US2459717A - Organic lubricant composition - Google Patents

Description

Patented Jan. 18, 1949 ORGANIC LUBRICANT COMPOSITION George L. Perry, Berkeley, Calif., assignor to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application January 28, 1946, Serial No. 642,986

13 Claims. (01. 252-485) This invention relates to compounded lubricating oils and more particularly to the type of lubricant especially applicable to use in steam turbines.

A serious problem in the lubrication of turbines is the prevention of rusting. Rust may be promoted by steam or water which penetrates valve packings, by moisture which condenses from the atmosphere within the engine orifices or by water dissolved in or. set free by chemical changes in the lubricant. In addition to weakening the metal parts from which it is derived, rust may accelerate greatly the oxidation or degradation of the lubricant as well as interfere with clearances and clog delicate engine parts such as the governor mechanism by circulating through the oil system. Accordingly, a turbine lubricant should contain a rust inhibitor.

Another dimculty which must be guarded against in steam turbines is the occurrence of emulsions in the lubricating system. Since some water inevitably creeps into the lubricant from time to time, the presence of emulsifying agents in the lubricant must be strenuously avoided, first by employing a highly refined oil (petroleum or mineral oil), and secondly by insuring that no emulsifying agent is later incorporated in the oil. The damage caused by emulsions may occur in several ways: The viscosity of the emulsified oil is vastly difierent from that of the original lubricant, thus altering the speed of circulation as well as the lubricating properties; in addition, an emulsion will quickly pick up and circulate any sludge or sediment that may be prescut and thereby impart to the lubricant an undesirable scouring or abrasive action. Thus, it will be apparent that no additive, Whether to inhibit rusting or for some other purpose, can be tolerated in a turbine lubricant if such additive is also an emulsifying agent.

An additional problem which has become of increasing seriousness of late is the large amount of wear occurring at points of stress or strain in the turbine such as in the reduction gears. This is accentuated by the modern trend to make turbines as compact as possible, which object is attempted to be realized by reducing the size and (if possible) increasing the strength of the working parts. As a consequence, numerous units of such design have had to be replaced due to, their breakdown in actual service in a comparatively short time.

Attempts to remedy this situation by improving the lubricant, such as by incorporating therein a wear reducing or extreme pressure (E. P.)

agent, have met with failure due to the unsuitability for one reason or another of the additives for this application. Thus, most E. P. additives are emulsifying agents, often decrease the oxidation stability of the lubricant, produce corrosive oils, and interfere with the action of the antirusting agent. For example, organic chlorides which have been widely used as extreme pressure agents in lubricants are both emulsifying agents and corrosion promoters. Certain organic phosphorus compounds which are employed in extreme pressure lubricants also possess both these disadvantages. Thus, polylauryl phosphate decreases the oxidation stability and permits vapor space rusting while tricresyl phosphate, in addition to being corrosive, decreases the film tenacity of the oil. Certain sulfur-containing antiwear or E. P. agents possess similar hanadlcaps. For instance, alpha mercapto stearic acid increases emulsiflcation, decreases oxidation stability, and allows vapor space rusting while sulfurized sperm oil increases emulslfication and decreases film tenacity of the oil. Also, the presence of stearic acid decreases oxidation stability.

Similar problems of rusting or corrosion and wear with lubricants used in contact with metal surfaces arise in connection with damping or hydraulic oils, such as for recoil mechanisms, oils for gears where high wear (i. e. seizure) is not encountered, and other compositions. Likewise, in the lubrication of internal combustion engines, one finds the association of high temperatures, metallic surfaces, and the occurrence of moisture.

It is therefore an object of this invention to provide an organic lubricant composition having both antirusting and antiwear properties, but which does not possess emulsion-forming or other deleterious characteristics. It is another object to provide a mineral oil composition having properties which render it especially suitable for use as a lubricant in turbines, internal combustion engines, and other similar mechanisms, such as' in damping or hydraulic devices, etc.

It has now been found that an improved organic lubricant composition can be formed by incorporating two additives in a suitable base, such as an oleaginous or mineral 011 base, whereby there is obtained a lubricant having both antirusting and antiwear properties without emulsion-forming tendencies or other undesirable properties, which lubricant is especially suitable for use in turbines.

Turbine oils can be produced by employing well refined lubricating oils of a proper viscosity range which may be between about '75 and about tung oil, soya bean oil, fiaxseed oil, tallow, lard,

stearine pitch, etc., as well as in the so-called synthetic lubricants such as polymerized olefins, alcohols, esters, olefin oxides, etc.

