DE102011005441A1 - Use of acids having aliphatic hydrocarbon groups or their salts as corrosion inhibitors in a composition containing an ionic liquid e.g. an imidazolium salt compound - Google Patents

Abstract

Use of acids having at least 8C-aliphatic hydrocarbon groups or their salts as corrosion inhibitors in a composition containing at least one ionic liquid, is claimed. An independent claim is included for a composition comprising salts or acids having at least 8C-aliphatic hydrocarbon groups as corrosion inhibitors and at least one ionic liquid.

Description

The invention relates to the use of acids having an aliphatic hydrocarbon group of at least 8 carbon atoms or salts thereof as corrosion inhibitors in compositions containing at least one ionic liquid.

The invention also relates to compositions containing salts or acids having an aliphatic hydrocarbon group of at least 8 C atoms as corrosion inhibitors and at least one ionic liquid.

In particular, the invention also relates to compositions which consist of more than 40% by weight of ionic liquids and contain at least one carboxylic acid or a carboxylate having an aliphatic hydrocarbon group of 8 to 26 carbon atoms and a carboxylic acid or a carboxylate group as corrosion inhibitor.

Ionic liquids are suitable for. As a lubricant, hydraulic fluid or other work equipment and come in such uses in contact with equipment or analagen parts of metals.

Many metals and alloys show signs of corrosion in the presence of ionic liquids. Corrosion on a problematic scale can occur, in particular, in simple, unalloyed steels, which are frequently used as material in plant engineering and mechanical engineering.

To avoid or reduce corrosion phenomena, the addition of so-called corrosion inhibitors is known. For common lubricating oils many different corrosion inhibitors are described.

The addition of a corrosion inhibitor to an ionic liquid which is used as lubricating oil is the subject of an article of X. Liu, F. Zhou, Y. Lang and W. Liu in Tribology Letters (2006), 23 (3), 191-196 , This article describes the addition of benzotriazoles as a corrosion inhibitor to a liquid imidazolium salt. Particular demands are placed on corrosion inhibitors for ionic liquids, in particular they should dissolve well in the ionic liquids, be compatible with the ionic liquids and remain in the system under the conditions of later use of the ionic liquids and not evaporate, be washed out or otherwise from the System escape.

What is desired are alternative and possibly more effective in ionic liquids corrosion inhibitors.

Object of the present invention were therefore mixtures of ionic liquids and corrosion inhibitors, which are used for a wide variety of uses, eg. As lubricating oil and hydraulic fluid, come into question and have no or at most only a slight corrosive effect in systems or plant components made of metals.

Accordingly, the use defined above was found.

According to the invention, acids having an aliphatic hydrocarbon group of at least 8 C atoms or salts thereof are used as corrosion inhibitors in compositions containing at least one ionic liquid.

To the compositions

The compositions are in their use, for. B. as a lubricant or hydraulic fluid usually liquid. Since the use can be carried out at a significantly elevated temperature, it is also possible to use compositions which are still solid under normal conditions (1 bar, 21 ° C.) but then become liquid during use.

The compositions are preferably liquid under normal conditions (1 bar, 21 ° C.).

The compositions preferably consist of more than 40% by weight, in particular more than 60% by weight and particularly preferably more than 80% by weight, of ionic liquids.

The weight specifications are based on the entire composition, which already contains the corrosion inhibitors.

The composition may contain an ionic liquid or a mixture of several ionic liquids. It may contain other constituents in addition to the ionic liquids and the corrosion inhibitor (s). Particularly suitable are water or organic solvents, in particular organic solvents miscible with ionic liquids, such as alcohols, and additives such as thickeners, stabilizers or defoamers.

To the ionic liquids

The term ionic liquid is understood as meaning salts (compounds of cations and anions) which at normal pressure (1 bar) have a melting point of less than 200 ° C., preferably less than 150 ° C., more preferably less than 100 ° C. and most preferably less than 80 ° C. have.

In a particularly preferred embodiment, the ionic liquids used herein under normal conditions (1 bar, 21 ° C), d. H. at room temperature, liquid.

Preferred ionic liquids contain an organic compound as a cation (organic cation). Depending on the valence of the anion, the ionic liquid may contain other cations, including metal cations, in addition to the organic cation.

The cations of particularly preferred ionic liquids are exclusively an organic cation or, in the case of polyvalent anions, a mixture of different organic cations.

