CN1312261C - Hydraulic fluids with improved corrosion resistance - Google Patents

Abstract

The present invention relates to a hydraulic fluid with improved corrosion protection properties, in particular a brake fluid for motor vehicles, comprising: (a) 0.005-0.125 wt. % of 1H-1,2,4-triazole, and (b) 0-10 wt. % of one or more other corrosion inhibitors, wherein when 1H-1,2,3-benzotriazole and/or 1H-1,2,3-toluenetriazole and/or derivatives thereof are concomitantly used, the weight ratio of 1H-1,2,4-triazole to the 1H-1,2,3-triazoles must be greater than 4:1.

Description

Hydraulic fluids with improved corrosion resistance

The present invention relates to hydraulic fluids with improved corrosion protection properties, in particular brake fluids for motor vehicles, comprising:

(a) 0.005-0.125% by weight of 1H-1,2,4-triazole, and

(b) 0-10% by weight of one or more other corrosion inhibitors, wherein concomitant use of 1H-1,2,3-benzotriazole and/or 1H-1,2,3-tolyltriazole and In the case of / or its derivatives, the weight ratio of 1H-1,2,4-triazole to said 1H-1,2,3-triazole must be greater than 4:1.

Very high demands are placed on the chemical and physical properties of hydraulic fluids, especially brake fluids for motor vehicles. According to the Federal Motor Vehicle Safety Standard FMVSS-No.116 and the SAE J 1704 standard (Federal Motor Vehicle Safety Standard FMVSS-No.116 and the SAE J 1704 standard) published by the Society of Automotive Engineers, the US Department of Transportation has existing regulations on brake fluid. Standards and specifications, modern brake fluids should have on the one hand a high dry boiling point (Equilibrium Return Boiling Point "ERBP") and a high wet boiling point ("Wet ERBP"), and on the other hand should have only slightly Changing viscosity.

Furthermore, the automotive industry has more stringent requirements for improved corrosion protection in the case of metallic and non-ferrous metals. Corrosion inhibitors in brake fluids are used to prevent damage to metallic materials caused by corrosion.

For some time, 1H-1,2,3-triazoles such as 1H-1,2,3-benzotriazole or 1H-1,2,3-tolyltriazole have been used as buffers in hydraulic fluids or brake fluids. Etches are known, see for example EP-A 028 789 (1) and EP-A 454 110 (2).

WO 00/46325(3) describes hydraulic fluids containing 1H-1,2,3-benzotriazole or derivatives thereof (such as 1H-1,2,3 -tolutriazole) and a mixture of 1H-1,2,4-triazole or its derivatives as its corrosion inhibitor system. For comparison, Tables (1)-(4) in (3) also introduce hydraulic fluids containing only 1H-1,2,4-triazole at a concentration of 0.15% by weight; however, its corrosion inhibition effect is only on copper case is acceptable.

However, the hydraulic fluids and brake fluids for engines known in the prior art are still unsatisfactory in terms of their properties, especially their corrosion resistance. It is therefore an object of the present invention to provide a hydraulic fluid which is able to meet the abovementioned requirements for improved corrosion protection, especially in the case of metallic and non-ferrous metals.

We have found that this object can be achieved by a hydraulic or power transmission fluid as defined at the outset.

The hydraulic fluids according to the invention, in particular motor vehicle brake fluids, preferably contain 0.005-0.10% by weight, preferably 0.005-0.08% by weight, especially 0.005-0.06% by weight, of component (a).

In a preferred embodiment, the hydraulic fluids according to the invention, in particular motor vehicle brake fluids, contain component (a) as the only triazole corrosion inhibitor. This means that triazoles such as 1H-1,2,3-benzotriazole, 1H-1,2,3-tolyltriazole or hydrogenated 1H-1,2,3-tolyltriazole are excluded here , while inorganic and/or organic corrosion inhibitors with different structures can exist.

