JP2514058B2 - Method for producing novel electrical insulating oil composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an electrically insulating oil composition which is excellent in low-temperature characteristics and contains substantially no chlorine.

[Prior Art and its Problems] In German Laid-Open Patent No. 3127805, an electrically insulating oil composition comprising alkylated diphenylmethane is obtained by reacting toluene and benzyl chloride in the presence of an aluminum chloride catalyst. It is disclosed. The electric insulating oil obtained here has excellent low-temperature characteristics, but since benzyl chloride is used as the starting material for the electric insulating oil, a large amount of chlorine easily enters the obtained electric insulating oil composition. When the insulating oil contains a large amount of chlorine, the oxidative stability of the electric insulating oil is reduced. Alternatively, chlorine may be generated from the insulating oil under high voltage, and this may corrode the element of the container of insulating oil or the container itself. Furthermore, there is a concern that the generated chlorine gas reacts with the insulating oil to generate chlorinated aromatic hydrocarbons, which are generally recognized as highly toxic.

Therefore, in the insulating oil, especially the insulating oil composed of aromatic hydrocarbons, the mixing of chlorine must be strictly controlled. However, as described above, the insulating oil composition described in the West German Patent has a drawback that chlorine cannot be mixed in.

The above-mentioned publication proposes to add an oxidation stabilizer such as a hydroquinone derivative or an acid acceptor in order to prevent such harmful effects of chlorine. Of course, such a method is not a fundamental solution.

[Structure of the Invention] That is, the present invention provides toluene and diphenylmethane or benzyltoluene produced without using a chlorinated hydrocarbon as a starting material in the presence of a disproportionation catalyst,
A reaction product containing benzyltoluene and ditolylmethane is obtained by reacting at -10 to 550 ° C, and then benzyltoluene 20 to 80, which comprises recovering benzyltoluene and ditolylmethane by distillation from the reaction product. % And 80% to 20% of ditolyl methane, and a method for producing an electric insulating oil composition, which is substantially free of chlorine and has excellent low temperature characteristics. To do.

 The present invention will be described in more detail below.

The disproportionation catalyst used in the present invention is any catalyst capable of producing benzyltoluene and ditolylmethane from toluene and diphenylmethane, and ditolylmethane from toluene and benzyltoluene, as long as they can be produced by a disproportionation reaction. Can also be used.

For example, Lewis acid such as aluminum chloride, silica
Solid acids such as alumina, heteropoly acids such as silicotungstic acid, super strong acids such as trifluoromethane sulfonic acid, super strong acid cation exchange resins such as perfluorosulfonic acid resin (trade name: Nafion, manufactured by DuPont), etc. It may be mentioned as the disproportionation catalyst of the present invention.

The temperature of the disproportionation reaction is -10 depending on the type of disproportionation catalyst.
It can be selected from a wide temperature range of ~ 550 ° C, preferably 20-500 ° C.

At a temperature lower than -10 ° C, the disproportionation reaction is difficult to proceed, and at a temperature higher than 550 ° C, side reactions such as decomposition occur, which are not preferable.

More specifically, for example, a Lewis acid such as aluminum chloride is selected from the range of -10 to 180 ° C, preferably 20 to 150 ° C, and a solid acid such as silica / alumina is contained at 180 to 5 ° C.
It is selected from the range of 50 ° C, preferably 200 to 500 ° C, and 140 to 250 ° C, preferably 150 to 230 ° C for cation exchange resins such as perfluorosulfonic acid resins.

The diphenylmethane or benzyltoluene that is the raw material of the present invention is a substance produced without using chlorinated hydrocarbon as the starting raw material. As described in the aforementioned West German Patent Publication, a compound produced by using a chlorinated hydrocarbon such as benzyl chloride as a starting material, for example, benzyltoluene produced by using aluminum chloride catalyst with toluene and benzyl chloride, or benzene. Diphenylmethane and the like obtained by condensing and chloroform with an aluminum chloride catalyst are not preferable because they often contain chlorine. Therefore, for example, a compound such as benzyltoluene obtained by a disproportionation reaction with an aluminum chloride catalyst from diphenylmethane produced by condensing formaldehyde and benzene or alkylbenzene, or toluene and ditolylmethane is used as a raw material of the present invention. do it. Also,
It may be a compound obtained by a known method in which other chlorinated hydrocarbon is not used as a starting material. The other raw material of the present invention, toluene, is usually produced by physically separating petroleum by distillation or extraction. Therefore, toluene is usually substantially chlorine-free.

The molar ratio of toluene to be supplied to the reaction system is 1 or more with respect to diphenylmethane or benzyltoluene or the total amount of both. If the amount of toluene is smaller than this, a large amount of heavy components are produced, which is not preferable. The upper limit of this molar ratio is not particularly limited, but the more toluene is used, the more ditolylmethane tends to be produced. Therefore, in order that the amount ratio of benzyltoluene and ditolylmethane contained in the obtained reaction product is appropriate, the molar ratio of toluene is practically 1 to 30 with respect to the total amount of diphenylmethane or benzyltoluene or both. It is desirable to select within the range.

