NL8204031A - METHOD FOR REDUCING THE BRAKE SOUND IN DISC BRAKED IN OIL. - Google Patents

Description

, N.O. 31419 1

Method for reducing the brake noise for disc brakes immersed in oil_

The invention relates to lubricating oil compositions, in particular lubricating oil compositions, which are useful as functional fluids in coupling, hydraulic fluids and / or lubrication of systems demanding relative moving parts. More particularly, the invention relates to functional fluids for use in lubricating heavy machinery, especially high output tractors, and to reduce brake noise therein.

The use of heavy machinery, such as a tractor, increases the demand for lubricant compositions with very good utilization properties. Mbderne tractors have many powered parts, such as power steering and power brakes. Power brakes are preferably disc type because they have a greater braking capacity. The preferred disc brakes are wet-type brakes immersed in a lubricant and therefore sealed from sludge and dirt.

Such brakes, however, suffer from at least one problem, namely the grinding or screaming of the brakes. This phenomenon is a very unpleasant noise that occurs when you slow down. In the past, friction modifiers, such as dioleyl hydrogen phosphite, have been added to the brake lubricant composition to reduce the cutting edge. Lubricant compositions containing this additive tend to be crushed very quickly, especially at high temperatures.

A further complicatle in eliminating the braking of the brakes is the desire to use the same functional fluid not only for lubricating the brakes, but also for lubricating other tractor parts, such as the hydraulic and mechanical power take-offs, the gearbox , intermediate gears and armies of the tractor and the like. The functional fluid must act as a lubricant, a power transfer agent and as a heat transfer medium. It is possible to obtain a composite fluid which satisfies all these needs without the braking of the brakes.

U.S. Patent No. 3,151,077 teaches the use of borated monoacylated trimethylol alkanes as engine fuel and lubricating oil additives. These additives are said to reduce the occurrence of surface ignition in an internal combustion engine and prevent accumulation of carburettor deposits.

U.S. Patent No. 2,795,548 describes the use of lubricating oil compositions containing borated 1,2-alkanediol. The oil compositions are used in the crankcase of an internal combustion engine to reduce the oxidation of the oil and corrosion of the metal parts of the engine.

According to the invention, it has now been found that oil-soluble borated 1,2-alkanediol of the formula 1, wherein R is an alkyl group of 8 to 28 carbon atoms, function as suitable friction modifiers which, when added to a lubricating oil, provide good shavings exhibit antagonistic properties.

More particularly, the invention relates to a method of reducing the cutting edge when braking between oil-immersed disc brakes by lubricating the contacting surfaces of the brakes with a composition of a predominant amount a lubricating oil which contains an effective amount for cutting the cutting of a borated 1,2-alkanediol of the formula 1.

The borated alkane-1,2-diols of the formula I to be used in the invention are compounds containing 10 to 30, preferably 10 to 20, carbon atoms. A single compound defined by the number of carbon atoms can be used, such as borated decane-1,2-diol, borated octadecane-1,2-diol, borated eicosane-1,2-diol, borated tricontane-1,2-diol and the like, however, a mixture of several compounds with different number of carbon atoms is preferred. Typical mixtures include the borated 1,2-diols of alkanes with 10 to 30 carbon atoms, the borated 1,2-diols of alkanes with 12, 14, 16, 18 and 20 carbon atoms, the borated 1,2-diols of alkanes with 15 up to 20 carbon atoms, the borated 1,2-diols of alkanes with 15 to 18 carbon atoms, the borated 1,2-diols of alkanes with 20 to 24 carbon atoms, the borated 1,2-diols of alkanes with 24, 26 and 28 carbon atoms and the like.

The long chain borated 1,2-alkanediol diols are prepared by borating a long chain 1,2-alkanediol of the formula II, wherein R is as defined above, with a stoichiometric amount of boric acid to remove the reaction. -tie water by azeotropic distillation. The reaction is believed to proceed according to the scheme of the figure, wherein R is an alkyl group 40 having 8 to 28 carbon atoms.

