JP2021163659A - Electrical insulating oil composition - Google Patents

Abstract

To provide an electrical insulating oil composition which has a pour point of -40°C or less, excellent oxidation stability and initial transparency and has non-corrosiveness.SOLUTION: There is provided an electrical insulating oil composition which satisfies the following requirements (1) to (5). Requirement (1): the pour point is -40°C or less, Requirement (2): the Saybolt color is +10 or more, Requirement (3): the sulfur content is 50 mass ppm to 255 mass ppm based on the total amount of the electrical insulating oil composition, Requirement (4): %CN determined by ring analysis (n-d-M method) is 50.5 or less, Requirement (5): in the corrosive sulfur test (ASTM D1275 B method), the copper plate corrosion test rating measured according to JIS K 2513:2000 is 1a to 3b, provided that when the copper plate corrosion test rating is 1a to 2a, %CN determined by ring analysis (n-d-M method) is 46.5 or less.SELECTED DRAWING: None

Description

The present invention relates to an electrically insulating oil composition.

The electrically insulating oil composition is 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. For example, Patent Document 1 proposes an electrically insulating oil composition having better electrical insulating properties, based on the fact that the electrically insulating oil composition is used as an insulating material (see, for example, Patent Document 1 and the like).

Japanese Unexamined Patent Publication No. 2014-196391

In recent years, from the viewpoint of providing a highly versatile electric insulating oil composition whose use is not restricted even in cold regions, the electric insulating oil composition may have a pour point of −40 ° C. or lower. It is requested.

In addition, the electrically insulating oil composition is often used for a long period of 10 years or more. Therefore, the electrically insulating oil composition is required to have excellent oxidative stability.

Further, in order to prevent the occurrence of troubles in oil-filled electrical equipment, thorough maintenance management is required for the electrically insulating oil composition. In the maintenance management of the electric insulating oil composition, it is one of the effective methods to judge the deterioration of the electric insulating oil composition based on the appearance, particularly the hue of the electric insulating oil composition. Generally, the hue of an electrically insulating oil composition becomes brown as the deterioration progresses. Therefore, the electrically insulating oil composition is also required to have performance close to colorless and transparent (hereinafter, also referred to as "initial transparency") in an unused state and an initial state of use so that the degree of deterioration can be easily determined.

In addition, the electrically insulating oil composition is also required to have the ability to not corrode metals (for example, copper and the like) used in oil-filled electrical equipment. Hereinafter, the performance is also referred to as "non-corrosive".

However, as a result of diligent studies by the present inventor, it has been found that it is difficult to prepare an electrically insulating oil composition that satisfies all of the above requirements.

The present invention has been made under such circumstances, and provides an electrically insulating oil composition having a pour point of −40 ° C. or lower, excellent oxidative stability and initial transparency, and non-corrosive. That is the issue.

As a result of diligent studies, the present inventor has found that an electrically insulating oil composition satisfying a specific requirement can solve the above-mentioned problems, and has completed the present invention.
That is, the present invention relates to the following [1] to [6].
[1] An electrically insulating oil composition that satisfies the following requirements (1) to (5).
-Requirement (1): The pour point is -40 ° C or less.
-Requirement (2): The Seibolt color is +10 or more.
-Requirement (3): The sulfur content is 50 mass ppm to 255 mass ppm based on the total amount of the electrically insulating oil composition.
- Requirement (4): ring analysis (n-d-M method) According% _{C N} is 50.5 or less.
-Requirement (5): In the corrosive sulfur test (ASTM D1275 B method), the copper plate corrosion test score measured in accordance with JIS K 2513: 2000 is 1a to 3b. However, when the copper plate corrosion test score is 1a~2a it is% by ring analysis (n-d-M method) _{C N} is 46.5 or less.
[2] The electrically insulating oil composition according to [1], which further satisfies the following requirements (α) and (β).
-Requirement (α): The acid value after performing the oxidation stability test under the following test conditions in accordance with JIS C2101: 2010 is 0.60 mgKOH / g or less.
-Requirement (β): The amount of sludge after the oxidation stability test is carried out under the following test conditions in accordance with JIS C2101: 2010 is 0.40% or less based on the total amount of the electrically insulating oil composition.
-Test conditions: 120 ° C., 75 hours [3] The electrically insulating oil composition according to [1] or [2], which contains a low-sulfur type mineral oil (A) and a high-sulfur type mineral oil (B).
[4] The low-sulfur mineral oil (A) further contains an ultra-low-sulfur mineral oil (A1) having a sulfur content of less than 3 parts by mass ppm.
The electrically insulating oil composition according to any one of [1] to [3], further comprising an ultra-high sulfur mineral oil (B1) having a sulfur content of 400 mass ppm or more.
[5] the high sulfur type mineral oil (B) further comprises a ring analysis (n-d-M method) According% C _A is 8.0 or more high sulfur mineral oil (B2), according to [4] Electrical insulating oil composition.
[6] A method of use in which the electrically insulating oil composition according to any one of [1] to [5] is used as an insulating material for oil-filled electrical equipment.

According to the present invention, it is possible to provide an electrically insulating oil composition having a pour point of −40 ° C. or lower, excellent oxidative stability and initial transparency, and non-corrosive.

In the present specification, the lower limit value and the upper limit value described stepwise for a preferable numerical range (for example, a range such as content) can be independently combined. For example, from the description of "preferably 10 to 90, more preferably 30 to 60", the "preferable lower limit value (10)" and the "more preferable upper limit value (60)" are combined to obtain "10 to 60". You can also do it.
Further, in the present specification, the numerical values of Examples are numerical values that can be used as an upper limit value or a lower limit value.
Further, in the present specification, the numerical range described as "AA to BB" shall mean "AA or more and BB or less" unless otherwise specified.

[Aspects of the electrically insulating oil composition of the present invention]
The electrically insulating oil composition of the present invention satisfies the following requirements (1) to (5).
-Requirement (1): The pour point is -40 ° C or less.
-Requirement (2): The Seibolt color is +10 or more.
-Requirement (3): The sulfur content is 50 mass ppm to 255 mass ppm based on the total amount of the electrically insulating oil composition.
- Requirement (4): ring analysis (n-d-M method) According% _{C N} is 50.5 or less.
-Requirement (5): The copper plate corrosion test score measured in accordance with JIS K 2513: 2000 is 1a to 3b. However, when the copper plate corrosion test score is 1a~2a it is% by ring analysis (n-d-M method) _{C N} is 46.5 or less.

In the present invention, as shown in the requirement (1), the pour point is as low as −40 ° C. or lower, and as shown in the requirement (2), the seibolt color is +10 or more, and the initial transparency is excellent. Further, by satisfying the requirements (3) to (5), it is possible to provide an electrically insulating oil composition having excellent oxidative stability and being non-corrosive.
Hereinafter, the requirements (1) to (5) and other requirements will be described in detail, and then the conditions for preparing the electrically insulating oil composition for satisfying these requirements will be described in detail.

<Requirements (1) to (5)>
The electrically insulating oil composition of the present invention satisfies all of the requirements (1) to (5) described below.

