PL197796B1 - 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

Description of the invention

The present invention relates to a brake fluid for motor vehicles.

Hydraulic fluids, and in particular brake fluids for motor vehicles, must meet very stringent requirements as to their chemical and physical properties. According to the applicable standards and requirements for brake fluids, established by the US Department of Transportation in Federal Motor Vehicle Safety Standard FMVSS-No. 116, and the SAE J 1704 standard published by the Society of Automotive Engineers, modern brake fluids should have a high "boiling point when dry" (determined at equilibrium on reflux - ERPB) and high wet boiling point ("wet ERPB), and viscosity varies slightly over a wide temperature range.

In addition, the car industry imposes stricter requirements for better corrosion protection for metals and non-ferrous metals. When added to brake fluids, corrosion inhibitors are designed to prevent corrosion damage to metal parts.

The use of 1H-1,2,3-triazole derivatives such as 1H-1,2,3-benzotriazole or 1H-1,2,3-tolutriazole as corrosion inhibitors in hydraulic or brake fluids has been known for a long time, e.g. EP-A 028789 (1) and EP-A 454110 (2).

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-tolutriazole, and 1H-1,2,4-triazole or its derivatives derivatives in a weight ratio of 1: 4 to 4: 1 for use as a corrosion inhibitor system. For comparison, Tables 1-4 in (3) also show the properties of hydraulic fluids containing only 1H-1,2,4-triazole at a concentration of 0.15% by weight; however, its anti-corrosion effect can only be considered sufficient for copper.

The prior art hydraulic fluids and brake fluids for motor vehicles do not show satisfactory properties, in particular anti-corrosion effect. Thus, there was a need for hydraulic fluids, and in particular brake fluids, meeting in particular the above requirements for improved corrosion protection for metals and non-ferrous metals.

It has surprisingly been found that a brake fluid having the appropriate composition given below meets these requirements.

The invention relates to a brake fluid for motor vehicles, characterized in that it comprises:

(a) 0.005-0.125% by weight of 1H-1,2,4-triazole and (b) 0-10% by weight of one or more additional corrosion inhibitors, whereby 1H-1,2,3-benzotriazole and / or 1H-1,2,3-tolutriazole and / or derivatives thereof, the weight ratio of the 1H-1,2,4-triazole to the 1H-1,2,3-triazoles is greater than 4: 1 and furthermore 0.1 - 97% by weight of one or more polyglycol ethers and / or their esters with boric acid.

Preferably, the brake fluid contains 0.005-0.08% by weight of component (a).

Preferably, the brake fluid comprises component (a) as the sole triazole-based corrosion inhibitor.

Preferably, the brake fluid comprises as component (b) 0.001-0.5% by weight of one or more compounds from the group consisting of benzimidazole, hydrogenated 1H-1,2,3-tolutriazole, 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 additional corrosion inhibitors other than (a).

Preferably, the brake fluid further comprises, in addition to components (a) and optionally (b), 0.1-50% by weight of one or more polyglycols.

The brake fluids according to the invention preferably contain 0.005-0.10% by weight, more preferably 0.005-0.08% by weight, more preferably 0.005-0.06% by weight, of component (a).

The brake fluids of the invention preferably contain component (a) as the sole triazole-based corrosion inhibitor. This means that they do not contain triazole derivatives such as 1H-1,2,3-benzotriazole, 1H-1,2,3-tolutriazole or hydrogenated 1H-1,2,3-tolutriazole, but may contain inorganic and / or organic corrosion inhibitors of a different structure.

The brake fluids according to the invention also contain up to 10% by weight, in particular up to 5% by weight, of one or more additional corrosion inhibitors (b), provided that when 1H-1,2,3-benzotriazole and / or 1H-1 are used simultaneously , 2,3-tolutriazole and / or derivatives thereof, the weight ratio of 1H-1,2,4-triazole to these 1H-1,2,3-triazoles must be greater than 4: 1.

PL 197 796 B1

Suitable additional corrosion inhibitors (b) are the alkali metal salts of phosphoric and phosphorous acid; fatty acids such as octanoic, lauric, palmitic, stearic or oleic acid and their alkali metal salts; phosphoric and phosphorous acid esters such as ethyl phosphate, dimethyl phosphate, isopropyl phosphate, diisopropyl phosphate, butyl phosphite or dimethyl phosphite; optionally substituted ethoxylated mono- and dialkylamines and their mineral acid and fatty acid salts, e.g., butylamine, hexylamine, octylamine, isononylamine, oleylamine, dipropylamine, diisopropylamine or dibutylamine; optionally substituted ethoxylated alkanolamines, e.g. mono-, di- or triethanolamine, N, N'-di-n-butylaminoethanol or 1,1'-iminodipropan-2-ol, cyclohexylamine, benzimidazole and hydrogenated tolutriazole; and nitroaromatics, e.g. 3-nitrobenzaldehyde.

