JPWO2006040888A1 - Electrical insulation oil - Google Patents

Abstract

The present invention provides an electrical insulating oil that is excellent in biodegradability, has low viscosity at low temperatures, has little deterioration in insulation performance even when mixed with some moisture, and has sufficient electrical properties. Is mainly composed of an ester consisting of neopentyl glycol and at least one linear or branched carboxylic acid having 7 to 10 carbon atoms, a kinematic viscosity at 0 ° C. of 10 to 200 mm 2 / s, and a dielectric breakdown voltage of 30 kV. Thus, an electrical insulating oil having a biodegradability of 60% or more and a pour point of −30 ° C. or less is provided.

Description

  The present invention relates to an electrical insulating oil excellent in electrical characteristics and biodegradability.

  As the electrical insulating oil, various kinds such as refined mineral oil, alkylbenzene, alkylnaphthalene, silicone oil and ester oil are used. Recently, emphasis has been placed on environmental problems, in particular, biodegradability of leaked insulating oil, and insulating oils composed of fatty acid esters formed by transesterification of rapeseed oil and isobutyl alcohol have also been proposed (Japanese Patent Laid-Open No. 2000-90740). No. publication). In addition, an electrical insulating oil mainly composed of an ester composed of trimethylolpropane and / or pentaerythritol and a specific fatty acid has been proposed (see Japanese Patent Application Laid-Open No. 2004-273291).

  By the way, in the natural circulation cooling transformers that do not have a circulation pump, such as power distribution pole transformers, insulation is achieved even with low viscosity at low temperatures and some water contamination in addition to the biodegradability and normal insulation performance. There is a demand for a small decrease in performance.

  The electrical insulating oil comprising the rapeseed oil ester is not satisfactory in terms of pour point and viscosity at low temperature, and various commercially available electrical insulating oils also have electrical characteristics, pour point, viscosity at low temperature and There are problems with any of the biodegradability, and few have been found that satisfy all of these.

  The present invention solves the above problems, and provides an electrical insulating oil that has excellent biodegradability, low viscosity at low temperature, little deterioration in insulation performance even when mixed with some moisture, and sufficient electrical properties. The purpose is to do.

The present invention
(1) The main component is an ester composed of neopentyl glycol and one or more of linear or branched carboxylic acid having 7 to 10 carbon atoms, kinematic viscosity at 0 ° C. is 10 to 200 mm ² / s, and dielectric breakdown voltage is An electrical insulating oil of 30 kV or higher, biodegradability of 60% or higher, and a pour point of −30 ° C. or lower;
(2) The ester is composed of neopentyl glycol, n-heptanoic acid, n-octanoic acid, n-nonanoic acid, n-decanoic acid, 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid. The electrical insulating oil according to (1) above, which contains at least one ester;
(3) The electrical insulating oil according to (1) above, wherein the ester contains 5 mol% or more of one or more esters of neopentyl glycol and a branched carboxylic acid having 8 or 9 carbon atoms,
(4) The electrical insulating oil as described in (3) above, wherein the ester contains 5 to 100 mol% of an ester of neopentyl glycol and 2-ethylhexanoic acid,
(5) 1% by mass of any one or more of phenolic compounds and / or amine compounds as antioxidants, triazole compounds as antistatic agents, and carbodiimides and / or epoxy compounds as hydrolysis inhibitors The electrical insulating oil according to (1) above, which is added below,
It depends on.

  Since the electrical insulating oil of the present invention is excellent in biodegradability, it is rapidly decomposed by microorganisms even if it leaks, and the load on the natural environment is small. The natural circulation cooling function can be exerted, and even if some moisture such as rainwater is mixed, the insulation performance is hardly lowered, and it has sufficient electrical properties and excellent practical performance.