(Requirement (1))
Requirement (1) stipulates that the pour point of the electrically insulating oil composition is −40 ° C. or lower.
When the pour point of the electric insulating oil composition is −40 ° C. or lower, it is possible to obtain a highly versatile electric insulating oil composition whose use is not restricted even in cold regions and the like.
On the other hand, according to the study of the present inventor, when the pour point of the electrically insulating oil composition is −40 ° C. or lower, the electrically insulating oil composition satisfies all of oxidation stability, initial transparency, and non-corrosiveness. It turned out to be difficult to prepare. Under such circumstances, the present inventor has studied diligently, and by satisfying the requirements (2) to (5) described below, an electrically insulating oil composition that satisfies all of oxidation stability, initial transparency, and non-corrosiveness. We have found that it is possible to prepare things.

Here, the electric insulating oil composition according to one aspect of the present invention may have a pour point of −42 ° C. or lower, and may be −44 ° C. or lower, from the viewpoint of making the electrically insulating oil composition more excellent in versatility. It may be −46 ° C. or lower, −48 ° C. or lower, or −50 ° C. or lower. However, the electrically insulating oil composition according to one aspect of the present invention is preferably from the viewpoint of satisfying the requirements for use in the coldest region, from the viewpoint of satisfying all of oxidation stability, initial transparency, and non-corrosiveness. It is -80 ° C or higher.
In the present specification, the pour point of the electrically insulating oil composition means a value measured in accordance with JIS K 2269: 1987 (pour point of crude oil and petroleum products and pour point test method of petroleum products).

(Requirement (2))
Requirement (2) stipulates that the Saybolt color of the electrically insulating oil composition is +10 or more.
When the Seibolt color of the electric insulating oil composition is +10 or more, the electric insulating oil composition having excellent initial transparency can be obtained.
If the Seibolt color of the electric insulating oil composition is less than +10, the initial transparency is inferior, so that it is difficult to evaluate the deterioration of the electric insulating oil composition by observing the appearance in the maintenance management of the electric insulating oil composition.

Here, the electrically insulating oil composition according to one aspect of the present invention has a Seibolt color of preferably +12 or more, more preferably +15 or more, from the viewpoint of making the electrically insulating oil composition more excellent in initial transparency.
In this specification, the Saybolt color of the electrically insulating oil composition means a value measured in accordance with JIS K2580: 2003.

(Requirement (3))
Requirement (3) stipulates that the sulfur content of the electrically insulating oil composition is 50 mass ppm to 255 mass ppm based on the total amount of the electrically insulating oil composition.
If the sulfur content of the electric insulating oil composition is less than 50% by mass based on the total amount of the electric insulating oil composition, the electric insulating oil composition is inferior in oxidative stability. That is, in this case, it is presumed that the sulfur content for ensuring the oxidative stability is insufficient, resulting in an electrically insulating oil composition having inferior oxidative stability.
On the other hand, if the sulfur content of the electric insulating oil composition exceeds 255 mass ppm based on the total amount of the electric insulating oil composition, the non-corrosive electric insulating oil composition cannot be obtained. That is, in this case, since the sulfur content is excessively contained, it is presumed that the electrically insulating oil composition corrodes the metal such as copper.

Here, the electric insulating oil composition according to one aspect of the present invention contains the electric insulating oil composition having a sulfur content from the viewpoint of facilitating the preparation of the electric insulating oil composition which is more excellent in oxidative stability and non-corrosive. Based on the total amount of the substance, it is preferably 52 mass ppm to 240 mass ppm, more preferably 54 mass ppm to 230 mass ppm, and further preferably 56 mass ppm to 220 mass ppm.
The sulfur content of the electrically insulating oil composition conforms to JIS K 2541: 2013, and depending on the sulfur content, a trace amount titration type oxidation method, a combustion tube type air method, a radiation type excitation method, a bomb type mass method, It means a value measured by selecting from an ultraviolet fluorescence method and a wavelength-dispersed fluorescent X-ray method.

(Requirement (4))
Requirement (4),% by ring analysis of the electrical insulating oil composition (n-d-M method) _{C N} is defines that this is 50.5 or less.
If the% C _N value of the electrical insulating oil composition exceeds 50.5, the electrical insulating oil composition poor in oxidation stability. That is, in this case, it is presumed that a large amount of naphthenic acid, which is a factor of oxidative deterioration, is present in the electric insulating oil composition, resulting in an electric insulating oil composition having poor oxidative stability.

Here, the electrical insulating oil composition of an embodiment of the present invention, from the viewpoint of easily preparing an electrical insulating oil composition having excellent by oxidation stability,% by ring analysis (n-d-M method) C _N is, It is preferably 50.0 or less, more preferably 49.0 or less, still more preferably 48.0 or less, still more preferably 47.0 or less. Further, from the viewpoint of facilitating the effect of the present invention, it is preferably 41.0 or more, more preferably 42.0 or more, still more preferably 42.5 or more.
In this specification, the ring analysis (nd-M method) is carried out in accordance with ASTM D 3238-95.

(Requirement (5))
In requirement (5), for the electrically insulating oil composition, the copper plate corrosion test scores measured in accordance with JIS K 2513: 2000 are 1a to 3b (1a, 1b, 2a, 2b, 2c, 2d, 2e, 3a, It stipulates that it is 3b). However, when the copper plate corrosion test score is 1a~2a (1a, 1b, 2a) is% by ring analysis (n-d-M method) _{C N} is 46.5 or less.
If the copper plate corrosion score is 4a to 4b (4a, 4b), the non-corrosive electrically insulating oil composition cannot be obtained.
Further, it is presumed that the electrically insulating oil composition having a copper plate corrosion test score of 1a to 2a has a small content of sulfur compounds that can contribute to the improvement of oxidative stability. In the sulfur compound is less electrical insulating oil composition which can contribute to improvement of oxidation stability, amount of naphthenic content, easily affect the oxidative stability of the electrical insulating oil composition,% C _N is 46.5 If it exceeds, an electrically insulating oil composition having poor oxidative stability will be obtained.

Here, the electrically insulating oil composition according to one aspect of the present invention is subjected to ring analysis (n) when the copper plate corrosion test score is 1b from the viewpoint of facilitating the preparation of an electrically insulating oil composition having better oxidative stability. -d-M method) According% _{C N} is preferably 46.0 or less, more preferably 45.0 or less, more preferably 44.0 or less, more further preferably 43.5 or less. Further, from the viewpoint of facilitating the effect of the present invention, it is preferably 41.5 or more, more preferably 42.0 or more, still more preferably 42.5 or more.

<Requirements (α) and (β)>
The electrically insulating oil composition of the present invention satisfies the requirements (1) to (5), has a pour point of −40 ° C. or lower, is excellent in oxidative stability and initial transparency, and is non-corrosive. It becomes an insulating oil composition.
Here, it is preferable that the electrically insulating oil composition of one aspect of the present invention satisfies a specific index with respect to oxidative stability. Specifically, it is preferable to satisfy the following requirements (α) and (β).

