NO812415L - STABILIZED 1,1,1-TRICHLORETHAN MIXTURES. - Google Patents

Description

The present invention relates to stabilized 1,1,1-trichloroethane-containing mixtures which can be used for degreasing metals, while maintaining a constant pH.

It is known that 1,1,1-trichloroethane, which is particularly used for degreasing metals and dry-cleaning textiles, and in aerosols, causes a very special stability and corrosion problem. Application of the stabilizers which are normally used for other chlorinated hydrocarbons for the stabilization of 1,1,1-trichloroethane generally does not give satisfactory results. This phenomenon has been attributed to the fact that there is a high reactivity. between metals and 1,1,1-trichloroethane, which reactivity within a very short time gives rise to decomposition of the 1,1,1-trichloroethane and attack on the metal.

For stabilization of 1,1,1-trichloroethane, it has already been proposed to use epoxide compounds together with nitroalkanes (U.S. Patent No. 3,049,571, No. 3,532,761, No.

4,026,956 and Belgian Patent No. 763,703. According to these patents

different epoxy compounds can be used for this purpose. However, since epoxybutane is the only one available under commercially advantageous conditions, this compound is still the one used in practice.

Although the pH stability of 1,1,1-trichloroethane-containing mixtures stabilized with epoxybutane can be considered satisfactory in most cases, stability problems still remain when these mixtures are used for degreasing metal parts that are wetted with oils for cutting tools. In this case, it is observed, depending on the nature of the oil used, that the 1,1,1-trichloroethane-containing mixture becomes acidic or basic, and this makes it necessary to adapt the composition of the stabilizer in each individual case.

The purpose of the present invention is to provide 1,1,1-trichloroethane-containing mixtures whose pH does not vary, even when used, for degreasing metal parts that are moistened with different types of oils for cutting tools.

The invention thus relates to 1,1,1-trichloroethane-containing mixtures containing at least one nitroalkane and at least one epoxide compound, namely 2-methyl-2,3-epoxybutane.

The nitroalkane in the mixtures according to the invention contains . usually 1-4 carbon atoms. It is preferably nitromethane,

nitroethane, 1-nitropropane or 2-nitropropane or a mixture of these compounds. Nitromethane and nitroethane are very particularly preferred.

The amount of nitroalkane usually varies between 0.001 mol and

1 mole per liter of 1,1,1-trichloroethane. Preferably, this amount is between 0.01 and 0.5 mol per litres. Amounts between 0.05 and 0.3 mol per liters of 1,1,1-trichloroethane is very particularly preferred.

The amounts of 2-methyl-2,3-epoxybutane, also referred to as isoamylene oxide, are the same as those described above for the nitroalkanes.

In addition to the above-mentioned compounds, the mixtures may contain one or more other stabilizers which are common for. 1,1,1-trichloroethane, such as alcohols, esters, nitriles, internal ethers and ketones, and also epoxide compounds such as isobutene oxide. However, the mixtures containing 2-methyl-2,3-epoxybutane as the sole epoxide compound are preferred.

The alcohols can be saturated or unsaturated. The preferred alcohols contain 1-7 carbon atoms and may be substituted or unsubstituted. Usually they are unsubstituted alcohols.

Examples of saturated alcohols are methanol, ethanol, propanol, isopropanol, butan-1-ol, butan-2-ol, tertiary butyl alcohol, pentanols such as tertiary amyl alcohol, ethylene glycol monomethyl-, monoethyl, monopropyl or monobutyl ether, glycerol , ethylene glycol, propylene glycol, 2-hydroxy-2-methylbutan-3-one, 3,3-dimethoxy-2 - methylbutan-2-dl and 3-amino-2-methylbutan-2-ol. Very good results have been achieved with propanols, tertiary and secondary butanols and tertiary pentanol. The preferred saturated alcohol is tertiary butanol.

The unsaturated alcohols that are usually used are unsubstituted alcohols containing 3-6 carbon atoms. Among these, allyl alcohol, 2-methylbut-3-en-2-ol and 2-methylbut-3-yn-2-ol are preferred. The preferred unsaturated alcohol is 2-methylbut-3-yn-2-ol.

The most commonly used esters are monoesters and diesters containing 2-8 carbon atoms, which are saturated or unsaturated and which may be substituted with halogens or hydroxyl groups, such as ethyl-, propyl-, isopropyl-, butyl-, sec-butyl-, tert .-butyl-, amyl-, hexy 1- and . cyclohexyl formates, methyl, ethyl,• propyl, isopropyl, butyl, amyl, ethynyl and propynyl acetates, methyl, ethyl, propyl, isopropyl, butyl, amyl and ethynyl -propionates,. methyl, ethyl, propyl, isopropyl and prop-2-ynyl butyrates, methyl, ethyl, propyl, isopropyl, butyl, sec-butyl and tert-butyl acrylates and methacrylates, methyl and ethyl crotonates and isocrotonates. ethyl and methyl sorbinates, ethyl diformate and ethyl diacetate. Unsubstituted monoesters containing 4-6 carbon atoms are suitable. Very good results have been obtained with ethyl acetate, isobutyl acetate, n-propyl acetate, methyl methacrylate and n-butyl acetate. Methyl methacrylate, ethyl acetate and n-propyl acetate have been found to be particularly suitable.

The most commonly used nitriles are optionally substituted,

saturated or unsaturated, aliphatic or aromatic compounds containing 2-7 carbon atoms, such as acetonitrile, propionitrile, acrylonitrile, butyr-nitrile, methacrylonitrile, malon-nitrile, benznitrile, dimethylamine-acetonitrile, methylamine-propionitrile, dimethylamine-propionitrile, diethylamine-acetonitrile , methylethylamine-acetonitrile, thiodipropionitrile, tetracyan - ethylene, tetra-cyanoquinodimethane, tetracyandithiin, 1,2-dicyan-1,2-bis-(tri-fluoromethyl)-ethylene, cyano-benzaldehyde, nitro-benznitrile and cyan -pyridine. Among these, acetonitrile, propionitrile and acrylonitrile are the most suitable.

The particularly suitable internal ethers are monocyclic or polycyclic ethers which can alternately contain other heteroatoms and which contain one or more substituted or unsubstituted, saturated or unsaturated rings with 5 or 6 carbon atoms, such as 1,3-dioxane, 1,4-dioxane, 1,3,5-trioxane, 1,3-dioxolane, dioxane, dioxadiene, thioxane, oxazole, tetrahydrofuran, diphenyl ether and the like.

Ketones that can be used are substituted or unsubstituted ketones containing 3-7 carbon atoms, such as, for example, acetone, methyl 1-ethyl 1-ketone, diethyl ketone, methyl 1-propyl 1-ketone, methyl 1-isopropyl ketone, 1- (furan-2-yl)-propanone, 3-hydroxy-hexane-2,5-dione, 2-methyl-2-hydroxypentan-4-one and the like.

Other compounds, and in particular alkoxyalkanes such as alkoxyethanes, nitrates such as alkyl nitrates containing 1-5 carbon atoms, amines such as aliphatic amines containing 2-6 carbon atoms, pyrroles such as n-methyl-pyrrole, and other aromatic compounds such as toluene, or aliphatic compounds such as di-isobutylene,

can also be incorporated into the stabilizer ultimately used for 1,1,1-trichloroethane.

The various other stabilizers used are. usually present in amounts between 0.01 and 2 moles per liter of 1,1,1-trichloroethane and preferably in amounts between 0.1 and 0.8 moles per liter. litres.

Mixtures which are very effectively stabilized according to the invention contain, in addition to 2-methyl-2,3-epoxybutane and nitro-methane or nitro-ethane, a saturated alcohol, more spe-. particularly tertiary butyl alcohol, and an unsaturated alcohol, more particularly - 2-methylbut-3-yn-2-ol.

