EP0247467A2 - Use of salts from esters of long chain fatty alcohols with alpha-sulfofatty acids - Google Patents

Abstract

The invention relates to the use of salts (III) <IMAGE> of esters of long-chain fatty alcohols R¹-OH (I) with α-sulfofatty acid salts (II) <IMAGE>, wherein in the general formulas (I), (II) and (III) R¹ for an unbranched or branched alkyl radical or alkenyl radical with 8 to 36 C atoms or a mono- or polysethylated alkyl radical with 8 to 18 C atoms in the alkyl group and 1 to 10 ethoxy groups, R² for an unbranched or branched alkyl radical with 10 to 20 C -Atoms and M stands for half an equivalent of a divalent metal from the group magnesium, calcium, barium and zinc, as corrosion inhibitors in oils or oil-containing emulsions in amounts of 0.05 to 10 wt .-%, based on oil.

Description

The invention relates to the use of salts of esters of long-chain fatty alcohols with α-sulfofatty acids.

In industrial processes in which metal surfaces, in particular surfaces made of iron and its alloys, come into contact with oil or oil-containing aqueous emulsions under extreme conditions of pressure and temperature, the problem of corrosion of the metal surfaces occurs. Such processes are, for example, large-scale industrial cooling processes, metal surface cleaning and processing processes of the metal surfaces, such as drilling, cutting, rolling, etc. In such processes, oils or oil-containing emulsions are used without the influence of water on the metal surface can be completely excluded. However, the successive corrosion of the metal parts coming into contact with the oils or oil-containing liquids leads to a significant reduction in the service life of such systems or to problems in the subsequent treatment of the metal surface, for example during application a corrosion-protecting surface layer through phosphating or painting.

It has therefore been known for a long time to add corrosion inhibitors to the oil-based liquids which come into contact with the metal surfaces. As such, numerous compounds or mixtures of different compounds come into question in predominantly oil-containing liquids or pure oils. DE-AS 11 49 843 discloses half-amides of saturated or unsaturated dicarboxylic acids and their salts with aliphatic primary amines as additives for fuel oils and `lubricating oils`. Although these additives significantly improve corrosion protection, they have an extremely strong tendency to foam, which cannot be accepted in such additives. DE-AS 12 98 672 discloses alkali metal or amine salts of sulfonamidocarboxylic acids as corrosion inhibitors with good lubricating properties and little tendency to foam. Agents containing these compounds, however, have the disadvantage that they can only be prepared in processes which are complex in terms of manufacturing technology, and because of the relatively high content of sulfonamide groups they can sometimes have a toxic effect or at least have toxic effects expected, which necessitates corresponding toxicological tests.

For corrosion inhibition in oil or oil-containing systems, from "Ullmann's Encyclopedia of Industrial Chemistry", volume 18, 4th edition (1979), pages 1 and 2; and Winnacker, Küchler "Chemical Technology", Volume 4: "Organic Technology II", 3rd edition (1972), page 475 also known synthetic sulfonates from the group of petroleum sulfonates.

The disadvantage of these compounds, however, is that they are not biodegradable and therefore cannot be used in processes in which environmental contact inevitably takes place, since the escape of such agents into waste water or into the soil would cause ecological damage that is difficult to overlook.

The object of the present invention was to provide corrosion-inhibiting compounds for use in oil-containing systems which do not have the disadvantages of the prior art mentioned. The compounds should not only be accessible inexpensively in large quantities from regenerable sources, but should also have a corrosion-inhibiting effect which is at least equivalent to the known corrosion inhibitors. In addition, they should be ecologically and toxicologically harmless, and in particular should be more biodegradable than compounds previously used.

