EP2379687B1 - Water-based hydraulic fluids comprising dithio-di(aryl carbolic acids) - Google Patents

Description

The present invention relates to water-based hydraulic fluids containing dithiodi (arylcarboxylic acids) and having improved performance properties, and to the use of dithiodi (arylcarboxylic acids) as a corrosion inhibiting or lubricity additive in hydraulic fluids.

Water-based hydraulic fluids are used in a wide variety of applications, particularly where hydraulic fluid containing mineral oil emanating from the hydraulic system is a source of fire hazards or environmental hazards. Typical fields of application are steel mills, forges, coal mining and oil production facilities as well as wind farms.

Due to the reduced lubrication and increased risk of corrosion when compared to mineral oil-containing fluids, carefully matched additive packages are also used. A water-based hydraulic fluid typically includes the following components (described, for example, in U.S. Patent Nos. 4,346,488, 4,846,074, 5,429,846, 5,348,859, and 5,436,637) DE-A-2 534 808 respectively. T. Mang, W. Dressel: "Lubricants and Lubrication", Wiley-VCH, Weinheim, 2001, Chapter 11.4.6 ): (1) water 35 - 70% (2) Thickener or freezing point depressants (eg glycols) 25 - 50% (3) lubricant 0 - 20% (4) Corrosion inhibitors 0 - 10% (5) PH adjusting agent (eg alkanolamines) 0 - 10% (6) defoamers 0 - 2% (7) antioxidants 0 - 2% (8th) dye 0 - 0.1%

The pH is typically alkaline, usually pH> 9. Increasing the pH contributes to corrosion protection. decisive

Significance comes after the above composition to the anti-corrosion and lubricants.

EP-A-0 059 461 discloses as a lubricant polyalkylene glycols, which also serve as corrosion inhibitors, and the use of dithiophosphonates as a lubricant.

DE-A-2 534 808 describes alkoxylated polyamides of dicarboxylic acids and oligoamines which have improved lubricating properties and their use in water-based hydraulic fluids.

US 4434066 discloses hydroxy- or nitro-substituted aromatic carboxylic acids as lubricants in aqueous hydraulic fluids.

US 4138346 discloses phosphoric acid mono- and diesters and sulfur compounds such as mercaptobenzothiazoles, dithiobis (thiazoles) and alkyl disulfides as lubricants in aqueous hydraulic fluids.

WO-9634076 discloses as corrosion inhibitors in aqueous hydraulic fluids aliphatic carboxylic acids or their alkali or ammonium salts.

EP-A-0 059 461 discloses carboxylic acid diethanolamides, amines and substituted imidazolines, fatty acid ethoxylates as corrosion inhibitors in aqueous hydraulic fluids.

US 4452710 discloses as corrosion inhibitors in aqueous hydraulic fluids carboxylic acid amides with an additional free carboxylic acid function.

In addition to the stated requirements of a good lubricating and anti-corrosive effect are used in aqueous hydraulic fluids used today.

By the addition of salts during use of the liquid or by the economic reasons necessary use of hard water or even seawater to formulate the liquid hard water and electrolyte compatibility of the additives is required. Many of the currently known additives do not fulfill one or more of these conditions. Thus, many carboxylic acids and especially phosphoric acid esters are not stable to water hardness.
Furthermore, it is often omitted for economic and environmental reasons defoamers, which limits the selection of non-foaming additives. Ethoxylates and other alkoxylates, aliphatic carboxylic acids, in particular fatty acids, and aliphatic carboxylic acid alkanolamides are known for their strong foaming action on account of their surfactant structure.

Last but not least, additives must have good ecotoxicological properties, especially if the hydraulic fluids are used in ecologically sensitive areas such as the North Sea or the Arctic Ocean. For example, any hydraulic fluid additive used in North Sea oil production must meet OSPAR criteria that require good biodegradation and low toxicity. Many additives do not meet these criteria. Thus, imidazolines and mercaptobenzothiazoles are not approved due to their toxicity to marine organisms, so that often additives with poorer performance properties are used. Also in terms of ecological safety and also for economic reasons, the lowest possible use concentration of the additives is desirable. This is often complicated because additives that achieve a certain effect, eg. B. lubrication, often exert a negative influence on other properties, eg. B. deteriorate the corrosion protection. Thus, it is known that ethoxylates, especially if they are highly ethoxylated, indeed cause good lubrication, but are detrimental to the corrosion protection (see T. Mang, W. Dressel: "Lubricants and Lubrication", Wiley-VCH, Weinheim, 2001, Chapter 14.3 ). A significant improvement, therefore, are components that are multifunctional or have synergistic effects with other additives.

The object of the present invention was thus to find improved, low-foam, hard water-stable corrosion inhibitors and lubricant additives for water-based hydraulic fluids with good ecotoxicological properties, which require only a low use concentration.

