NO171973B - MIXING BASED ON POLYPHENYLMETHANES AND THEIR APPLICATIONS AS DIELECTRIC - Google Patents

Abstract

Mixtures of benzyltoluene, benzylbenzene and their higher homologues, the said mixtures optionally containing triphenylmethane, ditolylphenylmethane, tolyldiphenylmethane and their higher homologues. These mixtures are prepared by chlorinating a mixture of toluene and benzene which is then subjected to the action of an inorganic halide.

Description

The present invention relates to mixtures based on polyphenylmethanes and their use as dielectrics. The invention relates more particularly to mixtures of mono- and dibenzyltoluene, mono- and dibenzylbenzene and may contain triphenylmethane, ditolylphenylmethane, tolyldiphenylmethane or their higher homologues.

EP-PS 259,798 describes mixtures of monobenzyltoluene of ethylbiphenyl and/or 1-1 diphenylethane with other biphenyls or other diphenylmethanes with more than 17 carbon atoms.

EP-PS 262,456 describes mixtures of monobenzyltoluene and a diphenylmethane which is substituted with alkyls, the overall structure having between 15 and 17 carbon atoms.

EP-PS 172,537 describes isomeric mixtures of benzylbenzene.

EP-PS 282,083 describes mixtures of monobenzyltoluene and ditolylmethane.

All these described mixtures are obtained by addition or coupling reactions of pure reactants which then necessitate difficult separations.

EP-PS 136,230 describes mixtures of monobenzyltoluene, dibenzyltoluene and ditolylphenylmethane which can be used as dielectric fluids. The patent also describes a method for obtaining these mixtures in a very simple way.

New mixtures based on polyphenylmethanes have now been found which have better dielectric properties than the known technique. Another aim of the invention is to provide mixtures which can be used at low temperature.

Another object of the invention is to provide compositions which are easy to prepare.

The invention thus relates to a mixture based on two oligomers Aj and A2 such that: Aj is an isomer or a mixture of isomers with the formula: where nj and n£ - 0, 1 or 2 provided that nj + n£ is less than or equal to 3 and R means hydrogen; A2 is an isomer or a mixture of isomers with the same general formula as Ai except that R means methyl and ni and ii2 are replaced by and q2 and have the same meaning, and the mixture is characterized by at least one of the oligomers Ai and A2 comprising an isomer with three benzene nuclei. The oligomer A2 can be, for example, metabenzyltoluene or a mixture of two isomers of benzyltoluene or a mixture of three isomers of benzyltoluene. It can also be a more special isomer with = 1 and ^2~ °» for example 3,5-dibenzyltoluene or a mixture of such isomers such that qj - 1 and q2 - 0 or a mixture of isomers such that qj_ « 0 and <q>2 - 1. A2 can further be a mixture of isomers where q^ and q2 have several meanings, for example a mixture consisting of 64 wt-# of dibenzyltoluene, 22 wt-# of a mixture of isomers so that qi and q£ - 1» 10 wt-# of an isomer mixture such that Ql + q2 - 2 and 4 wt-# of an isomer mixture such that q^ + q2 - 3. It can further be any other combination of these isomers or isomeric mixtures described above.

The same applies to the oligomer A^ which is thus an isomer or a mixture of isomers of benzylbenzene or its higher homologues. The mixture according to the invention is such that at least one of the oligomers A1 or A2 is an isomer that has at least 3 benzene nuclei in its structure or a mixture of isomers with 3 benzene nuclei, or a mixture comprising at least one isomer or isomers with three benzene nuclei.

The product according to the invention can be a mixture of any oligomer A^ and the oligomer A2 either in the form of dibenzyltoluene, i.e. one or isomers where qj - 1 and q2 = 0 or tolylbenzylphenylmethane, i.e. an isomer or isomers where qi° 0 and qg - 1.

