Electrical insulating base oil for oil-filled electrical equipment, electrical insulating oil containing the same, and oil-filled electrical equipment

Abstract

To provide an electrical insulating base oil for oil-filled electrical equipment that exhibits excellent partial discharge characteristics and environmental harmony.SOLUTION: An electrical insulating base oil for oil-filled electrical equipment comprises an ester compound (A) represented by the following general formula (I): R1-COO-R2(I), where R1 is an aryl group or an arylalkyl group having 6 to 10 carbon atoms, and R2 is a linear or branched-chain hydrocarbon group having 12 or more carbon atoms.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an electrically insulating base oil for oil-filled electrical equipment, an electrically insulating oil containing the same, and an oil-filled electrical equipment. [Background technology]

[0002] Conventionally, electrical insulating oil has been used in oil-filled electrical equipment such as transformers, cables, circuit breakers, and capacitors for the purpose of insulation and cooling. Because oil-filled electrical equipment is used under high electric fields, there is a possibility of partial discharge occurring inside the equipment. Therefore, insulating oil used in oil-filled electrical equipment is required to have excellent partial discharge characteristics, i.e., it is difficult for partial discharge to occur under high electric fields (high partial discharge inception voltage) and even if partial discharge does occur, it is quickly extinguished (high partial discharge extinction voltage).

[0003] Mineral oil, silicone oil, PCB (polychlorinated biphenyl), dibenzyltoluene, etc. have been used as base oils for electrical insulating oils. However, these base oils are generally poorly biodegradable, and the environmental impact they pose is a concern when they leak into the environment. Furthermore, mineral oil is a limited resource, so its use may be restricted in the future. Silicone oil generally has high viscosity and low thermal conductivity. As a result, it has a poor cooling effect for oil-filled electrical equipment, making it difficult to construct such equipment in a compact size.

[0004] In recent years, the use of highly biodegradable vegetable oils and fatty acid esters as base oils for electrical insulating oils has been studied. For example, Patent Document 1 discloses an electrical insulating oil containing vegetable oil. Patent Document 2 discloses that a higher fatty acid ester-based solvent containing a higher fatty acid ester compound is effective for applications such as electrical insulating oil.

[0005] However, the techniques of Patent Documents 1 and 2 do not provide sufficient partial discharge characteristics. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-287788 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-149705 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, substances that are persistent, bioaccumulative, and toxic have become known as PBT (persistent bioaccumulative toxic) substances, and their use has been restricted in many areas. In particular, restrictions on the use of chemical substances are becoming increasingly strict in Europe and other countries, and environmental friendliness is also becoming a focus of attention when it comes to the use of base oils for electrical insulating oils. For example, in the GHS classification, 2-ethylhexyl benzoate is classified as Category 2, a chemical substance suspected of reproductive toxicity to humans, and its use may be restricted. For this reason, there is a demand for the development of environmentally friendly electrical insulating base oils that do not contain PBT substances.

[0008] The present invention has been made in view of the above circumstances, and has as its object to provide an electrical insulating base oil for oil-filled electrical devices that has good partial discharge characteristics and is environmentally friendly. [Means for solving the problem]

[0009] As a result of extensive research, the present inventors have found that the following electrical insulating base oil for oil-filled electrical devices can solve the above problems.

[0010] That is, the present invention has the following configuration. [1] An electrical insulating base oil for oil-filled electrical devices, comprising an ester compound (A) represented by the following general formula (I): R 1 -COO-R 2 (I) However, in formula (I), R 1is an aryl group having 6 to 10 carbon atoms or an arylalkyl group having 6 to 10 carbon atoms, and R 2 is a linear hydrocarbon group having 12 or more carbon atoms or a branched hydrocarbon group having 12 or more carbon atoms. [2] In the formula (I), R 1 is an aryl group having 6 to 10 carbon atoms. [3] In the formula (I), R 2 is a branched hydrocarbon group having 12 or more carbon atoms. [4] In the formula (I), R 2 The electrically insulating base oil for an oil-filled electrical device according to any one of [1] to [3], wherein is a branched hydrocarbon group having 12 to 15 carbon atoms. [5] The electrical insulating base oil for oil-filled electrical devices according to any one of [1] to [4], which contains at least one compound (B) selected from the group consisting of alkylbenzenes, alkylnaphthalenes, diarylalkanes, triarylalkanes, and mineral oils. [6] The electrical insulating base oil for oil-filled electrical devices according to [5], wherein the mass ratio of component (A) / component (B) is 90 / 10 to 20 / 80. [7] An electrical insulating oil containing the electrical insulating base oil for oil-filled electrical devices according to any one of [1] to [6]. [8] An oil-filled electrical device comprising the electrical insulating oil according to [7]. [Effects of the Invention]

[0011] The electrical insulating base oil for oil-filled electrical devices of the present invention has good partial discharge characteristics and is environmentally friendly. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a capacitor. [Figure 2] FIG. 1 is a schematic diagram illustrating an example of a cable. DETAILED DESCRIPTION OF THE INVENTION

[0013] (electrical insulating base oil for oil-filled electrical equipment) The electrically insulating base oil for oil-filled electrical devices of the present invention (hereinafter also simply referred to as "electrically insulating base oil") contains a specific ester compound (component (A)). By virtue of having this characteristic, the electrically insulating base oil of the present invention can suppress the occurrence of partial discharge even when used under a high electric field. Furthermore, by virtue of having this characteristic, the electrically insulating base oil of the present invention can be used as an electrically insulating oil for oil-filled electrical devices while reducing the burden on the environment.

[0014] The biodegradability of the electrical insulating base oil is preferably 60% or more, more preferably 70% or more, even more preferably 75% or more, particularly preferably 80% or more, and may be 100%. The biodegradability is measured after 28 days in accordance with the Manometric Respirometry Test (Guideline 301F, July 17, 1992) specified in the OECD Guideline for Testing of chemicals.

[0015] In this specification, "the electrical insulating base oil is environmentally friendly" means, for example, that it has a low load on humans and the environment and is therefore highly environmentally friendly. More specifically, it means, for example, that it does not contain any substances classified as carcinogenic, mutagenic, or reproductively toxic in Category 1 or Category 2 in Annex III of the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH).

