Mineral oil, and process oil and grease

Abstract

[Problem] To provide a mineral oil having excellent weather resistance, and a process oil and a grease that contain said mineral oil. [Solution] A mineral oil that satisfies requirement (X1). Requirement (X1): Regarding the second derivative (A") of the absorbance (A) of the absorption spectrum of the mineral oil by wavelength (λ), the second derivative value (A"303) at 303 nm and the second derivative value (A"308) at 308 nm satisfy formula (f1).　(A"303) ≤ (A"308) … (f1)

Description

Mineral oil, process oil and grease

[0001] The present invention relates to a mineral oil, a process oil containing the mineral oil, and a grease containing the mineral oil.

[0002] Resin compositions containing resins such as rubber-based resins and thermoplastic elastomers are processed into molded articles by extrusion molding, injection molding, blow molding, calendaring, or other processes depending on the intended use and required properties of the final product. In this process, a process oil may be blended into the resin composition to improve the processability of the resin composition. The process oil acts as a so-called plasticizer. Various process oils are known. For example, Patent Document 1 describes that a thermoplastic elastomer blended with one or more selected from paraffin-based process oil, naphthene-based process oil, aromatic process oil, ester-based plasticizer, and ether-based plasticizer has excellent moldability.

[0003] Japanese Patent Application Publication No. 07-126452

[0004] Incidentally, resin compositions may be required to have decorative properties. Resin compositions that require decorative properties are required to have the ability to suppress discoloration and deterioration outdoors. From this perspective, when processing resin compositions that require decorative properties, a process oil with excellent weather resistance is required. Furthermore, greases may also be required to have weather resistance, similar to process oils.

[0005] From the viewpoint of a stable supply of process oils and greases, it is considered desirable to use mineral oils as base oils used as raw materials for these products. However, conventional mineral oils have room for further improvement in terms of weather resistance.

[0006] Therefore, an object of the present invention is to provide a mineral oil having excellent weather resistance, and a process oil and a grease containing the mineral oil.

[0007] According to the present invention, the following items [1] to [4] are provided. [1] A mineral oil that satisfies the following requirement (X1): Requirement (X1): With respect to the second derivative (A″) of the absorbance (A) of the absorption spectrum of the mineral oil with respect to the wavelength (λ), the second derivative value (A″) at 303 nm is ３０３ ) and the second derivative at 308 nm (A'' ３０８ ) satisfies the following formula (f1): (A'' ３０３ ) ≦ (A'' ３０８ ) (f1) [2] The mineral oil according to the above item [1], wherein the following component (y) satisfies the following requirement (Y1): Component (y): A component that is recovered in ethanol when the mineral oil is passed through an alumina column and then ethanol is passed through the column. Requirement (Y1): The content (C ＤＢＥ１６ ) and the content of a component (DBE19) having a double bond equivalent (DBE) of 19 (C ＤＢＥ１９ ) satisfies the following formula (f4) on a molar basis: (C ＤＢＥ１６ )>(C ＤＢＥ１９ ) (f4) [3] A process oil containing the mineral oil according to the above [1] or [2]. [4] A grease containing the mineral oil according to the above [1] or [2] and a thickener.

[0008] According to the present invention, it is possible to provide a mineral oil having excellent weather resistance, and a process oil and a grease containing the mineral oil.

[0009] 1 shows the absorption spectra of the mineral oil of Example 1 and the mineral oil of Comparative Example 1. FIG. 2 shows the second derivative (A″) of the absorbance (A) with respect to wavelength (λ) of the absorption spectra of the mineral oil of Example 1 and the mineral oil of Comparative Example 1. FIG. 3 shows the results of an analysis of the amount (actual intensity) of each double bond equivalent (DBE) for the mineral oil of Example 1 and the mineral oil of Comparative Example 1 based on Evaluation 2. FIG. 4 shows the results of an analysis of the amount (standard value) of each double bond equivalent (DBE) for the mineral oil of Example 1 and the mineral oil of Comparative Example 1 based on Evaluation 2. FIG. 5 shows the absorption spectra of the mineral oils of Examples 2 to 3 and the mineral oils of Comparative Examples 2 to 3.

[0010] The upper and lower limit values ​​of the numerical ranges described in this specification can be combined in any way. For example, when "A to B" and "C to D" are described as numerical ranges, the numerical ranges "A to D" and "C to B" are also included in the scope of the present invention. Furthermore, the numerical range "lower limit to upper limit" described in this specification means that the range is equal to or greater than the lower limit and equal to or less than the upper limit, unless otherwise specified. Furthermore, in this specification, the numerical values ​​in the examples are numerical values ​​that can be used as upper or lower limit values.

[0011] [Aspects of Mineral Oil (Requirement (X1))] The mineral oil of this embodiment satisfies the following requirement (X1): Requirement (X1): With respect to the second derivative (A″) of the absorbance (A) of the absorption spectrum of the mineral oil with respect to the wavelength (λ), the second derivative value (A″) at 303 nm is ３０３ ) and the second derivative at 308 nm (A'' ３０８ ) satisfies the following formula (f1): (A'' ３０３ ) ≦ (A'' ３０８ ) ... (f1)

[0012] Requirement (X1) clarifies that the absorption peak of unsubstituted coronene (i.e., coronene consisting only of a ring structure) observed at 308 nm in the absorption spectrum of conventional mineral oil is blue-shifted to 303 nm. In the mineral oil of this embodiment, coronene is destabilized, causing its absorption peak to blue-shift from 308 nm to 303 nm. The destabilization of coronene is thought to occur when alkyl chains are attached to coronene, and the electron-donating inductive effect of the alkyl chains has some effect on the π-electron system of the coronene. In other words, mineral oils that satisfy the requirement (X1) are thought to contain a large amount of coronene attached to alkyl chains. Therefore, it is thought that not only coronene, but also cyclic hydrocarbons with fewer rings than coronene, contain a large amount of alkyl chains attached. Therefore, the presence of the alkyl chain inhibits polycondensation between cyclic hydrocarbons with a small number of rings, making it difficult to produce polycondensates with a large number of rings and conjugated double bonds (hereinafter also referred to as "polycyclic polycondensates"), which are a factor in reducing weather resistance. Therefore, it is presumed that the mineral oil of this embodiment has excellent weather resistance.

[0013] In this specification, the second derivative (A″) of the absorbance (A) of the absorption spectrum with respect to the wavelength (λ) means the second derivative obtained by the following formula (1): A″=d ２ A / dλ ２ ....(1)

[0014] In this specification, the absorption spectrum of mineral oil can be measured using an ultraviolet-visible spectrophotometer, etc. Examples of ultraviolet-visible spectrophotometers include UV-2700 manufactured by Shimadzu Corporation, which was used in the examples described later.