In another preferred embodiment, the hydraulic fluid according to the invention, in particular the brake fluid of a motor vehicle, also contains at most 10% by weight, in particular at most 5% by weight, of one or more other corrosion inhibitors (b), wherein In the case of concomitant use of 1H-1,2,3-benzotriazole and/or 1H-1,2,3-tolyltriazole and/or derivatives thereof, 1H-1,2,4-triazole and The weight ratio of said 1H-1,2,3-triazoles must be greater than 4:1.

Further corrosion inhibitors (b) suitable here are in particular alkali metal salts of phosphoric acid and phosphorous acid; fatty acids and their alkali metal salts, such as caprylic acid, lauric acid, palmitic acid, stearic acid or oleic acid; Esters such as ethyl phosphate, dimethyl phosphate, isopropyl phosphate, diisopropyl phosphate, butyl phosphite or dimethyl phosphite; substituted or unsubstituted ethoxylated mono- and dialkyl Amines and their salts with inorganic acids and fatty acids, such as butylamine, hexylamine, octylamine, isononylamine, oleylamine, dipropylamine, diisopropylamine or dibutylamine; substituted or unsubstituted ethoxylated alkanes Alcoholamines such as mono-, di- or triethanolamine, N,N'-di-n-butylaminoethanol or 1,1'-iminodipropan-2-ol, cyclohexylamine, benzimidazole and hydrogenated toluene Triazoles, and nitroaromatics such as 3-nitrobenzaldehyde.

The content of the corrosion inhibitor (b) in the hydraulic fluid of the present invention, especially the brake fluid for motor vehicles, is 0.001-10% by weight, especially 0.001-5% by weight.

In a particularly preferred embodiment, the hydraulic fluid according to the invention, in particular the brake fluid of a motor vehicle, contains, in addition to 1H-1,2,4-triazole (a), 0.001-5% by weight, in particular 0.001-0.5% by weight of one or more selected from benzimidazole, hydrogenated 1H-1,2,3-tolyltriazole, purine, adenine, 6-chloropurine, 2,6-dichloropurine, 6- Compounds of methoxypurine, 1H-1,2,3-triazole(4,5-b)pyridine, 6-histaminepurine and 6-furfurylaminopurine, and if desired, other than (a) Other corrosion inhibitors as additional corrosion inhibitors (b). Purine derivatives described in German patent application P10026010.1 are used as corrosion inhibitors for non-ferrous metals in hydraulic fluids or brake fluids.

All percentages by weight data given in the context and in each case are relative to the total amount of hydraulic fluid or brake fluid, unless otherwise stated. In each case, the weight of all components of the hydraulic fluid or brake fluid according to the invention cited above and below add up to a maximum of 100% by weight.

The invention relates in particular to brake fluids for motor vehicles comprising component (a) as corrosion inhibitor and, if desired, component (b).

In a preferred embodiment, the motor vehicle brake fluid according to the invention comprises, in addition to (a) and if desired (b), 0.1-97% by weight, in particular 30-97% by weight, especially 50-97% by weight % of one or more polyglycol ethers and/or borate esters thereof.

Suitable polyglycol ethers here are in particular ethylene glycol monoalkyl ethers having up to 6 ethylene oxide units and up to 4 carbon atoms in the alkyl moiety, for example diethylene glycol monomethyl ether, triethylene glycol Monomethyl ether or tetraethylene glycol monobutyl ether. Ethylene glycol dialkyl ethers and propylene glycol dialkyl ethers having up to 6 alkylene oxide units and up to 4 carbon atoms in each alkyl moiety are also suitable, for example triethylene glycol dimethyl ether, tetraethylene glycol Dimethyl ether, diethylene glycol di-tert-butyl ether, diethylene glycol dibutyl ether, butyl diglycol tert-butyl ether, or dipropylene glycol dimethyl ether.

Especially in EP-B013925 (cyclic diboronic acid ester), DE-C2804535 (nitrogen-containing boric acid ester), DE-A2438038 (boronic acid alkylene glycol monoalkyl ether ester) and DE-B1768933 (boric acid trialkyl Suitable borate esters of these or other polyglycol ethers are described in the specification for oxyalkyl esters.

In addition to the polyglycol ethers and/or their borate esters, the motor vehicle brake fluids according to the invention may also contain, as customary components, those substances based on carboxylic acid esters, mineral oils or silicone oils.