[0016] The kinematic viscosity of the electrical insulating base oil at 40°C is 0.1 mm 2 / s~8mm 2 / s is preferred, 0.5 mm 2 / s~4mm 2 When the kinematic viscosity of the electrical insulating base oil is within the above-mentioned preferred range, the cooling effect of the oil-filled electrical equipment can be easily obtained. 2 / s~8mm2 / s" is "0.1mm 2 / s or more 8mm 2 / s or less" and the same applies to other numerical ranges indicated by "~".

[0017] In this specification, the kinematic viscosity can be measured in accordance with JIS K2283:2000 (Crude oil and petroleum products - Test method for kinematic viscosity and calculation method for viscosity index).

[0018] The pour point of the electrical insulating base oil is preferably −25° C. or lower, more preferably lower than −35° C. When the pour point of the electrical insulating base oil is the above-mentioned upper limit or lower, it becomes easier to obtain an electrical insulating oil that is highly versatile and has no restrictions on use even in cold regions, etc.

[0019] In this specification, the pour point can be measured in accordance with "3. Pour point test method" of JIS K 2269:1987 (Test methods for pour point and cloud point of crude oil and petroleum products).

[0020] In this specification, "insulating" refers to a dielectric breakdown voltage of 40 kV or more when measured in accordance with "22. Dielectric breakdown voltage test" of JIS C 2101:2010 (Test methods for electrical insulating oils).

[0021] <Component (A)> Component (A) is an ester compound represented by the following general formula (I): By containing component (A), the electrical insulating base oil of the present invention has good partial discharge characteristics and environmental friendliness. R 1 -COO-R 2 (I) However, in formula (I), R 1 is an aryl group having 6 to 10 carbon atoms or an arylalkyl group having 6 to 10 carbon atoms, and R 2 is a linear hydrocarbon group having 12 or more carbon atoms or a branched hydrocarbon group having 12 or more carbon atoms.

[0022] In formula (I), R 1 is an aryl group having 6 to 10 carbon atoms or an arylalkyl group having 6 to 10 carbon atoms.1 Examples of R include phenyl, o-tolyl, m-tolyl, p-tolyl, 2,3-xylyl, 2,4-xylyl, mesityl, 1-naphthyl, 2-naphthyl, benzyl, 2-phenylethyl, 1-phenylethyl, 2-phenyl-1-propyl, 3-phenyl-1-propyl, and 1-phenyl-1-butyl groups. Among these, R is particularly preferred because it is likely to provide good partial discharge characteristics. 1 is preferably a phenyl group, an o-tolyl group, an m-tolyl group, a p-tolyl group, a benzyl group, a 2-phenylethyl group, or a 1-phenylethyl group.

[0023] In formula (I), R 2 R is a linear or branched hydrocarbon group having 12 or more carbon atoms, preferably a linear or branched hydrocarbon group having 12 to 17 carbon atoms, more preferably a linear or branched hydrocarbon group having 12 to 15 carbon atoms, and more preferably a linear or branched hydrocarbon group having 12 to 15 carbon atoms. 2 When the number of carbon atoms in R is within the above range, the partial discharge characteristics and environmental friendliness are good. 2 If the number of carbon atoms is less than 12, it may be toxic to living organisms. 2 If the number of carbon atoms is too large, the kinematic viscosity becomes high, and there is a risk that a sufficient cooling effect for oil-filled electrical equipment cannot be obtained.

[0024] R 2 may be a saturated or unsaturated hydrocarbon group.

[0025] R 2 Examples of R include a linear alkyl group having 12 or more carbon atoms or a branched alkyl group having 12 or more carbon atoms, an alkenyl group, and an alkynyl group. 2 Examples of the alkyl group include a dodecyl group, a 2-butyl-1-n-octyl group, a tridecyl group, a tridecenyl group, a tetradecyl group, a pentadecyl group, a pentadecenyl group, a hexadecyl group, a 2-hexyl-1-decyl group, a heptadecyl group, a heptadecenyl group, a heptadecadienyl group, a heptadecatrienyl group, and a heptadecatetraenyl group.

[0026] R 2 R is preferably a branched hydrocarbon group. 2 However, if the hydrocarbon group is a branched chain, the low-temperature fluidity is more likely to be improved. The branched chain hydrocarbon group in the present invention also includes a group in which the carbon atom bonded to the oxygen atom of the ester group in formula (I), such as a 2-butyl-1-n-octyl group, is a secondary carbon atom.

[0027] As component (A), from the viewpoint of further improving the partial discharge extinction voltage, preferred are benzoate esters such as dodecyl benzoate, tridecyl benzoate, tetradecyl benzoate, pentadecyl benzoate, and 2-butyl-1-n-octyl benzoate; and phenylacetate esters such as dodecyl phenylacetate, tridecyl phenylacetate, and 2-butyl-1-n-octyl phenylacetate.

[0028] Among these, dodecyl benzoate and pentadecyl benzoate are preferred because they improve the partial discharge extinction voltage and provide good low-temperature fluidity, and 2-butyl-1-n-octyl benzoate and the like are preferred because they are environmentally friendly.

[0029] The component (A) may be used alone or in combination of two or more.

[0030] [Method of producing component (A)] Examples of methods for producing component (A) include (i) a method involving transesterification between a fat or oil and an alcohol having a linear or branched hydrocarbon group having 12 or more carbon atoms, (ii) a method involving esterification of a carboxylic acid with an alcohol having a linear or branched hydrocarbon group having 12 or more carbon atoms, and (iii) a method involving transesterification of an ester with an alcohol having a linear or branched hydrocarbon group having 12 or more carbon atoms.

[0031] Examples of the oils and fats used in the method (i) include bergamot resin, mineral oil, synthetic oils and fats, peppermint oil, rose oil, neroli oil, olive oil, cacao oil, perilla oil, camellia oil, peanut oil, soybean oil, rapeseed oil, mustard oil, dehydrated castor oil, tung oil, safflower oil, linseed oil, corn oil, sunflower oil, corn oil, cottonseed oil, sesame oil, rice bran oil, hemp oil, evening primrose oil, palm oil, palm kernel oil, coconut oil, etc. Furthermore, oils and fats that have been used for food or the like may be reused as the oils and fats.

