Electrically insulating oil composition

Abstract

Provided is an electrically insulating oil composition that satisfies the requirements (1) to (3) indicated below. · Requirement (1): %CA as determined through ring analysis (the n-d-M method) is 5.5% or less. · Requirement (2): The sulfur atom content with reference to the total amount of the electrically insulating oil composition is 20 mass ppm or more. · Requirement (3): The pour point is -50.0°C or lower.

Description

Electrical insulating oil composition

[0001] The present invention relates to an electrical insulating oil composition and a method for using the electrical insulating oil composition.

[0002] Electrical insulating oil compositions are used as insulating materials for oil-filled electrical equipment such as oil-filled capacitors, oil-filled cables, oil-filled transformers, and oil-filled circuit breakers. For example, Patent Document 1 discloses an invention relating to an electrical insulating oil composition obtained by a gas-to-liquid process or a lubricating oil fraction separated from said synthetic wax, which is subjected to predetermined hydrocracking and hydroisomerization dewaxing treatments to adjust the volume resistivity at 80°C and 25°C to a predetermined range.

[0003] Special Publication No. 2014-196391

[0004] In recent years, electrical insulating oil compositions are sometimes used in cold regions, and therefore good low-temperature fluidity is required. Furthermore, electrical insulating oil compositions intended for use outside of Japan are also required to have high oxidation stability as specified in IEC (International Electrical Commission) 60296:2020 (hereinafter also simply referred to as "IEC 60296"). Under these circumstances, one aspect of the present invention aims to provide an electrical insulating oil composition that is excellent in low-temperature fluidity and oxidation stability, for example.

[0005] This invention relates to %C obtained by ring analysis (n-d-M method). Ａ The present invention provides an electrical insulating oil composition in which the sulfur atom content and pour point are adjusted to a predetermined range, and a method for using the electrical insulating oil composition. Specifically, the present invention relates to the following aspects: [1] An electrical insulating oil composition that satisfies the following requirements (1) to (3): Requirement (1): %C by ring analysis (n-d-M method) Ａ The content is 6.0% or less. Requirement (2): The sulfur atom content is 20 ppm by mass or more on a total basis of the electrical insulating oil composition. Requirement (3): The pour point is -50.0°C or lower. [2] The electrical insulating oil composition described in [1] above, which further satisfies the following requirement (4). Requirement (4): %C by ring analysis (n-d-M method) Ｎ and %C Ｐ Ratio to [%C]Ｎ / % C Ｐ is less than 1.0. [3] The electrical insulating oil composition according to [1] or [2] above, further satisfying the following requirement (5). - Requirement (5): % C by ring analysis (n-d-M method) Ｎ is less than 50.0%. [4] % C defined in requirement (1) Ａ is less than 3.5%, the electrical insulating oil composition according to any one of [1] to [3] above. [5] The electrical insulating oil composition according to any one of [1] to [4] above, further satisfying the following requirement (6). - Requirement (6): The ratio [S / % C Ａ (unit: %) of the sulfur atom content (unit: mass ppm) and % C by ring analysis (n-d-M method) Ａ is 8.0 to 40.0. [6] The electrical insulating oil composition according to any one of [1] to [5] above, further satisfying the following requirement (7). - Requirement (7): The Saybolt color is +10 or more. [7] The electrical insulating oil composition according to any one of [1] to [6] above, containing a low-sulfur type mineral oil (α) with a sulfur atom content of 50 mass ppm or less and a high-sulfur type mineral oil (β) with a sulfur atom content of more than 50 mass ppm. [8] The electrical insulating oil composition according to [7] above, wherein the low-sulfur type mineral oil (α) satisfies the following requirement (α1). - Requirement (α1): The pour point is -40.0 °C or lower. [9] The electrical insulating oil composition according to [7] or [8] above, wherein the low-sulfur type mineral oil (α) satisfies the following requirement (α2). - Requirement (α2): % C by ring analysis (n-d-M method) Ａ is less than 4.5%.

[10] The electrical insulating oil composition according to any one of [7] to [9] above, wherein the low-sulfur type mineral oil (α) satisfies the following requirement (α3). - Requirement (α3): The ratio [% C Ｎ and % C Ｐ and the ratio [% C Ｎ / % C Ｐ] is less than 1.0.

[11] An electrical insulating oil composition according to any one of the above items [7] to

[10] , wherein the high-sulfur mineral oil (β) satisfies the following requirement (β1). Requirement (β1): The pour point is -40.0°C or lower.

[12] An electrical insulating oil composition according to any one of the above items [7] to

[11] , wherein the high-sulfur mineral oil (β) satisfies the following requirement (β2). Requirement (β2): %C by ring analysis (n-d-M method) Ａ The content is 4.5% or more.

[13] An electrical insulating oil composition according to any one of the above items [7] to

[12] , wherein the high-sulfur mineral oil (β) satisfies the following requirement (β3). Requirement (β3): %C by ring analysis (n-d-M method) Ｎ and %C Ｐ Ratio to [%C] Ｎ / %C Ｐ

[14] An electrical insulating oil composition according to any one of the above items [7] to

[13] , wherein the content ratio of low-sulfur mineral oil (α) to high-sulfur mineral oil (β) [(α) / (β)] is 40 / 60 or more and less than 95 / 5 by mass ratio.

[15] An electrical insulating oil composition according to any one of the above items [7] to

[14] , wherein the content of high-sulfur mineral oil (β) is 7 to 25% by mass on a total basis of the electrical insulating oil composition.

[16] An electrical insulating oil composition according to any one of the above items [1] to

[15] , wherein the acid value after conducting an oxidation stability test based on IEC 61125:2018 for 164 hours is less than 1.00 mg KOH / g.

[17] A method of using an electrical insulating oil composition, wherein the electrical insulating oil composition according to any one of the above items [1] to

[16] is used as an insulating material for oil-filled electrical equipment.

[0006] A preferred embodiment of the present invention provides an electrical insulating oil composition that exhibits excellent low-temperature fluidity and oxidation stability, and can be suitably used as an insulating material for oil-filled electrical equipment.

[0007] The numerical ranges described herein can be any combination of upper and lower limits. For example, if the numerical range is described as "preferably 30 to 100, more preferably 40 to 80," then the ranges of "30 to 80" and "40 to 100" are also included in the numerical range described herein. Similarly, if the numerical range is described as "preferably 30 or more, more preferably 40 or more, and also preferably 100 or less, more preferably 80 or less," then the ranges of "30 to 80" and "40 to 100" are also included in the numerical range described herein. In addition, for example, if the numerical range described herein is described as "60 to 100," then it means the range is "60 or more (60 or greater than 60), and 100 or less (100 or less than 100)."

[0008] In this specification, kinematic viscosity and viscosity index refer to values ​​measured and calculated in accordance with JIS K2283:2000.

[0009] [Composition of the Electrical Insulating Oil Composition] The electrical insulating oil composition according to one aspect of the present invention preferably contains a mineral oil-based base oil as its main component, but may also contain synthetic oils other than mineral oil-based base oils, or additives such as antioxidants. In the electrical insulating oil composition according to one aspect of the present invention, the content of the mineral oil-based base oil may be 80.0% by mass or more, 85.0% by mass or more, 90.0% by mass or more, 95.0% by mass or more, 96.0% by mass or more, 97.0% by mass or more, 98.0% by mass or more, 99.0% by mass or more, 99.2% by mass or more, 99.4% by mass or more, 99.6% by mass or more, 99.7% by mass or more, 99.8% by mass or more, 99.90% by mass or more, 99.92% by mass or more, more than 99.92% by mass, or 100% by mass, based on the total amount (100% by mass) of the electrical insulating oil composition.

[0010] Furthermore, according to IEC 60296:2020 Ed. 5, electrical insulating oils are classified into "additive-free oil," "trace-added oil," and "added oil" based on the amount of antioxidant added, as follows: ・"Additive-free oil": The amount of antioxidant added is less than 0.01% by mass on a basis of the total amount of the composition. ・"Trace-added oil": The amount of antioxidant added is 0.01% by mass or more and less than 0.08% by mass on a basis of the total amount of the composition. ・"Added oil": The amount of antioxidant added is 0.08% by mass or more and less than 0.4% by mass on a basis of the total amount of the composition. When the electrical insulating oil composition according to one embodiment of the present invention is an additive-free oil, the content of mineral oil-based base oil is 100% by mass on a basis of the total amount (100% by mass) of the electrical insulating oil composition. When the electrical insulating oil composition according to one aspect of the present invention is an additive oil in a small amount, the content of mineral oil-based base oil may be 99.92% by mass or more and less than 100% by mass, or 99.92% by mass or more and 99.99% by mass or less, based on the total amount (100% by mass) of the electrical insulating oil composition. When the electrical insulating oil composition according to one aspect of the present invention is an additive oil, the content of mineral oil-based base oil may be 99.6% by mass or more and 99.92% by mass or less, based on the total amount (100% by mass) of the electrical insulating oil composition.