In a further preferred embodiment, the motor vehicle brake fluid according to the invention contains, in addition to components (a) and if desired (b), 0.1-50% by weight, in particular 1-40% by weight, especially 5-30% by weight of one or more polyglycols.

Suitable polyglycols here are in particular the relatively high-boiling reaction products of ethylene oxide and/or propylene oxide and/or butylene oxide with water or glycols, especially ethylene oxide and epoxy The corresponding product of a mixture of propane and water. The number of alkylene oxide units of this type of polyglycol is generally 2-10.

These high boiling point polyglycols act as lubricants, essentially to enhance temperature/viscosity performance. The polyglycol imparts sufficient viscosity to the low-viscosity polyglycol ether at high temperatures and thus ensures adequate lubrication. Adequate lubrication is essential in components of motor vehicle braking systems, since in these systems rubber or elastomers must slide on metal with very low losses.

In the motor vehicle brake fluids according to the invention, further components and adjuvants may be conventional antioxidants, such as phenothiazines and/or those based on phenols, and conventional antifoams.

Furthermore, the brake fluid of the present invention may contain the cyclic carboxylic acid derivatives mentioned in WO 00/65001, which are suitable as components for lowering low-temperature viscosity in the presence of water.

The presence of said small amount of 1H-1,2,4-triazole ensures in an excellent manner that the hydraulic fluid or motor vehicle brake fluid according to the invention complies with the requirements stated above, especially on metals such as iron, stainless steel, tinplate, In the case of pig iron (gray iron), lead, tin, chromium, zinc, aluminium, magnesium and their alloys, and in the case of welding metals such as solder, and in the case of non-ferrous metals such as copper and its alloys such as brass , Compared with the prior art, it has very good anti-corrosion performance, that is, improved anti-corrosion performance.

Other advantages of the hydraulic fluid or motor vehicle brake fluid of the present invention are its good low-temperature viscosity, good water compatibility, mild pH, good low-temperature, high-temperature and oxidation stability, and compatibility with rubbers, plastics, gum lines, etc. , fibers, elastomers and rubber sealing ring materials and similar materials have good characteristics (ie excellent compatibility), and excellent lubricating properties.

The use of only small amounts of 1H-1,2,4-triazole in the hydraulic fluid or motor vehicle brake fluid according to the invention is quite advantageous from an economical and ecological point of view.

The following examples serve to illustrate the invention without limitation.

Application example

Based on commercially available DOT4 or DOT5.1 brake fluid BF1 (ERBP: 267°C, wet ERBP: 173°C, dynamic viscosity at -40°C: 676cSt) and BF 2 (ERBP: 263°C, wet E RBP: 181°C, - Dynamic viscosity at 40°C: 850cSt) with 0.05% by weight of 1H-1,2,3-tolyltriazole as non-ferrous metal corrosion inhibitor, BF1a, BF1b, BF1c and BF2a of the present invention were detected for comparison.

The motor vehicle brake fluid used has the following composition:

BF1:

55.00% by weight triethylene glycol methyl ether borate,

43.44% by weight of a mixture of triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, triethylene glycol monobutyl ether and diethylene glycol monomethyl ether,

1.51% by weight of a mixture of 1,1'-iminodipropan-2-ol, phenothiazine and phosphate esters,

0.05% by weight of 1H-1,2,3-tolyltriazole

BF2:

68.00% by weight triethylene glycol methyl ether borate,

28.84% by weight of a mixture of triethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether and diethylene glycol,

3.11% by weight of a mixture of 1,1'-iminodipropan-2-ol, phenothiazine and phosphonic acid derivatives,

0.05% by weight of 1H-1,2,3-tolyltriazole.

The difference between brake fluid BF1a and BF2a of the present invention and BF1 and BF2 is only that 0.05% by weight 1H-1,2,3-tolyltriazole is replaced by the same amount of 1H-1,2,4-triazole; Brake fluid BF1b contains 0.04 wt% 1H-1,2,4-triazole and 0.01 wt% adenine instead of 0.05 wt% 1H-1,2,3-tolyltriazole; brake fluid BF1c of the present invention contains 0.07 % by weight 1H-1,2,4-triazole (but only 54.98% by weight triethylene glycol monomethyl ether borate), instead of 0.05% by weight 1H-1,2,3-tolyltriazole.