Suitable organic cations are, in particular, organic compounds containing heteroatoms, such as nitrogen, sulfur, oxygen or phosphorus; in particular, the organic cations are compounds having an ammonium group (ammonium cations), an oxonium group (oxonium cations), a sulfonium group (sulfonium cations) or a phosphonium group (phosphonium cations).

In a particular embodiment, the organic cation of the ionic liquids is ammonium cations, including non-aromatic compounds having a localized positive charge on the nitrogen atom, e.g. B. compounds with tetra-nitrogen (quaternary ammonium compounds) or compounds with trivalent nitrogen, wherein a bond is a double bond, or aromatic compounds with delocalized positive charge and at least one, preferably one or two nitrogen atoms in the aromatic ring system are understood.

Preferred organic cations are quaternary ammonium cations, preferably those having three or four aliphatic substituents, more preferably C1 to C12 alkyl groups, on the nitrogen atom, which may optionally be substituted by hydroxyl groups.

Also preferred are organic cations containing a heterocyclic ring system having one or two nitrogen atoms as part of the ring system. Suitable compounds are monocyclic, bicyclic, aromatic or non-aromatic ring systems. Called z. B. bicyclic systems, as described in WO 2008/043837 are described. The bicyclic systems of WO 2008/043837 are diazabicyclo derivatives, preferably from a 7- and a 6-ring, which contain an amidinium group; in particular, the 1,8-diazabicyclo (5.4.0) undec-7-enium cation may be mentioned.

Very particularly preferred organic cations comprise a five- or six-membered heterocyclic ring system having one or two nitrogen atoms as part of the ring system.

As such organic cations into consideration, for. Pyridinium cations, pyridazinium cations, pyrimidinium cations, pyrazinium cations, imidazolium cations, pyrazolium cations, pyrazolinium cations, imidazolinium cations, thiazolium cations, triazolium cations, pyrrolidinium cations and imidazolidinium cations. These cations are z. In WO 2005/113702 listed. As far as it is necessary for a positive charge on the nitrogen atom or in the aromatic ring system, the nitrogen atoms are in each case by an organic group having generally not more than 20 C atoms, preferably a hydrocarbon group, in particular a C1 to C16 alkyl group, in particular a C1 to C10 , particularly preferably a C1 to C4 alkyl groups substituted.

The carbon atoms of the ring system can also be substituted by organic groups having generally not more than 20 C atoms, preferably a hydrocarbon group, in particular a C1 to C16 alkyl group, in particular a C1 to C10, particularly preferably a C1 to C4 alkyl groups.

Particularly preferred ammonium cations are quaternary ammonium cations, imidazolium cations, pyrimidinium cations and pyrazolium cations.

Very particular preference is given to imidazolium cations, in particular those as listed in formula 1 below.

The ionic liquids may contain inorganic or organic anions. Such anions are z. B. in the above WO 03/029329 . WO 2007/076979 . WO 2006/000197 and WO 2007/128268 listed.

der Gruppe der Methide der allgemeinen Formel:

der Gruppe der Alkoxide und Aryloxide der allgemeinen Formeln:
R^aO^–;
der Gruppe der Halometallate der allgemeinen Formel
[M_rHal_t]^s,
wobei M für ein Metall und Hal für Fluor, Chlor, Brom oder Iod steht, r und t ganze positive Zahlen sind und die Stöchiometrie des Komplexes angeben und s eine ganze positive Zahl ist und die Ladung des Komplexes angibt;
der Gruppe der Sulfide, Hydrogensulfide, Polysulfide, Hydrogenpolysulfide und Thiolate der allgemeinen Formeln:
S^2–, HS^–, [S_v]^2–, [HS_v]^–, [R^aS]^–,
wobei v eine ganze positive Zahl von 2 bis 10 ist; und
der Gruppe der komplexen Metallionen wie Fe(CN)₆ ^3–, Fe(CN)₆ ^4–, MnO₄ ^–, Fe(CO)₄ ^–.In particular, such an anion may be considered
the group of halides and halogen-containing compounds of the formulas:
F ^-, Cl ^-, Br ^-, I ^-, BF ₄ ^-, PF ₆ ^-, AlCl ₄ ^-, Al ₂ Cl ₁₀ ^-, Al ₃ Cl ₁₀ ^-, AlBr ₄ ^-, FeCl ₄ ^-, BCl ₄ ^-, SbF ₆ ^-, AsF ₆ ^-, ZnCl ₃ ^-, SnCl ₃ ^-, CuCl ₂ ^-, CF ₃ SO ₃ ^-, (CF ₃ SO _{3) 2} N ^-, CF ₃ CO ₂ ^-, CCl ₃ CO ₂ ^-, CN ^-, SCN ^- , OCN ^- , NO ² , NO ³ , N (CN) ^- ;
the group of sulfates, sulfites and sulfonates of the general formulas:
SO ₄ ^2- , HSO ₄ ^- , SO ₃ ^2- , HSO ₃ ^- , R ^a OSO ₃ ^- , R ^a SO ₃ ^- ;
the group of phosphates of the general formulas:
PO ₄ ^3- , HPO ₄ ^2- , H ₂ PO ₄ ^- , R ^a PO ₄ ^2- , HR ^a PO ₄ ^- , R ^a R ^b PO ₄ ^- ;
the group of phosphonates and phosphinates of the general formula:
R ^a HPO ₃ ^- , R ^a R ^b PO ₂ ^- , R ^a R ^b PO ₃ ^- ;
the group of phosphites of the general formulas:
PO ₃ ^3- , HPO ₃ ^2- , H ₂ PO ₃ ^- , R ^a PO ₃ ^2- , R ^a HPO ₃ ^- , R ^a R ^b PO ₃ ^- ;
the group of phosphonites and phosphinites of the general formula:
R ^a R ^b PO ₂ ^- , R ^a HPO ₂ ^- , R ^a R ^b PO ^- , R ^a HPO ^- ;
the group of carboxylates of the general formulas:
R ^a COO ^- ;
the group of the bristles of the general formulas:
BO ₃ ^3- , HBO ₃ ^2- , H ₂ BO ₃ ^- , R ^a R ^b BO ₃ ^- , R ^a HBO ₃ ^- , R ^a BO ₃ ^2- , B (OR ^a ) (OR ^b ) (OR ^c ) (OR ^d ) ^- , B (HSO ₄ ) ^- , B (R ^a SO4) ^- ;
the group of boronates of the general formulas:
R ^a BO ₂ ^2- , R ^a R ^b BO ^- ;
the group of carbonates and carbonic esters of the general formulas:
HCO ₃ ^- , CO ₃ ^2- , R ^a CO ₃ ^- ;
the group of silicates and silicic acid esters of the general formulas:
SiO ₄ ^4- , HSiO ₄ ^3- , H ₂ SiO ₄ ^2- , H ₃ SiO ₄ ^- , R ^a SiO ₄ ^3- , R ^a R ^b SiO ₄ ^2- , R ^a R ^b R ^c SiO ₄ ^- , HR ^a SiO ₄ ^2- , H ₂ R ^a SiO ₄ ^- , HR ^a R ^b SiO ₄ ^- ;
the group of the alkyl or aryl silane salts of the general formulas:
R ^a SiO ₃ ^3-, R ^a R ^b SiO ₂ ^2-, R ^a R ^b R ^c SiO ^-, R ^a R ^b R ^c SiO ₃ ^-, R ^a R ^b R ^c SiO ₂ ^-, R ^a R ^b SiO ₃ ^2- ;
the group of carboximides, bis (sulfonyl) imides and sulfonylimides of the general formulas:

the group of methides of the general formula:

the group of alkoxides and aryloxides of the general formulas:
R ^a O ^- ;
the group of halometalates of the general formula
[M _r Hal _t ] ^s ,
where M is a metal and Hal is fluoro, chloro, bromo or iodo, r and t are integer positive numbers and indicate the stoichiometry of the complex and s is an integer positive number indicating the charge of the complex;
the group of sulfides, hydrogen sulfides, polysulfides, hydrogen polysulfides and thiolates of the general formulas:
S ^2-, HS ^-, [S _v] ^2-, [HS _v] ^- [R ^a S] ^-,
where v is a whole positive number from 2 to 10; and
the group of complex metal ions such as Fe (CN) ₆ ^3- , Fe (CN) ₆ ^4- , MnO ₄ ^- , Fe (CO) ₄ ^- .