Preferably, the product according to the invention is a mixture comprising one of the following combinations of the oligomers A^ and A2 :

a) Ai such that = ng = 0

A2 such that + <q>2 = 1

b) Ai such that n^ + n2 = 1

A2 such that qj = <q>2<=> 0

c) Ai such that n^ + n2 = 1

A2 such that q^ + <q>2 = 1

Although the proportions of A1 and A2 may be any, the amount of A2 is preferably greater than the amount of A2 and is preferably between 60 and 80% by weight of the total amount of the total amount of A2 and A2.

The invention also relates to a mixture based on the two oligomers A^ and A2 and this is characterized by the fact that it additionally comprises at least one oligomer selected from among the oligomers B]_, B2 and B3 as follows: Bi is an isomer or a mixture of isomers with the formula:

there:

n'j, n"! and n4 - 0, 1 and 2.

n' 2, n"2, <n>3> n'3 and n5 - 0 and 1,

provided that n'i + n"i + n'2 + n<n>2 + n3 + n'3 + n4 + n5 is less than or equal to 2;

R 1 and R 2 are hydrogen;

B2 is an isomer or a mixture of isomers of the same general formula as Bj except that R1 and R2 are methyl and the coefficients n are replaced by q and have the same meaning; and

B3 is an Isomer or a mixture of isomers of the same general formula as Bi except that Ri and R2 are different and mean hydrogen or methyl and the coefficients n are replaced by r and have the same meaning.

The oligomer Bj can be triphenylmethane in its simplest form. It can also be an isomer and exactly benzylphenyl-diphenylmethane, that is, n' 1 » 1 and with all other coefficients equal to 0 or a mixture of numerous isomers of this product. Bi can also be a mixture of isomers where the coefficients n have several meanings such as, for example, that 72 wt-£ of Bi consists of isomers where the sum

n'i + n"l + n'3 + n3 + <n>'2<+> n<n>2 + n4 + n$ - 0; 21% by weight consists of isomers where the above-mentioned sum is 1 and the rest consists of isomers where the sum is 2. Bi can also be an isomer or a mixture of isomers represented by any exact spectrum for the coefficients n. It can also be a mixture that is a combination of two or more mixtures as mentioned above. The oligomers B2 and B3 are defined in the same way.

Particularly advantageous mixtures consist of Ai, A2 and B2. Among these mixtures, the following mixtures are preferred:

a) Ai such that n^ = n2 = 0

A2 so that 60-90 wt-# of A2 consists of isomers with n^ +

n2 = 0

B2 equal to any.

b) Ai such that more than 50% by weight of Ai consists of isomers with nl + n2 = 0

A2 and B2 as under a).

Among the mixtures based on Ai, A2 and at least one of the oligomers Bi, B2 and B3, those comprising 5 oligomers Ai, A2, Bi, B2 and B3 are particularly advantageous and are very unexpectedly easy to fabricate.

The invention also relates to a mixture consisting of the mixture Ai, A2, Bi, B2.

All the mixtures described can be used as dielectric fluid, especially in capacitors. All of the compositions can be purified, for example by contacting them with decolorizing earth, a bentonite or an equivalent product until a sufficiently high resistivity is achieved and generally they are purified according to conventional techniques for purifying liquids for dielectric use. One can also add to the mixtures according to the invention common additives for liquids for dielectric use such as epoxides, antioxidants of the di-tert-butyl paracresol type or derivatives of anthraquinone. The invention also relates to synthesis processes for all these mixtures.

The oligomers A^, A2 can be prepared by reacting benzyl chloride C5H5CH2CI with toluene for A2 and with benzene for A^. As regards the oligomers B^, B2 and B3, can these be prepared by reacting benzylidene chloride C^^CHCl»? with benzene, toluene, benzyl chloride and the oligomers A^ and A2.

Benzyl chloride and benzylidene chloride are known products. For example, one can carry out a radical chlorination of toluene followed by a distillation to separate C6H5CH2C1 and C6H5CHC12.

Then, once the different oligomers A and B have been obtained, it is sufficient to mix them to obtain the compositions of the invention.

A particularly suitable method for obtaining the mixture of oligomers A2 and B2 is described in EP-PS 136,230 and consists in a first step of reacting chlorine with toluene by radical reaction in the presence of free radical generators and in a second step of subjecting the reaction product from the first one to influence of a mineral halide or a mineral acid.

As regards the method for producing A-^ + B^, this is carried out by: a) reacting chlorine with a mixture of benzene and toluene by radical reaction in the presence of a free radical generator;

b) unreacted toluene is removed; and

c) subjecting the obtained product to the influence of a

mineral halide or a mineral acid.

The radical chlorination of the mixture of benzene and toluene is generally carried out at a temperature between 50 and 110°C and preferably between 70 and 100°C. It is preferably carried out so that no more than 10 to 40%, expressed on a molar basis, of the toluene used is converted into the corresponding chlorinated derivative. As regards the free radical generator, one can use either a photochemical initiation or a chemical initiator; among chemical initiators, mention must be made of azo compounds such as azodiisobutyronitrile or also azodivaleronitrile and further lauroyl peroxide. The amount of chemical initiator used is generally between 0.05 and 3% by weight calculated on the toluene used, preferably between 0.1 and 1.5%.

It has been surprisingly established that if the mixture of benzene and toluene contains at least 15 mol-# toluene and preferably 20-30%, no chlorination of benzene occurs.

Toluene is then removed, for example by distillation using one or more columns and recycling benzene which may exit together with non-chlorinated toluene in the reaction medium containing chlorinated toluene.

The reaction medium obtained during the previous step, i.e. a mixture of CfcH6, C6H5CH2C1 and C6H5CHC12 is then subjected to the influence of a mineral halide or also a mineral acid. This reaction takes place in practice at a temperature between 30 and 110°C, preferably between 50 and 100°C. Among the mineral halides, one can use iron (III) chloride, antimony trichloride, titanium tetrachloride or also aluminum chloride in amounts by weight in relation to reactants which are usually between 50 ppm and 1%, preferably between 100 ppm and 0.5%. Mineral acids can also be used, for example sulfuric acid with a weight concentration of between 70 and 95 H>. It is also possible to use zeolites or certain mineral oxides.

A variant of the method at the level of this second step consists in pouring the reaction mixture from the first phase into a sump of benzene of benzene and a mixture of oligomers according to the invention, containing mineral halide or mineral acid in the form of a solution or dispersion; this variant is particularly interesting for continuous execution of such a process as it is clear that the process can be carried out both continuously and discontinuously.

It is recommended, after distillation of excess benzene, and proceed to the elimination of mineral halide or mineral acid by any known technical means such as washing with water, neutralization, drying.

A]_ + B]_ can also be prepared according to a variant of the method described above where benzene is introduced after chlorination of toluene.

This procedure is carried out by:

a) chlorine is reacted with toluene by a radical reaction in the presence of a free radical generator,

b) unreacted toluene is removed; and

c) benzene is added and the product obtained is subjected to reaction

an influence of a mineral halide or a mineral acid.

The implementation of the method is the same as in the above-mentioned case where a mixture of toluene and benzene is chlorinated, however, the elimination of toluene is much easier because it is the most volatile product.

One does not go outside the scope of the invention when replacing steps a) and b) with a synthesis of the mixture CfcHsCEtøCl and C6H5CHC12.

A method for producing the mixture of oligomers Ai and A2 is carried out by bringing benzyl chloride into contact with benzene and toluene in the presence of a mineral halide or a mineral acid.

This reaction takes place under the same conditions as described above under step c) in the method for producing Ai + B^.

Ai + A2 can also be prepared according to a variant of the above-mentioned method by: a) reacting chlorine with toluene and benzene in the presence of a free radical generator;

b) removing benzylindene chloride; and

c) one subjects the obtained product to the influence of

halide or a mineral acid.

The implementation corresponds to the above-mentioned representations. For step b) it is advantageous to work by distillation, for example by recovering the light fraction in the mixture obtained under a). This light fraction consists of benzene, toluene and benzyl chloride, it is sufficient to add this

In a mineral halide or a mineral acid or

II a product containing this halide or this

acid.