[0015] In this specification, the term "cyclic hydrocarbon" refers to a hydrocarbon compound consisting of only carbon atoms and hydrogen atoms and having a cyclic structure in which the carbon atoms are bonded in a ring. Furthermore, the cyclic hydrocarbon having a small number of rings that serves as a factor (starting material) for producing a polycyclic polycondensate is a compound having one or more aromatic rings (e.g., benzene rings). The compound having one or more aromatic rings may have a cyclic structure consisting of a fused aromatic ring (e.g., fused benzene ring), or may be a condensate of an aromatic ring and an alicyclic ring (e.g., a condensate of a benzene ring and a cyclohexane ring).

[0016] From the viewpoint of obtaining a mineral oil with superior weather resistance, the requirement (X1) preferably satisfies the following formula (f1a), more preferably the following formula (f1b), and even more preferably the following formula (f1c): (A″ ３０３ ) < (A'' ３０８ )...(f1a) (A'' ３０３ ) < (A'' ３０８ )-0.01...(f1b) (A'' ３０３ ) < (A'' ３０８ )-0.02...(f1c)

[0017] [Requirements (X2) and (X3)] The mineral oil of this embodiment may satisfy the following requirement (I), but from the viewpoint of making it easier to improve weather resistance, it preferably satisfies the following requirement (II), and more preferably the following requirement (III): (I) Requirement (X1) (II) "Requirement (X1)" and "one selected from requirements (X2) and (X3)" (III) Requirements (X1), (X2), and (X3) In the following description, the above requirements (I) to (III) will also be referred to as the "requirement (X) group." Requirements (X2) and (X3) will be described in detail below.

[0018] <Requirement (X2)> Requirement (X2) is defined as follows: Requirement (X2): Second derivative value (A'') at 308 nm ３０８ ) satisfies the following formula (f2): (A'' ３０８ )>-0.01...(f2)

[0019] Requirement (X2) is a requirement indicating that the mineral oil contains a low amount of unsubstituted coronene observed at 308 nm. In addition to requirement (X1), mineral oils that satisfy requirement (X2) contain less unsubstituted coronene and more coronene with alkyl chains attached. Therefore, not only coronene, but also cyclic hydrocarbons with fewer rings than coronene, contain more alkyl chains attached. Therefore, polycondensation between cyclic hydrocarbons with fewer rings is more likely to be inhibited, making it less likely that polycyclic hydrocarbons, which can reduce weather resistance, will be produced, resulting in a mineral oil with better weather resistance.

[0020] <Requirement (X3)> Requirement (X3) is defined as follows: Requirement (X3): The maximum value (A''max) of the second derivative (A'') within the range of 306 nm or more and 310 nm or less, and the minimum value (A''min) within the range of 306 nm or more and 310 nm or less, satisfy the following formula (f3): |[(A''max) - (A''min)] / (A''max)| < 3.0 (f3) In formula (f3), the left-hand side is the absolute value of the difference between the maximum value (A''max) of the second derivative (A'') within the range of 306 nm or more and 310 nm or less and the minimum value (A''min) within the range of 306 nm or more and 310 nm or less, divided by the maximum value (A''max).

[0021] By using a mineral oil that satisfies the requirement (X3) in addition to the requirement (X1), the weather resistance of the mineral oil can be made more excellent. Also, by using a mineral oil that satisfies the requirement (X3) in addition to the requirement (X1) and the requirement (X2), the weather resistance of the mineral oil can be made even more excellent.

[0022] [Requirements (Y1) to (Y4)] From the viewpoint of further facilitating improvement in weather resistance, the mineral oil of this embodiment preferably satisfies the following (IV), more preferably the following (V), even more preferably the following (VI), and still more preferably the following (VII): (IV) Requirement (Y1) (V) "Requirement (Y1)" and "one selected from requirements (Y2), (Y3), and (Y4)" (VI) "Requirement (Y1)" and "two selected from requirements (Y2), (Y3), and (Y4)" (VII) Requirement (Y1), requirement (Y2), requirement (Y3), and requirement (Y4) In the following description, the above (IV) to (VII) will also be referred to as "requirement (Y) group."

[0023] Here, requirements (Y1) to (Y4) are all defined with respect to the following component (y). Component (y): A component recovered in ethanol when the mineral oil is passed through an alumina column and then ethanol is passed through the alumina column. Component (y) is composed of mildly polar components, including aromatic components, that are adsorbed to the alumina column among the components contained in the mineral oil of this embodiment. Requirements (Y1) to (Y4) define the relative amount of a specific DBE value for component (y). The relative amount of a specific double bond equivalent (DBE) in component (y) can be analyzed by the method described in the Examples below, using the mass-to-charge ratio (m / z) measured by field desorption-mass spectroscopy (FD-MS).

[0024] In this specification, the term "double bond equivalent (DBE)" refers to a value calculated from the following formula (2) based on the number of carbon atoms and the number of hydrogen atoms determined from the molecular weight estimated from the mass-to-charge ratio (m / z) measured by field desorption mass spectrometry. Ｎ ) + 1 - [(H Ｎ ) / 2]...(2) In the above formula (2), C Ｎ is the number of carbon atoms, and H Ｎ is the number of hydrogen atoms.

[0025] Requirements (Y1) to (Y4) will be explained in detail below.

[0026] <Requirement (Y1)> Requirement (Y1) is defined as follows: Requirement (Y1): In a component having a molecular weight of 296 to 1084, the content (C ＤＢＥ１６ ) and the content of a component (DBE19) having a double bond equivalent (DBE) of 19 (C ＤＢＥ１９ ) satisfies the following formula (f4) on a molar basis: (C ＤＢＥ１６ )>(C ＤＢＥ１９ ) ... (f4)

[0027] The mineral oil satisfying the requirement (Y1) has a content (C ＤＢＥ１９ ) with a double bond equivalent (DBE) of 16 (DBE16) ＤＢＥ１６ ) is relatively high. Mineral oils with these characteristics have suppressed decomposition of cyclic hydrocarbons and tend to have a low content of components with a double bond equivalent (DBE) of 14 or less. Components with a double bond equivalent (DBE) of 14 or less are mainly composed of cyclic hydrocarbons with a small number of rings (e.g., cyclic hydrocarbons with four or fewer rings). Cyclic hydrocarbons with a small number of rings are prone to form polycyclic polycondensates due to light or heat. As a result, the color of the mineral oil is likely to deteriorate. In other words, cyclic hydrocarbons with a small number of rings are a factor that deteriorates weather resistance. According to studies by the inventors, it has been confirmed that the mineral oil of this embodiment has a lower content of components with a double bond equivalent (DBE) of 14 or less compared to conventional mineral oils. Therefore, it is presumed that mineral oils that satisfy requirement (Y1) have a low content of cyclic hydrocarbons with a small number of rings, which are a factor that deteriorates weather resistance, and therefore have excellent weather resistance. Note that, in the past, it was generally believed that weather resistance was influenced by the amount of aromatics contained. However, in the present invention, the investigation has gone a step further and revealed that the structural distribution of aromatic compounds (the distribution of the double bond equivalents) affects color stability and weather resistance.

