IE49832B1 - Halogenated hydrocarbons stabilized against decomposition by water - Google Patents

Abstract

1. Halogenated hydrocarbon selected from the group consisting of methylene chloride, trichlorofluormethane and 1.1.1-trichloroethane, stabilized against decomposition by water, which comprises as stabilizer from 0.001 to 10% by weight of a tertiary amine of the formula RR**1 R**2 N with R being alkyl with 1 to 10 carbons and R**1 and R**2 , independent from one another, being isopropyl, butyl-(2), tertiary butyl or cyclohexyl.

Description

The present invention relates to the stabilization of halogenated hydrocarbons, especially those, which are liquid at room temperature, against decomposition in the presence of water. Halogenated hydrocarbons are used, inter alia, for extracting, degreasing or purifying metals and as solvents for other active ingredients. In many application fields the halogenated hydrocarbon is contacted with water which may cause a rapid or slow decomposition, with hydrogen halogenide being formed. Thus, present metals, for example tin plate, are corroded in many cases.

Hydrogenated hydrocarbons, preferably methylene chloride and 1,1,1-trichloroethane, but also trichlorofluoraiethane, are used as solvents for a variety of active ingredients, even for aerosol sprays. In most cases, the halogenated hydrocarbon, for example methylene chloride, is blended with other organic solvents, such as alcohols or aliphatic hydrocarbons.

In general, a stabilization of the halogenated hydro20 carbon in the absence of water, is easy or unnecessary. Insecticides or hair sprays, which contain methylene chloride, for example, are in general anhydrous.

An important advantage of the abovementioned halogenated hydrocarbons, besides their high dissolving power for many substances, is that they are classified as non-combustible, according to the legal regulations for compressed gas bottles that are binding within the EC zone. When using said halogenated hydrocarbons in spray formulations, especially in the presence of other combustible components, the safety requirements imposed on products which do not carry the sign combustible, can be met (the declaration of combustibility is obligatory in some countries if the proportion by weight of combustible components, calculated on the total spray, is 45 S or more).

A disadvantage of the abovementioned chlorocarbon solvents is their noticeable sensitivity to water. This also applies to many other halogenated hydrocarbons, - 3 especially to those which have only a low halogenation degree and contain less than 4 fluorine atoms in the molecule.

Even in the presence of small portions of water in an aerosol spray, pure methylene chloride, for example, especially on contact with metals, is. hydrolysed in a relatively short time (4 to 8 weeks, to such a degree that the metallic compressed gas bottle undergoes corrosion by the hydrogen chloride split off. A sufficient high portion of water may be introduced into the spray formula by blending the chlorohydrocarbon with ethanol having a strength of 96 % by volume. In most cases the content is also chemically attacked by the hydrochloric acid formed, thus making the whole content of the bottle unuseable.

Therefore many experiments have been carried out to stabilize halogenated hydrocarbons, especially the compounds methylene chloride and 1,1,1-trichloroethane, which are of special importance for the manufacture of aerosols, against hydrolysis by addition of inhibitors. Epoxides and/or secondary amines, for example, have been added to halogenated hydrocarbons, especially methylene chloride. From the toxicological point of view, however, epoxides have to be considered as unacceptable. Secondary amines, in the presence of nitrites, can lead to the formation of nitrosamines which may be cancerogenic. Another disadvantage is that the effect of the abovementioned stabilizers is slowly reduced and temporally limited because the stabilizers either react with the halogenated hydrocarbon or with the hydrogen halide formed therefrom. There have also been used N-methylpyrrole and N-alkylmorpholine in order to protect methylene chloride (in the absence of water) against decomposition by metals or metal salts (GB-PS 932,438). This is also valid for the known tertiary amines, such as triethylamine (US-patent application B 370,309).

Therefore it was necessary to stabilize halogenated - 4 hydrocarbons against hydrolysis by toxicologically unobjectionable compounds in such a way that their effectiveness is guaranteed for a long time.

Now it has been found that halogenated hydro5 carbons selected from methylenechloride and trichlorofluoromethane can be stabilized against decomposition by water, when adding thereto from 0.001 to 10 % by weight of a tertiary amine of the formula RR1R2N (I) wherein R is alkyl with from 1 to 10 carbon atoms 1 2 and R and R , independent from one another, are isopropyl, buty1-(2), tertiary butyl or cyclohexyl.

The alkyl radicals may be linear, branched or cyclic.

R is preferably alkyl with 1 to 4 carbon atoms, 15 especially the methyl or ethyl radical. Tertiary amines of the formula I, with R^ being identical with R are preferred because they can be manufactured more easily.

Preferred concentration ranges for the tertiary 20 amine, employed according to the invention, are 0.005 498 32 - 5 to 5 % by weight, specially 0.01 to 1 % by weight.

Furthermore, it has been found that the stabilizing effect of the tertiary amine is increased in the presence of an ether. As ethers there are preferably employed those compounds which only consist of C, H and 0 and which have no other reactive groups. Specially preferred are low molecular weight alkyl ethers or cycloalkyl ethers whose alkyl radicals contain from 1 to 6 c-atoms. Ether contents of more than 1 S by weight proved to be especially effective. Very favorable reactions showed 5- or 6-membered heterocyclic compounds, for example tetrahydrofuran, or unbranched dialkyl ethers with 2 to 6 carbon atoms, such as diethyl ether, dimethyl ether or methylethyl ether.

