded and two sulfur atoms are directly bonded, such as those represented by general formula (b4), tend to be less effective in improving the luster of metal materials after heat treatment such as quenching. However, by using them in combination with a carboxylic acid compound (C), the luster of metal materials after heat treatment such as quenching can be improved. Note that when the number of carbon atoms in the aryl group exceeds 15, the luster of metal materials after heat treatment such as quenching may not be improved even when combined with a carboxylic acid compound (C).

[0078] In the general formula (b4), Ar １５ and Ar １６ Examples of the aryl group having 6 to 15 carbon atoms constituting the formula (I) include a phenyl group, a biphenyl group, a naphthyl group, a phenanthryl group, a fluorenyl group, and an anthryl group. Note that the "6 to 15 carbon atoms" in the "aryl group having 6 to 15 carbon atoms" means that the ring carbon atoms are 6 to 15. From the viewpoint of more easily exerting the effects achieved by the combination with the carboxylic acid compound (C), the number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6.

[0079] When the aryl group has a substituent, examples of the substituent include a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a hydroxyl group, an amino group, a nitro group, an amide group, a benzamide group, a carboxy group, a residue obtained by removing a hydrogen atom from one hydroxyl group of a dicarboxylic acid, and a halogen atom. The monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms is preferably a linear or branched alkyl group having 3 to 10 carbon atoms, more preferably a branched alkyl group having 3 to 10 carbon atoms. The halogen atom is, for example, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom, and is preferably a chlorine atom. When the aryl group has a substituent, the number of the substituent may be one or more. Furthermore, when the aryl group has a plurality of substituents, the plurality of substituents may be the same or different.

[0080] In the general formula (b4), Ar １５ and Ar １６ are each independently preferably an unsubstituted aryl group having 6 to 15 carbon atoms or an aryl group having 6 to 15 carbon atoms and having at least one or more hydroxyl groups, more preferably an unsubstituted aryl group having 6 to 10 carbon atoms or an aryl group having 6 to 10 carbon atoms and having at least one or more hydroxyl groups, even more preferably an unsubstituted aryl group having 6 carbon atoms or an aryl group having 6 carbon atoms and having at least one or more hydroxyl groups, and still more preferably an unsubstituted aryl group having 6 carbon atoms.

[0081] Specific examples of the sulfides (B4) include diphenyl disulfide, di-p-tolyl disulfide, 4,4'-dithiodianiline, 2,2'-dithiodianiline, 2,2'-dithiodibenzoic acid, bis(2-benzamidophenyl) disulfide, bis(4-hydroxyphenyl) disulfide, etc. Among these, diphenyl disulfide is preferred.

[0082] The sulfides (B4) may be used alone or in combination of two or more.

[0083] (Preferred embodiment of sulfur compound (B)) In the heat-treated oil composition of this embodiment, from the viewpoint of making it easier to improve oxidation stability and to make it easier to exert the effect of combination with the carboxylic acid compound (C), the sulfur compound (B) preferably comprises one or more selected from the group consisting of sulfides (B1) represented by the general formula (b1), sulfides (B2) represented by the general formula (b2), and sulfides (B3) represented by the general formula (b3), and more preferably comprises one or more selected from the group consisting of sulfides (B1) represented by the general formula (b1) and sulfides (B2) represented by the general formula (b2). In this embodiment, the one or more selected from the group consisting of sulfides (B1) represented by the general formula (b1), sulfides (B2) represented by the general formula (b2), and sulfides (B3) represented by the general formula (b3) include the following embodiments. Only the sulfides (B1) represented by the general formula (b1) Only the sulfides (B2) represented by the general formula (b2) Only the sulfides (B3) represented by the general formula (b3) A combination of the sulfides (B1) represented by the general formula (b1) and the sulfides (B2) represented by the general formula (b2) A combination of the sulfides (B1) represented by the general formula (b1) and the sulfides (B3) represented by the general formula (b3) A combination of the sulfides (B2) represented by the general formula (b2) and the sulfides (B3) represented by the general formula (b3) A combination of the sulfides (B1) represented by the general formula (b1), the sulfides (B2) represented by the general formula (b2), and the sulfides (B3) represented by the general formula (b3) In the present embodiment, the one or more selected from the group consisting of the sulfides (B1) represented by the general formula (b1) and the sulfides (B2) represented by the general formula (b2) include the following embodiments.Only the sulfides (B1) represented by the general formula (b1) above Only the sulfides (B2) represented by the general formula (b2) above A combination of the sulfides (B1) represented by the general formula (b1) and the sulfides (B2) represented by the general formula (b2) above Furthermore, from the viewpoint of facilitating further improvement in oxidation stability and facilitating further exertion of the effect of the combination with the carboxylic acid compound (C), it is more preferable that the sulfur compound (B) includes one or more selected from the group consisting of sulfides (B1) containing a compound represented by the general formula (b1-1) above, sulfides (B2) containing a compound represented by the general formula (b2-1) above, and sulfides (B3) containing a compound represented by the general formula (b3-1) above. Among these, from the viewpoint of further improving oxidation stability, it is more preferable that the sulfur compound (B) contains one or more selected from the group consisting of sulfides (B1) containing a compound represented by the general formula (b1-1) above and sulfides (B2) containing a compound represented by the general formula (b2-1) above. In this embodiment, the one or more selected from the group consisting of sulfides (B1) containing a compound represented by the general formula (b1-1) above, sulfides (B2) containing a compound represented by the general formula (b2-1) above, and sulfides (B3) containing a compound represented by the general formula (b3-1) above includes the following aspects.Only sulfides (B1) containing a compound represented by the general formula (b1-1) Only sulfides (B2) containing a compound represented by the general formula (b2-1) Only sulfides (B3) containing a compound represented by the general formula (b3-1) A combination of sulfides (B1) containing a compound represented by the general formula (b1-1) and sulfides (B2) containing a compound represented by the general formula (b2-1) A combination of sulfides (B1) containing a compound represented by the general formula (b1-1) and sulfides (B3) containing a compound represented by the general formula (b3-1) A combination of sulfides (B2) containing a compound represented by the general formula (b2-1) and sulfides (B3) containing a compound represented by the general formula (b3-1) A combination of sulfides (B2) containing a compound represented by the general formula (b2-1) and sulfides (B3) containing a compound represented by the general formula (b3-1) A combination of sulfides (B2) containing a compound represented by the general formula (b2-1) and sulfides (B3) containing a compound represented by the general formula (b3-1) A combination of a sulfide (B1) containing a compound represented by the general formula (b1-1), a sulfide (B2) containing a compound represented by the general formula (b2-1), and a sulfide (B3) containing a compound represented by the general formula (b3-1) Furthermore, in the present embodiment, the one or more selected from the group consisting of a sulfide (B1) containing a compound represented by the general formula (b1-1) and a sulfide (B2) containing a compound represented by the general formula (b2-1) includes the following aspects: Only a sulfide (B1) containing a compound represented by the general formula (b1-1) Only a sulfide (B2) containing a compound represented by the general formula (b2-1) A combination of a sulfide (B1) containing a compound represented by the general formula (b1-1) and a sulfide (B2) containing a compound represented by the general formula (b2-1).