The 1,1,1-trichloroethane mixtures stabilized according to the invention can be used for any purpose where good stabilization of the 1,1,1-trichloroethane used is required. They are preferably used for degreasing metals and more particularly for degreasing metals that have been moistened with oils for cutting tools. The term "cutting tool oils" includes any type of oil or grease used in operations such as machining, boring, polishing and wire drawing of metals.

The examples that follow do not indicate. in any way any limitation.

Example 1

This example is a comparison example.

300 cm 3 trichloroethane stabilized with 0.541 mol/l tertiary buty1-alcohol, 0.164 mol/l nitromethane, 0.208 mol/l 2-methylbut-3-yn-2-ol and 0.079 mol/l epoxybutane, and 75 cm 3 oil for cutting tools (respectively kaleol oil in Experiment 1, calcium stearate in Experiment 2 and polybutylcuprisil in Experiment 3) are placed in a 500 cm^ round-bottomed flask fitted with a thermometer and equipped with a SOXI-ILET type extraction apparatus with a capacity of 100 cm 3, which is again connected to a capacitor, and the whole thing is protected from the light.

The mixture is kept at the boiling point. for 72 hours, and the heating is adjusted so that the extraction apparatus is filled and emptied completely at 30-minute intervals. Consequently, the concentration of oil for cutting tools in the mixture varies continuously between 20 and 27.6% by volume, thus imitating the conditions that occur in industrial machines for degreasing in the vapor phase.

After the boiling period of 72 hours, the contents of the extraction apparatus are emptied into the flask, the condenser is mounted in an inclined position and the solvent is recovered by distillation. The degradation of this solvent is determined by measuring the acidity, and the results are given in Table I below.

Example 2

The work operations in Example 1 are repeated, but the process is carried out using 1,1>1-trichloroethane stabilized with 0.541 mol/l tertiary butyl alcohol, 0.164 mol/l nitromethane, 0.208 mol/l 2-methyl-but-3-yn-2 -ol and 0.079 mol/1 2-methyl-2,3-epoxybutane.

The degradation of this solvent is determined by measuring the acidity, and the values are given in Table II below.

A comparison of the results in Examples 1 and 2 shows that a 1,1,1-trichloroethane mixture stabilized with nitromethane and 1,2-epoxybutane can be attacked by different types of oils and is only suitable for certain non-aggressive oils, while the mixture according to the invention, in which 1,2-epoxybutane is replaced by a corresponding amount of 2-methyl-2,3-epoxybutane, is suitable in all cases.

Claims (9)

1. Stabilized 1,1,1-trichloroethane mixtures containing at least one nitroalkane and at least one epoxide compound, characterized in that the epoxide compound is 2-methyl-2,3-epoxybutane. 2. Mixture according to claim 1, characterized in that the nitroalkane is nitromethane or nitroethane. 3. Mixture according to claim 1 or 2, characterized in that the nitroalkane and the 2-methyl-2,3-epoxybutane are present in amounts between 0.001 and 1 mol per liter 1,1,1-trichloroethane.. 4. Mixture according to one of the preceding claims, characterized in that it also contains one or more others ■stabilizers selected from alcohols, esters, nitriles, internal ethers and ketones. 5. Mixture according to claim 4, characterized in that the alcohols are unsubstituted, saturated or unsaturated alcohols. 6. Mixture according to claim 5, characterized in that the alcohols are tertiary butyl alcohol or 2-methyl-but-3-yn-2-ol. 7. Mixture, according to claim 6, characterized in that it contains tertiary butyl alcohol and 2-methyl-but-3-yn-2-ol. 8. Mixture according to one of claims 4-7, characterized in that the other stabilizers are present in an amount of 0.01-2 mol per liter of 1,1,1-trichloroethane. 9. Mixture according to one of the preceding claims, characterized in that it contains 2-methyl-2,3-epoxybutane as the only epoxy compound.