The corrosion or rust inhibitor used in the present combination is a relatively high molecular weight dibasic acid. By dibasic acid is meant an acid having two acidic or ionizable hydrogen ions. The two acidic radicals should be separated by no more than about four carbon atoms and preferably by no more than two or three. Such acids are, for instance, high molecular weight saturated or unsaturated polycarboxylic acids stable under ordinary lubricat- 7 ing conditions, such as alkylated aliphatic polycarboxylic acids like alkylated succinic, glutaric, adipic, etc., acids. The oxygen in the acid radicals may also be replaced in whole or in part by sulfur to give the corresponding thio equivalents as thiolic (--COSH) thionic (-CSOH) or thionthiolic (-CSSH) acids.

The dibasic acid may also be a monocarboxylic acid whose second acidic hydrogen atom is supplied or activated by a radical such as nitro, nitroso, cyano, hydrosulfide, or aromatic sulfonyl which is not more than about two or three carbon atoms removed from the carboxylic radical. These monocarboxylic acids themselves should contain a minimum of 12 to 16 carbon atoms in addition to the added radical. Thus, taking stearic acid as an example, its dibasic corrosioninhibiting derivatives would be alpha or beta nitrostearic acid, alpha or beta nitrosostearic acid, alpha or beta cyanostearic acid, alpha or beta mercaptostearic acid, alpha or beta phenylsulfonylstearic acid, etc.

One or both of the acidic groups may be attached to an aromatic nucleus, as in alkylated salicylic acids,such as di-isopropyl-salicylic acid, alpha (orthocarboxyl aryloxy) carboxylic acids such as nooc ooncoon One may also use dibasic acids wherein the two acidic groups are joined through an oxygen, sulfide, disulfide, or nitrogen linkage, as

ROH(CH2) C0011 R H(CH2),,C O OH wherein X is an oxygen, sulfur 01' nitrogen atom, u and 11:0 or 1, z is a small integer such as 1 or 2, and each R is an organic radical, conveniently a fatty acid radical.

Hydroxamic acids are also effective dibasic corrosion inhibitors.

These corrosion inhibitors may also contain ether, amino, sulfide, disulfide, etc., radicals elsewhere in the molecule. Those dibasic acids having at least one carboxylic radical are preferred. Mixtures of the various dibasic acids, as well as the pure compounds, may be used.

The saturated acids are preferred because of their greater stability toward oxidation which results in longer active life. Also, those corrosion inhibitors which consist only of carbon, hydrogen chain fatty alcohols, etc., and condensing them with maleic acid anhydride to produce an alkylene succinic anhydride, and hydrolyzing the latter to produce the corresponding free acid, which may then be hydrogenated if desired. Such acids have been described in U. S. Patent No. 2,133,734.

The antiwear additive used in the present invention is an oil-soluble, liquid, sulfurized product of a liquid unsaturated fatty acid, prefera'bly of 8 to 26 carbon atoms. These sulfurized products of unsaturated fatty acids may be formed by reacting sulfur with unsaturated fatty acids at temperatures of, for example, from about C. to about 300 C. The amount of sulfur used to sulfurize the unsaturated fatty acid may be varied according to the particular fatty acid used and the specific characteristics desired in the final product. Generally, an amount of sulfur sufficient to substantially saturate the olefinic double bonds of the fatty acid is employed. The sulfur, preferably in a finely divided state, may be added gradually to heated unsaturated acid while agitating the mixture, After all the sulfur is added, the mixture is heated further until the reaction is completed. The unsaturated fatty acids may also be sulfurized by reaction with sulfur monochloride, phosphorus polysulfide, such as phosphorus sesquisulfide, or other compounds capable of sulfurizing, i. e. of introducing sulfur in non-oxidized form, into the unsaturated fatty acid. It is sometimes desirable to blow or bubble air. steam, inert gases or the like through the sulfurized unsaturated fatty acids. The value of the sulfurized products of unsaturated fatty acids as oil additives is considerably improved by subjecting them to treatment with a filter clay which removes deleterious amounts of undesirable constituents.

The sulfurized unsaturated fatty acid is used as the free acid, and the preferred agent is sulfurized oleic acid, particularly sulfurized oleic acid prepared by reacting oleic acid with free sulfur. Other suitable acids which may be sulfurized include, for example, hypogaeic acid, elaidic acid, erucic acid, brassidic acid, linoleic acid, linolinic acid, etc.

