JPS58155603A - Electrically insulating oil - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present application relates to an electrical insulating oil whose main raw material is graphine base crude oil or mixed base crude oil.

More specifically, the distillate oil with a boiling point (normal pressure equivalent) of 230 to 430°C obtained by distilling paraffin base crude oil or mixed base crude oil is subjected to solvent refining or hydrorefining treatment, or solvent refining and hydrogenation treatment, and Adding 3 to 50 wt% of an aryl alkane and an amorphous ethylene-propylene copolymer o, ooi to 0.5 vt% to mineral oil with a sulfur content of 0.35 vt% or less obtained by solvent dewaxing treatment. This invention relates to an electrical insulating oil that is characterized by excellent thermal stability, copper plate discoloration resistance, electrical properties, low-temperature performance, and corona resistance.

Today, various types of insulating oils are on the market, but the majority of them in terms of quantity are mineral oil-based insulating oils. The reason for this is that compared to the insulating oil obtained by the Taninari method, mineral oil-based insulating oil uses petroleum fraction as the main raw material and can therefore be supplied in large quantities at relatively low cost. Synthetic insulating oils are expensive/6''% and limited to special applications.

However, conventionally, this mineral oil-based insulating oil is not a product that can be produced from any crude oil without much difference, such as gasoline or kerosene. In producing mineral oil-based insulating oil, the choice of crude oil is actually the most important. That is, there is a practical need for a naphthenic crude oil whose specific gravity, flash point, and viscosity are within certain ranges, and whose freezing point is generally low and whose sulfur content is low.

On the other hand, recently, small and medium-sized transformers have become smaller and lighter, so the operating temperature is 10°C higher than the conventional operating temperature.
Crise transformers have been designed, requiring insulating materials that can adequately withstand these temperatures. Conventional insulating paper and naphthenic mineral oil alone do not have sufficient service life under these conditions. In addition, in recent years, capacitors, cables, transformers, and circuit breakers are sufficiently degassed when filling with oil, and even after filling, measures such as diaphragm type or nitrogen filling are taken, so the presence of oxygen is extremely low. There are many. Therefore, in addition to oxidation stability, which has traditionally been considered important, it is widely desired to evaluate the quality of oil based on changes in tan δ during thermal deterioration, that is, insulating oils with excellent thermal stability.

The present inventors conducted research on the amount of lead with the aim of obtaining this insulating oil with excellent thermal stability at a relatively low cost and in multiple quantities. It has been found that an insulating oil containing a predetermined amount of synthetic oil such as an aryl alkane and an amorphous ethylene-propylene copolymer is extremely superior to a fraction purified from a mixed base crude oil by a predetermined method.

On the other hand, since the recent so-called oil crisis, it has become extremely difficult to obtain naphthenic crude oil, which has limited origins and is only produced in small quantities. As the present invention makes clear, it is of great interest to obtain superior electrical insulating oils from paraffinic or mixed base crude oils.

As mentioned above, an insulating oil in which hydrogen gas absorption is improved by mixing alkylbenzene or the like with naphthenic mineral oil is already known (US Pat. No. 3,036,010). However, as shown in Comparative Examples below, products using naphthenic mineral oil as the main raw material do not have sufficient performance in terms of thermal stability.

Furthermore, it is already known that synthetic oils such as alkylbenzene can be used alone as electrical insulating oils (Journal of the Japan Petroleum Institute, Vol. 17, No. 7 (1974)), but they are extremely poor in terms of oxidation stability. Not only are these synthetic oils used in specific insulating oils such as cable oil and cable oil, but these synthetic oils are also very expensive and often difficult to supply in large quantities, making them relatively inexpensive. It is necessary to obtain electrical insulating oil that can be supplied in large quantities.

The present invention provides a method for producing electrical insulating oil using paraffin base crude oil or mixed base oil as raw material oil, in which an aryl alkane and an amorphous ethylene-propylene copolymer are mixed to improve thermal stability and high temperature stability. We have discovered that we can produce a product that is superior to conventional naphthenic insulating oils in terms of low-temperature properties and low-temperature properties, and that it is also possible to produce a product that is equivalent to conventional naphthenic oils in terms of corona resistance. It is something that

The present invention will be explained in more detail below.

