JPS6254212B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to novel liquid dielectrics based on nuclear chlorinated alkyl aromatic compounds prepared from chlorotoluene or chloroxylene or mixtures of both. Conventionally, polychlorobiphenyl-based compounds have been widely used in the field of electrical equipment insulation. This is because they have several advantages in addition to their electrical properties and are extremely well suited for use as liquid dielectrics. That is, it is extremely stable against temperature and hydrolysis, has no or very low flammability, has a low vapor pressure, and is not very expensive. Instead, their lack of biodegradability results in them accumulating in the environment, which severely limits their field of application and has led some countries to completely or partially ban them.
Moreover, their dielectric constants drop rapidly at extremely low temperatures, making it difficult to use them in extremely cold conditions. Other compounds have been proposed as liquid dielectrics, such as the esters described in French Patent No. 2,322,435, but the latter esters are easily combustible.
The polychloropolyphenyl alkanes described in FR 2 273 351 are made from alkanedihalides such as 1,1-dichloroethane and are not economically useful. The inventor of the present invention has discovered that it is possible to obtain a compound from a simple and inexpensive raw material, namely chlorotoluene or chloroxylene, which has no biphenyl nucleus and has various properties that allow it to be advantageously substituted for polychlorobiphenyl without causing any disadvantages in dielectric applications. I found out. In fact, the absence of a biphenyl nucleus and the presence of an alkyl group on an aromatic nucleus have an advantageous effect on biodegradability (Chemosphere No. 213, pp. 103-109 (1977))
(see G. Sundstrom, K. Olie and O. Hutzinger). Furthermore, it has been found that these compounds have significantly improved electrical properties at cryogenic temperatures compared to chlorobiphenyl, which makes these materials particularly useful in extreme application conditions. The inventors also revealed the basic properties of these compounds: (a) they have a high dipole moment; (b) they have good chemical stability; It is even practiced. (c) They have good resistance to ignition or combustion, and from these compounds are obtained the selected components of liquid insulation, especially insulation for transformers. These properties are manifested by high dielectric constant (ie, conductivity) values and by extremely low loss factor values over a wide temperature range that encompasses the range of normal use of liquid dielectrics. The compound constituting the dielectric of the present invention has the following general formula: (where n, x, y and z are 1 or 2). When y is 1, chlorotoluene is used, and when y is 2, chloroxylene is used. These compounds are prepared from one isomer or a mixture of isomers of chlorotoluene or chloroxylene by subjecting it to radical chlorination initiated in a conventional manner, i.e. photochemically or in the presence of a radical initiator. It will be done. This reaction can be carried out at a temperature of 0 to 150°C, preferably 20 to 100°C. The mixture thus obtained was then added to Friedel's
Craft catalysts such as AlCl ₃ , AlBr ₃ , FeCl ₃ are also added. Condensation is carried out between the produced chlorobenzyl chloride or methylchlorobenzyl chloride and excess chlorotoluene or chloroxylene according to the following reaction formula: This reaction can proceed at 20 to 100°C, and the ratio of compounds with n=1 varies depending on the excess amount of chlorotoluene or chloroxylene present, and as the excess amount of chlorotoluene or chloroxylene increases, n is advantageous for obtaining a compound of 1. After decomposing the catalyst and washing the organic phase, the mixture is distilled to recover unreacted chlorotoluene and chloroxylene. Unreacted components can be recycled to subsequent operations. In this case, mixtures of compounds with n=1 or 2 are separated by distillation. Of course, the crude product of the reaction is alkali (NaOH,
A prepurification treatment is carried out using Na ₂ CO ₃ , NaHCO ₃ or similar compounds of calcium or potassium) at temperatures of 20 to 350°C, preferably 200 to 250°C, and for varying periods of time depending on the chosen temperature. Must be. Sometimes a subsequent distillation is advantageous. The purification process that follows this pretreatment consists in using acid clay or activated alumina, alone or in a mixture, according to specific techniques known in the field of liquid dielectrics. It may likewise be advantageous to add stabilizers of the epoxide type or other types of stabilizers, such as tetraphenyltin or anthraquinone compounds, in a continuous stream. These additives are generally hydrochloric acid acceptors;
It is contained in an amount of 0.001 to 10%, preferably 0.01 to 0.3%. Moreover, when liquid dielectrics are used as insulating liquids for transformers, without compromising their good qualities, the following general formula:

It is possible, and sometimes advantageous, to mix with compounds of the formula: where a is 2 to 4, b is 0 to 2, and R is an aliphatic hydrocarbon group having 1 to 3 carbon atoms. Among the compounds corresponding to the above general formula, commonly used are trichlorobenzene or tetrachlorobenzene, which have a rather limited vapor pressure and can be introduced in proportions of from 30% to 60% of the weight of the mixture. The following examples are illustrative of the invention and are not in any way limited thereto. Implementation 1 Stirrer, chlorine supply pipe and 30W Philips TLADK
5080 g (40 mol) of o-chlorotoluene are introduced into 6 reactors equipped with irradiation lamps. Over 4 hours, 568g (8 moles) of chlorine gas was introduced and the temperature was raised to 70°C.
Keep at ℃. At that time, pull out the reaction product and give 100
Leave only ml in the reactor and add 16 mg of FeCl ₃ to this. The withdrawn product is then added over a period of 2 hours while maintaining the temperature at 30°C. At the end of the reaction, 15 min
Heat to 100℃. The product obtained is 10% of hydrochloric acid
Wash with aqueous solution 1 with stirring and then twice with 1 part water. The organic phase thus obtained was
Distill under vacuum to a total maximum temperature of 200℃.
A first fraction of 2950 g of o-chlorotoluene which distills off to 45 DEG C. is recovered. The second fraction (compound A) distilled out up to 200° C. weighs 1320 g and constitutes a compound of general formula (1) where n is 1. This compound A has the following structural formula: has. Reduce the pressure to 0.1mm of mercury and 210~
At 245° C., 480 g of a third fraction (compound B) is distilled off, which constitutes the compound with n=2. This compound B has the following structural formula: has. There are 140 heavy compounds with n greater than 2 in the reactor.
g remains. Compound A has the following properties: Specific gravity (20℃) = 1.210 Viscosity (20℃) = 15.17cst Refractive index = 1.595 Freezing point = <-50℃ Chlorine content = 28.1% (theoretical amount 28.3%) This compound is subsequently purified by adding 2% by weight of Na ₂ CO ₃ and heating to 200° C. for 4 hours, and then distilled at this temperature at 15 mm of mercury. After the treatments normally applied to dielectrics (contact with activated alumina and apart), this compound is combined with tetraphenyltin, a conventional dielectric stabilizer.
Add 0.1%. The dielectric constant ε was measured at various temperatures and frequencies according to the standard ASTM D924, and the curve shown in Figure 1 was obtained. For comparison, the same measurements were also carried out on trichlorobiphenyl treated in the same way. The results are shown by the curves in FIG. About trichlorobiphenyl
At 100KHz, a decrease in the value of ε is observed from 0°C. For Compound A, this decrease is observed only from -45°C at 100KHz. Loss factor (tg) (measured according to standard ASTM D924) as a function of temperature for various frequencies
Comparison of changes in δ) (Figures 3 and 4) also shows that Compound A compared to trichlorobiphenyl (Figure 4).
(Figure 3) shows a significant difference in behavior. The curve ensemble shifts toward lower temperatures for Compound A. Thus, at a frequency of 50 Hz, the loss factor increases rapidly from 0°C for trichlorobiphenyl, while for compound A it does not reach its minimum even at -50°C. Other properties of Compound A are very close to those of trichlorobiphenyl as shown in the table below.

