DE1136695B - Stabilizing trichlorethylene against decomposition - Google Patents

Description

Stabilizing Trichlorethylene Against Decomposition The invention relates to relate to the use of a synergistic ternary mixture for stabilization of trichlorethylene against decomposition.

The invention was based on the object of a means for stabilizing to find trichlorethylene, which is particularly suitable for the decomposition to prevent this substance, which occurs especially when trichlorethylene is used for degreasing metals. This decomposition is prevented if the formation of free hydrogen chloride or the acid in theirs Formation in trichlorethylene is neutralized.

It is well known that trichlorethylene is an unstable chemical compound, which decomposes fairly easily when moisture, air, light and heat individually or act on them together.

The decomposition leads to the formation of hydrogen chloride, phosgene, Carbon monoxide, dichloroacethyl chloride and other products. The autocatalytic one in itself Decomposition, which leads to the formation of the undesired products mentioned, is still going on increased when the trichlorethylene with metal surface, z. B. made of steel and aluminum, is in contact.

While now on the one hand the decomposition of trichlorethylene in contact is conveyed with metal surfaces, on the other hand, the one formed during the decomposition takes effect Hydrogen chloride the metal surfaces in contact with trichlorethylene chemically, especially when the trichlorethylene is used in degreasing processes of metal surfaces as degreasing solvent in liquid and / or vapor phase is used.

Because the acid formed from the trichlorethylene touches the metal surfaces attacks, the formation of metal chlorides is caused, which in particular, if it is aluminum and / or iron chlorides, as decomposition catalysts act for trichlorethylene and thus the decomposition of this solvent continues increase, which is due to a more or less strong coloring due to the formation to recognize condensed tar products.

There are already several ways of stabilizing trichlorethylene known. A wide variety of organic substances were used, e.g. B.

Amines, imines, phenols, alcohols, ethers, esters, epoxy and heterocyclic Compounds, saturated and unsaturated hydrocarbons. The so far to stabilize Compounds used by trichlorethylene are characterized either by that they increase the decomposition products in proportion to their formation from the trichlorethylene able to remove, whereby the onset of a catalytic effect during the Decomposition of the solvent is prevented, or by preventing it from the start are able to suppress the degradation of trichlorethylene.

In the first case it is especially necessary to use the hydrogen chloride to the extent of its formation in trichlorethylene, and were used for this purpose Amines are used, which eliminate the acid with the formation of its hydrochloride. Even the use of epoxy compounds has been suggested because the oxygen-containing Oxyäthylenring in the molecule with hydrogen chloride with chlorohydrin formation, z. B. of 3-chloro-propanediol (1, 2) is able to react.

Since the chlorine in chlorohydrins is no longer in ionic form, it does not attack metals with which it means when degreasing metal surfaces Trichlorethylene comes into contact.

Protective substances of the second type mentioned, which are already used for stabilization of trichlorethylene were given, for example, phenols, which the trichlorethylene Capable of protecting against oxidative decomposition, since they react with oxygen and thereby converted into the corresponding quinoid compounds.

As mentioned above, amines and epoxy compounds act as acid acceptors, whereby they use the trichlorethylene used as a solvent at practically neutral or keep an alkaline p-value. The stabilizing effect of amines is for example in U.S. Patents 1925,602 and 2 096 735 and that of ethers and particularly of epoxies is in the U.S. Patent 2,371,645.

The stabilizing effect of phenolic compounds that are in the manner indicated above from that of the amines and ethers and in particular of the epoxides is in the U.S. Patents 1910 962, 2 008 680, 2 751421, 2 155 723.

Any of the above classes of compounds used for stabilization has already been used by trichlorethylene, has certain advantages and disadvantages with regard to the extent of the protective effect they have on the organic solvent confers.

Thus, in general, amines, when used alone, must the trichlorethylene are added in large amounts when the solvent is used as to be considered stable for practical purposes and to the strictest quality standards should correspond.

However, the use of amines in large amounts brings about the considerable The disadvantage is that this makes the solvent strongly alkaline, which is proves to be particularly harmful when the trichlorethylene is used for degreasing amphoteric metals, e.g. B. aluminum or zinc is used.

Phenols do, when used alone, and do one have a certain molecular structure, good protection against oxidation, but confer on the other hand the solvent has a low degree of acidity, and once in that The phenols offer solvents for some reason acid is formed no longer protection, as they are unable to bind acid.

After all, ethers, including the alkylene oxides, practice only one very limited stabilizing effect when not shared with others stabilizing compounds are used. So it became a synergistic one Combination of an epoxy and an amine as a stabilizer for trichlorethylene in U.S. Patent No. 2,797,250.

This stabilizer also has the disadvantage that a Sufficient stabilization of trichlorethylene can only be achieved if that Amine to the solvent in large amounts of more than 0.1%, based on the volume, is added, whereby the trichlorethylene receives an undesirably high alkalinity. The above-described disadvantages are eliminated by the stabilizing agent according to the invention avoided and achieved the goals already mentioned.