The corrosion inhibitors (b) are preferably used in the brake fluids according to the invention in an amount of 0.001-10% by weight, in particular 0.001-5% by weight.

The brake fluids according to the invention contain in addition to 1H-1,2,4-triazole (a) preferably 0.001-5% by weight, in particular 0.001-0.5% by weight, one or more compounds selected from the group consisting of benzimidazole, hydrogenated 1H-1 , 2,3-tolutriazole, 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 additional corrosion inhibitors other than (a) as additional corrosion inhibitors (b). The aforementioned purine derivatives are described in the German patent application P 10026010.1 as corrosion inhibitors of non-ferrous metals for use in hydraulic fluids or brake fluids.

Unless otherwise stated, all% by weight data are based on the total amount of brake fluid in each case. The total amount of all components present in the brake fluids according to the invention is in each case 100% by weight.

In particular, the brake fluids according to the invention contain the above-described components (a) and, if appropriate, (b) as corrosion inhibitors.

The brake fluids according to the invention contain, in addition to components (a) and, if appropriate, (b), 0.1 to 97% by weight, preferably 30 to 97% by weight, in particular 50 to 97% by weight, of one or more polyglycol ethers and / or their borates.

Suitable polyglycol ethers are, in particular, ethylene glycol monoalkyl ethers with up to 6 ethylene oxide units and up to 4 carbon atoms in the alkyl group, such as, for example, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether or tetraethylene glycol monomethyl ether. Ethylene glycol dialkyl ethers and propylene glycol dialkyl ethers with up to 6 alkylene oxide units and up to 4 carbon atoms in each alkyl group may also be used, such as e.g. triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol di-tert-butyl ether , diethylene glycol dibutyl ether, diethylene glycol di-tert-butyl ether or dipropylene glycol dimethyl ether.

Suitable boric acid esters of the above and other polyglycol ethers are described in EP-B 013925 (cyclic bisboric acid esters), DE-C 2804535 (nitrogen-containing boric acid esters), DE-A 2438038 (alkylene glycol monoalkyl ether esters of boric acid) and in DE-B 1768933 (boric acid trialkoxyalkyl esters).

Instead of the polyglycol ethers and / or their esters with boric acid described above, the brake fluids according to the invention may also contain carboxylic acid esters, mineral oils or silicone oils as their main constituent.

Preferably, the brake fluids according to the invention contain, in addition to components (a) and, if appropriate, (b), 0.1-50% by weight, particularly 1-40% by weight, particularly preferably 5-30% by weight, of one or more polyglycols.

Suitable polyglycols are in particular the reaction products of ethylene oxide and / or propylene oxide and / or butylene oxide with water or diols, in particular suitable reaction products of mixtures of ethylene oxide and propylene oxide with water; all of these compounds have a relatively high boiling point. The number of alkylene oxide units in polyglycols of this type is usually 2-10.

The high boiling point polyglycols described above act as a lubricant which essentially improves performance with temperature and viscosity. The presence of polyglycols gives the low viscosity polyglycol ethers a sufficiently high viscosity at high temperature to provide adequate lubrication. This lubrication is essential in the brake system4

Due to the fact that the rubber or elastomers sliding on metal parts must show a very low degree of wear.

Further ingredients and adjuvants in the brake fluids according to the invention may be known antioxidants, such as, for example, phenothiazine and / or phenol-based agents, and known antifoams.

In addition, the brake fluids of the invention may contain the cyclic carboxylic acid derivatives mentioned in WO 00/65001, used as low temperature viscosity reducing components in the presence of water.

The presence of the above-mentioned small amount of 1H-1,2,4-triazole makes the brake fluids according to the invention meet the requirements set for them and, in particular, show an anti-corrosion effect better than the fluids known from the state of the art, i.e. they provide increased corrosion protection for metals such as iron, steel, tinplate, cast iron (gray cast iron), lead, tin, chrome, zinc, aluminum, magnesium and their alloys, as well as soldering metals such as soldering tin, and non-ferrous metals such as copper and its alloys e.g. brass.

Further advantageous advantages of the brake fluids according to the invention are favorable low temperature viscosity, good miscibility with water, moderate pH value, low and high temperature stability, resistance to oxidation and chemical stability, favorable behavior (i.e. compatibility) with materials such as rubbers, plastics, adhesives, fibers, gaskets of elastomers and rubber and similar materials, as well as good lubricating properties.

Last but not least, the use of even small amounts of 1H-1,2,4-triazole in the brake fluids of the invention is advantageous both from an economic and an ecological point of view.

The following examples illustrate the invention.