  An ester composed of neopentyl glycol, which is the main component of the electrical insulating oil of the present invention, and one or more of linear or branched carboxylic acids having 7 to 10 carbon atoms is a non-catalyst of the glycol and carboxylic acid, or sulfuric acid, In the presence of a strong acid catalyst such as an alkylsulfonic acid or a metal chloride catalyst such as tin chloride or titanium chloride, it can be produced by esterification by a conventional method. Moreover, the obtained ester is good to refine | purify by a series of processes, such as deoxidation, water washing, dehydration, decoloring, and filtration similarly to the case where the normal ester is refine | purified.

  In addition, the electrical insulating oil of the present invention uses the above-mentioned glycol and each carboxylic acid separately esterified separately, appropriately mixed, so-called physical mixing, and having a predetermined property Alternatively, what is obtained by so-called chemical mixing in which two or more kinds of carboxylic acids are appropriately blended in advance so as to have predetermined properties and esterified with the glycol may be used.

  As described above, by using an ester obtained by physical mixing or chemical mixing with the above two or more kinds of carboxylic acids as a base material, it is possible to satisfy various properties required as an electrical insulating oil in a well-balanced manner.

  The ester according to the present invention may be a partial ester in which some of the hydroxyl groups of neopentyl glycol remain without being esterified, but all the hydroxyl groups of the alcohol (glycol) are esterified. Preferably there is. Specifically, the hydroxyl value of the ester is preferably 50 mgKOH / g or less, particularly preferably 10 mgKOH / g or less.

  In addition, the linear or branched carboxylic acid having 7 to 10 carbon atoms is represented by R-COOH, has one carboxyl group, and R is a linear or branched alkyl group having 6 to 9 carbon atoms. In particular, n-heptanoic acid, n-octanoic acid, n-nonanoic acid, n-decanoic acid, 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid are preferred. Further, as the carboxylic acid, a branched carboxylic acid having 8 or 9 carbon atoms is more preferable. Specifically, 2-ethylhexanoic acid or 3,5,5-trimethylhexanoic acid is preferably used. The acid is preferably 5 mol% or more, particularly 15 mol% or more, more preferably 25 mol% or more in the total carboxylic acid. In particular, 2-ethylhexanoic acid is preferably used as the carboxylic acid so as to be 5 to 100 mol%, particularly 15 to 100 mol%, and more preferably 50 to 100 mol% in the total carboxylic acid.

  The ester may be contained as a main component of the base oil, but in particular, from the point of satisfying all required performances such as viscosity at low temperature, pour point, biodegradability and electrical properties more reliably and in a balanced manner. The ester is preferably contained in an amount of 50% by mass or more based on the total amount of the base oil, more preferably 80% by mass or more, and even more preferably 90% by mass or more. Most preferably, it is 100 mass%.

  As the base oil of the electrical insulating oil of the present invention, in addition to the above ester, hydrocarbon oils such as mineral oil, olefin polymer, alkylbenzene, polyglycol, polyvinyl ether, ketone, polyphenyl ether, silicone, polysiloxane, Oxygen-containing synthetic oils such as perfluoroether, esters other than the above esters, and ethers may be used.

Electrical insulating oil of the present invention has a kinematic viscosity at 0 ℃ is required to be in the range of 10 to 200 mm ² / s, is less than 10 mm ² / s, poor flame resistance flash point is lowered, also 200 mm ² If it exceeds / s, the circulation of the insulating oil in the transformer becomes insufficient, cooling becomes incomplete and causes heating. The kinematic viscosity at 0 ° C. is preferably in the range of 10 to 100 mm ² / s, particularly 10 to 50 mm ² / s.

  Further, the electrical insulating oil of the present invention needs to have a biodegradability of 60% or more and preferably a biodegradability of 85% or more in order to reduce the influence on the natural environment. . In addition, this biodegradability is a thing after 28 days measured by the method prescribed | regulated to OECD 301B.