The reaction system may be a flow system or a batch system.
The reaction time is 20 minutes to 1 hour in the batch system and SV0.5 to 10 in the continuous system. The reaction pressure is not particularly limited, but is usually atmospheric pressure to 10 kg / cm ² .

After completion of the reaction, if necessary, the catalyst is separated and removed, and if necessary, neutralized, washed with water, and dried to obtain a reaction product containing benzyltoluene and ditolylmethane.

An electrically insulating oil consisting of benzyltoluene and ditolylmethane is then recovered from the reaction product by distillation, preferably vacuum distillation. During this distillation, the effluent temperature is adjusted appropriately so that the amounts of benzyltoluene and ditolylmethane are appropriate. The insulating oil composition of the present invention can also be produced by individually recovering benzyltoluene and ditolylmethane from the reaction product by distillation and mixing them. Further, the reaction products obtained by separately reacting by the method of the present invention may be separately distilled to recover the obtained benzyltoluene and ditolylmethane, and these may be appropriately mixed.

The electrical insulating oil composition produced by the method of the present invention,
In addition to being used for condenser oil, cable oil, etc., it is particularly suitable for impregnating oil-impregnated electrical equipment, such as oil-impregnated capacitors, oil-impregnated cables, etc., in which plastic is used as at least part of the insulating material or inductive material is there. As the plastic, in addition to polyester, polyvinylidene fluoride and the like, polyolefins such as polypropylene and polyethylene are particularly suitable. An oil-impregnated capacitor that is preferably impregnated is manufactured by winding a metal foil as a conductor such as aluminum and a plastic film and impregnating with insulating oil, or vapor-depositing a metal such as aluminum or zinc as a conductor. A layered metal plastic film is wound with a plastic film or insulating paper, if necessary, and impregnated to produce. The oil-impregnated cable is manufactured by winding an insulating material such as a laminated plastic film with paper or a plastic non-woven fabric around a conductor such as copper and impregnating it.

When used as an insulating oil, a conventionally known electric insulating oil, for example, phenylxylylethane, alkylbiphenyl, alkylnaphthalene or the like can be appropriately mixed in an arbitrary ratio.

[Effects of the Invention] Benzyltoluene in insulating oil obtained by the method of the present invention contains a lot of m-form having a low melting point among its positional isomers, and also in ditolylmethane, the methyl group was oriented in the m-position. Since it contains many positional isomers, it also has a low crystal precipitation temperature. Therefore, the electrical insulating oil composition of the present invention can essentially suppress the precipitation of crystals due to the synergistic effect of the components while utilizing the low viscosity at low temperature, which is the characteristic of benzyltoluene. Further, the amount of chlorine contained in the electric insulating oil is small, the oxidation stability is good, and an excellent electric insulating oil having no corrosiveness can be obtained.

The benzyltoluene contained in the reaction product obtained by reacting toluene with benzyltoluene is not necessarily an unreacted component. That is, by the disproportionation reaction of the present invention, benzyltoluene is reformed into one containing more m-form. Therefore, according to the method of the present invention, p-benzyltoluene or the like having a high melting point and originally difficult to be used as an electric insulating oil can be used as a starting material.

[Example] Method for producing composition (Composition 1) To a 10 l separable flask, 3.5 l of toluene, 1 of diphenylmethane and 60 g of aluminum chloride were placed, and 3
The mixture was stirred at 0 ° C for 4 hours. After the completion of the reaction, the catalyst is deactivated, neutralized, washed with water, and dried, and an electrical insulating oil composed of benzyltoluene and ditolylmethane is distilled by distillation.
0 ml was collected. The composition was benzyltoluene 52% (wt%, the same hereinafter) and ditolylmethane 48%. Isomeric distribution of benzyltoluene is m-form 63.9%, o-form 1
0.5% and p-form 25.6%. Further, 87.1% of ditolylmethane had at least one methyl group attached to the m-position.

(Composition 2) 3 l of toluene, 1 of benzyltoluene, and 60 g of aluminum chloride were placed in a 10 l separable flask, and 3
The mixture was stirred at 0 ° C for 4 hours. After completion of the reaction, deactivate the catalyst,
Neutralize, wash with water, dry, and distill to obtain 1200 ml of electrically insulating oil consisting of benzyltoluene and ditolylmethane.
Recovered. Its composition was 47% benzyltoluene and 53% ditolylmethane. The distribution of benzyltoluene isomers was as follows: m-form 59.6%, o-form 10.1%, p-form 23.2%
Met. Further, 84.8% of ditolylmethane had at least one methyl group attached to the m-position.