In the literature ( Lubrication Engineering 1977, Vol. 33, page 291 .) It is described that alkali metal salts of dithiodibenzoic acid in aqueous metal cutting fluids have a weak lubricating effect compared to aliphatic sulfur-containing acids. It has now been found that dithiodi (arylcarboxylic acids) of the formula 1 have very good corrosion protection properties, especially at high pH values. It has furthermore been found that the dithiodi (arylcarboxylic acids) also have good lubricating properties sufficient for use in hydraulic fluids. In addition, they do not foam, are stable to hard water and electrolytes and have a low toxicity to aquatic organisms.

A further, particularly positive property has been found that, in combination with water-soluble corrosion protection agents, a further improved corrosion protection can be achieved compared to the sole use of these water-soluble corrosion protection agents. Due to the synergistic effect of dithiodi (arylcarboxylic acids) with common water-soluble corrosion inhibitors, the use concentration of the additive package in the hydraulic fluid can be reduced. The dithiodi (arylcarboxylic acids) are compatible with the common additives disclosed in the above-mentioned prior art. Through the use of synergistic mixtures of corrosion inhibitors and dithiodi (arylcarboxylic acids) hydraulic fluids can be produced for the known fields of application, but especially for offshore applications in ecologically sensitive areas such as the North Sea, which are ecologically and economically superior to the previously known and approved systems,

1. a) Wasser,
2. b) mindestens ein Glykol, ein Polyglykol oder beides, und
3. c) 0,1 bis 30 Gew.-% mindestens einer Verbindung der Formel 1,
   
   worin

   M

   Wasserstoff, Alkalimetall, Erdalkalimetall oder Ammonium,

   Ar¹ und Ar²

   unabhängig voneinander ein- oder mehrkernige aromatische Gruppen, die Substituenten tragen können, oder Heteroatome enthalten können

bedeuten.The invention thus relates to water-based hydraulic fluids containing

1. a) water,
2. b) at least one glycol, a polyglycol or both, and
3. c) 0.1 to 30% by weight of at least one compound of the formula 1,
   
   wherein

   M

   Hydrogen, alkali metal, alkaline earth metal or ammonium,

   Ar ¹ and Ar ²

   independently of one another mononuclear or polynuclear aromatic groups which may carry substituents, or may contain heteroatoms

mean.

Another object of the invention is the use of the compounds of formula (1) in amounts of 0.1 to 30 wt .-% as corrosion inhibitors or lubricity improvers in water-based hydraulic fluids.

Another object of the invention is a method for improving the anticorrosive and lubricating properties of water-based hydraulic fluids by adding 0.1 to 30 wt .-% of a compound of formula (1) to a hydraulic fluid.

In the case of the free acid, the substituents M are hydrogen, in the case of salts, alkali metal ions, alkaline earth metal ions or ammonium ions. In the case of the ammonium ions, these are preferably compounds formed by protonation from the amines described below as neutralizing agents.

The aryl radicals Ar ¹ and Ar ² may be the same or different. However, due to manufacturing reasons, compounds in which both aromatics are the same are preferred. Preferably, Ar ¹ and Ar ² are mononuclear or binuclear aromatic groups, especially mononuclear aromatic groups. Ar ¹ and Ar ² are preferably mononuclear benzoic acid derivatives of the formulas 2a-2c. Ar ¹ and Ar ² may contain heteroatoms.

In the following formulas, the two free valences denote the binding sites to the sulfide bridge and to the COOM group.

The substituents R ¹ -R ⁴ in the radicals Ar ¹ and Ar ² are preferably independently hydrogen, linear, branched and / or cyclic C ₁ -C ₂₀ alkyl - and / or C ₂ - to C ₂₀ -alkenyl radicals, halogen atoms, Nitro groups, amino groups, alkoxy groups, hydroxy or hydroxy-C ₁ -C ₂₀ -alkyl groups. The alkyl or alkenyl radicals are preferably short-chain radicals having 1 to 6 carbon atoms which do not deteriorate the solubility in water too much, eg. For example, methyl, ethyl, propyl, isopropyl, butyl, iso-butyl and tert-butyl radicals. According to the invention preferably further compounds which carry only one further substituent on the aromatic ring, ie in which three of R ¹ -R ⁴ are hydrogen. Most preferably, then, the remainder, which is not hydrogen, is in the meta or para position to the sulfide bridge. In a preferred embodiment, Ar ¹ and Ar ^{2 have} the substitution pattern of (2a) and (2c), particularly preferred is the substitution pattern of formula (2a).

worin die freie Valenz die Stellung der Sulfidbrücke angibt, und X für eine C₁- bis C₄-Alkylgruppe, eine Nitrogruppe oder ein Halogenatom steht. In dieser Ausführungsform entspricht die Verbindung der Formel (1) der Formel (4)

In a particularly preferred embodiment of the invention, each of the radicals Ar ¹ and Ar ^{2 is} a mononuclear aromatic radical of the formula (3)

wherein the free valence indicates the position of the sulfide bridge, and X represents a C ₁ to C ₄ alkyl group, a nitro group or a halogen atom. In this embodiment, the compound of the formula (1) corresponds to the formula (4)

worin X die oben angegebene Bedeutung hat.Furthermore, it is preferred that the compound of the formula (1) corresponds to the formula (5)

wherein X has the meaning given above.

