EP0222311B1 - Use of alkoxy-hydroxy-substituted fatty acids as corrosion inhibitors in oils and emulsions containing oil - Google Patents

Abstract

Acid cleaning/pickling compositions for metal surfaces containing (A) at least one protein-derived polymer, sugar-derived polymer, sorbitol, tannin, or vinyl-based polymer, (B) at least one iodine or iodine-affording compound; acids solutions prepared therefrom; and methods for their use.

Description

In technical processes for mechanical processing and cleaning of metal surfaces as well as in technical cooling processes, oils and oil-containing emulsions come into contact with metal surfaces at high temperatures, the liquid media containing more or less large amounts of water. These result in part from the particular process taking place, as is the case, for example, with steam turbines, but can also be a desired component of the respective liquid media. In all such cases, protecting the metal surfaces coming into contact with the liquid media against corrosion poses a significant problem. Iron or iron-containing alloys in particular are corroded by water or moisture in the process liquids. The result in the ongoing process is a reduction in the service life of the respective system or, in the case of further processing of the metal surfaces, the need for complex cleaning of the metal surfaces in preparation for subsequent process steps, for example by phosphating, electroplating, painting, etc.

To inhibit corrosion, a corrosion inhibitor is added to the process, cleaning or cooling liquids in such cases, which should inhibit, if not completely suppress, the corrosion.

DE-B-11 49 843 and EP-B-0 002 780 describe amine salts of amic acids which are obtained by reacting succinic or maleic anhydride with primary alkylamines, and alkanolamine salts of maleic acids as corrosion inhibitors for fuel and lubricating oils or also called water-containing systems. However, such compounds have the disadvantage that they tend to foam very strongly or - with a low tendency to foam - lose a large part of their corrosion-inhibiting effect.

DE-B-12 98 672 also discloses alkali or amine salts of sulfonaminocarboxylic acids, which likewise have a good corrosion protection effect in known metalworking fluids or oil-containing oil emulsions. However, a disadvantage of these compounds is that they are to be regarded as relatively toxic and their use is therefore subject to severe restrictions.

DE-A-29 43 963 also discloses alkanolamine salts of certain alkenylsuccinic acids which, in aqueous systems without foam formation, show good corrosion protection on metal surfaces made of iron or iron-containing alloys. EP-A-0 127 132 also discloses alkenylsuccinic acid halamides as corrosion inhibitors, which are also used in aqueous process fluids for drilling, cutting or rolling metals. In aqueous media in particular, however, hydrolysis of the succinic acid derivatives mentioned is observed, which drastically reduces the corrosion-inhibiting effect of such compounds. In addition, the starting materials required for the preparation of such compounds are only available after in some cases complex syntheses, so that it seemed necessary to find new anticorrosive active ingredients which are not only universally applicable, but also the disadvantages described here, such as tendency to foam formation, hydrolysis instability, Do not display toxicity, incompatibility with hard process water etc.

in der R¹ für unverzweigte Alkylreste oder Alkenylreste mit 6 bis 8 C-Atomen, R² für unverzweigte oder verzweigte Alkylreste mit 1 bis 18 C-Atomen oder für unverzweigte oder verzweigte Alkenylreste mit 2 bis 18 C-Atomen, M für Wasserstoff oder organische Ammoniumreste mit einem oder mehreren Alkylresten oder Hydroxyalkylresten am Stickstoffatom und m für ganze Zahlen im Bereich von 3 bis 13 stehen, in Mengen von 0,01 bis 10 Gew.-%, bezogen auf Ölbasis, als Korrosionsinhibitoren in Ölen und ölhatigen Emulsionen.It has now surprisingly been found that ring opening products of epoxy fatty acids with unbranched or branched alcohols and their salts are particularly suitable as corrosion inhibitors in mineral oils and emulsions containing mineral oils. The invention relates to the use of alkoxyhydroxy fatty acids and their salts of the general formula (I)

in R ¹ for unbranched alkyl radicals or alkenyl radicals with 6 to 8 C atoms, R ² for unbranched or branched alkyl radicals with 1 to 18 C atoms or for unbranched or branched alkenyl radicals with 2 to 18 C atoms, M for hydrogen or organic Ammonium radicals with one or more alkyl radicals or hydroxyalkyl radicals on the nitrogen atom and m represent integers in the range from 3 to 13, in quantities of 0.01 to 10% by weight, based on oil, as corrosion inhibitors in oils and oil-containing emulsions.