8204031 '4 3

The reaction can be carried out at a temperature in the range 60 ° C to 135 ° C in the presence of any suitable organic solvent, such as methanol, benzene, xylenes, toluene, neutral oil and the like. If the solvent does not form an azeotrope with water, a sufficient amount of an azeotrope-forming agent is taken up to remove the water as an azeotrope.

The diols used for the invention are commercially available or are prepared in a simple manner from the corresponding α-olefin by methods well known in the art. For example, the olefin is first reacted with a peracid, such as peracetic acid, or hydrogen peroxide plus formic acid, to form a 1,2-epoxyalkane, which is readily hydrolyzed to alkane-1,2- under acid or base catalysis. diol. According to another method, the olefin is first halogenated to a 1,2-dihaloalkane, which is then hydrolyzed to an alkane-1,2-diol by reacting first with sodium acetate and then with sodium hydroxide.

α-Alkenes are obtained by thermal cracking of waxes. This process produces olefins with all numbers of carbon atoms. α-olefins with an even number of carbon atoms are prepared according to the commonly known ethylene "fouling" reaction. Olefins obtained by Sen from these methods have essentially a linear structure with little or no branching. Linear olefins are the preferred olefins for conversion to alkane 1,2-diols.

The lubricant compositions used in the process of the invention contain a major amount of a lubricating oil and about 0.1 to 5.0% by weight of the borated 1,2-alkanediol of the formula 1, preferably 0, 5 to 2% by weight, based on the weight of the total composition. The optimum amount of a borated 1,2-alkanediol within these limits will vary slightly depending on the base oil and other additives present in the oil.

Additive concentrates are also within the scope of the invention. In the addition concentrate form, the borated 1,2-alkanediol is present in a concentration of 5 to 50% by weight.

The lubricant compositions are prepared by mixing the appropriate amount of the desired borated 1,2-alkanediol with the lubricating oil using conventional techniques. When concentrates are prepared, the amount of lubricating oil is limited, but to a sufficient amount to dissolve the required amount of 1,2-alkanediol-40-diol diol. Generally, the concentrate 8204031 * 4 will contain a sufficient amount of borated 1,2-alkanediol to allow subsequent dilution with further lubricating oil in a 1- to 10-fold amount.

The lubricating oil, which can be used in the practice of the present invention, contains very different hydrocarbon oils of synthetic or natural origin, such as naphthenic, paraffinic and mixed base oils, such as are obtained in the refining of crude oil. Other lubricating oils obtained from slate oil, tar sands or coal are also useful. The lubricating oils can be used individually or mixed, as far as miscible. The lubricating oils generally have a viscosity of 50 to 5000 SUS (Saybolt Universal Seconds) and usually from 100 to 1500 SUS at 37.8 ° C. preferred ones have an SAE number in the range of 10 to 40 and have a paraffinic structure.

In some tractor systems, where the brake fluid is kept in a separate oil container, the hydrocarbon oil and borated 1,2-alkanediol composition of the invention is a sufficient lubricant and can be used as such. In the more common tractor systems, which have a common oil tray for all functional fluids, for example, gearbox lubricant, hydraulic flux and the like, the lubricating oil is mixed with a range of additives. These additives include anti-oxidants, detergents, dispersants, anti-rust agents, foam inhibitors, corrosion inhibitors, anti-wear agents, viscosity index improvers (VI), friction control agents, elastomeric swelling agents, extreme pressures ( EP) additives, pour point depressants and metal deactivators. All these additives are generally known in the lubricating oil field.

The additives, which may preferably be added to the lubricating oils to which the borated 1,2-alkanediol of the formula I are added, are the oil-soluble detergents such as the alkali or alkaline earth metal hydrocarbon sulfonates, or the alkali metal or alkaline earth metal phenolates or mixtures thereof, extremes of pressure additives, such as the Group II dihydrocarbon dithiophosphate salts, and dispersants, such as the alkenyl succinimides or succinates or mixtures thereof.

