SUBSTANTIALLY NON-FLAMMABLE BIOLOGICALLY DEGRADABLE FUNCTIONAL FLUID

Substantially non-flammable biologically

The invention relates to a substantially non-flammable, biologically degradable functional liquid, particularly a hydraulic fluid or an insulating fluid for electrical apparatus, which comprises a bromine containing benzyl-

5 toluene derivative as the essential component.

Chlorinated aromatic compounds, particularly chlorinated biphenyls, have taken an important place in various fields of technology in the last few decades. The polychlorinated biphenyls, in particular, have been used to

10 a large extent as hydraulic fluids, as insulating fluids for electrical equipment and as flame suppressing additives for plastics and the like. However, in the last few years, these compounds have been the subject of considerable dispute. It has been determined that

15 these products exert harmful effects on health and the environment and they have potentially catastrophic dangers in that, when burned, highly poisonous dioxin and dibenzofuran may be formed. This has already lead in part to the complete banning of the manufacture or at 20 least the use of such compounds by the state supervisory organizations and in part to the imposition of serious limitations to the use of these substances.

To overcome these disadvantages it has been proposed in European Patent No. 88 650 granted September 14, 1983 to use instead chlorinated benzyltoluenes and chlorinated benzylxylenes as lubricants and also as hydraulic fluids because these compounds are substantially inflammable and⁵ resist oxidation and are also biologically degradable and are advantageous in view of their low toxic properties.

GB-PS 1 504 655 granted March 22, 1978 describes electrical equipment which contains biologically easily degradable dielectric fluids, namely haloginated diphenyl¹⁰ methane, which are characterized in that the halogen substituents and possibly alkyl substituents are located only in one of the two phenyl rings, while the other phenyl ring remains unsubstituted, since only such haloginated diphenylmethanes having an unsubstituted phenyl group are 15 easily biologically degradable, while the diphenylmethanes substituted on both phenyl residues are resistant to microbiological degradation.

European Patent No. 8251 granted February 20, 1980 discloses fluid dielectrics which can be used, for example, 20 as insulating fluids for transformers or as impregnating materials for insulating layers using capacitors, it is concerned with alkyl aromatic compounds which are chlorinated on the aromatic nucleus and which may be obtained from chlorotoluene and/or chloroxylene, for example tetra25 chlorobenzyltoluene, and it is indicated that these compounds have advantages over the multichlorinated biphenyls previously used for the same purpose. The absence of the biphenyl nucleus and the presence of the alkyl groups on the aromatic nucleus are accordingly credited with the

30 favourable action on the biological degradative behaviour.

Finally, European Patent No. 71 338 granted February 9 1983 describes electroviscous fluids which consist of hydro phobic liquids in which solid hydrophilic particles are dispersed. Upon application of an electrical field to such 35 a suspension the viscosity of this mixture rises drastically. This change is reversible and rapid so that such suspensions can be used, for example, in

electronically controllable clutches. It is indicated that the hydrophobic liquids in the mixture have a high boiling point, a low viscosity, suitable electrical properties and chemical stability and low toxicity and are 5 preferably biologically degradable. For this purpose, according to this European Patent Application, halogenated diaryl derivatives are suitable as the hydrophobic fluids, the aromatic nuclei of which are combined with one another via various bridges and have fluorine, chlorine or bromine 10 atoms as the halogen substituents. It is stated that these diaryl derivatives should be asymmetrically substituted because then a lower solidification point of the fluid and an improvement of the ability to be biologically degraded is obtained.

15 The conventional functional liquids are not satisfactory in all respects because they either do not fulfil the criterion of non-flammability required by hydraulic and insulating fluids or they have disadvantageous properties resulting from their inflammability such as poor 20 biodegradability, toxicity of the fulids or their decomposition products, unfavourable viscosity-temperature properties or incompatibility with sealing elements.

The object of the present invention is to provide a functional fluid which has physical properties necessary 25 for the intended use and while having high chemical stability nevertheless can be biologically degraded and is nontoxic and does not give rise to highly toxic products, such as dioxin for example, upon improper treatment.

It has been surprisingly found that a particular group 30 of halogenated diaryl derivatives not only, on the one hand, exhibits valuable technical properties, but also, on the other hand, does not exhibit the dangerous and the environmentally hazardous properties of the conventional compounds, so that the compounds are especially suitable 35 as or for functional fluids.

The invention provides a non-flammable biologically degradable functional fluid consisting of or containing at least one bromine containing benzyltoluene derivative of general formula If

(I)

(Br)_χ (Br)_χ,

5 in which x is 1 or 2,

x' is 0 or 1,

y is 0, 1 or 2,

y' is 0, 1 or 2,

z is 0, or 1, and

10 z' is 1 or 2

with the proviso that the relationship

y+y' =0, 1 or 2 and

x + x" + y + y' = 1, 2 or 3

is fulfilled.