It has now been found that salts of esters of long-chain fatty alcohols with .alpha.-sulfofatty acids completely meet the requirements mentioned.

von Estern langkettiger Fettalkohole

mit α-Sulfofettsäuresalzen (II)

wobei in den allgemeinen Formeln (I), (II) und (III)

• R¹ für einen unverzweigten oder verzweigten Alkylrest oder Alkenylrest mit 8 bis 36 C-Atomen oder einen einfach oder mehrfach oxethylierten Alkylrest mit 8 bis 18 C-Atomen in der Alkylgruppe und 1 bis 10 Ethoxygruppen,
• R² für einen unverzweigten oder verzweigten Alkylrest mit 10 bis 20 C-Atomen und
• M für ein halbes Äquivalent eines zweiwertigen Metalls aus der Gruppe Magnesium, Calzium, Barium und Zink steht,

als Korrosionsinhibitoren in ölen oder ölhaltigen Emulsionen.The invention relates to the use of salts (III)

of esters of long-chain fatty alcohols

with α-sulfofatty acid salts (II)

where in the general formulas (I), (II) and (III)

• R ^{1 represents} an unbranched or branched alkyl radical or alkenyl radical with 8 to 36 C atoms or a single or multiple oxyethylated alkyl radical with 8 to 18 C atoms in the alkyl group and 1 to 10 ethoxy groups,
• R ² for an unbranched or branched alkyl radical having 10 to 20 carbon atoms and
• M represents half an equivalent of a divalent metal from the group consisting of magnesium, calcium, barium and zinc,

as corrosion inhibitors in oils or oil-containing emulsions.

The salts (III) of esters of long-chain fatty alcohols with α-sulfofatty acids used according to the invention are derived from long-chain fatty alcohols of the general formula (I) in which R ^{1 can represent} an unbranched or branched alkyl radical or alkenyl radical having 8 to 36 carbon atoms. Although in particular all unbranched or branched alkyl radicals or alkenyl radicals with 8, 9, 10, 11 etc. carbon atoms can be considered for R ¹ , those alcohols with alkyl radicals R ¹ which are available in large numbers from native sources are particularly preferred Amounts are accessible inexpensively. These are, for example, alcohols (I) in which _R ^{1 represents} an unbranched alkyl radical, preferably having 8 to 22 carbon atoms. The n-alkanols from the group octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, nonadecanol, eicosanol, uneicosanol and docosanol are suitable as such. Such alcohols, especially the representatives of this group an even number of carbon atoms in the alkyl radical are inexpensive from natural fats and oils via the corresponding fatty acids by reactions known per se for the hydrogenation of the carboxyl group and are available in large quantities on an industrial scale. The ester salts used according to the invention can not only be derived from the pure long-chain fatty alcohols of the general formula (I), but can also be ester salt mixtures which result from mixtures of such long-chain fatty alcohols (I) obtained in the industrial production process. Mixtures of this type in which ester salts of long-chain fatty alcohols of the general formula (I) occur, in which R ^{1 represents} a mixture of unbranched alkyl radicals in the range from 12 to 18, can be regarded as the alcohol mixtures sold under the trademark "Lorol" Ester salt mixtures from mixtures of long-chain fatty alcohols (I) can preferably be used, which consist of mixtures of cetyl alcohol, i.e. a saturated alcohol (I) with an unbranched C ₁₆ -alkyl radical, and oleyl alcohol, ie an alcohol unsaturated in the 9,10-position with an unbranched C ₁₈ Such mixtures are available under the trade name "Ocenol ^R " with different proportions of the unsaturated oleyl radical, for example "Ocenol ^R 50/55" or "Ocenol ^R 92/96".

The ester salts used according to the invention can also be derived from long-chain fatty alcohols (I) in which R ^{1 represents} a branched alkyl radical. Alcohols with such branched alkyl radicals can arise, for example, by subjecting alcohols of synthetic or native origin to the so-called "Guerbet reaction", from which essentially 2-alkylalkan-1-ols are obtained.

Examples of branched alcohols are 2-ethylhexanol, 2-hexyldecanol and 2-hexadecyleicosanol. Dimerized unsaturated fatty alcohols can also be used for the esterification. Such alcohol can be considered, for example, dimerized oleyl alcohol ("Sovermal ^R ").

