NO139582B - DIELECTRIC FLUIDUM BASED ON HALOGENEPHENYLOXIDES AND HALOGENALKYLDIPHENYLOXIDES - Google Patents

Description

The most used dielectric fluids to date are highly chlorinated hydrocarbons, such as e.g. polychlorinated biphenyls (PCBs). These are functionally satisfactory, but they are highly unsatisfactory from an environmental protection and ecological point of view.

point, as they are highly toxic and particularly resistant to biological degradation. For this reason, people have constantly sought to

find satisfactory replacement materials.

Polyhalogenated diphenyl oxides are known to be use-

only as dielectric fluid, either alone (US Patent 2,022,634)

or in admixture with alkyl diphenyl oxides (US patent 2,169,995).

However, such fluids can no longer be accepted, as the polyhalogen component is not sufficiently biodegradable.

Alkylated diphenyl oxides have been suggested for use

as a dielectric fluid (US patent 2 170 809), but has due to

its poor electrical properties, especially the low dielectric constants, did not find wider application.

Lower alkyl chlorodiphenyl oxides are known and have been proposed for use as a dielectric fluid (US Patent 2,170,989),

but has not been accepted within the industry due to high volatility, low flash point and relatively poor electrical properties.

Norwegian patent no. 133 519 previously described a dielectric liquid based on halogen-containing diphenyl oxides and consisting of a mixture containing at least 30% by weight of both halogen diphenyl oxide and halogen alkyl diphenyl oxide. However, it has now been found that certain mixtures of halogen diphenyl oxides and semi-alkyl diphenyl oxides surprisingly prove to be less toxic than the mixtures described in patent no. 133,519. This lower toxicity is considered to be of great practical importance at a time when it is considered very important to reduce environmental pollution.

The present invention thus relates to a dielectric fluid consisting of a mixture of monochloro or monobromo diphenyl oxide and monochloro or monobromo alkyl diphenyl oxide, characterized in that the mixture consists of (a) 5-15% by weight of at least one monochloro or monobromo diphenyl oxide and (b) 85-95% by weight of at least one monochloro or monobromoalkyldiphenyl oxide having 1-2 alkyl groups, each having 2-12 carbon atoms, which oxide has a total number of alkyl carbon atoms of 2-16.

A preferred embodiment of the invention consists of

that (a) is monochlorodiphenyl oxide and (b) is a mixture of monochlorobutyldiphenyloxide, monochlorodibutyldiphenyloxide and monochlorotributyldiphenyloxide.

The dielectric fluid according to the invention is generally at the same level as the dielectric fluid according to patent no.

133,519 in terms of dielectric properties.

The alkylation and halogenation of diphenyl oxide (DPO) is

known in and of itself. It is also known that these reactions result in a mixture of isomeric, homologous and/or analogous compounds, where the number and position of the substituents varies. Such mixtures, which with a foreign word can be called "cogeneric" mixtures, can be completely or partially separated by fractional distillation and/or crystallization or in some other way. For the present purpose, however, it has been found that such a separation is generally not necessary, provided that the average values lie within the limits specified in the present case. In particular, the polyhalogen components should only be present in very low concentrations, as these are very toxic and resistant to biological degradation. For most purposes, concentrations of dihalogen compounds of up to approx. 5% is tolerated.

For further elucidation of the op<p>invention it is now necessary

some examples are given.. The following table I shows data regarding

dielectric mixtures according to the present invention (examples 1 and 2) compared to similar mixtures which, in terms of composition, fall just outside the scope of the invention (comparative examples A and B).

The above-mentioned materials are easily biodegradable, which also applies to the homologous mono- and dialkylchloro- and -bromo-DPO compounds.

EXAMPLE 3.

The toxicity of the dielectric fluids to fish was determined in a 96 hour test in static water using "Fathead" abalone. In these experiments, the toxicity of monochlorodiphenyl oxide, monochlorobutyldiphenyl oxide and mixtures thereof was determined. Table II below shows the results that were found. Ten fish were used in each experiment. EC^Q is defined as the concentration of the oxides in the water, measured in mg/l, at which 50% of the fish were unaffected (the other five fish were either dead or showed signs of poisoning).

IG means not toxic at the solubility concentration in water.

It will be seen from the data given in Table II that the EC^q for the monochlorodiphenyl oxide as such is only 1.7 mg/l. The presence of the monochloroalkyldiphenyl oxide seems to reduce the toxicity of Cl-DPO, as the real EC,-0 is far greater than expected for mixtures containing up to 15% Cl-DPO.

The values for expected toxicity in the above Table II have been arrived at as follows: 1. All calculations are based on (1) the observed EC^Q value of 1.7 for 100% Cl-DPO, which is highly toxic, and '( 2)

the fact that 100% C4C1-DP0 is not toxic, at least at the concentrations used in these experiments (cf. the rightmost column in Table II).

2. For the determination of the expected value for a mixture of

30% Cl-DPO and 70% C4Clr©PO multiply 1.7 by 100/30,

because Cl-DPO is diluted to 30% concentration, since 70%

is the non-toxic C4C1-DP0. This gives the value 5.7.

3. In a similar way, the calculation is performed for the 75%-25% mixture: 1.7 x 100/25 = 6.8, etc.

Other alkylhalogen DPO compounds which can be mixed with Cl-DPO and/or Br-DPO, for the production of dielectric fluids according to the invention, include ethyl-, propyl-, hexyl-, octyl-, decyl-, dihexyl-, dioctyl-, hexyloctyl-, heptylnonyl-

and hexyldecyl-Cl-DPO and the corresponding alkyl-Br-DPO compounds. In these compounds, the positions of the substituents in the DPO core are of little importance for the purpose of the invention. Furthermore, the configuration of the alkyl groups is relatively unimportant, although those that are highly branched are less easily biodegradable than those that have unbranched chains.

Claims (2)

1. Dielectric fluid consisting of a mixture of monochloro- or monobromo-diphenyl oxide and monochloro- or monobromo-alkyldiphenyl oxide, characterized in that the mixture consists of (a) 5-15% by weight of at least one monochloro or monobromodiphenyl oxide and (b) 85-95% by weight of at least one monochloro or monobromoalkyldiphenyl oxide with 1-3 alkyl groups, each having 2-12 carbon atoms, which oxide has a total number of alkyl carbon atoms of 2-16. 2. Fluid according to claim 1, characterized in that (a) is monochlorodiphenyl oxide and (b) is a mixture of monochlorobutyldiphenyloxide, monochlorodibutyldiphenyloxide and monochlorotributyldiphenyloxide.