Furthermore, step a) can be carried out without benzene and by adding it in step c). You can also add toluene during step c).

Furthermore, a method for producing a mixture of oligomers Ai, Ag, Bi, B2 and B3 is described by: a) reacting chlorine with a mixture of benzene and toluene by radical reaction in the presence of a free radical generator; b) then subjecting the preceding reaction product to the action of a mineral halide or a mineral acid.

As before and provided that the benzene-toluene mixture contains at least 15 mol-# toluene, no chlorination of benzene occurs. The implementation corresponds to that of the previous processes.

The following examples shall illustrate the invention.

Example 1

The tests consist of 1 subjecting capacitor models to accelerated aging tests at elevated voltage and temperature.

The essential thing about the tests is the number of collapsed capacitors. In certain cases, the aging duration is short and the measurement of the firmness of non-broken capacitors during the test provides supplementary information with a view to the deterioration of the insulation.

1. Test on mixed capacitors.

For this test, two series of 10 capacitors have been made, comprising 2 layers of polypropylene film with a thickness of 12 pm and a paper layer with a density of 1.0 and a thickness of 12 pm.

These two series of capacitors are impregnated, one with an oligomer A2 such that 75 wt-# is benzyltoluene (q^ = q2 = 0) and 25 wt-# of the isomers such that q^ + q2 = 1 and containing diglycidyl ethers of bisphenol A in shares of one part per 100 parts A2, the other with a mixture of A^ and A2 such that:

a) A2 represents 70 wt-# of A^ + A2; and

b) A^ is formed by 70 weight-# isomers so that n^ = n2 = 0 and

30 wt-# isomers such that n^ + n2 = 1.

1.1. Lifetime

After impregnation and thermal formation, the capacitors were subjected to aging at 85°C under 2700 volts (75 V/pm) for 553 hours. After this first aging without failure being observed, the sample was continued under 3000 volts (83.8 V/pm) to tighten the conditions.

At this point, after 4400 hours of aging, the following results were obtained:

These results are in favor of the mixture + Ag.

1.2. Developments of tanS.

TenS for the capacitors is measured after 535, 1460 and 4400 hours of ageing. The following results are achieved:

TanS for capacitors impregnated with the mixture A^ + Ag is significantly smaller than that of the capacitors impregnated with A2, which shows that the deterioration is less significant.

II. Tests on total film capacitors.

For this sample, three series of 10 capacitors comprising two rue polypropylene film layers with a thickness of 13.5 pm are produced.

Two series are impregnated with the oligomer Ag as above, one series is impregnated with the mixture A^ + Ag as above.

2.1. Lifetime.

After impregnation and thermal formation, the capacitors are subjected to aging at 90" C under 2400 volts (88.9 V/pm) for 500 hours.

The following results are achieved:

These results show a slight difference in favor of the mixture A^ + Ag.

2.2. Development of the breakdown voltage.

To confirm these results, the breakdown voltage is measured for the capacitors that are still alive at the end of the aging test. The same measurement carried out on new capacitors gives a value of 11.5 kV. Any deterioration of the insulation during aging results in a reduction in firmness.

The following results are achieved:

capacitors impregnated with A2 : 6.6kV capacitors impregnated with A-^ + A2 : 9.4 kV

These results show significantly that the deterioration of capacitors impregnated with A^ + A2 is much less.

Example 2 - Synthesis of an oligomer Aj.

In a 6 liter reactor equipped with a rotary tube, a reflux cooler, a nitrogen injector and a dropping funnel, 4212 g corresponding to 54 mol of benzene and 1 g of FeCl3 are charged. The mass in the reactor is brought to 65°C under nitrogen. Using the dropping funnel, 759 g corresponding to 6 mol of benzyl chloride are added over the course of 4 hours. The reaction medium is then stirred for one hour and 0.25 g of FeCl3 is added. The reaction medium is then kept for two hours at 70°C under nitrogen purging. The amount of hydrochloric acid released is 5.95 mol. Unreacted benzene is then removed by simple distillation. 873 of crude polyphenylmethane is then treated with 1 # anhydrous Na 2 CH 3 for 3 hours at 275°C with stirring. After treatment, the product is subjected to a distillation in a column with a height of 30 cm filled with glass springs under a negative pressure of 1 mm HG.