X is particularly preferably in the para position to the sulfide bridge.

More preferably, X is a methyl or ethyl group.

In a further particularly preferred embodiment, the formula (1) is dithiodibenzoic acid, ie R ¹ , R ² , R ³ and R ⁴ are H.

The preparation of the compounds of formula (1) is known in the art and exemplified in EP-A-0 085 181 described.

Another object of the invention are water-based hydraulic fluids containing in combination with dithiodi (arylcarboxylic acids) another corrosion inhibitor.

1. a) Toluol- oder Benzolsulfonamidocapronsäuren (Formel (6))
   
   mit R⁵, R⁶ = H oder CH₃
2. b) Isononanoylamidocapronsäure (Formel (7))
   
3. c) Triazin-Trisaminohexansäure (Formel (8))
   

In a preferred embodiment, the hydraulic fluids contain at least one further corrosion inhibitor in addition to the dithiodi (arylcarboxylic acids). Suitable corrosion inhibitors are benzenesulfonic acid amidocaproic acid, toluenesulfonic acid amidocaproic acid, benzenesulfonic acid (N-methyl) amidocaproic acid, toluenesulfonic acid (N-methyl) amidocaproic acid (all formula 6), alkanoylamidocarboxylic acids, especially isononanoylamidocaproic acid (formula (7)) and triazine-2,4,6-tris (aminohexanoic acid ) (Formula (8)), or the alkali, alkaline earth and amine salts of the compounds of formulas (6) - (8).

1. a) Toluene or benzenesulfonamidocaproic acids (formula (6))
   
   with R ⁵ , R ⁶ = H or CH ₃
2. b) Isononanoylamidocaproic acid (Formula (7))
   
3. c) Triazine trisaminohexanoic acid (Formula (8))
   

Other known and suitable corrosion inhibitors are linear or branched C ₆ - to C ₈ -carboxylic acids such. Example, octanoic acid, 2-ethylhexanoic acid, n-nonanoic acid, n-decanoic acid, n-isodecanoic acid, dicarboxylic acids such as succinic acid, adipic acid, maleic acid, citric acid, and long-chain dicarboxylic acids such as decanedioic, undecanedioic or dodecanedioic acid, the chains may be branched or cyclic, and polycarboxylic acids. Also suitable corrosion inhibitors are alkanesulfonic acid amides, alkanesulfonamidocarboxylic acids and Phtalsäurehalbamide. Furthermore, the salts of the compounds listed above can also be used.

If the salts of one of the abovementioned corrosion inhibitors are used, these are preferably salts which are formed by reaction of the free acids with a neutralizing agent which is contained in the hydraulic fluid.

The hydraulic fluids preferably contain 1-15%, especially 1-10% of the dithiodi (arylcarboxylic acid) of the formula (1).

If further corrosion inhibitors are used, the total amount of dithiodi (arylcarboxylic acid) and further corrosion inhibitor is generally 0.1-30%, preferably 1-10%, especially 1-5% corrosion inhibitor. The use concentration of dithiodi (arylcarboxylic acids) is then between 0.05 to 20%, preferably 0.5 to 5%, especially 0.5 to 3%.

If the salts of the anticorrosive agents are used, the concentrations stated as weight percentages of the used Corrosion inhibitor due to the higher molecular weight of the salts compared to the free acids correspondingly higher.

wobei R⁷ = Wasserstoff, Methyl, Ethyl ist.According to the invention, the hydraulic fluid may contain a lubricant for reducing friction and abrasion. Suitable lubricants here are amine, alkali metal or alkaline earth metal salts of alkyl or aryl phosphoric acid esters and / or amine, alkali metal or alkaline earth metal salts of the phosphoric acid esters of alkoxylated alcohols. It is also possible to use polyalkylene glycols. These can be obtained by anionic or metal-catalyzed polymerization of alkylene oxides of the formula (9) with mono-, di-, tri-, tetra- and polyfunctional alcohols or amines or mixtures thereof

wherein R ⁷ = hydrogen, methyl, ethyl.

If several alkylene oxides are used, the polymerization can be carried out sequentially (blockwise arrangement of the monomers) or with a mixture of the oxides (random arrangement of the monomers). Suitable starting alcohols for these polyalkylene glycols are, for. As ethylene glycol, propylene glycol, trimethylolpropane, glycerol, pentaerythritol, sorbitol and other polyhydric alcohols. Suitable amines are, for. As the compounds mentioned below as neutralizing agents, if they contain acidic N-H bonds. The molecular weights of the polyalkylene glycols thus obtained may vary from 500 g / mol to 50,000 g / mol, usually the molecular weights are 2,000 to 10,000 g / mol.