(Requirement (α))
The electrically insulating oil composition according to one aspect of the present invention conforms to JIS C2101: 2010 and has an acid value of preferably 0.60 mgKOH / g or less after performing an oxidation stability test under the following test conditions. The test conditions are 120 ° C. and 75 hours.
The requirement (α) is one of the indexes of the oxidative stability of the electrically insulating oil composition, and the lower the acid value shown in the requirement (α), the better the oxidative stability.
Here, from the viewpoint of making the electrically insulating oil composition of one aspect of the present invention an electrically insulating oil composition having more excellent oxidation stability, the above acid value is more preferably 0.50 mgKOH / g or less, still more preferably 0.50 mgKOH / g or less. It is 0.40 mgKOH / g or less, more preferably 0.30 mgKOH / g or less, and even more preferably 0.20 mgKOH / g or less.
The acid value means a value measured in accordance with JIS K 2501-5: 2003, JIS K 2501-6: 2003, or JIS K 2501-7: 2003.

(Requirement (β))
The amount of sludge in the electrically insulating oil composition according to one aspect of the present invention is preferably 0.40% or less based on the total amount of the electrically insulating oil composition.
That is, the requirement (β) is also one of the indexes of the oxidative stability of the electrically insulating oil composition like the requirement (α), and the smaller the sludge amount shown in the requirement (β), the better the oxidative stability. It is shown that.
Here, from the viewpoint that the electrically insulating oil composition according to one aspect of the present invention is an electrically insulating oil composition having better oxidation stability, the above sludge amount is more preferable based on the total amount of the electrically insulating oil composition. Is 0.30% or less, more preferably 0.20% or less, still more preferably 0.10% or less.
In this specification, the sludge amount means a value measured in accordance with JIS C2101: 2010.

<Preferable requirements other than the above requirements (1) to (5)>
The electrically insulating oil composition according to one aspect of the present invention preferably satisfies the requirements described below from the viewpoint of making it easier to exert the effects of the present invention.

(Requirement _{(6):% C} A)
Electrical insulating oil composition of an embodiment of the present invention, ring analysis (n-d-M method) According% _{C A} is preferably 5.0 to 9.4, more preferably 5.2 to 9.2, More preferably, it is 5.3 to 9.1.

(Requirement (7):% _CP )
Electrical insulating oil composition of an embodiment of the present invention, ring analysis (n-d-M method) According% _{C P} is preferably 40.0 to 53.0, more preferably 41.0 to 52.5, More preferably, it is 41.5 to 52.0.

(Requirement (8): Dissipation factor)
The electrically insulating oil composition according to one aspect of the present invention has a dielectric loss tangent of preferably 0.01 or less, more preferably 0.009 or less, still more preferably 0.008 or less.
In the present specification, the dielectric loss tangent of the electrically insulating oil composition means a value measured in accordance with JIS C2101: 2010.

(Requirement (9): 40 ° C kinematic viscosity)
Electrical insulating oil composition of an embodiment of the present invention, is 40 ° C. kinematic viscosity, preferably 8.00mm ² /s~13.00mm ² / s, more preferably 8.10mm ² /s~11.00mm ² / s, more preferably 8.20mm ² /s~9.00mm ² / s, even more preferably 8.30mm ² /s~8.95mm ² / s, is even more preferably 8.40mm ² / s~8. It is 90 mm ² / s.
In this specification, the kinematic viscosity at 40 ° C. of the electrically insulating oil composition means a value measured in accordance with JIS K2283: 2000.

(Requirement (10): 100 ° C. kinematic viscosity)
Electrical insulating oil composition of an embodiment of the present invention, 100 ° C. kinematic viscosity is preferably 2.00mm ² /s~4.00mm ² / s, more preferably 2.05mm ² /s~3.00mm ² / s, more preferably 2.10mm ² /s~2.45mm ² / s, even more preferably 2.15mm ² /s~2.40mm ² / s, is even more preferably 2.20mm ² / s~2. It is 35 mm ² / s.
In this specification, the kinematic viscosity at 100 ° C. of the electrically insulating oil composition means a value measured in accordance with JIS K2283: 2000.

(Requirement (11): Viscosity index)
The electrically insulating oil composition according to one aspect of the present invention has a viscosity index of preferably 45 to 67, more preferably 47 to 67, and even more preferably 49 to 66.
In this specification, the viscosity index of the electrically insulating oil composition means a value calculated from the measured values of 40 ° C. kinematic viscosity and 100 ° C. kinematic viscosity in accordance with JIS K2283: 2000.

(Requirement (12): Density)
The electrical insulating oil composition according to one aspect of the present invention has a density (15 ° C.) of preferably 0.860 to 0.900, more preferably 0.865 to 0.895, and even more preferably 0.870 to 0. It is 892.
In this specification, the density (15 ° C.) of the electrically insulating oil composition is measured in accordance with JIS K 2249-1: 2011 (crude oil and petroleum products-how to determine the density-Part 1: vibration method). Means the value that was set.

(Requirement (13): Refractive index)
The electrically insulating oil composition according to one aspect of the present invention has a refractive index (20 ° C.) of preferably 1.460 to 1.500, more preferably 1.465 to 1.495, and further preferably 1.470 to 1. .490.
In this specification, the refractive index (20 ° C.) of the electrically insulating oil composition means a value measured in accordance with JIS K 0062: 1992.

(Requirement (14): Aniline point)
The electrically insulating oil composition according to one aspect of the present invention has an aniline point of preferably 68.0 ° C to 83.0 ° C, more preferably 69.0 ° C to 82.0 ° C, and even more preferably 70.0 ° C to 70.0 ° C. It is 81.5 ° C.
In this specification, the aniline point of the electrically insulating oil composition means a value measured in accordance with JIS K 2256: 2013.

(Requirement (15): Flash point)
The electric insulating oil composition according to one aspect of the present invention has a flash point of preferably 140 ° C. to 153 ° C., more preferably 141 ° C. to 152 ° C., still more preferably 142 ° C. to 151 ° C. ..
In the present specification, the flash point of the electrically insulating oil composition by the Perschemal tense sealing method means a value measured in accordance with JIS K 2265-3: 2007.

(Requirement (16): Isoparaffin amount)
The electrically insulating oil composition according to one aspect of the present invention preferably contains an isoparaffin amount of a certain amount or more from the viewpoint of lowering the pour point and facilitating the satisfaction of the above requirement (1).
In the present specification, the amount of isoparaffin in the electrically insulating oil composition means a value quantified by analytical means such as mass spectrometry and nuclear magnetic resonance.

