EP0412271B1 - Hydraulic fluids - Google Patents

Description

The invention relates to flame-retardant hydraulic fluids that are environmentally compatible and have lubricating properties.

Hydraulic fluids based on mineral oils are particularly common. In the mining industry, however, flame-retardant hydraulic fluids are required for safety reasons. B. in Schrämm machines, tunnel boring machines, turbo couplings and hydraulic rams. Flame-retardant liquids are also preferred outside of mining wherever there are devastating fires when flammable media escape from the closed hydraulic system.

The current flame-retardant hydraulic fluids are, in particular, aqueous systems, either oil-in-water emulsions (HFA) or glycol-polyglycol-water mixtures (HFC). The main disadvantage of the o / w emulsions is that they are metastable systems, which can be particularly critical due to temperature fluctuations and electrolytes (DE-OS 35 08 946). If thickened systems are involved, such as the avoidance of leakage losses in the gap seals of pumps and valves or the build-up of lubricating films between rubbing solid surfaces, the polymers used are usually not or only insufficiently stable under shear.

HFC fluids based on mono-, oligo- or polyglycols have, in addition to extensive flame resistance, the advantage of physiological harmlessness and ecological acceptance (P. Lehringer, Petroleum and Coal-Natural Gas-Petrochemicals 41, 230 (1988)), which is particularly advantageous for Mobile use is where hydraulic fluid leaks often seep into the ground. The systems are also considered to be largely shear stable, but this is to be viewed critically in view of the fact that usually the polymers in particular make the greatest contribution to the overall viscosity of the liquid, because of their chemical structure they are most at risk of shear. Another disadvantage of the current HFC liquids is that the proportion of active substance must be very high, even at a somewhat elevated temperature still have a minimum viscosity. Water contents ≦ 50% are quite typical here (C. Rasp, Tribologie Schmierungstechn. 35, 185 (1988). In addition, the additive packages for producing more favorable effects in lubrication and wear protection are very complex here.

The task was therefore to develop flame-retardant, environmentally compatible hydraulic fluids which are sufficiently viscous at low active substance concentrations and have a favorable lubricating effect.

The problem was solved by aqueous hydraulic fluids containing an aqueous surfactant solution as a basis.

The invention therefore relates to the use of a mixture of
5-30% by weight alkyl polyglycoside
0-20% by weight of surfactant additives
0-10% by weight of non-surfactant additives and
Water ad 100% by weight,
as aqueous hydraulic fluids, characterized in that the alkyl polyglycoside corresponds to the formula RON _n , in which R for a linear or branched, saturated or unsaturated alkyl radical with 8 to 18 carbon atoms and Z _n for an oligoglycoside radical with an average of n = 1 to 3 hexose or pentose units or mixtures thereof and the active substance content is at most 40% by weight.

It has surprisingly been found that alkylpolyglycosides, even at lower concentrations, alone or in the presence of other surfactants, have a particularly high level of viscosity with a very good lubricating effect.

Alkyl polyglycosides

The alkyl polyglycosides used according to the invention correspond to the general formula (I)

RON _n , (I)


in which R is a linear or branched, saturated or unsaturated alkyl radical having 8 to 18 carbon atoms and Z _{n is} an oligoglycoside radical with an average of n = 1 to 3, hexose or pentose units or mixtures thereof.

The alkyl oligoglycosides used in accordance with the invention can be prepared entirely or partially on the basis of renewable raw materials by known processes. For example, dextrose is reacted with n-butanol to give butyl oligoglycoside mixtures in the presence of an acid catalyst, which are transglycosidated with long-chain alcohols in the presence of an acid catalyst to give the desired alkyl oliglycoside mixtures. The formula of the products can be varied within certain limits. The alkyl radical R 'is determined by the choice of the long-chain alcohol. Favorable for economic reasons are the industrially accessible tenside alcohols with 8 to 18 carbon atoms, e.g. B. oxo alcohols, Ziegleralkohole and native alcohols from the hydrogenation of fatty acids or fatty acid derivatives.

The oligoglycosyl radical Z _n is determined, on the one hand, by the selection of the carbohydrate and, on the other hand, by setting the average degree of oligomerization n. B. according to DE-OS 19 43 689. In principle, it is known that polysaccharides, oligosaccharides and monosaccharides, e.g. B. starch, maltodextrins, dextrose, galactose, mannose, xylose, etc. can be converted to alkyl oligoglycosides. The industrially available carbohydrates starch, maltodextrins and dextrose are particularly preferred. Since the economically interesting alkyl polyglycoside syntheses are not regio- and stereoselective, the alkyl polyglycosides are always mixtures of oligomers, which in turn represent a mixture of different isomeric forms. They exist side by side with α- and β-glycosidic bonds in pyranose and furanose form. The links between two saccharide residues are also different.

Due to the synthesis, the alkyl polyglycosides can also contain accompanying substances such as residual alcohols, monosaccharides, oligosaccharides and oligoalkyl polyglycosides.