[0011] Antioxidants included in one embodiment of the present invention's electrical insulating oil composition include, for example, phenolic antioxidants (e.g., 2,6-di-tert-butyl-p-cresol), amine antioxidants, molybdenamine antioxidants, and sulfur-based antioxidants.

[0012] Furthermore, the electrical insulating oil composition according to one embodiment of the present invention may also contain other additives besides antioxidants, depending on the specifications of the electrical insulating oil. Examples of such other additives include metal deactivators, pour point depressants, and rust inhibitors and flowable antistatic agents (for example, benzotriazole compounds that serve as both rust inhibitors and flowable antistatic agents (e.g., Ilgamet 39 (manufactured by BASF))).

[0013] In one embodiment of the present invention, the total content of additives, including antioxidants, may be 5.0% by mass or less, 4.0% by mass or less, 3.0% by mass or less, 2.0% by mass or less, 1.0% by mass or less, 0.50% by mass or less, 0.40% by mass or less, 0.30% by mass or less, 0.20% by mass or less, 0.10% by mass or less, 0.08% by mass or less, 0.06% by mass or less, 0.04% by mass or less, 0.02% by mass or less, 0.01% by mass or less, 0.001% by mass or less, or 0.0001% by mass or less, based on the total amount (100% by mass) of the electrical insulating oil composition, or the electrical insulating oil composition may not contain any additives.

[0014] In an electrical insulating oil composition according to one aspect of the present invention, the content of synthetic oils other than mineral oil-based base oil may be 20.0% by mass or less, 15.0% by mass or less, 10.0% by mass or less, 8.0% by mass or less, 6.0% by mass or less, 4.0% by mass or less, 2.0% by mass or less, 1.0% by mass or less, 0.50% by mass or less, 0.10% by mass or less, 0.05% by mass or less, 0.01% by mass or less, 0.001% by mass or less, or 0.0001% by mass or less, based on the total amount (100% by mass) of the electrical insulating oil composition, or the electrical insulating oil composition may not contain synthetic oils other than mineral oil-based base oil.

[0015] An electrical insulating oil composition according to one aspect of the present invention satisfies the following requirements (1) to (3): Requirement (1): %C by ring analysis (n-d-M method) Ａ The content of sulfur atoms is 6.0% or less. Requirement (2): The sulfur atom content is 20 ppm by mass or more on a total basis of the electrical insulating oil composition. Requirement (3): The pour point is -50.0°C or lower. An electrical insulating oil composition according to one aspect of the present invention is adjusted to satisfy requirements (1) to (3), and can therefore be an electrical insulating oil composition that has high oxidation stability as defined in IEC 60296, as well as excellent low-temperature fluidity.

[0016] <Requirement (1)> Requirement (1) is the %C of the electrical insulating oil composition determined by ring analysis (n-d-M method). ＡThis defines the requirements. By satisfying requirement (1) together with requirement (2) above, an electrical insulating oil composition having high oxidation stability as defined in IEC 60296 can be obtained. From the above viewpoint, the %C defined in requirement (1) above Ａ The percentage is 6.0% or less, but it is preferably 5.7% or less, 5.5% or less, 5.2% or less, 5.0% or less, less than 5.0%, 4.7% or less, 4.5% or less, less than 4.5%, 4.2% or less, 4.0% or less, 3.7% or less, 3.5% or less, less than 3.5%, 3.4% or less, 3.3% or less, 3.2% or less, 3.1% or less, 3.0% or less, 2.9% or less, 2.8% or less, 2.7% or less, 2.6% or less, 2.5% or less, or 2.4% or less.

[0017] Furthermore, from the viewpoint of providing an electrical insulating oil composition with good low-temperature fluidity, the %C specified in requirement (1) above Ａ Preferably, the amount is 0.1% or more, 0.5% or more, 0.7% or more, 1.0% or more, 1.2% or more, 1.3% or more, 1.4% or more, 1.5% or more, 1.6% or more, 1.7% or more, 1.8% or more, 1.9% or more, 2.0% or more, 2.1% or more, 2.2% or more, or 2.3% or more, and may be 2.4% or more, 2.5% or more, 2.6% or more, 2.7% or more, 2.8% or more, 2.9% or more, or 3.0% or more.

[0018] In this specification, %C Ａ , as well as the weight-average molecular weight (Mw) and %C described below. Ｎ , and %C Ｐ This refers to the value measured by ring analysis (n-d-M method) in accordance with ASTM D3238:1995.

[0019] <Requirement (2)> Requirement (2) specifies the content of sulfur atoms in the electrical insulating oil composition. By satisfying requirement (2) together with requirement (1) above, an electrical insulating oil composition with high oxidation stability as specified in IEC 60296 can be obtained. From the above viewpoint, the sulfur atom content specified in requirement (2) is 20 ppm by mass or more based on the total amount (100% by mass) of the electrical insulating oil composition, but it is preferable that it is 22 ppm by mass or more, 24 ppm by mass or more, 26 ppm by mass or more, 28 ppm by mass or more, 30 ppm by mass or more, 32 ppm by mass or more, 34 ppm by mass or more, 36 ppm by mass or more, 38 ppm by mass or more, 40 ppm by mass or more, 45 ppm by mass or more, 50 ppm by mass or more, 55 ppm by mass or more, 60 ppm by mass or more, 65 ppm by mass or more, 70 ppm by mass or more, 75 ppm by mass or more, 80 ppm by mass or more, 85 ppm by mass or more, 90 ppm by mass or more, 95 ppm by mass or more, or 100 ppm by mass or more.

[0020] Furthermore, from the viewpoint of providing an electrical insulating oil composition with good corrosion resistance, the sulfur atom content specified in requirement (2) is based on the total amount (100% by mass) of the electrical insulating oil composition and is 500 ppm by mass or less, 450 ppm by mass or less, 400 ppm by mass or less, 350 ppm by mass or less, 300 ppm by mass or less, 280 ppm by mass or less, 260 ppm by mass or less, 240 ppm by mass or less, 220 ppm by mass or less, 200 ppm by mass or less, 190 ppm by mass or less, 180 ppm by mass or less, and 170 ppm by mass. Preferably, the amount is ppm or less, 160 ppm by mass or less, 150 ppm by mass or less, 140 ppm by mass or less, 130 ppm by mass or less, 120 ppm by mass or less, 110 ppm by mass or less, or 100 ppm by mass or less. Furthermore, it may be 90 ppm by mass or less, 80 ppm by mass or less, 70 ppm by mass or less, 65 ppm by mass or less, 60 ppm by mass or less, 55 ppm by mass or less, 50 ppm by mass or less, less than 50 ppm by mass, or 48 ppm by mass or less, or 45 ppm by mass or less.

[0021] In this specification, the sulfur atom content refers to the value measured in accordance with JIS K2541:2013.

[0022] <Requirement (3)> Requirement (3) specifies the pour point of the electrical insulating oil composition. By satisfying requirement (3), it is possible to make an electrical insulating oil composition that has excellent low-temperature fluidity and is not restricted in use even in cold regions, and is highly versatile. Note that IEC 60296 requires that the pour point be -40.0°C or lower. Therefore, an electrical insulating oil composition that satisfies requirement (3) meets the quality of electrical insulating oil specified in IEC 60296. Furthermore, as specified in requirement (3), electrical insulating oil compositions with a pour point of -50.0°C or lower generally tend to have reduced oxidation stability. However, an electrical insulating oil composition according to one embodiment of the present invention is adjusted to satisfy the above requirements (1) and (2), and therefore has high oxidation stability as specified in IEC 60296 even if the pour point is -50.0°C or lower.

[0023] From the viewpoint of providing a highly versatile electrical insulating oil composition that exhibits excellent low-temperature fluidity and can be used without restrictions even in cold regions, the pour point specified in requirement (3) is -50.0°C, but it is preferable that it be -52.5°C or lower, -55.0°C or lower, -57.5°C or lower, -60.0°C or lower, or less than -60.0°C. Furthermore, the pour point specified in requirement (3) may be -80.0°C or higher, -77.5°C or higher, -75.0°C or higher, -72.5°C or higher, or -70.0°C or higher.

