DE2453863A1 - ELECTRIC ISOLATING OIL - Google Patents

Description

Or. Rer. near Horst pupil PATENT ADVOCATE

11.11.1074 Dr.Sch / Ki.

6 Frankfurt / Main 1,
Niddastrasse 52

Telephone (0611) 237220

Telex: 04-16759 mapat d

Telegrams: Mainpatent Frankfurtmain Postscheck-Account: 282420-602 Frankfurt / M.

Bank account: 225/0389

Deutsche Bank AG, Frankfurt / M.

K '1352

Claimed Priority: November 16, 1973, Japan,

No. 128421 Ί973

Applicant: KUREHA KAGAKU KOGYO KABUSHIKI KAISHA No. 8, Horidome-cho
Nihonbashi, Chuo-ku,
Tokyo, Japan

Electrically insulating oil.

The invention relates to a new electrically insulating oil, which has excellent gas absorption property.

So far, a mineral oil is usually produced by refining the lubricant fraction of crude oil the treatment with sulfuric acid and the treatment with alumina has been used as an electrically insulating oil been. When the lubricating oil fraction of the crude oil

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however, subjected to such treatments, so-called sulfuric acid sludge deposition occurs during the sulfuric acid treatment which inevitably requires the disposal of this sulfuric acid sludge deposit. In the In recent years, the discarding of this sulfuric acid sludge deposit has attracted public criticism as it provides a potential cause of pollution. Therefore, it is extremely difficult to remove the sulfuric acid sludge deposit perform. As a result, it has become difficult to get an ample supply of any to ensure electrically insulating oil.

Under these circumstances, a real need arose to create an easily available new electric insulating oil.

It is therefore an object of the invention to provide an advantageous new electrically insulating oil which is excellent Has gas absorption property.

Further objects and features of the present invention will become apparent from the following description of the invention.

In consideration of the above-described circumstances, the inventors have made a study to develop a method to produce a new electrically insulating oil. You found this way that if a mineral oil obtained by hydrogenation refining of the lubricating oil fraction of crude oil with a special alkylnaphthalene is combined, then the resulting mixture has excellent gas absorption property and hence advantageously serves as an electrical, insulating oil.

The invention is based on these findings. Therefore, the invention is characterized in that a mineral oil obtained from hydrogenation refining of the lubricating oil fraction of crude oil with an alkylnaphtha

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! in the general formula:

-En

is combined, where R is an alkyl group having 1 to 4 carbon atoms and η denotes an integer with the value 1 to 4 with the proviso that the total number of carbon atoms in the alkyl group is not less than 3 and in the case where η is an integer of 2 or more, R can be the same or different.

The accompanying drawing is an explanatory diagram that explains the method after in the determination the gas properties of an oil sample using a Thronton apparatus.

The alkyl naphthalenes used for the present invention are those that should be represented by the following general formula:

where R denotes an alkyl group having 1 to 4 carbon atoms and η denotes an integer from 1 to 4 with the proviso that the total number of carbon atoms in the alkyl group is not less than 3, and in the case where η is is an integer with the value 2 or higher, E can be the same or different. From the structural formula it can be seen that any alkylnaphthalene can be used which has one to four alkyl groups (in the presence of two