  Furthermore, the electrical insulating oil of the present invention has a pour point of −30 ° C. or lower. Unless the pour point of the electrical insulating oil is −30 ° C. or lower, it cannot withstand use in cold regions. Further, in order to ensure excellent electrical characteristics of the electrical insulating oil, the dielectric breakdown voltage according to JIS C 2101 needs to be 30 kV or higher, and is preferably 50 kV or higher. Further, the electrical insulating oil of the present invention preferably has a dielectric loss tangent (80 ° C.) according to JIS C 2101 of 5% or less, particularly 2% or less. Furthermore, the electrical insulating oil of the present invention preferably has a total acid value of 0.1 mgKOH / g or less in order to ensure good stability.

  Since the base oil mainly composed of ester has a high dielectric constant close to that of insulating paper as compared with a mineral oil-based base oil, the transformer can be miniaturized. In addition, since the base oil mainly composed of ester has a high saturated water content, the dielectric breakdown voltage can be maintained at 30 kV or higher even when the water concentration becomes 500 ppm.

  In the electrical insulating oil of the present invention, a phenolic compound and / or an amine compound as an antioxidant, a carbodiimide and / or an epoxy compound as a hydrolysis inhibitor, and a charge are added to the base oil mainly composed of the ester. It is preferable to add at least 1 mass percent of each of the triazole compounds as the inhibitor.

  Examples of the phenol compound and amine compound as the antioxidant include di-tert-butyl-p-cresol, 4,4′-methylene-bis- (2,6-di-tert-butylphenol), bisphenol A, Examples thereof include phenyl-α-naphthylamine, N, N-di (2-naphthyl) -p-phenylenediamine, dioctyldiphenylamine and the like. Examples of the triazole compound as the antistatic agent include benzotriazole, benzotriazole derivatives, and thiadiazole. Further, as the carbodiimide as the hydrolysis inhibitor, diphenylcarbodiimide, ditolylcarbodiimide, bis (isopropylphenyl) carbodiimide, bis (diisopropylphenyl) carbodiimide, bis (triisopropylphenyl) carbodiimide, bis (butylphenyl) carbodiimide, etc. Bis (alkylphenyl) carbodiimide and the like, and epoxy compounds as the hydrolysis inhibitor include phenyl glycidyl ether, phenyl glycidyl ester, alkyl glycidyl ether having 5 to 18 carbon atoms, alkyl glycidyl having 5 to 18 carbon atoms. Examples include esters.

  One or more of these antioxidants, hydrolysis inhibitors and antistatic agents may be added depending on the individual required performance. The addition amount should be 1% by mass or less for each additive based on the total mass of the electrical insulating oil. If it exceeds 1% by mass, sludge generation and coloring at the time of deterioration occur. In particular, for antioxidants and hydrolysis inhibitors, 0.05 to 1% by mass, especially 0.1 to 0.5% by mass, and for antistatic agents, 5 to 1000 ppm, in particular 5 to 50 ppm added. It is preferable to do.

  In addition to the above additives, the electrical insulating oil of the present invention includes an anti-wear agent such as zinc dithiophosphate, an extreme pressure agent such as a sulfur compound, a viscosity index improver, a pour point depressant, a cleaning dispersant, a metal dispersant. Additives such as an activator can be added alone or in combination. The addition amount of these additives is not particularly limited, but is preferably 1% by mass or less based on the total amount of the electrical insulating oil.

<Example>
Hereinafter, the present invention will be described in more detail based on examples. In addition, this invention is not restrict | limited at all by the following examples.

(Example 1)
Neopentyl glycol (NPG) is used as alcohol, n-heptanoic acid (nC7), n-octanoic acid (nC8), n-nonanoic acid (nC9), n-decanoic acid (nC10), 2-ethyl as carboxylic acid Hexanoic acid (bC8), 3,5,5-trimethylhexanoic acid (bC9), n-butanoic acid (nC4), n-dodecanoic acid (nC12) were used, and for comparison, trimethylolpropane (alcohol) Using TMP) or pentaerythritol (PE), esters were prepared at the ratios shown in Table 1 to obtain test oils. The ester using two or more kinds of carboxylic acids is prepared by chemical mixing, that is, by mixing carboxylic acids at a predetermined ratio and esterifying them with alcohol.