[0024] In this specification, the pour point refers to the value measured in accordance with JIS K 2269:1987 (Test method for pour point and cloud point of crude oil and petroleum products).

[0025] <Other requirements related to ring analysis (n-d-M method)> The electrical insulating oil composition of one aspect of the present invention preferably further satisfies at least one of the following requirements (4) and (5), and more preferably satisfies both of the following requirements (4) and (5). ・Requirement (4): %C by ring analysis (n-d-M method) Ｎ and %C Ｐ Ratio to [%C] Ｎ / %C Ｐ ] is less than 1.0. • Requirement (5): %C by ring analysis (n-d-M method) ＮThe percentage is less than 50.0%. By satisfying requirement (4) and / or requirement (5), an electrical insulating oil composition with further improved oxidation stability as defined in IEC 60296 can be obtained.

[0026] From the viewpoint of providing an electrical insulating oil composition with even greater oxidation stability, the ratio [%C] specified in requirement (4) Ｎ / %C Ｐ [%C] is less than 1.0, but preferably 0.99 or less, 0.98 or less, 0.97 or less, 0.96 or less, 0.95 or less, 0.94 or less, 0.93 or less, 0.92 or less, 0.91 or less, 0.90 or less, 0.89 or less, 0.88 or less, 0.87 or less, 0.86 or less, or 0.85 or less. Furthermore, from the viewpoint of providing a highly versatile electrical insulating oil composition that has good low-temperature fluidity and whose use is not restricted even in cold regions, the ratio [%C] specified in requirement (4) is preferable. Ｎ / %C Ｐ It is preferable that ] is 0.10 or higher, 0.15 or higher, 0.20 or higher, 0.25 or higher, 0.30 or higher, 0.35 or higher, 0.40 or higher, 0.45 or higher, 0.50 or higher, 0.55 or higher, 0.60 or higher, 0.65 or higher, 0.70 or higher, 0.75 or higher, or 0.80 or higher.

[0027] From the viewpoint of providing an electrical insulating oil composition with even higher oxidation stability, the %C specified in requirement (5) Ｎ It is less than 50.0%, but preferably 49.5% or less, 49.0% or less, 48.5% or less, 48.0% or less, 47.8% or less, 47.6% or less, 47.4% or less, 47.2% or less, 47.0% or less, 46.8% or less, 46.6% or less, 46.4% or less, 46.2% or less, 46.0% or less, 45.8% or less, 45.6% or less, 45.4% or less, 45.2% or less, or 45.0% or less. Furthermore, from the viewpoint of providing a highly versatile electrical insulating oil composition that has good low-temperature fluidity and whose use is not restricted even in cold regions, the %C specified in requirement (5) is preferable. ＮPreferably, the amount is 25.0% or more, 30.0% or more, 32.0% or more, 34.0% or more, 36.0% or more, 38.0% or more, 40.0% or more, 41.0% or more, 42.0% or more, 43.0% or more, 44.0% or more, or 45.0% or more.

[0028] In one embodiment of the present invention, in order to obtain an electrical insulating oil composition with a superior balance of low-temperature fluidity and oxidation stability, %C is determined by ring analysis (n-d-M method). Ｐ It may also be 44.5% or more, 45.0% or more, 45.5% or more, 46.0% or more, 46.5% or more, 47.0% or more, 47.5% or more, 48.0% or more, 48.5% or more, 49.0% or more, 49.5% or more, 50.0% or more, greater than 50.0%, 50.5% or more, 51.0% or more, 51.5% or more, or 52.0% or more, and it may also be 75.0% by mass or less, 70.0% by mass or less, 65.0% by mass or less, 60.0% by mass or less, 58.0% by mass or less, 56.0% by mass or less, 55.0% by mass or less, 54.0% by mass or less, or 53.0% by mass or less.

[0029] In an electrical insulating oil composition according to one aspect of the present invention, the weight-average molecular weight (Mw) determined by ring analysis (n-d-M method) may be 100 or more, 120 or more, 140 or more, 160 or more, 180 or more, 200 or more, 210 or more, 220 or more, 230 or more, 240 or more, 250 or more, or 260 or more. Alternatively, it may be 1000 or less, 900 or less, 800 or less, 700 or less, 600 or less, 550 or less, 500 or less, 450 or less, 400 or less, 380 or less, 360 or less, 340 or less, 330 or less, 320 or less, 310 or less, 300 or less, 290 or less, or 280 or less.

[0030] An electrical insulating oil composition according to one aspect of the present invention is preferably further satisfied with the following requirement (6): Requirement (6): Sulfur atom content (unit: mass ppm) and %C determined by ring analysis (n-d-M method). Ａ (Unit: Ratio to %) [S / %C] Ａ The value is between 8.0 and 40.0. By satisfying requirement (6), an electrical insulating oil composition with further improved oxidation stability as defined in IEC 60296 can be obtained.

[0031] From the viewpoint of providing an electrical insulating oil composition with even greater oxidation stability, the ratio [S / %C] specified in requirement (6) Ａ It is preferable that the ] is 8.0 or higher, 8.5 or higher, 9.0 or higher, 9.5 or higher, 10.0 or higher, 10.5 or higher, 11.0 or higher, 11.5 or higher, 12.0 or higher, 12.5 or higher, 13.0 or higher, 13.5 or higher, or 14.0 or higher, and it is also preferable that it is 40.0 or lower, 38.0 or lower, 36.0 or lower, 35.0 or lower, 34.0 or lower, 33.0 or lower, 32.0 or lower, 31.0 or lower, 30.0 or lower, 29.0 or lower, 28.0 or lower, 27.0 or lower, 26.0 or lower, 25.0 or lower, 24.0 or lower, 23.0 or lower, 22.0 or lower, 21.0 or lower, or 20.0 or lower.

[0032] <Saybolt Color> The electrical insulating oil composition according to one embodiment of the present invention preferably further satisfies the following requirement (7): Requirement (7): The Saybolt color is +10 or higher. By satisfying requirement (7), an electrical insulating oil composition with excellent initial transparency can be obtained, and in the maintenance management of the electrical insulating oil composition, deterioration evaluation of the electrical insulating oil composition by visual observation becomes easier.

[0033] From the viewpoint of providing an electrical insulating oil composition with excellent initial transparency, the Saybolt color specified in requirement (7) is +10 or higher, but it is preferable that it be +12 or higher, +14 or higher, +16 or higher, +18 or higher, +20 or higher, +22 or higher, +24 or higher, +26 or higher, +28 or higher, or +30.

[0034] In this specification, Saybolt color refers to the value measured in accordance with JIS K2580:2003. Furthermore, the Saybolt color of an electrical insulating oil composition can be adjusted to a Saybolt color within the above range by, for example, treatment with activated carbon, alumina, silica gel, molecular sieve, white clay, etc.

[0035] <Properties of the Electrical Insulating Oil Composition> The kinematic viscosity of the electrical insulating oil composition according to one embodiment of the present invention at 40°C is 6.00 mm ２ / s or more, 6.20mm ２ / s or more, 6.40mm ２ / s or more, 6.60mm ２ / s or more, 6.80mm ２ / s or more, 7.00mm ２ / s or more, 7.20mm ２ / s or more, 7.40mm ２ / s or more, 7.60mm ２ / s or more, 7.80mm ２ / s or more, 8.00mm ２ / s or more, 8.10mm ２ / s or more, or 8.20 mm ２ It is preferable that the value be 14.0 mm or more. ２ / s or less, 13.0mm ２ / s or less, 12.0mm ２ / s or less, 11.5mm ２ / s or less, 11.0mm ２ / s or less, 10.5mm ２ / s or less, 10.0mm ２ / s or less, 9.80mm ２ / s or less, 9.60mm ２ / s or less, 9.40mm ２ / s or less, 9.20mm ２ / s or less, 9.00mm ２ / s or less, 8.90mm ２ / s or less, 8.80mm ２ / s or less, 8.70mm ２ / s or less, 8.60mm ２ / s or less, 8.50mm ２ / s or less, 8.40mm ２ / s or less, or 8.30 mm ２ It is preferable that the value be less than or equal to / s.

