EP0144739A2 - Corrosion inhibitor - Google Patents

Abstract

Reaction products of a) conjugated polyunsaturated fatty acid esters, which contain 16 to 22 C atoms in the fatty acid radical and 1 to 10, preferably 1 to 4, C atoms in the alcohol radical, and b) fumaric acid and also c) subsequently reacted further with ammonia and primary or secondary amines having alkyl radicals of chain lengths 1 to 22 C atoms or with alcohols in place of c) are used as corrosion inhibitors in mineral-oil based lubricating oils and lubricating greases. Quantities of 0.1 to 10 per cent by weight - relative to the mineral oil base - are used.

Description

The invention relates to the use of certain reaction products of fatty acid esters and fumaric acid and the subsequent further reaction with ammonia or alkylamines or with alcohols as corrosion inhibitors in lubricating oils and lubricating greases based on mineral oils.

• _a) konjugiert mehrfach ungesättigten Fettsäureestern, die im Fettsäurerest 16 bis 22 C-Atome und im alkoholischen Rest 1 bis 10, vorzugsweise 1 bis 4 C-Atome enthalten und
• b) Fumarsäure sowie
• c) nachfolgendeT weiterer Umsetzung mit Ammoniak und primären beziehungsweise sekundären Aminen mit Alkylresten der Kettenlängen 1 bis 22 C-Atomen oder anstelle von c) mit Alkoholen

als Korrosionsschutzmittel in Schmierölen und Schmierfetten auf Mineralölbasis.Reaction products find use in detail

• _a ) conjugates polyunsaturated fatty acid esters containing 16 to 22 carbon atoms in the fatty acid residue and 1 to 10, preferably 1 to 4 carbon atoms in the alcoholic residue and
• b) fumaric acid and
• c) subsequent reaction with ammonia and primary or secondary amines with alkyl radicals with chain lengths of 1 to 22 carbon atoms or instead of c) with alcohols

as a corrosion protection agent in lubricating oils and greases based on mineral oil.

Esters of polyunsaturated fatty acids containing conjugated double bonds are therefore suitable as starting materials. This is obtained by isomerization, for example with alkali, of fatty acid mixtures, which occur naturally when severing highly unsaturated oils or when fractionating fatty acid mixtures into unsaturated and saturated fractions.

The esters of the conjugated fatty acids react with fumaric acid to form cyclohexenyl compounds. In this way, tricarboxylic acid monoesters are formed with fumaric acid. At temperatures of 200 to 270 ° C, these compounds change into cyclic anhydrides, which means that the two carboxyl groups on the cyclohexene ring split off one mole of water.

Ammonia, primary or secondary as well as straight-chain or branched alkylamines are used for the reaction. Amines in which the number of carbon atoms in the alkyl radicals is 1 to 22, such as butylamine, dibutylamine, octylamine, 2-ethylhexylamine, dodecylamine, octadecylamine, are particularly suitable. Tricarboxylic acid mono-ester-mono-amides are formed.

The alcohols used for the reaction can be straight-chain or branched. The number of their carbon atoms can be 1 to 22. The following alcohols are particularly suitable: methyl alcohol, ethyl alcohol, isopropyl alcohol, octanol, 2-ethylhexyl alcohol and 1,2-diols. Tricarboxylic acid diesters are formed during the reaction.

The 1,2-diols can be made from α-epoxides. The number of carbon atoms in the 1,2-diols can be 3 to 18, in particular propylene glycol, 1,2-dihydroxyoctane, 1,2-dihydroxydodecane are used. Tricarboxylic acid di-esters are also formed here.

The derivatives according to the invention are generally viscous oils which are readily soluble in mineral oil.

The amounts used are between 0.1 and 10%, preferably 0.5 to 2%, based on the mineral oil base.

