DE2523898C3 - Liquid dielectrics - Google Patents

Description

The invention relates to the use of liquid dielectrics, in particular liquids based on them of certain polychloropolyphenyl-l.l-alkanes.

It is well known that the substances used to insulate electrical equipment must have a specific value Have number of specific properties; Above all, it is important that they also have a high relative Have dielectric constant and good heat resistance and are non-flammable or non-flammable are. There are few among the currently known liquid dielectrics that also offer these inexpensive ones Have properties. There is therefore still a need for products that meet the requirements of electrical industry.

The invention was based on the object of providing new liquid dielectrics which characterized by a high relative dielectric constant and good heat resistance and non-flammable or are not flammable. This object is achieved by the invention specified in claim 1 solved.

It has been shown that polychloropolyphenylalkanes, which are based on certain alkyl dihalides and certain chlorinated aromatics produced by the Friedel-Crafts method are excellent Properties related to the relative dielectric constant, the heat resistance and the Have non-flammability or non-flammability. Further advantages of these new products are emerging the following description.

The implementation products from the starting compounds described below are used for Used to isolate electrical equipment.

The alkyl dihalides are methane, 1,1-ethane and 1,1-propanedihalogen compounds in question; preferred are the chlorine derivatives. A mixture of these may also be of interest and importance Use Alky ^ halogen compounds.

The chlorinated aromatic compounds include ortho-dichlorobenzene, alone or with Monochlorobenzene and / or 1,2,3-trichlorobenzene is used or else monochlorobenzene and 1,2,3-trichlorobenzene alone or together.

Dielectrics made by condensing alkyl dihalogen compounds and chlorobenzene produced by the Friedcl-Craftsschcn process are already known. The alkyl dihalogen compounds used here are, however, fundamentally different compounds than in the case of the use according to the invention, because the two halogen atoms are attached to different carbon atoms are bound (US-PS 22 44 284). It has surprisingly been found that such known Polychloropolyphenylalkanes have a markedly lower heat resistance than those according to the invention compounds used starting from a dihaloalkane whose halogen atoms are connected to the same Carbon atom of the chain are bonded. This difference in resistance is evident in the Recognizable drawing in the for certain conversion products according to the state of the art and according to According to the invention, the development of the total pressure as a function of the temperature are recorded. The experiments were carried out according to Edward S. Blake et al., Journal of Chemical and engineering data, Vol. 6, No. i ', January 1961, pp. 87-98. The curves correspond to the following connections:

1. conversion product from

1,2-dichloropropane and o-dichlorobenzene

2. Conversion product from

1,2-dichloropropane and monochlorobenzene

3. Conversion product from

1,2-dichloroethane and monochlorobenzene
4. Conversion product from

1,1-dichloroethane and monochlorobenzene

5. Conversion product from

Methylene chloride and monochlorobenzene

6. Conversion product from

1,1-dichloroethane and o-dichlorobenzene

The comparison of the curves shows that the reaction products obtained from ί, Ι-dihaloalkanes are considerably more heat-resistant than the known products, because their decomposition - recognizable by the Pressure increase - begins only at a much higher temperature than the decomposition of the known Products.

To produce the polychloropolyphenylalkanes used as dielectrics according to the invention, the abovementioned chlorobenzenes are reacted with the dihaloalkane in the presence of a metal chloride, in particular aluminum chloride, as a catalyst. In general, an excess of chlorobenzene (s) based on the stoichiometrically required ratio is used; the latter is 2 moles of chlorobenzene / mole of alkyl dihalide. It is advantageous to work with a ratio of 2.1 to 10 moles of chlorobenzene (en) to 1 mole of alkyl dihalide; however, there is no really critical upper limit. If o-dichlorobenzene is used at the same time as monochlorobenzene and / or 1,2,3-trichlorobenzene, it should make up at least 50 mol%, preferably at least 70 mol% of the total amount of aromatic chlorohydrocarbons. Likewise, when working with a mixture of monochlorobenzene and 1,2,3-trichlorobenzene, the latter should make up at least 50 mol%, preferably at least 70 mol% of the mixture. The reaction is carried out at a moderate temperature in the range from 20 to 120 ^° C. until the evolution of hydrogen halide ceases. Is essential. that the implementation is extremely easy to carry out; this is another benefit.

The crude reaction products exist after the catalyst or the excess has been separated off Chlorobenzene essentially consists of a mixture of di (chlorophenyl) alkanes. where the benzene nuclei at the same aliphatic carbon atom are bonded.

They can also contain a small proportion of poly (chlorophenyl) alkanes with more than 2 benzene nuclei arise through polycondensation. The number of chlorine atoms attached to the phenyl groups depends of course on the chlorobenzene (s) used. Becomes a mixture of chlorinated aromatics used, the reaction product contains symmetrical and asymmetrical compounds at the same time, d. H. Compounds that have an equal or unequal number of chlorine atoms in their phenyl groups contains bound.

The reaction products are used in the usual way as dielectrics further treated, d. H. by simple distillation, steam distillation or by other physical Separation process cleaned. If necessary, the distillate is collected in several fractions, whereby of course, any such fraction obtained from the original reaction product according to of the invention can be used.

The reaction products or the fractions obtained therefrom are for the most part liquids with a pour point below 0 ° C, which does not crystallize. Some products are solid at a relatively high temperature. They have interesting properties of being non-flammable; a certain number of them have no focal point (point de feu). As shown above, is the heat resistance of these compounds is considerably higher than the heat resistance of the known ones Polychloropolyphenylalkanes. Furthermore, the compounds according to the invention are notable for their high relative dielectric constant.