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or more alkyl groups, these can be the same or different "), selected from the group consisting of methyl, ethyl, propyl and butyl are selected and are bonded to any positions on a naphthalene ring. Such alkylnaphthalenes can can be obtained by separating special fractions of petroleum or coal tar. You can also easily do this obtained that lower olefins with up to four carbon atoms on naphthalene or naphthalene fractions in the presence of a Friede1-Crafts catalyst such as e.g. Aluminum chloride or a solid acid catalyst such as silica-alumina can be reacted to thereby Alkylate naphthalene or naphthalene fractions. Because of their special structure, they have those described above Alkylnaphthalenes numerous isomers. The present invention does not require that these alkylnaphthalenes be pure substances are. They can be mixtures consisting of two or more isomers. For use in the present In accordance with the invention, it is not necessary for the alkynaphthalenes to be in the form of individual compounds, they can also exist in the form of mixtures consisting of two or more different types of alkylnaphthalenes. from the Alkylnahhthalinen in all possible above described Forms prove to be such for the purpose of the invention, both from the standpoint of starting material and synthesis Particularly advantageous alkylnaphthalenes which have one to four propyl groups, such as monopropylnaphthalene, dipropy! Naphthalene, Tripropylnaphthalene and tetrapropylnaphthalene, or the one propyl group in conjunction with other alkyl groups such as methyl propyl naphthalene and dimethyl propyl naphthalene. When the above alkylnaphthalenes are synthesized from naphthalene or naphthalene fractions can be the naphthalene or the naphthalene fractions temporarily subjected to hydrogenation refining treatments so that they are freed from impurities. In this case, some of the naphthalene will be in the starting material converted into tetralin (tetrahydronaphthalene ^, resulting in the Conversion of the naphthalene ring back into the tetraline ring.

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lead is. If the naphthalene, which now contains tetralin, is subsequently subjected to the alkylation, the resultant becomes Alkylnaphthalene inevitably a corresponding alkyltetralin contain. In the present "invention, such an alkylnaphthalene containing an alky! Tetralin, can be used equally effectively.

In contrast, it has been shown that many Mky! Naphthalenes, the fall outside the range of the alky! naphthalenes defined by the general formula given above, for use in the present invention are undesirable from the standpoint of the starting material and the synthesis, since most of them are such that they have low boiling points and high vapor pressures, emit aggressive vapors or have a high degree of viscosity. It should be noted that such alkylnaphthalenes precisely because of these disadvantageous properties in contrast to those that are considered useful for the invention should be excluded.

In the present invention, such an alkylnaphthalene, as described above, combined with a mineral oil obtained by the fact that the crude oil fraction of crude oil has been subjected to hydrogenation refining is. When combining the two ingredients, the mixing ratio is same not particularly critical. However, it is desirable that the alkylnaphthalene be in an amount from 5 to 45 vol. <£, based on the volume of the mineral oil, is used, although the range to which the hydrogenation refining of the lubricating oil fraction of the crude oil is carried out is carried out is more or less variable.

The electrically insulating oil of the present invention obtained as described above is not only excellent in its gas absorption property but also in its resistance to oxidation, as from the preferred ones Embodiments, which are given below, clearly highlight

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goes. Therefore, it is believed that the present invention will make a valuable contribution to the electrical industry and the electrical machine industry supplies.

The present invention will now be explained on the basis of preferred exemplary embodiments described in more detail. It is noted that the invention is not limited to these examples.

example 1

A gas-generating type mineral oil obtained by hydrogenation refining the lubricating oil fraction of crude oil was obtained was mixed with dipropylnaphthalene in the mixing proportions shown in Table 1 are. The mixtures prepared in this way (sample oils) were tested for various properties that are suitable for electrically insulating oil are characteristic. The results are given in Table 1.

From Table 1 it can be seen that the electrically insulating Oil according to the present invention by its gas absorption property and its resistance to oxidation excels.

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Table 1

Test no.

Composition Mineral oil (parts by volume) 100 Composition Dipropy! -Naphthalene ( Vo.T ^ ile) O

60 40

Gas characteristic (in terms of the generation-absorption-pressure difference, cm-oil in the manometer according to type type, leave to stand for 120 minutes) + 65 -12

Physical 15th
Specific weight d. O.P83 0.905 egg properties Flash point ⁰ C 145 140 Pour point C -30 -37.5 Viscosity (at 30 ⁰ C) cst 13.5 12.0 Resistant Acid number mg KOH / g 0.35 0.20 speed against Sludge deposit GewT 0.06 0.04 UAlUdTIUU (in the course of the oxidation educated)

Dielectric properties (80 ° C)

£ (dielectric constant) 2.16

Tg <$ ^ (dielectric V ^ r- 0.02 lustwinkel, tangent)

J) Q. -cm (specific "volume 3x10" resistance)

15th

2.28 0.04

6x10

14th

Dielectric breakdown voltage field strength (kV / 25 mm)

65

80

Note 1: The procedures for determining physical properties, resistance to oxidation, dielectric properties and dielectric breakdown voltage were in Conforms to those specified in JIS C-2320 and related standard procedures are.