in der R¹ und m die oben angegebenen Bedeutungen haben und M für Wasserstoff oder eine Alkylgruppe, bevorzugt von in natürlichen Fetten oder Ölen verestert vorkommenden Alkoholen stehen kann, nach an sich bekannten Verfahren expodiert werden. Eine derartige Epoxidationsreaktion kann beispielsweise durch Umsetzung der Fettsäuren oder deren Estern der allgemeinen Formel (II) mit organischen Peroxosäuren unter geeigneten Bedingungen erfolgen. Die auf diesem Wege erhaltenen Epoxide, die den Oxiranring an der Position im Molekül tragen, an der in den Edukten die olefinische Doppelbindung zu finden war, werden dann nach ebenfalls an sich bekannten Verfahren durch sauerkatalysierte Ringöffnung mit Alkoholen der allgemeinen Formel

in der R² die oben angegebenen Bedeutungen haben kann, in die entsprechenden Alkoxyhydroxyfettsäurederivate überführt, in denen die Alkoxygruppe R²0 und die Hydroxygruppe je an den beiden im Edukt durch die olefinische Doppelbindung verbundenen Kohlenstoffatomen angebunden sind. Je nach Einsatzmenge an Alkohol kann dabei auch die endständige Estergruppierung der Epoxide umgeestert werden.The compounds of the general formula (1) which are used according to the invention for corrosion inhibition are known as such. The process for their preparation is described in the relevant literature, for example in DE-A-33 18 596 (EP-A-0 127 810). Alkoxyhydroxy fatty acids and their salts of the general formula (I) are then formed, for example, by the fact that fatty acids or their esters of the general formula (11)

in which R ¹ and m have the meanings given above and M can stand for hydrogen or an alkyl group, preferably alcohols occurring in natural fats or oils, can be exposed by methods known per se. Such an epoxidation reaction can be carried out, for example, by reacting the fatty acids or their esters of the general formula (II) with organic peroxo acids under suitable conditions. The epoxides obtained in this way, which carry the oxirane ring at the position in the molecule at which the olefinic double bond was found in the starting materials, are then, according to processes which are also known per se, by acid-catalyzed ring opening with alcohols of the general formula

in which R ² can have the meanings given above, converted into the corresponding alkoxyhydroxyfatty acid derivatives in which the alkoxy group R ² 0 and the hydroxyl group are each attached to the two carbon atoms connected in the starting material by the olefinic double bond. Depending on the amount of alcohol used, the terminal ester grouping of the epoxides can also be transesterified.

The esters resulting from this reaction sequence are then saponified by alkaline methods which are also known per se, giving the salts of the general formula (I) in which M represents organic ammonium radicals having one or more alkyl or hydroxyalkyl radicals on the nitrogen atom. If appropriate, the corresponding salts can be converted into the corresponding acids (I) in which M represents hydrogen by adjusting an acidic pH in the reaction medium.

For such reaction sequences, naturally occurring fats and oils of the general formula (11) are preferably used, which are inexpensively available in large quantities from native sources. Soybean oil which has a high content of oleic acid and linoleic acid, sunflower oil, sesame oil, corn oil, cottonseed oil, palm oil or coconut oil are preferred. Such natural fats and oils contain high proportions of esters of unsaturated fatty acids of the general formula (I), in which R 'represents unbranched alyl radicals or alkenyl radicals, for example with 8 carbon atoms. Mixtures of esters of different chain lengths can also be found in such oils of native origin, for example, in soybean oil, mixtures of fatty acid esters of the general formula (11) are found in which R 'represents alkyl and alkenyl radicals with 8 C atoms, the saturated and Unsaturated portions are in a weight ratio of 1: 2. Such compounds are to be regarded as preferably usable in the sense of the present invention.

The alcohols of the general formula (III) used for the alcoholysis of the oxirane ring contain unbranched or branched allyl residues with 1 to 18 carbon atoms or unbranched or branched alkenyl residues with 2 to 18 carbon atoms. Unbranched alkyl radicals or alkenyl radicals with 8 to 18 carbon atoms are to be regarded as preferred, which can also be provided inexpensively in large quantities from native sources. In particular, alcohol mixtures of natural origin are used which have unbranched alkyl radicals with 16 carbon atoms and alkenyl radicals with 18 carbon atoms. Mixtures of cetyl alcohol and oleyl alcohol are to be regarded as such; Reaction products of these alcohol mixtures with epoxidized fatty acids of native origin lead to alkoxyhydroxy fatty acids, which can be used as particularly preferred in the sense of the present invention.