Surfactant additives

• a) Alkylbenzol- oder Dialkylbenzolsulfonate der Formel (II)
  
          R(R₁)C₆H₃SO₃M   (II),
  
  in der R einen verzweigten oder unverzweigten Alkylrest mit 8 bis 20 C-Atomen, R₁ H oder einen verzweigten oder unverzweigten Alkylrest mit 1 bis 10 C-Atomen, wobei die Kohlenstoffatomsumme von R und R₁ mindestens 8, vorzugsweise 10 bis 18, beträgt, und M Na, K, Ammonium oder Alkylammonium bedeuten.
• b) Alkansulfonate und/oder Olefinsulfonate der Formel (III)
  
          R''SO₃M'   (III)
  
  sein, in der R'' ein gesättigter oder ungesättigter, verzweigter oder unverzweigter Alkylrest mit 8 bis 20 C-Atomen und M' Na, K, Ammonium oder Alkylammonium bedeuten.
• c) Petroleumsulfonate
• d) Fettalkohol- bzw. Alkylphenolderivate der folgenden Formel (IV)
  
          [R‴(C₆H₄)_xO(R''''O)_y]_z U_vM'',   (IV)
  
  in der R‴ ein gesättigter, verzweigter oder unverzweigter Alkylrest mit 6 bis 20, vorzugsweise 8 bis 16 Kohlenstoffatomen, x = 0 oder 1, R'''' C₂H₄ oder C₃H₆, y 0 bis 15, z 1 oder 2, U SO₃, CH₂COO, CHCOO, v 0 oder 1 und M'' H, Na, K, Ammonium oder Alkylammonium bedeuten.
• e) Weitere tensidische Zusätze sind Carbonsäuren mit längeren, verzweigten oder unverzweigten, gesättigten oder ungesättigten Kohlenwasserstoffketten sowie Phosphorsäurepartialester insbesondere von Alkoholen bzw. von Fettalkohol- bzw. Alkylphenoloxethylaten. Letztere lassen sich durch Umsetzung der betreffenden Alkohole bzw. Oxethylate mit Phosphorsäuren, Phosphoroxiden oder Phosphorhalogeniden herstellen.

The flame-retardant hydraulic fluids according to the invention can furthermore contain up to 20% by weight of surfactant additives which are selected from the following compounds or consist of mixtures of these compounds:

• a) alkylbenzene or dialkylbenzenesulfonates of the formula (II)
  
  R (R₁) C₆H₃SO₃M (II),
  
  in which R is a branched or unbranched alkyl radical having 8 to 20 C atoms, R₁ H or a branched or unbranched alkyl radical having 1 to 10 C atoms, the sum of carbon atoms of R and R₁ being at least 8, preferably 10 to 18, and M is Na, K, ammonium or alkylammonium.
• b) alkane sulfonates and / or olefin sulfonates of the formula (III)
  
  R''SO₃M '(III)
  
  be in which R "is a saturated or unsaturated, branched or unbranched alkyl radical having 8 to 20 carbon atoms and M 'Na, K, ammonium or alkylammonium.
• c) Petroleum sulfonates
• d) fatty alcohol or alkylphenol derivatives of the following formula (IV)
  
  [R ‴ (C₆H₄) _x O (R '''' O) _y ] _z U _v M '', (IV)
  
  in which R ‴ is a saturated, branched or unbranched alkyl radical having 6 to 20, preferably 8 to 16 carbon atoms, x = 0 or 1, R '''' C₂H₄ or C₃H₆, y 0 to 15, z 1 or 2, U SO₃, CH₂COO, CHCOO, v 0 or 1 and M "H, Na, K, ammonium or alkylammonium.
• e) Other surfactant additives are carboxylic acids with longer, branched or unbranched, saturated or unsaturated hydrocarbon chains and phosphoric acid partial esters, in particular of alcohols or of fatty alcohol or alkylphenol oxyethylates. The latter can be prepared by reacting the alcohols or oxyethylates in question with phosphoric acids, phosphorus oxides or phosphorus halides.

Finally, cationic surfactants such as quaternary ammonium compounds as additives to alkyl polyglycosides in aqueous hydraulic fluids also have beneficial effects, e.g. B. a strong improvement in lubricating properties.

Non-surfactant additives

Suitable non-surfactant additives in the hydraulic fluids according to the invention are amines or alkanolamines as pH regulators or corrosion inhibitors; Sodium molybdate, boric acid amine ester, benzotrialzole or toluene triazole also as corrosion inhibitors; Morpholine or N-methylmorpholine as vapor phase inhibitors; Silicone defoamers or other defoamers; Glycol and / or glycol ether or urea as a solubilizer and optionally water-soluble polymers for correcting the temperature profile of the viscosity and preservatives.