The fraction of compounds with 2 aromatic rings passes at 85 to 95°C. The fraction consisting of three aromatic rings distills over at 170-200°C.

The fraction consisting of 4 aromatic rings distills over at 260-280°C (after removing the distillation column).

The rest represents 5.8% added product. The distillation fractions are mixtures and make up 94 wt-# of added product. One obtains an oligomer A^ whose weight composition is as follows:

nine and ng =0 66.5

n-L = 1 n2 = 0 27

m and n2 = 1 6.5%

The properties are as follows:

Crystallization point = + 3°C

Viscosity at 40°C = 3.4 cP

Viscosity at 20°C = 5.8 cP

Density at 40°C = 1.001

Density at 20°C = 1.012

Example 3: synthesis of the mixture A^ + B^.

In an apparatus similar to that in example 2, 1266 g corresponding to 9.61 mol benzyl chloride and 1266 g corresponding to 0.306 mol benzylidene chloride are placed in the dropping funnel, which is obtained by photochlorination of toluene (molar ratio toluene:chlorine = 4) and separation of unreacted toluene by distillation.

This product is reacted under the same conditions as in example 2 with 3900 g corresponding to 50 mol of benzene and 1 g of FeCl3. Recovered hydrochloric acid is 9.99 mol. The product obtained after distillation of unreacted benzene amounts to 1304 g. This is treated as in example 1 with sodium carbonate and then subjected to the same distillation. The distillation residue makes up 14.2% of the added product. The fractions are mixtures and make up 85 io of added product. The product thus obtained is of the oligomer mixture type of A^ and B^.

This consists, by weight, of:

- £53:

* the oligomers A^ where n^ and n2 = 0

- £31:

<*> the oligomers A^ where n^ = 1 and n2 ■= 0

* the oligomers B^ where n'i = n2 = n"i = n"2 = n3 = n<*>3 = n4 = n5 = 0

- 4 p.m

* the oligomers A^ where n^ = n2 = 1

<*> the oligomers B^ where n'i + n'2 + n"i + n«2 + n3 + n'3 + n4 + n5 = 1

The properties are as follows:

Crystallization point : -15°C

Viscosity at 20°C : 8.1 cP

Density at 20°C: 1.019

Example 4: Preparation of A^ + A2 + B^ + B2 + B3.

In a 1 liter reactor equipped with piping, condenser, feed pipe for chlorine and a Philips TLADK lamp of 30 watts placed externally, put 390 g corresponding to 5 mol of benzene and 460 g corresponding to 5 mol of toluene; 78.1 g corresponding to 1.25 mol of chlorine are then added and the whole is kept at 85°C for 1 hour. The amount of hydrochloric acid that is released is 1.15 mol. Chromatographic analysis shows that benzene is completely inert during the chlorination. The mixture contains 16# benzyl chloride and 0.52% benzylidene chloride by weight.

The reaction medium is placed in a pouring funnel and fed over the course of 1 hour to a 1 liter reactor equipped with piping containing 15.3 g corresponding to 0.166 mol toluene, 12.95 g corresponding to 0.166 mol benzene and 0.15 g FeCl3 at a temperature of 80° C. The whole thing is then kept for 1 hour at 80° C with a purge of nitrogen. The amount of hydrochloric acid released is 1.1 mol.

The product obtained after distillation of benzene and unreacted toluene amounts to 180 g. This is treated as in example 1 with sodium carbonate and subjected to the same distillation. The distillation residue makes up 2.76% of the product used. The distillation fractions are mixed and made up! 97.1% by weight of used product. The product thus obtained is of the type of mixture of the oligomers A^, Ag, Bj, Bg and B3.