About the said test oil, each physical property was measured and the practical performance was evaluated. The physical property measurement and the performance evaluation test were performed by the following methods. These results are shown in Table 2.
(1) Kinematic viscosity: measured at 0 ° C. by the method specified in JIS K 2283.
(2) Biodegradability: Measured by the method defined in OECD 301B (after 28 days).
(3) Pour point: Measured by the method defined in JIS K 2269.
(4) Total acid value: measured by the method defined in JIS K 2514.
(5) Dielectric breakdown voltage: measured by the method specified in JIS C 2101.
(6) Dielectric loss tangent: Measured at 80 ° C. by the method defined in JIS C 2101.
(7) Flash point: Measured by the method defined in JIS K 2265 (Cleveland open type).

  From Table 2, the test oils 1 to 7 according to the present invention have good kinematic viscosity, biodegradability, low temperature fluidity, combustibility, and thermal stability, and are well balanced as the performance of the electrical insulating oil. On the other hand, sample oil 8 for comparison has a low kinematic viscosity and flash point, sample oil 9 has a too high pour point, sample oil 10 has a high kinematic viscosity, and low biodegradability. The test oil 11 has low biodegradability, the test oils 12 and 13 have a high pour point, low biodegradability, and the test oil 14 has a high pour point, both of which are inferior as electrical insulating oils.

(Example 2)
To the sample oil 6, 2,6-di-t-butyl-p-cresol (DBPC) or phenyl-α-naphthylamine (PNA) as an antioxidant, benzotriazole (BTA) as an antistatic agent, water As a decomposition inhibitor, bis (butylphenyl) carbodiimide (BBPC) or phenylglycidyl ether (PGE) was added in the amounts shown in Table 3 on the basis of the total sample oil mass.

  About this, the oxidation stability test (120 degreeC and 75 hours by the method prescribed | regulated to JIS C2101) was done. The results are shown in Table 3.

  From this result, it is understood that the oxidation stability can be improved by adding an antioxidant, an antistatic agent, a hydrolysis inhibitor or the like.

  The electrical insulating oil of the present invention is excellent in biodegradability, low viscosity at low temperature, small deterioration in insulation performance even if some moisture is mixed in, and has sufficient electrical properties. Although it is extremely useful as an electrical insulating oil for a pole transformer, it is also useful as an insulating oil for various electrical devices such as other transformers, cables, capacitors, circuit breakers and the like.

Claims (5)

The main component is an ester composed of neopentyl glycol and one or more of linear or branched carboxylic acids having 7 to 10 carbon atoms, kinematic viscosity at 0 ° C. of 10 to 200 mm ² / s, dielectric breakdown voltage of 30 kV or more, An electrical insulating oil having a decomposability of 60% or more and a pour point of -30 ° C or less.   The ester is neopentyl glycol and at least one of n-heptanoic acid, n-octanoic acid, n-nonanoic acid, n-decanoic acid, 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid. The electrical insulating oil according to claim 1, comprising an ester thereof.   2. The electrical insulating oil according to claim 1, wherein the ester contains 5 mol% or more of one or more esters of neopentyl glycol and a branched carboxylic acid having 8 or 9 carbon atoms.   The electrical insulating oil according to claim 3, wherein the ester contains 5 to 100 mol% of an ester of neopentyl glycol and 2-ethylhexanoic acid.   1 mass% or less of any one or more of phenolic compounds and / or amine compounds as antioxidants, triazole compounds as antistatic agents, and carbodiimides and / or epoxy compounds as hydrolysis inhibitors are added. The electrical insulating oil according to claim 1, wherein: