SK11922003A3 - Hydraulic fluids with improved anti-corrosion properties - Google Patents

Abstract

The invention relates to hydraulic fluids, in particular brake fluids for motor vehicles, with improved anti-corrosion properties, containing (a) between 0.005 and 0.125 wt. % 1H-1,2,4-triazole and (b) between 0 and 10 wt. % of one or more corrosion inhibitors, whereby with the co-use of 1H-1,2,3-benzotriazole and/or 1H-1,2,3-tolyltriazole and/or their derivatives, the weight ratio of 1H-1,2,4-triazole to the aforementioned 1H-1,2,3-triazoles must be greater than 4:1.

Description

The present invention relates to hydraulic fluids, in particular brake fluids for motor vehicles, with improved anti-corrosion properties, comprising as component (a) 1 H-1,2,4-triazole and as component (b) one or more corrosion inhibitors.

SUMMARY OF THE INVENTION

The present invention relates to hydraulic, in particular brake fluids, for motor vehicles providing improved corrosion protection comprising (a) from 0.005 to 0.125% by weight of 1H-1,2,4-triazole, and (b) from 0 to 10% by weight one or more other corrosion inhibitors, wherein, by the simultaneous use of 1H-1,2,3-benzotriazole and / or 1H-1,2,3-tolyltriazole and / or derivatives thereof, a weight ratio between 1H-1,2,4-triazole and said 1 H-1,2,3-triazoles must be greater than 4: 1.

Hydraulic fluids, and in particular brake fluids for motor vehicles, are subject to very high requirements regarding their chemical and physical properties. According to existing standards and technical regulations for brake fluids of the US Department of Transportation in Federal Motor Vehicle Safety Standard FMVSS-No. 116 and according to SAE J 1704 standards published by Society of Automotive Engineers, modern brake fluids on the one hand should have high dry boiling points (equilibrium reflux boiling points, "ERBP") and high wet boiling points (wet ERBP). (“Wet ERBP”)), but on the other hand, they should also have a viscosity that varies only slightly over a wide temperature range.

In addition, there are several exacting requirements from the automotive industry to improve corrosion protection for metals and non-ferrous metals. Corrosion inhibitors in brake fluids are intended to prevent the destruction of metal materials caused by corrosion.

The use of 1H-1,2,3-triazoles such as 1H-1,2,3-benzotriazole or 1H-1,2,3-tolyltriazole as corrosion inhibitors in hydraulic fluids or brake fluids has been known for some time, for example from European patent applications EP-A 028 789 (1) and EP-A 454 110 (2).

International patent document WO 00/46325 (3) recommends hydraulic fluids containing a combination of 1H-1,2,3-benzotriazole or its derivatives such as 1H-1,2,3-tolyltriazole and 1H-1,2,4 -triazole or derivatives thereof, in a weight ratio of 1: 4 to 4: 1, as a corrosion inhibitor system. For purposes of comparison, Tables 1 to 4 in (3) also disclose hydraulic fluids containing 1H-1,2 alone, 4-triazole in concentrations of 0.15% by weight; however, its corrosion inhibiting effect is acceptable only in the case of copper.

However, hydraulic fluids and brake fluids for motor vehicles known from the prior art are still insufficient in terms of their properties and, in particular, their corrosion protection. It is therefore an object of the present invention to provide hydraulic fluids which in particular satisfy the above-mentioned requirements for improving corrosion protection in the case of metals and non-ferrous metals.

We have surprisingly found that this objective can be achieved by the hydraulic or energy-transferring fluids defined in the introduction.

Hydraulic fluids, in particular brake fluids for motor vehicles, according to the present invention suitably comprise from 0.005 to 0.10% by weight, preferably from 0.005 to 0.08% by weight, particularly preferably from 0.005 to 0.06% by weight, of component (a).

In a preferred embodiment, hydraulic fluids, in particular brake fluids for motor vehicles, according to the present invention comprise component (a) as a triazole-based corrosion inhibitor. This is understood to mean that triazoles such as 1H-1,2,3-benzotriazole, 1H-1,2,3-tolyltriazole or hydrogenated 1H-1,2,3-tolyltriazole are excluded, but inorganic and and / or organic corrosion inhibitors having a different structure may be present.

In a further preferred embodiment, the hydraulic fluids according to the present invention, in particular motor vehicle brake fluids, may also contain up to 10% by weight, in particular up to 5% by weight, of one or more other corrosion inhibitors (b), where -1,2,3-benzotriazole and / or 1H-1,2,3-tolyltriazole and / or derivatives thereof, the weight ratio between 1H-1,2,4-triazole and said 1H-1,2,3-triazoles must be higher than 4: 1.

Suitable further corrosion inhibitors (b) are in particular the alkali metal salts of phosphoric acid and phosphoric acid, fatty acids such as caprylic acid, lauric acid, palmitic acid, stearic acid or oleic acid, and their alkali metal salts, phosphoric acid esters and phosphoric acid , such as ethyl phosphate, dimethyl phosphate, isopropyl phosphate, diisopropyl phosphate, butyl phosphate or dimethyl phosphate, substituted or unsubstituted ethoxylated mono- and dialkylamines and their salts with mineral acids and fatty acids, for example butylamines, butylamines, octylamine, isononylamine, oleylamine, dipropylamine, diisopropylamine or dibutylamine, substituted or unsubstituted ethoxylated alkanolamines, for example mono-, di- or triethanolamine, N, N'-di-n-butylaminoethanol or 1,1'-iminodipropane-2- ol, cyclohexylamine, benzimidazole and hydrogenated tolyltriazole, and nitroaromatic compounds such as 3-nitrobenzaldehyde.

Said corrosion inhibitors (b) according to the present invention are preferably present in hydraulic fluids, in particular in brake fluids for motor vehicles, in amounts of from 0.001 to 10% by weight, preferably from 0.001 to 5% by weight.

In a particularly preferred embodiment, hydraulic fluids, in particular brake fluids for motor vehicles, according to the present invention comprise, in addition to 1H-1,2,4-triazole (a), from 0.001 to 5% by weight, preferably from 0.001 to 0.5% by weight , one or more of benzimidazole, hydrogenated 1H-1,2,3-tolyltriazole, purine, adenine, 6-chloropurine, 2,6-dichloropurine, 6-methoxypurine, 1H-1,2,3-triazolo ( 4,5

b) pyridine, 6-histaminopurine and 6-furfurylaminopurine. and optionally other corrosion inhibitors other than (a) such as additional corrosion inhibitors (b). Said purine derivatives are described in German patent application P 100 26 010.1 as corrosion inhibitors of non-ferrous metals for hydraulic fluids or for brake fluids.

All percentages and weight percentages given above are in each case based on the total amount of hydraulic fluid or brake fluid, unless otherwise indicated. The sum of all the above and below components for the hydraulic or brake fluids of the present invention is in any case up to 100% by weight.

In particular, the present invention relates to brake fluids for motor vehicles comprising, as corrosion inhibitors, said components (a) and optionally components (b).

In a preferred embodiment, the brake fluids for motor vehicles according to the present invention further comprise, in addition to components (a) and optionally (b), from 0.1 to 97% by weight, preferably from 30 to 97% by weight, particularly preferably from 50 to 97% by weight. , one or more polyglycol ethers and / or borates thereof.

Suitable polyglycol ethers are, in particular, ethylene glycol monoalkyl ethers which contain up to 6 ethylene oxide units and contain up to 4 carbon atoms in the alkyl moiety, such as diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether or tetraethylene glycol ether. Also suitable are ethylene glycol dialkyl ethers and propylene glycol dialkyl ethers which contain up to 6 alkylene oxide units and contain up to 4 carbon atoms in each of the alkyl radicals, such as triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether.

Suitable boronic esters of the aforementioned or other polyglycol ethers are described in particular in patent documents EP-B 013 925 (cyclic bisboric acid esters), DE-C 28 04 535 (nitrogen-containing boronic esters), DE-A

38,038 (alkylene glycol monoalkylether esters of boric acid) and DE-B 17 68 933 (trisalkoxyalkylesters of boric acid).

Instead of the aforementioned polyglycol ethers and / or boric acid esters thereof, the brake fluids for motor vehicles according to the present invention may also contain as base component compounds based on carboxylic acid esters, mineral oils or silicone oils.

In another preferred embodiment, the brake fluids for motor vehicles of the present invention further comprise, in addition to components (a) and optionally (b), from 0.1 to 50% by weight, preferably from 1 to 40% by weight, particularly preferably from 5 to 30% by weight, % of one or more polyglycols.

Suitable polyglycols are in particular products of the reaction of ethylene oxide and / or propylene oxide and / or butylene oxide with water or diols having a relatively high boiling point, in particular the corresponding products of mixtures of ethylene oxide and propylene oxide with water. The number of alkylene oxide in polyglycols of this type is usually from 2 to 10.

The effect of these high boiling polyglycols is that they act as a lubricant, which substantially contributes to improving the temperature / viscosity property. The polyglycols provide low viscosity polyglycol ethers sufficient for high temperature viscosity to provide adequate lubrication. Adequate lubrication is needed in the components of the braking system of motor vehicles, since in these systems rubber or elastomers must slide on the metal with very low wear.

The other components and excipients in the brake fluids of motor vehicles according to the present invention may be conventional antioxidants, for example phenothiazine and / or phenol-based compounds, and conventional antifoams.

In addition, the brake fluids of the present invention may comprise cyclic carboxylic acid derivatives disclosed in WO 00/65001, which are useful as components for reducing low temperature viscosity in the presence of water.

The presence of said small amount of 1H-1,2,4-triazole in an excellent manner ensures that the hydraulic or brake fluids for motor vehicles of the present invention meet the requirements of the present invention.

At the outset, and in particular, the corrosion properties that are generally well comparable to the prior art are influenced, i. improving corrosion protection for metals such as iron, steel, tinplate, cast iron, lead, tin, chromium, zinc, aluminum, magnesium and their alloys, and solder metals such as solder tin and non-ferrous metals such as copper and alloys thereof such as brass.

Further advantages of hydraulic fluids or brake fluids for motor vehicles according to the present invention are their excellent low temperature viscosity, good water compatibility, moderate pH, good low and high temperature stability and good oxidation stability as well as good chemical stability, excellent properties (ie, good compatibility) with materials such as rubbers, plastics, adhesive layers, fibers, elastomers and rubber seals and the like, as well as good lubricating properties.

Not least, the use of only a small amount of 1H-1,2,4-triazole in hydraulic or brake fluids for motor vehicles according to the present invention is advantageous both economically and environmentally.

The examples below describe the present invention in more detail without limiting it in any sense.

DETAILED DESCRIPTION OF THE INVENTION

Examples of use

Based on commercially available DOT 4 or DOT 5.1 brake fluids BF 1 (ERBP: 267 ° C, wet ERBP: 173 ° C, kinematic viscosity at -40 ° C: 676 cSt) and BF 2 (ERBP: 263 ° C, wet ERBP: 181 ° C, kinematic viscosity at -40 ° C: 850 cSt) in each case containing 0.05% w / w 1H-

1,2,3-tolyltriazole as a non-ferrous metal corrosion inhibitor was tested in comparison with the brake fluids BF 1a, BF 1b, BF 1c and BF 2a of the present invention.

The brake fluid used for motor vehicles had the following compositions:

-7BF 1:

55.00% by weight triethylene glycol methyl ether, 43.44% by weight mixtures of triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, triethylene glycol monobutyl ether and diethylene glycol monomethyl ether, 1.51% by weight mixtures of 1,1'-iminodipropan-2-ol, phenothiazine and phosphoric acid ester, 0.05% by weight 1H-1,2,3-tolyltriazole

BF 2:

68.00% by weight triethylene glycol methyl ether, 28.84% by weight mixtures of triethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether and diethylene glycol, 3.11% by weight mixtures of 1,1'-iminodipropan-2-ol, phenothiazine and phosphorous acid derivative, 0.05% by weight 1H-1,2,3-tolyltriazole.

The brake fluids BF 1a and BF 2a of the present invention differ from BF 1 and BF 2 only in that 0.05% by weight of 1H-1,2,3-tolyltriazole has been replaced with the same amount of 1H-1,2,4-triazole ; BF 1b brake fluid contains 0.04 wt% 1H-1,2,4-triazole and 0.01 wt% adenine, instead of 0.05 wt% 1H-1,2,3-tolyltriazole; The BF 1c brake fluid of the invention contains 0.07 wt% 1H-1,2,4-triazole (but only 54.98 wt% triethylene glycol monomethyl ether borate) instead of 0.05 wt% 1H-1,2,3-tolyltriazole.

The use studies were conducted in accordance with the PSA Peugeot-Citroen D 53 5387 copper corrosion test version 2000. In this test, the copper plate, which had been pre-cleaned in acetone, had a total surface area of 1000 cm ² (dimensions:

(71.4 cm x 7 cm x 0.05 cm) was rolled into a circular cylinder in such a way that the metal surface of the inner part was not in contact with each other. The copper plate was placed in a mixture of 294 ml brake fluid containing 6 ml distilled water and heated at 100 ° C for 100 hours; 10 liters of air per hour were passed through the liquid, and the air was previously passed through distilled water cooled to 2 ° C. At the end of the test, the appearance of the unwound copper plate and the appearance of the liquid were evaluated visually and the copper content of the liquid was determined.

The results from the above test were summarized in Table 1 below.

Table 1

Cu content [Mg / kg] Cu plate appearance Liquid, look pH BF 1 (Compare): 24 Coarse coating Cloudy, precipitates 7.4 BF 1a: 29 Lights, uncoated Amber color, clear 7.6 BF 1b: 34 Lights, uncoated Amber color, clear 7.6 BF 1c: 18 Lights, uncoated Amber color, clear 7.5 BF2 (Compare): 10 Coarse coating Cloudy, precipitates 7.6 BF 2a: 30 Lights, uncoated Amber color, clear 7.7

From the above, it can be seen that the formulations of the present invention, in contrast to conventional brake fluids such as BF 1 and BF 2, not only provide very good copper protection against low Cu corrosion in the test fluid, but additionally also provide a metal surface without coating and do not form sediment in the brake fluid.

The results below for the corrosion test of SAE J 1704 (Jan. 97) also confirm that the brake fluids of the present invention, such as BF 2a, having a low 1H-1,2,4-triazole content, provide advantages over non-subject formulations, such as BF 1d, with a high content of 1H-1,2,4-triazole, because they show better corrosion results in the case of copper (BF 1d corresponds to BF 1 but contains 0.20% by weight of 1H-1, 2,4-triazole, instead of 1H-1,2,3-tolyltriazole and consists only of 54.85% by weight of triethylene glycol monomethyl etherborate).

The results of the corrosion tests according to SAE J 1704 (Jan. 97) are summarized in the following Table 2.

Table 2

metal BF 2a Weight change [mg / cm ² ] BF 1d (comparison) Weight change [mg / cm ² ] Tin plate 0.00 -0.01 steel +0.03 0.00 aluminum 0.00 0.00 cast iron +0.05 +0.02 Brass 0.00 0.00 copper -0.05 -0.11 zinc +0.05 +0.04

Claims (5)

Brake fluid for motor vehicles with improved corrosion protection, characterized in that it contains (a) from 0.005 to 0.125% by weight of 1H-1,2,4-triazole, and (b) from 0 to 10% by weight of one or a plurality of other corrosion inhibitors, wherein, by the simultaneous use of 1H-1,2,3-benzotriazole and / or 1H-1,2,3-tolyltriazole and / or derivatives thereof, a weight ratio between 1H-1,2,4-triazole and said 1H-1,2,3-triazoles must be greater than 4: 1. and in addition from 0.1 to 97% by weight of one or more polyglycol ethers and / or boronic esters thereof. Brake fluid for motor vehicles according to claim 1, characterized in that it contains from 0.005 to 0.08% by weight of component (a). Motor vehicle brake fluid according to claim 1 or 2, characterized in that it comprises component (a) as the only triazole-based corrosion inhibitor. Motor vehicle brake fluid according to claim 1 or 2, characterized in that it contains as component (b) from 0.001 to 0.5% by weight of one or more compounds selected from the group consisting of benzimidazole, hydrogenated 1 H-1,2, 3-tolyltriazole, purine, adenine, 6-chloropurine, 2,6-dichloropurine, 6-methoxypurine, 1H-1,2,3-triazolo (4,5-b) pyridine, 6-histaminopurine and 6furfurylaminopurine, and optionally other corrosion inhibitors other than (a). Motor vehicle brake fluid according to one of Claims 1 to 4, characterized in that it contains, in addition to components (a) and optionally (b), from 0.1 to 50% by weight of one or more polyglycols.