According to the invention, not only the free alkoxyhydroxy fatty acids (I) in which M represents hydrogen, but also their oil-soluble salts (I) in which M represents organic ammonium radicals with one or more alkyl radicals or hydroxyalkyl radicals on the nitrogen atom can be used as corrosion inhibitors. Preferred cations of such salts are ammonium cations which carry two or three alkyl radicals or hydroxyalkyl radicals on the nitrogen atom. Of these, salt (1) in which M stands for a diethanolammonium radical is particularly preferably used.

The alkoxyhydroxy fatty acids mentioned and their salts of the general formula (I) given are used as corrosion inhibitors in lubricating oils, lubricating greases, power transmission oils and metalworking emulsions based on mineral oils. They are used in a wide range of quantities in oils or oil-containing emulsions. The amounts can vary in the range from 0.01 to 10% by weight, based on the oil base, and are preferably from 0.05 to 0.5%. Oils and oil-containing emulsions which contain alkoxyhydroxy fatty acids or their salts of the general formula (I) in these amounts show a corrosion protection on iron and iron-containing metal surfaces which is at least equivalent to that of the compounds known hitherto. The alkoxyhydroxy fatty acids mentioned or their salts are superior to the previously known compounds in that they can be made inexpensively accessible in large quantities from natural raw materials.

The invention is illustrated by the examples below.

For the use according to the invention, the compounds of Table 1 below were prepared according to the route described above, and their solubility in oils of different characters is also given in Table 1.

example 1

• 0: keine Korrosion,
• 1: Spuren von Korrosion,
• 2: leichte Korrosion (korrodierte Fläche 5%),
• 3: Mäßige Korrosion (korrodierte Fläche im Bereicht von 5 bis 20%), und
• 4: starke Korrosion (korrodierte Fläche 20%).
• Die Ergebnisse sind den nachfolgenden Tabellen 2 und 3 zu entnehmen.

Degreased and sanded steel rods (material: CK15 according to DIN 17 210) were subsequently mixed for 24 hours in stirred mixtures of mineral oil and distilled water in a ratio of 10: 1 (procedure A) or mineral oil and artificial sea water (ratio 10: 1) (procedure B) DIN 51585 stored at 60 ° C. After the prescribed test period, the test specimens were assessed for signs of corrosion. The evaluation followed the following evaluation scale:

• 0: no corrosion,
• 1: traces of corrosion,
• 2: slight corrosion (corroded area 5%),
• 3: moderate corrosion (corroded area in the range of 5 to 20%), and
• 4: severe corrosion (corroded area 20%).
• The results are shown in Tables 2 and 3 below.

Comparative Examples 1 and 2

For comparison, identical test specimens were stored in solutions without inhibitor (see FIG. 1) or in the corresponding mixtures which contained a commercially available alkenylsuccinic acid half-ester, the concentration of which corresponded to the concentration of the alkoxyhydroxy fatty acids used according to the invention (see FIG. 2). The results are also shown in Tables 2 and 3 below.

Example 2

Gray cast iron filter paper test according to DIN 51360 / Part 2.

In this test method, gray cast iron chips were wetted on a round filter with an oil emulsion in water contaminated with chloride or hardness, which were produced using alkoxyhydroxy fatty acids or their salts of the general formula (I) according to the invention. 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 the corresponding concentrates by customary methods using water with a total hardness of 3.58 mmol CaCl ₂ .6H ₂ O and MgSO ₄ .7H ₂ O.

The recipes used were made using the following concentrates:

All percentages are percentages by weight.

The emulsions were prepared by stirring 8 to 25% by weight of the stated concentrates (formulations 1 and 2) in water with the stated total hardness. This corresponds to DIN 51360 / Part 2.

The results are shown in Table 4 below.

• 0: keine Korrosion,
• 1: Spuren von Korrosion, 1₀
• 2: leichte Korrosion (korrodierte Fläche 1%),
• 3: mäßige Korrosion (korrodierte Fläche im Bereich von 1 bis 5%), und
• 4: starke Korrosion (korrodierte Fläche 5%).

The degree of corrosion was assessed as follows:

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

Comparative Example 3

Analogously to Example 2, an emulsion was used which did not contain an inhibitor of the general formula (I). In this comparison emulsion, the ratio of naphthenic mineral oil: emulsifier (adduct of 6.5 EO with nonylphenol) was 4: 1.