[0036] The kinematic viscosity at 100°C of an electrical insulating oil composition according to one aspect of the present invention is 1.00 mm. ２ / s or more, 1.20mm ２ / s or more, 1.40mm ２ / s or more, 1.50mm ２ / s or more, 1.60mm ２ / s or more, 1.70mm ２ / s or more, 1.80mm ２ / s or more, 1.90mm ２ / s or more, 2.00mm ２ / s or more, 2.10mm ２ / s or more, or 2.20 mm ２ / s or more is preferable, and 5.00 mm ２ / s or less, 4.50 mm ２ / s or less, 4.00 mm ２ / s or less, 3.50 mm ２ / s or less, 3.20 mm ２ / s or less, 3.00 mm ２ / s or less, 2.90 mm ２ / s or less, 2.80 mm ２ / s or less, 2.70 mm ２ / s or less, 2.60 mm ２ / s or less, 2.50 mm ２ / s or less, 2.40 mm ２ / s or less, or 2.30 mm ２ / s or less is preferable.

[0037] The viscosity index of the electrical insulating oil composition of one aspect of the present invention is preferably 30 or more, 35 or more, 40 or more, 45 or more, 50 or more, 55 or more, 57 or more, 60 or more, 62 or more, or 64 or more, and may also be 110 or less, 100 or less, less than 100, 95 or less, 90 or less, 85 or less, 80 or less, 75 or less, or 72 or less.

[0038] In this specification, the kinematic viscosity and the viscosity index mean values measured or calculated in accordance with JIS K2283:2000.

[0039] From the viewpoint of facilitating the production of an electrical insulating oil composition excellent in low-temperature fluidity, the density of the electrical insulating oil composition of one aspect of the present invention at 15 °C is 0.800 g / cm ３ or more, 0.810 g / cm ３ or more, 0.820 g / cm ３ or more, 0.830 g / cm ３ or more, 0.840 g / cm ３ or more, 0.845 g / cm ３ or more, 0.850 g / cm ３ or more, 0.855 g / cm ３ or more, or 0.860 g / cm ３ or more is preferable, and from the viewpoint of facilitating the production of an electrical insulating oil composition excellent in low-temperature fluidity and corrosion resistance, 0.900 g / cm３ Below, 0.895g / cm ３ Below, 0.890g / cm ３ Below, 0.885g / cm ３ Below, 0.880g / cm ３ Below, 0.875g / cm ３ The following, or 0.870 g / cm³ ３ The following is preferable. In this specification, the density at 15°C means the value measured in accordance with JIS K2249-1:2011 (Crude oil and petroleum products - Method for determining density - Part 1: Vibration method).

[0040] In one embodiment of the present invention, the acid value of the fresh oil in the electrical insulating oil composition is preferably 0.05 mg KOH / g or less, 0.04 mg KOH / g or less, 0.03 mg KOH / g or less, 0.02 mg KOH / g or less, or 0.01 mg KOH / g or less. In this specification, the acid value of the fresh oil refers to the value measured in accordance with the "indicator photometric titration method" in Annex 1 of JIS K2501:2003.

[0041] The aniline point of an electrical insulating oil composition according to one embodiment of the present invention is preferably 68.0°C or higher, 70.0°C or higher, 72.0°C or higher, 74.0°C or higher, 76.0°C or higher, 78.0°C or higher, 80.0°C or higher, 82.0°C or higher, 84.0°C or higher, or 86.0°C or higher, from the viewpoint of easily producing an electrical insulating oil composition with excellent corrosion resistance. Furthermore, from the viewpoint of easily producing an electrical insulating oil composition with excellent oxidation stability, it is preferably 100.0°C or lower, 98.0°C or lower, 96.0°C or lower, 94.0°C or lower, 92.0°C or lower, 90.0°C or lower, or 88.0°C or lower. In this specification, the aniline point refers to the value measured in accordance with JIS K2256:2013.

[0042] The flash point of an electrical insulating oil composition according to one embodiment of the present invention is preferably 130°C or higher, 135°C or higher, 136°C or higher, 137°C or higher, 138°C or higher, 139°C or higher, or 140°C or higher, from the viewpoint of ensuring the safety of the electrical insulating oil composition, and may also be 170°C or lower, 165°C or lower, 160°C or lower, 157°C or lower, or 155°C or lower. In this specification, the flash point refers to the value measured by the Pennsky-Hartens closed-circuit method (PM) in accordance with JIS K2265-3:2007.

[0043] In one embodiment of the present invention, the furfural content may be 0.10 ppm by mass or less, 0.05 ppm by mass or less, or less than 0.01 ppm by mass, based on the total amount (100% by mass) of the electrical insulating oil composition. In this specification, the furfural content refers to the value measured by the electrical insulating oil-furfural quantitative test method of the Japan Petroleum Institute standard JPI-5S-58-99.

[0044] In one embodiment of the present invention, the dielectric loss tangent at 90°C is preferably 0.010% or less, 0.009% or less, or 0.008% or less. In this specification, the dielectric loss tangent refers to the value measured in accordance with JIS C2101:2010.

[0045] [Mineral oil-based base oil constituting an electrical insulating oil composition according to one aspect of the present invention] From the viewpoint of preparing an electrical insulating oil composition that satisfies each of the above requirements (1) to (3), an electrical insulating oil composition according to one aspect of the present invention preferably contains a low-sulfur type mineral oil (α) with a sulfur atom content of 50 ppm by mass or less and a high-sulfur type mineral oil (β) with a sulfur atom content of more than 50 ppm by mass.

[0046] In an electrical insulating oil composition according to one aspect of the present invention, from the viewpoint of preparing an electrical insulating oil composition that satisfies each of the above requirements (1) to (3), and particularly from the viewpoint of preparing an electrical insulating oil composition having high oxidation stability as defined in IEC 60296, the content ratio of low-sulfur mineral oil (α) to high-sulfur mineral oil (β) [(α) / (β)] is, by mass ratio, greater than 30 / 70, 35 / 65 or more, 40 / 60 or more, and 45 / 55 or less. Preferably, the ratio is 50 / 50 or more, greater than 50 / 50, 55 / 45 or more, 60 / 40 or more, 65 / 35 or more, 67 / 33 or more, 70 / 30 or more, 72 / 28 or more, 75 / 25 or more, 77 / 23 or more, 80 / 20 or more, 82 / 18 or more, or 85 / 15 or more. It is also preferable that the ratio is less than 95 / 5, 94 / 6 or less, 93 / 7 or less, 92 / 8 or less, 91 / 9 or less, or 90 / 10 or less.

[0047] In an electrical insulating oil composition according to one aspect of the present invention, from the viewpoint of preparing an electrical insulating oil composition that satisfies each of the above requirements (1) to (3), and particularly from the viewpoint of preparing an electrical insulating oil composition having high oxidation stability as defined in IEC 60296, the content of low-sulfur mineral oil (α) is preferably more than 30% by mass, 35% by mass or more, 40% by mass or more, 45% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 72% by mass or more, 75% by mass or more, 77% by mass or more, 80% by mass or more, or 82% by mass or more, based on the total amount (100% by mass) of the electrical insulating oil composition, and is also preferably less than 95% by mass, 94% by mass or less, 93% by mass or less, 92% by mass or less, 91% by mass or less, or 90% by mass or less.

[0048] In an electrical insulating oil composition according to one aspect of the present invention, from the viewpoint of preparing an electrical insulating oil composition that satisfies each of the above requirements (1) to (3), and particularly from the viewpoint of preparing an electrical insulating oil composition having high oxidation stability as defined in IEC 60296, the content of high-sulfur mineral oil (β) is preferably more than 5% by mass, 6% by mass or more, 7% by mass or more, 8% by mass or more, 9% by mass or more, or 10% by mass or more, based on the total amount (100% by mass) of the electrical insulating oil composition, and also preferably less than 70% by mass, less than 65% by mass, 60% by mass or less, 55% by mass or less, 50% by mass or less, 45% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, 28% by mass or less, 25% by mass or less, 23% by mass or less, 20% by mass or less, or 18% by mass or less.

[0049] In an electrical insulating oil composition according to one aspect of the present invention, the total content of low-sulfur mineral oil (α) and high-sulfur mineral oil (β) [(α) + (β)] is preferably 80.0% by mass or more, 85.0% by mass or more, 90.0% by mass or more, 95.0% by mass or more, 96.0% by mass or more, 97.0% by mass or more, 98.0% by mass or more, 99.0% by mass or more, 99.2% by mass or more, 99.4% by mass or more, 99.6% by mass or more, 99.7% by mass or more, 99.8% by mass or more, 99.90% by mass or more, 99.92% by mass or more, greater than 99.92% by mass, or 100% by mass, based on the total amount (100% by mass) of the electrical insulating oil composition.

[0050] The following provides a detailed description of low-sulfur mineral oil (α) and high-sulfur mineral oil (β), including their preparation methods.