The I4 rough-in base crude oil referred to in the present invention is a crude oil containing a large amount of 45-fin hydrocarbons, and is referred to in "Petroleum Handbook J 1.
As described on page 19 (published by JIC Sekiyu Shunjusha in 1972), AieI of the first key fraction of crude oil (kerosene fraction)
Philippine Army-fi4G” or above, 2nd key fraction (273-3
Typical examples of lubricating oil fraction (00° C., 740 M, %llF) with an API specific gravity of 3e0 or higher include Pencil Pair crude oil and Minas crude oil. It is located between the mixed base crude oil, Hasu 7 base crude oil, and Gurahui base crude oil, and is the first key fraction! The specific gravity is 33 to 4 @', and the second key fraction has a muPI specific gravity of 20 to 30', and it is mostly found in electric, continental crude, Arabian crude, and Middle Eastern crude oil of 7 liters of oil. Be looked at. To this invention? In particular, Arabian crude oil such as Arabian medium Arabian medium is preferably used.

In the present invention, the d rough-in base material is prepared by distilling a mixed base crude oil at normal pressure or by distilling a residual oil from atmospheric distillation under reduced pressure to a boiling point (converted to normal pressure) of 230 to 430°C. The contained distillate oil is treated with a solvent that selectively dissolves aromatic compounds. The solvent used here that selectively dissolves aromatic compounds is commonly used, and specifically, furfural, liquid sulfur dioxide, phenol, etc. are used. In the present invention, furfural is particularly suitable, and when furfural is used, the extraction temperature is usually 50 to 100°C,
The temperature is preferably 60-90°C, and the ratio of furfural to mineral oil is about 0.3. It is used in a range of vol, /vol or more, preferably 0.5 vol, /vol or more.

In addition, in the present invention, mineral oil obtained by subjecting the aforementioned fraction to catalytic hydrorefining can also be used. Catalysts used in hydrorefining are oxides of metals from Groups 1, 1B, and 2 of the periodic table, using dexide, activated carbon, Fuller's earth, diatomaceous earth, zeolite, silica, silica alumina, etc. as carriers. It is usually used after pre-sulfurization. Specific examples of these oxides include cobalt oxide,
Examples include molybdenum oxide, tungsten oxide, and nickel oxide. In the present invention, a presulfurized catalyst consisting of nickel oxide and molybdenum oxide supported on an aluminum oxide-containing carrier is particularly preferably used. The reaction temperature in the hydrorefining treatment of the present invention is usually about 230 to about 350°C. At low temperatures, the reaction rate is low, and at high temperatures, pi + rough-in increases due to Par-L decomposition, resulting in a slight rise in pour point and unfavorable color of the product.

The reaction pressure is 25 kg/cm2 or more, preferably 25~
100 Yu/cm”, most preferably 35-45 Yu/(7
)2. Also, hydrogen is 10% for feedstock oil I Kt.
0 to 10.00 ONm”, preferably 200 to 1,
Contact is made within the range of 00ONm3.

In the present invention, as described above, a purification method using only solvent refining or only hydrorefining can be adopted, but it is preferable to perform solvent refining and hydrorefining in order to improve thermal stability. preferable. In this case, 30 to 85 wt% is usually preferable for solvent purification.
% desulfurization rate. Although the order of solvent purification and hydrotreating is not particularly limited, it is particularly preferable to hydrotreat solvent-purified sifinate.

In the present invention, the mineral oil is subjected to a solvent film wax treatment. The solvent film wax used in the present invention solidifies and removes the wax content in oil by a known method, and the commonly used method is B.
This is the K method. The solvent used is habenzene, toluene, acetone t* is 1'! It is a mixed solvent of toluene, methyl ethyl ketone, etc. The composition of the solvent (ratio of Kent content to aromatic content) is 30-35% in the case of acetone and methyl ethyl ketone. The solvent ratio can be determined by adding a solvent so that the viscosity of the solution supplied to the dewaxing filter is approximately constant.

The order of the solvent membrane waxing treatment in the present invention can be carried out at any stage before or after the solvent refining treatment and/or hydrorefining treatment, but it is preferably performed in order to further increase the dewaxing efficiency. Performed after solvent toning and/or hydrorefining treatment.

In the present invention, the purified mineral oil is subjected to solid adsorbent treatment if necessary. The solid adsorbent treatment mentioned here refers to acid clay, activated clay, Fuller's earth, alumina,
A solid adsorbent such as silica-alcohol and mineral oil are usually used
Process II refers to contact at 80°C. This adsorbent treatment further improves properties such as thermal stability and electrical properties.

In the present application, the sulfur content in the mineral oil fraction is reduced to 0. 35 wt% or less, preferably 0. 0 1 = 0. 2 It is necessary to use vt9G.

If the sulfur content is high, the steel plate's discoloration resistance (corrosion resistance) will be poor, that is, it will have an adverse effect on the steel blackening phenomenon inside the insulating oil container.