Other suitable lubricants are sulfur compounds such as mercaptobenzothiazoles, dithiobis (thiazoles) and alkyl disulfides, thiophosphonates or inorganic compounds such as phosphoric acid or metal sulfides. In the preferred embodiment of the invention, the hydraulic fluid contains no lubricant, since the lubricity of the corrosion inhibitors, especially the dithiodi (arylcarboxylic acids) already sufficient.

The hydraulic fluids of the invention are adjusted with a neutralizing agent to a pH of 8-12, particularly preferably 9-10. Suitable neutralizing agents are amines of the formula (10)

NR ⁸ R ⁹ R ¹⁰ (10)

wherein
R ⁸ , R ⁹ and R ¹⁰ independently of one another represent hydrogen or a hydrocarbon radical having 1 to 100 carbon atoms.

In a first preferred embodiment, R ⁸ and / or R ⁹ and / or R ¹⁰ independently of one another represent an aliphatic radical. This preferably has 1 to 24, particularly preferably 2 to 18 and especially 3 to 6 C atoms. The aliphatic radical may be linear, branched or cyclic. It can still be saturated or unsaturated. Preferably, the aliphatic radical is saturated. The aliphatic radical may carry substituents such as, for example, hydroxyl, C ₁ -C ₅ -alkoxy, cyano, nitrile, nitro and / or C ₅ -C ₂₀ -aryl groups, for example phenyl radicals. The C ₅ -C ₂₀ -aryl radicals may in turn optionally be substituted by halogen atoms, halogenated alkyl radicals, C ₁ -C ₂₀ -alkyl, C ₂ -C ₂₀ -alkenyl, hydroxyl, C ₁ -C ₅ -alkoxy - such as, for example, methoxy- , Amide, cyano, nitrile, and / or nitro groups. In a particularly preferred embodiment, R ⁸ and / or R ⁹ and / or R ¹⁰ independently of one another represent hydrogen, a C ₁ -C ₆ -alkyl, C ₂ -C ₆ -alkenyl or C ₃ -C ₆ -cycloalkyl radical and especially for an alkyl radical having 1, 2, or 3 C atoms. These radicals can carry up to three substituents. Particularly preferred aliphatic radicals R ⁸ and / or R ⁹ and / or R ¹⁰ are hydrogen, methyl, ethyl, hydroxyethyl, n-propyl, isopropyl, hydroxypropyl, n-butyl, isobutyl and tert-butyl, hydroxybutyl, n-hexyl, cyclohexyl, n-octyl, n-decyl, n-dodecyl, tridecyl, isotridecyl, tetradecyl, hexadecyl, octadecyl and methylphenyl.

In another preferred embodiment, R ⁸ and R ⁹ together with the nitrogen atom to which they are attached form a ring. This ring has preferably 4 or more such as 4, 5, 6 or more ring members. Preferred further ring members are carbon, nitrogen, oxygen and sulfur atoms. The rings in turn may carry substituents such as alkyl radicals. Suitable ring structures are, for example, morpholinyl, pyrrolidinyl, piperidinyl, imidazolyl and azepanyl radicals. In a preferred embodiment, then R ^{10 is} H or an alkyl radical having 1 to 12 carbon atoms.

In a further preferred embodiment, R ⁸ , R ⁹ and / or R ¹⁰ independently of one another represent an optionally substituted C ₆ -C ₁₂ -aryl group or an optionally substituted heteroaromatic group having 5 to 12 ring members.

In a further preferred embodiment, R ⁸ , R ⁹ and / or R ¹⁰ independently of one another represent an alkyl radical interrupted by heteroatoms. Particularly preferred heteroatoms are oxygen and nitrogen.

R¹¹

für eine Alkylengruppe mit 2 bis 6 C-Atomen und bevorzugt mit 2 bis 4 C-Atomen wie beispielsweise Ethylen, Propylen, Butylen oder Mischungen daraus,

R¹²

für Wasserstoff, einen Kohlenwasserstoffrest mit 1 bis 24 C-Atomen oder eine Gruppe der Formel -NR¹³R¹⁴,

n

für eine Zahl zwischen 2 und 50, bevorzugt zwischen 3 und 25 und insbesondere zwischen 4 und 10 und

R¹³, R¹⁴

unabhängig voneinander für Wasserstoff, einen aliphatischen Rest mit 1 bis 24 C-Atomen und bevorzugt 2 bis 18 C-Atomen, eine Arylgruppe - oder Heteroarylgruppe mit 5 bis 12 Ringgliedern, eine Poly(oxyalkylen)gruppe mit 1 bis 50 Poly(oxyalkylen)einheiten, wobei sich die Polyoxyalkyleneinheiten von Alkylenoxideinheiten mit 2 bis 6 C-Atomen ableiten, oder R¹³ und R¹⁴ gemeinsam mit dem Stickstoffatom, an das sie gebunden sind, einen Ring mit 4, 5, 6 oder mehr Ringgliedern bilden, stehen.

