SE456743B - APPLICATION OF A LUBRICANE OIL COMPOSITION CONTAINING A DRILLED FAT ACID ESTER OF GLYCEROL TO REDUCE OIL FROM OIL LOWER DISC BRAKES - Google Patents

Description

15' ZÛ 25 30 35 40 456 743 2 -ï esters act as suitable friction modifiers which, when added to a lubricating oil, exhibit good anti-noise properties.

More particularly, the present invention relates to the use of a composition comprising a lubricating oil containing from 0.1 to 5 weight percent of a borated fatty acid ester of glycerol to reduce oil-immersed disc brake noise by lubricating the contact surfaces of oil-immersed disc brakes with the composition.

The borated fatty acid esters of glycerol are prepared by borating a fatty acid ester of glycerol with boric acid with removal of the water of reaction. Preferably, sufficient boron is present so that each boron will react with from 1.5 to 2.5 hydroxyl groups present in the reaction mixture.

The reaction can be carried out at a temperature in the range of 60 to 135°C, in the absence or presence of any suitable organic solvent, such as methanol, benzene, xylenes, toluene, neutral oil and the like.

Fatty acid esters of glycerol can be prepared by a variety of methods well known in the art. Many of these esters, such as glycerol monooleate and glycerol tallow ester, are manufactured on a commercial scale. The esters useful in the present invention are oil-soluble and are conveniently prepared from C8 to C22 fatty acids or mixtures thereof, such as those found in natural products. The fatty acid may be saturated or unsaturated.

Certain compounds found in acids from natural sources may include _licanic acid, which contains a keto group. Most suitable C8 to C22 fatty acids are those of the formula R-COOH, wherein R is alkyl or alkenyl.

The fatty acid monoester of glycerol is suitable, however mixtures of mono- and diesters may be used. Preferably each mixture of mono- and diesters contains at least 40% of the monoester.

Most suitably, mixtures of mono- and diesters of glycerol contain from 40 to 60% by weight of the monoester. For example, commercial glycerol monooleate contains a mixture of from 45 to 55% by weight of monoester and from 55 to 45% diester.

Suitable fatty acids are oleic acid, stearic acid, palmitic acid, myristic acid, palmitoleic acid, linoleic acid, lauric acid, linolenic acid and eleostearic acid, and the acids from the natural products linseed, palm oil, olive oil, peanut oil, corn oil, safflower oil and the like.

A particularly suitable acid is oleic acid.

The lubricating compositions used in the process of the present invention contain a major portion of a lubricating oil and from about 0.1 to 5.0 weight percent of the borated fatty acid ester of glycerol, preferably from 0.5 to 2 weight percent based on the weight of the total composition. The optimum amount of a borated fatty acid ester of glycerol within these ranges will vary slightly depending on the base oil and other additives present in the oil.

Additive concentrates are also included within the scope of the present invention. In the form of additive concentrates, the borated fatty acid ester of glycerol is present in a concentration ranging from 5 to 50 weight percent.

The lubricating compositions are prepared by mixing, using conventional methods, the appropriate amount of the desired borated fatty acid ester of glycerol with the lubricating oil.

When concentrates are prepared, the amount of lubricating oil is limited, but is sufficient to dissolve the required amount of borated fatty acid ester of glycerol. Typically, the concentrate will have sufficient borated fatty acid ester of glycerol to permit subsequent dilution with 1- to 10-fold lubricating oil.

The lubricating oil which can be used in the practice of the present invention includes a wide variety of hydrocarbon oils derived from synthetic or natural sources, such as naphthenic base, paraffinic base and blended base oils such as those obtained from the refining of crude oil. Other lubricating oils derived from shale oil, tar sands or coal are also useful. The lubricating oils can be used individually or in combination whenever they are miscible. The lubricating oils usually have a viscosity ranging from 50 to 5000 SUS (Saybolt Universal Seconds), and usually from 100 to 1500 SUS at 3700. The suitable oils have an SAE classification in the range of 10 to 40 and are paraffinic in structure.