Furthermore, the aryl alkanes referred to in the present invention are as follows. That is, an alkylbenzene represented by the following general formula, where R1% R2 is hydrogen or a hydrocarbon residue having 1 to 20 carbon atoms, and the total number of carbon atoms in R1 and R2 is 9 or more, preferably 12 to 20. 28. If the total number of carbon atoms is less than 9, the flash point, evaporation test, and other properties will deteriorate, which is disadvantageous. The hydrocarbon residues of R1 and R2 may be either linear or branched. These alkylbenzenes may contain up to about 50% by weight of tetralin, indene, indane, or their hydrocarbon derivatives. These alkylbenzenes are usually composed of benzene and olefins or benzene and halogenated/F-roughin. It is obtained by condensing (alkylating) these compounds in the presence of an acid catalyst such as a Friedel-Krach type catalyst. Industrially, monoalkylbenzenes having 9 to 16 carbon atoms obtained when synthesizing linear or branched alkylbenzenes for detergents, or heavy alkylbenzenes produced as by-products when synthesizing these,
Kettle residual oil (detergent alkylbenzene removed by distillation,
Residue oil) etc. are preferably used. These aryl alkanes are preferably treated with a solid adsorbent before use. Furthermore, it is generally preferable for these aryl alkanes to have good electrical properties when used after being subjected to hydrogenation treatment. In this case, the catalyst used for the hydrogenation treatment is one or more of metals, metal oxides, and metal sulfides of Groups I, II, and II of the Periodic Table.
Those in which the seeds or more are supported on a solid carrier such as silica, alumina, diatomaceous earth, or activated carbon are preferably used. Specifically, it is supported or not supported on the above carrier.
f) Catalysts such as aluminum, platinum, nickel, copper-chromium, cobalt-molybdenum, nickel-molybdenum, nickel-tungsten can be preferably applied. Hydrogenation reaction conditions are pressure, usually 2 to 50 kg/cm2G.
, temperature 50-400°C, liquid hourly space velocity 1-15 vol,
/ vol, go; get it.

In addition, when using linear heavy alkylbenzene with a boiling point of about 300°C or higher as the aryl alkane, it is hydrogenated under conditions that selectively hydrogenate only the alkyl polycyclic aromatic group contained as an impurity. Wavelength 400m
It is particularly preferable to use one having an absorbance of μ of 0.4×10””1/L-on or less.

In the present invention, the above-mentioned aryl alkane is added in an amount of 3 to 50 wt % to the mineral oil obtained by refining a predetermined fraction from the above-described paraffin base crude oil or mixed base crude oil. If the amount added is less than 3 wt, properties such as thermal stability and hydrogen gas absorption will not be sufficient, and if the amount added is less than 3 wt
% or more is not only unlikely to improve thermal stability, hydrogen gas absorption, etc., but is also expensive and uneconomical.

In addition, in the present invention, mineral oil obtained by refining a predetermined fraction from the above-mentioned rough-in base crude oil or mixed base crude oil is processed into the above-mentioned arylalkane to produce an amorphous ethylene-propylene copolymer. 0001~0.5wt
%.

The amorphous ethylene-propylene copolymer mentioned here is usually oil-soluble and has a weight average molecular weight of 10,000 to 200.0.
00 preferably 20,000-70,000, usually propylene content 10-70 mot% preferably 20-70
60 mol%. The term "amorphous" as used herein means that the copolymer may have a certain degree of crystallinity, and usually has a crystallinity of 0 to 5%, preferably 0 to 2. Furthermore, the molecular weight distribution is preferably relatively narrow, and generally 8 or less, particularly 4 or less, is suitable for the purpose of the present invention.

These ethylene-propylene copolymers can be obtained by known specific methods. Polymerization is carried out by mixing a specific homogeneous Ziegler-Natsuta catalyst that is soluble in organic solvents in an inert organic solvent, and adding ethylene, propylene, and hydrogen gas under conditions of normal pressure or slightly increased pressure and room temperature or slightly high temperature. This is done by introducing it into the catalyst mixture. Ethylene and propylene have different polymerization reaction rates, and the polymerization reaction rate of ethylene is much higher than that of zoropylene.

Therefore, the monomer ratio of ethylene and zolopylene does not match the content of ethylene and propylene in the produced copolymer. Therefore, it is necessary to pay sufficient attention to the monomer ratio of ethylene and propylene in order to obtain an ethylene-propylene copolymer with the desired propylene content.