15 The bromine-containing benzyltoluene derivatives used according to the invention as or in functional fluids are thus compounds which are substituted on both nuclei wherein at least one bromine substituent and one methyl group must be present. Both the nuclei can however carry several

20 bromine atoms and several methyl groups and the positions of these substituents are not important so that, according to the invention, all of the positional isomers of these bromine-containing benzyltoluene derivatives of formula I given above can be used in or as functional fluids.

25 In addition one or both of the phenyl groups may contain chlorine atoms as substituents.

It has surprisingly been found that these bromine-containing benzyltoluene derivatives used according to the invention possess a more advantageous compatibility with 30 the environment than the conventional halogenated diaryl derivatives, and at the same time possess excellent physical properties which make them particularly suitable for use as functional fluids such as hydrulic fluids or insulating fluids for electrical equipment.

Surprisingly, it has also been found that the substituted bromine-containing benzyltoluene derivatives of the invention of general formula I given above, which are substituted on both phenyl rings, can be biologically degraded without further treatment which appears surprising in view of European Patent^No· 71 338

10 and GB-PS 1 504 655 discussed above. Moreover, the bromine-containing benzyltoluene derivatives of general formula I above used in accordance with the invention have the further surprising advantage that in normal working conditions they are fluid and exhibit a particularly

15 favourable viscosity-temperature relationship. Moreover they possess a high flame point, are of low toxicity and low corrosiveness and do not produce highly toxic dioxin products when improperly overheated, which can occur accidentally in the case of polychlorinated biphenyls.

20 Moreover it has been found that the bromine-containing benzyltoluene derivatives used according to the invention are compatible with sealing elements to an excellent extent, so that the group of compounds of the invention have unexpectedly proved advantageous for the uses

25 discussed above.

Particularly preferred are substantially non-flammable, biologically degradable functional fluids which, as the bromine-containing benzyltoluene derivatives, contain a compound of general formula II

30

Even more preferred are functional fluids according to the invention which contain a bromine-containing benzyltoluene derivative according to formula III, IV or V below.

Naturally the functional fluids according to the invention may contain the bromine-containing benzyltoluene 10 derivatives defined above alone, but preferably however they are used in the form of mixtures, especially in the form of mixtures of the individual positional isomers of these compounds.

The bromine-containing benzyltoluene derivatives

15 according to the invention of the formulae given above and used in the invention in or as functional fluids are partially known, for example in the general formula of European Patent No. 71 338 mentioned above and also in the generic definition of DE-OS 23 36 289 published 1975. The 20 former reference discloses an enormously large group of compounds, and mentions the use of the invention neither expressly nor in the examples. DE-OS 23 36 289 describes essentially chlorinated o-benzyltoluene, which is described as a valuable starting material for the preparation of anthracene and anthraquinone and its derivatives. The compounds of the invention of the general formula given above and their uses differ from the biologically degradable bromine-containing benzyltoluene derivatives described in GB-PS 1 504 655 in that they are not just asymmetric but rather are substituted on both phenyl rings and nevertheless surprisingly have advantageous properties.

The preparation of the bromine-containing benzyltoluene derivatives of the invention takes place in a conventional manner either by the halogénation of the.non-halogen substituted corresponding benzyltoluene with elemental bromine or a mixture of bromine and chlorine in the presence of a known halogénation catalyst such as iron, FeClg, FeBr^» AlCl^ » TiCl^ and the like. In this

way the reaction can take place at room temperature or, depending on the catalyst employed, at temperatures between -5 and +40°C.

A further preferred method for the preparation of

the bromine-containing benzyltoluene derivatives of

the invention of general formula I above involves the condensation of a compound of general formula VI

in which x', y* and z' are as disclosed above, with a compound of general formula VII

(VII)

in which Hal represents bromine or chlorine and x, y, z are as disclosed above. The condensation can be carried out, if necessary, in the presence of a Friedel-Crafts

5 catalyst, such as FeCl^, FeBr^, AlCl^ and/or TiCl^,

in the presence of an excess of the compound of general formula VI.

The bromine-containing benzyltoluene derivatives according to the invention exhibit a substantially

10 improved flame resistance than the chlorine substituted compounds known from European Patent Application No.

88 650 while at the same time exhibiting improved viscosity-temperature relationships.

The known asymetrically substituted dibromobenzyl-

15 toluene of GB-PS1 504 655 are solid at room temperature, while the isomer brominated on both phenyl rings solidifies at -25°C, which is particularly advantageous when using these compounds as hydraulic fluids or insulating fluids.