[0084] (Content of sulfur compound (B)) In the heat-treated oil composition of this embodiment, the content of sulfur compound (B) is preferably 0.01 mass% or more, more preferably 0.02 mass%, and even more preferably 0.05 mass% or more, based on the total amount of the heat-treated oil composition, from the viewpoint of more easily achieving the effects of the present invention. Furthermore, from the viewpoint of more easily suppressing the generation of sludge and the shortening of the life of the heat-treated oil composition due to excessive addition of sulfur compound, it is preferably 2.0 mass% or less, more preferably 1.0 mass% or less, and even more preferably 0.5 mass% or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 0.01 mass% to 2.0 mass%, more preferably 0.02 mass% to 1.0 mass%, and even more preferably 0.05 mass% to 0.5 mass%.

[0085] (Molecular Weight of Sulfur Compound (B)) In the heat-treated oil composition of this embodiment, from the viewpoint of making it easier to exhibit the effects of the present invention, the molecular weight of the sulfur compound (B) is preferably 100 or more, more preferably 150 or more, and even more preferably 180 or more. Also, it is preferably 1,500 or less, more preferably 1,200 or less, and even more preferably 1,000 or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 100 to 1,500, more preferably 150 to 1,200, and even more preferably 180 to 1,000.

[0086] <Carboxylic Acid Compound (C)> The heat treatment oil composition of this embodiment contains a carboxylic acid compound (C). As mentioned above, the sulfur compound (B) is poor at improving the luster of metal materials after heat treatment such as quenching. However, by using it in combination with the carboxylic acid compound (C), the sulfur compound (B) and the carboxylic acid compound (C) interact with each other, improving the luster of metal materials after heat treatment such as quenching.

[0087] The carboxylic acid compound (C) is one or more selected from the group consisting of compounds having at least one carboxy group and their anhydrides. The compound having at least one carboxy group may be a monocarboxylic acid or a dicarboxylic or higher polycarboxylic acid. It may also be a partial ester in which a portion of the polycarboxylic acid is esterified. Among these, from the viewpoint of more easily exerting the effect of the combination with the sulfur compound (B), the compound having at least one carboxy group is preferably a dicarboxylic or higher polycarboxylic acid, and more preferably a dicarboxylic acid. That is, the carboxylic acid compound (C) is preferably one or more selected from the group consisting of dicarboxylic acids and their anhydrides. Among these, dicarboxylic acids are preferred. The carboxylic acid compound (C) may be used alone or in combination of two or more.

[0088] Preferred examples of the carboxylic acid compound (C) include one or more selected from dicarboxylic acids such as alkylsuccinic acid and alkenylsuccinic acid, and anhydrides thereof. Among these, from the viewpoint of further enhancing the effects of the combination with the sulfur compound (B), one or more selected from dicarboxylic acids such as alkylsuccinic acid and alkenylsuccinic acid are preferred, and alkenylsuccinic acid is more preferred. Furthermore, the number of carbon atoms in the alkyl group of the alkylsuccinic acid and the alkenyl group of the alkenylsuccinic acid is preferably 10 to 20.

[0089] The divalent carboxylic acid (preferably alkenyl succinic acid) such as alkyl succinic acid and alkenyl succinic acid preferably used as the carboxylic acid compound (C) has a kinematic viscosity at 40°C of preferably 10 mm ２ / s or more, more preferably 15 mm ２ / s or more, more preferably 20 mm ２ / s or more. Also, preferably 50 mm ２ / s or less, more preferably 40 mm ２ / s or less, more preferably 30 mm ２The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 10 mm ２ / s ~ 50 mm ２ / s, more preferably 15 mm ２ / s ~ 40 mm ２ / s, more preferably 20 mm ２ / s ~ 30 mm ２ / s. In this specification, the 40 ° C. kinematic viscosity of a dicarboxylic acid such as alkylsuccinic acid and alkenylsuccinic acid (preferably alkenylsuccinic acid) means a value measured in accordance with JIS K2283:2000. Furthermore, the dicarboxylic acid such as alkylsuccinic acid and alkenylsuccinic acid (preferably alkenylsuccinic acid) preferably used as the carboxylic acid compound (C) preferably has an acid value of 50 mg KOH / g or more, more preferably 100 mg KOH / g or more, and even more preferably 150 mg KOH / g or more. Furthermore, it is preferably 400 mg KOH / g or less, more preferably 300 mg KOH / g or less, and even more preferably 250 mg KOH / g or less. The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, the acid value is preferably 50 mgKOH / g to 400 mgKOH / g, more preferably 100 mgKOH / g to 300 mgKOH / g, and even more preferably 150 mgKOH / g to 250 mgKOH / g. In this specification, the acid value of a dicarboxylic acid such as an alkylsuccinic acid or an alkenylsuccinic acid (preferably an alkenylsuccinic acid) refers to a value measured by indicator titration in accordance with JIS K 2501:2003-5.