[0032] The method (i) can be carried out by a conventionally known method.

[0033] Examples of the carboxylic acid used in the method (ii) include benzoic acid, phenylacetic acid, etc. Furthermore, carboxylic acids that have been used for food or the like may be reused as the carboxylic acid.

[0034] As the carboxylic acid, benzoic acid and phenylacetic acid are preferred, as they tend to improve the partial discharge characteristics of component (A) and tend to provide good low-temperature fluidity.

[0035] The method (ii) can be carried out by a known method, for example, by gradually increasing the temperature from room temperature to 200°C while gradually reducing the pressure from normal pressure to 0.7 KPa and removing the by-produced water.

[0036] The catalyst used in the method (ii) is not particularly limited, but examples thereof include acid catalysts such as sulfuric acid, p-toluenesulfonic acid (p-TS), benzenesulfonic acid (BS), and methanesulfonic acid; inorganic oxide catalysts such as ZrO, TiO, SiO, PO, AlO, and ZnO; basic catalysts such as hydroxides, hydrogencarbonates, carbonates, sodium methoxide, and potassium methoxide of lithium, cesium, sodium, potassium, magnesium, barium, and calcium; organic titanium compound catalysts such as tetraisopropyl titanate, tetra-n-butyl titanate, tetraethanolamine titanate, and tetrastearyl titanate; and organic zirconium compound catalysts such as normal propyl zirconate, normal butyl zirconate, zirconium tetraacetylacetonate, and zirconium monoacetylacetonate.

[0037] Examples of the ester in the method (iii) include the ester compounds of the carboxylic acid in the method (ii). The ester compounds are preferably ester compounds formed from the same carboxylic acids as those preferred in the method (ii).

[0038] The method (iii) can be carried out by a known method, for example, by gradually increasing the temperature from room temperature to 200°C while gradually reducing the pressure from normal pressure to 0.7 KPa, and removing the by-produced alcohols.

[0039] The catalyst used in the method (iii) is not particularly limited, but examples thereof include hydroxides of lithium, cesium, sodium, potassium, magnesium, barium, calcium, and the like; basic catalysts such as hydrogen carbonates, carbonates, sodium methoxide, and potassium methoxide; organic titanium compound catalysts such as tetraisopropyl titanate, tetra-n-butyl titanate, tetraethanolamine titanate, and tetrastearyl titanate; and organic zirconium compound catalysts such as normal propyl zirconate, normal butyl zirconate, zirconium tetraacetylacetonate, and zirconium monoacetylacetonate.

[0040] In order to improve electrical properties such as partial discharge characteristics, the method for producing component (A) preferably involves refining such as alcohol removal, glycerin separation, inorganic component removal, neutralization, water washing, distillation, adsorption treatment, and degassing treatment. Among these, adsorption treatment and / or degassing treatment are preferred. Adsorption treatment reduces the acid value of the electrical insulating base oil, making it easier to improve electrical properties. Degassing treatment reduces the water content of the electrical insulating base oil, making it easier to improve electrical properties.

[0041] The adsorption treatment is carried out by adding an adsorbent such as activated clay or activated alumina to the reaction liquid after the completion of the reaction to adsorb the free carboxylic acid, acid catalyst, etc., and then removing the adsorbent by filtration.

[0042] Examples of the adsorbent include the Kyoward series, such as Kyoward 100, 200, 300, 400, 500, 600, 700, 1000, and 2000 (all trade names) manufactured by Kyowa Chemical Industry Co., Ltd., which are inorganic synthetic adsorbents mainly composed of Mg, Al, Si, etc.; the Kyowamag series, such as Kyowamag 30 and 150 (all trade names) manufactured by Kyowa Chemical Industry Co., Ltd.; and the Tomita-AD series, such as Tomita-AD100, 500, 600, and 700 (all trade names) manufactured by Tomita Pharmaceutical Co., Ltd.

[0043] The adsorbent is preferably added in an amount of 0.01 to 5 parts by mass per 100 parts by mass of the ester compound obtained by the reaction. The adsorption treatment is preferably carried out at a temperature of 20 to 160°C in the atmosphere, in an inert gas atmosphere such as nitrogen or argon, or under reduced pressure for 10 minutes to 5 hours.

[0044] By such an adsorption treatment, the acid value of the component (A) can be reduced to preferably 0.0001 mgKOH / g to 0.01 mgKOH / g, and more preferably 0.0001 mgKOH / g to 0.005 mgKOH / g, thereby further improving the electrical properties.

[0045] The acid value can be measured according to "16. Acid value test" in JIS C 2101:2010 (Testing methods for electrical insulating oils).

[0046] The degassing treatment is carried out by replacing the atmosphere in the reactor with nitrogen, reducing the pressure at 20°C to 160°C and a vacuum of 0.1 kPa to 80 kPa for 10 minutes to 5 hours, and distilling off water and air from the reaction solution after the reaction. At this time, azeotropy may be performed by adding 0.1 mol to 3 mol of a compound that forms an azeotrope with water, such as toluene, isopropyl alcohol, ethanol, or pyridine, based on the water content of the reaction solution.

[0047] By such degassing treatment, the water content in component (A) can be reduced to preferably 0.1 ppm to 100 ppm, and more preferably 0.1 ppm to 50 ppm.

[0048] The moisture content can be measured using the method described in "20. Moisture test" of JIS C 2101:2010 (Testing methods for electrical insulating oils).

[0049] After degassing, component (A) is preferably stored under a nitrogen atmosphere or dry air to prevent it from absorbing moisture again. Component (A) may also be stored with 0.1 to 30 parts by mass of a dehydrating agent, such as Molecular Sieves 4A (trade name, manufactured by Junsei Chemical Co., Ltd.), added per 100 parts by mass of component (A). This allows the moisture content to be maintained within the above-mentioned preferred range for a long period of time.

[0050] The content of component (A) is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 40% by mass or more, based on the total mass of the electrical insulating base oil. It may be 100% by mass, i.e., the electrical insulating base oil is composed only of component (A). When the content of component (A) is equal to or greater than the above lower limit, partial discharge characteristics and environmental friendliness tend to be good.

[0051] The content of component (A) is preferably 10% by mass to 100% by mass, more preferably 20% by mass to 90% by mass, and even more preferably 40% by mass to 80% by mass, based on the total mass of the electrical insulating base oil.

[0052] <(B) component> Component (B) is at least one compound selected from the group consisting of alkylbenzenes, alkylnaphthalenes, diarylalkanes, triarylalkanes, and mineral oils.

[0053] By using component (B), the partial discharge extinction voltage is likely to be increased, and further, the low-temperature fluidity is likely to be improved.

[0054] Alkylbenzene is an aromatic hydrocarbon in which an alkyl group is bonded to one benzene ring. The alkyl group may be linear or branched. One or more alkyl groups may be bonded to the benzene ring. Examples of alkylbenzene include monoalkylbenzene, dialkylbenzene, trialkylbenzene, and tetraalkylbenzene.

[0055] The alkyl group of the alkylbenzene preferably has 1 to 30 carbon atoms, more preferably 3 to 30 carbon atoms, still more preferably 4 to 24 carbon atoms, and particularly preferably 10 to 20 carbon atoms.

[0056] The alkylbenzene is preferably one in which 1 to 4 alkyl groups are bonded to a benzene ring. Furthermore, the alkylbenzene is preferably one in which the total number of carbon atoms in the alkyl groups bonded to the benzene ring is 3 to 30, more preferably one in which the total number of carbon atoms in the alkyl groups is 4 to 24, and even more preferably one in which the total number of carbon atoms in the alkyl groups is 10 to 20. When an alkylbenzene is blended into an electrical insulating base oil, low-temperature fluidity tends to be improved.

[0057] Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, an icosyl group, a henicosyl group, a docosyl group, a tricosyl group, a tetracosyl group, a pentacosyl group, a hexacosyl group, a heptacosyl group, an octacosyl group, a nonacosyl group, and a triancotyl group. These alkyl groups may be linear or branched.

[0058] As the alkylbenzene, from the viewpoint of facilitating an increase in the partial discharge extinction voltage, the alkyl group bonded to the benzene ring preferably has a total carbon number of 10 to 20. Furthermore, the alkyl group is preferably a linear or branched decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, heptadecyl group, octadecyl group, nonadecyl group, or icosyl group.

[0059] The alkylbenzenes may be used alone or in combination of two or more.

[0060] Specific examples of alkylbenzenes include decylbenzene, undecylbenzene, dodecylbenzene, tridecylbenzene, tetradecylbenzene, heptadecylbenzene, octadecylbenzene, nonadecylbenzene, and icosylbenzene.

[0061] The method for producing alkylbenzene is not particularly limited, and known methods can be used. Examples of the production method include a method in which a raw material consisting of benzene, toluene, xylene, ethylbenzene, methylethylbenzene, diethylbenzene, or a mixture thereof is alkylated using an alkylating agent. Examples of the alkylating agent include linear or branched olefins obtained by polymerization of lower monoolefins such as ethylene, propylene, butene, and isobutylene; linear or branched olefins obtained by thermal cracking of wax, heavy oil, petroleum fractions, polyethylene, polypropylene, etc.; linear olefins obtained by separating n-paraffins from petroleum fractions such as kerosene and diesel and olefinating them using a catalyst; and mixtures thereof.

[0062] Alkylnaphthalene is an aromatic hydrocarbon in which an alkyl group is bonded to one naphthalene ring. Examples of the alkyl group include the same alkyl groups as those bonded to the alkylbenzene. One or more alkyl groups may be bonded to the naphthalene ring.

[0063] The alkyl group of the alkylnaphthalene preferably has 1 to 30 carbon atoms, more preferably 3 to 30 carbon atoms, even more preferably 10 to 25 carbon atoms, and particularly preferably 14 to 20 carbon atoms. As the alkylnaphthalene, one in which 1 to 4 alkyl groups are bonded to a naphthalene ring is preferred. Furthermore, as the alkylnaphthalene, from the viewpoint of easily increasing the partial discharge extinction voltage, one in which the total number of carbon atoms in the alkyl groups bonded to the naphthalene ring is 3 to 30 is preferred, one in which the total number of carbon atoms in the alkyl groups is 6 to 24 is more preferred, and one in which the total number of carbon atoms in the alkyl groups is 14 to 20 is even more preferred.

[0064] The alkylnaphthalene may be used alone or in combination of two or more.

[0065] Specific examples of alkylnaphthalenes include decylnaphthalene, undecylnaphthalene, dodecylnaphthalene, tridecylnaphthalene, tetradecylnaphthalene, heptadecylnaphthalene, octadecylnaphthalene, nonadecylnaphthalene, and icosylnaphthalene.

[0066] The method for producing alkylnaphthalene is not particularly limited, and alkylnaphthalene can be produced by various known methods. For example, there is a method in which a halide of a hydrocarbon having 14 to 20 carbon atoms or an olefin having 14 to 20 carbon atoms is added to naphthalene in the presence of an acid catalyst such as a Friedel-Crafts catalyst, which is a mineral acid such as sulfuric acid, phosphoric acid, tungstosilicic acid, or hydrofluoric acid, a solid acidic substance such as acid clay or activated clay, or a metal halide such as aluminum chloride or zinc chloride.

[0067] Examples of diarylalkanes include alkane compounds having two aromatic hydrocarbon groups in the molecule, such as diphenylmethane, benzyltoluene, benzylxylene, phenyl-sec-butylphenylmethane, di-sec-butyldiphenylmethane, diphenylethane, phenylethylphenylethane, phenylcumylethane, diisopropylphenylethane, phenyltolylethane, di-sec-butylphenylethane, di-tert-butylphenylethane, phenylxylylethane, phenyl-sec-butylphenylethane, diphenylpropane, diphenylbutane, ditolylethane, dixylyloctane, and dixylyldecane.