The ester salts used according to the invention can also be derived from long-chain fatty alcohols of the general formula (I), the radical R ^{1 of which is} a mono- or polysethylated alkyl radical. Such radicals R1 have 8 to 18 carbon atoms in the alkyl radical and also contain 1 to 10 oxethyl groups, it being emphasized that the number of oxethyl groups per alcohol molecule (I) is to be regarded as the average degree of oxethylation of the respective alcohol and, as a result of the production process, in a more or less narrow range can fluctuate.

In this case too, preference is given to esters of long-chain fatty alcohols (I) whose alkyl radical has 12 to 18 C atoms and a number of ethoxy groups in the molecule which is in the range from 3 to 6.

in der R² für unverzweigte oder verzweigte Alkylreste mit 10 bis 20 C-Atomen und M für ein halbes Äquivalent eines Metalls aus der Gruppe Magnesium, Calcium, Barium und Zink stehen. R² kann somit ein geradkettiger Alkylrest aus der Gruppe Decyl, Undecyl, Dodecyl, Tridecyl, Tetradecyl, Pentadecyl, Hexadecyl, Heptadecyl, Octadecyl, Nonadecyl und Eicosyl sein oder auch für die entsprechenden verzweigten Isomere der genannten Alkylreste stehen. Die α-Sulfofettsäurekomponente der erfindungsgemäßen Ester stammt bevorzugt aus Fettsäuren natürlicher Herkunft, die in großen Mengen aus nativen Fetten und ölen durch Fettspaltung zugänglich gemacht werden können. Die natürlich resultierenden Fettsäuren werden durch gegebenenfalls notwendige hydrierende Härtung und anschließende, an sich bekannte, Sulfonierung in α-Position zur Carboxylgruppe in die α-Sulfofettsäuren der allgemeinen Formel (II) überführt, die eine der Komponenten für die erfindungsgemäß verwendeten Estersalze langkettiger Fettalkohole mit α-Sulfofettsäuren sind. Bevorzugt werden für derartige Ester die aus der Spaltung natürlicher Fette und öle resultierenden Fettsäuregemische verwendet. Als bevorzugte Gemische derartiger Fettsäuren werden solche angesehen, deren C-Zahl im Bereich von 12 bis 18 liegt, so daß R² für die α-Sulfofettsäurekomponente der erfindungsgemäß verwendeten Estersalze ein geradzahliger unverzweigter Alkylrest im Bereich von 10 bis 16 ist. Als Edukte, die auf dem aufgezeigten Wege zu den α-Sulfofettsäurekomponenten (II) der Estersalze (III) führen, sind somit Laurinsäure, Myristinsäure, Palmitinsäure, Stearinsäure, Lauroleinsäure, Myristoleinsäure, Palmitoleinsäure und ölsäure anzusehen. Hydrierung ungesättiger Reste R², anschließende Sulfonierung und Umsetzung mit Basen des Typs M₂(OH)₂ bzw. entsprechenden Salzen im alkalischen Medium führt zu den oG-Sulfofettsäuresalzen der allgemeinen Formel (II).The α-sulfofatty acid component of the ester salts used according to the invention has the general formula (II)

in which R ^{2 represents} unbranched or branched alkyl radicals having 10 to 20 carbon atoms and M represents half an equivalent of a metal from the group consisting of magnesium, calcium, barium and zinc. R ² can thus be a straight chain Alkyl radicals from the group decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl and eicosyl or also represent the corresponding branched isomers of the alkyl radicals mentioned. The α-sulfofatty acid component of the esters according to the invention preferably originates from fatty acids of natural origin, which can be made available in large quantities from native fats and oils by fat cleavage. The naturally resulting fatty acids are converted into the α-sulfofatty acids of the general formula (II), which are one of the components for the ester salts of long-chain fatty alcohols with α, which are used according to the invention, by optionally necessary hydrogenating curing and subsequent, known per se, sulfonation in the α-position to the carboxyl group -Sulfo fatty acids are. The fatty acid mixtures resulting from the cleavage of natural fats and oils are preferably used for such esters. Preferred mixtures of such fatty acids are those whose C number is in the range from 12 to 18, so that R ^{2 is} an even, unbranched alkyl radical in the range from 10 to 16 for the α-sulfofatty acid component of the ester salts used according to the invention. The educts which lead to the α-sulfofatty acid components (II) of the ester salts (III) in the manner shown are thus lauric acid, myristic acid, palmitic acid, stearic acid, lauroleic acid, myristoleic acid, palmitoleic acid and oleic acid. Hydrogenation of unsaturated radicals R ² , subsequent sulfonation and reaction with bases of the type M ₂ (OH) ₂ or corresponding salts in an alkaline medium leads to the oG-sulfofatty acid salts of the general formula (II).