[0051] <Low-sulfur mineral oil (α)> In the low-sulfur mineral oil (α) used in one aspect of the present invention, the sulfur atom content is 50 ppm by mass or less based on the total amount (100% by mass) of the low-sulfur mineral oil (α), but it is preferable that it is 45 ppm by mass or less, 40 ppm by mass or less, 35 ppm by mass or less, 30 ppm by mass or less, 25 ppm by mass or less, 20 ppm by mass or less, 15 ppm by mass or less, 10 ppm by mass or less, 7 ppm by mass or less, 5 ppm by mass or less, or less than 5 ppm by mass.

[0052] The low-sulfur mineral oil (α) used in one aspect of the present invention can be prepared, for example, by performing one or more treatments selected from hydrocracking and hydroreforming on vacuum distillate oil obtained by vacuum distillation of atmospheric pressure distillation residue of crude oil such as paraffinic crude oil or intermediate crude oil, followed by hydroisomerization dewaxing treatment or solvent dewaxing treatment (preferably hydroisomerization dewaxing treatment).

[0053] In one aspect of the present invention, the low-sulfur mineral oil (α) used is preferably satisfied with one or more of the following requirements (α1) to (α4), more preferably two or more, even more preferably three or more, and even more preferably all of them, from the viewpoint of preparing an electrical insulating oil composition that satisfies each of the requirements including the above requirements (1) to (3). • Requirement (α1): The pour point is -40.0°C or lower. • Requirement (α2): %C calculated by ring analysis (n-d-M method). Ａ However, it is less than 4.5%. • Requirement (α3): %C by ring analysis (n-d-M method) Ｎ and %C Ｐ Ratio to [%C] Ｎ / %C Ｐ ] is less than 1.0. • Requirements (α4): Sulfur atom content (unit: mass ppm) and %C determined by ring analysis (n-d-M method). Ａ (Unit: Ratio to %) [S / %C] Ａ The value is 15.0 or less.

[0054] The pour point specified in requirement (α1) is -40.0°C or lower, but it is preferable that it be -42.5°C or lower, -45.0°C or lower, -47.5°C or lower, -50.0°C or lower, -52.5°C or lower, -55.0°C or lower, -57.5°C or lower, or -60.0°C or lower.

[0055] %C as defined in requirement (α2) ＡIt is less than 4.5%, but preferably 4.4% or less, 4.3% or less, 4.2% or less, 4.1% or less, 4.0% or less, 3.9% or less, 3.8% or less, 3.7% or less, 3.6% or less, 3.5% or less, 3.4% or less, 3.3% or less, 3.2% or less, 3.1% or less, 3.0% or less, 2.9% or less, 2.8% or less, 2.7% or less, 2.6% or less, 2.5% or less, 2.4% or less, 2.3% or less, 2.2% or less, 2.1% or less, or 2.0% or less. It may also be 0.1% or more, 0.5% or more, 0.7% or more, 1.0% or more, 1.2% or more, 1.3% or more, 1.4% or more, or 1.5% or more.

[0056] The ratio [%C] specified in requirement (α3) Ｎ / %C Ｐ ] is less than 1.0, but is preferably 0.98 or less, 0.96 or less, 0.94 or less, 0.92 or less, 0.90 or less, 0.88 or less, 0.86 or less, 0.84 or less, 0.82 or less, or 0.80 or less, and may also be 0.10 or more, 0.15 or more, 0.20 or more, 0.25 or more, 0.30 or more, 0.35 or more, 0.40 or more, 0.45 or more, 0.50 or more, 0.55 or more, 0.60 or more, 0.65 or more, or 0.70 or more.

[0057] The ratio [S / %C] specified in requirement (α4) Ａ The value of ] is 15.0 or less, but it is preferably 12.0 or less, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, 4.5 or less, 4.0 or less, 3.5 or less, 3.0 or less, or 2.5 or less.

[0058] In one aspect of the present invention, the low-sulfur mineral oil (α) used is preferably further having the following physical properties, from the viewpoint of making it easier to prepare an electrical insulating oil composition that satisfies each of the above requirements (1) to (3): • %C Ｎ It is preferable that the percentage is 25.0% or more, 30.0% or more, 35.0% or more, or 40.0% or more, and also preferable that it is less than 50.0%, 48.0% or less, 46.0% or less, or 44.0%. ＰPreferably, the content is 40.0% or more, 42.0% or more, 44.0% or more, 46.0% or more, 48.0% or more, 50.0% or more, or 52.0% or more, and also preferably 75.0% or less, 70.0% or less, 65.0% or less, 60.0% or less, or 55.0% or less. Weight-average molecular weight (Mw) is preferably 100 or more, 120 or more, 140 or more, 160 or more, 180 or more, 200 or more, 220 or more, 240 or more, 250 or more, or 260 or more, and also preferably 1000 or less, 900 or less, 800 or less, 700 or less, 600 or less, 500 or less, 400 or less, 380 or less, 360 or less, 340 or less, 320 or less, 300 or less, or 280 or less. Kinematic viscosity at 40°C: 6.00 mm ２ / s or more, 6.50mm ２ / s or more, 7.00mm ２ / s or more, 7.50mm ２ / s or more, or 8.00 mm ２ It is preferable that the value be 14.0 mm or more. ２ / s or less, 12.0mm ２ / s or less, 10.0mm ２ / s or less, 9.50mm ２ / s or less, 9.00mm ２ / s or less, or 8.50 mm ２ It is preferable that the value is less than or equal to / s. • Kinematic viscosity at 100°C: 1.00 mm ２ / s or more, 1.20mm ２ / s or more, 1.40mm ２ / s or more, 1.60mm ２ / s or more, 1.80mm ２ / s or more, 2.00mm ２ / s or more, or 2.10 mm ２ It is preferable that the value be 5.00 mm or more. ２ / s or less, 4.50mm ２ / s or less, 4.00mm ２ / s or less, 3.50mm ２ / s or less, 3.00mm ２ / s or less, 2.80mm ２ / s or less, 2.60mm ２ / s or less, or 2.40 mm ２It is preferable that the viscosity index is 30 or higher, 40 or higher, 50 or higher, 60 or higher, 65 or higher, or 70 or higher, and may also be 110 or lower, 100 or lower, less than 100, 95 or lower, 90 or lower, 85 or lower, or 80 or lower. Density (15℃) 0.800 g / cm³ ３ Above, 0.810g / cm ３ Above, 0.820g / cm ３ Above, 0.830g / cm ３ Above, 0.840g / cm ３ or more, or 0.850 g / cm³ ３ Preferably, it should be 0.900 g / cm³ or higher, and also 0.900 g / cm³. ３ Below, 0.890g / cm ３ Below, 0.870g / cm ３ The following, or 0.860 g / cm³ ３ The following is preferable: - Saybolt color: Preferably +10 or higher, +12 or higher, +14 or higher, +16 or higher, +18 or higher, +20 or higher, +22 or higher, +24 or higher, +26 or higher, +28 or higher, or +30. - Aniline point: Preferably 68.0°C or higher, 70.0°C or higher, 72.0°C or higher, 74.0°C or higher, 76.0°C or higher, 78.0°C or higher, 80.0°C or higher, 82.0°C or higher, 84.0°C or higher, or 86.0°C or higher, and preferably 100.0°C or lower, 98.0°C or lower, 96.0°C or lower, 94.0°C or lower, 92.0°C or lower, 90.0°C or lower, or 88.0°C or lower. - Flash point: Preferably 130°C or higher, 132°C or higher, 134°C or higher, 136°C or higher, or 138°C or higher, and may be 170°C or lower, 165°C or lower, 160°C or lower, 155°C or lower, or 150°C or lower. - Furfural content: May be 0.10 ppm by mass or less, 0.05 ppm by mass or less, or less than 0.01 ppm by mass.

[0059] In one aspect of the present invention, the low-sulfur mineral oil (α) used preferably contains ultra-low-sulfur mineral oil (αVL) with a sulfur atom content of 5 ppm by mass or less. In addition, the low-sulfur mineral oil (α) used in one aspect of the present invention may contain low-sulfur mineral oil (αL) with a sulfur atom content of more than 5 ppm by mass and 50 ppm by mass or less, together with the ultra-low-sulfur mineral oil (αVL), but the lower the content of low-sulfur mineral oil (αL), the better, and it is even better that it does not contain low-sulfur mineral oil (αL).