In some tractor systems in which the brake fluid is kept in a separate container, the hydrocarbon oil/borated fatty acid ester of glycerol composition of the present invention is a sufficient lubricant and can be used as such. However, in the more common tractor systems in which there is a common container for all functional fluids, e.g., transmission lubricant, hydraulic fluid, and the like, the lubricating oil is mixed with a variety of additives. These additives include antioxidants, detergents, dispersants, rust inhibitors, foam inhibitors, corrosion inhibitors, anti-wear agents, viscosity index (VI) improvers, friction control agents, elastomer swelling agents, extreme pressure (EP) agents, pour point depressants, and metal deactivators. All of these additives are well known in lubricating oil technology.

The suitable additives which can be added to the lubricating oils to which the borated fatty acid esters of glycerol are added are the oil-soluble detergents, such as alkali or alkaline earth metal hydrogencarbyl sulfonates, or alkali or alkaline earth metal phenolates, or mixtures thereof, extreme pressure additives, such as metal salt-ur-group-II dihydrocarbyl thiophosphates, and dispersants, such as alkenyl succinimides or succinates or mixtures thereof.

Alkali or alkaline earth metal hydrocarbyl sulfonates can be either petroleum sulfonates, synthetically alkylated aromatic sulfonates, or aliphatic sulfonates, such as those derived from polyisobutylene. One of the more important functions of the sulfonates is to act as a detergent and dispersant.

These sulfonates are well known in the art. The hydrocarbyl group must have a sufficient number of carbon atoms to render the sulfonate molecule oil-soluble. Preferably, the hydrocarbyl moiety has at least 20 carbon atoms and may be aromatic or aliphatic, but is usually alkylaromatic. Most suitable for use are calcium, magnesium or barium sulfonates, which are aromatic in character.

Some sulfonates are typically prepared by sulfonating a petroleum fraction with aromatic groups, usually mono- or dialkylbenzene groups, and then forming the metal salt of the sulfonic acid material. Other feedstocks used to prepare these sulfonates include synthetic alkylated benzenes and aliphatic hydrocarbons prepared by polymerizing a mono- or diolefin, e.g., a polyisobutenyl group prepared by polymerizing isobutene. Metal salts are formed directly or by metathesis using well-known procedures.

The sulfonates may be neutral or overbased with base numbers up to about 400 or more. Carbon dioxide is the most commonly used material to generate the basic or overbased sulfonates. Mixtures of neutral and overbased sulfonates may be used. The neutral sulfonates are typically used to provide from 5 to 25 mg of sulfonate per kg of the total composition. Suitably, the neutral sulfonates are present in from 10 to 20 mmol per kg of the total composition and the overbased sulfonates are present in from 50 to 200 mmol per kg of the total composition.

The phenolates for use in this invention are the conventional products which are alkali or alkaline earth metal salts of alkylated phenols. One of the functions of the phenolates is to act as a detergent and dispersant. The phenols may be mono- or polyalkylated.

The alkyl moiety of the alkyl phenolate is present to impart oil solubility to the phenolate. The alkyl moiety may be obtained from naturally occurring or synthetic sources. Naturally occurring sources include petroleum hydrocarbons, such as white oil and wax. When derived from petroleum, the hydrocarbon moiety is a mixture of various hydrocarbyl groups, the specific composition of which depends on the particular oil material used as the starting material. Suitable synthetic sources include various commercially available alkenes and alkane derivatives which, when reacted with phenol, yield an alkyl phenol. Suitable radicals obtained include butyl, hexyl, octyl, decyl, dodecyl, hexadecyl, eicosyl, tricontyl and the like. Other suitable synthetic sources of the alkyl radical include olefin polymers, such as polypropylene, polybutene; polyisobutene and the like.

The alkyl group may be straight chain or branched chain, saturated or unsaturated (if unsaturated, it suitably contains no more than 2 and usually no more than 1 site of olefinic unsaturation).

The alkyl radicals will usually contain from 4 to 30 carbon atoms. Usually, when the phenol is monoalkyl substituted, the alkyl radical will contain at least 8 carbon atoms. The phenolate will be sulfurized if desired. It may be either neutral or overbased and if overbased it will have a base number of up to 200 to 700 or more. Mixtures of neutral and overbased phenolates may be used.

The phenolates are present in the oil to provide from 10 to 60 mmol of phenolate per kg of the total composition. Suitably, the natural phenolates are present from 20 to 50 mmol per kg of the total composition and the overbased phenolates are present from 50 to 200 mmol per kg of the total composition. Suitable metals are calcium, magnesium, strontium or barium.

The sulfurized alkaline earth metal alkyl phenolates can also be used. These salts are obtained by a variety of processes, such as by treating the neutralization product of an iodoalkali metal base and an alkyl phenol with sulfur. Typically, the sulfur is added in elemental form to the neutralization product and reacted at elevated temperatures to produce the sulfurized alkaline earth metal alkyl phenolate. If more alkaline earth metal base is added during the neutralization reaction than was necessary to neutralize the phenol, a basic sulfurized alkaline earth metal alkyl phenolate is obtained, for example, the process of Walker et al., 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. Excess alkaline earth metal base can be added subsequently to the sulfurization step but is usually added at the same time as the alkaline earth metal base is added to neutralize the phenol. Carbon dioxide is the most commonly used material to produce the basic or "overbased" phenolates. A process in which basic sulfurized alkaline earth metal alkyl phenolates are produced by adding carbon dioxide is shown in Hanneman, U.S. Patent No. 3,178,368.

Group II metal salts of dihydrocarbyldithiophosphoric acids exhibit anti-wear, antioxidant and thermal stability properties.

Group II metal salts of phosphorodithioic acids have been described previously. See, for example, U.S. Patent No. 3,390,080, columns 6 and 7, wherein these compounds and their preparation are generally described. Preferably, the Group II metal salts of dihydrocarbyldithiophosphoric acids useful in the lubricating oil composition of the present invention contain from about 4 to about 12 carbon atoms in each of the hydrocarbyl radicals and may be the same or different and may be aromatic, alkyl or cycloalkyl. Suitable hydrocarbyl groups are alkyl groups containing from 4 to 8 carbon atoms and are represented by butyl, isobutyl, sec-butyl, hexyl, isohexyl, octyl, 2-ethylhexyl and the like.

The metals suitable for forming these salts include barium, calcium, strontium, zinc and cadmium, of which zinc is preferred. 1.? r* _..- f? 10 15 20 25 30 35 456 743 Suitably, the Group II metal salt of a dihydrocarbyl dithiophosphoric acid has the following formula: [R2o\P/s / \ Rso sl-MZ 1 e. R2 and R3 each independently represent hydrocarbyl radicals, as described above, and wherein: f. M1 represents a metal cation from Group II as described above.

Dithiophosphoric acid salts are present in the lubricating oil composition in an amount effective to prevent wear and oxidation of the lubricating oil. Suitable amounts range from about 3 to 30 mmol of the dithiophosphoric acid salt per kg of the total composition.

Most suitably, the salt is present in an amount ranging from about 15 to 20 mmol per kg of the total lubricating oil composition.

Alkenyl succinimide or succinate or mixtures thereof are present to act, among other things, as a dispersant and to prevent the formation of deposits. The alkenyl succinimides and succinates are well known in the art. The alkenyl succinimides are the reaction product of a polyolefin polymer-substituted succinic anhydride with an amine, preferably a polyalkylene polyamine, and the alkenyl succinates are the reaction product of a polyolefin polymer-substituted succinic anhydride with monohydric or polyhydric alcohols, phenols and naphthols, preferably a polyhydric alcohol containing at least three hydroxy radicals. Polyolefin polymer-substituted succinic anhydrides are obtained by reacting a polyolefin polymer or a derivative thereof with maleic anhydride. The succinic anhydride thus obtained is reacted with the amine or hydroxy compound. The preparation of alkenyl succinimides has been described many times in the art. See, for example, U.S. Patents 3,390,082, 3,219,666, and 3,172,892. The preparation of alkenyl succinates has also been described in the art. See, for example, U.S. Patents 3,381,022 and 3,522,179.

Particularly good results can be obtained with the lubricating oil compositions of the present invention when the alkenyl succinimide or succinate is a polyisobutene-substituted succinic anhydride of a polyalkylene polyamine or polyhydric alcohol, respectively. 10 15 20 25 30 35 40 456 743 Polyisobutene, from which the polyisobutene-substituted succinic anhydride is obtained by polymerization of isobutene, can vary widely in composition. The average number of carbon atoms can be in the range of from 30 or less to 250 or more, with a resulting number average molecular weight of about 400 or less to 3000 or more. Preferably, the average number of carbon atoms per polyisobutene molecule will be in the range of from about 50 to about 100 with polyisobutenes having a number average molecular weight of about 600 to about 1500. More preferably, the average number of carbon atoms per polyisobutene molecule is in the range of from about 60 to about 90, and the number average molecular weight is in the range of from about 800 to 1300. The polyisobutene is reacted with maleic anhydride according to well known procedures to yield polyisobutene-substituted succinic anhydride.

In the preparation of alkenyl succinimide, the substituted succinic anhydride is reacted with a polyalkylene polyamine to yield the corresponding succinimide. Each alkylene radical of the polyalkylene polyamine typically has up to about 8 carbon atoms. The number of alkylene radicals can range from about 8 to about 8. The alkylene radical is exemplified by ethylene, propylene, butylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, octamethylene, etc. The number of amino groups is typically, but not necessarily, greater than the number of alkylene radicals present in the amine, i.e., if a polyalkylene polyamine contains 3 alkylene radicals, it will typically contain 4 amino radicals. The number of amino radicals can range up to about 9. Suitably, the alkylene radical contains from about 2 to about 4 carbon atoms and all amine groups are primary or secondary. In this case, the number of amine groups exceeds the number of alkylene groups by 1. Preferably, the polyalkylene polyamine contains from 3 to 5 amine groups. Specific examples of polyalkylene polyamines include ethylenediamine, diethylenetriamine, triethylenetetramine, propylenediamine, tripropylenetetramine, tetraethylenepentamine, trimethylenediamine, pentaethylenehexamine, di-(trimethylene)triamine, tri(hexamethylene)tetramine, etc.

Other amines suitable for preparing the alkenyl succinimide useful in the present invention include the cyclic amines, such as piperazine, morpholine, and dipiperizines. fn...

Preferably, the alkenyl succinimides which can be used in the compositions of the present invention have the following formula: 10 15 20 25 30 0 RfïH-Cšrläalkylene-N; H 1 mZ-cšo n wherein: a. R1 represents an alkenyl group, preferably a substantially saturated hydrocarbon, prepared by polymerizing aliphatic mono-olefins. Preferably, R1 is prepared from isobutene and has an average number of carbon atoms and a number average molecular weight as described above; A b. The "alkylene" radical preferably represents a hydrocarbyl group containing up to about 8 carbon atoms and which preferably contains from about 2-4 carbon atoms as described above; c. A represents a hydrocarbyl group, an amine-substituted hydrocarbyl group or hydrogen. The hydrocarbyl group and the amine-substituted hydrocarbyl groups are typically alkyl and amino-substituted alkyl analogs of the alkylene radicals described above. Suitably, A is hydrogen; d. n is an integer from about 1 to 10, and suitably from about 3-5.

The alkenyl succinimide can be reacted with boric acid or a similar boron-containing compound to form borated dispersants useful in the present invention. The borated succinimides are intended to be included within the scope of the term "alkenyl succinimide".

The alkenyl succinates are the above-described succinic anhydrides with hydroxy compounds, which may be aliphatic compounds, such as monohydric or polyhydric alcohols, or aromatic compounds, such as phenols and naphthols. The aromatic hydroxy compounds from which the esters may be derived are illustrated by the following specific examples: phenol, beta-naphthol, alpha-naphthol, cresol, resorcinol, catechol, p,p'-dihydroxybiphenyl, 2-chlorophenol, 2,4-dibutylphenol, propylene tetramer-substituted phenol, didodecylphenol, 4,4'-methylene bisphenol, alpha-decyl-beta-naphthol, polyisobutene (molecular weight 1000)-substituted phenol, the condensation product of heptylphenol with 0.5 moles of formaldehyde, the condensation product of octylphenol with acetone, di(hydroxyphenyl)oxide, di(hydroxyphenyl)sulfide, di(hydroxyphenyl)disulfide and 4-cyclohexylphenol.

Phenol and alkylated phenols with up to three alkyl substituents are suitable. Each of the alkyl substituents may contain 100 10 15 20 25 30 35 40 10 456 745 or more carbon atoms.

The alcohols from which the esters may be derived suitably contain up to about 40 aliphatic carbon atoms. They may be monohydric alcohols, such as methanol, ethanol, isooctanol, dodecanol, cyclohexanol, cyclopentanol, behenyl alcohol, hexatriacontanol, neopentyl alcohol, isobutyl alcohol, benzyl alcohol, betaphenylethyl alcohol, 2-methylcyclohexanol, betachloroethanol, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monopropyl ether, triethylene glycol monododecyl ether, ethylene glycol monooleate, diethylene glycol monostearate, sec-pentyl alcohol, tert-butyl alcohol, 5-bromododecanol, nitrooctadecanol and glycerol dioleate. Polyhydric alcohols suitably contain from 2 to about 10 hydroxy radicals. 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 in which the alkylene radical contains from 2 to about 8 carbon atoms. Other useful polyhydric alcohols include glycerol, glycerol monooleate, glycerol monomethyl ether, pentaerythritol, 9,10-dihydroxystearic acid, 9,10-dihydroxystearic acid methyl ester, 1,2-butanediol, 2,3-hexanediol, 2,4-hexanediol, pinacol, erythritol, arabitol, sorbitol, mannitol, 1,2-cyclohexanediol and xylene glycol. Carbohydrates, such as sugars, starches, cellulose, etc., can likewise yield esters. The carbohydrates can be exemplified by glucose, fructose, sucrose, rhamnose, mannose, glyceraldehyde and galactose.

A particularly suitable group of polyhydric alcohols are those having at least three hydroxy radicals, some of which have been esterified with a monocarboxylic acid having from about 8 to about 30 carbon atoms, such as octanoic acid, oleic acid, stearic acid, linoleic acid, dodecanoic acid or tall oil acid. Examples of such partially esterified polyhydric alcohols are the monooleate of sorbitol, the distearate of sorbitol, the monooleate of glycerol, the monostearate of glycerol, the didodecanoate of erythritol.

The esters may also be derived from unsaturated alcohols, such as allyl alcohol, cinnamyl alcohol, propargyl alcohol, 1-cyclohexene-3-ol, and oleyl alcohol. Still other groups of alcohols capable of yielding the esters of the present invention include ether alcohols and amino alcohols including, for example, oxyalkylene-, oxyarylene-, amino-alkylene- and amino-arylene-substituted alcohols with one or more oxyalkylene-, amino-alkylene- or amino-arylene-oxyarylene radicals. They are exemplified by Cellosolve, carbitol, phenoxyethanol, heptylphenyl-(oxypropylene)6-H, octyl-(oxyethylene)30-H, phenyl-(oxyoctylene)2-H, mono-(heptylphenyloxypropylene)-substituted glycerol, poly(styrene oxide), aminoethanol, 3-aminoethylpentanol, di(hydroxyethyl)amine, p-aminophenol, tri(hydroxypropyl)amine, N-hydroxyethylethylenediamine, N,N,N',N'-tetrahydroXi- trimethylenediamine, and the like. For the most part, ether alcohols with up to about 150 oxyalkylene radicals, wherein the alkylene radical contains from 1 to about 8 carbon atoms, are suitable. ' The esters may be vanadium esters of succinic acids or acid esters, i.e. partially esterified succinic acids, as well as partially esterified polyhydric alcohols or phenols, i.e. esters with free alcoholic or phenolic hydroxy radicals. Mixtures of the above-illustrated esters are also contemplated within the scope of the present invention. ' The alkenyl succinates may be reacted with boric acid or a similar boron-containing compound to form borated dispersants for use in the present invention. Such borated succinates are described in U.S. Patent No. 3,533,945. The borated succinates are intended to be included within the scope of the term "alkenyl succinate".