As described, the ester salts used according to the invention can originate from salts (II), in the formula M of which stands for half an equivalent of a divalent metal from the group consisting of magnesium, calcium, barium and zinc. Half an equivalent of one of the divalent metals mentioned means that a metal atom is capable of binding two monovalent α-sulfofatty acid residues.

in der _R ¹, _R ² und M die oben genannten Bedeutungen haben können, entstehen beispielsweise dadurch, daß man die Fettalkohole (I) mit α-Sulfofettsäuren oder deren Salzen der allgemeinen Formel (II) in einem geeigneten organischen Lösungsmittel - gegebenenfalls in Gegenwart katalytischer Säuremengen - umsetzt, das Lösungsmittel nach an sich bekannten Methoden entfernt und die Produkte, sofern erwünscht, nach ebenfalls bekannten Methoden reinigt und isoliert. Es ist jedoch auch möglich, die Produktlösungen unmittelbar, d.h. ohne die Salze (III) in Reinform zu isolieren, für die Korrosionsinhibierung zu verwenden.The process for producing the ester salts (III) of long-chain fatty alcohols with α-sulfofatty acid salts used according to the invention is known as such. The ester salts of the general formula (III) resulting from this process

in which _R ¹ , _R ² and M can have the meanings given above arise, for example, by reacting the fatty alcohols (I) with α-sulfofatty acids or their salts of the general formula (II) in a suitable organic solvent - optionally in the presence of catalytic ones Amounts of acid - reacted, the solvent removed by methods known per se and, if desired, the products purified and isolated by methods which are also known. However, it is also possible to use the product solutions directly, ie without isolating the salts (III) in pure form, for the corrosion inhibition.

Inorganic mineral acids, in particular sulfuric acid, in particular, have proven useful as catalysts for the process mentioned is preferred. However, acidic ion exchangers or other acidic catalysts known per se can also be used. The esterification reaction is usually carried out in an organic solvent. Examples of such solvents are toluene or xylene. The reaction temperatures of the esterification reaction vary depending on the alcohol (I) and oC-sulfofatty acids or their salts (II) used and are normally 0 to 140 ° C.

As with numerous other esterification reactions, it can be advantageous to remove the amount of water formed during the esterification by methods known per se. In the simplest case, this is done with the aid of an organic solvent which is suitable as a "tug" and which forms an azeotrope with water and thereby removes it from the reaction mixture. This gradually shifts the balance of the esterification reaction towards the products.

After completion of the reaction, which can be recognized, for example, by the separation of the previously calculated amount of water, the organic solvent is removed by methods known per se. This can be done for example by distillation at normal pressure or reduced pressure. If necessary, the product mixture obtained is then converted into the salts (III) used according to the invention by methods which are also known (neutralization).

The esters or their salts (III) or mixtures of different compounds are then obtained by the process route outlined, namely when as α-sulfo fatty acid starting material mixtures of compounds of general formula (II) or as fatty alcohol starting material (I) fatty alcohol mixtures were used.

A preferred way of producing the ester salts of the general formula (III) used according to the invention is, however, to start from fatty acid alkyl esters, preferably fatty acid methyl esters, from partially synthetic or synthetic production, adding these esters according to known methods with SO ₃ in the α-position sulfonate, adapt the sulfonation products by methods which are also known, for example by bleaching with hydrogen peroxide, to the customary quality standard and the fatty acid alkyl esters sulfonated in this way in the α-position with the addition of an excess of an alcohol _R 1 ^- _OH (I), in which R the has meanings given above, to transesterify. A major advantage of this procedure is that the successive reactions can be carried out without isolating the intermediates and comparatively high product yields can be obtained, which can then be directly converted into the desired ester salts of the general formula (III ) leads.