Thus, R ⁸ , R ⁹ and / or R ¹⁰ independently of one another are preferably radicals of the formula (11)

- (R ¹¹ -O) _n -R ¹² (11)

wherein

R ¹¹

for an alkylene group having 2 to 6 C atoms and preferably having 2 to 4 C atoms, for example ethylene, propylene, butylene or mixtures thereof,

R ¹²

is hydrogen, a hydrocarbon radical having 1 to 24 carbon atoms or a group of the formula -NR ¹³ R ¹⁴ ,

n

for a number between 2 and 50, preferably between 3 and 25 and in particular between 4 and 10 and

R ¹³ , R ¹⁴

independently of one another are hydrogen, an aliphatic radical having 1 to 24 C atoms and preferably 2 to 18 C atoms, an aryl group or heteroaryl group having 5 to 12 ring members, one Poly (oxyalkylene) group having 1 to 50 poly (oxyalkylene) units, wherein the polyoxyalkylene derived from alkylene oxide having 2 to 6 carbon atoms, or R ¹³ and R ¹⁴ together with the nitrogen atom to which they are attached, a ring with 4, 5, 6 or more ring members form, stand.

R¹⁵

für eine Alkylengruppe mit 2 bis 6 C-Atomen und bevorzugt mit 2 bis 4 C-Atomen wie beispielsweise Ethylen, Propylen oder Mischungen daraus steht,

jedes R¹⁶

unabhängig voneinander für Wasserstoff, einen Alkyl- oder Hydroxyalkylrest mit bis zu 24 C-Atomen wie beispielsweise 2 bis 20 C-Atomen, einen Polyoxyalkylenrest -(R¹¹-O)_p-R¹², oder einen Polyiminoalkylenrest -[R¹⁵-N(R¹⁶)]_q-(R¹⁶) stehen, wobei R¹¹, R¹², R¹⁵ und R¹⁶ die oben gegebenen Bedeutungen haben und q und p unabhängig voneinander für 1 bis 50 stehen und

m

für eine Zahl von 1 bis 20 und bevorzugt 2 bis 10 wie beispielsweise drei, vier, fünf oder sechs steht.

Furthermore, R ⁸ , R ⁹ and / or R ¹⁰ independently of one another are preferably radicals of the formula (12)

- [R ¹⁵ -N (R ¹⁶ )] _m - (R ¹⁶ ) (12)

wherein

R ¹⁵

represents an alkylene group having 2 to 6 C atoms and preferably having 2 to 4 C atoms, such as, for example, ethylene, propylene or mixtures thereof,

every R ¹⁶

independently of one another represent hydrogen, an alkyl or hydroxyalkyl radical having up to 24 C atoms, such as, for example, 2 to 20 C atoms, a polyoxyalkylene radical - (R ¹¹ -O) _p -R ¹² , or a polyiminoalkylene radical - [R ¹⁵ -N ( R ¹⁶ )] _q - (R ¹⁶ ), where R ¹¹ , R ¹² , R ¹⁵ and R ^{16 have} the meanings given above and q and p independently of one another are from 1 to 50 and

m

is a number from 1 to 20, and preferably from 2 to 10, such as three, four, five or six.

The radicals of the formula (12) preferably contain 1 to 50, in particular 2 to 20, nitrogen atoms.

Particularly preferred neutralizing agents are water-soluble alkylamines such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, propylamine and Langerkettige mono-, di- and trialkylamines, provided that they are at least 1 wt .-%, preferably 1 - 5 wt .-% water-soluble , The alkyl chains can be branched here. Also suitable are oligoamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, their higher homologs and mixtures of these. Further suitable amines in this series are the alkylated, especially methylated, representatives of these oligoamines, such as N, N-dimethyldiethyleneamine, N, N-dimethylpropylamine and longer-chain and / or higher alkylated amines of the same construction principle. Particularly suitable according to the invention are alkanolamines such as monoethanolamine, diethanolamine, triethanolamine, diglycolamine, triglycolamine and higher homologs, methyldiethanolamine, ethyldiethanolamine, propyldiethanolamine, butyldiethanolamine and longer-chain alkyldiethanolamines, where the alkyl radical may be cyclic and / or branched. Further suitable alkanolamines are dialkylethanolamines such as dimethylethanolamine, diethylethanolamine, dipropylethanolamine, dibutylethanolamine and longer-chain dialkylethanolamines, where the alkyl radical may also be branched or cyclic. Also within the meaning of the invention, aminopropanol, aminobutanol, aminopentanol and higher homologs, as well as the corresponding mono- and dimethylpropanolamines and longer-chain mono- and dialkylamino alcohols can be used. Last but not least, special amines such as 2-amino-2-methylpropanol (AMP), 2-aminopropanediol, 2-amino-2-ethylpropanediol, 2-aminobutanediol and other 2-aminoalkanols, aminoalkylamine alcohols, tris (hydroxylmethyl) aminomethane are suitable, as well as end-capped Representatives such as methylglycolamine, methyldiglycolamine and higher homologs, di (methylglycol) amine, di (methyldiglycol) amine and their higher homologs and the corresponding triamines and polyalkylene glycol amines (eg Jeffamine ^® ). Usually and in the context of the invention, mixtures of the abovementioned amines are used to adjust desired pH values.