(Composition 3) To a 10 l autoclave, 2.8 l of toluene, 0.7 l of diphenylmethane, and 60 g of silica-alumina catalyst (trade name:
N-632L, manufactured by JGC Corporation, particle size: 12-14 mesh, alumina content: 13% by weight) was added, and the mixture was stirred at 260 ° C for 3 hours.
After completion of the reaction, the catalyst was removed and 370 ml of electrically insulating oil consisting of benzyltoluene and ditolylmethane was recovered by distillation. Its composition was 47% benzyltoluene and 53% ditolumethane. The isomer distribution of benzyltoluene is
The content was 54.3% for m-form, 16.7% for o-form and 29.0% for p-form. In addition, 80.6% of ditolylmethane had at least one methyl group attached to the m-position.

(Composition 4) Into a 10 l autoclave, 2.8 l of toluene, 0.7 l of diphenylmethane and 20 g of Nafion, which is a perfluorosulfonic acid resin known as a solid superacid (trade name: Nafion
Powder 501, manufactured by DuPont) was added, and the mixture was stirred at 190 ° C for 34 hours. After the reaction was completed, the catalyst was removed, and the electrical insulating oil consisting of benzyltoluene and ditolylmethane was removed by distillation.
0 ml was collected. Its composition was 51% benzyltoluene and 49% ditolylmethane. The isomer distribution of benzyltoluene is as follows: m-form 59.3%, o-form 13.4% and p-form
It was 27.1%. Further, 83.4% of ditolylmethane had at least one methyl group attached to the m-position.

(Compositions 5 and 6) By the same method as that used for producing the composition 1,
A mixture of benzyltoluene and ditolylmethane was obtained and distilled to obtain benzyltoluene and ditolylmethane separately. Compositions 5 and 6 of electrical insulating oils were obtained by mixing each in a weight ratio of 9: 1 and 1: 9.

(Composition 7) 730 g of toluene, 10 g and aluminum chloride were put into a 2 l separable flask, and 210 g was added while stirring at 70 ° C.
Benzyl chloride (benzyl chloride) was added in 2 hours, and the mixture was further stirred for 2 hours. After the completion of the reaction, the catalyst was removed, and distillation was performed to obtain 190 g of an electrically insulating oil containing benzyltoluene 40% and ditolylmethane 60%.

Here, the diphenylmethane used as the raw material for the compositions 1 to 4 was obtained by condensing benzene and formaldehyde with a sulfuric acid catalyst, and benzyltoluene was not mixed with benzene and ditolylmethane using an aluminum chloride catalyst. It was obtained by leveling.

Example 1 (Measurement of Chlorine Content of Electrical Insulating Oil) The chlorine content of Compositions 1 to 7 was measured by the Wick Bolt method. The amount of chlorine in composition 7 was 43 ppm. Further, in each of the compositions 1 to 6, the content was 1 ppm or less.

Example 2 (Destruction Test of Capacitor) Two biaxially oriented polypropylene films having a thickness of 14 μ were stacked and wound with an aluminum foil as an electrode to obtain a capacitance.
A 0.4 μF model capacitor was made. According to a conventional method, an electric insulating oil having each composition shown in Table 1 was impregnated. After cooling for 1 week at a temperature cycle of −50 ° C. in the daytime and −60 ° C. in the night, the sample was left standing at −50 ° C. for a day and night for the measurement. Ten capacitors were prepared and measured for each insulating oil composition. At −50 ° C., the potential gradient was increased by 10 V / μ to apply electricity, and the number of capacitors to be destroyed was calculated for each potential gradient. Table 1 shows the results.

As can be seen from the results in Table 1, in the composition 5 in which the majority is benzyltoluene, the life of the capacitor is short, and the measured values vary.

Example 3 (Study of Oxidation Stability) Composition 1 and composition 7 were examined for oxidative stability in accordance with ASTM D-1934. The results are shown in Table 2.

From the above table, it is understood that the oxidation stability of the composition 7 containing a large amount of chlorine is poor.

Claims (3)

(57) [Claims] 1. Toluene and diphenylmethane or benzyltoluene produced without using a chlorinated hydrocarbon as a starting material are prepared in the presence of a disproportionation catalyst at −10 to 550 ° C.
To obtain a reaction product containing benzyltoluene and ditolylmethane, and then recovering benzyltoluene and ditolylmethane from the reaction product by distillation. Benzyltoluene 20 to 80% and ditolumethane 80 to 20% %, A method for producing an electrically insulating oil composition. 2. The method for producing an electrically insulating oil composition according to claim 1, wherein the chlorinated hydrocarbon is benzyl chloride. 3. The disproportionation catalyst is any catalyst selected from the group consisting of a Lewis acid, a solid acid, a heteropolyacid, a super strong acid and a strong acid type cation exchange resin. A method for producing the electrically insulating oil composition described.