[0090] (Content of carboxylic acid compound (C)) In the heat-treated oil composition of this embodiment, the content of the carboxylic acid compound (C) is, from the viewpoint of making it easier to exhibit the effects of the present invention, preferably 0.1 mass% or more, more preferably 0.15 mass% or more, and even more preferably 0.2 mass% or more, based on the total amount of the heat-treated oil composition. Also, it is preferably 5.0 mass% or less, more preferably 3.0 mass% or less, and even more preferably 2.0 mass% or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 0.1 mass% to 5.0 mass%, more preferably 0.15 mass% to 3.0 mass%, and even more preferably 0.2 mass% to 2.0 mass%.

[0091] <Ratio of sulfur compound (B) to carboxylic acid compound (C) [(B) / (C)]> In the heat-treated oil composition of this embodiment, the ratio of sulfur compound (B) to carboxylic acid compound (C) [(B) / (C)] is, in mass ratio, preferably 0.002 or more, more preferably 0.02 or more, and even more preferably 0.1 or more, from the viewpoint of more easily achieving the effects of the present invention. It is also preferably 0.8 or less, more preferably 0.5 or less, and even more preferably 0.3 or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 0.002 to 0.8, more preferably 0.02 to 0.5, and even more preferably 0.1 to 0.3.

[0092] <Additives> The heat-treated oil composition of this embodiment is prepared by mixing the base oil (A), the sulfur compound (B), and the carboxylic acid compound (C), and if desired, additives commonly used in heat-treated oil compositions may also be blended. Examples of such additives include steam film breakers, brightness improvers, coolability improvers, and antioxidants. One type of additive may be used alone, or two or more types may be used in combination.

[0093] (Vapor Film Breaker) Examples of the vapor film breaker include ethylene-α-olefin copolymers (α-olefins having 3 to 20 carbon atoms) such as ethylene-propylene copolymers; hydrogenated products of the ethylene-α-olefin copolymers; α-olefin polymers having 5 to 20 carbon atoms such as 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene; hydrogenated products of the α-olefin polymers; olefin polymers having 3 or 4 carbon atoms such as polypropylene, polybutene, and polyisobutylene; hydrogenated products of the olefin polymers; polymeric compounds such as polymethacrylate, polymethacrylate, polystyrene, and petroleum resin; and asphalt. These vapor film breakers may be used alone or in combination of two or more. The number average molecular weight (Mn) of the vapor film breaker is usually preferably 800 to 100,000. The number average molecular weight (Mn) of the vapor film breaker is a polystyrene-equivalent value measured using gel permeation chromatography (GPC). The content of the vapor film breaker is preferably 0.5 to 18 mass%, more preferably 1.0 to 16 mass%, and even more preferably 2.0 to 15 mass%, based on the total amount of the heat treatment oil composition.

[0094] (Brilliance improver) Examples of the brilliance improver include fats and oils; complete esters of alkyl succinic acid and alkyl succinimides and derivatives thereof; complete esters of alkenyl succinic acid, alkenyl succinimides and derivatives thereof; substituted hydroxyaromatic carboxylic acid esters (complete esters) and derivatives thereof. These brilliance improvers may be used alone or in combination of two or more. The content of the brilliance improver is preferably 0.1% by mass to 5.0% by mass, more preferably 0.3% by mass to 3.0% by mass, and even more preferably 0.4% by mass to 2.0% by mass, based on the total amount of the heat treatment oil composition.

[0095] (Cooling Improver) Examples of cooling improvers include metal-based detergents such as metal sulfonates, metal salicylates, and metal phenates. Metals constituting metal detergents include, for example, alkali metals such as sodium and potassium, and alkaline earth metals such as magnesium, calcium, and barium. Other examples of cooling improvers include imide-based dispersants such as boron-containing alkenyl succinimides, and mono- or di-carboxylic acid amides such as fatty acids or succinic acid. These cooling improvers may be used alone or in combination of two or more. Here, in order to more easily achieve the effects of the present invention, it is preferable that the content of the cooling improver is low. Specifically, the content of the cooling improver is preferably less than 0.20 mass%, more preferably less than 0.10 mass%, even more preferably less than 0.01 mass%, even more preferably less than 0.001 mass%, based on the total amount of the heat treatment oil composition. It is even more preferable that the cooling improver is not present.

[0096] (Antioxidant) Examples of the antioxidant include phenol-based antioxidants and amine-based antioxidants. Examples of the phenol-based antioxidant include 2,6-di-tert-butyl-paracresol, 2,6-di-tert-butyl-4-ethylphenol, 2,4,6-tri-tert-butylphenol, 2,6-di-tert-butyl-4-hydroxymethylphenol, 2,6-di-tert-butylphenol, 2,4-dimethyl-6-tert-butylphenol, 2,6-di-tert-butyl-4-(N,N-dimethylaminomethyl)phenol, 2,6-di-tert-amyl-4-methylphenol, and n-octadecyl-3-(4-hydroxy-3,5-di-tert-butylphenyl). monocyclic phenols such as propionate; and polycyclic phenols such as 4,4'-methylenebis(2,6-di-tert-butylphenol), 4,4'-isopropylidenebis(2,6-di-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-bis(2,6-di-tert-butylphenol), 4,4'-bis(2-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), and 4,4'-butylidenebis(3-methyl-6-tert-butylphenol). Examples of the amine-based antioxidant include diphenylamine-based antioxidants and naphthylamine-based antioxidants. Examples of diphenylamine antioxidants include alkylated diphenylamines having an alkyl group having 3 to 20 carbon atoms, and specific examples include diphenylamine, monooctyldiphenylamine, monononyldiphenylamine, 4,4'-dibutyldiphenylamine, 4,4'-dihexyldiphenylamine, 4,4'-dioctyldiphenylamine, 4,4'-dinonyldiphenylamine, tetrabutyldiphenylamine, tetrahexyldiphenylamine, tetraoctyldiphenylamine, and tetranonyldiphenylamine.Examples of naphthylamine-based antioxidants include alkyl-substituted phenyl-α-naphthylamines having 3 to 20 carbon atoms, such as α-naphthylamine, phenyl-α-naphthylamine, butylphenyl-α-naphthylamine, hexylphenyl-α-naphthylamine, octylphenyl-α-naphthylamine, and nonylphenyl-α-naphthylamine. These antioxidants may be used alone or in combination of two or more. The content of the antioxidant is preferably 0.01% by mass to 5.0% by mass, more preferably 0.02% by mass to 3.0% by mass, and even more preferably 0.05% by mass to 2.0% by mass, based on the total amount of the heat treatment oil composition.