Both the salts of the esters of the general formula (III) and mixtures of various such compounds are particularly suitable as corrosion inhibitors in oils and oil-containing emulsions. They are particularly preferably used as corrosion protection agents in lubricating oils, greases, power transmission oils and metalworking emulsions based on mineral oils puts. The salts (III) used according to the invention are excellently soluble in mineral oils or oil-containing emulsions and have the great advantage over the anticorrosive agents known from the prior art, such as petroleum sulfonates or comparable compounds, in that they are large in processes which have been known for a long time and have therefore been well studied Quantities can be made inexpensively accessible. In addition, they are completely harmless from a toxicological point of view and can generally be broken down better than the petroleum sulfonates conventionally used as corrosion protection agents.

The amounts of the salts (III) used according to the invention are, depending on the field of use, in the range from 0.05 to 10% by weight, based on the respective oil base, preferably in the range between 0.5 and 5% by weight. Even at low concentrations, the corrosion-inhibiting effect is comparable to that of conventional agents known from the prior art, and in the case of application concentrations of the same order of magnitude, in some cases even better than the corrosion-inhibiting effect of synthetic sulfonates, such as petroleum sulfonates.

The invention is illustrated by the following examples.

example 1 Preparation of the esters according to the invention.

• ^A C_12-18-Fettsäuremethylester-Fraktion aus gehärtetem Palmkernfettsäuremethylester, C-Kettenverteilung: 48 % C₁₂, ^{18 %} C₁₄, ^{10 %} C₁₆, 23 % ^C1^8. Verseifungszahl: 234, Jodzahl: 0,1.
• B Oleylalkohol durch Hydrierung von angereichertem technischen ölsäuremethylester (im Handel z.B. unter der Bezeichnung Ocenol^R 92/96).

Calcium salt of α-sulfonated C _12-18 fatty acid oleyl ester Fat substances used :,

• ^A C _12-18 fatty acid methyl ester fraction from hardened palm kernel fatty acid methyl ester, C chain distribution: 48% C ₁₂ , ^18% C ₁₄ , ^10% C ₁₆ , 23% ^C 1 ^8. Saponification number: 234, iodine number: 0.1.
• B oleyl alcohol by hydrogenation of enriched technical oleic acid methyl ester (commercially eg under the name Ocenol ^R 92/96).

240 g (1 mol) des Esters (A) wurden mit 72 g (0,9 mol) SO₃ sulfoniert, indem man aus 100 g 65 %igen Oleums das enthaltene SO₃ freisetzte und gasförmig im Gemisch mit Stickstoff im Verhältnis 5 Vol.-% SO₃/ 95 Vol.-% N₂ bei einer Temperatur von 80°C über eine Zeitdauer von ca. 1 h durch den Ester (A) leitete. Man ließ ca. 1/2 h bei 80°C nachreagieren. Das schwarze Sulfonierungsprodukt wurde durch Zugabe von 2 % von 35 %igem Wasserstoffperoxid aufgehellt.Chain distribution:

240 g (1 mol) of the ester (A) were sulfonated with 72 g (0.9 mol) of SO ₃ by liberating the SO ₃ contained from 100 g of 65% oleum and gaseous in a mixture with nitrogen in a ratio of 5 vol. -% SO initiated _3/95 vol .-% N ₂ at a temperature of 80 ° C over a period of about 1 hour by the ester (a). The mixture was left to react at 80 ° C. for about 1/2 h. The black sulfonation product was lightened by adding 2% of 35% hydrogen peroxide.

410 g (1.5 mol) of oleyl alcohol (B) were added to the bleached product. It was then at 90 ° C for 4 h heated with stirring and in a water jet vacuum. The methanol released (32 g) was condensed in a cold trap. The acid number of the reaction product was determined to be 56.