Because of this combination of properties, the compounds used are excellent Dielectrics are generally used for all insulation of electrical equipment, especially in transformers as well as for the impregnation (as impregnation resin) of capacitors. The liquid and Non-crystallizing mixtures or fractions can be used alone. The one at room temperature solid or crystallizing compounds are combined with other products according to the invention or fractions or combined with known liquid dielectrics, for example with polychlorodiphenylene, Trichlorobenzene, esters of organic acids, etc. The resulting mixtures are flowable and do not allow any of the isomers to crystallize out at any temperature. All according to the invention Products used can otherwise with each other or with known insulating liquids be mixed. This gives end products, their properties such as viscosity and relative dielectric constant adjusted at will and the particular intended use can be customized.

The following examples serve to explain the invention in more detail.

example 1

1544 g (10.5 mol) of o-dichlorobenzene containing 10 g (0.075 mole) of anhydrous aluminum chloride was heated to 85 ⁰ C and then under stirring with 149 g (1.5 mol) of 1,1-dichloroethane h added over 3 . The reaction was slightly exothermic. The elimination of hydrogen chloride stopped about 1 hour after the addition of the dichloroethane was complete. Then, the reaction mixture was neutralized by 2-hour treatment with 30 g of KOH at 8O ⁰ C and then filtered. 1580 g of liquid organic phase were obtained.

First 1160 g of excess dichlorobenzene were distilled off from this mixture and then the ^{fraction passing over at 1 mm Hg between 170 and 200 °} C. was collected, yield 357 g.

This fraction was a clear, translucent liquid with the following properties:

density
viscosity
Relative dielectric constant
measured at 100 kHz
Pour point

1.35 / 26 ° C
33OcSt / 22.5 ° C

8.18 / 25 ° C

-13 ° C

(according to ASTM D 97-66)

Chromatographic analysis showed that the distillate was 98.7% by weight of isomers of 1,1-di (dichlorophenyl) ethane contained.

Example 2

The procedure was as in Example 1 and a mixture of 40 mol% monochlorobenzene and 60 mol% Brought o-dichlorobenzene to implement. 7.5 moles of chlorobenzenes were used per mole of 1,1-dichloroethane. The reaction temperature was 75 ° C.

After the excess chlorobenzenes had been distilled off, the ^{fraction passing over at 3 mm up to 270 °} C. was collected; it consisted of the desired polychloropolyphenylethanes. The distillate had the following properties:

density
viscosity
Relative dielectric constant
at 100 kHz
Pour point
Flash point
No focus

1.306 / 24 ° C
68.4cSt / 22.5 ° C

7, O4 / 27 ° C

-28 ⁰ C (ASTM D 97-66)
204 ⁰ C (ASTM D 92-66)
(ASTM D 92-66)

Example 3

2646 g (18 mol) of o-dichlorobenzene and 24 g of aluminum chloride were brought to 85 ^° C. and 306 g (3.6 mol) of methylene chloride were added over the course of 3 h; the reaction mixture was then degassed with the aid of a gentle stream of nitrogen at the same temperature of 85.degree. After 6.3 mol of hydrogen chloride had been collected in this way, the reaction mixture was hydrolyzed with 50 g of water, then neutralized with KOH, and the organic layer was distilled off. After separating off the excess o-dichlorobenzene, 680 g of product were obtained, which passed over and crystallized at 175 to 190 ° C./1 mm Hg.

Example 4

A mixture of 2352 g (16 mol) of o-dichlorobenzene and 26.7 g of aluminum chloride was heated to 8O ⁰ C and then in the course of 150 min uniformly with a mixture of 198 g (2 mol) of 1,1-Dichlorälhan and 225 g (2 mol) monochlorobenzene added. After the addition had ended, the temperature was held at 80 ° C. for a further half an hour; it was then degassed for 1 hour by passing a gentle stream of nitrogen through it. A total of 3.96 mol of hydrogen chloride was collected, corresponding to 99% of theory.

The catalyst was added while stirring the mixture

hydrolyzed with 20 g of water; it was then neutralized with KOH at 80 ° C. The mixture was filtered and allowed to settle the filirate; the excess chlorobenzenes were drawn off overhead in an amount of 2083 g.

The remaining crude product was distilled in vacuo; 400 g of a fraction were obtained which, at 175 until passed 190 ° C / 1.5 mm Hg. This product was one pale yellow liquid that does not above -30 "C crystallized and had a relative dielectric constant of 7.9 / 20 "C.

The dielectrics used according to the invention are especially used as impregnating resins for Capacitors are used - advantageously with HO acceptors of a known type such as Hpoxyverbindungen offset.

Claims (2)

Patent claims: 1. Use of Polychlorpolyphenylalkanen, which by reacting a methane dihalide, Ethane-l, l-dihalide and / or propane-l, l-dihalide with monochlorobenzene and 1,2,3-trichlorobenzene or with o-dichlorobenzene alone or in a mixture with monochlorobenzene or 1,2,3-trichlorobenzene or have been obtained with both compounds in the presence of a Friedel-Crafts catalyst, as liquid dielectrics. 2. Use of the dielectrics according to claim 1 together with known liquid dielectrics and / or epoxy compounds as HCI acceptors.