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

Example 3

Another corrosion protection test was carried out in which sanded steel sheets (ST 1405), dimensions: 25 x 50 mm, were kept in stirred mineral oil emulsions at elevated temperature. Two rotating steel sheets of the same composition, size and surface quality were exposed to a chloride and hardness-stressed mineral oil emulsion at 50 ° C for three days and after the test period the mass losses of both sheets were determined and averaged gravimetrically.

The corrosion protection S was then calculated in% according to the following equation from the comparison of the results with the averaged removals in the case of a blank sample made from inhibitor-free emulsion:

• G_o: Gewichtsdifferenz des Prüfblechs vor und nach der Lagerung in inhibitorfreier Emulsion, und
• G,: Gewichtsdifferenz des Prüfblechs vor und nach der Lagerung in inhibitorhaltiger Emulsion.

In the equation:

• G _o : weight difference of the test sheet before and after storage in an inhibitor-free emulsion, and
• G ,: Weight difference 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 analogy to Example 3, steel sheets were kept under the same reaction conditions in a mineral oil emulsion which contained no inhibitor. The mineral oil: emulsifier weight ratio in this emulsion was 4: 1.

The results are also shown in Table 5 (cf. 4).

Example 4

In a further corrosion test, steel sheets (quality ST 1405, degreased and sanded, dimensions: 25 x 50 mm) were immersed in mineral oil emulsions which had been produced using the substances used according to the invention. Different amounts of inhibitor were used in the mineral oil emulsions. After a certain draining and drying time, the sheets were stored in a humidity chamber at 100% relative atmospheric humidity. After the test period (1 to 7 days), the steel sheets were checked for signs of corrosion. The evaluation was carried out on the evaluation scale given in Example 1 from 0 to 4.

The results are shown in Table 6 below.

Comparative Example 5

According to the conditions given in Example 4, identical steel sheets of the same size were stored in mineral oil emulsions which did not contain an inhibitor. The comparison emulsions contained naphthenic mineral oil and emulsifier (adduct of 6.5 EO with nonylphenol) in a weight ratio of 4: 1.

The results of the comparative tests can also be found in Table 6 below (see FIG. 5).

Claims (10)

1. The use of alkoxyhydroxy fatty acids corresponding to general formula (I)

in which R' represents unbranched alkyl or alkenyl radicals containing 6 to 8 C atoms, R² represents unbranched or branched alkyl radicals containing 1 to 18 C atoms or unbranched or branched alkenyl radicals containing 2 to 18 C atoms, M represents hydrogen or organic ammonium residues containing one or more alkyl groups or hydroxyalkyl groups at the nitrogen atom and m is an integer of 3 to 13, or salts thereof in quantities of 0.01 to 10% by weight, based on oil, as corrosion inhibitors in oils and oil-containing emulisons.

2. The use claimed in claim 1, characterized in that, in the compounds of general formula (I), R' is an alkyl radical or alkenyl radical containing 8 C atoms.

3. The use claimed in claims 1 and 2, characterized in that, in the compounds of general formula (I), R¹ represents alkyl radicals and alkenyl radicals containing 8 C atoms in a ratio of 1:2.

4. The use claimed in claims 1 to 3, characterized in that, in the compounds corresponding to general formula (I), m is an integer of 7 to 11.

5. The use claimed in claims 1 to 4, characterized in that, in the compounds corresponding to general formula (I), R² represents unbranched alkyl radical or alkenyl radicals containing 8 to 18 C atoms.

6. The use claimed in claims 1 to 5, characterized in that, in the compounds corresponding to general formula (I), R² represents art unbranched alkyl radical containing 16 C atoms and an unbranched alkenyl radical containing 18 C atoms.

7. The use claimed in claims 1 to 6, characterized in that, in the compounds corresponding to general formula (I), M represents hydrogen.

8. The use claimed in claims 1 to 6, characterized in that, in the compounds corresponding to general formula (I), M represents a group NH₂(C₂H₄0H)₂.

9. The use claimed in claims 1 to 8, characterized in that the compounds of general formula (I) are used in quantities of 0.05 to 0.5% by weight, based on oil.

10. The use of alkoxyhydroxy fatty acids corresponding to formula (I) and salts thereof as corrosion inhibitors in lubricating oils, lubricating greases, power transmission oils and metal-working emulsions based on mineral oils.