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Note 2:

Procedure for determining the gas characteristic:

When an oil in the atmosphere of hydrogen gas an electric When exposed to the field, the oil either generates hydrogen gas or it absorbs hydrogen gas. This behavior, that the oil shows within the electric field is called the "gas characteristic", which is made by means of a Thronton apparatus which is the same as that shown in the accompanying drawing. In the drawing, 1 denotes a container for the sample oil and this container 1 is partially immersed in an oil bath 11 which is equipped with a stirrer 12 is. The container 1 is also provided with an inlet 4 for the sample oil and a glass tap 5. A manometer 3, which is filled with oil and equipped with a glass tap 5 'and a glass tap 6 for adjusting the pressure difference in the manometer is connected to the container 1 via a ball joint 7. With the container 1 are a high voltage electrode 9 and a grounded electrode 10 via a high pressure transformer P. To apply a given sample oil to his To test gas characteristics using this Thronton apparatus, an oil sample 2, in the hydrogen gas beforehand, is tested is dissolved to saturation, introduced into the container 1, which is filled with hydrogen gas. After the temperature the oil sample 2 and that of the oil bath an equilibrium fRO ° C) has reached, the voltage is applied to the high-voltage electrode 0 at the commercially customary frequency. The manometer 3 contains an oil of the quality of rotary vacuum pump oil. If it is shown that the oil sample 2 in its gas characteristics is of the absorption type, the oil level in the right pipe of the pressure gauge rises and the oil level in the left pipe falls proportional. If the oil sample 2 is of the generation type in its gas characteristic, then the difference is in oil levels of the monometer is the reverse of that of an oil of the gas absorption type. The size of the gas generation ability or gas absorption capability of the oil sample 2 can therefore be expressed in terms of the difference between the oil levels in the two tubes of the pressure gauge,

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e.g. in centimeter oil, as indicated under the conditions previously described is observed. In the present example, the atmosphere in which the test passed was performed, from hydrogen gas, from which sample oil were taken 10 ml in volume used and the gradient of the alternating voltage potential was 4 kVmm. The gas characteristic was expressed in values of the difference in the oil levels of the pressure gauge, in cm-oil after 120 minutes of applying the mentioned potential expressed.

Example 2

Fin gas generating type mineral oil obtained by hydrogenation refining the lubricating oil fraction of crude oil was subjected to was mixed with tributylnaphthalene in the mixing proportions shown in Table 2 Similar to Example 1, the resulting Mixtures (sample oils ") based on different properties tests that are characteristic of electrically insulating oil. The results of the test are given in Table 2 below.

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Table 2

Test no.

Mineral oil (parts by volume)

Tributy! -Naphthalene (parts by volume)

100 O

90 10

80 20

Gas characteristics (in values of the pressure difference, cm-oil in the manometer after standing for 120 minutes)

Generation type +25

Absorption type -5

Absorption type -25

Physical Properties

Specific gravity d ^ 0.881

Flash point ⁰ C 145 Pour point ⁰ C -30

Viscosity C at 30 ⁰ C) cst 13.7

O, 8P7 147 -30 16.2

O ₁ POl 14P -27.5 19.4

Resistance to
oxidation

Acid number mg KOH'g 0.30 0.25 0.20

Sludge deposition weight '? 0.06 0.06 0.05

(formed in the course of the

Oxidation)

Dielectric £ (dielectric conical constant)

tg S ⁰ ^ (dielectric loss angle)

DO. -cm (specific volume resistance)

2.16

0.02

3XlO ¹⁵

2.17

0.04

2.19

0.03

2XlO ¹⁵ IxIO ¹⁵

Dielectric Breakdown Voltage Field

thickness (kV ^ S mm) 65 65 68

Example 3

A gas absorption type mineral oil obtained by hydrogenating the lubricating oil fraction of crude oilSr Refining was done using methylpropylnaphthalene mixed in the proportions given in Table 3. Similar to example 1, the

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Mixtures (sample oils ^ on different properties tested, which are characteristic of electrically insulating oil. The results of the test are given in Table 3.