In the above anions, R ^a , R ^b , R ^c and R ^d are each independently
Hydrogen;
C ₁ -C ₃₀ -alkyl and their aryl, heteroaryl, cycloalkyl, halogen, hydroxy, amino, carboxy, formyl, -O-, -CO-, -CO-O- or -CO- N <substituted components such as methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, 2-methyl-1-propyl (isobutyl), 2-methyl-2-propyl (tert-butyl ), 1-pentyl, 2-pentyl, 3-pentyl, 2-methyl-1-butyl, 3-methyl-1-butyl, 2-methyl-2-butyl, 3-methyl-2-butyl, 2.2- Dimethyl 1-propyl, 1-hexyl, 2-hexyl, 3-hexyl, 2-methyl-1-pentyl, 3-methyl-1-pentyl, 4-methyl-1-pentyl, 2-methyl-2-pentyl, 3-methyl-2-pentyl, 4-methyl-2-pentyl, 2-methyl-3-pentyl, 3-methyl-3-pentyl, 2,2-dimethyl-1-butyl, 2,3-dimethyl-1 butyl, 3,3-dimethyl-1-butyl, 2-ethyl-1-butyl, 2,3-dimethyl-2-butyl, 3,3-dimethyl-2-butyl, heptyl, octyl, nonyl, decyl, undecyl, Dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, icosyl, henicosyl, docosyl, tricosyl, tetracosyl, pentacosyl, hexacosyl, heptacosyl, octacosyl, nonacosyl, triacontyl, phenylmethyl (benzyl), di phenylmethyl, triphenylmethyl, 2-phenylethyl, 3-phenylpropyl, cyclopentylmethyl, 2-cyclopentylethyl, 3-cyclopentylpropyl, cyclohexylmethyl, 2-cyclohexylethyl, 3-cyclohexylpropyl, methoxy, ethoxy, formyl, acetyl or C _q F _{2 (qa) + (1 b )} H _{2a + b} with q ≤ 30, 0 ≤ a ≤ q and b = 0 or 1 (for example CF ₃ , C ₂ F ₅ , CH ₂ CH ₂ -C _(q-2) F _{2 (q-2 ) +1} , C ₆ F ₁₃ , C ₈ F ₁₇ , C ₁₀ F ₂₁ , C ₁₂ F ₂₅ );
C ₃ -C ₁₂ cycloalkyl and their aryl, heteroaryl, cycloalkyl, halogen, hydroxy, amino, carboxy, formyl, -O-, -CO- or -CO-O-substituted components, such as for example cyclopentyl, 2-methyl-1-cyclopentyl, 3-methyl-1-cyclopentyl, cyclohexyl, 2-methyl-1-cyclohexyl, 3-methyl-1-cyclohexyl, 4-methyl-1-cyclohexyl or C _q F _{2 ( qa) (1-b)} H _2a-b with q ≤ 30, 0 ≤ a ≤ q and b = 0 or 1;
C ₂ -C ₃₀ alkenyl and their aryl, heteroaryl, cycloalkyl, halogen, hydroxy, amino, carboxy, formyl, -O-, -CO- or -CO-O-substituted components, such as For example, 2-propenyl, 3-butenyl, cis-2-butenyl, trans-2-butenyl or C _q F _{2 (qa) - (1-b)} H _2a-b with q ≤ 30, 0 ≤ a ≤ q and b = 0 or 1;
C ₃ -C ₁₂ cycloalkenyl and their aryl, heteroaryl, cycloalkyl, halogen, hydroxy, amino, carboxy, formyl, -O -, - CO- or -CO-O-substituted components, such as For example, 3-cyclopentenyl, 2-cyclohexenyl, 3-cyclohexenyl, 2,5-cyclohexadienyl or C _q F _{2 (qa) -3 (1-b)} H _2a-3b with q ≤ 30, 0 ≤ a ≤ q and b = 0 or 1;
Aryl or heteroaryl having 2 to 30 carbon atoms and their alkyl, aryl, heteroaryl, cycloalkyl, halogen, hydroxy, amino, carboxy, formyl, -O-, -CO- or -CO-O- substituted components such as phenyl, 2-methylphenyl (2-tolyl), 3-methylphenyl (3-tolyl), 4-methylphenyl, 2-ethylphenyl, 3-ethylphenyl, 4-ethyl -phenyl, 2,3-dimethyl-phenyl, 2,4-dimethyl-phenyl, 2,5-dimethyl-phenyl, 2,6-dimethyl-phenyl, 3,4-dimethyl-phenyl, 3,5-dimethyl-phenyl , 4-phenyl-phenyl, 1-naphthyl, 2-naphthyl, 1-pyrrolyl, 2-pyrrolyl, 3-pyrrolyl, 2-pyridinyl, 3-pyridinyl, 4-pyridinyl or C ₆ F _(5-a) H _a with 0 ≤ a ≤ 5; or
two radicals are an unsaturated, saturated or aromatic, optionally substituted by functional groups, aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms and / or heterocycles and optionally substituted by one or more oxygen and / or sulfur atoms and / or one or more substituted or unsubstituted imino groups interrupted ring.