In addition to water as the solvent, the hydraulic fluid according to the invention is based on the alkylpolyglycosides, a toxicologically, unobjectionable surfactant class of excellent biodegradability (95 to 97% by weight coupled unit test, DOC). 3 to 30 wt .-%, preferably 5 to 25 wt .-%, alkyl polyglycoside are contained in the liquids according to the invention, the total active ingredient concentration at max. 40% by weight, preferably 35% by weight.

The pressure fluids according to the invention are usually clear in the temperature range between 5 and 80 ° C. or possibly slightly opalescent in the presence of silicone defoamers. They are usually weakly alkaline.

MARLON^(R) A

lineares C₁₀C₁₃-Alkylbenzolsulfonat-Na-Salz
(Hüls AG)

MARLON^(R) PS

C₁₃C₁₇-Paraffinsulfonat Na-Salz
(Hüls AG)

Polymekon^(R) 730

Silikonentschäumer
(Goldschmidt AG)

bedeuten.The following examples are intended to illustrate the liquids, where

MARLON ^(R) A

linear C₁₀C₁₃ alkylbenzenesulfonate Na salt
(Hüls AG)

MARLON ^(R) PS

C₁₃C₁₇ paraffin sulfonate sodium salt
(Hüls AG)

Polymekon ^(R) 730

Silicone defoamer
(Goldschmidt AG)

mean.

example 1

A 15 wt .-% solution of C₁₂C₁₃ alkyl polyglycoside (DP 1.7, determined via 1 H-NMR) in demineralized water was prepared. The viscosity behavior of the solution (Haake RV 20 rotational viscometer, M 5, 50 ° C, shear range 30-300 sec⁻¹) is Newtonian and is approx. 150 mPa · s. Multiple ultrasound (Telsonic USG 1000, 20 kHz), each lasting 10 minutes, did not change the viscosity and confirmed the assumed shear stability of the system. The clear point of the solution is 10 ° C. As the temperature rises (up to 80 ° C), the solution does not undergo any optical change. The wear behavior (lubrication effect) of the solution was investigated with the friction wear balance according to Reichert (weight loss of the test rollers after 100 m friction distance and 1,500 g load). The mean value from 3 test runs was 6.6 ± 0.5 mg at a specific surface pressure of 2,400 N / cm². No foam development was observed during wear measurement. Comparative wear tests with demineralized water on the one hand and Ecubasol Hydrotherm ^(R) 36 (glycol-based hydraulic fluid) on the other hand showed weight loss values of 66 and 6.9 mg under similar conditions. The comparison of the results demonstrates that a 15% by weight solution of the alkyl polyglycoside not only has a sufficient viscosity level but also has strong lubricating properties.

Example 2

A 15 wt .-% solution of N-C₁₂-C₁₈-N, N, N trimethylammonium chloride in demineralized water is low viscosity at 50 ° C (about 1 mPa · s), its wear-preventing effect - carried out analogously to Example 1 - is mediocre with 34.5 mg weight loss. However, if half of the quaternary ammonium compound is replaced by C₁₂C₁₃ alkyl polyglycoside (DP 1.7), a strong lubricating effect results with a weight loss of 10.9 ± 0.6 mg, whereas the approximate viscosity remains unchanged and the clear point of +2 ° C to +5 ° C.

Example 3

A 10 wt .-% solution of C₁₀-C₁₄ alkyl polyglycoside (D.P. about 1.3) in demineralized water shows Newtonian flow behavior and has a viscosity of 70 mPa · s at 50 ° C. The analysis of the wear behavior carried out analogously to Example 1 showed a weight loss of the test specimen of 15 mg.

Examples 4 to 13 (tables)

The examples in question demonstrate the effectiveness of the mixtures according to the invention in terms of viscosity level and wear protection. The sonication carried out in the solutions according to Examples 4 and 10 (2 times 10 minutes, each with subsequent viscosity measurement) shows a complete shear stability of the structures producing the increased viscosity. Examples 11 and 12 demonstrate the effectiveness of the mixtures according to the invention in water of different hardness (calcium hardness).

Claims (2)

1. The use of a mixture composed of
      5 - 30% by weight of alkyl polyglycoside
      0 - 20% by weight of surface-active additives
      0 - 10% by weight of non-surface-active additives
      and water to 100% by weight,
   as an aqueous hydraulic fluid, characterised in that the alkyl polyglycoside corresponds to the formula R-O-Z_n, in which R represents a linear or branched, saturated or unsaturated alkyl radical having 8 to 18 carbon atoms and Z_n represents an oligoglycoside radical having an average n = 1 to 3 hexose or pentose units or a mixture thereof, the active compound content being at most 40% by weight.
2. The use of a mixture according to claim 1 as a hydraulic fluid, characterised in that the surface-active additives used are selected from organic sulphates, organic sulphonates, partial esters of phosphoric acid, oxyethylates, carboxymethylated oxyethylates, carboxylic acid salts and quaternary ammonium salts.