The alkali metal or alkaline earth metal hydrocarbon sulfonates can be either petroleum sulfonates, synthetic alkylated aromatic sulfonates or aliphatic sulfonates, such as those obtained from poly-40 isobutylene. One of the main functions of the 8204031 sulfonates is to act as a detergent and dispersant. These sulfides are well known in the art. The hydrocarbon residue must have a sufficient number of carbon atoms to make the sulfonate molecule soluble in all. Preferably, the hydrocarbon moiety has at least 20 carbon atoms and can be aromatic or aliphatic, although it usually has an alkyl aromatic structure.

Particularly preferred for use are calcium, magnesium or barium sulfonates, which have an aromatic character.

Certain sulfonates are usually prepared by sulfonation of a petroleum fraction with aromatic groups, usually mono- or dialkyl-benzene groups, followed by forming the metal salt of the sulfonic acid material. Other starting materials used to prepare these sulfonates are synthetic alkylated benzenes and aliphatic hydrocarbons prepared by polymerization of an olefin or alkadides, for example, a polyisobutenyl group, prepared by polymerization of isobutylene. The metal salts are formed directly or by double conversion according to well known methods.

The sulfonates can be neutral or overbased with base numbers up to about 400 or more. Carbon dioxide is the most commonly used material for preparing the basic or overbased sulfonates.

Mixtures of neutral and overbased sulfonates can be used. The neutral sulfonates are usually used in an amount to provide 5 to 25 mmol sulfonate per kilogram of the total composition. Preferably, the neutral sulfonates are present in an amount of 10 to 20 mmoles per kilogram of the total composition, and the excess base sulfonates are present in an amount of 50 to 200 mmoles per kilogram of the total composition.

The phenolates for use in the invention are the usual products which are the alkali or alkaline earth metal salts of alkylated phenols. Vanη of the functions of the phenolates is to act as a detergent and dispersant. The phenols can be singly or multiply alkylated.

The alkyl portion of the alkyl phenolate is present to impart to the phenolate oil solubility. The alkyl portion can be obtained from naturally occurring or synthetic sources. Naturally occurring sources include petroleum hydrocarbons, such as white oil and wax. The hydrocarbon portion, in that it is derived from petroleum, is a mixture of various hydrocarbon residues, the specific composition of which depends on the particular 8204031 6 '' oil material which has been used as the raw material. Suitable synthetic sources include various commercially available olefins and alkane derivatives which, when reacted with the phenol, provide an alkyl phenol. Suitable residues obtained are butyl, hexyl, octyl, decyl, dodecyl, hexadecyl, eicosyl, tricontyl groups and the like. Other suitable synthetic sources of the alkyl groups are olefin polymers such as polypropylene, polybutene, polyisobutylene and the like.

The alkyl group may be straight or branched chain and may be saturated or unsaturated (if unsaturated, it preferably contains no more than 2 and generally no more than 1 site of olefinic unsaturation). The alkyl groups will generally contain 4 to 30 carbon atoms. When the phenol is substituted by έέη alkyl group, the alkyl group should generally contain at least 8 carbon atoms. The phenolate can be sulfurated if desired. It can be either neutral or overbased and, if overbased, it will have a base number of up to 200 to 300 or more. Mixtures of neutral and overbased phenolates can be used.

The phenolates are usually present in the oil in an amount such that they provide 10 to 60 mmoles of phenolate per kilogram of the total composition. Preferably, the neutral phenolates are present in 20 to 50 mmol per kilogram of the total composition and the overbased phenolates are present in 50 to 200 mmol per kilogram of the total composition. As metals, calcium, magnesium, strontium or barium are preferred.

The sulfurized alkaline earth metal alkyl phenolates can also be used. These salts are obtained by various methods, such as treatment of the neutralization product of an alkaline earth metal base and an alkyl phenol with sulfur. Suitably, the sulfur is added in elemental form to the neutralization product and reacted at elevated temperatures to form the sulfurized alkaline earth metal alkyl phenolate.

If more alkaline earth metal base is added during the neutralization reaction than is necessary to neutralize the phenol, a basic sulfurized alkaline earth metal alkyl phenolate is obtained. See, for example, the process described in U.S. Patent No. 2,680,096. Additional basicity can be obtained by adding carbon dioxide to the basic sulfurized alkaline earth metal alkyl phenolate. The excess alkaline earth metal base can be added after the sulfuring step, but is suitably added at the same time as the alkaline earth metal base to neutralize the phenol. 8204031 * 7.