In the above anions, R ^a , R ^b , R ^c and R ^{d are} preferably each independently a hydrogen atom or a ^{C 1 to C} 12 alkyl group.

As anions are mentioned z. B. chloride; Bromide; iodide; thiocyanate; hexafluorophosphate; trifluoromethanesulfonate; methane; the carboxylates, in particular formate; Acetate; mandelate; Nitrate; Nitrite; trifluoroacetate; Sulfate; Bisulfate; Methyl sulfate; ethyl sulfate; 1-propyl sulfate; 1-butyl sulfate; 1-hexyl sulfate; 1-octyl sulfate; Phosphate; dihydrogen; Hydrogen phosphate; C1-C4-dialkyl; propionate; tetrachloroaluminate; Al2Cl7-; chlorozincate; Chloroferrat; imide, bis (trifluoromethylsulfonyl); Bis (pentafluoroethylsulfonyl) imide; Bis (methylsulfonyl) imide; Bis (p-Tolyfsulfonyl) imide; Tris (trifluoromethylsulfonyl) methide; Bis (pentafluoroethylsulfonyl) methide; p-tolylsulfonate; tetracarbonylcobaltate; Dimethylenglykolmonomethylethersulfat; oleate; stearate; acrylate; methacrylate; maleate; hydrogen citrate; vinylphosphonate; Bis (pentafluoroethyl) phosphinate; Borates such as bis [salicylato (2 -)] borate, bis [oxalato (2 -)] borate, bis [1,2-benzenediolato (2 -) - O, O '] borate, Tetracyano borate, tetrafluoroborate; dicyanamide; Tris (pentafluoroethyl) trifluorophosphate; Tris (heptafluoropropyl) trifluorophosphate, cyclic aryl phosphates such as catechol phosphate (C6H4O2) P (O) O and chlorocobaltate.

Anions are particularly preferably those from the group
the alkyl sulfates
R ^a OSO ₃ ^- ,
wherein R ^{a is} a C 1 to C 12 alkyl group, preferably a C 1 -C 6 alkyl group,
the alkyl sulfonates
R ^a SO ₃ ^- ;
wherein R ^{a is} a C 1 to C 12 alkyl group, preferably a C 1 -C 6 alkyl group,
the halides, in particular chloride and bromide and
the pseudohalides, such as thiocyanate, dicyanamide,
the carboxylates R ^a COO ^- ;
wherein R ^{a is} a C 1 to C 20 alkyl group, preferably a C 1 -C 8 alkyl group, in particular acetate,
the phosphates,
in particular the dialkyl phosphates of the formula R ^a R ^b PO ₄ ^- , wherein R ^a and R ^b independently of one another represent a C 1 to C 6 alkyl group; in particular, R ^a and R ^{b are} the same alkyl group, which may be mentioned dimethyl phosphate and diethyl phosphate
and the phosphonates, in particular the monoalkylphosphonic esters of the formula R ^a R ^b PO ₃ ^- , where R ^a and R ^b independently of one another are a C ₁ to C 6 alkyl group
and the TFSI anion of the formula N (-SO ₂ CF ₃ ) ₂ ^- and tricyanomethamide of the formula (ON) ₃ C ^- .

Very particularly preferred anions are
Chloride, bromide, hydrogensulfate, tetrachloroaluminate, thiocyanate, dicyanamide, methylsulfate, ethylsulfate, methanesulfonate, formate, acetate, dimethylphosphate, diethylphosphate, p-tolylsulfonate, tetrafluoroborate and hexafluorophosphate, methylmethylphosphonate and methylphosphonate, the TFSI anion, tricyanomethamide and trifluoromethanesulfonate.

worin
R1 und R3 für einen organischen Rest mit 1 bis 20 C-Atomen stehen,
R2, R4, und R5 für ein H-Atom oder einen organischen Rest mit 1 bis 20 C-Atomen stehen,
X für ein Anion steht und
n für 1, 2 oder 3 steht.Particularly preferred ionic liquids are imidazolium salts of formula I below:

wherein
R 1 and R 3 represent an organic radical having 1 to 20 C atoms,
R 2, R 4, and R 5 represent an H atom or an organic radical having 1 to 20 C atoms,
X stands for an anion and
n is 1, 2 or 3.