[0097] [Physical properties of the heat-treated oil composition of the present invention] <Sulfur content> The heat-treated oil composition of this embodiment has a sulfur content of preferably 10 ppm by mass or more, more preferably 20 ppm by mass or more, and even more preferably 25 ppm by mass or more, based on the total amount of the heat-treated oil composition. It is also preferably 10,000 ppm by mass or less, more preferably 7,000 ppm by mass or less, even more preferably 5,000 ppm by mass or less, and even more preferably 3,000 ppm by mass or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 10 ppm by mass to 10,000 ppm by mass, more preferably 20 ppm by mass to 7,000 ppm by mass, even more preferably 25 ppm by mass to 5,000 ppm by mass, and even more preferably 25 ppm by mass to 3,000 ppm by mass. In this specification, the sulfur content in the heat-treated oil composition means a value measured in accordance with the ultraviolet fluorescence method of JIS K 2541-6:2013 when measured on the order of ppm by mass, and means a value measured in accordance with the wavelength dispersive X-ray fluorescence method of JIS K 2541-7:2013 when measured on the order of % by mass.

[0098] <Phosphorus Amount, Molybdenum Amount, and Zinc Amount> The heat-treated oil composition of this embodiment preferably has a phosphorus amount, a molybdenum amount, and a zinc amount, each independently, based on the total amount of the heat-treated oil composition, of less than 0.01 mass%, more preferably less than 0.001 mass%, and even more preferably contains no phosphorus, molybdenum, or zinc. In this specification, the phosphorus amount, molybdenum amount, and zinc amount in the heat-treated oil composition can be measured in accordance with JPI-5S-38-03.

[0099] <40°C kinematic viscosity> The heat treatment oil composition of this embodiment has a kinematic viscosity at 40°C set according to the desired oil temperature during heat treatment such as quenching. Heat treatment oil compositions are classified into cold oils used at low oil temperatures, hot oils used at high oil temperatures, and semi-hot oils used at intermediate oil temperatures. Cold oils are classified as Type 1 of JIS K2242:2012, and semi-hot oils and hot oils are classified as Type 2 of JIS K2242:2012. When the heat treatment oil composition of this embodiment is used as cold oil, the 40°C kinematic viscosity is 5mm ２ / s or more 40mm ２ When the heat-treated oil composition of the present embodiment is used as a semi-hot oil or a hot oil, the kinematic viscosity at 40°C is preferably less than 40 mm / s. ２ / s or more 500mm ２ In this specification, the 40°C kinematic viscosity of the heat-treated oil composition means the value measured in accordance with JIS K2283:2000.

[0100] [Method for producing heat treatment oil composition] The method for producing the heat treatment oil composition of this embodiment is not particularly limited. For example, the method for producing the heat treatment oil composition of this embodiment includes a step of mixing one or more base oils (A) selected from the group consisting of mineral oils (A1), synthetic oils (A2), and vegetable oils (A3), a sulfur compound (B), and a carboxylic acid compound (C). The sulfur compound (B) includes one or more selected from the group consisting of sulfides (B1) represented by the following general formula (b1), sulfides (B2) represented by the following general formula (b2), sulfides (B3) represented by the following general formula (b3), and sulfides (B4) represented by the following general formula (b4). The carboxylic acid compound (C) is one or more selected from the group consisting of compounds having at least one carboxy group and their anhydrides. [In the general formula (b1), Ar １１ R each independently represents an aryl group having 6 to 15 carbon atoms and at least a hydroxyl group. １１ represents a substituted or unsubstituted hydrocarbon group (X1). The hydrocarbon group (X1) represents an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, a cycloalkenyl group having 3 to 15 carbon atoms, a cycloalkylalkyl group having 4 to 15 carbon atoms, a cycloalkenylalkyl group having 4 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, or an arylalkyl group having 7 to 15 carbon atoms. In the general formula (b2), Ar １２ represents an arylene group having 6 to 15 carbon atoms and at least a hydroxyl group. １２ and R １３ each independently represents a substituted or unsubstituted hydrocarbon group (X2). The hydrocarbon group (X2) represents an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, a cycloalkenyl group having 3 to 15 carbon atoms, a cycloalkylalkyl group having 4 to 15 carbon atoms, a cycloalkenylalkyl group having 4 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, or an arylalkyl group having 7 to 15 carbon atoms. In the general formula (b3), Ar １３ represents an aryl group having 6 to 15 carbon atoms and at least a hydroxyl group. １４represents a substituted or unsubstituted aryl group having 6 to 15 carbon atoms. １５ and Ar １６ each independently represents a substituted or unsubstituted aryl group having 6 to 15 carbon atoms.

[0101] The method for mixing the above components is not particularly limited, and examples thereof include a method comprising a step of blending a sulfur compound (B) and a carboxylic acid compound (C) with a base oil (A). The sulfur compound (B) and the carboxylic acid compound (C) may be blended simultaneously with the base oil (A) or separately. When the heat-treated oil composition further contains other components (the additives) other than the base oil (A), the sulfur compound (B), and the carboxylic acid compound (C), the other components may be blended simultaneously with the sulfur compound (B) and the carboxylic acid compound (C) with the base oil (A) or separately. Each component may be blended after being formed into a solution (dispersion) by adding a diluent oil or the like. After blending the components, it is preferable to uniformly disperse them by stirring using a known method. The preferred embodiments of the base oil (A), the sulfur compound (B), and the carboxylic acid compound (C) are as described above.