Carbon dioxide is the most commonly used material for preparing the basic or "overbased" phenolates. A method of preparing basic sulfurized alkaline earth metal alkyl phenolates by the addition of carbon dioxide is described in U.S. Patent No. 3,178,368.

The salts of dihydrocarbon dithiophosphoric acid and Group II metal exhibit degradation and oxidation inhibiting and thermally stabilizing properties. The salts of dithiophosphoric acids and Group II 10 metals have been previously described. See, for example, U.S. Patent No. 3,390,080, columns 6 and 7, which generally describe these compounds and their preparation. Suitably, the salts of the Group II dihydrocarbon dithiophosphoric acids and metal useful in the lubricating oil composition of the invention contain from about 4 to about 12 carbon atoms in each of the hydrocarbon radicals, which may be yellow or different and which are aromatic. may be any of the aromatic, alkyl, or cycloalkyl groups. Preferred hydrocarbon radicals are alkyl groups of 4 to 8 carbon atoms, such as, for example, butyl, isobutyl, sec-butyl, hexyl, isohexyl, octyl, 2-ethylhexyl groups and the like. The metals suitable for forming these salts are barium, calcium, strontium, zinc and cadmium, of which zinc is preferred.

Preferably, the salt of a dihydrocarbon ditiophosphoric acid and a Group II metal corresponds to the formula 3, wherein R 1 and R 3 each independently represent hydrocarbon radicals, as described above, and represents a Group II metal cation, as above described.

The dithiophosphoric acid salts are present in the lubricating oil composition in an effective amount to prevent degradation and oxidation of the lubricating oil. Preferably, the amount is from about 3 to 30 mmole dithlophosphoric acid salt per kilogram of the total composition.

In particular, it is preferred that the salt be present in an amount of about 15 to 20 mmoles per kilogram of the total lubricating oil composition.

The alkenyl succinimide or succinate or mixture thereof is present, inter alia, to act as a dispersant and to prevent the formation of deposits. The alkenyl succinimides and succinates are well known in the art. The alkenyl succimides are the reaction product of a polyolefin polymer substituted succinic anhydride with an amine, preferably a polyalkylene polyamine, and the reaction alkenyl succinates are the reaction product of a polyolefin polymer substituted with succinic anhydride, polyhydric anhydride , phenols and naphthols, preferably a polyhydric alcohol containing at least three hydroxyl groups. The succinic anhydrides substituted by polyolefin-5 polymer are obtained by reacting a polyolefin polymer or derivative thereof with maleic anhydride. The succinic anhydride thus obtained is reacted with the amine or hydroxy compound. The calculation of the alkenylsuecin imides has been described in many places in the literature. For example, U.S. Pat. Nos. 3,390,082, 3,219,666, and 3,172,892, the disclosure of which is considered to be incorporated by reference. The calculation of the alkenyl succinates has also been described in the literature. Zle, for example, U.S. Patent Nos. 3,381,022 and 3,522,179, the disclosure of which is incorporated herein by reference.

Particularly good results can be obtained with the lubricating oil compositions of the invention if the alkenyl succinimide or succinate is a polylsobutylene-substituted succinic anhydride of a polyalkylene polyamine or polyhydric alcohol, respectively.

The polylsobutene, which is used to prepare the polyisobutylene substituted succinic anhydride, is obtained by polymerization of isobutene and can vary widely in its compositions. The average number of 25 carbon atoms can vary from 30 or less to 250 or more, with consequent average molecular weight to the number of about 400 or less to 3000 or more. Preferably, the average number of carbon atoms per polyisobutylene molecule will range from about 50 to about 100, with the polyisobutenes having an average molecular weight by number from about 600 to about 1500. The average number of carbon atoms per polyisobutylene molecule is in particular about 60 to about 90 at an average molecular weight to the number of about 800 to 1300. The polylsobutene is reacted with maleic anhydride by well known methods to form the succinic anhydride substituted by polylsobutylene.