For neutralization, 25.5 g of calcium hydroxide were placed in a mixture of 300 g of water and 100 g of isopropanol. The sulfonation product was added dropwise. The neutralized product (pH 5 to 8) separated out in the heat as a lighter phase in which the calcium salt was present together with some isopropanol, unsulfonated ester fractions and unused oleyl alcohol. This phase was separated and freed of isopropanol and water residues in vacuo at 90 ° C. In the end product, which slowly solidified at room temperature, 1.9% Ca was analyzed.

Examples 2 to 4

• Magnesiumsalz (Beispiel 2): 1,5 % Mg
• Bariumsalz (Beispiel 2): 7,0 % Ba
• Zinksalz (Beispiel 4): 3,7 % Zn.

In the same procedure as in Example 1, neutralization was carried out with magnesium hydroxide, barium hydroxide and zinc oxide instead of calcium hydroxide. Salts of α-sulfonated C _12-18 fatty acid _ethyl ester were obtained with the following analytical values:

• Magnesium salt (Example 2): 1.5% Mg
• Barium salt (Example 2): 7.0% Ba
• Zinc salt (Example 4): 3.7% Zn.

Examples 5 to 7

The procedure for these examples corresponded to that for Examples 1 to 4, but with the difference that now the sulfonation was carried out with 1.2 mol SO ₃ instead of 0.9 mol S0 ₃ .

For example, base used for transesterification of alcohol used for neutralization analysis

Example 8

_R eindarstellung of the barium salt of α-sulfo-C _12-18 - fettsäureoleylester from the sodium salt by precipitation reaction.

a) Preparation of the sodium salt

The α-sulfoester obtained by sulfonation and transesterification with oleyl alcohol according to Example 1 was neutralized with sodium hydroxide solution instead of calcium hydroxide. By extracting the aqueous isopropanol solution with petroleum ether, all unsulfonated portions were removed. Then the salt solution was evaporated in vacuo and dried. The dry evaporation residue was mixed with ethyl acetate (500 g of ethyl acetate to 20 g of residue) and treated in the heat for 10 minutes at the reflux temperature. The solution became fil trated and evaporated. 4.1% Na were analyzed in the evaporation residue (sodium salt) (calculated: 3.95% Na).

b) Preparation of the barium salt

20 g (0.034 mol) of the sodium salt prepared according to (a) were dissolved in water / isopropanol and with an aqueous solution of 4.2 g (0.017 mol) of BaCl ₂ . 2 H ₂ 0 added. A crystalline precipitate formed which was filtered off. After drying at 50 ° C. under high vacuum, 10.4% Ba (also 0.2% Na) were analyzed in the barium salt obtained (17.2 g) of α-sulfo-C _12-18 fatty acid oleyl ester (also 0.2% Na) (calculated: 10 , 9% Ba). This compound was found to be soluble in mineral oil.

Example 9

In a manner analogous to Examples 1 to 8, further ester salts of the general formula (III) were prepared, which are listed in Table 1 below.

Example 10

According to DIN 51585, steel rods (material composition: C _K 15, surface degreased and sanded) in stirred mixtures of mineral oil and artificial sea water in a ratio of 10: 1 (method B according to DIN 51585) stored at 60 ° C for 24 h.

• 0: keine Korrosion,
• 1: Spuren von Korrosion,
• 2: leichte Korrosion (korrodierte Fläche ≃5 %),
• 3: mäßige Korrosion (korrodierte Fläche im Bereich zwischen 5 und 20 %) und
• 4: starke Korrosion (korrodierte Fläche über 20 %).

After the prescribed test period, the test specimens were assessed for signs of corrosion. In this and the following examples, the evaluation was carried out on the following scale:

• 0: no corrosion,
• 1: traces of corrosion,
• 2: slight corrosion (corroded area ≃5%),
• 3: moderate corrosion (corroded area in the range between 5 and 20%) and
• 4: severe corrosion (corroded area over 20%).

The results are shown in Table 2 below.