The subject matter of the invention is explained again in the following examples, without being limited thereto.

example 1

• a) Preparation of Fumarsäureaddukts of conjugated unsaturated _{Fettsäureestern:;} Technically conjugated fatty acid (approx. 58% conjugated fatty acid, Woburn iodine number approx. 140) based on sunflower oil is esterified with methanol in the presence of sulfuric acid. The main fraction of the distillation is a fatty acid methyl ester, about 58% of which contain two conjugated double bonds.
  1000 g of the 58% conjugated unsaturated fatty acid methyl ester are slowly heated to 200 ° C. while stirring with 230 g of fumaric acid and 600 mg of sulfur. After a further 30 minutes at 200 ° C., the reaction, which is accelerated by the addition of a small amount of sulfur, has ended. The unreacted portion of fatty acid methyl ester is separated off by distillation, the temperature exceeding 200 ° C. The end product (770 g) has an iodine number of about 65 and the IR spectrum indicates that an ester group and a cyclic anhydride group are present.
• b) Reaction of the fumaric acid adduct with ammonia. 4.2 g of ammonia gas are passed into 100 g of the fumaric acid adduct obtained while stirring at 80-90 ° C.
• c) The reaction with amines takes place at max. 80 ° C. The calculated amount of amine is added to the fumaric acid adduct from about 50 ° C within about 30 minutes. Then it is heated to 80 ° C. for a further 30 minutes.

Example 2

• a) Zur Umsetzung des Fumarsäureadduktes (siehe Beispiel 1a) mit Methylalkohol zum Partialester werden 100 g des Fumarsäureadduktes mit 20 g Methanol 30 Min. unter Rückfluß erhitzt. Der Methanolüberschuß wird darauf im Vakuum abdestilliert, zurück bleibt der Tricarbonsäure-dimeth^ylester
• b) Zur Umsetzung des Fuma_Tsäureadduktes (siehe Beispiel la) mit Octandiol-1,2 werden 80 g des Fumarsäureadduktes mit der berechneten Menge des Diols (30 g) 1 Stunde auf 90 °C unter Rühren erhitzt.

Production of tricarboxylic acid di-esters

• a) To react the fumaric acid adduct (see Example 1a) with methyl alcohol to form the partial ester, 100 g of the fumaric acid adduct are refluxed with 20 g of methanol for 30 minutes. The excess methanol is subsequently removed by vacuum distillation, remains the tricarboxylic dimeth ^y lester
• b) acid adduct To implement the Fuma _T (see example la) using 1,2-octanediol, 80 g of fumaric acid-adduct with the calculated amount of the diol (30 g) for 1 hour at 90 ° C. with stirring.

Example 3

The results are shown below, which were obtained with the test duration of different lengths using the condensation water test according to DIN 51359. The test procedure is carried out as follows: steel sheets of a certain composition, external shape and surface quality are immersed in the sample and, after a certain period of draining or drying, are hung in the humidity chamber in which, with continuous air supply, 875 1 / h and a temperature of 50 ° C the relative humidity should be 100%. After the prescribed test duration, the steel sheets are assessed for signs of corrosion.

The steel sheets were degreased and sanded. The test duration and the concentration of mineral oil on rust inhibitors are shown in Tables 1 to 3 below.

• 0 keine Korrosion
• 1 Spuren von Korrosion
• 2 leichte Korrosion (K'=5 %)
• 3 mäßige Korrosion (5 %>K=20 %)
• 4 starke Korrosion (K > 20 %).

The evaluation was carried out as follows:

• 0 no corrosion
• 1 traces of corrosion
• 2 slight corrosion (K '= 5%)
• 3 moderate corrosion (5%> K = 20%)
• 4 severe corrosion (K> 20%).

• A:
  • Konjuenfettsäure-methylester-fumarsäure-addukt gemäß Beispiel 1 a) mit NH₃ umgesetzt
• B:
  • Addukt wie A, jedoch mit 2-Ethylhexylamin umgesetzt
• C:
  • Addukt wie A, jedoch mit Methanol umgesetzt

• D:
  • Addukt wie A, jedoch mit 2-Ethylhexanol umgesetzt
• E:
  • Addukt wie A. jedoch mit 1,2-Dihydroxyoctanol umgesetzt
• F:
  • Konjuenfettsäure-2-ethylhexyl-ester-fumarsäure-addukt mit Methanol umgesetzt