In the preparation of the alkenyl succinimide, the substituted succinic anhydride is reacted with a polyalkylene polyamine to form the corresponding succinimide. Each alkylene group 40 of the polyalkylene polyamine usually has up to about 8 carbon 8204031 9 atoms. The number of alkylene groups can vary up to about 8. The alkylene group is, for example, an ethylene, propylene, butylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, octamethylene group, etc. The number of amino groups in general, although not necessarily, is more than the number of alkylene groups present in the amine, that is, if the polyalkylene polyamine contains 3 alkylene groups, it will usually contain 4 amino groups. The number of amino groups can range up to about 9. Preferably, the alkylene group contains about 2 to about 4 carbon atoms and all amino groups are primary or secondary. In this case, the number of amino groups έέη will be more than the number of alkylene groups. Preferably, the polyalkylene polyamine contains 3 to 5 amino groups. Specific examples of the polyalkylene polyamines are ethylene diamine, diethylene triamine, triethylene tetramine, propylenediamine, tripropylene tetramine, tetraethylene pentamine, trimethylene diamine, pentaethylene hexamine, di (trimethylene) triamine, ethylene, hexamethylene

Other suitable amines for the preparation of the alkenylsuccinimide to be used in the invention are the cyclic amines such as piperazine, morpholine and diplperazines.

Preferably, the alkyl succinimides which can be used in the compositions of the invention correspond to the formula 4 wherein a. R] represents an alkenyl group, preferably a substantially saturated hydrocarbon residue prepared by polymerization of aliphatic monoalkenes. Preferably, it is prepared from isobutene and R 1 has an average number of carbon atoms and an average molecular weight by number as described above; b. the "alkylene" radical mainly represents a hydrocarbon radical having at most 8 carbon atoms and preferably about 2-4 carbon atoms, as described above; c. A represents a hydrocarbon residue, an amine-substituted hydrocarbon residue or hydrogen. The hydrocarbon radical and the amine-substituted hydrocarbon radicals are the alkyl and amino-substituted alkyl analogs of the above-described alkylene groups. Preferably A represents hydrogen; d. n indicates an integer from about 1 to 10 and preferably from about 3 to 5.

The alkenyl succinimide can be reacted with boric acid or a similar boron 40-containing compound to form the borated 82 0 4 0 31 10 dispersants which can be used in the invention. The borated succinimides are intended to be included within the scope of the term "alkenyl succinimide".

The alkenyl succinates are the reaction products of the above-described succinic anhydride with hydroxy compounds, which may be aliphatic compounds, such as monovalent or polyvalent alcohols, or aromatic compounds, such as phenols and naphthols. The aromatic hydroxy compounds from which the esters can be derived are exemplified by the following 10 specific examples: phenol, S-naphthol, α-naphthol, cresol, resorcinol, catechol, ρ, ρ'- dihydroxybiphenyl, 2-chlorophenol, 2,4-dibutylphenol, phenol substituted by propylene tetramer, didodecylphenol, 4,4'-methylene bis-phenol, α-decyl-0-naphthol, phenol substituted by polyisobutene (molecular weight 1000), the condensation product of heptylphenol with 0.5 mol of formaldehyde, the condensation product of octylphenol with acetone, di- (hydroxyphenyl) oxide, di- (hydroxyphenyl) sulfide, dl- (hydroxyphenyl) disulfide and 4-cyclohexylphenol. Phenol and alkylated phenols with up to three alkyl substituents are preferred. Each of the alkyl substituents can contain 100 carbon atoms or more.