[0060] The content of ultra-low sulfur mineral oil (αVL) is preferably 30% by mass or more, 40% by mass or more, 50% by mass or more, 60% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, 95% by mass or more, or 100% by mass, based on the total amount (100% by mass) of low-sulfur mineral oil (α).

[0061] In an electrical insulating oil composition according to one aspect of the present invention, from the viewpoint of preparing an electrical insulating oil composition that satisfies each of the above requirements (1) to (3), and particularly from the viewpoint of preparing an electrical insulating oil composition having high oxidation stability as defined in IEC 60296, the content of ultra-low sulfur mineral oil (αVL) is preferably 30% by mass or more, 35% by mass or more, 40% by mass or more, 45% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 72% by mass or more, 75% by mass or more, 77% by mass or more, 80% by mass or more, or 82% by mass or more, based on the total amount (100% by mass) of the electrical insulating oil composition, and also preferably less than 95% by mass, 94% by mass or less, 93% by mass or less, 92% by mass or less, 91% by mass or less, or 90% by mass or less.

[0062] In an electrical insulating oil composition according to one aspect of the present invention, from the viewpoint of preparing an electrical insulating oil composition that satisfies each of the above requirements (1) to (3), and particularly from the viewpoint of preparing an electrical insulating oil composition having high oxidation stability as defined in IEC 60296, the content of low sulfur mineral oil (αL) is preferably less than 90% by mass, less than 80% by mass, less than 70% by mass, less than 60% by mass, less than 50% by mass, less than 40% by mass, less than 30% by mass, less than 20% by mass, less than 10% by mass, less than 5.0% by mass, less than 3.0% by mass, less than 2.0% by mass, less than 1.0% by mass, less than 0.1% by mass, less than 0.01% by mass, less than 0.001% by mass, or less than 0.0001% by mass, based on the total amount (100% by mass) of the electrical insulating oil composition.

[0063] (Ultra-low sulfur mineral oil (αVL)) The ultra-low sulfur mineral oil (αVL) used in one aspect of the present invention can be obtained, for example, by vacuum distilling the residual oil from atmospheric distillation of crude oil such as paraffinic crude oil or intermediate crude oil under reduced pressure, subjecting the vacuum distillate to one or more treatments selected from hydrocracking and hydroreforming, and then performing a hydroisomerization dewaxing treatment. The ultra-low sulfur mineral oil (αVL) may be used alone or in combination of two or more types.

[0064] Ultra-low sulfur mineral oil (αVL) undergoes one or more treatments selected from hydrocracking and hydroreforming, which highly remove impurities such as sulfur compounds (and even nitrogen compounds) derived from the vacuum distillate. Furthermore, ring-opening of naphthenes and hydrogenation and ring-opening of aromatics occur. Therefore, it has extremely low sulfur and aromatic content, but its sulfur content is supplemented when combined with high-sulfur mineral oil (β). In addition, the ultra-low sulfur mineral oil (αVL) undergoes hydroisomerization and dewaxing treatment, which isomerizes linear paraffins into branched isoparaffins. Therefore, it has a low pour point and can be easily prepared into an electrical insulating oil composition that satisfies requirement (3).

[0065] (Low-sulfur mineral oil (αL)) Low-sulfur mineral oil (αL) used in one aspect of the present invention can be obtained, for example, by vacuum distilling the residual oil from atmospheric distillation of crude oil such as paraffinic crude oil or intermediate crude oil under reduced pressure, subjecting the vacuum distillate to one or more treatments selected from hydrocracking and hydroreforming, and then performing a solvent dewaxing treatment.

[0066] In one embodiment of the present invention, the low-sulfur mineral oil (αL) is subjected to one or more treatments selected from hydrocracking and hydroreforming, followed by solvent dewaxing to precipitate and separate linear paraffins under low temperature conditions. The pour point of the low-sulfur mineral oil (αL) depends on the precipitation temperature of linear paraffins during the solvent dewaxing treatment; the lower the precipitation temperature, the lower the pour point.

[0067] <High-sulfur mineral oil (β)> In the high-sulfur mineral oil (β) used in one aspect of the present invention, the sulfur atom content is greater than 50 ppm by mass on a basis of the total amount (100% by mass) of the high-sulfur mineral oil (β), but from the viewpoint of providing a mineral oil that can lower the pour point of the electrical insulating oil composition and prepare an electrical insulating oil composition with excellent low-temperature fluidity, the content is 60 ppm or more by mass, 80 ppm or more by mass, 100 ppm or more by mass, 120 ppm or more by mass, 140 ppm or more by mass, 160 ppm or more by mass, 180 ppm or more by mass It is preferable that the amount is 200 ppm or more, 220 ppm or more, 240 ppm or more, 260 ppm or more, 280 ppm or more, 300 ppm or more, 320 ppm or more, or 340 ppm or more, and it is also preferable that it is less than 400 ppm, 390 ppm or less, 380 ppm or less, 370 ppm or less, 360 ppm or less, or 350 ppm or less.

[0068] In one aspect of the present invention, the high-sulfur mineral oil (β) may contain ultra-high-sulfur mineral oil (βVH) with a sulfur atom content of 400 ppm by mass or more. However, from the viewpoint of providing a mineral oil that can be prepared into an electrical insulating oil composition with excellent corrosion resistance, it is preferable that it does not contain ultra-high-sulfur mineral oil (βVH).

[0069] In an electrical insulating oil composition according to one aspect of the present invention, from the viewpoint of providing a mineral oil that can be prepared as an electrical insulating oil composition with excellent corrosion resistance, the content of ultra-high sulfur mineral oil (βVH) is preferably less than 50% by mass, less than 40% by mass, less than 30% by mass, less than 20% by mass, less than 10% by mass, less than 5.0% by mass, less than 3.0% by mass, less than 2.0% by mass, less than 1.0% by mass, less than 0.1% by mass, less than 0.01% by mass, less than 0.001% by mass, or less than 0.0001% by mass, based on the total amount (100% by mass) of the electrical insulating oil composition.

[0070] In an electrical insulating oil composition according to one aspect of the present invention, from the viewpoint of providing a mineral oil that can be prepared as an electrical insulating oil composition with excellent corrosion resistance, the high-sulfur type mineral oil (β1) having a sulfur atom content of more than 50 ppm by mass and less than 400 ppm by mass is preferably more than 5% by mass, 6% by mass or more, 7% by mass or more, 8% by mass or more, 9% by mass or more, or 10% by mass or more, based on the total amount (100% by mass) of the electrical insulating oil composition, and is also preferably less than 70% by mass, less than 65% by mass, 60% by mass or less, 55% by mass or less, 50% by mass or less, 45% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, 28% by mass or less, 25% by mass or less, 23% by mass or less, 20% by mass or less, or 18% by mass or less.

[0071] The high-sulfur mineral oil (β) used in one aspect of the present invention can be obtained, for example, by solvent extraction treatment of the distillate obtained by ambient vacuum distillation of naphthenic crude oil. In addition to solvent extraction treatment, conventionally known refining processes such as dewaxing, deflaking, hydrogenation, alkali treatment, and clay treatment may also be used in appropriate combination. The high-sulfur mineral oil (β) may be used alone or in combination of two or more types.

[0072] High-sulfur mineral oil (β) can be extracted using solvent extraction to remove excess aromatic compounds and sulfur compounds (and even nitrogen compounds) derived from the distillate, while leaving a moderate amount of sulfur compounds that can function as antioxidants. Therefore, an appropriate amount of sulfur remains, making it easier to adjust the sulfur content of the electrical insulating oil composition to a predetermined range.

[0073] Furthermore, the input ratio of furfural (S) to raffinate (R, raw material base oil) [(S) / (R)] during solvent extraction treatment may be 1.00 or more, 1.20 or more, 1.40 or more, 1.60 or more, or 1.80 or more by volume, from the viewpoint of making it easier to remove excess sulfur, etc., and may also be less than 2.50, 2.40 or less, 2.30 or less, or 2.20 or less, from the viewpoint of not removing too much sulfur and aromatic content.

[0074] In one aspect of the present invention, the high-sulfur mineral oil (β) used is preferably satisfied with one or more of the following requirements (β1) to (β4), more preferably two or more, even more preferably three or more, and even more preferably all of them, from the viewpoint of preparing an electrical insulating oil composition that satisfies each of the requirements including the above requirements (1) to (3). • Requirement (β1): The pour point is -40.0°C or lower. • Requirement (β2): %C by ring analysis (n-d-M method). Ａ However, it is 4.5% or more. • Requirements (β3): %C determined by ring analysis (n-d-M method) Ｎ and %C Ｐ Ratio to [%C] Ｎ / %C Ｐ The ratio is 1.0 or higher. • Requirements (β4): Sulfur atom content (unit: mass ppm) and %C determined by ring analysis (n-d-M method). Ａ (Unit: Ratio to %) [S / %C] Ａ The value is 15.0 or higher.