20 The bromine-containing benzyltoluene derivatives of the invention have proved useful not only as hydraulic fluids but also as insulating fluids for electrical equipment, such as for example condensers, transformers and the like, not only on the basis of their favourable 25 viscosity-temperature relationships, but also on account of their very favourable flame resisting effect. The functional fluids of the invention can in consequence of this be used, in particular, as non-flammable hydraulic or insulating fluids which, on the basis of their low

30 toxicity, their low inclination to form poisonous decomposition products and their biological degradability, represent a considerable contribution to technology.

As already explained the bromine-containing benzyltoluene derivatives mentioned above can be contained individually or also in the form of mixtures, preferably 5 in the form of isomer mixtures, in the functional fluids of the invention instead of being used alone as said fluids.

The invention is described in more detail in the following examples.

1Preparation Example

Preparation of dibromobenzyltoluene by condensation of bromotoluene with bromobenzylbromide.

For the preparation of dibromobenzyltoluene, bromotoluene was first prepared by the bromination of toluene with elemental bromine in the presence of anhydrous

FeC1^» a∩d this was then brominated at the side chain.

With this 8.3 Mol of bromotoluene were heated in

the presence of 0.5g of a radical chain initiator

( α, α'-Azobisisobutyronitr ile) to a temperature of 80°C.

1.66 Mol of bromine were added drop-wise with cooling under irradiation with an ultra-violet lamp having a power of 300 W. The resulting hydrogenbromide was absorbed in a wash bottle containing cooled water.

The cooled mixture was then dropped into a suspension of 6g FeCl^ in 1.6 Mol of bromotoluene at a temperature 30°C to bring about the condensation reaction. The resulting gaseous hydrogenbromide was absorbed into cooled water in a wash bottle in the same manner as described above. The formation of by-products (brominated dibenzyltoluene), was suppressed during this condensation reaction by the presence of a large excess of bromotoluene.

After the termination of the addition the mixture

was heated to 50°C for 30 minutes, after which the cooled reaction mixture was washed with one liter of water, then with one liter of 10% sodium hydroxide solution and finally once again with one liter of water. The organic phase was dried and the excess bromotoluene was distilled off .

The remaining fluid was distilled under 0.4 mbar, and 395g of a main fraction boiling between 155 and 166°C at 5 0.4 mbar was obtained and this was identified by mass spectrometry as dibromobenzyltoluene. Thereby an investigation of the isomers was foregone.

The electron stream mass spectrum of the resulting dibromobenzyltoluene is given in the Table below.

TABLE

Electron Impact Mass Spectrum of Dibromobenzyltoluene m/κ Relative Total Ion I∩tensi ty m/x Relat i ve Total Ion Intensity

The remaining bromine-containing benzyltoluene derivatives according to the invention can be obtained in an analogous manner to the above described reaction scheme by using conventional methods or also by direct bromination 5 or bromination and chlorination of benzyltoluene, in which case of course reaction mixtures are obtained which in suitable ways, for example by gas chromatography, must be separated into the bromine-containing benzyltoluene derivatives of the general formula given above according 10 to the invention.

The non-flammable, biologically degradable functional fluids of the invention may contain in addition to the bromine-containing benzyltoluene derivatiaves additional components and additives normally used in functional

15 fluids, for example corrosion inhibitors such as alkaline earth sulfonates, stabilizers such as amine derivatives or phenolic products, wear reducing additives such as zinc dialkyldithiphosphate, acid acceptors such as epoxide compounds, tin tetraphenyl etc., as well as anti-

20 foaming agents such as soap, silicone, glycol, phosphate esters, and viscosity index enhancers such as polymethacrylate, polyisobutylene. Further the bromine-containing benzyltoluene derivatives used according to the invention can be modified with various suitable products such as

25 mineral oil, glycols, etc.

The following examples serve to further clarify the non-flammable biologically degradable functional fluids of the invention.

30 Investigation of the properties of the dibromobenzyltoluenes which are preferred as the bromine-containing benzyltoluene derivatives of the invention, a)Biological Degradability

The investigation of the biological degradability was 35 carried out by means of a known measuring procedure for the determination of the biological degradability anionic and non-ionic synthetic tensides (surface-active substances) namely the OECD-screening test (Federal Law Publication 1 (1977), page 245) (modified) for non-ionic 5 tensides.

Aerobic polyvalent microorganisms from the outlet of a biological sewage plant were used as an innoculating suspension. In this method the first sample was taken after seven days, the second sample after 14 days and the 10 third sample after 19 days. The samples thus taken were treated according to the directions of the tests indicated above and the decomposition rate was determined by gas chromatography.

The following results were obtained in this way:

15 sample after 7 days : 49.3% degraded

sample after 14 days : 69.1% degraded

sample after 19 days : 82.9% degraded Surprisingly the dibromobenzyltoluene, which is a preferred compound of the invention was biologically

20 degraded by more than 80%.

b) Combustion Test

A combustion test was carried out according to "the 6th Luxemburg Report on the requirements and tests of non-flammable fluids for hydraulic power transmission and

25 control."