[Electrical insulating oil composition satisfying the above requirements and its preparation method]
The composition of the electrically insulating oil composition of one aspect of the present invention is not particularly limited as long as it satisfies the above requirements, but from the viewpoint of facilitating the preparation of an electrically insulating oil composition satisfying the above requirements, the electricity of one aspect of the present invention The insulating oil composition preferably contains a low sulfur type mineral oil (A) and a high sulfur type mineral oil (B).
Here, the low sulfur type mineral oil (A) is a mineral oil in which the sulfur content is reduced to 30 mass ppm or less (preferably 20 mass ppm or less, more preferably 15 mass ppm or less, still more preferably 10 mass ppm or less). Is preferable. The high sulfur type mineral oil (B) has a sulfur content of more than 30 mass ppm (preferably 50 mass ppm or more, more preferably 100 mass ppm or more, still more preferably 150 mass ppm or more, still more preferably 200 mass ppm or more) remaining. It is preferable that the mineral oil is used.
Furthermore, low-sulfur-type mineral oil (A), in addition to the sulfur content is reduced to below 30 wt ppm, ring analysis (n-d-M method) According% _{C N} 45.0 or less (preferably It is preferably a mineral oil having a value of 44.0 or less, more preferably 43.0 or less). High sulfur type mineral (B), in addition to sulfur is ultra remaining 30 mass ppm, ring analysis (n-d-M method) According% _{C N} 45.0 greater (preferably 48 or more, It is more preferably 50 or more, still more preferably 52 or more).
In the electrically insulating oil composition of one aspect of the present invention, the total content of the low sulfur type mineral oil (A) and the high sulfur type mineral oil (B) is preferably 90% by mass or more based on the total amount of the electrically insulating oil composition. It is 100% by mass, more preferably 95% by mass to 100% by mass, further preferably 98% by mass to 100% by mass, and even more preferably 99% by mass to 100% by mass.

Hereinafter, the low sulfur type mineral oil (A) and the high sulfur type mineral oil (B) contained in the electric insulating oil composition of one aspect of the present invention will be based on the method for preparing the electric insulating oil composition of one aspect of the present invention. I will explain in detail.

<Low sulfur type mineral oil (A)>
The electrically insulating oil composition of one aspect of the present invention contains a low sulfur type mineral oil (A).
When the electrically insulating oil composition contains only the high sulfur type mineral oil (B), the pour point is adjusted to -40 ° C or less in consideration of the physical characteristics of the high sulfur type mineral oil (B) to meet the above requirement (1). It is relatively easy to meet. However, the Seibolt color is adjusted to +10 or more to satisfy the above requirement (2), the sulfur content is adjusted to 255 mass ppm or less to satisfy the above requirement (3), and the naphthenic content is adjusted to a certain value or less. It is difficult to satisfy the above requirements (4) and (5) in consideration of the physical properties of the high sulfur type mineral oil (B). In other words, when the electrically insulating oil composition contains only high sulfur type mineral oil (B), the pour point can be adjusted to −40 ° C. or lower, but the oxidation stability and initial transparency are excellent. It is difficult to prepare an electrically insulating oil composition that is non-corrosive.
On the other hand, since the electrically insulating oil composition contains the low sulfur type mineral oil (A), it is easy to adjust so as to satisfy the above requirements (2) to (5), and also satisfy the above requirement (1). Can be adjusted.

Here, from the viewpoint of making it easier to adjust the pour point to a low temperature so as to satisfy the above requirement (1), the low sulfur type mineral oil (A) is an ultra-low sulfur mineral oil having a sulfur content of less than 3 parts by mass ppm ( It is preferable to include A1). Here, ultra low sulfur mineral oil (A1) is% by ring analysis (n-d-M method) _{C N} is preferably 45.0 or less, more preferably 44.0 or less, more preferably 43.0 or less Is.
In the electrically insulating oil composition of one aspect of the present invention, the content of the ultra-low sulfur mineral oil (A1) is preferably based on the total amount of the low-sulfur mineral oil (A) from the viewpoint of facilitating the above requirement (1). Is 40% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, still more preferably 70% by mass or more.

Here, the low-sulfur type base oil (A) is from the viewpoint of making it easier to adjust the hue, sulfur content, and naphthen content so as to satisfy the above requirements (2), (3), and (4). , It is preferable to contain other low-sulfur mineral oils other than the ultra-low-sulfur mineral oil (A1). Other low-sulfur mineral oils include, for example, low-sulfur mineral oils having a sulfur content of more than 3 mass ppm and 30 mass ppm or less (preferably more than 3 mass ppm and 20 mass ppm or less, more preferably more than 3 mass ppm and 10 mass ppm or less). A2) can be mentioned. Note that the low sulfur mineral oil (A2) is% by ring analysis (n-d-M method) _{C N} is preferably 45.0 or less, more preferably 44.0 or less, even more preferably at 43.0 or less ..
From the viewpoint of facilitating the above requirements (2), (3), and (4) in the electrically insulating oil composition of one aspect of the present invention, the content of the low sulfur mineral oil (A2) is a low sulfur mineral oil ( Based on the total amount of A), it is preferably more than 5% by mass, more preferably 10% by mass or more, still more preferably 15% by mass or more, still more preferably 20% by mass or more.

The total content of the ultra-low sulfur mineral oil (A1) and the low-sulfur mineral oil (A2) is preferably 90% by mass to 100% by mass, more preferably 95% by mass, based on the total amount of the low-sulfur type mineral oil (A). It is ~ 100% by mass, more preferably 98% by mass to 100% by mass, and even more preferably 99% by mass to 100% by mass.

Hereinafter, a method for preparing ultra-low sulfur mineral oil (A1) and low-sulfur mineral oil (A2) will be described.

(Ultra low sulfur mineral oil (A1))
The ultra-low sulfur mineral oil (A1) is obtained by hydrocracking and hydromodification with respect to the vacuum distillate obtained by distilling the atmospheric distillation residual oil of crude oil such as paraffin crude oil or intermediate base crude oil under reduced pressure. It is obtained by performing one or more kinds of treatments selected from treatments and the like, and then performing hydrogenation isomerization dewaxing.
The ultra-low sulfur mineral oil (A1) may be used alone or in combination of two or more.

The ultra-low sulfur mineral oil (A1) has impurities such as sulfur compounds (further nitrogen compounds) derived from the vacuum distillate oil by one or more treatments selected from hydrogenation decomposition treatment, hydrogenation reforming treatment, and the like. Is highly removed. In addition, ring-opening of naphthenic acid progresses. Therefore, the sulfur content is extremely low, and the sulfur content of the electrically insulating oil composition can be easily adjusted to a predetermined range so as to satisfy the requirement (3). Further, the naphthenic content of the electrically insulating oil composition can be adjusted to a predetermined range so as to satisfy the requirement (4), and the oxidative stability (further insulating characteristics) can be easily improved.
Then, in the ultra-low sulfur mineral oil (A1), the linear paraffin is isomerized into branched-chain isoparaffin by the hydrogenation isomerization dewax treatment. Therefore, the pour point is low, and the pour point of the electrically insulating oil composition can be easily adjusted to a low temperature so as to satisfy the requirement (1).