[Table] Example 2 Operate in the same manner as in Example 1, but o
- Replacement of chlorotoluene by an isomer mixture of dichlorotoluene. Distilled to 13 mm of mercury after photochemical chlorination and condensation with excess dichlorotoluene
A main fraction is obtained which is distilled off at 230 DEG to 255 DEG C. and is constituted by a mixture of isomers corresponding to the general formula (), where n is 1 and x and z are 2. The compound thus produced has a specific gravity of 1.372 at 20°C and a chlorine content of 43.9% (theoretical value 44.4%). Example 3 The procedure was as in Example 1, except that p-chlorotoluene was substituted for o-chlorotoluene. After the reaction, a main fraction of 21 mm of mercury and distilled at 200-225° C. is obtained by distillation. This compound has the general formula (1) (where n is 1, x and z are 1)
It is a mixture of isomers. Its specific gravity at 20℃ is
1.207, the chlorine content is 28.0% (theoretical value 28.3%). The second fraction, which is distilled at 0.1 mm of mercury column and at 200 to 250°C, is expressed by the general formula (1) (where n is 2,
x and z are 1). Example 4 Applying the procedure of Example 1 to a mixture of 50% o-chlorotoluene and 50% p-chlorotoluene,
Distilled at a mercury column of 20mm and 200 to 230℃, and general formula (1)
(where n is 1 and x and z are 1) can be separated. The specific gravity of this compound is
1.207, and its chlorine content is 27.9% (theoretical value is 28.3%). Freezing point is below -25°C. The second fraction distilled at 0.1 mm of mercury and at 200 to 270° C. corresponds to general formula (1) (where n is 2 and x and z are 1). Example 5 Dichlorotoluene (50 in the presence of _FeCl3 )
obtained by limited chlorination of toluene at °C)
6.8 kg is charged into a reactor equipped with a stirrer, heating and cooling equipment, chlorine introduction equipment, equipment for releasing hydrochloric acid through a cooler, and an irradiation lamp. temperature 80
℃ and introduce chlorine at a rate of 100 g/hour. The reaction is stopped after 5 hours. Degas the mixture with nitrogen and transfer to a separatory funnel, leaving only about 500 ml.
Add 16g of _FeCl3 . The withdrawn product is then returned to the reactor over a period of 2 hours while maintaining the temperature at 80-100°C. A large amount of hydrochloric acid is separated. Hold temperature for an additional 2 hours. The resulting mixture is washed with hot and then cold water, and the excess dichlorotoluene is distilled off in a 30-stage column at a pressure of 250 mm of mercury, then reduced to 10 mm. Fraction of products with boiling point 210-240℃
2240g is isolated. This compound contains 44.3% chlorine and corresponds to the formula: The fraction thus recovered contains 1.833 g of commercially available trichlorobenzene, consisting of an isomer mixture of 63% 1,2,3-trichlorobenzene, 36% 1,2,4-trichlorobenzene and 1% tetrachlorobenzene (i.e. 45% of the mixture obtained). ) is added. Add 4 g of tetraphenyltin. Characterization of a mixture of 70% Askarel (conventional polychlorobiphenyl mixture) and 30% trichlorobenzene by measuring the physical and dielectric properties of the mixture after a conventional dielectric purification process with continuous treatment with activated alumina. Compare with.

[Table] Figures 5 and 6 show the difference in loss factor as a function of temperature and frequency between the mixture obtained in this example and Askarel D type, and Figures 7 and 8 show the difference between the permittivity of the materials. It shows the difference.

[Brief explanation of the drawing]

Figures 1 and 7 show the dielectric constant ε of the compound of the present invention.
FIG. 2 and FIG. 8 are curve charts representing the permittivity ε of the prior art compounds (trichlorobiphenyl and askarel D type), respectively, and FIGS. 4 and 6 are curve charts showing the loss ratio of compounds of the prior art (trichlorobiphenyl and askarel type D), respectively.

Claims (1)

[Claims] Primary formula: (where n, x, y and z are numerical values of 1 or 2). 2. The liquid dielectric material according to claim 1, which is applied as an insulating material for use as an insulating liquid for a transformer or as an insulating material used by impregnating between layers of a capacitor. 3 Partial radical chlorination of one isomer or mixture of isomers or a mixture of two compounds of chlorotoluene or chloroxylene, followed by excess chlorobenzyl chloride or methylchlorobenzyl chloride formed in the presence of a Friedel-Crafts catalyst. of the following formula: (In the formula, n, x, y and z are numerical values of 1 or 2.) A method for producing a liquid dielectric material comprising a compound having the formula: 4. The excess chlorotoluene and/or chloroxylene that remained unchanged during the chlorination reaction process is 40% or more in excess of the amount of chlorobenzyl chloride or methylchlorobenzyl chloride obtained. Manufacturing method. 5th order formula: (In the formula, n, x, y, and z are numerical values of 1 or 2.) A liquid dielectric consisting of a compound is expressed by the following general formula: (wherein a varies from 2 to 4, b varies from 0 to 2 and R is an aliphatic hydrocarbon group of 1 to 3 carbon atoms). ,
An insulating liquid for transformers, which comprises adding to this mixture an amount of epoxidized oil or an acid acceptor of the type tetraphenyltin in an amount of 0.001 to 10%. 6. The insulating liquid according to claim 5, wherein the liquid dielectric is introduced into the mixture in a proportion of 20 to 80%. 7 The above liquid dielectric has the following formula: (i.e. n = y = 1, x = z = 2), which has the following composition: 1, 2, 4-isomer 50 ~
6. The insulating liquid according to claim 5, which is introduced into commercially available trichlorobenzene consisting of 85% and 50-15% of the 1,2,3-isomer in a proportion of 40-70%.