[0102] [Uses of Heat Treatment Oil Composition] The heat treatment oil composition of this embodiment can be used during heat treatment, such as quenching, of a metal material to improve the luster of the metal material after heat treatment, such as quenching. For example, it can be suitably used as a heat treatment oil composition when performing heat treatment, such as quenching, on various alloy steels, such as carbon steel, nickel-manganese steel, chromium-molybdenum steel, and manganese steel. The heat treatment oil composition of this embodiment also has excellent oxidation stability. Therefore, the heat treatment oil composition of this embodiment is preferably used as a heat treatment oil (preferably, a quenching oil or a tempering oil) for quenching or the like of a metal material. This embodiment also provides a method of using the heat treatment oil composition of this embodiment as a heat treatment oil (preferably, a quenching oil or a tempering oil) for quenching or the like of a metal material. When the heat treatment is quenching, the oil temperature of the heat treatment oil composition is preferably set to 40°C to 280°C, more preferably 50°C to 200°C, and even more preferably 60°C to 150°C. When the heat treatment is tempering, the oil temperature may be further increased, for example, up to an upper limit of 300°C. The quenching temperature of the metal material may be 800°C or higher and 900°C or lower, or may be higher than 900°C and 1100°C or lower.

[0103] [One Aspect of the Present Invention Provided] According to one aspect of the present invention, the following items [1] to

[11] are provided: [1] A heat treatment oil composition comprising one or more base oils (A) selected from the group consisting of mineral oils (A1), synthetic oils (A2), and vegetable oils (A3), a sulfur compound (B), and a carboxylic acid compound (C), wherein the sulfur compound (B) comprises one or more compounds selected from the group consisting of sulfides (B1) represented by the following general formula (b1), sulfides (B2) represented by the following general formula (b2), sulfides (B3) represented by the following general formula (b3), and sulfides (B4) represented by the following general formula (b4), and the carboxylic acid compound (C) is one or more compounds selected from the group consisting of compounds having at least one carboxy group and anhydrides thereof. [In the general formula (b1), Ar １１ represents an aryl group having 6 to 15 carbon atoms and at least a hydroxyl group. １１represents a substituted or unsubstituted hydrocarbon group (X1). The hydrocarbon group (X1) represents an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, a cycloalkenyl group having 3 to 15 carbon atoms, a cycloalkylalkyl group having 4 to 15 carbon atoms, a cycloalkenylalkyl group having 4 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, or an arylalkyl group having 7 to 15 carbon atoms. In the general formula (b2), Ar １２ is an arylene group having 6 to 15 carbon atoms and at least a hydroxyl group. １２ and R １３ each independently represents a substituted or unsubstituted hydrocarbon group (X2). The hydrocarbon group (X2) represents an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, a cycloalkenyl group having 3 to 15 carbon atoms, a cycloalkylalkyl group having 4 to 15 carbon atoms, a cycloalkenylalkyl group having 4 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, or an arylalkyl group having 7 to 15 carbon atoms. In the general formula (b3), Ar １３ represents an aryl group having 6 to 15 carbon atoms and at least a hydroxyl group. １４ represents a substituted or unsubstituted aryl group having 6 to 15 carbon atoms. １５ and Ar １６each independently represent a substituted or unsubstituted aryl group having 6 to 15 carbon atoms.] [2] The heat-treatment oil composition according to [1] above, wherein in the general formula (b1), the hydrocarbon group (X1) is an aryl group having 6 to 15 carbon atoms and at least a hydroxyl group. [3] The heat-treatment oil composition according to [1] or [2] above, wherein the sulfur compound (B) comprises one or more selected from the group consisting of sulfides (B1) represented by the general formula (b1), sulfides (B2) represented by the general formula (b2), and sulfides (B3) represented by the general formula (b3). [4] The heat-treatment oil composition according to any of [1] to [3] above, wherein the sulfur content is 10 ppm by mass to 10,000 ppm by mass based on the total amount of the heat-treatment oil composition. [5] The heat treatment oil composition according to any one of [1] to [4] above, wherein the content of the sulfur compound (B) is 0.01 mass% to 2.0 mass% based on the total amount of the heat treatment oil composition. [6] The heat treatment oil composition according to any one of [1] to [5] above, wherein the content of the carboxylic acid compound (C) is 0.1 mass% to 5.0 mass% based on the total amount of the heat treatment oil composition. [7] The heat treatment oil composition according to any one of [1] to [6] above, wherein the content ratio of the sulfur compound (B) to the carboxylic acid compound (C) [(B) / (C)] is 0.002 to 0.8 by mass. [8] The heat treatment oil composition according to any one of [1] to [7] above, further comprising one or more selected from the group consisting of a vapor film breaker, an antioxidant, a luster improver, and a coolability improver. [9] The heat treatment oil composition according to any one of [1] to [8] above, which is used as a quenching oil or a tempering oil.

[10] A method of using the heat treatment oil composition according to any one of [1] to [9] above as a quenching oil or a tempering oil.

[11] A method for producing a heat treatment oil composition, comprising a step of mixing one or more base oils (A) selected from the group consisting of mineral oils (A1), synthetic oils (A2), and vegetable oils (A3), a sulfur compound (B), and a carboxylic acid compound (C), wherein the sulfur compound (B) comprises one or more selected from the group consisting of sulfides (B1) represented by the following general formula (b1), sulfides (B2) represented by the following general formula (b2), sulfides (B3) represented by the following general formula (b3), and sulfides (B4) represented by the following general formula (b4), and the carboxylic acid compound (C) is one or more selected from the group consisting of compounds having at least one carboxy group and anhydrides thereof. [In the general formula (b1), Ar １１ R each independently represents an aryl group having 6 to 15 carbon atoms and at least a hydroxyl group. １１ represents a substituted or unsubstituted hydrocarbon group (X1). The hydrocarbon group (X1) represents an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, a cycloalkenyl group having 3 to 15 carbon atoms, a cycloalkylalkyl group having 4 to 15 carbon atoms, a cycloalkenylalkyl group having 4 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, or an arylalkyl group having 7 to 15 carbon atoms. In the general formula (b2), Ar １２ represents an arylene group having 6 to 15 carbon atoms and at least a hydroxyl group. １２ and R １３ each independently represents a substituted or unsubstituted hydrocarbon group (X2). The hydrocarbon group (X2) represents an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, a cycloalkenyl group having 3 to 15 carbon atoms, a cycloalkylalkyl group having 4 to 15 carbon atoms, a cycloalkenylalkyl group having 4 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, or an arylalkyl group having 7 to 15 carbon atoms. In the general formula (b3), Ar １３ represents an aryl group having 6 to 15 carbon atoms and at least a hydroxyl group. １４ represents a substituted or unsubstituted aryl group having 6 to 15 carbon atoms. １５ and Ar １６each independently represents a substituted or unsubstituted aryl group having 6 to 15 carbon atoms.

[0104] The present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples.

[0105] [Methods for measuring various physical properties] (1) 40°C kinematic viscosity of base oil (A), carboxylic acid compound (C), and heat-treated oil composition The 40°C kinematic viscosity of the base oil (A) and carboxylic acid compound (C) used in each example and each comparative example, and the heat-treated oil composition prepared in each example and each comparative example, was measured in accordance with JIS K2283: 2000. (2) Sulfur content The sulfur content of the base oil (A) used in each example and each comparative example, and the heat-treated oil composition prepared in each example and each comparative example, was measured in accordance with the ultraviolet fluorescence method of JIS K 2541-6: 2013.

[0106] [Examples 1 to 8, Comparative Examples 1 to 9] The raw materials used in preparing the heat-treated oil compositions of Examples 1 to 8 and Comparative Examples 1 to 9 are shown below.

[0107] (1) Base oil (A) "Mineral oil (A1)-1": High viscosity mineral oil classified in Group II in the API category (corresponding to bright stock with low sulfur content), sulfur content: less than 3 ppm by mass, kinematic viscosity at 40 ° C: 396.7 mm ２ / s "Mineral oil (A1)-2": Mineral oil classified as Group II in the API category, sulfur content: less than 3 ppm by mass, kinematic viscosity at 40 ° C: 7.573 mm ２ / s "Mineral oil (A1)-3": Mineral oil classified as Group III in the API category, sulfur content: less than 3 ppm by mass, kinematic viscosity at 40 ° C: 20.57 mm ２ / s "Mineral oil (A1)-4": Mineral oil classified as Group II in the API category, sulfur content: less than 3 ppm by mass, kinematic viscosity at 40 ° C: 31.49 mm ２ / s

[0108] (2) Sulfur Compound (B) "Sulfide (B1)-1": bis(3,5-di-tert-butyl-4-hydroxybenzyl) sulfide (molecular weight: 470.75) This is a compound represented by the following chemical formula (b1-1-1). The compound represented by the chemical formula (b1-1-1) is a compound represented by the general formula (b1-1), wherein m1 and m2 are 2, and two R １５ and two R １６ All of these are tert-butyl groups. The hydroxyl group is located at the 4-position of the phenyl group. The tert-butyl groups are located at the 3- and 5-positions of the phenyl group.

[0109] "Sulfide (B2)-1": 2-methyl-4,6-bis[(dodecylthio)methyl]phenol (molecular weight: 536.96) This is a compound represented by the following chemical formula (b2-1-1). The compound represented by the chemical formula (b2-1-1) is a compound represented by the general formula (b2-1) in which m3 is 1 and R １７ is a methyl group. The hydroxyl group is located at the 1st position of the phenyl group. The methyl group is located at the 2nd position of the phenyl group.

[0110] "Sulfide (B3)-1": Probucol (4,4'-[propane-2,2-diylbis(sulfanediyl)]bis[2,6-bis(1,1-dimethylethyl)phenol], molecular weight: 516.84) This is a compound represented by the following chemical formula (b3-1-1). The compound represented by the chemical formula (b3-1-1) is a compound represented by the general formula (b3-1), wherein m4 and m5 are 2, and two R １８ and two R １９ are both tert-butyl groups. The hydroxyl group is located at the 4-position of the phenyl group, and the tert-butyl groups are located at the 3- and 5-positions of the phenyl group.

[0111] "Sulfides (B4)-1": diphenyl disulfide (molecular weight: 218.33) This is a compound represented by the following chemical formula (b4-1-1). The compound represented by the chemical formula (b4-1-1) is a compound represented by the general formula (b4), １５ and Ar １６ are each an unsubstituted phenyl group.

[0112] (3) Comparative Example Sulfur Compound (B') "Dibenzothiophene": a thiophene represented by the following chemical formula (b').

[0113] (4) Carboxylic Acid Compound (C) "Alkenyl succinic acid": a dicarboxylic acid. The alkenyl group has 10 to 20 carbon atoms. Kinematic viscosity at 40°C: 26.0 mm ２ / s Acid value: 195 mg KOH / g The acid value is a value measured by indicator titration in accordance with JIS K 2501:2003-5.

[0114] (5) Non-carboxylic acid compound (C') "Calcium sulfonate": base number 300 mg KOH / g. The base number of calcium sulfonate is a value measured by potentiometric titration (base number / perchloric acid method) in accordance with JIS K2501:2003-9.

[0115] (6) Additives Vapor film breaker: polymer

[0116] The above raw materials were thoroughly mixed in the blending amounts (mass %) shown in Tables 1 and 2 to prepare the heat-treated oil compositions of Examples 1 to 8 and Comparative Examples 1 to 9, respectively.

[0117] [Evaluation Method] (1) Evaluation Method of Brightness The brightness of the steel material after quenching was evaluated with reference to "The Influence of Oxygen in a Heat Treatment Oil Tank on Brightness (Idemitsu Tribo Review, No. 31, pp. 1963-1966, published September 30, 2008)." Specifically, a dumbbell-shaped steel material S45C (diameter: 16 mm, length: 30 mm, hardness H ＲＣ : 16) and cylindrical steel material SUJ2 (diameter: 10 mm, length: 30 mm, hardness H ＲＣ : 15) were combined to prepare test specimens. Specifically, a dumbbell-shaped steel material S45C and a cylindrical steel material SUJ2 were tied together at their centers using a SUS303 wire, thereby bundling the dumbbell-shaped steel material S45C and the cylindrical steel material SUJ2 (see Figure 1). Note that the "Steel material S45C" is a carbon steel specified in JIS G 4051. The "Steel material SUJ2" is a high-carbon chromium bearing steel specified in JIS G 4805. The "SUS303 wire" is a stainless steel wire specified in JIS G 4309. The test specimens were then heated in a furnace filled with a mixed gas atmosphere of nitrogen and hydrogen, and then quenched by being placed in a heat treatment oil composition, thereby conducting a quenching test. The quenching test was performed under the following two conditions.