[0075] The pour point specified in requirement (β1) is -40.0°C or lower, but it is preferable that it be -42.5°C or lower, -45.0°C or lower, -47.5°C or lower, -50.0°C or lower, -52.5°C or lower, -55.0°C or lower, -57.5°C or lower, or -60.0°C or lower.

[0076] %C as defined in requirement (β2) Ａ The amount is 4.5% or more, but preferably 4.7% or more, 4.8% or more, 5.0% or more, 5.2% or more, 5.2% or more, or 5.4% or more, and preferably 10.0% or less, 9.0% or less, 8.0% or less, 7.0% or less, 6.8% or less, 6.6% or less, 6.4% or less, 6.2% or less, 6.0% or less, or 5.8% or less.

[0077] The ratio [%C] specified in requirement (β3) Ｎ / %C Ｐ ] is 1.0 or higher, but preferably 1.1 or higher, 1.2 or higher, 1.3 or higher, 1.4 or higher, 1.5 or higher, or 1.6 or higher, and preferably 3.0 or lower, 2.8 or lower, 2.6 or lower, 2.4 or lower, 2.2 or lower, 2.0 or lower, or 1.8 or lower.

[0078] The ratio [S / %C] specified in requirement (β4) Ａ ] is 15.0 or higher, but preferably 20.0 or higher, 25.0 or higher, 30.0 or higher, 35.0 or higher, 40.0 or higher, 45.0 or higher, 50.0 or higher, 55.0 or higher, or 60.0 or higher, and also preferably 80.0 or lower, 78.0 or lower, 76.0 or lower, 74.0 or lower, 72.0 or lower, 70.0 or lower, 68.0 or lower, 66.0 or lower, or 64.0 or lower.

[0079] The high-sulfur mineral oil (β) used in one aspect of the present invention preferably further has the following physical properties: • %C Ｎ It is preferable that the percentage is 30.0% or more, 35.0% or more, 40.0% or more, 45.0% or more, 50.0% or more, or 55.0% or more, and it is also preferable that it is less than 75.0%, 70.0% or less, 68.0% or less, 66.0% or less, 64.0% or less, 62.0% or less, or 60.0% or less. Ｐ Preferably, the content is 20.0% or more, 22.0% or more, 24.0% or more, 26.0% or more, 28.0% or more, 30.0% or more, or 32.0% or more, and also preferably 60.0% or less, 55.0% or less, 50.0% or less, 45.0% or less, or 40.0% or less. Weight-average molecular weight (Mw) Preferably, it is 100 or more, 120 or more, 140 or more, 160 or more, 180 or more, 200 or more, 220 or more, 240 or more, or 250 or more, and also preferably 1000 or less, 900 or less, 800 or less, 700 or less, 600 or less, 500 or less, 400 or less, 380 or less, 360 or less, 340 or less, 320 or less, 300 or less, or 280 or less. Kinematic viscosity at 40°C 6.00 mm ２ / s or more, 6.50mm ２ / s or more, 7.00mm ２ / s or more, 7.50mm ２ / s or more, 8.00mm ２ / s or more, or 8.50 mm ２ It is preferable that the value be 14.0 mm or more. ２ / s or less, 12.0mm ２ / s or less, 10.0mm ２ / s or less, 9.50mm ２ / s or less, or 9.00 mm ２ It is preferable that the value is less than or equal to / s. • Kinematic viscosity at 100°C: 1.00 mm ２ / s or more, 1.20mm ２ / s or more, 1.40mm ２ / s or more, 1.60mm ２ / s or more, 1.80mm ２ / s or more, 2.00mm ２ / s or more, or 2.10 mm ２ It is preferable that the value be 5.00 mm or more. ２ / s or less, 4.50mm ２ / s or less, 4.00mm ２ / s or less, 3.50mm ２ / s or less, 3.00mm ２ / s or less, 2.80mm ２ / s or less, 2.60mm ２ / s or less, or 2.40 mm ２ It is preferable that the viscosity index is 10 or higher, 15 or higher, 20 or higher, 25 or higher, or 30 or higher, and may also be less than 100, 90 or lower, 80 or lower, 70 or lower, 60 or lower, 50 or lower, or 40 or lower. Density (15℃) 0.800 g / cm³ ３ Above, 0.810g / cm ３ Above, 0.820g / cm ３ Above, 0.830g / cm ３ Above, 0.840g / cm ３ or more, or 0.850 g / cm³ ３ Preferably, the amount is 0.950 g / cm³ or more. ３ Below, 0.940g / cm ３ Below, 0.930g / cm ３ Below, 0.920g / cm３ Below, 0.910g / cm ３ The following, or 0.900 g / cm³ ３ The following is preferable: - Saybolt color: Preferably +10 or higher, +12 or higher, +14 or higher, +16 or higher, +18 or higher, +20 or higher, +22 or higher, or +24 or higher. - Aniline point: Preferably 50.0°C or higher, 52.0°C or higher, 54.0°C or higher, 56.0°C or higher, 58.0°C or higher, 60.0°C or higher, 62.0°C or higher, 64.0°C or higher, or 66.0°C or higher, and preferably 100.0°C or lower, 90.0°C or lower, 80.0°C or lower, 78.0°C or lower, 76.0°C or lower, 74.0°C or lower, or 72.0°C or lower. - Flash point: Preferably 130°C or higher, 132°C or higher, 134°C or higher, 136°C or higher, 138°C or higher, 140°C or higher, 142°C or higher, or 144°C or higher, and may be 170°C or lower, 165°C or lower, 160°C or lower, 155°C or lower, or 150°C or lower. - Furfural content: May be 0.10 ppm by mass or less, 0.05 ppm by mass or less, or less than 0.01 ppm by mass.

[0080] Furthermore, low-sulfur mineral oil (α) (including ultra-low-sulfur mineral oil (αVL) and low-sulfur mineral oil (αL)) and high-sulfur mineral oil (β) may be subjected to other treatments not mentioned above, such as treatment with activated carbon, alumina, silica gel, molecular sieves, or clay. These treatments may be applied to each of the low-sulfur mineral oil (α) (including ultra-low-sulfur mineral oil (αVL) and low-sulfur mineral oil (αL)) and high-sulfur mineral oil (β), or they may be applied after they are mixed.

[0081] [Characteristics of the Electrical Insulating Oil Composition] For an electrical insulating oil composition according to one embodiment of the present invention, the acid value after performing an oxidation stability test based on IEC 61125:2018 for 164 hours is preferably less than 1.00 mg KOH / g, 0.90 mg KOH / g or less, 0.80 mg KOH / g or less, 0.70 mg KOH / g or less, 0.60 mg KOH / g or less, 0.60 mg KOH / g or less, 0.50 mg KOH / g or less, 0.40 mg KOH / g or less, 0.30 mg KOH / g or less, 0.25 mg KOH / g or less, 0.20 mg KOH / g or less, or 0.15 mg KOH / g or less.

[0082] For an electrical insulating oil composition according to one embodiment of the present invention, the amount of sludge (the ratio of the mass of sludge to the total amount of the composition after the test) after an oxidation stability test based on IEC 61125:2018 has been performed for 164 hours is preferably 0.80% or less, 0.70% or less, 0.60% or less, 0.50% or less, 0.40% or less, 0.30% or less, 0.20% or less, 0.15% or less, 0.10% or less, 0.07% or less, or 0.05% or less.

[0083] For an electrical insulating oil composition according to one embodiment of the present invention, the dielectric loss tangent at 90°C after an oxidation stability test based on IEC 61125:2018 has been performed for 164 hours is preferably 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, 5.0% or less, 2.0% or less, 1.0% or less, or 0.80% or less.

[0084] In this specification, the acid value, sludge amount, and dielectric loss tangent at 90°C after 164 hours of oxidation stability testing according to IEC 61125:2018 refer to values ​​measured according to the methods described in the examples below.