Here, the ultra-low sulfur mineral oil (A1) preferably has the following physical property values.
-Pour point is preferably −50 ° C. or lower.
·% _{C A}
It is preferably 3.4 to 6.4, more preferably 3.9 to 5.9, and even more preferably 4.4 to 5.4.
・% C _p
It is preferably 51.7 to 54.7, more preferably 52.3 to 54.2, and even more preferably 52.8 to 53.7.
· 40 ° C. kinematic viscosity preferably 8.10mm ² /s~9.10mm ² / s, more preferably 8.20mm ² /s~9.00mm ² / s, more preferably 8.30mm ² / s~8. It is 90 mm ² / s.
· 100 ° C. kinematic viscosity preferably 2.10mm ² /s~2.60mm ² / s, more preferably 2.15mm ² /s~2.55mm ² / s, more preferably from 2.20mm ² / s~2. It is 50 mm ² / s.
The viscosity index is preferably 60 to 80, more preferably 65 to 75, and even more preferably 67 to 73.
The density is preferably 0.8610 to 0.8710, more preferably 0.8630 to 0.8690, and even more preferably 0.8640 to 0.8680.
The refractive index is preferably 1.4700 to 1.4800, more preferably 1.4720 to 1.4780, and even more preferably 1.4730 to 1.4770.
-Aniline point is preferably 75.0 ° C to 95.0 ° C, more preferably 80.0 ° C to 90.0 ° C, still more preferably 82.0 ° C to 88.0 ° C.
The flash point is preferably 130 ° C. to 160 ° C., more preferably 135 ° C. to 155 ° C., and even more preferably 140 ° C. to 150 ° C.

(Low sulfur mineral oil (A2))
The low sulfur mineral oil (A2) is a hydrocracking treatment and a hydrogenation reforming treatment of a vacuum distillate obtained by distilling the atmospheric distillation residual oil of crude oil such as paraffin crude oil or intermediate base crude oil under reduced pressure. It is obtained by performing one or more treatments selected from the above, and then performing solvent dewaxing.

The low sulfur mineral oil (A2) is separated by precipitating linear paraffin in a low temperature environment by solvent dewaxing treatment after one or more treatments selected from hydrocracking treatment and hydrogenation reforming treatment. It is being removed. The pour point of low sulfur mineral oil (A2) depends on the precipitation temperature of linear paraffin during solvent dewaxing treatment, and the lower the precipitation temperature is set, the lower the pour point, but the higher the treatment cost. do. In one aspect of the present invention, even if the pour point of the low-sulfur mineral oil (A2) is about −25 ° C., it is electrically insulated by the combination with the ultra-low sulfur mineral oil (A1) and the high-sulfur type mineral oil (B). The pour point of the oil composition can be adjusted below −40 ° C. Therefore, by setting the pour point of the low-sulfur mineral oil (A2) to about -25 ° C to reduce the production cost of the low-sulfur mineral oil (A2), the cost of the low-sulfur mineral oil (A) is reduced as a whole. can do.

Further, the low-sulfur mineral oil (A2) is not as strict in refining conditions as the ultra-low-sulfur mineral oil (A1). Therefore, the hue indicated by the seibolt color is better than that of the ultra-low sulfur mineral oil (A1), and the seibolt color of the electrically insulating oil composition can be easily adjusted to a good range so as to satisfy the requirement (2).

Here, the low-sulfur mineral oil (A2) preferably has the following physical property values.
-Pour point is preferably −30 ° C. to −20 ° C.
-Seybolt color is preferably +15 or more, more preferably +20 or more.
·% _{C A}
It is preferably 6.0 to 9.0, more preferably 6.5 to 8.5, and even more preferably 7.0 to 8.0.
・% C _p
It is preferably 50.6 to 53.6, more preferably 51.1 to 53.1, and even more preferably 51.6 to 52.6.
· 40 ° C. kinematic viscosity preferably 7.90mm ² /s~8.90mm ² / s, more preferably 8.00mm ² /s~8.80mm ² / s, more preferably 8.10mm ² / s~8. It is 70 mm ² / s.
· 100 ° C. kinematic viscosity preferably 2.00mm ² /s~2.50mm ² / s, more preferably 2.05mm ² /s~2.45mm ² / s, more preferably from 2.10mm ² / s~2. It is 40 mm ² / s.
The viscosity index is preferably 60 to 80, more preferably 65 to 75, and even more preferably 67 to 73.
The density is preferably 0.8660 to 0.8760, more preferably 0.8680 to 0.8740, and even more preferably 0.8670 to 0.8730.
The refractive index is preferably 1.4740 to 1.4840, more preferably 1.4760 to 1.4820, and even more preferably 1.4770 to 1.4810.
The aniline point is preferably 68.0 ° C to 88.0 ° C, more preferably 73.0 ° C to 83.0 ° C, and even more preferably 75.0 ° C to 81.0 ° C.
The flash point is preferably 145 ° C to 175 ° C, more preferably 150 ° C to 170 ° C, and even more preferably 150 ° C to 165 ° C.

<High sulfur type mineral oil (B)>
The electrically insulating oil composition of one aspect of the present invention contains a high sulfur type mineral oil (B).
When the electrically insulating oil composition contains only the low sulfur type mineral oil (A), it is possible to adjust the pour point to −40 ° C. or lower to satisfy the above requirement (1). It is also possible to adjust the Seibolt color to +10 or more to satisfy the above requirement (2). It is also possible to adjust the naphthenic acid content to a certain value or less to satisfy the above requirements (4) and (5). However, it is difficult to adjust the sulfur content to 50 mass ppm or more to satisfy the above requirement (3).
On the other hand, since the electrically insulating oil composition contains the high sulfur type mineral oil (B), it is easy to adjust so as to satisfy the above requirements (1) to (5).

Here, from the viewpoint of making it easier to adjust so as to satisfy the above requirement (3), the high sulfur type mineral oil (B) contains an ultra-high sulfur mineral oil (B1) having a sulfur content of 400 mass ppm or more. Is preferable. Here, ultra-high sulfur mineral oil (B1) is% by ring analysis (n-d-M method) _{C N} is preferably 45.0, more preferably above 48 or more, more preferably 50 or more, more preferably more Is 52 or more.
In the electrically insulating oil composition of one aspect of the present invention, the content of the ultra-high sulfur mineral oil (B1) is preferably 20% by mass to 100% by mass, more preferably 20% by mass, based on the total amount of the high-sulfur mineral oil (B). It is 30% by mass to 100% by mass, more preferably 40% by mass to 100% by mass, and even more preferably 50% by mass to 100% by mass.

Further, the high-sulfur type mineral oil (B) may be composed of only the ultra-high sulfur mineral oil (B1), but may contain other high-sulfur mineral oils other than the ultra-high sulfur mineral oil (B1). Other high-sulfur mineral oils include, for example, high-sulfur mineral oils having a sulfur content of more than 30 mass ppm and less than 400 mass ppm (preferably 40 mass ppm or more and 300 mass ppm or less, more preferably 50 mass ppm or more and 250 mass ppm or less). B2) can be mentioned. The high sulfur mineral oil (B2) is ring analysis (n-d-M method) According% _{C N} is preferably 45.0, more preferably above 48 or more, more preferably 50 or more, even more preferably 52 That is all.
In the electrically insulating oil composition of one aspect of the present invention, when the high sulfur mineral oil (B) contains the high sulfur mineral oil (B2), the content of the high sulfur mineral oil (B2) is that of the high sulfur mineral oil (B). Based on the total amount, it may be 5% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more. It may be 50% by mass or more.