It has been found that a ternary mixture, the diisopropylamine, a phenol, e.g. B. Isopropylp-hydroxyanisole of the formula and an alkylene oxide, e.g. B. butylene oxide or propylene oxide, contains a synergistic stabilizing effect on trichlorethylene in practically neutral or only weak. able to exercise alkaline medium if it-dem. Solvent is added.

The synergistic stabilizing effect produced by this ternary mixture prevents the decomposition and thus the formation of acid in the trichlorethylene, if the latter of the separate or joint and long-lasting effect exposed to air, light, moisture and / or heat in the presence of metals is a decomposition that normally occurs when trichlorethylene is in liquid and vapor phase is used in processes for degreasing metals.

The above-mentioned ternary mixture contains diisopropylamine as the amine component, which is expediently used in the mixture in such amounts that by addition of the mixture to the trichlorethylene a content of 0.5 moles of amine per ton of trichlorethylene is achieved, which corresponds to approximately 0.005 percent by weight in the solvent.

This amount of amine can depending on the purpose for which the trichlorethylene should be used, be varied somewhat; For example, it can be 0.001 ° / o reduced or, if the trichlorethylene is used for degreasing ice surfaces should be used, up to 0, 1 percent by weight (about 10 moles), based on the Solvent, can be increased.

The phenol of the ternary mixture can after adding the mixture to the solvent therein in amounts of about 0.005 to 0.02 percent by weight will. These amounts, depending on the others, may be present in the solvent Auxiliaries somewhat decreased (down to 0.001 ° / 0) or increased (up to to 0.1%).

The alkylene oxide, especially propylene oxide or butylene oxide, is the solvent as a component of the ternary mixture advantageously in such amounts added that its content between 0, 01 and 1, 0, preferably between 0, 2 and 0.4 percent by weight, based on trichlorethylene, is. Depending on the purposes of use, for which the solvent is intended, and the various contained therein Auxiliaries can reduce the specified limit values by adding slightly lower or larger amounts of the alkylene oxide component can be modified. These other excipients can for example be ethers and alcohols and can be used as degreasing agents Serving trichlorethylene are added without the by the invention ternary mixture to adversely affect the synergistic effect produced.

The invention is to be illustrated by a series of examples, which illustrate the technical advantages achieved. In these examples worked with samples of trichlorethylene by various known methods were stabilized, these samples were made according to their stability properties evaluated, which was determined with the help of a 48-hour accelerated oxidation test as stated in USA.-Army-Navy-Aeronautical Specification MIL-T 7003 and Federal Specification OT-634a is described.

The aforementioned stabilization test consists essentially of the following Measures: 200 ml of trichlorethylene, which contain various stabilizers, are kept in a 500 ml Pyrex flask fitted with a reflux condenser for 48 hours heated to boiling, and gaseous oxygen saturated with water is with Using a blowpipe 3 mm in diameter at a speed of 10 to 12 bubbles per minute passed through the solvent in the flask; a steel strip with the dimensions 12.7 # 50.8 # 1.6mm will suspended in the vapor phase, while a steel strip with dimensions 6, 3 # 19 # 1.6 mm is introduced into the liquid phase; one under the vessel Matted 150 watt light bulb acts as a light and heat source at the same time. To The acidity of the trichlorethylene in the flask is determined in the experiment.

The results of two series of tests are shown in Tables I and II reproduced. The percentages of the various Auxiliaries are percentages by weight. The p-values were in the aqueous extracts of trichlorethylene determined after completion of the stability tests, with each Case the same ratio of water to trichlorethylene, namely a ratio 1: 1 was applied.

All experiments were repeated several times and the results averaged.

Test series 1 This test series comprises Examples I to 7, with examples 1 to 3 with individual stabilizing compounds, the examples 4 to 6 each with two components of the ternary mixture according to the invention and Example 7 carried out with the ternary mixture itself using butylene oxide became.

Table I. pH of the Trichloro Added to the trichlorethylene game stabilizers accelerate ten oxy- dation test 1 diisopropylamine 0.005 ° / 0.8 2 isopropyl-p-hydroxyanisole 0.01% 1.9 3 butylene oxide 0.21% 1.8 4 diisopropylamine 0.005 ° / 0 + Isopropyl-p-hydroxyanisole 0.01% 2, 4 5 diisopropylamine 0.005% + Butylene oxide 0.21% 2.2 6 butylene oxide 0.21% + Isopropyl-p-hydroxyanisole 0.1 ° / 0.4.7 7 diisopropylamine 0.005 ° / 0 + Isopropyl-p-hydroxyanisole 0.01% + Butylene oxide 0.21% 7.8 To carry out Example 7, a ternary mixture of 5 g of diisopropylamine, 10 g of isopropylp-hydroxyanisole and 200 g of butylene oxide was prepared.