[0068] Of these, phenylethylphenylethane or phenylxylylethane is preferred.

[0069] Examples of phenylethylphenylethanes include 1-phenyl-1-(2-ethylphenyl)ethane, 1-phenyl-1-(3-ethylphenyl)ethane, 1-phenyl-1-(4-ethylphenyl)ethane, 1-phenyl-2-(2-ethylphenyl)ethane, etc. Examples of phenylxylylethanes include 1-phenyl-1-(2,3-dimethylphenyl)ethane, 1-phenyl-1-(2,4-dimethylphenyl)ethane, 1-phenyl-1-(2,5-dimethylphenyl)ethane, 1-phenyl-1-(2,6-dimethylphenyl)ethane, 1-phenyl-1-(3,4-dimethylphenyl)ethane, 1-phenyl-1-(3,5-dimethylphenyl)ethane, 1-phenyl-2-(2,3-dimethylphenyl)ethane, etc.

[0070] The diarylalkane preferably has a total of 13 to 30 carbon atoms, and more preferably 13 to 20 carbon atoms.

[0071] The diarylalkane may be used alone or in combination of two or more.

[0072] Triarylalkanes include alkane compounds having three aromatic hydrocarbon groups in the molecule, such as dibenzylbenzene, dibenzyltoluene, dibenzylxylene, and alkyl group-substituted derivatives thereof.

[0073] The total number of carbon atoms in the triarylalkane is preferably 19 to 30, and more preferably 19 to 26.

[0074] The triarylalkane may be used alone or in combination of two or more.

[0075] Examples of mineral oils include those obtained by distillation and refinement of heavy oils. Examples of the mineral oil include paraffinic or naphthenic mineral oils obtained by atmospheric and vacuum distillation of paraffinic, intermediate, or naphthenic crude oils, followed by one or more refining methods, such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, and clay treatment, on lubricating oil fractions. Among these, highly refined mineral oils are preferred because of their superior thermal stability. Examples of the mineral oil include refined oils obtained by refining distillates obtained by atmospheric distillation of paraffinic, intermediate, or naphthenic crude oils or by vacuum distillation of the residual oil from atmospheric distillation according to conventional methods, deeply dewaxed oils obtained by further deep dewaxing treatment after refining, and hydrogenated oils obtained by hydrotreating.

[0076] As a mineral oil, the kinematic viscosity at 40°C is 0.1 mm 2 / s~100mm 2 / s is preferable, and 0.1 mm 2 / s~50mm 2 / s is more preferable, and 0.1 mm 2 / s~10mm 2 The kinematic viscosity may be adjusted by using one mineral oil or by mixing two or more mineral oils having different kinematic viscosities.

[0077] As component (B), alkylbenzene or alkylnaphthalene is preferred, and alkylbenzene is more preferred, because they provide an excellent balance between partial discharge characteristics and environmental friendliness when used in combination with component (A).Among alkylbenzenes, monoalkylbenzenes having a linear alkyl group having 10 to 20 carbon atoms are particularly preferred.

[0078] The component (B) may be used alone or in combination of two or more.

[0079] The content of component (B) is preferably 0% by mass to 80% by mass, more preferably 10% by mass to 80% by mass, even more preferably 20% by mass to 70% by mass, and particularly preferably 35% by mass to 65% by mass, relative to the total mass of the electrical insulating base oil.

[0080] When the content of the component (B) is equal to or greater than the above lower limit, it is easier to increase the partial discharge extinction voltage and the low-temperature fluidity.

[0081] When the electrical insulating base oil contains the (B) component, the mass ratio of the (A) component / the (B) component [mass ratio of the (A) component to the (B) component] is preferably 90 / 10 to 20 / 80, more preferably 80 / 20 to 30 / 70, and even more preferably 65 / 35 to 35 / 65. When the mass ratio represented by component (A) / component (B) is within the above range, it becomes easier to obtain an electrical insulating base oil that has good partial discharge characteristics and biodegradability.

[0082] The total content of components (A) and (B) is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, based on the total mass of the electrical insulating base oil. It may even be 100% by mass, i.e., the electrical insulating base oil is composed only of components (A) and (B). When the total content of components (A) and (B) is within the above-mentioned preferred range, good partial discharge characteristics and environmental friendliness are likely to be achieved.

[0083] The electrical insulating base oil of the present invention preferably contains an ester compound (A) which is an alkyl benzoate, and at least one compound (B) selected from the group consisting of alkylbenzene, alkylnaphthalene, diarylalkane, triarylalkane, and mineral oil.

[0084] The electrical insulating base oil of the present invention comprises an ester compound (A) which is an alkyl benzoate, and at least one compound (B) selected from the group consisting of alkylbenzene, alkylnaphthalene, dibenzyltoluene, and phenylxylylethane, The content of component (A) is 20% by mass to 100% by mass relative to the total mass of the electrical insulating base oil, The content of component (B) is 0% by mass to 80% by mass relative to the total mass of the electrical insulating base oil, The total amount of component (A) and component (B) is preferably 100% by mass or less of the total mass.

[0085] The electrical insulating base oil of the present invention preferably comprises an ester compound (A) that is an alkyl benzoate.

[0086] The electrical insulating base oil of the present invention comprises an ester compound (A) which is an alkyl benzoate, and at least one compound (B) selected from the group consisting of alkylbenzene, alkylnaphthalene, dibenzyltoluene, and phenylxylylethane, The content of component (A) is 20% by mass to 90% by mass relative to the total mass of the electrical insulating base oil, The content of component (B) is 10% by mass to 80% by mass relative to the total mass of the electrical insulating base oil, The total amount of component (A) and component (B) is preferably 100% by mass or less of the total mass.

[0087] (electrical insulating oil for oil-filled electrical equipment) The electrically insulating oil for oil-filled electrical devices of the present invention (hereinafter also simply referred to as "electrically insulating oil") contains the above-mentioned electrically insulating base oil.