Hereinafter, a method for preparing ultra-high sulfur mineral oil (B1) and high-sulfur mineral oil (B2) will be described.

(Ultra-high sulfur mineral oil (B1))
The ultra-high sulfur mineral oil (B1) can be obtained, for example, by subjecting a distillate obtained by distilling a naphthenic-based crude oil under normal pressure to a solvent extraction treatment. Further, the ultra-high sulfur mineral oil (B1) may be produced by appropriately combining conventionally known refining processes such as dewaxing treatment, dewaxing treatment, hydrogenation finishing, and alkali treatment, in addition to the solvent extraction treatment.
The ultra-high sulfur mineral oil (B1) may be used alone or in combination of two or more.

The ultra-high sulfur mineral oil (B1) can function as an antioxidant while removing excess aromatic components and sulfur compounds (further nitrogen compounds) derived from the distillate oil by solvent extraction treatment. The compound can be reasonably retained. Therefore, an appropriate amount of sulfur remains, and the sulfur content of the electrically insulating oil composition can be easily adjusted within a predetermined range so as to satisfy the requirement (3).

Here, the ultra-high sulfur mineral oil (B1) preferably has the following physical property values.
-Pour point is preferably −50 ° C. or lower.
The Seibolt color is preferably −5 to +5, more preferably -2 to +4, and even more preferably 0 to +3.
·% _{C A}
It is preferably 9.2 to 12.2, more preferably 9.7 to 11.7, and even more preferably 10.2 to 11.2.
・% C _p
It is preferably 33.1 to 36.1, more preferably 33.6 to 35.6, and even more preferably 34.0 to 35.1.
· 40 ° C. kinematic viscosity preferably 8.60mm ² /s~9.60mm ² / s, more preferably 8.70mm ² /s~9.50mm ² / s, more preferably 8.80mm ² / s~9. It is 40 mm ² / s.
· 100 ° C. kinematic viscosity preferably 2.00mm ² /s~2.50mm ² / s, more preferably 2.05mm ² /s~2.45mm ² / s, more preferably from 2.10mm ² / s~2. It is 40 mm ² / s.
The viscosity index is preferably 15 to 35, more preferably 20 to 30, and even more preferably 22 to 28.
The density is preferably 0.9030 to 0.9130, more preferably 0.9050 to 0.9110, and even more preferably 0.9060 to 0.9100.
The refractive index is preferably 1.4890 to 1.4990, more preferably 1.49 to 1.4970, and even more preferably 1.492 to 1.4960.
-Aniline point is preferably 45.0 ° C to 75.0 ° C, more preferably 50.0 ° C to 70.0 ° C, still more preferably 55.0 ° C to 65.0 ° C.
The flash point is preferably 130 ° C. to 160 ° C., more preferably 135 ° C. to 155 ° C., and even more preferably 140 ° C. to 150 ° C.

(High sulfur mineral oil (B2))
Examples of the high-sulfur mineral oil (B2) include hydrorefined distillate obtained by distilling naphthenic-based crude oil under normal pressure.
As the high sulfur mineral oil (B2), one type may be used alone, or two or more types may be used in combination.

The high sulfur mineral oil (B2) was subjected to solvent extraction treatment for excess sulfur contained in the vacuum distillate obtained by distillation of the atmospheric distillation residual oil of the naphthenic crude oil under reduced pressure by hydrorefining treatment. More is removed compared to the case, especially more corrosive sulfur. Therefore, the corrosive sulfur content is small, and it is possible to easily suppress the corrosiveness while ensuring the oxidative stability required for the electrically insulating oil composition. Further, since the coloring substance contained in the vacuum distillate is removed, the hue of the electrically insulating oil can be easily adjusted within a predetermined range.
The high sulfur mineral oil (B2), from the viewpoint of easier to improve the non-corrosive and oxidative stability,% by ring analysis (n-d-M method) C _A is adjusted to 8.0 or higher Is preferable. % C _A of high sulfur mineral oil (B2) is more preferably 8.0 to 11.0, more preferably from 8.5 to 10.5. Even more preferably, it is 9.0 to 10.5.

Here, the high sulfur mineral oil (B2) preferably has the following physical property values.
-Pour point is preferably −50 ° C. or lower.
·% _{C A}
It is preferably 7.5 to 11.4, more preferably 8.0 to 10.9, and even more preferably 8.5 to 10.4.
・% C _p
It is preferably 31.2 to 44.3, more preferably 31.7 to 43.8, and even more preferably 32.2 to 43.3.
· 40 ° C. kinematic viscosity preferably 8.30mm ² /s~9.40mm ² / s, more preferably 8.40mm ² /s~9.30mm ² / s, more preferably 8.50mm ² / s~9. It is 20 mm ² / s.
· 100 ° C. kinematic viscosity preferably 2.00mm ² /s~2.50mm ² / s, more preferably 2.05mm ² /s~2.45mm ² / s, more preferably from 2.10mm ² / s~2. It is 40 mm ² / s.
The viscosity index is preferably 10 to 50, more preferably 15 to 45, and even more preferably 20 to 40.
The density is preferably 0.8840 to 0.9160, more preferably 0.8860 to 0.9140, and even more preferably 0.8870 to 0.9130.
The refractive index is preferably 1.4810 to 1.5000, more preferably 1.4830 to 1.4980, and even more preferably 1.484 to 1.4970.
-Aniline point is preferably 45.0 ° C to 85.0 ° C, more preferably 50.0 ° C to 80.0 ° C, still more preferably 55.0 ° C to 75.0 ° C.
The flash point is preferably 125 ° C. to 160 ° C., more preferably 130 ° C. to 155 ° C., and even more preferably 135 ° C. to 150 ° C.

<Adjustment of compounding ratio of each component>
In the electrically insulating oil composition of one aspect of the present invention, when the electrically insulating oil composition is composed of a low sulfur type mineral oil (A) and an ultrahigh sulfur mineral oil (B1), the low sulfur type mineral oil (A) is used. The content is preferably more than 50% by mass based on the total amount of the electrically insulating oil composition.
Conventionally, by blending a low sulfur type mineral oil (A) in an amount of more than 50% by mass, an electrically insulating oil having a flow point of -40 ° C or less, excellent oxidative stability and initial transparency, and non-corrosive. Although it was difficult to provide the composition, in the electrically insulating oil composition of the present invention, even when the low sulfur type mineral oil (A) is blended in an amount of more than 50% by mass, as described above. By preparing an electrically insulating oil composition using a low sulfur type mineral oil (A) and an ultrahigh sulfur mineral oil (B1), it is possible to obtain an electrically insulating oil composition that satisfies all of these requirements.
When the electrically insulating oil composition is composed of a low sulfur type mineral oil (A) and an ultra-high sulfur type mineral oil (B1), the content of the low sulfur type mineral oil (A) is more preferably 60% by mass or more 95. It is less than mass%, more preferably 70% by mass or more and 90% by mass or less.