In formula I, R 1 and R 3 are preferably independently an organic radical having 1 to 10 C atoms. In particular, R 1 and R 3 are an aliphatic radical, in particular an aliphatic radical without further heteroatoms, eg. B. for an alkyl group. More preferably, R1 and R3 independently of one another are a C1 to C10 or a C1 to C4 alkyl group.

In formula I, R 2, R 4 and R 5 are preferably independently an H atom or an organic radical having 1 to 10 C atoms; in particular, R 2, R 4 and R 5 represent an H atom or an aliphatic radical. Particularly preferably, R 2, R 4 and R 5 independently of one another are an H atom or an alkyl group, in particular R 2, R 4 and R 5 independently of one another are an H atom or a C1 to C4 alkyl group. Most preferably, R2, R4 and R5 are each an H atom.

X is an anion, preferably one of the abovementioned preferred and particularly preferred anions,
n is preferably 1.

Particularly preferred ionic liquids consist exclusively of an organic cation having one of the above anions.

The molar weight of the ionic liquids is preferably less than 2000 g / mol, more preferably less than 1500 g / mol, more preferably less than 1000 g / mol, and most preferably less than 750 g / mol; in a particular embodiment, the molecular weight is between 100 and 750 or between 100 and 500 g / mol.

To the corrosion inhibitors

The corrosion inhibitors used in the invention are salts or acids having an aliphatic hydrocarbon group of at least 8 C atoms, d. H. these compounds contain at least one acid group or its salt with any cation and also a hydrophobic molecule group in the form of the hydrocarbon group having at least 8 carbon atoms.

The corrosion inhibitors are preferably low molecular weight compounds having a molecular weight of less than 1000 g / mol, in particular less than 500 g / mol.

The aliphatic hydrocarbon group may be saturated or unsaturated, in particular it may contain one, two or three ethylenically unsaturated groups. The aliphatic hydrocarbon group preferably has at least 10 C atoms, more preferably at least 12 C atoms. In general, it has not more than 30 C atoms, especially not more than 26 C atoms. Particularly preferred aliphatic hydrocarbon groups consist for. B. from 12 to 26 carbon atoms and in particular from 14 to 24 carbon atoms.

The corrosion inhibitors may be, for. As acids selected from carboxylic acids, esters of sulfuric acid, esters of phosphoric acid, salts of these acids or mixtures of these compounds.

Be listed in particular
Carboxylic acids of the formula R ¹ -COOH,
Esters of sulfuric acid of the formula: R ¹ -OS (O) -OH,
Esters or diesters of phosphoric acid of the formula:
R ¹ -OP (O) (- OH) ₂ or (R ¹ -O-) ₂ P (O) -OH

In the above formulas, R ^{1 is} the aliphatic hydrocarbon group described above and has the corresponding preferred and particularly preferred meanings.

Preferably, the corrosion inhibitors are carboxylic acids or their salts (carboxylates) having a total of 8 to 26 carbon atoms (including the carbon atom of the carboxyl group), particularly preferably having 10 to 24 carbon atoms, very particularly preferably 12 to 24 C atoms, in a particular embodiment with a total of 18 carbon atoms.

The carboxylic acids or carboxylates can be saturated or unsaturated.