The applied research was carried out according to the 2000 edition of the PSA Peugeot-Citroёn D535387 copper corrosion test. In this experiment, a copper sheet with a total surface area of 1000 cm ² (dimensions: 71.4 cm × 7 cm × 0.05 cm) previously cleaned in acetone was rolled into a cylinder so that the inner metal surface would not self contact. The copper piece was then placed in a mixture containing 294ml of brake fluid and 6ml of distilled water, and heated to 100°C for 100 hours; the air previously passed through the distilled water cooled to 2°C was passed through the fluid at a rate of 10 liters/hour. After the experiment, the appearance of the unfolded copper sheet and the appearance of the fluid were visually evaluated, and the copper content in the fluid was determined.

The experimental results are shown in Table 1 below.

Table 1:

Cu content [mg/kg] Cu sheet appearance fluid appearance pH BF1 (control): twenty four thick coating turbidity, precipitation 7.4 BF1a: 29 bright, uncoated amber, clear 7.6 BF1b: 34 bright, uncoated amber, clear 7.6 BF1c: 18 bright, uncoated amber, clear 7.5 BF2 (control): 10 thick coating turbidity, precipitation 7.6 BF2a: 30 bright, uncoated amber, clear 7.7

As can be seen from the comparison with conventional brake fluids, the formulations of the present invention, such as BF1 and BF2, not only provide very good copper corrosion resistance at the lower Cu content in the experimental fluid, but also obtain coating-free metal surfaces and no deposits form in the brake fluid.

The following also proves that according to the results of SAE J 1704 (January 97) corrosion test, the brake fluid of the present invention with lower 1H-1,2,4-triazole content, such as BF2a, is better than non-present invention 1H-1 , formulations with a higher 2,4-triazole content, such as BF1d, because the brake fluids according to the invention show better corrosion results in the case of copper (BF1d corresponds to BF1, but contains 0.20% by weight 1H-1, 2,4-triazole instead of 1H-1,2,3-tolyltriazole and only 54.85% by weight triethylene glycol monomethyl ether borate):

Table 2 below shows the results of corrosion experiments conducted in accordance with SAE J 1704 (January 97).

Table 2:

Metal Weight change of BF2a [mg/cm ² ] Weight change of BF1d (control) [mg/cm ² ] tinplate 0.00 -0.01 Stainless 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)

1. A brake fluid for motor vehicles with improved anti-corrosion properties, comprising: (a) 0.005-0.125% by weight of 1H-1,2,4-triazole, and (b) 0-5% by weight of one or more other corrosion inhibitors, wherein concomitant use of 1H-1,2,3-benzotriazole and/or 1H-1,2,3-tolyltriazole and / or its derivatives, the weight ratio of 1H-1,2,4-triazole and said 1H-1,2,3-triazole must be greater than 4:1, 0.1-97% by weight of one or more polyglycol ethers and/or borate esters thereof are also included. 2. The brake fluid for motor vehicles according to claim 1, comprising 0.005-0.08% by weight of component (a). 3. Brake fluid for motor vehicles according to claim 1 or 2, containing component (a) as the only triazole-based corrosion inhibitor. 4. The brake fluid for motor vehicles according to claim 1 or 2, containing 0.001-0.5% by weight of one or more selected from benzimidazole, hydrogenated 1H-1,2,3-tolyltriazole, purine, Adenine, 6-chloropurine, 2,6-dichloropurine, 6-methoxypurine, 1H-1,2,3-triazole (4,5-b)pyridine, 6-histamine purine and 6- Compounds of furfurylaminopurine and, if desired, other corrosion inhibitors besides (a) as component (b). 5. The brake fluid for motor vehicles according to any one of claims 1-4, comprising, in addition to components (a) and (b) if desired, 0.1-50% by weight of one or more polyglycol.