The following connections are designated by A to F:

• A:
  • Conjugated fatty acid methyl ester-fumaric acid adduct according to Example 1 a) reacted with NH ₃
• B:
  • Adduct as A, but reacted with 2-ethylhexylamine
• C:
  • Adduct as A, but reacted with methanol

• D:
  • Adduct as A, but reacted with 2-ethylhexanol
• E:
  • Adduct as A. but implemented with 1,2-dihydroxyoctanol
• F:
  • Conjugated fatty acid 2-ethylhexyl ester fumaric acid adduct reacted with methanol

Testing of rust inhibitors in mineral oil-based lubricating oils according to DIN 51 359 (humidity chamber) Steel sheets 088 St-1405: degreased, sanded Temperature: 50 ° C

Example 4:

The results are shown below, which were obtained using the sea water immersion test according to DIN 51 358.

• Stahlbleche bestimmter Zusammensetzung, äußerer Form und Oberflächengüte werden in die Lösung des mit dem Inhibitor legierten Korrosionsschutzöls getaucht und nach einer bestimmten Abtropfzeit 20 Stunden in ruhendes künstliches Meerwasser gehängt. Anschließend werden die Stahlbleche auf Korrosionserscheinungen beurteilt.

The test procedure is carried out as follows: '

• Steel sheets of a certain composition, external shape and surface quality are immersed in the solution of the corrosion protection oil alloyed with the inhibitor and, after a certain draining time, hung in still artificial sea water for 20 hours. The steel sheets are then assessed for signs of corrosion.

The steel sheets were degreased and sanded. The test duration and the concentration of mineral oil on rust inhibitors is shown in the table below.

The evaluation was carried out as in Example 3.

Testing of rust inhibitors in mineral oil-based lubricating oils according to DIN 51 358 (seawater immersion test)

Temperature: 20 ° C

Time: 20 hours

Example 5:

The results are shown below, which were obtained using the mineral oil / water stirring test according to DIN 51 585.

• Stahlstäbe bestimmter Zusammensetzung werden bei 60° C in eine gerührte Mischung aus Mineralöl/Wasser (Methode A) oder aus Mineralöl/künstlichem Meerwasser (Methode B) über 24 Stunden getaucht, wobei das Öl-/Wasser-Volumenverhältnis 10:1 und die Rührerdrehzahl 1000 UpM betragen.

The stirring process is carried out as follows:

• Steel rods of a certain composition are immersed at 60 ° C in a stirred mixture of mineral oil / water (method A) or mineral oil / artificial sea water (method B) for 24 hours, the oil / water volume ratio being 10: 1 and the stirrer speed 1000 Rpm.

The rods are then assessed for signs of corrosion. The steel bars were degreased and sanded.

The concentration of mineral oil in rust inhibitors is shown in the table below.

The evaluation was carried out as indicated in Example 3.

Testing of rust inhibitors in mineral oil-based lubricating oils according to DIN 51 585 (oil / water stirring test)

Steel rods CK 15, degreased, sanded

Temperature: 60 ° C

Time: 24 hours

Method A: oil / water

Method B: Oil / artificial sea water

Claims (5)

1. Use of reaction products a) conjugates polyunsaturated fatty acid esters containing 16 to 22 carbon atoms in the fatty acid residue and 1 to 10, preferably 1 to 4 carbon atoms in the alcoholic residue, and b) fumaric acid and c) subsequent further reaction with ammonia and primary or secondary amines with alkyl radicals with chain lengths of 1 to 22 carbon atoms or instead of c) with alcohols as corrosion inhibitors in lubricating oils and lubricating greases based on mineral oils. 2. Use of reaction products according to claim 1, characterized in that the alcoholic radical in the fatty acid esters contains 2 to 4 carbon atoms. 3. Use according to claim 1, characterized in that the reaction with amines of chain length 4 to 18 is carried out. 4. Use according to claim 1, characterized in that the 1,2-diols contain 3 to 18 carbon atoms. 5. Use according to claim 1 in an amount of 0.1 to 10, preferably 0.5 to 2%, based on the mineral oil base.