Homogeneous Ziegler-Natsuta type catalysts for obtaining the specific ethylene-propylene copolymer used in the present invention have the general formulas vOX3 and VO(OR)nXs-n.
(However, X is chlorine, bromine, or iodine, and R has 1 to 1 carbon atoms.
6 hydrocarbon residue, n is an integer from 1 to 3) and the general formula R2AtX.

Coordination catalysts consisting of organoaluminum halides represented by RAjX, RA7X2 and R3At2X3 are preferred. During polymerization, the inert organic solvent used is usually an aliphatic or aromatic hydrocarbon. concrete K
Tri n-hexane, hezotane, toluene, xylene, etc. are preferably used.

When the amorphous ethylene-propylene copolymer referred to here alone is added to mineral oil that has been subjected to the specified refining process referred to in this application, its pour point will drop to some extent, but when both the copolymers are added in specified amounts to the arylalkane referred to in this application, the pour point will drop to some extent. Surprisingly, the inventors of the present invention have found that when added, the pour point drops significantly compared to when each is added alone. This significant drop is particularly noticeable when the mineral oil has a relatively wide boiling range of about 80°C or higher.

Although it is not strictly clear why the supporting point decreases synergistically by adding both of these, they simultaneously exert a special effect in conjunction with each other during the precipitation of wax crystals in mineral oil. It seems that it will.

Furthermore, even if a predetermined amount of the ethylene-propylene copolymer mentioned here is added, the thermal stability of the insulating oil consisting of the predetermined mineral oil and aryl alkane referred to in the specified invention of the present application,
It does not have any adverse effect on electrical characteristics, etc.

If the amount of ethylene/propylene added is less than 0,001wt, it will not be very effective in lowering the pour point;
Adding more than 5 wt% is not economically disadvantageous since no drop in the pour point is observed, and it also has an adverse effect on properties such as electrical properties and thermal stability. ~Next, the present invention will be explained in more detail with reference to some examples.

Example 1 and Comparative Example 1 Distillate oil obtained by distilling Middle Eastern (mixed base) crude oil at atmospheric pressure and then distilling the residual oil under reduced pressure (boiling point 250-3 in terms of atmospheric pressure)
80°C, sulfur content 1.7 wt%) was collected. Next, add this distillate to a solvent ratio (furfural/distillate) of 1.
3. Furfural was extracted at an extraction temperature of 75 to 90°C to obtain a raffinate with a sulfur content of 0.8 wt%. (Desulfurization rate 5
6 wt%). Furthermore, this raffinate was treated with a Nip-Mob3 catalyst (NiO: 3.Ow) using alumina as a carrier.
t%, MOO3: 14.0wt%) at 300°C
, after hydrorefining treatment at a hydrogen pressure of 40 kg/cm2,
Dewaxing was carried out using benzene, toluene, and methyl ethyl ketone as solvents at a solvent ratio (solvent/oil) of 16 and a cooling temperature of -30°C to obtain a mixed base refined mineral oil.

On the other hand, a heavy alkylbenzene with a boiling point of about 310 to 404°C, which is obtained as a by-product when synthesizing a branched alkylbenzene for detergents by reacting propylene tetramer as the main component, sulolefin, and benzene with a boron catalyst, is wt% and weight average molecular weight 180,00
5 wt% of amorphous ethylene-propylene copolymer Q having a propylene content of 30 moles was added to the above mixed base refined mineral oil to obtain an insulating oil, and various properties were measured. The results are shown in Table 1. As is clear from Table 1, even if the copolymer alone or the alkylbenzene alone is added to mixed base refined mineral oil, the pour point decreases to some extent, but when both are added at the same time, A very significant drop in pour point occurs. Of course, other properties such as thermal stability and electrical properties are not degraded. The degree of pour point depression is much greater than that expected from the degree of depression when each of these is added singly.

Such a low pour point insulating oil is suitable for extremely cold rolling.

Claims (1)

[Scope of Claims] ・Solvent refining or hydrorefining treatment, or solvent refining of distillate oil with a boiling point (normal pressure equivalent) of 230 to 430°C obtained by distilling mother fin base crude oil or mixed base crude oil The sulfur content obtained by hydrogenation treatment and solvent waxing treatment was 0. Copolymerization of 3 to 50 wt% aryl alkane and amorphous ethylenezolopyrene using mineral oil of up to 35 wt% as base oil. An electrical insulating oil that contains 0.001 to 0.5 wt% of phosphorus and has excellent thermal stability, resistance to discoloration of copper plates, electrical properties, low temperature performance, and corona resistance.