A sulfurized product of an unsaturated fatty acid which is particularly effective as an antiwear agent in lubricating compositions may be prepared by reacting free sulfur with an unsaturated fatty acid in a molal ratio of sulfur to unsaturated fatty acid which is greater than one to one, but preferably less than two to one.

The following description of a preferred method used in the preparation of an especially effective antiwear additive is given for the purpose of illustration:

Oleic acid of a good commercial grade was heated in a suitable vessel to a temperature of about 150 C. The heated oleic acid was blanketed with an inert atmosphere, such as nitrogen, natural gas. etc., and then, for each molecular part (282 parts by weight) of oleic acid, about 1.3

atomic parts (32 parts by weight) of sulfur flowers (corresponding to about 14.6% by weight sulfur based on the weight of oleic, acid,- or about 13% sulfur based on the total of oleic acid plus sulfur) was added to the heated acid. The mixture was .well stirred and maintained at a temperature of about 150 C. to 180 C. for a period of from about 3% to 4 hours.

To the crude product was slowly added about 20% to 30% by weight of an acid-washed adsorptive clay (Super Filtrol) while the temperature was maintained at about 140 C. to 160 C. After all of the clay had been added and well mixed with the sulfurized oleic acid product, the clay and substances adsorbed thereon were removed by filtration. The recovered slufurized oleic acid was a fairly viscous, reddish-yellow colored, clear liquid which was fairly soluble in mineral oil compositions. Analysis indicated a content of combined sulfur which corresponded substantially to the sulfur content of the mixture of oleic acid and sulfur as mixed.

Efiective amounts of the sulfurized unsaturated fatty acids in a turbine oil are in the order of from 0.005% to 0.1% by weight, although quantities of between 0.01% and 0.05% by weight are usually suiilcient and even preferred. Amounts of the dibasic acid anticorrosive agent between about 0.01% and about 0.5% by weight may be employed. Usually a combined weight of from about 0.02% to about 0.1% for both additives is satisfactory, although the combination of agents is effective at lower concentrations, particularly when added to turbine oils.

It will be seen that the small amounts of additives sufiiclent to accomplish the present purpose are much less than would be required to alter the other properties of the lubricating composition. Thus, at the low concentration of the sulfurized unsaturated fatty acid used here in turbines, no resistance to extreme pressure wear (i. e., where seizure occurs) is obtained. Only when used in amounts greater than 0.1 by weight do extreme pressure agents become effective as such. With less than 0.1% and particularly less than 0.05% the present agents prevent low pressure or corrosive wear.

It has been found that the combination of the dibasic acid anticorrosive and the sulfurized unsaturated fatty acid in turbine oils has advantages which could not be obtained by any other known combination of additives. These advantages are, in particular, non-corrosiveness, and a hitherto unachieved reduction in wear without increased tendencies towards emulsion formation, decreased film tenacity, decreased oxidation stability, increased vapor space rusting. As pointed out hereinabove, other antiwear agents impart one or more deleterious properties to turbine oils, whereas the combination of sulfurized unsaturated fatty acids with the dibasic acid anticorrosive not only reduces wear and the corrosiveness of the oil, but also gives a reduction in friction.

The present turbine oil additives were tested alone and together in the multiple four-ball machine similar in principle to the Boerlage apparatus described in the magazine, Engineering, vol. 136, July 14, 1933. This apparatus comprises four steel balls arranged in pyramid formation. The top ball is rotated by spindles against the three bottom balls which are clamped in a stationary ball holder. The balls are immersed in the oil to be tested. Tests were run for two hours at 100 R. P. M. under a 7.0 kg. load and at various temperatures. The diameters of the wear scars worn on the three balls forming the base of the pyramid were then measured, and the average taken as the true indication of wear. Results from tests using a highly refined turbine oil, 185-205 8. U.

at 130 F., and containing 0.25% by weight ditertiary butyl p-cresol (employed as an antioxidant) were as follows:

TABLE I Wear evaluation m the multiple four-ball machine Scar Diameter (mm) at Cone. of Various Temperatures Additive (dgiitive) 0 y wt.