[0118] (Quenching test condition 1: hot oil simulated test, Table 1) Test subjects: Examples 1 to 4, Comparative Examples 1 to 7 Furnace temperature: 850°C Test piece retention time in furnace: 40 minutes after furnace temperature reaches 850°C Temperature of heat treatment oil composition: 120°C Duration of test piece immersion in heat treatment oil composition (quenching time): 10 minutes

[0119] (Quenching test condition 2: Cold oil simulated test, Table 2) Test subjects: Examples 5 to 8, Comparative Examples 8 to 9 Furnace temperature: 850°C Test piece retention time in furnace: 40 minutes after furnace temperature reaches 850°C Temperature of heat treatment oil composition: 80°C Test piece immersion time in heat treatment oil composition (quenching time): 10 minutes

[0120] The brilliance of the test specimens after quenching was evaluated based on the following criteria, focusing on "brightness," "edge coloring," and "contact area coloring." Furthermore, based on the evaluation results of "brightness," "edge coloring," and "contact area coloring," the brilliance of the test specimens was evaluated comprehensively based on the following criteria. (Brightness) Appearance samples with the specified coloring were prepared and visually compared with the color of the test specimens after quenching. The degree of coloring of the appearance samples is indicated by the following numerical values: 0: No coloring at all. 1: Light coloring. 2: Dark brown to black coloring. (Edge Coloring) The edges of the test specimens (see Figure 1) were visually observed and evaluated based on the following criteria: 0: No or almost no coloring. 1: Light coloring was observed. 2: Dark brown to black coloring was observed. (Contact Area Coloring) The contact areas of the test specimens (contact areas between the dumbbell-shaped steel material and the cylindrical steel material, see Figure 1) were visually observed and evaluated based on the following criteria. 0: No or almost no coloring. 1: Light coloring is observed. 2: Dark brown to black coloring is observed.

[0121] (Overall evaluation of brilliance) Using the evaluation results of "brightness," "edge coloring," and "contact area coloring," an overall evaluation was performed based on the following criteria. Evaluation S: The sum of the evaluation results of "brightness," "edge coloring," and "contact area coloring" is 0. Evaluation A: The sum of the evaluation results of "brightness," "edge coloring," and "contact area coloring" is 1. Evaluation B: The sum of the evaluation results of "brightness," "edge coloring," and "contact area coloring" is 2. Evaluation C: The sum of the evaluation results of "brightness," "edge coloring," and "contact area coloring" is 3 or more. However, if the evaluation result of any of "brightness," "edge coloring," and "contact area coloring" is 2 or more, the evaluation was rated C. Heat-treated oil compositions rated S have extremely excellent brilliance. Heat-treated oil compositions rated A have excellent brilliance. On the other hand, heat-treated oil compositions rated B have slightly inferior brilliance. Heat-treated oil compositions rated C have inferior brilliance.

[0122] (2) Oxidative Degradation Test With reference to "6.3 Stability Test Method" of JIS K2242:2012, the heat-treated oil composition was subjected to oxidative degradation by the following method. 400 mL of heat-treated oil was placed in a 730 mL (φ45 mm × length 500 mm) container, and oxidative degradation was carried out for 24 hours at a temperature of 170 ° C and an air flow rate of 10 L / h without adding a catalyst. Then, the 40 ° C kinematic viscosity of the heat-treated oil composition that was not oxidatively deteriorated (hereinafter also referred to as "new oil") and the heat-treated oil composition after oxidative degradation was measured, and the increase rate of the 40 ° C kinematic viscosity after oxidative degradation (the increase rate of the 40 ° C kinematic viscosity from the new oil) was calculated using the following formula. (40°C kinematic viscosity increase rate from new oil) = [(40°C kinematic viscosity of oil after oxidative degradation) - (40°C kinematic viscosity of new oil)] / (40°C kinematic viscosity of new oil) The greater the 40°C kinematic viscosity increase rate from new oil, the more likely the oxidative degradation of the heat-treated oil composition will progress. In other words, this means that the oxidative stability of the heat-treated oil composition is low. Conversely, the smaller the 40°C kinematic viscosity increase rate from new oil, the less likely the oxidative degradation of the heat-treated oil composition will progress. In other words, this means that the oxidative stability of the heat-treated oil composition is high.

[0123] Table 1 shows the results of the evaluation of the luster of the heat-treated oil compositions of Examples 1 to 4 and Comparative Examples 1 to 7. FIG. 2 shows the state of test pieces after a quenching test using the heat-treated oil compositions of Examples 1 to 4 and Comparative Examples 1 to 7. Table 2 shows the results of measuring the kinematic viscosity at 40°C for the heat-treated oil compositions of Examples 5 to 8 and Comparative Examples 8 to 9. Table 2 also lists the results for the heat-treated oil compositions using fresh oil and the results for the oil after a 24-hour oxidation degradation test. FIG. 3 shows the state of test pieces after a quenching test using the heat-treated oil compositions (fresh oil) of Examples 5 to 8 and Comparative Examples 8 to 9. In Tables 1 and 2, ">" means "less than."

[0124]

[0125] The following can be seen from Table 1. The results shown in Examples 1 to 4 indicate that a heat treatment oil composition with excellent brilliance of test pieces after quenching can be obtained by using a carboxylic acid compound (C) in combination with sulfides (B1), (B2), (B3), or (B4). In contrast, when the carboxylic acid compound (C) is used alone as in Comparative Example 2, or when the sulfides (B1), (B2), (B3), or (B4) are used alone as in Comparative Examples 3 to 6, the heat treatment oil composition results in poor brilliance of test pieces after quenching. Furthermore, Comparative Example 7, in which calcium sulfonate was used instead of the carboxylic acid compound (C), also results in a heat treatment oil composition with poor brilliance of test pieces after quenching.