[0028] As described above, it is presumed that the mineral oil of this embodiment exhibits excellent weather resistance due to the fact that alkyl chains are bonded to cyclic hydrocarbons, which increases steric hindrance, and the content of cyclic hydrocarbons with a small number of rings, which are a factor that deteriorates weather resistance, is reduced.

[0029] Component (y) is mostly composed of cyclic hydrocarbons. The cyclic hydrocarbons are mostly compounds having one or more aromatic rings (e.g., benzene rings). The cyclic structure of the compound having one or more aromatic rings may be a condensed aromatic ring (e.g., condensed benzene rings), or a condensation product of an aromatic ring and an alicyclic ring (e.g., a condensation product of a benzene ring and a cyclohexane ring).

[0030] <Requirement (Y2)> Requirement (Y2) is defined as follows: Requirement (Y2): In the component having a molecular weight of 296 to 1084, the content (C ＤＢＥ１５ ) and the content of a component (DBE19) having a double bond equivalent (DBE) of 19 (C ＤＢＥ１９ ) satisfies the following formula (f5) on a molar basis: (C ＤＢＥ１５ )>(C ＤＢＥ１９ ) ... (f5)

[0031] In addition to the requirement (Y1), the mineral oil satisfying the requirement (Y2) has a content (C ＤＢＥ１９ ) with a double bond equivalent (DBE) of 16 (DBE16) ＤＢＥ１６ ), as well as the content of a component having a double bond equivalent (DBE) of 15 (DBE15) (C ＤＢＥ１５ ) are also relatively high. Mineral oils with these characteristics tend to have more suppressed decomposition of cyclic hydrocarbons and a lower content of components with a double bond equivalent (DBE) of 14 or less. Therefore, by making a mineral oil satisfy requirement (Y2) in addition to requirement (Y1), the content of cyclic hydrocarbons with a small number of rings, which are a factor that deteriorates weather resistance, can be reduced, making it easier to improve the weather resistance of the mineral oil.

[0032] <Requirement (Y3)> Requirement (Y3) is defined as follows: Requirement (Y3): In the component having a molecular weight of 296 to 1084, the content (C ＤＢＥ１６ ) and the content of a component (DBE13) having a double bond equivalent (DBE) of 13 (C ＤＢＥ１３ ) satisfies the following formula (f6) on a molar basis: (C ＤＢＥ１６ )>(C ＤＢＥ１３ ) ... (f6)

[0033] Requirement (Y3) is the content (C ＤＢＥ１３ ) is the content of a component (DBE16) having a double bond equivalent (DBE) of 16 (C ＤＢＥ１６ ) is relatively less than the requirement (Y1). Therefore, by making a mineral oil satisfy the requirement (Y3) in addition to the requirement (Y1), the weather resistance of the mineral oil can be easily improved. Furthermore, by making a mineral oil satisfy the requirement (Y3) in addition to the requirements (Y1) and (Y2), the weather resistance of the mineral oil can be easily improved.

[0034] <Requirement (Y4)> Requirement (Y4) is defined as follows: Requirement (Y4): In the component having a molecular weight of 296 to 1084, the content (C ＤＢＥ１５ ) and the content of a component (DBE13) having a double bond equivalent (DBE) of 13 (C ＤＢＥ１３ ) satisfies the following formula (f7) on a molar basis: (C ＤＢＥ１５ )>(C ＤＢＥ１３ ) ... (f7)

[0035] Requirement (Y4) is the content (C ＤＢＥ１３ ) is the content (C ＤＢＥ１５) is relatively less than the requirement (Y1). Therefore, by making a mineral oil satisfy requirement (Y4) in addition to requirement (Y1), the weather resistance of the mineral oil can be more easily improved. Furthermore, by making a mineral oil satisfy requirement (Y4) in addition to requirements (Y1) and (Y2), the weather resistance of the mineral oil can be more easily improved. Furthermore, by making a mineral oil satisfy requirement (Y4) in addition to requirements (Y1) and (Y3), the weather resistance of the mineral oil can be more easily improved. Furthermore, by making a mineral oil satisfy requirement (Y4) in addition to requirements (Y1) to (Y3), the weather resistance of the mineral oil can be more easily improved.

[0036] [Requirements (Z1) to (Z7)] The mineral oil of this embodiment preferably satisfies one or more requirements selected from the following requirements (Z1) to (Z7) in addition to the requirements (X) group and the requirements (Y) group. That is, the mineral oil of this embodiment preferably satisfies one or more requirements selected from the requirements (X) group and the following requirements (Z1) to (Z7), and more preferably satisfies the requirements (X) group, the requirements (Y) group, and one or more requirements (Z1) to (Z7).

[0037] (Requirement (Z1): Kinematic Viscosity at 40°C) Requirement (Z1) is defined as follows: Requirement (Z1): The kinematic viscosity of the mineral oil at 40°C (hereinafter also referred to as "40°C kinematic viscosity") is 25 mm ２ / s ~ 500 mm ２ / s. When the 40°C kinematic viscosity of the mineral oil is in the above range, the following advantages are obtained. When the mineral oil is used as a base oil for a process oil, evaporation and oil smoke are suppressed when the resin composition is heated when the process oil is blended with the resin composition and processed. When the mineral oil is used as a base oil for a process oil, kneading and the like are easily performed when the resin composition is blended with the process oil and processed. When the mineral oil is used as a base oil for a grease, the grease can be easily adjusted to an appropriate worked consistency. In order to make it easier to exhibit these advantages, the 40°C kinematic viscosity specified in requirement (Z1) is preferably 50 mm ２ / s~450mm ２ / s, more preferably 60 mm ２ / s~420mm ２ / s, more preferably 75 mm ２ / s~420mm ２ / s, and even more preferably 100 mm ２ / s~420mm ２ / s, and even more preferably 200 mm ２ / s~420mm ２ / s, more preferably 300 mm ２ / s~420mm ２ / s, and even more preferably 350 mm ２ / s~420mm ２ The mineral oil of this embodiment has a kinematic viscosity of 350 mm / s at 40°C. ２ / s~420mm ２ In this specification, the kinematic viscosity at 40°C of a mineral oil is a value measured in accordance with JIS K2283:2000.

[0038] (Requirement (Z2): Viscosity Index) Requirement (Z2) is defined as follows. Requirement (Z2): The viscosity index of the mineral oil is 70 or more. When the viscosity index of a mineral oil is 70 or more, the viscosity change due to temperature is likely to be small, making it easy to use in both high and low temperature ranges. From the viewpoint of making it easier to exhibit these advantages, the viscosity index defined in requirement (Z2) is preferably 75 or more, more preferably 80 or more, and even more preferably 85 or more. In addition, it is usually 150 or less. In this specification, the viscosity index of a mineral oil is a value calculated from the kinematic viscosity of the mineral oil measured in accordance with JIS K2283:2000 (for example, kinematic viscosity at 40°C and kinematic viscosity at 100°C).