71.1 it oligomer A^ + Ag where n^ and ng = 0

Ql and <q>2 = 0

- 24.3 *:

* oligomer Aj + Ag where n^ = 1 and n2 = 0

q± = 1 and qg = 0

<*> the oligomers B^ + Bg + B3 so that all the coefficients n, p and r are zero - 4.6 *:

<*> the oligomers A^ + Ag where n^ = ng = 1

<q>j <=><q>2 <=><1>

<*> the oligomers B-^ + Bg + B3 so that the sum of all the coefficients n is equal to 1, the sum of all the coefficients q is equal to 1 and the sum of all the coefficients ri is equal to 1.

j

1 the oligomer A^ + Ag is weight advantage none against Ag 85 : 15 (determined by gas phase chromatography) for the value n^ and ng equal to 0. I

The properties are as follows: Crystallization < at - 32°C

Viscosity at 20°C = 6.7 cP <1>

Viscosity at 20°C = 0.998

Example 5

Some mixtures of product A^ from example 2 with a product Ag + Bg produced according to the technique described in EP-PS 136,230 were made and where the weight composition in relation to the general formula is as follows:

75% oligomeric Ag where q^ and qg = 0

- 23 St:

* oligomer Ag with q^ = 1 and ng = 0

* oligomers Bg as q'x = <q>'2=<q>"i=<q>"g<=q>3<=q*>3 <+q>4 <+q>5 <=>< 0>

- 2 ten

* the oligomers Ag where qi = qg = 1

* oligomers B2 as q'i+<q>'2<+q>"i<+q>"<g+q>3<+q>'3<+q>4<+q>s = 1

The amount of oligomers Bg:

q'i <=><q>'2 <=> <Ti <=><q>"2 - «13 - <q>'3 <=> <u - «15 <=><0>

is 2.5 $6, determined by chromatography analysis.

The crystallization point is below -40°C. The viscosity at 20°C is 6.5 cP and the density is 1.006.

Claims (8)

1. Mixture based on two oligomers A^ and Ag such that: - Ai is an isomer or a mixture of avi isomers with the formula: where nj^ and ng are equal to 0, 1 and 2 provided that n^ + n2 is less than or equal to 3 and R means hydrogen; and j Ag is an isomer or a mixture of isomers with it same general formula A except that R! means methyl and ni and ng are replaced by and qg and have the same meaning, characterized in that at least one of the oligomers A^ and Ag comprises an isomer with three benzene nuclei. 2. Mixture according to claim 1, characterized in that the oligomer A^ is such that n^ - ng - 0 and the oligomer Ag is such that q^ + qg - 1. 3. Mixture according to claim 1, characterized in that the oligomer Aj is such that n^ + n2 - 1 is such that qi =» q2 - 0. 4. Mixture according to claim 1, characterized in that the oligomer A^ is such that n^ + n2 = 1 and the oligomer Ag is such that <q>i + <q>g - <1.> 5. Mixture based on two oligomers Ai and Ag, characterized in that it additionally comprises at least one oligomer selected from the oligomers Bj^, Bg and B3 as follows: Bi is an isomer or a mixture of isomers with the formula: where: n'i, nM! and n4 - 0, 1 and 2. n'g, n"2, <n>3, n'3 and n5 - 0 and 1, provided that n'j + n"i + n'g <+> n"g <+> n3 + n'3 + n4 + n$ is less than or equal to 2; R 1 and R 8 are hydrogen; Bg is an isomer or a mixture of isomers of the same general formula as B^ except that Rj and Rg are methyl and the coefficients n are replaced by q and have the same meaning; and B3 is an isomer or a mixture of isomers of the same general formula as B^ except that R^ and Rg are different and mean hydrogen or methyl and the coefficients n are replaced by r and have the same meaning. 6. Mixture according to claim 5, characterized in that it comprises the oligomers A^, Ag and Bg. 7. Mixture according to claim 5, characterized in that it comprises A^, Ag, B^, Bg and B3. 8. Use of mixtures according to any one of claims 1-7 as dielectric liquids.