Further, in the electric insulating oil composition of one aspect of the present invention, when the electric insulating oil composition is composed of a low sulfur type mineral oil (A), an ultrahigh sulfur mineral oil (B1) and a high sulfur mineral oil (B2). The content of the low sulfur type mineral oil (A) is preferably 40% by mass or more based on the total amount of the electrically insulating oil composition.
Conventionally, even when low sulfur type mineral oil (A) is blended in an amount of 40% by mass or more, the flow point is -40 ° C or less, excellent in oxidative stability and initial transparency, and non-corrosive. Although it was difficult to provide a product, in the electrically insulating oil composition of the present invention, even when 40% by mass or more of the low sulfur type mineral oil (A) is blended, the low sulfur type mineral oil is as described above. By preparing an electrically insulating oil composition using (A), ultra-high sulfur mineral oil (B1) and high-sulfur mineral oil (B2), it is possible to obtain an electrically insulating oil composition that satisfies all of these requirements. ..
When the electrically insulating oil composition is composed of low sulfur type mineral oil (A), ultra high sulfur mineral oil (B1) and high sulfur mineral oil (B2), the content of the low sulfur type mineral oil (A) is higher. It is preferably 35% by mass or more and less than 90% by mass, more preferably 40% by mass or more and 80% by mass or less, and further preferably 45% by mass or more and 80% by mass or less.

<Other processing>
The ultra-low sulfur mineral oil (A1), low-sulfur mineral oil (A2), ultra-high sulfur mineral oil (B1), and high-sulfur mineral oil (B2) are treated with other treatments other than the above, for example, activated charcoal, alumina, silica gel, and the like. It may be treated with a molecular sieve, white clay, or the like.
These treatments may be applied to each of ultra-low sulfur mineral oil (A1), low-sulfur mineral oil (A2), ultra-high sulfur mineral oil (B1), and high-sulfur mineral oil (B2). May be applied after mixing.

<Additives>
The electrically insulating oil composition according to one aspect of the present invention may or may not contain an additive in addition to the above-mentioned components.
In IEC60296, which is an example of the standard of electric insulating oil, it is classified into additive-free oil, trace amount added oil, and additive oil according to the amount of antioxidant added to the electric insulating oil. The amount of the inhibitor added is 0% by mass based on the total amount of the composition for "additive-free oil", less than 0.08% by mass based on the total amount of composition for "trace amount added oil", and 0.08% by mass for "added oil". It is defined as 0.4% by mass or less.
The electrically insulating oil composition according to one aspect of the present invention comprises a phenol-based antioxidant (for example, 2,6-di-tert-butyl-p-cresol, etc.), an amine-based antioxidant, and molybdenum according to the above specifications. One or more kinds of antioxidants selected from the group consisting of amine-based antioxidants and sulfur-based antioxidants may be contained within the above range.
Examples of other additives include a metal inactivating agent, a pour point depressant, and a rust preventive and a flow antistatic agent (for example, a benzotriazole compound that also serves as a rust preventive and a flow antistatic agent). Can be mentioned.

[Acid value and sludge amount of electrically insulating oil composition]
The electrically insulating oil composition according to one aspect of the present invention has an acid value of preferably 0.60 mgKOH / g or less, more preferably 0.50 mgKOH, after the oxidation stability test is carried out by the method described in Examples described later. It is less than / g, more preferably 0.40 mgKOH / g.
Further, in the electrically insulating oil composition of one aspect of the present invention, the sludge amount after the oxidation stability test is carried out by the method described in Examples described later is preferably 0.40% or less, more preferably 0.30. % Or less, more preferably 0.20% or less, still more preferably 0.10% or less.

[Use of the electrically insulating oil composition of the present invention]
The electrically insulating oil composition 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.
Therefore, according to the present invention, there is a method of using the electrically insulating oil composition of the present invention as an insulating material for oil-filled electrical equipment such as an oil-filled capacitor, an oil-filled cable, an oil-filled transformer, and an oil-filled circuit breaker. Provided.

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

[Measurement method of various physical property values]
The measurement of various physical property values of the base oil and the electrically insulating oil composition used in each Example and each Comparative Example was carried out according to the procedure shown below.
(1) Pour point Measured in accordance with JIS K 2269: 1987 (Pour point of crude oil and petroleum products and cloud point test method of petroleum products).
(2) Seibolt color Measured according to JIS K2580: 2003.
(3) Sulfur content Measured in accordance with JIS K 2541-2: 2013 "Crude oil and petroleum products-Sulfur content test method-Microcoefficient titration formula oxidation method".
(4) Corrosion score of copper plate In the corrosive sulfur test (ASTM D1275 B method), the measurement was performed in accordance with JIS K 2513: 2000.
(5) aromatic content _{(% C} A), naphthenes _{(% C} N), and paraffin component _{(% C} P)
Calculated by ring analysis (nd-M method) according to ASTM D3238: 1995.
(6) Dissipation factor Measured according to IEC60247.
(7) Dynamic Viscosity and Viscosity Index The 40 ° C. kinematic viscosity, 100 ° C. kinematic viscosity, and viscosity index were measured and calculated in accordance with JIS K2283: 2000.
(8) Density (15 ° C)
Measurements were made in accordance with JIS K 2249-1: 2011 (crude oil and petroleum products-how to determine density-Part 1: vibration method).
(9) Refractive index (20 ° C)
Measured according to JIS K 0062: 1992.
(10) Aniline point Measured according to JIS K 2256: 2013.
(11) Flash point Measured by the Penske Maltens Sealing Method (PM) method in accordance with JIS K2265-3: 2007.
(12) Acid value Measured according to JIS K 2501-7: 2003.

[Examples, Comparative Examples, and Reference Examples]
First, the base oils shown in Table 1 were prepared.

・ Ultra low sulfur mineral oil (A1)
For ultra-low sulfur mineral oil (A1), hydrogenation reforming treatment is performed on the vacuum distillate obtained by distillation of the atmospheric distillation residual oil of the intermediate base crude oil under reduced pressure, and then hydrogenation isomerization dewaxing is performed. Was used.
・ Low sulfur mineral oil (A2)
The low sulfur mineral oil (A2) was obtained by subjecting the vacuum distillate obtained by distillation of the atmospheric distillation residual oil of the intermediate base crude oil under reduced pressure to a hydrogenation reforming treatment and then solvent dewaxing. I used the one.
・ Low sulfur mineral oil (A3)
The low sulfur mineral oil (A3) is obtained by hydrocracking and then solvent dewaxing the distillate under reduced pressure obtained by distillation of the atmospheric distillation residual oil of the naphthenic base crude oil under reduced pressure. Using.
・ Ultra-high sulfur mineral oil (B1)
As the ultra-high sulfur mineral oil (B1), a distillate obtained by distilling a naphthenic base crude oil under normal pressure was subjected to solvent extraction treatment and further alkali treatment.
・ High sulfur mineral oil (B2) -1
As the high sulfur mineral oil (B2) -1, hydrorefined distillate obtained by distilling naphthenic base crude oil under normal pressure was used.
・ High sulfur mineral oil (B2) -2
As the high sulfur mineral oil (B2) -2, hydrorefined distillate obtained by distilling naphthenic base crude oil under normal pressure was used. However, the conditions for hydrorefining were made more severe than the conditions for hydrorefining during the production of high sulfur mineral oil (B2) -1.