The invention also provides aerosol containers which contain a mixture of at least one halogenated hydrocarbon as hereinabove defined, liquid at room temperature and normal pressure, at least one liquefied aerosol propellant, which is gaseous at room temperature and normal pressure, as well as water. These containers may also contain other organic solvents and active ingredients. By the term active ingredient in the present application there are to be understood substances which cannot be considered as liquid halogenated hydrocarbons, organic solvents or propellants, which, however, are important for the use of aerosol formulation.

Examples hereof are perfumes, dyestuffs and binding agents (in lacquer sprays) and bactericides. These active ingredients, in general, have only a small influence on the hydrolysis of the halogenated hydrocarbons present. In sprays for producing low temperatures or in paint removers based on methylene chloride, for example, they are not necessary.

Of special interest are aerosol containers containing from 10-89.5 % by weight of liquid halogenated hydrocarbon as hereinabove defined, 0-75 % by weight of other organic solvents, 0.5-25 % by weight of water, 4-9832 - 6 0 - 35 % by weight of active ingredients and 10 - 70 % by weight of liquefied aerosol propellant gas, the content being stabilized by an amount of a tertiary amine of the formula - I in the range from 0.00001 to 0.1 part by weight per part by weight of liquid halogenated hydrocarbon.

The stabilization according to the invention is of special importance, if the aerosol formulations mentioned above are dispensed from aerosol containers made from metal. In this case, the corrosive attack on the metal (for example tin plate) may be substantially suppressed for a long time.

The following examples illustrate the invention: Examples Test mixtures were dispensed to welded tin plate aerosol bottles (18 oz) without interior lacquer protection. The bottles were closed by normal aerosol valves.provided with blank tin plate disks and after being charged with the propellant, they were stored at 40°C in a vertical position. When the intended storage time of, in general, 4, 8 and 12 weeks had passed, the bottles still charged were cooled to temperature lower than the boiling point of the propellants employed, they were perforated at the dome by means of a thorn and left to stand under a hood until they had reached again room temperature, with the portions of propellant evaporating gradually. The remaining contents were poured into beakers and the cleared bottles were opend by sawing. The remaining mixture (without propellant) as well as the opened tin plate bottles were examined optically for signs of corrosion. The statement without result of an examination means that the charge or the material of the bottle were uncharged, as compared with the original charge.

The following tables show the relation between stabilizator for water-containing methylene chloride, duration of storing and the corrosion of the aerosol - 7 bottles. Experiments 1 to 4 are comparative experiments. Experiments 5 to 7 are in accordance with the invention. - 8 Storage time 4 weeks Storage time - 9 [Storage time Table

Claims (5)

1. CLAIMS :1. A halogenated hydrocarbon selected from methylene chloride and trichlorofluoromethane, stabilized against decomposition by water, which comprises as stabilizer from 0.001 to 10 % by weight of a tertiary amine of the formula RR 1 R 2 N with R being alkyl with 1 to 10 carbon atoms and R 1 2 and R , independent from one another, being isopropyl, butyl-(2), tertiary butyl or cyclohexyl. 2. To 6 C-atoms. 8. Use of a tertiary amine according to claim 1 for stabilizing methylene chloride or trichlorofluoromethane against decomposition by water. 10 9. Use of a tertiary amine according to claim 1 for stabilizing a mixture of halogenated hydrocarbon and ether in which the halogenated hydrocarbon consists of methylene chloride or trichlorofluoromethane against decomposition by water. 15 10. An aerosol container containing a charge consisting of 10 - 89.5 % by weight of methylene chloride or trichloro fluoromethane 0-75 % by weight of other organic solvents, 20 0.5 - 25 % by weight of water, 0-35 % by weight of active ingredients and 10-70 % by weight of liquefied aerosol propellant, wherein the charge contains from 0.00001 to 0.1 part by weight of a tertiary amine according to claim 1 per 25 part by weight of halogenated hydrocarbon. 11. An aerosol container according to claim 10, wherein the container is made from metal. 12. A halogenated hydrocarbon according to claim 1, which is stabilized against decomposition by water, 30 substantially as hereinbefore described and exemplified. - 13 13. A halogenated hydrocarbon/ether mixture according to claim 5, substantially as hereinbefore described and exemplified. 14. An aerosol container according to claim 10,

2. A halogenated hydrocarbon according to claim 1, comprising the tertiary amine of the formula rrJn wherein R and R 1 are as defined in claim 1.

3. A halogenated hydrocarbon according to claim 1, wherein R is an alkyl with 1 to 4 carbon atoms.

4. A halogenated hydrocarbon according to any one of the claims 1 to 3, comprising as stabilizer from 0.01 to 1 % by weight of the tertiary amine. 5. A halogenated hydrocarbon/ether mixture in which the halogenated hydrocarbon is selected from methylene chloride and trichlorofluoroethane with a weight ratio of halogenated hydrocarbon/ether of from 1:2 to 100:1, comprising as stabilizer a mixture of from 0.001 to 10 % by weight of the tertiary amine according to claim 1. - 12 6. A mixture according to claim 5, wherein the ether consists only of carbon, hydrogen and oxygen and is free from other functional groups. 7. A mixture according to claim 6, wherein the 5 ether is an aliphatic linear ether with a total of

5. Substantially as hereinbefore described and exemplified.