Other suitable neutralizing agents are the oxides and hydroxides of the alkali and / or alkaline earth metals, such as. For example, lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide and calcium oxide.

The neutralizing agents mentioned are used in amounts that are needed to set a desired pH of the hydraulic fluid. This desired pH is 7 - 11, preferably 8 - 10, especially preferably 9-10. The amounts of neutralizing agent required for this purpose are generally between 0.1-10%.

The hydraulic fluids according to the invention may contain, in addition to water, a freezing point depressant or viscosity regulator. Suitable freezing point depressants are polyols, preferably comprising 2 to 10 OH groups. Examples of these are ethylene glycol, diethylene glycol, triethylene glycol and higher polyethylene glycols, propylene glycol, dipropylene glycol and higher polypropylene glycols, the corresponding methylglycols, ethyl, butyl and other alkylglycols and also alkylpropylene glycols. Likewise, glycerol, diglycerol, triglycerol and higher homologues, 1,3-propanediol and its oligo- and polymers can be used. It is also possible to use mixtures of the compounds mentioned. Their concentration depends on the required freezing point, which can vary greatly depending on the application and field of application. 1-50% freezing point depressants are used, preferably 20-50%, particularly preferably 30-40%.

wobei R⁷ = Wasserstoff, Methyl, Ethyl ist.Suitable viscosity regulators are polyacrylates, polymethacrylates and polyalkylene glycols, in particular high molecular weight polyalkylene glycols. These can be obtained by anionic or metal-catalyzed polymerization of alkylene oxides of the formula (9) or mixtures thereof with mono-, di-, tri-, tetra- and polyfunctional alcohols or amines

wherein R ⁷ = hydrogen, methyl, ethyl.

If several alkylene oxides can be used, the polymerization can be carried out sequentially (blockwise arrangement of the monomers) or with a mixture of the oxides (random arrangement of the monomers). Suitable starting alcohols for these polyalkylene glycols are, for. As ethylene glycol, propylene glycol, trimethylolpropane, glycerol, pentaerythritol, sorbitol and other polyhydric alcohols. suitable Amines are z. As the compounds mentioned below as neutralizing agents, if they contain acidic NH bonds. These polyalkylene glycols are usually selected not according to their molecular weight, but according to their viscosity at 40 ° C or 50 ° C, which may be usually from a few mPas up to 50,000 mPas and more and depends on the application. The use concentration of the viscosity regulators depends on the desired viscosity and may be 1-50%, preferably 20-50%, particularly preferably 30-40%.

According to the invention, the additives mentioned in the prior art defoamers, dyes and antioxidants can be used in the hydraulic fluid. In the preferred embodiment, but can be omitted for the reasons mentioned.

The preparation of the hydraulic fluids of this invention can be accomplished by mixing at room temperature or elevated temperatures directly from the components, or by diluting a previously prepared additive package with water, or by diluting a previously prepared additive package with a mixture of water and the freezing point depressant. If the hydraulic fluid is prepared directly from the components, it is advisable to introduce the water and optionally the freezing point and the subsequent addition of further ingredients, preferably first the neutralizing agent, then the compound of formula (1), then - if necessary - the other lubricant and the additional corrosion inhibitors are added. Other additives such as defoamers, dyes, antioxidants and viscosity regulators are added at the end. If the additive package is prepared separately so water and the freezing point, if it is part of the additive package, presented, then the neutralizing agent is added and then the other components in the above order. At high viscosities, especially when the freezing point depressant is not part of the additive package, a higher temperature than room temperature may be necessary during mixing, this temperature usually does not exceed 80 - 100 ° C. For particularly high viscosities, the additive package can be diluted with water.

All percentages in this application are percentages by weight based on the total weight of the hydraulic fluid. Exceptions are marked.

Examples

Dithiodiarylcarboxylic acids of the formula (2a) are designated below with o - (ortho), of the formula (2b) with m - (meta) and of the formula (2c) with p - (para). The use concentrations were chosen so that the hydraulic fluids achieve the desired corrosion protection (no corrosion at 15% application concentration).