The alcohols from which the esters can be derived preferably contain at most about 40 aliphatic carbon atoms. They can be monovalent alcohols, such as methanol, ethanol, isooctanol, dead canol, cyclohexanol, cyclopentanol, behenyl alcohol, hexatriacontanol, neopentyl alcohol, isobutyl alcohol, benzyl alcohol, S-phenylethyl alcohol, 2-methylcyclohexanol, β-chloroethanol, mon-ethyl alcohol, monobutyl ether of ethylene glycol, monopropyl ether of diethylene glycol, monododecyl ether of triethylene glycol, monooleate of ethylene glycol, monostearate of diethylene glycol, sec.pentyl alcohol, tert-butyl alcohol, 5-bromododecanol, nitrool octadecanol. The polyhydric alcohols preferably contain from 2 to about 10 hydroxyl groups. They are exemplified, for example, by ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, dibutylene glycol, tributylene glycol, and other alkylene glycols, wherein the alkylene group contains from 2 to about 8 carbon atoms. Other useful polyhydric alcohols include glycerol, glycerol monooleate, glycerol monomethyl ether, pentaerythritol, 9,10-dihydroxystearic acid, methyl 9,10-dihydroxystearic acid, 1,2-butanediol, 2,3-hexane-diol, 2 4-hexanediol, pinacol, erythritol, arabitol, sorbitol, mannitol, 1,2-cyclohexanediol and xylene glycol. Carbohydrates, such as sugars, starches, celluloses, etc. can similarly provide esters.

As carbohydrates, for example, glucose, fructose, sucrose, rhamnose, mannose, glyceraldehyde and bile lactose can be mentioned.

A particularly preferred group of polyhydric alcohols are the alcohols having at least three hydroxyl groups, some of which are esterified with a monocarboxylic acid having about 8 to about 30 carbon atoms, such as octanoic acid, oleic acid, stearic acid, 11- nolic acid, dodecanoic acid or tall oil acid. Examples of such pearl esterified polyhydric alcohols are the monooleate of sorbi-tol, dl stearate of sorbitol, monooleate of glycerol, monostearate of glycerol, dl-dodecanoate of erythritol.

The esters can also be derived from unsaturated alcohols such as allyl alcohol, cinnamon alcohol, propargyl alcohol, 1-cyclohex-en-3-ol and oleyl alcohol. Still other groups of the alcohols capable of providing the esters of the invention include the etheralcohols and aminoalcohols such as, for example, the oxyalkylene, oxyaryylene, aminoalkylene and aminoaryylene groups substituted alcohols with one or more oxyalkylene, aminoalkylene, aminoarylene or oxyaryl groups. Examples of these are Cellosolve, 20 carbitol, phenoxyethanol, heptylphenyl- (oxypropylene) gH, octyl- (oxy-ethylene) 3 ° “H, phenyl- (oxyoctylene) 2” H, substituted by (heptyl-phenyl-oxypropylene) glycerol, polyepoxystyrene , aminoethanol, 3-aminoethyl-pentahol, di- (hydroxyethyl) -amine, p-aminophenol, tri- (hydroxypropyl) -amine, N-hydroxyethyl ethylene diamine, Ν, Ν, Ν ', N'-te-trahydroxytrlmethylenediamine and of such. For the most part, the ether alcohols having up to about 150 oxyalkylene groups are preferred, with the alkylene group containing 1 to about 8 carbon atoms.

The esters can be diesters of succinic or acid esters, ie partially esterified succinic acids, as well as partially esterified polyhydric alcohols or phenols, namely esters with free alcoholic or phenolic hydroxyl groups. Mixtures of the above-mentioned esters are also considered to be within the scope of the invention.

The alkenyl succinates can be reacted with boric acid or a similar boron-containing compound to form borated dispersants which can be used in this invention. Such borated succinates are described in U.S. Patent No. 3,533,945, the disclosure of which is incorporated herein by reference. The borated succinates are 8204031> v.

12 deemed to fall within the scope of the term "alkenyl succinate".

The alkenyl succinimides and accinates are present in the lubricating oil compositions in an effective amount to act as a dispersant and prevent the deposition of contaminants contaminated in the oil. The amount of alkenyl succinimides and accinates may range from about 0.5% to about 20% by weight of the total lubricating oil composition. The amount of alkenyl succinimide or succinate which may be present in the lubricating oil composition preferably ranges from about 2 to about 5% by weight of the total composition.