[0088] The content of the electrically insulating base oil is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, and may be 100% by mass, based on the total mass of the electrically insulating oil. When the content of the electrically insulating base oil is equal to or more than the lower limit, the partial discharge characteristics and environmental friendliness of the electrically insulating oil tend to be good.

[0089] The biodegradability of the electrical insulating oil is preferably 60% or more, more preferably 70% or more, even more preferably 75% or more, particularly preferably 80% or more, and may be 100%. The biodegradability is measured in the same manner as in the measurement method for the biodegradability of electrical insulating oil base oils.

[0090] It is preferable that the electrical insulating oil has good environmental compatibility. Specifically, it is preferable that the electrical insulating oil is substantially free of, and more preferably free of, substances classified as carcinogenic, mutagenic, and toxic to reproduction in Category 1 or Category 2 in Annex III of the Regulation on Registration, Evaluation, Authorization and Restriction of Chemicals (REACH).

[0091] The kinematic viscosity of electrical insulating oil at 40°C is 0.1 mm 2 / s~8mm 2 / s is preferred, 0.5 mm 2 / s~4mm 2 When the kinematic viscosity of the electrical insulating oil is within the above-mentioned preferred range, the cooling effect on the oil-filled electrical device is easily obtained.

[0092] The pour point of the electrical insulating oil is preferably −25° C. or lower, more preferably lower than −35° C. When the pour point of the electrical insulating oil is equal to or lower than the upper limit, good usability is obtained even in cold regions, etc., and the versatility of the electrical insulating oil is enhanced.

[0093] In addition to the above-mentioned electrical insulating base oil, the electrical insulating oil may contain other components commonly used in electrical insulating oil. Examples of other components include base oils other than the above-mentioned components (A) and (B), and additives such as antioxidants, pour point depressants, metal deactivators, and decomposition inhibitors. However, in order to obtain better partial discharge characteristics and environmental friendliness, the content of base oils other than components (A) and (B) is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, based on the total mass of the electrical insulating oil.

[0094] Examples of the antioxidant include phenolic antioxidants such as dibutylhydroxytoluene and butylhydroxyanisole; amine antioxidants such as phenyl-α-naphthylamine and N,N-di(2-naphthyl)-p-phenylenediamine; vitamin E compounds such as tocopherol, d-tocopherol, dl-α-tocopherol, α-tocopherol acetate, dl-α-tocopherol acetate, tocopherol acetate, and α-tocopherol; vitamin C compounds such as ascorbic acid, ascorbic acid salts, and ascorbyl stearate; green tea extract; green coffee extract; sesamol; and sesaminol. Among these, phenolic antioxidants are preferred due to their excellent solubility in the base oil of the electrical insulating oil. Adding an antioxidant to the electrical insulating oil tends to improve oxidation stability during storage and long-term use.

[0095] The antioxidants may be used alone or in combination of two or more.

[0096] When the electrical insulating oil of the present invention contains an antioxidant, the content of the antioxidant is preferably 0.01 to 5 parts by mass per 100 parts by mass of the electrical insulating base oil.

[0097] Examples of the pour point depressant include sucrose fatty acid esters and acrylic polymers such as polyalkyl methacrylates and polyalkyl acrylates. The acrylic polymers preferably have a weight-average molecular weight of approximately 5,000 to 500,000. Examples of the acrylic polymers include polymers having a linear or branched alkyl group having 1 to 20 carbon atoms, such as polymethyl acrylate, polymethyl methacrylate, polypropyl acrylate, polypropyl methacrylate, polyheptyl acrylate, polyheptyl methacrylate, polynonyl acrylate, polynonyl methacrylate, polyundecyl acrylate, polyundecyl methacrylate, polytridecyl acrylate, polytridecyl methacrylate, polypentadecyl acrylate, polypentadecyl methacrylate, polyheptadecyl acrylate, and polyheptadecyl methacrylate. Commercially available acrylate polymers may also be used. As the commercially available product, the Aclub 100 series (Aclub 132, 133, 136, 137, 138, 146, 160, all trade names) manufactured by Sanyo Chemical Industries, Ltd. is preferred because of its pour point lowering effect and excellent handleability.

[0098] When the electrical insulating oil of the present invention contains a pour point depressant, the content of the pour point depressant is preferably 0.01 to 5 parts by mass, and more preferably 0.01 to 3 parts by mass, per 100 parts by mass of the electrical insulating base oil. When the content of the pour point depressant is equal to or greater than the lower limit, low-temperature fluidity is likely to be improved. When the content of the pour point depressant is equal to or less than the upper limit, an increase in viscosity of the electrical insulating oil is likely to be suppressed.

[0099] Examples of the metal deactivator include 4-alkyl-benzotriazoles such as benzotriazole, 4-methyl-benzotriazole, and 4-ethyl-benzotriazole; 5-alkyl-benzotriazoles such as 5-methyl-benzotriazole and 5-ethyl-benzotriazole; 1-alkyl-benzotriazoles such as 1-dioctylaminomethyl-2,3-benzotriazole; and 1-alkyl-benzotriazoles such as 1-dioctylaminomethyl-2,3-tolutriazole. Benzotriazole derivatives such as tolutriazoles; 2-(alkyldithio)benzimidazoles such as benzimidazole, 2-(octyldithio)benzimidazole, 2-(decyldithio)benzimidazole, and 2-(dodecyldithio)benzimidazole; benzotriazole derivatives such as 2-(octyldithio)-toluimidazole, 2-(decyldithio)-toluimidazole, and 2-(dodecyldithio)-toluimidazole; Imidazole derivatives; thiazole, benzothiazole, 2-mercaptobenzothiazole derivatives; 2-(alkyldithio)benzothiazoles such as 2-(hexyldithio)benzothiazole and 2-(octyldithio)benzothiazole; 2-(alkyldithio)toluthiazoles such as 2-(hexyldithio)toluthiazole and 2-(octyldithio)toluthiazole; 2-(N,N-diethyldithiocarbamyl)benzothiazole, 2-(N,N-dibutyldithiocarbamyl)benzothiazole, and benzothiazole derivatives such as 2-(N,N-dialkyldithiocarbamyl)benzothiazoles such as 2-(N,N-diethyldithiocarbamyl)toruthiazole, 2-(N,N-dibutyldithiocarbamyl)toruthiazole, and 2-(N,N-dihexyldithiocarbamyl)toruthiazole. Among these, benzotriazole derivatives are preferred because they also function as flow antistatic agents.