Comparative example la

In an analogous manner to that described in Example 10, identical steel rods were stored for 24 hours in oil-seawater mixtures at 60 ° C. which did not contain an inhibitor. The results (cf. la) are also shown in Table 2 below.

Comparative Example Ib

In an analogous manner to that described in Example 10, identical steel rods were stored for 24 hours in oil-seawater mixtures at 60 ° C., which contained a synthetic calcium petrol sulfonate (see FIG. 1b) as a commercially available inhibitor. The results are also shown in Table 2 below.

Example 11 Moisture chamber test

According to DIN 51359, sandblasted steel sheets 088 St 1405 (degreased) (dimensions: 25 mm x 50 mm) were immersed in a naphthenic mineral oil that contained ester salts (III) as corrosion inhibitors. The test loaded with the corrosion-inhibiting mineral oil After a certain draining time or drying time, the bodies were hung in a moisture chamber and stored for 30 days in a water vapor-saturated atmosphere in accordance with DIN 51359, a continuous air supply of 875 l / h and a temperature of 50 ° C. and a relative humidity of 100% being set. After the prescribed test duration, the test specimens were assessed for signs of corrosion, the evaluation scale given in Example 10 being used as the basis for the degree of corrosion.

The results are shown in Table 3 below.

Comparative Example 2a

In the same way as described in Example 11. Steel sheets of the specified quality immersed in a mineral oil that did not contain an inhibitor. The result is also shown in Table 3 below (cf. 2a).

Comparative Example 2b

In the same way as described in Example 11, steel sheets of the quality mentioned were immersed in a mineral oil which contained a synthetic calcium petrol sulfonate (see FIG. 2b) as a commercially available inhibitor. The result is also shown in Table 3 below.

Example 12 Gray cast iron filter paper test.

In accordance with DIN 51360 / Part 2, gray cast iron chips were wetted on a round filter with a mineral oil-seawater emulsion in accordance with DIN 51360 / Part 2, this mineral oil emulsion also containing ester salts (III) as corrosion inhibitors in a concentration of 2% by weight contained. After an exposure time of 2 h at room temperature, the corrosion marks on the filter paper were assessed visually according to the method specified in the standard.

The emulsions were prepared from a concentrate of the following composition by customary methods and using water which had a total hardness of 3.58 mmol CaCl ₂ . 6H ₂ 0 and MgS0 ₄ . 7H ₂ 0.

• 60 % naphthenisches Mineralöl,
• 15 % Emulgator (Addukt von 6,5 EO an Nonylphenol) und
• 25 % des erfindungsgemäß verwendeten Estersulfonatsalzes (III).

The concentrate, which was added in amounts of 4 to 8% by weight in water, had the following composition:

• 60% naphthenic mineral oil,
• 15% emulsifier (adduct of 6.5 EO with nonylphenol) and
• 25% of the ester sulfonate salt (III) used according to the invention.

The results are shown in Table 4 below.

Comparative Example 3

According to the method given in Example 12, the gray cast iron chips were wetted with a mineral oil emulsion which did not contain an inhibitor. The recipe contained naphthenic mineral oil and emulsifier in a weight ratio of 4: 1.

The results are also shown in Table 4 below (cf. 3).

Example 13 Bulk removal test.

Steel sheets of quality ST 1405, which had been degreased and sanded (size: 25 mm x 50 mm), were exposed in stirred mineral oil emulsions at 50 ° C for two weeks to the action of an emulsion that was contaminated with chloride and hardness while being gassed with atmospheric oxygen. Two panels were used for each inhibitor test. After the test period, the loss of mass was determined gravimetrically for both sheets and the values obtained were averaged.

From the comparison of the averaged values to the averaged removals for a blank sample from inhibitor free corrosion protection was then calculated in% according to the following equation:

• ΔG₀ die Gewichtsdifferenz des Prüfbleches vor und nach der Lagerung in inhibitorfreier Emulsion und
• ΔG_I die Gewichtsdifferenz des Prüfbleches vor und nach der Lagerung in inhibitorhaltiger Emulsion.