In consideration come z. Saturated carboxylic acids, such as:
Lauric acid (H ₃ C- (CH ₂ ) ₁₀ -COOH),
Palmitic acid (H ₃ C- (CH ₂ ) ₁₄ -COOH),
Stearic acid (H ₃ C- (CH ₂ ) ₁₆ -COOH) or
Cerotic acid (H ₃ C- (CH ₂ ) ₂₄ -COOH).
or the carboxylates of the above carboxylic acids;
as well as mono-, di- or triunsaturated carboxylic acids, such as:
Oleic acid (H ₃ C- (CH ₂ ) ₇ -CH = CH- (CH ₂ ) ₇ -COOH),
Linoleic acid (H ₃ C- (CH ₂ ) ₄ -CH = CH-CH ₂ -CH = CH- (CH ₂ ) ₇ -COOH) or
Linolenic acid (H ₃ C-CH ₂ -CH = CH-CH ₂ -CH = CH-CH ₂ -CH = CH- (CH ₂ ) ₇ -COOH),
or the carboxylates of the above unsaturated carboxylic acids;

In a preferred embodiment, the corrosion inhibitors are tall oil fatty acids, which are oleic acid, linoleic acid, linolenic acid or mixtures thereof, or the corresponding carboxylates of these acids or of the mixtures of these acids.

Usual tall oils contain z. B.
10 to 60% by weight of oleic acid
30 to 80 wt .-% linoleic acid, linolenic acid or mixtures thereof and
0 to 40 wt .-% of other ingredients, eg. B saturated carboxylic acids.

The above tall oil can also be used in the form of the corresponding carboxylates.

In a particularly preferred embodiment, the salts are preferred over the acids; Correspondingly, the corrosion inhibitors are in particular salts selected from carboxylates, salts of sulfuric acid esters or salts of phosphoric acid esters. Particularly preferred are the above carboxylates, especially the carboxylates of tall oils.

In the salts, the acid protons are replaced by suitable cations. In particular, salts with organic cations are suitable.

Suitable organic cations are in particular the cations of ionic liquids listed above, for. B. quaternary ammonium cations, preferably those having three or four aliphatic substituents, more preferably C1 to C12 alkyl groups on the nitrogen atom, which may optionally be substituted by hydroxyl groups, or organic cations comprising a heterocyclic ring system having one or two nitrogen atoms as part of Ringsystems included.

As such organic cations into consideration, for. Pyridinium cations, pyridazinium cations, pyrimidinium cations, pyrazinium cations, imidazolium cations, pyrazolium cations, pyrazolinium cations, imidazolinium cations, thiazolium cations, triazolium cations, pyrrolidinium cations and imidazolidinium cations.

Particularly preferred are imidazolium cations, in particular imidazolium cations corresponding to the cation in formula I.

Very particularly preferred corrosion inhibitors are therefore compounds of the formula I in which the anion is the anion of one of the above acids, preferably a carboxylate, in particular a C 8 to C 26 carboxylate (see above).

Insofar as the corrosion inhibitor itself is an organic liquid, the corrosion inhibitor may be identical to the ionic liquid of which the composition is preferably greater than 40% by weight. In this case, the composition may contain only a single ionic liquid in an amount of more than 40% by weight, in particular more than 60% by weight and particularly preferably more than 80% by weight.

Preferably, however, the corrosion inhibitor (s) and the ionic liquid (s) which are preferably more than 40% by weight in the composition are different compounds, even if the corrosion inhibitor itself is an ionic liquid.

In particular, according to the invention imidazolium salts of the formula I with carboxylates, in particular C 8 to C 26 carboxylates (see above) are used as anion in other imidazolium salts of the formula I with any other anion.

The corrosion inhibitors (acids or their salts, that is including cation) are preferably used in the composition in an amount of 0.05 to 10 wt .-%, particularly preferably 0.05 to 0.5 wt .-%. The weight is based on the total composition.

The corrosion inhibitors used according to the invention have as acids and in particular as salts a good compatibility with ionic liquids and remain even under demanding conditions in the later use of the ionic liquids in the composition and thus ensure a long-lasting corrosion protection.

By the use according to the invention, the corrosion of metallic parts of the system is greatly reduced or even completely suppressed. Corrosion phenomena, such as a removal of the metal parts or pitting occur to a much reduced extent.

The compositions of the invention are therefore suitable for. As a lubricant, hydraulic fluid or other work equipment and for other applications in which it comes in contact with ionic liquids with parts of metal or can come.