Example 1 (Prior Art) - Hydraulic fluid A consisting of:

water 43% Monoethylene glycol 40% Monoethanolamine 5% triethanolamine 3% Mixture of mono and dibutylphosphoric acid ester 7% Isononanoylamidocapronsäure 2%

Example 2 (Prior Art) - Hydraulic fluid B consisting of:

water 43% Monoethylene glycol 40% Monoethanolamine 2% triethanolamine 5% EO-PO block polymer M _w 600 (polyalkylene glycol) 5% Isononanoylamidocapronsäure 5%

Example 3 - Hydraulic fluid C consisting of:

water 46% Monoethylene glycol 40% triethanolamine 4% Monoethanolamine 3% o -Dithiodibenzoic acid 7%

Example 4 - Hydraulic fluid D consisting of:

water 44% Monoethylene glycol 40% triethanolamine 4% Monoethanolamine 4% m -dithiodibenzoic acid 9%

Example 5 - hydraulic fluid E consisting of:

water 42% Monoethylene glycol 40% triethanolamine 4% Monoethanolamine 5% p -dithiodibenzoic acid 8th %

Example 6 - Hydraulic fluid F consisting of:

water 46% Monoethylene glycol 40% triethanolamine 4% Monoethanolamine 3% o -Dithiodi (4-chloro-benzoic acid) 7%

Example 7 - Hydraulic fluid G consisting of:

water 46% Monoethylene glycol 40% triethanolamine 4% Monoethanolamine 3% o -Dithiodi (4-methylbenzoic acid) 7%

Example 8 - hydraulic fluid H consisting of:

water 46% Monoethylene glycol 40% triethanolamine 4% Monoethanolamine 3% o -Dithiodi (4-nitrobenzoic acid) 7%

Example 9 - Hydraulic fluid I consisting of:

water 45% Monoethylene glycol 40% triethanolamine 4% Monoethanolamine 3% o -Dithiodi (2,5-dimethylbenzoic acid) 8th %

Example 10 - Hydraulic fluid J consisting of:

water 45% Monoethylene glycol 40% triethanolamine 4% Monoethanolamine 3% 1,1 '-Dithiodi (naphthalene-2-carboxylic acid) 9%

Example 11 - Hydraulic fluid K consisting of:

water 46% Monoethylene glycol 40% triethanolamine 3% Monoethanolamine 3% 5,5 '-Dithiodi (quinoline-6-carboxylic acid) 9%

Example 12 - Hydraulic fluid L consisting of:

water 49% Monoethylene glycol 40% riethanolamin 5% Monoethanolamine 2% o -Dithiodibenzoic acid 2% Isononanoylamidocapronsäure 2% Table 1: Performance properties of fluids A-L The table demonstrates the improved efficacy and stability of the hydraulic fluids C to K according to the invention and in particular J (shows the synergistic effect with isononanoylamidocaproic acid). hydraulic fluid test criterion A B C D e F G H I J K L Appearance (20 ° C) clear liquid pH value (1% in water) 9.5 9.5 9.5 9.5 9.5 9.5 9.5 9.5 9.5 9.5 9.5 9.5 Hard water stability ¹⁾ cloudy, dregs clear clear clear clear clear clear clear clear clear clear clear Stability in seawater ²⁾ cloudy, dregs clear clear clear clear clear clear clear clear clear clear clear foam behavior Weak foam No foam Lubrication test (Reichert) ³⁾ Abrasion (mm ² ) 20.9 29.7 12.2 18.3 20.2 14.5 12.5 15.5 13.1 17.6 19.5 22.5 Noise Meter (m) 31 87 6 10 35 15 10 16 11 23 28 36 Corrosion protection (DIN 51360/2) ⁴⁾ 15% 15% 15% 15% 15% 15% 15% 15% 15% 15% 15% 15% Explanatory notes to Table 1:
¹⁾ 20% solution in water, 20 ° dH (corresponding to 350 ppm CaCO ₃ ), appearance after 24 h, 20 ° C
²⁾ 50% solution in seawater, appearance after 24 h at 20 ° C
³⁾ Reichert weight compensator to Reichert, weight 1.5 kg, circulation distance 100 m, circulation speed 1.6 m / s; Material steel rollers
⁴⁾ Limit concentration at which the filter paper still remains stainless