[0126] Table 2 reveals the following. The results shown in Examples 5 to 8 show that by using a carboxylic acid compound (C) in combination with sulfides (B1), (B2), (B3), or (B4), the brilliance of the test pieces after quenching is excellent, and the oxidative degradation of the heat-treatment oil composition is less likely to progress, thereby improving the oxidative stability of the heat-treatment oil composition. In contrast, when thiophenes are used as sulfur compounds, as in Comparative Example 9, by using a carboxylic acid compound (C) in combination, the brilliance of the test pieces after quenching is excellent, but the oxidative degradation of the heat-treatment oil composition is more likely to progress, and the oxidative stability of the heat-treatment oil composition cannot be made sufficient.

Claims

1. The oil composition comprises one or more base oils (A) selected from the group consisting of mineral oils (A1), synthetic oils (A2), and vegetable oils (A3), a sulfur compound (B), and a carboxylic acid compound (C), The sulfur compound (B) includes at least one selected from the group consisting of sulfides (B1) represented by the following general formula (b1), sulfides (B2) represented by the following general formula (b2), sulfides (B3) represented by the following general formula (b3), and sulfides (B4) represented by the following general formula (b4): The heat treatment oil composition, wherein the carboxylic acid compound (C) is one or more selected from the group consisting of compounds having at least one carboxy group and their anhydrides. 【Chemistry 1】 [In the above general formula (b1), Ar １１ R represents an aryl group having 6 to 15 carbon atoms and at least a hydroxyl group. １１ represents a substituted or unsubstituted hydrocarbon group (X1), wherein the hydrocarbon group (X1) represents an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, a cycloalkenyl group having 3 to 15 carbon atoms, a cycloalkylalkyl group having 4 to 15 carbon atoms, a cycloalkenylalkyl group having 4 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, or an arylalkyl group having 7 to 15 carbon atoms. In the general formula (b2), Ar １２ R is an arylene group having 6 to 15 carbon atoms and at least a hydroxyl group. １２ and R １３ each independently represents a substituted or unsubstituted hydrocarbon group (X2), wherein the hydrocarbon group (X2) represents an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, a cycloalkenyl group having 3 to 15 carbon atoms, a cycloalkylalkyl group having 4 to 15 carbon atoms, a cycloalkenylalkyl group having 4 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, or an arylalkyl group having 7 to 15 carbon atoms. In the general formula (b3), Ar １３ represents an aryl group having 6 to 15 carbon atoms and at least a hydroxyl group. １４ represents a substituted or unsubstituted aryl group having 6 to 15 carbon atoms. In the general formula (b4), Ar １５ and Ar １６ each independently represents a substituted or unsubstituted aryl group having 6 to 15 carbon atoms.

2. The heat treatment oil composition according to claim 1, wherein in the general formula (b1), the hydrocarbon group (X1) is an aryl group having 6 to 15 carbon atoms and at least a hydroxyl group.

3. The sulfur compound (B) comprises at least one selected from the group consisting of sulfides (B1) represented by the general formula (b1), sulfides (B2) represented by the general formula (b2), and sulfides (B3) represented by the general formula (b3). The heat treatment oil composition according to claim 1 or 2.

4. The heat treatment oil composition according to claim 1 or 2, wherein the sulfur content is 10 ppm by mass to 10,000 ppm by mass based on the total amount of the heat treatment oil composition.

5. The heat treatment oil composition according to claim 1 or 2, wherein the content of the sulfur compound (B) is 0.01 mass% to 2.0 mass% based on the total amount of the heat treatment oil composition.

6. The heat treatment oil composition according to claim 1 or 2, wherein the content of the carboxylic acid compound (C) is 0.1 mass% to 5.0 mass% based on the total amount of the heat treatment oil composition.

7. The heat treatment oil composition according to claim 1 or 2, wherein the content ratio of the sulfur compound (B) to the carboxylic acid compound (C) [(B) / (C)] is 0.002 to 0.8 in mass ratio.

8. The heat treatment oil composition according to claim 1 or 2, further comprising one or more selected from the group consisting of a steam film breaker, an antioxidant, a glitter improver, and a coolability improver.

9. The heat treatment oil composition according to claim 1 or 2, which is used as a quenching oil or a tempering oil.

10. A method for using the heat treatment oil composition according to claim 1 or 2 as a quenching oil or a tempering oil.

11. The method includes a step of mixing one or more base oils (A) selected from the group consisting of mineral oils (A1), synthetic oils (A2), and vegetable oils (A3), a sulfur compound (B), and a carboxylic acid compound (C), The sulfur compound (B) includes at least one selected from the group consisting of sulfides (B1) represented by the following general formula (b1), sulfides (B2) represented by the following general formula (b2), sulfides (B3) represented by the following general formula (b3), and sulfides (B4) represented by the following general formula (b4): A method for producing a heat treatment oil composition, wherein the carboxylic acid compound (C) is one or more compounds selected from the group consisting of compounds having at least one carboxy group and their anhydrides. 【Chemistry 2】 [In the above general formula (b1), Ar １１ R each independently represents an aryl group having 6 to 15 carbon atoms and at least a hydroxyl group. １１ represents a substituted or unsubstituted hydrocarbon group (X1), wherein the hydrocarbon group (X1) represents an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, a cycloalkenyl group having 3 to 15 carbon atoms, a cycloalkylalkyl group having 4 to 15 carbon atoms, a cycloalkenylalkyl group having 4 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, or an arylalkyl group having 7 to 15 carbon atoms. In the general formula (b2), Ar １２ R represents an arylene group having 6 to 15 carbon atoms and at least a hydroxyl group. １２ and R １３ each independently represents a substituted or unsubstituted hydrocarbon group (X2), wherein the hydrocarbon group (X2) represents an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, a cycloalkenyl group having 3 to 15 carbon atoms, a cycloalkylalkyl group having 4 to 15 carbon atoms, a cycloalkenylalkyl group having 4 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, or an arylalkyl group having 7 to 15 carbon atoms. In the general formula (b3), Ar １３ represents an aryl group having 6 to 15 carbon atoms and at least a hydroxyl group. １４ represents a substituted or unsubstituted aryl group having 6 to 15 carbon atoms. In the general formula (b4), Ar １５ and Ar １６ each independently represents a substituted or unsubstituted aryl group having 6 to 15 carbon atoms.

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