Examples

Used substances

Ionic liquids:

The cation of ionic liquids was in all cases
Ethyl-methyl-imidazolium (in formula I: R 1 = methyl, R 3 = ethyl), in short EMIM
EMIM MeSO ₃
EMIM methylsulfonate
EMIM TFSI
TFSI is the anion: N (-SO ₂ CF ₃ ) ₂ ^-
EMIM EtSO ₄
EMIM ethyl sulfate

Corrosion inhibitors:

• EMIM tall oil carboxylate

The anion "tall oil carboxylate" is a mixture of the carboxylates of oleic acid, linoleic acid and linolenic acid.
IRGAMET ^®
a benzotriazole from Ciba, a commercially available corrosion inhibitor
IRGACOR ^® NPA
Iso-nonyl-phenoxyacetic acid from Ciba, a commercially available corrosion inhibitor
Sarkosyl O
N-oleyl-sarcosine (oil-soluble) from Ciba, a market-known corrosion inhibitor
Korantin PP
2- (prop-2-ynyloxy) ethanol, (water-soluble), a commercially available corrosion inhibitor

Carrying out the test

The corrosion inhibitors were added to the ionic liquids so that their content in the composition was 0.5% by weight. Thereafter, one drop each of the obtained composition was placed on a steel plate (plain carbon steel, steel key 1.0036), and the steel plate was heated at 90 ° C for 24 hours to maintain a drier air flow over the steel plate. After 24 hours, the steel plate was cleaned and the damage to the steel plate was evaluated by corrosion.

The corrosion was assessed visually with the gradations: corrosion, minor corrosion, no corrosion.

Results are listed in the table below. EMIM MeSO ₃ EMIM TFSI EMIM EtSO ₄ without corrosion no corrosion corrosion EMIM tall oil carboxylate reduced corrosion no corrosion reduced corrosion benzotriazole reduced corrosion no corrosion no corrosion IRGACOR NPA (oil-soluble) corrosion no corrosion corrosion Sarkosyl O (oil-soluble) corrosion no corrosion corrosion Korantin PP (water-soluble) corrosion no corrosion no corrosion

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2008/043837 [0024]
• WO 2005/113702 [0026]
• WO 03/029329 [0030]
• WO 2007/076979 [0030]
• WO 2006/000197 [0030]
• WO 2007/128268 [0030]

Cited non-patent literature

• X. Liu, F. Zhou, Y. Lang and W. Liu in Tribology Letters (2006), 23 (3), 191-196 [0007]

Claims (14)

Use of acids having an aliphatic hydrocarbon group of at least 8 C atoms or salts thereof as corrosion inhibitors in compositions containing at least one ionic liquid. Use according to claim, characterized in that the compositions are liquid. Use according to claim 1 or 2, characterized in that the compositions consist of more than 40% by weight of ionic liquids. Use according to any one of claims 1 to 3, characterized in that the ionic liquids are those having a cation selected from quaternary ammonium cations or cations comprising a heterocyclic ring system having one or two nitrogen atoms as part of the ring system contain. Use according to any one of claims 1 to 4, characterized in that the ionic liquids are imidazolium salts of formula 1 below

in which R 1 and R 3 are an organic radical having 1 to 20 C atoms, R 2, R 4 and R 5 are an H atom or an organic radical having 1 to 20 C atoms, X is an anion and n is 1 , 2 or 3 stands. Use according to one of claims 1 to 5, characterized in that the corrosion inhibitors are acids selected from carboxylic acids, esters of sulfuric acid, esters of phosphoric acid, salts of these acids or mixtures of these compounds. Use according to any one of claims 1 to 6, characterized in that the corrosion inhibitors are carboxylic acids or their salts (carboxylates) having a total of 8 to 26 carbon atoms. Use according to any one of Claims 1 to 7, characterized in that the corrosion inhibitors are tall oil fatty acids, that is oleic acid, linoleic acid or linolenic acid, their mixtures or the corresponding carboxylates of these acids. Use according to any one of claims 1 to 8, characterized in that the corrosion inhibitors are salts selected from carboxylates, salts of sulfuric acid esters or salts of phosphoric acid esters. Use according to one of claims 1 to 9, characterized in that the corrosion inhibitors are salts with organic cations. Use according to claim 10, characterized in that the organic cations are imidazolium cations. Use according to any one of Claims 1 to 11, characterized in that the corrosion inhibitors are present in the composition in an amount of from 0.05 to 10% by weight. Compositions containing salts or acids with an aliphatic hydrocarbon group of at least 8 carbon atoms as corrosion inhibitors and at least one ionic liquid Compositions which consist of more than 40 wt .-% of ionic liquids and at least one carboxylic acid or carboxylate having an aliphatic hydrocarbon group of 8 to 26 carbon atoms and having a carboxylic acid or a carboxylate group as a corrosion inhibitor.