Alkenyl succinimides and succinates are present in the lubricating oil compositions in an amount effective to act as a dispersant and to prevent the deposition of contaminants formed in the oil. The amount of alkenyl succinimides and succinates may range from about 0.5 to about 20 weight percent of the total lubricating oil composition. Suitably, the amount of alkenyl succinimide or succinate which may be present in the lubricating oil composition is from about 2 to about 5 weight percent of the total composition.

The finished lubricating oil may be "single" or "multi-grade". "Multigrade" lubricating oils are prepared by adding viscosity index (VI) improvers. Typical viscosity index improvers are polyalkylene methacrylates, ethylene propylene copolymers, styrene-diene copolymers and the like. So-called decorated VI improvers with both viscosity index and dispersant properties are also suitable for use in the formulations of the present invention.

The following examples are given to specifically illustrate the present invention. w- 10 15 20 25 30 35 '40 IL 456 743 Example 1. Preparation of Borated Glycerol Monooleate To a mixture containing 125.23 g of glycerol monooleate (45 to 55 wt%) and glycerol dioleate (55 to 45 wt%) were added 30.92 g of boric acid and 250 ml of xylene. The reaction mixture was heated to 99° to 141°C for 9.5 hours under nitrogen under azeotropic conditions. 17.6 ml of water was collected through a Dean Stark trap. The reaction product was filtered and the volatiles were evaporated on a rotary evaporator under vacuum to 135°C to yield 128.35 g.

Analysis: boron 2.42% and 2.52% hydroxyl number 32 mg KOH/g.

Infrared spectroscopy analysis of the product shows no free hydroxyl stretch of the glycerol type but has strong BO-H bonding and virtually no B-O-B type absorption.

Example 2. The compositions of the present invention were tested in a laboratory test. The test was conducted on an SAE No. 2 friction machine modified by the addition of a moderate speed hydraulic motor drive. Test pieces were a composite of a sintered bronze plate of General Metals Powder Co. 1500 powder blend between two steel shim plates, mounted in the above apparatus. The test fluid, approximately 300 g in quantity, was then added to the test oil reservoir. The hydraulic drive rotated the test pieces at 100 rpm. A piston-like brake was applied using a 517 kPa gauge pressure.

SAE No. 2 load cell measured the braking torque and an electrical tachometer measured the rpm. An x-y recorder was used to generate a trace of torque versus rpm as the hydraulic drive was slowly regulated to reduce the speed to 0 rpm. The occurrence of brake noise for a fluid is related to the slope of the friction versus speed curve. The slope of the curve was found by measuring the slope of a line drawn through the 50 rpm point on the graph and the highest point on the graph below 50 rpm. As the slope of this curve became more and more negative, the brake noise became increasingly louder. This tendency is consistent with full-scale tractor brake noise testing.

The above described tests were run on three mineral oil-based hydraulic tractor fluids. The results for these three fluids are shown in Table I. Composition A has a base oil without a friction modifier and Composition B additionally contains 1% borated glycerol monooleate from Example 1. Composition C is a commercial hydraulic tractor fluid. As shown in Figure 1, the addition of borated glycerol monooleate (Fluid B) to the base fluid (Fluid A) increased the slope indicating that it was effective in reducing brake oil noise. Also shown in Table I is the slope obtained with a commercial hydraulic tractor fluid.

Table I Effect of borated fatty acid ester on brake noise in laboratory simulation Preparation Slope of friction versus speed curve A - base oil -0.0131 B - base oil + 1 wt.% borated glycerol oleate according to example 1 -0.0092 C - commercial preparation -0.0145

Claims (4)

f 456 743 in 1 "Patent Claims Use of a composition comprising a lubricating oil containing from 0.1 to 5% by weight of a boronated fatty acid ether of glyoerol, to reduce noise from oil immersed equivalent brake by lubricating the contact surfaces of oil immersed equivocal brakes with the composition. Use according to claim 1, characterized in that the borated fatty acid ether of glycerol is a borated glycerol oleate. Use according to claim 2, characterized in that. that the borated fatty acid ester of glycerol is a mixture containing 45 to 55% by weight of borated glycerol monooleate and 55 to 45% by weight of borated glycerol dioleate. Use according to claim 2, characterized in that the borated fatty acid ester of glycerol is borated glycerol monooleate. >