About 0.65 g of the ternary mixture then became about 200 ml of trichlorethylene given and thus intimately mixed, making 200 ml of the stabilizer containing trichlorethylene with a weight of about 295 g. The example clearly shows the synergistic character of the mixture. It should be noted that the pH values with individual stabilizers or binary Trichlorethylene samples provided with stabilizer mixtures show a clear acidity as they are well below 7.0, whereas the p-value, which is associated with according to the ternary mixture of diisopropylamine, a phenol and an alkylene oxide of the invention stabilized sample also after the above-described, under stability tests carried out under severe conditions essentially above 7, 0, d. H. remains in the alkaline range.

Test series II Table II comprises Examples 8 to 14 from which the synergism within the compounds diisopropylamine, isopropyl-p-hydroxyanisole and propylene oxide.

The results are essentially the same as the previous ones Examples.

Table II pH of the Trichloro Ethylene added to the trichlorethylene game stabilizer after the accelerate ten oxy- dation test 8 diisopropylamine 0.005% 1.8 9 isopropyl-p-hydroxyanisole 0.01% 1, 9 10 propylene oxide 0.18% 1.9 11 diisopropylamine 0.005% Isopropyl-p-hydroxyanisole 0.01% 2.4 12 diisopropylamine 0.005% Propylene oxide 0.18% 2.3 13 propylene oxide 0.18% + Isopropyl-p-hydroxyanisole 0.01% / 0.5.9 14 diisopropylamine 0.005 ° / 0 + Isopropyl-p-hydroxyanisole 0.01% + Propylene oxide 0.18% 8.8 Test series III In Table III, the results of a third series of tests are given, which comprises Examples 15 to 21 and, in a manner similar to the preceding series of tests, results in the synergistic effect of a ternary combination which corresponds to that used in Example 7, with the exception that the Isopropyl-p-hydroxyanisole by ethyl-p-hydroxyanisole of the formula was replaced.

The results obtained in this series of tests confirm this obtained in the first row and show the pronounced synergistic effect, the of the ternary mixture due to the p-hydroxyanisole derivative present therein is caused.

Table III pH of the Trichloro Ethylene added to the trichlorethylene game stabilizer after the accelerated Oxidation test 15 diisopropylamine 0.005 ° / 0.8 16 Ethyl-p-hydroxyanisole 0.01% / 0.18 17 butylene oxide 0.21% 1.8 18 diisopropylamine 0.005 ° / 0 Ethyl-p-hydroxyanisole 0.01% 2.7 19 diisopropylamine 0.005 ° /, Butylene oxide 0.21% 2.2 20 butylene oxide 0.21% Ethyl p-hydroxyaniso] 0.01% 4.5 21 diisopropylamine 0.005 ° / 0 Ethyl-p-hydroxyanisole 0.01% + Butylene oxide 0.21% 8.8 From the examples given, the technical advantages can be seen by using a synergistic ternary mixture consisting of diisopropylamine, a phenol, eg. B. a p-hydroxyanisole, such as isopropyl-p-hydroxyanisole, or ethyl-p-hydroxyanisole, and an alkylene oxide, especially propylene oxide or butylene oxide, as stabilizers for trichlorethylene can be achieved. By using this synergistic ternary mixture according to the invention, it is possible to get by with very small amounts of amine and thus prevent an excessively strong alkaline reaction of trichlorethylene, which makes the latter only suitable for degreasing amphoteric metals such as aluminum and zinc, receives.

Trichlorethylene, which is used as a degreasing solvent, can also be used Alkenoxyde, if it is used in the synergistically effective ternary according to the invention Used in mixtures, add in such large amounts that they have a strong acid-binding properties Exercise effect in the trichlorethylene.

The phenolic compound and the synergism with the amine and the epoxy compound ultimately lead to a highly effective protection against oxidation.

It should be noted that the in the above reproduced Details, proportions and conditions depending on the examples listed the intended use and other circumstances can be changed without therefore to be outside the scope of the invention.

PATENT CLAIMS: 1. Use of a synergistic ternary Mixture consisting of diisopropylamine, a phenol and an alkylene oxide, for Stabilizing trichlorethylene against decomposition.

Claims (1)

2. Embodiment according to claim 1, characterized in that a Mixture of diisopropylamine in the amount of 0.001 to 0.1 percent by weight, one Alkyl p-hydroxyanisole in the amount of 0.001 to 0.1 percent by weight and one Alkylene oxide in the amount of 0.01 to 1.0 percent by weight, based on trichlorethylene, is used. 3. Embodiment according to claim 2, characterized in that as Alkyl-p-hydroxyanisole ethyl-p-hydroxyanisole or isopropyl-p-hydroxyanisole and as Alkylene oxide propylene oxide or butylene oxide can be used. Documents considered: Belgian patent specification no. 563 604.