[0100] The metal deactivators may be used alone or in combination of two or more.

[0101] When the electrical insulating oil of the present invention contains a metal deactivator, the content of the metal deactivator is preferably 0.0001 to 0.5 parts by mass, and more preferably 0.0005 to 0.1 parts by mass, per 100 parts by mass of the electrical insulating base oil.

[0102] Examples of the decomposition inhibitor include carbodiimide compounds such as bis(alkylphenyl)carbodiimides, such as diphenylcarbodiimide, ditolylcarbodiimide, bis(isopropylphenyl)carbodiimide, and bis(butylphenyl)carbodiimide; phenyl glycidyl ether, phenyl glycidyl ester, alkyl glycidyl ether, alkyl glycidyl ester, 3,4-epoxycyclohexylmethyl(3,4-epoxycyclohexane)carboxylate, vinylcyclohexene diepoxide, 3,4-epoxy-6-methylcyclohexylmethyl(3,4-epoxy-6-methylhexane)carboxylate, phenol novolac epoxy compounds, which are diglycidyl ether epoxy compounds of bisphenol A; and epoxy compounds such as orthocresol novolac epoxy compounds. When the electrical insulating oil of the present invention contains a decomposition inhibitor, deterioration due to heat, oxygen, etc. is more easily suppressed.

[0103] The electrical insulating oil of the present invention is produced by a conventionally known production method, for example, a method in which other components are added to an electrical insulating base oil and then mixed.

[0104] The electrical insulating oil of the present invention can be used as an insulating oil for oil-filled electrical devices.

[0105] (oil-filled electrical equipment) The oil-filled electrical device of the present invention includes the above-mentioned electrical insulating oil. Examples of the oil-filled electrical device include a transformer, a reactor, a tap changer, a cable, a bushing, a voltage transformer, a capacitor, and a current transformer.

[0106] The capacitor in Figure 1 comprises capacitor element 1, which is wound around a dielectric such as polypropylene film and electrodes such as metal foil; lead pieces 2 formed of copper foil or the like extending from capacitor element 1; metal case 3 with an opening for accommodating capacitor element 1; insulating material 4 placed between the metal case and capacitor element 1; insulating medium (electrically insulating oil) 5 that fills the inside of the metal case to insulate metal case 3 from capacitor element 1; metal lid 6 that seals metal case 3; external lead terminal 7 placed on top of metal lid 6 and used to connect to an external power source; terminal plate 8 made of thermosetting resin or the like and used to insulate metal lid 6 from external lead terminal 7; terminal rod 9 placed below metal lid 6 and electrically connecting lead pieces 2 to external lead terminal 7; and rubber gasket 10 placed below metal lid 6 to insulate metal lid 6 from terminal rod 9 and prevent the insulating medium (electrically insulating oil) 5 from leaking out of the metal case.

[0107] The cable of Figure 2 comprises a conductor 16, a first semiconductive layer 17 arranged around the conductor 16, a layer impregnated with electrical insulating oil 12 arranged on the outside of the first semiconductive layer, a second semiconductive layer arranged on the outside of the layer impregnated with electrical insulating oil 12, a metal screen 14 arranged on the outside of the second semiconductive layer, and a protective sheath 15 arranged on the outside of the metal screen 14.

[0108] As explained above, the electrical insulating base oil of the present invention contains component (A), and therefore has good partial discharge characteristics and environmental friendliness. [Example]

[0109] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples. In these examples, "%" means "% by mass" unless otherwise specified. The raw materials used in this example are as follows:

[0110] <Component (A)> A-1: Dodecyl benzoate and pentadecyl benzoate mixture, manufactured by Sasol (Italy), trade name "COSMACOL EBL".

[0111] <(B) component> B-1: Alkylbenzene (monoalkylbenzene having an alkyl group having 10 to 13 carbon atoms, manufactured by Kanden Engineering, trade name "Sunohm 13A").

[0112] <Component (A'): Comparative component of component (A)> A'-1: Phenylxylylethane (JIS C2320, Type 5, No. 2 insulating oil).

[0113] (Examples 1 and 2, Comparative Example 1) The above (A-1) was used as the electrical insulating base oil of Example 1. In addition, the above components (A) and (B) were mixed according to the composition shown in Table 1 to produce the electrical insulating base oil of Example 2.

[0114] (A'-1) was used as the electrical insulating base oil of Comparative Example 1. The electrical insulating base oil of Comparative Example 1 was produced in the same manner as in Example 1, except that (A'-1) was used instead of (A-1).

[0115] Table 1 shows the composition (compound components, content (mass %)) of the obtained electrical insulating base oil of each example.

[0116] If there is a blank ingredient in the table, that ingredient is not included.

[0117] The electrical insulating base oils of each example were evaluated for partial discharge characteristics (partial discharge inception voltage, partial discharge extinction voltage) as follows. The evaluation results are shown in Table 1.

[0118] The pour point and kinematic viscosity of each electrical insulating base oil were measured as follows. The measurement results are shown in Table 1.

[0119] (Evaluation of partial discharge characteristics) <Evaluation of partial discharge inception voltage> The partial discharge inception voltage of each example of the electrical insulating base oil was measured in accordance with JEC-0401-1990. Specifically, using a partial discharge measuring device (ERA Discharge Detector Model 5 Type 700, manufactured by Robinson Instruments), the voltage at which a partial discharge exceeding a predetermined magnitude (discharge pulse magnitude, occurrence frequency) started (partial discharge inception voltage) when the applied voltage was gradually increased under a predetermined voltage was measured. The measured partial discharge inception voltage of the electrical insulating base oil of Comparative Example 1 (phenylxylylethane: JIS C2320, Type 5, No. 2 insulating oil) was used as the reference (100%), and the relative value of the measured partial discharge inception voltage of each example relative to this measured value was calculated. The relative values ​​were classified according to the following evaluation criteria to evaluate the partial discharge inception voltage of each example of the electrical insulating base oil. AA and A were considered to be acceptable. [Evaluation criteria] AA: 100% or more, A: 95% or more but less than 100% B: Less than 95%.