Examples 3 to 11 show the superior stability and low foaming of hydraulic fluids of the invention over the prior art. Examples 3-12 demonstrate the improved lubricity and anti-corrosion properties when using a dithiodi (arylcarboxylic acid) alone, as demonstrated by synergistic effect with another anticorrosive agent, a reduced use concentration of the active ingredient combination lubricant / corrosion inhibitor (4% compared to at least 7% in Examples 1 to 11) can be achieved without losing effectiveness. Due to the synergistic effect of dithiodi (arylcarboxylic acids) with common water-soluble corrosion inhibitors, the use concentration of the additive package in the hydraulic fluid can be reduced, as Example 12 compared to Examples 1 and 2 (known drug combinations) shows. Table 2: Ecotoxicological data Table 2 shows typical ecotoxicological data for corrosion and lubricant additives, as required by OSPAR for use in the North Sea. The requirements for OSPAR are fulfilled only by dithiodi (benzoic acid). example additive Biodegradation (OECD 306) Algae toxicity (EC ₅₀ ) Fish toxicity (LC ₅₀ ) OSPAR control - > 20% or> 60% > 10 mg / l > 10 mg / l comparison mercaptobenzothiazole <20% <1 mg / l <10 mg / l comparison N-aminoethyloleylimidazoline > 60% <1 mg / l <10 mg / l Additive from Example 3 Dithiodi (benzoic acid) (as salt) > 30% > 100 mg / l > 100 mg / l

Claims (15)

1. A hydraulic fluid comprising

   a) water,

   b) at least one glycol, a polyglycol or both, and

   c) from 0.1 to 30% by weight of at least one compound of the formula 1

   

   in which

   M is hydrogen, alkali metal, alkaline earth metal or ammonium,

   Ar¹ and Ar² are each independently mono- or polycyclic aromatic groups which may bear substituents or may contain heteroatoms.
2. The hydraulic fluid as claimed in claim 1, containing 35-70% by weight of water and 25-50% by weight of a glycol, of a polyglycol or both.
3. The hydraulic fluid as claimed in claim 1 and/or 2,
   in which Ar¹ and Ar² are each groups of the formulae 2a-2c

   

   in which R¹, R², R³, R⁴ are each independently H, CH₃, C₂-C₂₀-alkyl or -alkenyl, C₃- to C₂₀-cycloalkyl, halogen, NO₂, NO₃, CN, OX, NH₂, NHX or N(X)₂,
   where X = C₁-C₂₀-alkyl or C₃- to C₂₀-cycloalkyl.
4. The hydraulic fluid as claimed in one or more of claims 1 to 3,
   in which the Ar¹ and Ar² radicals each bear only one substituent which is not H apart from the carboxyl group and the sulfide bridge.
5. The hydraulic fluid as claimed in one or more of claims 1 to 4,
   in which each of the Ar¹ and Ar² radicals represents a monocyclic aromatic radical of the formula 3

   

   in which the free valence indicates the position of the sulfide bridge, and X is a C₁- to C₄-alkyl group, a nitro group or a halogen atom.
6. The hydraulic fluid as claimed in one or more of claims 1 to 5,
   in which X is in the para position to the sulfide bridge.
7. The hydraulic fluid as claimed in one or more of claims 1 to 6,
   in which X is a methyl or ethyl group.
8. The hydraulic fluid as claimed in one or more of claims 1 to 3,
   in which the formula 1 represents dithiodibenzoic acid.
9. The hydraulic fluid as claimed in one or more of claims 1 to 8, comprising at least one further anticorrosive selected from the group consisting of

   a) toluene- or benzenesulfonamidocaproic acids of the formula 6

   

   where R⁵, R⁶ = H or CH₃,

   b) isononanoylamidocaproic acid of the formula 7

   

   and

   c) triazinetrisaminohexanoic acid of the formula 8

   
10. The hydraulic fluid as claimed in one or more of claims 1 to 9, comprising at least one further anticorrosive selected from the group of the aliphatic and aromatic carboxylic acids, the aliphatic and aromatic dicarboxylic acids, the aliphatic and aromatic polycarboxylic acids, the phthalic monoamides, alkanesulfonamides and the alkanesulfonamidocarboxylic acids.
11. The hydraulic fluid as claimed in one or more of claims 1 to 10, comprising a lubricant for reducing friction and abrasion.
12. The hydraulic fluid as claimed in one or more of claims 1 to 11, comprising a neutralizing agent selected from the group of the amines, alkanolamines, alkali metal hydroxides and oxides, alkaline earth metal hydroxides and oxides.
13. The hydraulic fluid as claimed in one or more of claims 1 to 12, comprising a freezing point depressant selected from the group of the ethylene glycols, propylene glycols, alkyl glycols, alkylpropylene glycols.
14. The hydraulic fluid as claimed in one or more of claims 1 to 13, comprising a thickener selected from the group of the polyacrylates, polymethacrylates, polyethylene glycols, polypropylene glycols, polyalkylene glycols.
15. The use of from 0.1 to 30% by weight of a compound of the formula 1

    

    in which

    M is hydrogen, alkali metal, alkaline earth metal or ammonium,

    Ar¹ and Ar² are each independently mono- or polycyclic aromatic groups which may bear substituents or may contain heteroatoms

    as an anticorrosive or lubricity additive in hydraulic fluids.