In this equation are:

• ΔG _{0 is} the difference in weight of the test sheet before and after storage in an inhibitor-free emulsion and
• ΔG _{I is} the difference in weight of the test sheet before and after storage in an inhibitor-containing emulsion.

The results are shown in Table 5 below.

Comparative Example 4

In the same way as described in Example 13, steel sheets were exposed to a mineral oil emulsion which contained no inhibitor. The weight ratio of mineral oil: emulsifier in this emulsion was 4: 1. An adduct of 6.5 EO with nonylphenol was used as the emulsifier, and a naphthenic mineral oil was used as the oil.

The results are also shown in Table 5 below (see FIG. 4).

Example 14

• 60 % naphthenisches Mineralöl,
• 15 % Emulgator (Addukt von 6,5 EO an Nonylphenol) und
• 25 % Estersulfonatsalz (III).

Steel sheets of quality ST 1405, which were degreased and sanded (dimensions: 25 mm x 50 mm), were immersed in mineral oil emulsions containing 20% by weight of the concentrates specified below:

• 60% naphthenic mineral oil,
• 15% emulsifier (adduct of 6.5 EO with nonylphenol) and
• 25% ester sulfonate salt (III).

The specimens were then stored after a certain draining time and drying time in a humidity chamber with a water vapor-saturated atmosphere (100 _% relative air humidity) for 30 days at room temperature. After the end of the test period, the steel sheets were assessed for signs of corrosion, based on the evaluation scale given in Example 10.

The emulsions were prepared from the corresponding concentrates (see above) using customary methods and using water with a total hardness of 3.58 mmol CaCl ₂ .6H ₂ O and MgSO ₄ . 7H20 manufactured.

The results are shown in Table 6 below.

Comparative Example 5

Steel sheets of identical quality were treated in the manner given in Example 14, the emulsions not containing any inhibitor. The ratio of mineral oil: emulsifier in the comparison emulsions was 4: 1.

The results are also shown in Table 6 below (cf. 5).

Claims (10)

1. Use of salts (III)

of esters of long-chain fatty alcohols

with α-sulfofatty acid salts (II)

where in the general formulas (I), (II) and (III) R represents an unbranched or branched alkyl radical or alkenyl radical with 8 to 36 C atoms or a mono- or polysethylated alkyl radical with 8 to 18 C atoms in the alkyl group and 1 to 10 ethoxy groups, R ² for an unbranched or branched alkyl radical having 10 to 20 carbon atoms and M represents half an equivalent of a divalent metal from the group consisting of magnesium, calcium, barium and zinc,
as corrosion inhibitors in oils or oil-containing emulsions in amounts of 0.05 to 10% by weight, based on oil. 2. Use according to claim 1, characterized in that in the general formulas R represents an unbranched alkyl radical having 8 to 22 carbon atoms. 3. Use according to claims 1 to 2, characterized in that in the general formulas R ^{1 stands} for mixtures of several alkyl radicals. 4. Use according to claim 3, characterized in that in the general formulas R ^{1 stands} for mixtures of alkyl radicals having 12 to 18 carbon atoms. 5. Use according to claim 4, characterized in that in the general formulas R ^{1 stands} for mixtures of cetyl radicals and oleyl radicals. 6. Use according to claims 1 and 2, characterized in that R ¹ in the general formulas represents branched alkyl radicals of Guerbet alcohols. 7. Use according to claims 1 and 2, characterized in that in the general formulas R ^{1 stands} for a polyethylated alkyl radical having 12 to 18 carbon atoms in the alkyl radical and 3 to 6 ethoxy groups. 8. Use according to claims 1 to 7, characterized in that R ² in the general formulas represents an even numbered unbranched alkyl radical having 10 to 16 carbon atoms. 9. Use according to claims 1 to 8, characterized in that the oils or oil-containing emulsions are lubricating oils, greases, power transmission oils or metalworking emulsions based on mineral oils. 10. Use according to claims 1 to 9, characterized in that the amount of ester salts (III) is 0.5 to 5 wt .-%, based on oil.