Table 3

Test no.

Mineral oil (parts by volume ^

Methylpropy! -Naphthalene (parts by volume)

100 Away- 90 PO 0 sorp- 10 20th functional Away- away Type sorp- sorp -5 functional ions Type -Type -17 -30

Gas characteristics (in values of the pressure difference cm-oil in the manometer Minutes to stand)

15th

15 Specific weight d

Eigen- S-Ockpunkt ° C shaft _viscosity ( _at 3 ₀ o _C ) cst

0.887 0.800 0.898

145 141 138

-30 -32.5 -35.0

13.3 11.6 10.2

resistance
against
oxidation

Acid number mg KOH 'g

Sludge deposit weight 9 (formed in the course of the oxidation)

0.36 0.35 0.31 0.07 0.07 0, Q6

Dielek- B (dielectric constant) tric _{fg (} j _% (dielectric loss angle)

properties
(80 ° C)

-cm (specific volume resistance)

2.18 2.21 2.24 0.02 0.03 0.03

2xlO ¹⁵ IxIO ¹⁵ 8xlO ¹⁴

Dielectric breakdown voltage field 65 71 76 thickness (kV'25 mm)

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Example 4

The same mineral oil, which is used in Example 2 was consisted with a mixed oil composed of ⁿ O Vol.% Dipropylene! -Naphthalen and 10 vol. <£ Dipropyltetralin, mixed at mixing ratios indicated in Table 4. The resulting mixtures (sample oils) were tested similarly to Example 1 for various properties that are characteristic of electrically insulating oil. The results are given in Table 4.

Table 4
Test-N>. 1 2

Mineral oil (parts by volume 1 100 70

Mixed oil (by volume) O 30

Gas characteristics (in waiting for the pressure dif- erence- absorption cm-b'l in the manometer after 120 minutes of letting it stand) type type

25-15

Physical specific gravity d ¹ ^ 0.881 0.902 see own _o

shafts ^l

Pour point ⁰ C -30 -35

Viscosity (at 30 ° C) cst 13.7 13.1

Resistant - acid number mg KOHVg 0.30 0.19

Sr-hlammablagerung wt.% 0.06 0.05

(formed in the course of oxidation)

Dielectric- £ (dielectric constant ¹ ) 2.16 2.24 see Eigen- _fg £ _% (dielectric loss 0.02 0.03 scnaiTen. _I __- i \

co _n opi angle)

pic! _ _cm (specific volume 3x10 1x10 resistance "^

Dielectric breakdown voltage Ffld- 65 RO thickness (kV / 25 mm)

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Tables 2, 3 and 4 show that the electrical insulating oils according to the present invention in terms of gas absorption property and resistance to Oxidation are excellent.

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Claims (4)

- 14 claims 1. Electrically insulating oil, characterized that it is a mineral oil produced by the hydrogenation refining of the lubricating oil fraction from. Crude oil has been obtained, and an alkylnaphthalene of the general formula -Rn comprises, where R is an alkyl group having 1 to 4 carbon atoms and η denotes an integer with the value 1 to 4 with the proviso that the total number of Carbon atoms in the alkyl group is not lower than 3 and that in the case when η is an integer with the Value is 2 or more, R can be the same or different. 2. Electrically insulating oil according to claim 1, characterized in that the mixing ratio this alkylnaphthalene with the mineral oil is such that the alkylnaphthalene in an amount is incorporated, which is in the range of 5 to 45 vol.% lies. 3. Electrically insulating oil according to claim 1 or 2, characterized in that the Alkylnaphthalene is a mixture of isomers of the same. 4. Electrically insulating oil according to one of claims 1 to 3, characterized in that the alkylnaphthalene in the form of a mixture of two or more alkylnaphthalenes is used. 509822/0645