By this means it was shown that dibromobenzyltoluene has a better combustion behaviour than tetrachlorobenzyltoluene or polychlorinated biphenyl for example.

c) Investigation of corrosiveness

30 The corrosiveness of dibromobenzyltoluene was investigated according to the methods of the 6th Luxemburg Report mentioned above.

This involved immersing the metals steel, copper, brass, aluminum, cadmium and zinc as well as the metal

35 pairs copper-zinc, steel-aluminum, steel-cadmium and aluminum-zinc to two-thirds of their length in the fluid to be examined (dibromobenzyltoluene) and were left therein for 28 days at a temperature of 35°C.

This experiment showed that in the case of all of the test pieces the differences in weight resulting from corrosion was less than 1 mg (the permissible difference in weight was 20 mg).

d) Compatability with Sealing Elements

For the investigation of the compatability with sealing elements, a sealing element made from sealing material 83 FKM 575 (Viton) was submerged in the fluid under investigation and was kept for 21 days at 60°C, 80°C, 100°C , 120°C and 150°C. Then the variation in volume of the sealing element and the variation of its Shore hardness were determined.

This investigation showed that the preferred bromine-containing benzyltoluene derivative of the invention, namely dibromobenzyltoluene used as such and also in prepared hydraulic fluids had a particularly good performance, in that it produced a volume alteration in the sealing of between less than 1 and 2% and a variation in the Shore hardness of -3 degrees. The permissible volume change and variation in the Shore hardness in this testing method is up to 20% and from -10 degrees, respectively. Comparative tests using polychlorinated biphenyls and tetrachlorobenzyltoluenes showed values of volume change of 40% at a testing temperature of 150°C.

In the case of these known products, care must be taken when using them as hydraulic fluids not to exceed temperatures of 100°C because then the sealing material is attacked to too great an extent so that it can be damaged. e) Investigation of Pyrolysis

Dibromobenzyltoluene was pyrolysed at temperatures between 150 and 700°C in order to see if highly toxic decomposition products are produced. The operation of the test was carried out according to EPA - method No. 613.

Upon analysis with GCMS no highly toxic dioxin or dibenzofuran (tri - and tetrabromo) could be determined within the detection limits (0.5 ppb).

f) Investigation of the Viscosity-Temperature Relationship

The hydraulic fluid according to the invention of example 2 below showed the following viscosity-temperature relationships:

- 20°C 8320 cSt

10 0°C 430 cSt

+ 20°C 83 cSt

+ 50°C 21. cSt

+100°C 6.6 cSt

A hydraulic fluid consisting of tetrachlorobenzyl-

15 toluene had the following relationships:

- 20°C solid, not measurable

0°C 9730 cSt

+ 20°C 320 cSt

+ 50°C 25 cSt

20 +100°C 4 cSt

The folowing examples 2 to 8 provide further description of the invention and are concerned with the formulation of non-flammable hydraulic fluids (examples 2 to 6) and insulating fluids (examples 7 and 8).

25 Example 2

Formulation of a non-flammable hydraulic fluid:

93% Dibromobenzyltoluene

6% Viscosity index enhancer (polymethacrylate) 0.5% Corrosion inhibitor (barium sulfonate)

30 0.5% Antiwear additive (zinc dialkyldithiophosphate) Example 3

Formulation of a non-flammable hydraulic fluid:

75% Dibromobenzyltoluene

23% Isopropyl triphenylphosphate

35 1% Corrosion inhibitor (alkylsulfamidocarboxylic acid) 1% Acid acceptor (epoxide resin)

Formulation of a non-flammable hydraulic fluid:

88% Dibromobenzyltoluene

10% Butile stearate

1% Corrosion inhibitor (fatty acid alkanolamide) 0.5% Oxidation Stabilizer (amine derivative) 0.5% Antiwear additive (zinc dialkyldithiophosphate) Example 5

Formulation of a non-flammable hydraulic fluid:

10 65% Dibromobenzyltoluene

25% Monobrominated benzyltoluene

9% Viscosity index enhancer (polyisobutylene) 1% Corrosion inhibitor (stearin amine derivative) Example 6

15 Formulation of a non-flammable hydraulic fluid:

50% Dibromobenzyltoluene

45% Monobrominated xylylxylol

4.5% Viscosity index enhancer (polyisobutylene) 0.5% Corrosion inhibitor (stearin amine derivative) 20Example 7

Formulation of an insulating fluid for electrical equipment:

99.5% Dibromobenzyltoluene

0.3% Corrosion inhibitor (stearin amine derivative) 25 0.2% Epoxy resin

Formulation of an insulating fluid for electrical equipment:

50% Dibromobenzyltoluene

30 49.5% Monobrominated benzyltoluene

0.3% Corrosion inhibitor (stearin amine derivative) 0.2% Epoxy resin