Application examples

Based on commercially available DOT 4 or DOT 5.1 brake fluids, BF 1 fluids (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) each containing 0.05 wt. 1H-1,2,3-tolutriazole as a corrosion inhibitor of non-ferrous metals and compared with the brake fluids BF 1a, BF 1b, BF 1c and BF 2a according to the invention.

The brake fluids used for motor vehicles had the following composition.

BF 1

55.00 wt.% triethylene glycol methyl ether borate,

43.44 wt.% mixtures of triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, triethylene glycol monobutyl ether and diethylene glycol monomethyl ether,

1.51 wt.% mixtures of 1,1'-iminodipropan-2-ol, phenothiazine and an ester of phosphoric acid

0.05 wt.% 1H-1,2,3-tolutriazole.

BF 2

68.00 wt.% triethylene glycol methyl ether borate,

28.84 wt.% mixtures of triethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether and diethylene glycol,

3.11 wt.% mixtures of 1,1'-iminodipropan-2-ol, phenothiazine and a phosphonic acid derivative

0.05 wt.% 1H-1,2,3-tolutriazole.

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

The tests were carried out in accordance with the copper corrosion test used by PSA Peugeot Citroen D 53 5387 version 2000. According to this test, a copper sheet previously cleaned in acetone, with a total area of 1000 cm ² (dimensions 71.4 cm x 7 cm x 0.05 cm) was first rolled into a cylinder shape in such a way that the internal surfaces of the metal do not touch each other. The copper sheet was then placed in a mixture of 294 ml of brake fluid and 6 ml of distilled water and heated at 100 ° C for 100 hours; air was passed through the liquid at a rate of 10 liters per hour through distilled water cooled to

Temperature of 2 ° C. After completion of the tests, the appearance of the copper sheet after unwinding and the appearance of the liquid were visually assessed, and its copper content was determined.

The test results are given in Table 1.

T a b e l a 1

Cu content ^[m 9 ^{/ k} 9 ^] The appearance of the copper sheet The appearance of the fluid pH BF 1 (comparative) 24 Thick coating Cloudy, with sediment 7.4 BF 1a 29 Glossy, no coating Amber, transparent 7.6 BF 1b 34 Glossy, no coating Amber, transparent 7.6 BF 1c 18 Glossy, no coating Amber, transparent 7.5 BF 2 (comparative) 10 Thick coating Cloudy, with sediment 7.6 BF 2a thirty Glossy, no coating Amber, transparent 7.7

As can be seen from the above data, in contrast to known brake fluids, such as BF 1 and BF 2, the fluids according to the invention not only provide very good corrosion protection for copper and a low Cu content in the tested fluid, but also the metal surface is not tarnished, and in the brake fluid, no precipitate forms.

The following corrosion test results according to SAE J 1704 (January 97) also confirm the superior performance of the brake fluids of the invention, such as BF 2a, with a low 1H-1,2,4-triazole content, compared to other fluids such as as BF 1d with a high content of 1H-1,2,4-triazole, as better corrosion test results were obtained for copper (BF 1d is equivalent to BF 1, but contains 0.20 wt.% of 1H-1,2,4-triazole instead of 1H-1,2,3-toluotriazl and contains only 54.85 wt.% of triethylene glycol monomethyl ether borate).

The corrosion test results according to SAE J 1704 (January 97) are shown in Table 2.

T a b e l a 2

Metal BF 2a Mass change [mg / cm ² ] BF 1d (comparative) Mass change [mg / cirr] Tinned sheet 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

Patent claims

Claims (5)

1. Brake fluid for motor vehicles, characterized in that it contains: (a) 0.005-0.125% by weight of 1H-1,2,4-triazole and (b) 0-10% by weight of one or more additional corrosion inhibitors, whereby 1H-1,2,3-benzotriazole and / or 1H-1,2,3-tolutriazole and / or derivatives thereof, the weight ratio of 1H-1,2,4-triazole to these 1H-1,2,3-triazoles is greater than 4: 1, and furthermore 0.1 - 97% by weight of one or more polyglycol ethers and / or their esters with boric acid. 2. A hydraulic fluid according to claim 1 The method of claim 1, comprising 0.005-0.08% by weight of component (a). PL 197 796 B1 3. The brake fluid according to claim 1 The process of claim 1 or 2, wherein component (a) is the sole triazole-based corrosion inhibitor. 4. The brake fluid according to claim 1 A method as claimed in claim 1 or 2, characterized in that it contains as component (b) 0.001 - 0.5% by weight of one or more compounds from the group consisting of benzimidazole, hydrogenated 1H-1,2,3-tolutriazole, 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 additional corrosion inhibitors other than (a). The brake fluid according to claim 1 The process of claim 1 or 2, further comprising, in addition to components (a) and optionally (b), 0.1-50% by weight of one or more polyglycols.