Next, after mixing the base oils with the formulations shown in Tables 2 and 3, white clay treatment was performed to obtain electrically insulating oil compositions of Examples, Comparative Examples, and Reference Examples.
The acid value and sludge amount of the electrically insulating oil compositions of Examples, Comparative Examples, and Reference Examples were measured after performing an oxidation stability test under the following test conditions in accordance with JIS C2101: 2010.
-Test conditions: 120 ° C., 75 hours The acid value after the oxidation stability test was measured according to JIS K 2501-7: 2003.
The sludge amount after the oxidative stability test was measured in accordance with JIS C2101: 2010, and the sludge amount after the oxidative stability test was carried out under the following test conditions.
-Test conditions: 120 ° C., 75 hours In addition, the electric insulating oil compositions of Examples, Comparative Examples, and Reference Examples were subjected to a sulfur corrosion test in accordance with ASTM D1275B to evaluate the corrosiveness to copper.
The acid value of 0.60 mgKOH / g or less was regarded as acceptable.
The sludge amount was 0.40% or less as acceptable.
The results are shown in Tables 2 and 3.

From the results shown in Table 2, the following can be seen.
The electrically insulating oil composition of Examples 1-1 to 1-3 has a pour point of −40 ° C. or lower, a Seibolt color of +20 or higher, excellent oxidative stability, and is non-corrosive. Recognize.
As shown in Reference Example 1-1, when the pour point is higher than -40 ° C and the requirement (1) is not satisfied, the composition of an electrically insulating oil is excellent in oxidative stability and initial transparency and is non-corrosive. It can be seen that it is a product, but when the pour point is -40 ° C or less and the requirement (1) is satisfied, as shown in Comparative Examples 1-1 to 1-3, oxidative stability and initial transparency are obtained. It can be seen that it may not be possible to prepare an electrically insulating oil composition that is both excellent and non-corrosive.
In particular,
It can be seen that an electrically insulating oil composition having a copper plate corrosion score of 4a and not satisfying the requirement (5), such as the electrically insulating oil composition of Comparative Example 1-1, exhibits corrosiveness.
As the electrical insulating oil composition of Comparative Example 1-2, naphthenes (% C _N) is greater than 50, the electrical insulating oil composition which does not satisfy the requirement (4) is inferior in oxidation stability ..
As shown in Reference Example 1, when the pour point is higher than -40 ° C and the requirement (1) is not satisfied, the composition is an electrically insulating oil composition having excellent oxidative stability and initial transparency and being non-corrosive. It turns out to be. That is, when the pour point is higher than -40 ° C and the requirement (1) is not satisfied, it is easy to prepare an electrically insulating oil composition having excellent oxidative stability and initial transparency and being non-corrosive. I understand.

In addition, the following can be seen from the results shown in Table 3.
The electrically insulating oil composition of Examples 2-1 to 2-7 has a pour point of −40 ° C. or lower, a Seibolt color of +20 or higher, excellent oxidative stability, and is non-corrosive. Recognize.
As shown in Reference Example 2-1 when the pour point is higher than -40 ° C and the requirement (1) is not satisfied, the composition of an electrically insulating oil is excellent in oxidative stability and initial transparency and is non-corrosive. It can be seen that it is a product, but when the pour point is -40 ° C or less and the requirement (1) is satisfied, as shown in Comparative Examples 2-1 to 2-6, oxidative stability and initial transparency are obtained. It can be seen that it may not be possible to prepare an electrically insulating oil composition that is both excellent and non-corrosive.
Specifically, as the electrical insulating oil composition of Comparative Example 2-1, copper corrosion rating is the 1b, naphthenes (% C _N) is greater than 46.0, not meet the requirements (5) It can be seen that the electrically insulating oil composition is inferior in oxidative stability.
An electric insulating oil composition having a sulfur content of more than 255 mass ppm, a copper plate corrosion score of 4a, and not satisfying the requirements (3) and (5), such as the electric insulating oil composition of Comparative Example 2-2. , It can be seen that it is corrosive.
As electrical insulating oil compositions of Comparative Examples 2-3 and Comparative Examples 2-5, naphthenes (% C _N) is greater than 50, the electrical insulating oil composition which does not satisfy the requirement (4) is stable oxide It turns out that it is inferior in sex.
An electrically insulating oil composition having a sulfur content of less than 50% by mass and not satisfying the requirement (3), such as the electrically insulating oil compositions of Comparative Examples 2-4 and 2-6, is inferior in oxidative stability. You can see that.

Claims (6)

An electrically insulating oil composition that satisfies the following requirements (1) to (5).
-Requirement (1): The pour point is -40 ° C or less.
-Requirement (2): The Seibolt color is +10 or more.
-Requirement (3): The sulfur content is 50 mass ppm to 255 mass ppm based on the total amount of the electrically insulating oil composition.
- Requirement (4): ring analysis (n-d-M method) According% _{C N} is 50.5 or less.
-Requirement (5): In the corrosive sulfur test (ASTM D1275 B method), the copper plate corrosion test score measured in accordance with JIS K 2513: 2000 is 1a to 3b. However, when the copper plate corrosion test score is 1a~2a it is% by ring analysis (n-d-M method) _{C N} is 46.5 or less. The electrically insulating oil composition according to claim 1, further satisfying the following requirements (α) and (β).
-Requirement (α): The acid value after performing the oxidation stability test under the following test conditions in accordance with JIS C2101: 2010 is 0.60 mgKOH / g or less.
-Requirement (β): The amount of sludge after the oxidation stability test is carried out under the following test conditions in accordance with JIS C2101: 2010 is 0.40% or less based on the total amount of the electrically insulating oil composition.
-Test conditions: 120 ° C, 75 hours The electrically insulating oil composition according to claim 1 or 2, which contains a low-sulfur type mineral oil (A) and a high-sulfur type mineral oil (B). The low-sulfur mineral oil (A) further contains an ultra-low-sulfur mineral oil (A1) having a sulfur content of less than 3 mass ppm.
The electrically insulating oil composition according to any one of claims 1 to 3, further comprising an ultra-high sulfur mineral oil (B1) having a sulfur content of 400 mass ppm or more. The high sulfur type mineral oil (B) may further ring analysis (n-d-M method) According% C _A comprises a high sulfur mineral oil (B2) of 8.0 or higher, the electrical insulating oil according to claim 4 Composition. A method of use, wherein the electrically insulating oil composition according to any one of claims 1 to 5 is used as an insulating material for oil-filled electrical equipment.