[0039] (Requirement (Z3): Flash Point) Requirement (Z3) is defined as follows. Requirement (Z3): The flash point of the mineral oil is 150°C or higher. A mineral oil with a flash point of 150°C or higher has the following advantages: When a mineral oil is used as a base oil for a process oil, oily smoke is suppressed when heating is performed when blending the process oil into a resin composition and processing it. When a mineral oil is used as a base oil for a process oil or a base oil for a grease, the safety of the process oil and grease containing the base oil is ensured. Note that, from the viewpoint of making it easier to exhibit these advantages, the flash point defined in requirement (Z3) is preferably 180°C or higher, more preferably 210°C or higher, and even more preferably 240°C or higher. In addition, it is usually 400°C or lower. In this specification, the flash point of a mineral oil is a value measured by the Cleveland Open Cup (COC) method in accordance with JIS K2265-4:2007.

[0040] (Requirement (Z4):%C Ａ Requirement (Z4) is defined as follows: Requirement (Z4): % C by ring analysis (ndM method) of mineral oil Ａ When the mineral oil satisfies the requirement (Z4), the effects of the present invention are more easily exhibited. Ａ is preferably 4 or less, more preferably 3 or less, even more preferably 2 or less, still more preferably 1 or less, and even more preferably 0.1 or less.

[0041] (Requirement (Z5):%C Ｎ Requirement (Z5) is defined as follows: Requirement (Z5): % C by ring analysis (ndM method) of mineral oil Ｎ The mineral oil satisfies the requirement (Z5), and therefore the effect of the present invention is more easily exhibited. Ｎ is preferably 10 to 55, more preferably 15 to 50, and even more preferably 20 to 45.

[0042] (Requirement (Z6):%C ＰRequirement (Z6) is defined as follows: Requirement (Z6): % C by ring analysis (ndM method) of mineral oil ｐ is 30 to 100. When the mineral oil satisfies the requirement (Z6), the effects of the present invention are more easily exhibited. In addition, from the viewpoint of further facilitating the exhibiting of the effects of the present invention, the % C specified in the requirement (Z6) is ｐ is preferably 35 to 100, more preferably 40 to 100, and even more preferably 45 to 100.

[0043] (Requirement (Z7): Saybolt color (new oil)) Requirement (Z7) is defined as follows. Requirement (Z7): The Saybolt color of the mineral oil (new oil) is +25 or higher. When the Saybolt color of the mineral oil (new oil) is +25 or higher, the mineral oil can have excellent initial transparency. From the viewpoint of further enhancing the effects of the present invention, the Saybolt color of the mineral oil defined in requirement (Z7) is preferably +28 or higher, more preferably +30. In this specification, the Saybolt color of the mineral oil means a value measured in accordance with JIS K2580:2003.

[0044] [Method for Producing Mineral Oil] The mineral oil of this embodiment can be produced by making appropriate adjustments based on the matters described below.

[0045] <Preparation of Feedstock Oil> The feedstock oil used as the feedstock for the mineral oil of this embodiment preferably includes both vacuum distilled oil and vacuum residue obtained by atmospherically distilling one or more crude oils selected from paraffinic crude oil, intermediate crude oil, and naphthenic crude oil to extract fuel oil fractions such as kerosene and diesel, and then vacuum distilling the atmospheric residue remaining in the bottom of the distillation tower. The vacuum residue is preferably subjected to solvent deasphalting to obtain a solvent deasphalted oil, and then mixed with the vacuum distilled oil to be used as the feedstock oil. That is, the feedstock oil is preferably a mixture of vacuum distilled oil and deasphalted oil. Examples of solvents used in the solvent deasphalting treatment include linear saturated hydrocarbons having 3 to 6 carbon atoms, specifically propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, etc. These solvents may be used alone or in combination of two or more.

[0046] <Refining Treatment> The feedstock oil is subjected to one or more refining treatments selected from, for example, hydrocracking, solvent dewaxing, hydroisomerization dewaxing, and hydrofinishing, followed by post-treatment as described below as necessary. This produces the mineral oil of this embodiment. As the refining treatment, it is preferred to carry out at least hydrocracking, solvent dewaxing, and hydrofinishing in this order.

[0047] (Hydrocracking) Hydrocracking is a refining process carried out for the purpose of completely saturating the aromatic components contained in the feedstock oil and removing impurities such as sulfur and nitrogen components, etc. Hydrocracking is carried out in the presence of a catalyst by appropriately adjusting the hydrogen partial pressure, reaction temperature, liquid hourly space velocity, hydrogen gas supply rate, etc., so as to obtain a lubricating base oil that satisfies the above requirements.

[0048] Examples of the catalyst include catalysts containing two or more metal materials selected from nickel (Ni), tungsten (W), molybdenum (Mo), and cobalt (Co) (preferably, a metal oxide of a composite metal material containing at least nickel (Ni) and tungsten (W), a metal oxide of a composite metal material containing at least nickel (Ni) and molybdenum (Mo), and a metal oxide of a composite metal material containing at least cobalt (Co) and molybdenum (Mo)); and noble metals such as platinum (Pt) and lead (Pb). The catalyst may be used supported on a carrier. Examples of the carrier include a composite material of silica and alumina, an amorphous carrier such as alumina, and a crystalline carrier such as zeolite.

[0049] The hydrogen partial pressure in the hydrocracking treatment is preferably 15 MPa to 25 MPa. The reaction temperature in the hydrocracking treatment is preferably 300°C to 450°C. The liquid hourly space velocity (LHSV) in the hydrocracking treatment is preferably 0.5 hr －１ ~1.5 hours －１ The supply rate of hydrogen gas in hydrocracking is preferably 500 Nm per kiloliter of feed oil. ３ ~2,000 Nm ３ is.

[0050] (Solvent dewaxing treatment) Solvent dewaxing treatment is a refining treatment carried out for the purpose of removing wax contained in the feedstock oil. The solvent dewaxing treatment is carried out by appropriately adjusting various conditions so as to obtain a mineral oil that satisfies the above requirements.

[0051] Examples of solvents used in solvent dewaxing include aliphatic ketones having 3 to 6 carbon atoms, such as methyl ethyl ketone and methyl isobutyl ketone; aliphatic hydrocarbons having 3 to 6 carbon atoms, such as propane and butane; and toluene. The cooling temperature in solvent dewaxing is preferably −40 to 0° C. The wax precipitated by cooling (slack wax) is separated from the liquid fraction (solvent and treated oil) by filtration. The solvent is then removed from the liquid fraction to obtain solvent-dewaxed oil.

[0052] (Hydroisomerization dewaxing) Hydroisomerization dewaxing is a refining process carried out for the purpose of isomerizing linear paraffins contained in a feedstock oil to isoparaffins. Hydroisomerization dewaxing can also open the rings of aromatic components to form paraffins and remove impurities such as sulfur and nitrogen. Here, hydroisomerization dewaxing may be carried out on the wax (slack wax) separated from the feedstock oil, and the hydroisomerized dewaxed oil derived from the wax may be mixed with a solvent dewaxed oil. Alternatively, only the hydroisomerized dewaxed oil may be subjected to the hydrofinishing process described below. Hydroisomerization dewaxing is carried out in the presence of a catalyst, with the hydrogen partial pressure, reaction temperature, liquid hourly space velocity, and hydrogen gas supply rate appropriately adjusted to obtain a mineral oil that satisfies the above requirements.

[0053] The catalyst may be the same as that used in hydrocracking.

[0054] The hydrogen partial pressure in the hydroisomerization dewaxing treatment is preferably 2 MPa to 6 MPa. The reaction temperature in the hydroisomerization dewaxing treatment is preferably 250°C to 350°C. The liquid hourly space velocity (LHSV) in the hydroisomerization dewaxing treatment is preferably 0.2 hr －１ ~1.5 hours －１ The supply rate of hydrogen gas in the hydroisomerization dewaxing treatment is preferably 300 Nm per kiloliter of feed oil. ３ ~600Nm ３ is.

[0055] (Hydrofinishing Treatment) Similar to the hydrocracking treatment described above, hydrofinishing treatment is a refining treatment carried out for the purpose of completely saturating the aromatic components contained in the feedstock oil and removing impurities such as sulfur and nitrogen components. Hydrofinishing treatment is carried out in the presence of a catalyst by appropriately adjusting the hydrogen partial pressure, reaction temperature, liquid hourly space velocity, hydrogen gas supply rate, etc., so as to obtain a mineral oil that satisfies the above requirements.

[0056] Examples of the catalyst include those similar to those used in hydrocracking. That is, examples include catalysts containing two or more metal materials selected from nickel (Ni), tungsten (W), molybdenum (Mo), and cobalt (Co). Among these, metal oxides of composite metal materials containing at least nickel (Ni) and tungsten (W) are preferred, and tungsten-containing nickel catalysts containing at least nickel (Ni) and tungsten (W) (hereinafter, also simply referred to as "tungsten-containing nickel catalysts") are more preferred.

[0057] The hydrogen partial pressure in the hydrofinishing treatment is preferably 15 MPa to 25 MPa. The reaction temperature in the hydrofinishing treatment is preferably 200°C to 350°C. The liquid hourly space velocity (LHSV) in the hydrofinishing treatment is preferably 0.2 hr －１ ~1.5 hours －１ The supply rate of hydrogen gas in the hydrofinishing treatment is preferably 500 Nm per kiloliter of feed oil. ３ ~2,000 Nm ３ is.

[0058] After the refining process is completed, the resulting product oil is subjected to vacuum distillation, and the fraction is recovered so as to have a desired kinematic viscosity (preferably so as to satisfy the above requirement (Z1)), thereby obtaining the mineral oil of this embodiment. The conditions for vacuum distillation (pressure, temperature, time, etc.) are appropriately adjusted so that the kinematic viscosity of the resulting mineral oil falls within the desired range.

[0059] [Uses of Mineral Oil] The mineral oil of this embodiment has excellent weather resistance. Therefore, it can be used as a lubricating base oil that requires excellent weather resistance. Suitable examples of the lubricating base oil include base oils for process oils and base oils for greases. Therefore, the mineral oil of this embodiment provides the following uses. (1) A use method in which the mineral oil of this embodiment is used as a base oil for process oils. (2) A use method in which the mineral oil of this embodiment is used as a base oil for greases.

[0060] Furthermore, the mineral oil of this embodiment provides a process oil containing the mineral oil of this embodiment and a grease containing the mineral oil of this embodiment. The process oil containing the mineral oil of this embodiment and the grease containing the mineral oil of this embodiment will be described in detail below.

[0061] <Process Oil> The process oil of this embodiment contains the mineral oil of this embodiment described above. In the description of the process oil, the mineral oil of this embodiment will be referred to as "mineral oil (M1)".

[0062] (Mineral Oil (M1)) The process oil of this embodiment contains a mineral oil (M1). By containing the mineral oil (M1), the process oil of this embodiment exhibits excellent weather resistance. The mineral oil (M1) may be used alone or in combination of two or more. Here, in the process oil of this embodiment, the content of the mineral oil (MO) is preferably 70% by mass to 100% by mass, 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 process oil.

[0063] (Components Other Than Mineral Oil (M1)) The process oil of this embodiment may or may not contain components other than the mineral oil (M1), as long as the effects of the present invention are not significantly impaired. Examples of such components include base oils other than the mineral oil (M1) and various additives for process oils.

[0064] Examples of base oils other than mineral oil (M1) include mineral oils and synthetic oils that do not fall under the category of mineral oil (M1). Examples of such synthetic oils include hydrocarbon oils, aromatic oils, ester oils, ether oils, and synthetic oils obtained by isomerizing wax (GTL wax) produced by the Fischer-Tropsch process. Mineral oils and synthetic oils that do not fall under the category of mineral oil (M1) may be used alone or in combination of two or more. From the viewpoint of improving the weather resistance of the process oil, the content of mineral oil (M1) in the base oil constituting the process oil is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, even more preferably 70% by mass to 100% by mass, still 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 constituting the process oil.

[0065] Examples of various additives for process oil include antioxidants. The various additives for process oil may be used singly or in combination of two or more. The contents of the various additives for process oil in the process oil of this embodiment are appropriately adjusted depending on the type and application of the additive, but are each independently typically 0 to 10 mass%, preferably 0.001 to 7 mass%, and more preferably 0.01 to 5 mass%, based on the total amount of the process oil.

[0066] <Grease> The grease of this embodiment contains the mineral oil of this embodiment described above and a thickener. In the description of the grease, the mineral oil of this embodiment will be referred to as "mineral oil (M2)." The grease of this embodiment contains mineral oil (M2) that has excellent weather resistance. Therefore, it has excellent weather resistance compared to conventional greases.

[0067] The grease of this embodiment may or may not contain components other than the mineral oil (M2) and the thickener, as long as the effects of the present invention are not impaired. In this embodiment, the total content of the mineral oil (M2) and the thickener is preferably 70% by mass to 100% by mass, 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 grease.

[0068] (Mineral Oil (M2)) The grease of this embodiment contains a mineral oil (M2). By containing the mineral oil (M2), the grease of this embodiment exhibits excellent weather resistance. One type of mineral oil (M2) may be used alone, or two or more types may be used in combination. Here, in the grease of this embodiment, the content of the mineral oil (M2) is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 75% by mass, based on the total amount of the grease. Also, it is preferably 99% by mass or less, more preferably 97% by mass or less, and even more preferably 95% by mass or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 50% by mass to 99% by mass, more preferably 60% by mass to 97% by mass, and even more preferably 70% by mass to 95% by mass.

[0069] <Thickener> The grease of this embodiment contains a thickener. Examples of thickeners in the grease of this embodiment include metal soaps, metal complex soaps, cellulose nanofibers, and urea-based compounds. One type of thickener may be used alone, or two or more types may be used in combination. In the grease of this embodiment, the content of the thickener is preferably 1 to 40 mass%, more preferably 3 to 30 mass%, and even more preferably 5 to 25 mass%, based on the total amount of the grease.

[0070] <Components Other Than Mineral Oil (M2) and Thickener> The grease of this embodiment may or may not contain components other than the mineral oil (M2) and the thickener, as long as the effects of the present invention are not significantly impaired. Examples of such components include base oils other than the mineral oil (M2) and various additives for greases.

[0071] Examples of base oils other than mineral oil (M2) include mineral oils and synthetic oils that do not fall under the category of mineral oil (M2). Examples of such synthetic oils include hydrocarbon oils, aromatic oils, ester oils, ether oils, and synthetic oils obtained by isomerizing wax (GTL wax) produced by the Fischer-Tropsch process. Mineral oils and synthetic oils that do not fall under the category of mineral oil (M2) may be used alone or in combination of two or more. From the viewpoint of improving the weather resistance of the grease, the content of mineral oil (MO) in the base oil constituting the grease is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, even more preferably 70% by mass to 100% by mass, still 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 constituting the grease.

[0072] Examples of various additives for grease include antioxidants, rust inhibitors, extreme pressure agents, oiliness agents, antiwear agents, thickeners, solid lubricants, detergent dispersants, corrosion inhibitors, and metal deactivators. The various additives for grease may be used singly or in combination of two or more. The content of each of the various grease additives in the grease of this embodiment is adjusted appropriately depending on the type and application of the additive, but is typically 0 to 10 mass%, preferably 0.001 to 7 mass%, and more preferably 0.01 to 5 mass%, based on the total amount of the grease.

[0073] [An aspect of the present invention provided] According to one aspect of the present invention, the following [1] to

[11] are provided. [1] A mineral oil that satisfies the following requirement (X1): Requirement (X1): With respect to the second derivative (A″) of the absorbance (A) of the absorption spectrum of the mineral oil with respect to the wavelength (λ), the second derivative value (A″) at 303 nm is３０３ ) and the second derivative at 308 nm (A'' ３０８ ) satisfies the following formula (f1): (A'' ３０３ ) ≦ (A'' ３０８ ) (f1) [2] The mineral oil according to the above [1], further satisfying the following requirement (X2): Requirement (X2): second derivative value (A'') at 308 nm ３０８ ) satisfies the following formula (f2): (A'' ３０８ ) > -0.01 (f2) [3] The mineral oil according to the above item [1] or [2], further satisfying the following requirement (X3): Requirement (X3): The maximum value (A''max) of the second derivative value (A'') within the range of 306 nm or more and 310 nm or less and the minimum value (A''min) within the range of 306 nm or more and 310 nm or less satisfy the following formula (f3): |[(A''max) - (A''min)] / (A''max)| < 3.0 (f3) [4] The mineral oil according to any one of the above items [1] to [3], wherein the following component (y) satisfies the following requirement (Y1): Component (y): A component that is recovered in ethanol when ethanol is passed through an alumina column after the mineral oil is passed through the column. Requirement (Y1): In the component having a molecular weight of 296 to 1084, the content of a component (DBE16) having a double bond equivalent (DBE) of 16 (C ＤＢＥ１６ ) and the content of a component (DBE19) having a double bond equivalent (DBE) of 19 (C ＤＢＥ１９ ) satisfies the following formula (f4) on a molar basis: (C ＤＢＥ１６ )>(C ＤＢＥ１９ ) (f4) [5] The mineral oil according to the above [4], wherein the component (y) further satisfies the following requirement (Y2): Requirement (Y2): In the component having a molecular weight of 296 to 1084, the content (C ＤＢＥ１６ ) and the content of a component (DBE19) having a double bond equivalent (DBE) of 19 (C ＤＢＥ１９ ) satisfies the following formula (f5) on a molar basis: (C ＤＢＥ１５ )>(C ＤＢＥ１９) (f5) [6] The mineral oil according to the above [4] or [5], wherein the component (y) further satisfies the following requirement (Y3): Requirement (Y3): In the component having a molecular weight of 296 to 1084, the content (C ＤＢＥ１６ ) and the content of a component (DBE13) having a double bond equivalent (DBE) of 13 (C ＤＢＥ１３ ) satisfies the following formula (f6) on a molar basis: (C ＤＢＥ１６ )>(C ＤＢＥ１３ ) (f6) [7] The mineral oil according to any one of the above [4] to [6], wherein the component (y) further satisfies the following requirement (Y4): Requirement (Y4): In the component having a molecular weight of 296 to 1084, the content (C ＤＢＥ１５ ) and the content of a component (DBE13) having a double bond equivalent (DBE) of 13 (C ＤＢＥ１３ ) satisfies the following formula (f7) on a molar basis: (C ＤＢＥ１５ )>(C ＤＢＥ１３ ) ... (f7) [8] The mineral oil according to any one of the above [1] to [7], used as a base oil for process oil. [9] The mineral oil according to any one of the above [1] to [7], used as a base oil for grease.

[10] A process oil containing the mineral oil according to any one of the above [1] to [7].

[11] A grease containing the mineral oil according to any one of the above [1] to [7] and a thickener.

[0074] The present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples.

[0075] [Example 1, Comparative Example 1] The mineral oil of Example 1 and the mineral oil of Comparative Example 1 were evaluated for the following physical properties (1) to (4). In addition, the following evaluations 1 and 2 were also performed.

[0076] Example 1 The mineral oil of Example 1 was produced by the following method. Using vacuum distilled oil and solvent deasphalted oil as feedstocks, a nickel-tungsten-alumina catalyst (a catalyst in which nickel oxide and tungsten oxide are supported on an alumina carrier) was used, at a reaction temperature of 360 to 410°C, a hydrogen partial pressure of 20 MPa, and a hydrogen to feedstock supply ratio of 900 Nm ３ / kL, LHSV 0.9hr －１ A refined oil was obtained by hydrocracking under the following conditions. Next, the refined oil was mixed with toluene and methyl ethyl ketone and cooled to -20°C or below. The precipitated wax was removed, and then the toluene and methyl ethyl ketone were removed to obtain a dewaxed oil. Next, the dewaxed oil was subjected to hydrocracking using a tungsten-containing nickel catalyst at a reaction temperature of 300°C, a hydrogen partial pressure of 20 MPa, and a hydrogen to dewaxed oil feed ratio of 1,000 Nm ３ / kL, LHSV 0.4hr －１ The target fraction was then recovered by vacuum distillation to obtain the mineral oil of Example 1.

[0077] Comparative Example 1 The mineral oil of Comparative Example 1 was produced by the following method. Using vacuum distilled oil and solvent deasphalted oil as feedstocks, a nickel-tungsten-alumina catalyst (a catalyst in which nickel oxide and tungsten oxide are supported on an alumina carrier) was used, at a reaction temperature of 360 to 410°C, a hydrogen partial pressure of 20 MPa, and a hydrogen to feedstock supply ratio of 900 Nm ３ / kL, LHSV 0.9hr －１ The refined oil was subjected to hydrocracking treatment under the conditions of (a) to (b) above, and a refined oil was obtained. Next, the refined oil was mixed with toluene and methyl ethyl ketone and cooled to -20°C or below. The precipitated wax was removed, and then the toluene and methyl ethyl ketone were removed to obtain a dewaxed oil. Next, the dewaxed oil was subjected to hydrocracking treatment using a nickel-molybdenum-alumina catalyst (a catalyst in which nickel oxide and molybdenum oxide are supported on an alumina carrier) at a reaction temperature of 310°C, a hydrogen partial pressure of 20 MPa, and a hydrogen to dewaxed oil feed ratio of 1,000 Nm ３ / kL, LHSV 0.4hr －１ The target fraction was then recovered by vacuum distillation to obtain the mineral oil of Comparative Example 1.

[0078] [Measurement of various physical properties] (1) 40°C kinematic viscosity and viscosity index: Measured and calculated in accordance with JIS K2283:2000. (2) Flash point: Measured by the Cleveland open cup (COC) method in accordance with JIS K 2265-4:2007. (3) Various physical properties obtained by ring analysis: %C was measured by ring analysis (nd-M method) in accordance with ASTM D3238-95. Ａ , %C Ｎ , and %C Ｐ (4) Saybolt color: Measured in accordance with JIS K2580:2003

[0079] The results of measuring various physical properties of the mineral oils of Example 1 and Comparative Example 2 are shown in Table 1.

[0080]

[0081] [Evaluation 1: Evaluation by Absorption Spectrum] The absorption spectra of the mineral oils of Example 1 and Comparative Example 2 were measured using an ultraviolet-visible spectrophotometer (Shimadzu Corporation, UV-2700). Then, using the obtained absorption spectra, the second derivative (A″) of absorbance (A) with respect to wavelength (λ) was calculated, and the second derivative value (A″) at 303 nm was calculated. ３０３ ) and the second derivative at 308 nm (A'' ３０８ ) were calculated. Furthermore, the maximum value (A''max) of the second derivative value (A'') within the range of 306 nm or more and 310 nm or less, and the minimum value (A''min) within the range of 306 nm or more and 310 nm or less were determined. Using these values, it was examined whether the mineral oils of Example 1 and Comparative Example 2 satisfied the above formulas (f1) to (f3). The absorption spectrum is shown in Figure 1, and the second derivative (A'') of the absorption spectrum is shown in Figure 2. The examination results are also shown in Table 2. In Table 2, "S" means that the formula at the left end of Table 2 is satisfied, and "N" means that the formula at the left end of Table 2 is not satisfied.

[0082]

[0083] The following can be seen from Table 2. The mineral oil of Example 1 satisfies formula (f1) and the above-mentioned requirement (X1), and is therefore thought to contain a large amount of coronenes bonded to alkyl chains. Therefore, it is thought that the mineral oil also contains a large amount of cyclic hydrocarbons with fewer rings than coronene, with alkyl chains bonded to them. Therefore, it is presumed that the presence of the alkyl chains inhibits polycondensation between cyclic hydrocarbons with fewer rings, making it difficult for polycyclic cyclic hydrocarbons to be produced, resulting in a mineral oil with excellent weather resistance. In contrast, the mineral oil of Comparative Example 1 does not satisfy formula (f1) and does not satisfy the above-mentioned requirement (X1). Therefore, it is thought that the mineral oil contains less coronenes bonded to alkyl chains and more unsubstituted coronenes. Therefore, it is thought that the mineral oil also contains a large amount of unsubstituted cyclic hydrocarbons, even among cyclic hydrocarbons with fewer rings than coronene. Therefore, it is presumed that polycondensation between cyclic hydrocarbons with fewer rings is more likely to occur, making it easier for polycyclic cyclic hydrocarbons to be produced, resulting in a mineral oil with poor weather resistance. Furthermore, the mineral oil of Example 1 satisfies the formulas (f2) and (f3) and also satisfies the above requirements (X2) and (X3), and is therefore a mineral oil with superior weather resistance.

[0084] [Evaluation 2: Evaluation by double bond equivalent (DBE)] <Pretreatment of mineral oil> The mineral oils of Example 1 and Comparative Example 2 were pretreated in the following order (1) to (4). (1) The mineral oils of Example 1 and Comparative Example 2 were each passed through an alumina column. (2) Ethanol was passed through the alumina column to recover component (y). (3) After removing the ethanol with an evaporator, the residue was diluted with chloroform and applied to an emitter. (4) After drying the component applied to the emitter, measurement was performed using field desorption mass spectrometry (FD-MS, manufactured by JEOL Ltd., JMS-700 MStation).

[0085] <Analysis> Molecular formulas assumed for molecules composed of carbon and hydrogen atoms were comprehensively created from C20 to C90, and mass numbers were calculated. Taking the above pretreatment conditions into consideration, components that could not exist as component (y), such as molecules not containing unsaturated bonds and nonpolar molecules (e.g., molecules primarily composed of naphthenic or paraffinic structures, molecules with extremely large DBEs, such as coke), were excluded. These were then arranged in order of molecular weight, and the structure with a molecular weight ranging from 296 to 1084 that was most likely to match the molecular weight estimated from the mass-to-charge ratio (m / z) obtained by field desorption mass spectrometry (FD-MS) was determined, and its DBE was determined. The abundance of each molecule with a DBE was then calculated by summing the peak intensities at the FD-MS mass-to-charge ratio (m / z) that was most likely to match the molecular weight of the molecule.

[0086] Table 3 shows the amount of molecules present (actual intensity values) for each DBE for the mineral oils of Example 1 and Comparative Example 1. A plot of Table 3 is shown in Figure 3. Furthermore, Figure 4 shows the results of calculating the composition ratios (standard values) of molecules for each DBE when the sum of the peak intensities in the DBE range of 13 to 25 is set to 1.00 for the results of Table 3. The smaller the DBE, the fewer the number of rings in the cyclic hydrocarbon tends to be, and the larger the DBE, the greater the number of rings in the cyclic hydrocarbon tends to be.