[0120] <Evaluation of partial discharge extinction voltage> The partial discharge extinction voltage of each example of the electrical insulating base oil was measured in accordance with JEC-0401-1990. Specifically, using a partial discharge measuring device (ERA Discharge Detector Model 5 Type 700, manufactured by Robinson Instruments), the voltage at which partial discharges exceeding a predetermined magnitude (discharge pulse magnitude, occurrence frequency) extinguished when the applied voltage was gradually decreased under a predetermined voltage (partial discharge extinction voltage) was measured. The measured value of the partial discharge inception voltage of the electrical insulating base oil of Comparative Example 1 was set as the reference (100%), and the relative value of the measured partial discharge extinction voltage of the electrical insulating base oil of each example relative to this measured value was calculated. The relative values ​​were classified according to the following evaluation criteria, and the partial discharge extinction voltage of each example of the electrical insulating base oil was evaluated. AAA, AA, and A were considered acceptable. In the evaluation criteria below, B was evaluated as meaning that partial discharge was not extinguished and was not suitable for practical use. [Evaluation criteria] AAA: over 50%, AA: 45%~50%, A: 40% or more but less than 45% B: Less than 40%.

[0121] (Environmental friendliness assessment) The environmental friendliness of each electrical insulating base oil was evaluated based on international chemical substance regulations. Specifically, for each electrical insulating base oil, those that did not contain substances classified as carcinogenic, mutagenic, or reproductively toxic in Annex III of the Regulation on the Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) were evaluated as "Good," and those that contained such substances were evaluated as "Poor." In the case of ○, the product is evaluated as being highly environmentally friendly due to its low burden on people and the environment.

[0122] (Measurement of Pour Point) The pour point of each electrical insulating base oil was measured in accordance with "3. Pour point test method" of JIS K 2269:1987 (Testing methods for pour point and cloud point of crude oil and petroleum products). The pour point of each electrical insulating base oil was classified according to the following evaluation criteria and evaluated. A rating of AA or A indicates that the oil can be used well in cold regions and is highly versatile. [Evaluation criteria] AA: Pour point below -35°C, A: Pour point is -35℃ to -25℃, B: Pour point is above -25°C.

[0123] (Measurement of dynamic viscosity) The kinematic viscosity of each electrical insulating base oil at 40°C was measured using a Cannon-Fenske kinematic viscosity tube in accordance with JIS K2283:2000 (Crude oil and petroleum products - Kinematic viscosity test method and viscosity index calculation method). The kinematic viscosity of each electrical insulating base oil was classified according to the following evaluation criteria and evaluated. A rating of AA or A indicates that a good cooling effect is likely to be obtained for oil-filled electrical equipment. [Evaluation criteria] AA: 4mm 2 / s or less, A: 4mm 2 / s excess 8mm 2 / s or less, B:8mm 2 / s exceeded.

[0124] [Table 1]

[0125] From the results shown in Table 1, it was confirmed that the electrical insulating base oils of Examples 1 and 2 to which the present invention was applied have excellent partial discharge characteristics (partial discharge inception voltage, partial discharge extinction voltage) and are environmentally friendly. Furthermore, the electrical insulating base oil of Example 2 in particular has a low pour point and kinematic viscosity, and is evaluated as being suitable for use in cold regions and having an excellent cooling effect on oil-filled electrical equipment.

[0126] The electrical insulating base oil consisting only of (A'-1) (Comparative Example 1) did not provide sufficient partial discharge characteristics (partial discharge inception voltage, partial discharge extinction voltage) and environmental friendliness.

[0127] From the above results, it was confirmed that the electrical insulating base oil to which the present invention is applied has excellent partial discharge characteristics and is environmentally friendly. [Explanation of symbols]

[0128] 1 Capacitor element 2 reed pieces 3 Metal case 4. Insulation 5. Insulating medium (electrical insulating oil) 6 metal lid 7 External lead terminal 8 Terminal board 9 Terminal bar 10 Rubber packing 11 Insulating plate 12 Electrical insulating oil 13 Second semiconductive layer 14 Metal Screen 15 Protective sheath 16 Conductor 17 First semiconducting layer

Claims

1. An electrically insulating base oil for oil-filled electrical devices, comprising an ester compound (A) represented by the following general formula (I): R １ -COO-R ２ ・・・(I) However, in formula (I), R １ is an aryl group having 6 to 10 carbon atoms or an arylalkyl group having 6 to 10 carbon atoms, and R ２ is a linear hydrocarbon group having 12 or more carbon atoms or a branched hydrocarbon group having 12 or more carbon atoms.

2. In the formula (I), R １ The electrically insulating base oil for oil-filled electrical devices according to claim 1, wherein is an aryl group having 6 to 10 carbon atoms.

3. In the formula (I), R ２ The electrically insulating base oil for oil-filled electrical devices according to claim 1 , wherein is a branched hydrocarbon group having 12 or more carbon atoms.

4. In the formula (I), R ２ The electrically insulating base oil for oil-filled electrical devices according to claim 1, wherein is a branched hydrocarbon group having 12 to 15 carbon atoms.

5. 2. The electrically insulating base oil for oil-filled electrical devices according to claim 1, which contains at least one compound (B) selected from the group consisting of alkylbenzenes, alkylnaphthalenes, diarylalkanes, triarylalkanes, and mineral oils.

6. The electrically insulating base oil for oil-filled electrical devices according to claim 5, wherein the mass ratio of component (A) to component (B) is 90 / 10 to 20 / 80.

7. An electrical insulating oil for oil-filled electrical equipment, comprising the electrical insulating base oil for oil-filled electrical equipment according to any one of claims 1 to 6.

8. An oil-filled electrical device comprising the electrical insulating oil for oil-filled electrical devices according to claim 7.

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