The finished lubricating oil can be "single" or "multigrade". Multigrade lubricating oils are prepared by adding viscosity index (VI) improving parts. Typical examples of viscosity index improvers are polyalkyl methacrylates, ethylene propylene copolymers, styrene diene copolymers and the like. So-called decorated VI enhancing moieties with both viscosity index enhancing and dispersing properties are also suitable for use in the compositions of the invention.

The following examples are given to illustrate the invention in a specific manner. These examples and explanations should not be construed as any limitation on the scope of the invention.

Example I

Into a five liter reaction flask were charged 1050 g (4 moles) of C 1-5 5-8 alkane-1,2-diol, 272 g (4.4 moles) boric acid and 1550 g 25 xylene. The reaction mixture was stirred and refluxed for 90 hours. At the end of this period, 191 ml of water had been collected. The reaction mixture was cooled and filtered, then the solvent was removed in vacuo to yield 1158g of product containing 6.3% boron.

Example II

The compositions of the invention were tested in a laboratory test. The test was performed on an SAE No. 2 friction machine, which was modified by adding a moderate speed hydraulic motor drive. The test piece was a layered composite of gesη sintered bronze plate obtained from General Metalls Powder Co. 1500 mixture, between two steel plates as spacers, arranged in the above-mentioned device. Then the test liquid, about 300 g, was placed in the test oil tray. The hydraulic drive rotated the 40 test pieces at 100 rpm. A piston-like brake was applied with a contact pressure of 0.52 MPa. The braking torque was measured using the SAE No 2 load cell and the revolution speed in rpm was measured using an electric tachometer. An X-Y tracing was used to plot the 5 torque as a function of rpm, while the hydraulic drive was slowly controlled to reduce the speed to 0 rpm. The behavior of a fluid with regard to the braking of brakes is related to the slope of the friction velocity curve. The slope of the curve is found by measuring the slope of an 11 µm, which is drawn by drawing the point 50 rpm on the curve and the highest point on the curve below 50 rpm. As the slope of this curve becomes increasingly negativ, the chirping sound of the brake becomes louder. This inclination correlates with brake noise tests on a full-scale tractor.

The test described above is performed for three hydraulic fluids for mineral olle tractors. The results for these liquids are shown in Table A. Composition A was a base oil without a friction modifier, and composition δ additionally contained 1% borated alkanediol of Example I. Composition C is a commercially available tractor hydraulic fluid. As shown in Table A, the addition of borated 1,2-alkanediol (fluid B) to the base fluid (A) increased the slope, indicating that it is effective in reducing the braking of the brakes. Table A also shows the slope obtained with a commercially available tractor hydraulic fluid.

TABLE A

Effect of borated 1,2-alkanediol in a laboratory simulation test on the braking of the brakes

Composition Slope of Friction Rapid Hero Curve A - base oil 0.0131 B - base oil + 1 wt% borated 1,2-alkanediol of Example I 0.0086 C - commercially available preparation 0.0143 8204031

Claims (6)

Lubricating oil composition prepared for use in a tractor and contacting the surfaces of oil-immersed disc brakes, characterized in that in the prepared oil about 0.1 to 5 about 5% by weight of a borated 1.2 -alkanediol of the formula 1, wherein R is an alkyl group having 8 to 28 carbon atoms, or a mixture thereof. Lubricating oil composition according to claim 1, characterized in that R is an alkyl group with 8 to 18 carbon atoms. Lubricating oil composition according to claim 1 or 2, characterized in that the borated 1,2-alkanediol is a mixture of borated 1,2-diols containing 15 to 18 carbon atoms. 4. A method of reducing the grinding of oil-immersed disc brakes by lubricating the contacting surfaces of oil-immersed disc brakes, characterized in that the lubrication is carried out with a composition of a lubricating oil, which about 0.1 to about 5% by weight of a borated 1,2-alkanediol of the formula 1, wherein R is an alkyl group having 8 to 28 carbon atoms, or mixtures thereof. Process according to claim 4, characterized in that R is an alkyl group with 8 to 18 carbon atoms. Process according to claim 4 or 5, characterized in that the borated 1,2-alkanediol is a mixture of borated 1,2-diols containing 15 to 18 carbon atoms. 25. ii I 1 Η-1 IIH4 8204031