NL8001016A - USE OF METHYL ALCOHOL AS A STABILIZER AGAINST THE RISK OF EXPLOSION IN A DICHLOROMETHANE DEGREASANT FOR METAL SURFACES. - Google Patents

Description

* - -f -1- 21196 / JF / ts

Applicant: Chemische Werke Kluthe GmbH + Co., Heidelberg, Federal Republic of Germany.

Short designation: Use of methyl alcohol as an anti-explosive stabilizer in dichloromethane 5 degreasing agent for metal surfaces.

The invention relates to the use of an anti-explosive stabilizer in a metal surface degreaser, in particular for those of aluminum and aluminum alloys.

It is known that in the degreasing of aluminum or aluminum alloys with certain chlorinated hydrocarbons, for example with 1,1,1-trichloroethane or with dichloromethane, explosions can occur which are based on a polycondensation and dechlorination of the respective chlorinated coal hydrogen.

Reactions may occur in the course of which hydrogen chloride is split off from the chlorine hydrocarbons, which further converts finely divided aluminum into aluminum chloride.

This aluminum chloride, in turn, acts as a catalyst for Friedel-Kraft reactions, in which exothermic condensation takes place while hydrogen chloride is split off. Since the resulting chlorine hydrogen substance forms new aluminum chloride, the reaction and thereby also the generation of reaction heat accelerate more and more, until eventually the temperature is thus high to initiate the strongly exothermic dechlorination of the condensation products by finely divided aluminum.

It is already known to contact metals with methylene chloride, which methylene chloride is stabilized to prevent such reactions (German Auslegeschrift 2M 08 702). A truly complex mixture of nitrogen and oxygen-containing organic compounds with optional methyl alcohol is used, which consists largely of expensive components.

The present invention is therefore based on the technical problem of stabilizing the dichloromethane which is useful in itself as a degreasing agent for metal surfaces and in particular for aluminum and aluminum alloy surfaces in such a way that the degree of stabilization with with respect to the prior art, at the same time, greatly simplifying the nature of the additives and limiting them to cost-effective substances.

In assessing the applicability of stabilized 800 1 0 16 I--2- 21196 / JF / ts degreasers, three main points of view are decisive: 1. It should be investigated whether the stabilizer also distills out during the distillation of the mixture and whether its activity in the distillate is maintained unchanged.

2. The activity of the stabilizer should not be limited to preventing the formation of the catalytically highly active aluminum trichloride, but the stabilizer should render harmless large amounts of aluminum trichloride already present.

10 3 · The stabilizer, unlike other aliphatic and aromatic substances, which may have a double bonding character, must also retain the stabilizing effect in order to prevent any exothermic reaction.

Surprisingly, it has therefore been found that the use of methyl alcohol to accompany small amounts of diisopropylamine and / or benzyl ethylamine and / or triethylamine for the dichloromethane degreaser for metal surfaces, in particular aluminum and aluminum alloys, on excellent such a stabilizer.

A recommended mixing ratio is that of 6-12 wt.

20% methyl alcohol, 88-94 wt. % dichloromethane and each time around 0.01 wt. % di-isopropylamine, benzylethylamine and triethylamine.

A preferred embodiment of the stabilized degreasing agent according to the invention is characterized in that it consists of around 94 wt. % dichloromethane, around 6 wt. % methyl alcohol and each from around 0.01 wt.

25% di-isopropylamine, benzylethylamine and triethylamine exist. A 98-100% dichloromethane can normally be used as dichloromethane.

It is true that the aforementioned German Auslegeschrift No. 24 08 702 also gives an indication with regard to an extra content of methyl alcohol, in very small quantities. Since this. however, as expressly suggested as optional when supplementing a mixture of several other substances, this prior art cannot support the idea of attempting just this and only attempting it with the addition according to the invention.

A special feature of the surprisingly simple shining invention lies in that not only a technical improvement, but at the same time a considerable cost-saving factor is achieved.

With regard to the suitability testing of stabilized 800 1 0 16 t *> -3- 21196 / JF / ts degreasers, the following should generally be noted first: A), Normal testing with aluminum flakes.

1st test: 100 g of degreasing agent + 100 g of toluol + 18 g of Al 5 + 0.7 g of ALC13 vaulted under reflux for 18 hours.

2nd test: The same test with the addition of 1 g zinc stearate.

3 3rd test: The same test, but with the addition of 10 cm oleic acid.

4th test: Separation of a sample of the delivered product into three fractions with an equal volume proportion in a simple distillation apparatus. Each fraction is then treated as in test 1.

B). Testing with aluminum powder.

The same tests as under A, but using powdered aluminum.

15 C). Details of the tests.

Aluminum flakes: Aluminum flakes, medium, (plates with a diameter of 0.5 to 1 mm).

Aluminum Chloride: Aluminum chloride sublimated anhydrous, only, powdered, no scraps of material.

Toluol: Toluol (98%).

Zinc Stearate: Zinc Stearate.

Oleic Acid: Pure oleic acid.

3

Equipment: 250 cm with Claisen attachment, Mohrscher cooler and drying tube, heating in an air bath.

25 So-called fractional distillation in simple distillation equipment without column and with descending cooler.

The tests were interrupted overnight.

In the following, the particular suitability of the degreaser stabilized according to the invention is now indicated on the basis of test results.

3 100 cm metal degreaser, namely unstabilized. 3 dichloromethane was mixed with 100 cm toluol and boiled at reflux with 18 g aluminum flakes (leaves with / 85 meter of 0.5 to 1 mm) and 0.7 g AlCl 3 "anhydrous". The test temperature was measured by an inserted thermo element Already after a few minutes a very violent spontaneous reaction with the development of large quantities of hydrogen chloride was obtained. The flask content was converted into a filthy black mass.

800 1 0 16 -4- 21196 / JF / ts -V ^

The similarly tested stabilized degreaser of the invention consisting of 93.97 wt. % dichloroethane, 6 wt. % methyl alcohol, n, 01 wt. % di-isopropylamine, 0.01 wt. % benzylethylamine and 0.01 wt% triethylamine. not discolored after an * 18 hour test. An exothermic reaction did not occur.

Under the same test conditions, addition of a) zinc stearate (1g) also does not cause discoloration

O

b) oleic acid (10 cm) has a weak yellow discoloration.

Violent exothermic reactions did not occur in any of these tests.

In a further test, the stabilized degreasing agent according to the invention was separated into three large fractions by distillation according to DIN 51 751.

Each fraction was individually mixed with the same volume of toluol and then its behavior was investigated with addition of aluminum flakes and 15 AlClg in the above-mentioned mixing ratios at boiling temperature. The boiling temperatures observed in the distillation were 37.5 ° C for the first fraction, 37.5 ° C for the second fraction and 37.5 ° C-50 ° C for the third fraction.

These tests show that the stabilized degreasing agent according to the invention is resistant in the presence of aluminum flakes (leaves with a diameter of 0.5 mm) and aluminum chloride both alone and mixed with aromatics. The protective effect of the stabilizer is retained even after distillation.

In the following, it will now be proved on the basis of numerically obtained comparative test results, that the invention increases the degree of stabilization with respect to the prior art. Result of the comparison study.

Test results of the chemical resistance of specially stabilized dichloromethane.

30 Comparison of two different stabilized dichloromethane mixtures.

A) Stabilization according to the invention: 93.97 wt. % dichloromethane 6 wt. % methyl alcohol.

35 B) Stabilization according to German Offenlegungsschrift 24 08 702, page 11, table II, no. 10.

Dichloromethane stabilized with: 80 0 1 0 16 -5- 21196 / JF / ts 0.0025 wt. % di-isopropylamine 0.005 wt. % n-methylpyrol 0.25 wt. % propylene oxide 0.125 wt. % butylene oxide 5 0.05 wt. % acetone 0.25 wt. % tert. amylene 0.05 wt. % methyl alcohol 0.20 wt. % methyl acetate.

. 1st test: 100 ml xlichloromethane, as stabilized under A and B, and 100 ml toluol and 18 g aluminum flakes and 0.7 g AlCl 2 were refluxed for 18 hours.

2nd test: The same test with the addition of 1 g zinc stearate.

3 3rd test: The same test, but with the addition of 10 cm oleic acid.

4th test: Separation of a sample of dichloromethane stabilized as under A and B, in three fractions with equal volume in simple distillation equipment. Each fraction is then treated as described above in the first test.

Test results: 20

Mixture A Mixture B

1st test after 18 hours no negative no negative symptoms 2nd test no negative no negative symptoms. phenomena 3rd test no negative no negative phenomena. 4th test after 18 hours after 30 minutes 1st fraction without finding * 30 2nd fraction without finding * 3rd fraction without finding * * After 30 minutes violent reaction (decomposition), the test solution was then pressed out of the flask by strong foam development.

Test 4 was repeated four times in both mixtures, the results were always the same.

-CONCLUSIONS- 800 1 0 16

Claims (5)

1. Use of methyl alcohol and small amounts of diisopropylamine and / or benzylethylamine and / or triethylamine as an anti-explosive stabilizer in a dichloromethane degreasing agent for metal surfaces, in particular for those of aluminum and aluminum alloys. The use according to claim 1, wherein the agent is from 6-12 wt. % 10 methyl alcohol, 88-9 wt. % dichloromethane and each from around 0.01 wt. % di-isopropylamine, benzylehtylamine and triethylamine exist. t, Use according to claims 1 and 2, wherein the agent consists of around 6 wt. % methyl alcohol, around 94 wt. % dichloromethane and each time from around 0.01 wt. % di-isopropylamine, benzylethylamine and triethylamine exist. Degreaser according to any of the preceding claims. Stabilizer according to any of the preceding claims. 800 1 0 16