[0085] [Uses of the Electrical Insulating Oil Composition] An electrical insulating oil composition according to one embodiment of the present invention exhibits excellent low-temperature fluidity and oxidation stability. Therefore, an electrical insulating oil composition according to one embodiment of the present invention can be used as an insulating material for oil-filled electrical equipment such as oil-filled capacitors, oil-filled cables, oil-filled transformers, and oil-filled circuit breakers. Furthermore, the following [1] and [2] are also provided as embodiments of the present invention. [1] A method of using an electrical insulating oil composition according to one embodiment of the present invention as an insulating material for oil-filled electrical equipment such as oil-filled capacitors, oil-filled cables, oil-filled transformers, and oil-filled circuit breakers. [2] An insulating material for oil-filled electrical equipment such as oil-filled capacitors, oil-filled cables, oil-filled transformers, and oil-filled circuit breakers, comprising an electrical insulating oil composition according to one embodiment of the present invention.

[0086] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited in any way by these examples. The measurement or calculation methods for various properties are as follows.

[0087] (1) Kinematic viscosity and viscosity index were measured and calculated in accordance with JIS K2283:2000. (2) Density (15°C) was measured in accordance with JIS K2249-1:2011 (Crude oil and petroleum products - Method for determining density - Part 1: Vibration method). (3) Sulfur atom content was measured in accordance with JIS K2541-2:2013 "Crude oil and petroleum products - Test method for sulfur content - Microcoulometric titration method". (4) Acid value was measured in accordance with Annex 1 of JIS K2501:2003 "Indicator photometric titration method". (5) Weight-average molecular weight (Mw), %C Ａ , %C Ｎ , and %C Ｐ (6) Saybolt color was calculated by ring analysis (n-d-M method) in accordance with ASTM D3238:1995. (7) Aniline point was measured in accordance with JIS K2256:2013. (8) Flash point was measured by Pennsky-Hartens closed-circuit method (PM) in accordance with JIS K2265-3:2007. (9) Pour point was measured in accordance with JIS K2269:1987 (Test methods for the pour point and cloud point of crude oil and petroleum products).

[0088] Production Example 1: Vacuum distillate obtained by vacuum distillation of the residual oil from atmospheric distillation of intermediate crude oil was subjected to hydromodulation treatment, followed by hydroisomerization dewaxing treatment to obtain ultra-low sulfur mineral oil (αVL-i).

[0089] Production Example 2: Low-sulfur mineral oil (αL-i) was obtained by vacuum distillation of the residual oil from atmospheric distillation of intermediate crude oil, followed by hydroreforming and then solvent dewaxing.

[0090] Production Example 3 Distillate oil obtained by vacuum distillation of naphthenic crude oil was subjected to solvent extraction and then alkali treatment. In the solvent extraction treatment, the ratio of furfural (S) to distillate oil (R) [(S) / (R)] was set to 2.0 by volume. After alkali treatment, adsorption treatment was performed to remove furfural to obtain high-sulfur mineral oil (β-i).

[0091] Table 1 shows the various properties of ultra-low sulfur mineral oil (αVL-i), low sulfur mineral oil (αL-i), and high sulfur mineral oil (β-i).

[0092] Examples 1-3 and Comparative Examples 1-2: Using the proportions shown in Table 2, ultra-low sulfur mineral oil (αVL-i), low sulfur mineral oil (αL-i), and high sulfur mineral oil (β-i) were mixed and treated with 1% by mass of white clay. No additives were added, and an additive-free electrical insulating oil composition according to IEC 60296 was prepared. The various properties described above were measured for the prepared electrical insulating oil composition, and the following oxidation stability tests were performed to evaluate its oxidation stability. These results are shown in Table 2.

[0093] <Oxidation Stability Test> An oxidation stability test was performed on the prepared electrical insulating oil composition for 164 hours according to IEC 61125:2018. After the test, the acid value, sludge amount, and dielectric loss tangent (at 90°C) of the electrical insulating oil composition were measured. The acid value of the electrical insulating oil composition after the test was measured in accordance with IEC 62021-1. A smaller acid value indicates an electrical insulating oil composition with superior oxidation stability. The sludge amount after the test was measured in accordance with JIS C2101:2010. A smaller sludge amount indicates an electrical insulating oil composition with superior oxidation stability. The dielectric loss tangent (at 90°C) of the electrical insulating oil composition after the test was measured in accordance with IEC 60247. A smaller dielectric loss tangent indicates an electrical insulating oil composition with superior oxidation stability and electrical properties.

[0094]

[0095] As shown in Table 2, the electrical insulating oil compositions prepared in Examples 1 to 3 had a pour point of -50.0°C or lower, exhibiting excellent low-temperature fluidity, and also showed excellent oxidation stability in oxidation stability tests based on IEC 61125:2018. On the other hand, the electrical insulating oil compositions prepared in Comparative Examples 1 and 2 showed insufficient oxidation stability in oxidation stability tests based on IEC 61125:2018.

Claims

1. An electrical insulating oil composition that satisfies the following requirements (1) to (3). • Requirement (1): %C determined by ring analysis (n-d-M method) Ａ The content is 5.5% or less. Requirement (2): The sulfur atom content is 20 ppm by mass or more on a total basis of the electrical insulating oil composition. Requirement (3): The pour point is -50.0°C or lower.

2. The electrical insulating oil composition according to claim 1, further satisfying the following requirement (4): Requirement (4): %C by ring analysis (n-d-M method) Ｎ and %C Ｐ Ratio to [%C] Ｎ / %C Ｐ The value is less than 1.

0.

3. The electrical insulating oil composition according to claim 1 or 2, further satisfying the following requirement (5): Requirement (5): %C by ring analysis (n-d-M method) Ｎ The percentage is less than 50.0%.

4. %C as defined in requirement (1) Ａ An electrical insulating oil composition according to any one of claims 1 to 3, wherein the amount is less than 3.5%.

5. The electrical insulating oil composition according to any one of claims 1 to 4, further satisfying the following requirement (6). - Requirement (6): The ratio [S / %C Ａ (unit: %) of the sulfur atom content (unit: mass ppm) to %C by ring analysis (n-d-M method) Ａ is 8.0 to 40.

0.

6. An electrical insulating oil composition according to any one of claims 1 to 5, further satisfying the following requirement (7): - Requirement (7): The Saybolt color is +10 or higher.

7. An electrical insulating oil composition according to any one of claims 1 to 6, comprising a low-sulfur mineral oil (α) having a sulfur atom content of 50 ppm by mass or less, and a high-sulfur mineral oil (β) having a sulfur atom content of more than 50 ppm by mass.

8. The electrical insulating oil composition according to claim 7, wherein the low-sulfur mineral oil (α) satisfies the following requirement (α1): Requirement (α1): The pour point is -40.0°C or lower.

9. The electrical insulating oil composition according to claim 7 or 8, wherein the low-sulfur mineral oil (α) satisfies the following requirement (α2): Requirement (α2): %C by ring analysis (n-d-M method) Ａ The percentage is less than 4.5%.

10. An electrical insulating oil composition according to any one of claims 7 to 9, wherein the low-sulfur mineral oil (α) satisfies the following requirement (α3): Requirement (α3): %C by ring analysis (n-d-M method) Ｎ and %C Ｐ Ratio to [%C] Ｎ / %C Ｐ The value of ] is less than 1.

0.

11. An electrical insulating oil composition according to any one of claims 7 to 10, wherein the high-sulfur mineral oil (β) satisfies the following requirement (β1): Requirement (β1): The pour point is -40.0°C or lower.

12. An electrical insulating oil composition according to any one of claims 7 to 11, wherein the high-sulfur mineral oil (β) satisfies the following requirement (β2): Requirement (β2): %C by ring analysis (n-d-M method) Ａ The percentage is 4.5% or higher.

13. An electrical insulating oil composition according to any one of claims 7 to 12, wherein the high-sulfur mineral oil (β) satisfies the following requirement (β3): Requirement (β3): %C by ring analysis (n-d-M method) Ｎ and %C Ｐ Ratio to [%C] Ｎ / %C Ｐ The value of ] is 1.0 or greater.

14. An electrical insulating oil composition according to any one of claims 7 to 13, wherein the content ratio of low-sulfur mineral oil (α) to high-sulfur mineral oil (β) [(α) / (β)] is 40 / 60 or more and less than 95 / 5 by mass.

15. The electrical insulating oil composition according to any one of claims 7 to 14, wherein the content of high-sulfur mineral oil (β) is 7 to 25% by mass on a total basis of the electrical insulating oil composition.

16. An electrical insulating oil composition according to any one of claims 1 to 15, wherein the acid value after a 164-hour oxidation stability test based on IEC 61125:2018 is less than 1.00 mg KOH / g.

17. A method for using an electrical insulating oil composition, wherein the electrical insulating oil composition described in any one of claims 1 to 16 is used as an insulating material for an oil-filled electrical device.

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