[0087]

[0088] The following can be seen from Table 3 and FIG. 3. Compared to the mineral oil of Comparative Example 1, the mineral oil of Example 1 contains fewer components with a double bond equivalent (DBE) of 14 or less, and therefore contains fewer cyclic hydrocarbons with a small number of rings, which are factors that deteriorate weather resistance. Furthermore, the following can be seen from FIG. 4. The mineral oil of Example 1 satisfies requirement (Y1) (and also requirements (Y2) to (Y4)). On the other hand, the mineral oil of Comparative Example 1 does not satisfy requirement (Y1) (and also requirements (Y2) to (Y4)). Therefore, when considered comprehensively in light of the results shown in Table 3 and FIG. 3, it can be seen that mineral oils that satisfy requirement (Y1) (and also requirements (Y2) to (Y4)), like the mineral oil of Example 1, contain fewer components with a double bond equivalent (DBE) of 14 or less, and therefore contain fewer cyclic hydrocarbons with a small number of rings, which are factors that deteriorate weather resistance, and therefore have excellent weather resistance.

[0089] [Examples 2-3, Comparative Examples 2-3] The various physical properties (1) to (4) above were evaluated for the mineral oil of Example 2 and the mineral oil of Comparative Example 2. In addition, the above-mentioned Evaluation 1 and the following Evaluation 3 were also performed.

[0090] Example 2 Another lot obtained in the same manner as in Example 1 was used as the mineral oil of Example 2.

[0091] Example 3 The mineral oil of Example 3 was obtained in the same manner as in Example 1, except that the target fraction recovered by vacuum distillation was varied.

[0092] Comparative Example 2 Another lot obtained in the same manner as in Comparative Example 1 was used as the mineral oil of Comparative Example 2.

[0093] Comparative Example 3 The mineral oil of Comparative Example 3 was obtained in the same manner as in Comparative Example 1, except that the target fraction recovered by vacuum distillation was changed.

[0094] [Evaluation 3: Weathering Resistance Test (Photothermal Test)] The weathering resistance of the mineral oils of Examples 2 and 3 and the mineral oils of Comparative Examples 2 and 3 was evaluated by a photothermal test. In the photothermal test, 80 cc of the test oil was placed in a 100 cc glass container (glass bottle), and the oil temperature was maintained at 65°C. The test oil was irradiated with light from a xenon lamp (765 W / m) from above the glass bottle. ２ ) for 24 hours, and then the Saybolt color was measured.

[0095] The measurement results of various physical properties of the mineral oils of Examples 2-3 and Comparative Examples 2-3 and the results of Evaluation 3 above are shown in Table 4. The absorption spectra of the mineral oils of Examples 2-3 and Comparative Examples 2-3 are shown in FIG.

[0096]

[0097] From the shapes of the absorption spectra shown in Figure 5, it is estimated that the second derivatives of the absorption spectra of Examples 2 and 3 satisfy formula (f1) and therefore satisfy the above-mentioned requirement (X1). On the other hand, it is estimated that the second derivatives of the absorption spectra of Comparative Examples 2 and 3 do not satisfy formula (f1) and therefore do not satisfy the above-mentioned requirement (X1). Next, the following can be seen from the results shown in Table 4. It can be seen that the mineral oil of Example 2 is superior in weather resistance compared to the mineral oil of Comparative Example 2. It can also be seen that the mineral oil of Example 3 is superior in weather resistance compared to the mineral oil of Comparative Example 3.

Claims

1. A mineral oil that satisfies the following requirement (X1). Requirement (X1): The second derivative (A″) of the absorbance (A) of the absorption spectrum of the mineral oil with respect to the wavelength (λ) has a second derivative value (A″) at 303 nm. ３０３ ) and the second derivative at 308 nm (A'' ３０８ ) satisfies the following formula (f1). (A'' ３０３ )≦(A'' ３０８ )・・・(f1)

2. The mineral oil according to claim 1, further satisfying the following requirement (X2): Requirement (X2): Second derivative value (A'') at 308 nm ３０８ ) satisfies the following formula (f2). (A’’ ３０８ )>-0.01・・・(f2)

3. The mineral oil according to claim 1 or 2, further satisfying the following requirement (X3): Requirement (X3): The maximum value (A″max) of the second derivative (A″) within the range of 306 nm or more and 310 nm or less, and the minimum value (A″min) within the range of 306 nm or more and 310 nm or less, satisfy the following formula (f3). |[(A''max)-(A''min)] / (A''max)|<3.0...(f3)

4. 3. The mineral oil according to claim 1 or 2, A mineral oil in which the following component (y) satisfies the following requirement (Y1). Component (y): This component is recovered in ethanol when the mineral oil is passed through an alumina column and then ethanol is passed through the column. Requirement (Y1): In the component having a molecular weight of 296 to 1084, the content of a component (DBE16) having a double bond equivalent (DBE) of 16 (C ＤＢＥ１６ ) and the content of a component (DBE19) having a double bond equivalent (DBE) of 19 (C ＤＢＥ１９ ) satisfy the following formula (f4) on a molar basis. (C ＤＢＥ１６ )>(C ＤＢＥ１９ )・・・(f4)

5. 5. The mineral oil of claim 4, The mineral oil, wherein the component (y) further satisfies the following requirement (Y2): Requirement (Y2): In the component having a molecular weight of 296 to 1084, the content of a component having a double bond equivalent (DBE) of 15 (DBE15) (C ＤＢＥ１５ ) and the content of a component (DBE19) having a double bond equivalent (DBE) of 19 (C ＤＢＥ１９ ) satisfy the following formula (f5) on a molar basis. (C ＤＢＥ１５ )>(C ＤＢＥ１９ )・・・(f5)

6. 5. The mineral oil of claim 4, The mineral oil, wherein the component (y) further satisfies the following requirement (Y3): Requirement (Y3): In the component having a molecular weight of 296 to 1084, the content of a component (DBE16) having a double bond equivalent (DBE) of 16 (C ＤＢＥ１６ ) and the content of a component (DBE13) having a double bond equivalent (DBE) of 13 (C ＤＢＥ１３ ) satisfy the following formula (f6) on a molar basis. (C ＤＢＥ１６ )>(C ＤＢＥ１３ )・・・(f6)

7. 5. The mineral oil of claim 4, The mineral oil, wherein the component (y) further satisfies the following requirement (Y4): Requirement (Y4): The content of a component (DBE15) having a double bond equivalent (DBE) of 15 in a component having a molecular weight of 296 to 1084 (C ＤＢＥ１５ ) and the content of a component (DBE13) having a double bond equivalent (DBE) of 13 (C ＤＢＥ１３ ) satisfy the following formula (f7) on a molar basis. (C ＤＢＥ１５ )>(C ＤＢＥ１３ )・・・(f7)

8. 3. The mineral oil according to claim 1 or 2, which is used as a base oil for process oils.

9. 3. The mineral oil according to claim 1 or 2, which is used as a base oil for grease.

10. A process oil comprising the mineral oil according to claim 1 or 2.

11. A grease comprising the mineral oil according to claim 1 or 2 and a thickener.