None .47 57 6'3 A saturated allryl succinic acid of approx. 370 mol. wt... 0. 015 50 61 62 0. 05 52 0. l0 22 33 D0 O. 25 23 .37 31 A saturated alkyl suecinic acid of approx. 370 mol. wt. 0.015

39 4i 35 suliurized oleic acid 0.01 A saturated alkyl succinic acid oi approx. 370 mol. wt. 0. 015

. 27 .25 24 suliurized oleic acid 0. 025 A saturated alkyl succinic acid oi approx. 370 mol. wt. 0. 015

. 24 24 29 suliurized oleic acid 0.05 A saturated alkyl succinic acid of approx. 370 mol.wt.. 0.015 Z; 25 suliurized oleic acid 0. 10 A saturated alkyl succinic acid of approx. 370 moi. wt 0. 015

.21 .a's suifurlzed oleic acid 0.25

The effect of the present and other additives on the properties of turbine oils, other than wear reduction, were also determined. The base oil used was a highly refined turbine oil of about 400 U. S. seconds viscosity at F. containing 0.25% by weight di-tertiary butyl p-cresol. The additives were incorporated into this base oil and subjected to the following tests.

The rusting test was carried out by immersing a polished low-carbon cold-rolled steel specimen (3 mm. x 12 mm. x '76 mm.) in 350 ml. of the test oil, which was continuously agitated. Thirty minutes after starting, 10% by volume of synthetic sea water was added to the oil (the synthetic sea water was formulated to contain in 1000 ml. water11.0 g. MgCl2-6H2O; 4.0 g. Na2SO4 (anhydrous); 1.2 g. CaClz (anhydrous) and 25.0 g. NaCl). Additional amounts of water were added as required to maintain a constant volume. The test was continued for 48 hours at a controlled temperature of 75 C. Thereafter the steel specimen was washed with naphtha and acetone, and evaluation of the test result was expressed as per cent of surface rusted.

The film tenacity test was performed by dipping a polished steel strip (as in the above rusting test) into the test oil for 30 minutes, removing and allowing the strip to drain for 10 minutes, and then placing the oil-coated strip in well stirred water at a constant temperature of 75 C. The time elapsed until rusting starts, after the strip is transferred to the water, is a. measure of the tenacity of the film formed. A period of two hours in this test is considered satisfactory.

The turbine oxidation stability test (T. O. S. T.) described in 43 Proc. A. S. T. M. 275 (1943), is

carried out as follows: The 011 sample is subjected to a temperature of 95 C. in the presence of water, oxygen and an iron-copper catalyst, the time required to build up a neutralization number of 2.0 mg. KOH/gm. 011 being determined. The essential features of the tests are as follows: The oxidation cell is a glass tube 45 mm. x 600 mm. fitted with a mushroom water condenser and an oxygen delivery tube with fritted glass outlet. The catalyst consists of lengths of No. 14 A. W. G. open-hearth iron wire and electrolytic copper wire, each three meters long and wound into coils about 0.625 in. in diameter. The cell containing 300 ml. oil sample and the iron-copper catalyst is assembled with the condenser and oxygen inlet tube and placed in a thermostatically controlled bath capable of maintaining a temperature of 95:05" C. in the sample. Oxygen is admitted at a rate of 3:0.5 liter per hour and, at the end of 30 minutes, 60 ml. of distilled water is added to the cell. The test is then continued until acids are formed to the extent that the neutralization number of the oil reaches a value of 2.0 mg. KOH/gm. of oil.

Emulsion tests were performed with both distilled water and 1% NaCl solution at 130 F., according to "Federal Specification for Lubricants and Liquid-Fuels; General Specifications," Fed. Spec. No. 320,13,VV-L-791C, Feb. 19, 1942, sec. 1V, part 5, p. 116, wherein equal volumes (40 ml.) of the test oil and water are stirred for 5 minutes at 1500 R. P. M., and then after stopping the stirring the time to completely break the emulsion is determined. Generally, a maximumof 2 ml. emulsion remaining at the end of 30 minutes is allowed. In some cases, where unsatisfactory ;est is obtained at 30 minutes, the amount of un- Jroken emulsion remaining is recorded.

The results of these tests are shown in the folowing table:

present invention. Suitable antioxidants include. for example, polyalkyl arylhydroxy compounds having one or more hydroxy groups, preferably with short alkyl groups up to about eight or ten carbon atoms attached at the two, four and/or six positions, and advantageously with at least one tertiary alkyl group, such as 2,4,6-trimethylphenol, pentamethylor pentaethyl-phenol, 2,4- dimethyl-fi-tertiary-butyl phenol, 2,4-dimethy1- 6-octylphenol, 2,6-di-tertiary-butyl 4 methylphenol, 2,4,6-tri-tertiary-butylphenol, 2,4-dimethyl-G-tertiary octylphenol, etc.; amino phenols as benzyl amino phenols; amines such as dibutyl phenylene diamine, diphenyl amine, phenyl-beta-naphthylamine, dinaphthyl amines, etc, sulfur-containing antioxidants such as in the form of mercaptans, as in decyl mercaptans, dodecyl mercaptans, cetyl mercaptans, oleyl mercaptans, stearyl mercaptans; butyl or other higheralkyl thiophenes; thionaphthols, alkyl thionaphthols, etc.; or of polysulfides (R(SS)R'), as in diamyl disulfide and higher dialkyl disulfides, e. g. diphenyl disulfides, dibenzyl disulfide, dinaphthyl disulfides, wax polysulfldes formed by reaction of polychlorinated wax and sodium polysulflde, etc.; or of non-acidic sulfur compounds such as formed by reacting sulfur with olefins at temperatures of about 150 C. to 300 C.

Additional corrosion inhibitors or antirusting compounds may also be present in some instances, and include, for example, organic nitrogen compounds containing an acidic radical in close proximity to a nitrile, nitro or nitroso group (e. g., alpha cyano stearic acid).

I claim as my invention:

1. A lubricating composition comprising a major amount of a mineral lubricating oil containing from about 0.01% to about 0.5% by weight of a saturated alkyl succinic acid of at least 16 carbon atoms and from about 0.01% to TABLE II General properties of turbine oil additives highly refined mineral oil having a viscosity of 185 to 205 S. U. at 130 F. and containing 0.25 (ii-tertiary butyl para-cresol as an antioxidant was used as a base oil.]

0 f Emulsion Tests Time to Separate ggf g Film Te O. (minutes) Additive by Busting Test nafggmilssast Lire (Hours) Distilled Water 1% NaCl Solution 1, 415 lone 1,488 Satisfactory at 7 Satisfactory at 10 1, 230 min. min.

saturated alkyl succinic acid of 0. 015 Satisfactory at 48 6. 0 728 Satisfactory at 19 Satisfactory at 26 approx. 370 mol. wt. hrs. 760 mm. min.

saturated alkyl succinic acid oi 0.015 fj do 5. 5 130 Satisfactory at 15 Satisfactory at 15 sulfurizeddoleiliacid. i.. .d.. "f.

a Y *atisfactor at 48 4. 5 51s Unsatisfactory 4o Unsatisfactory 6 approx. 370 mol. wt. hm i of cc. atf30 lillih; 24 cc. at 30 min: ga sltearic acid d 0 6?? per phase rusting. cc. at 0 mm.

t succ'n nci o ui i irgif w n iolywt. l w Satisfactory at 48 3.5 865 Unsatisfactory, 10 cc. Unsatisfactory, 13

hrs, at 30 min; 4 cc. cc. at30min. sulfurized sperm oil 0.30 at 1 r.

In some instances, it may be advantageous to icorporate in the lubricant composition other dditives, such as antioxidants, antifoaming gents, pour point depressors or viscosity imrovers, etc. However, no compounds, such as ietallic salts, which react with either of the rimary additives, or detergents tending to form nulsions in turbine oils should be employed.

It is sometimes especially desirable to incora'rate an antioxidant in the turbine oils of the about 0.1% by weight of sulfurized oleic acid.

2. A lubricating composition comprising a major amount of a mineral lubricating oil, containing from about 0.01% to about 0.5% by weight of a saturated alkyl succinic acid of at least 16 carbon atoms, from about 0.01% to about 0.1% by weight of sulfurized oleic acid, and a minor amount, sufiicient to inhibit oxidation, of a polyalkyl phenol said alkyl radical having up to 10 carbon atoms.

3. A lubricating composition comprising a major amount of a mineral lubricating oil, containing from about 0.01% to about 0.5% by weight of a saturated alkyl succinic acid of at least 16 carbon atoms, from about 0.01% to about 0.1% by weight of sulfurized oleic acid, and a minor amount, sufficient to inhibit oxidation, of a di-tertiary butyl para-cresol.

4. A lubricating composition comprising a major amount of a mineral lubricating oil, and a minor amount sufllcient to inhibit corrosion, of a saturated alkyl succinic acid of at least 16 carbon atoms, and from about 0.01% to about 0.1% by weight of sulfurized oleic acid.

5. A lubricating composition comprising a major amount of a mineral lubricating oil, a minor amount suficient to inhibit corrosion, of a saturated alkyl dibasic aliphatic acid of at least 16 carbon atoms, and from about 0.01% to about 0.1% by weight of sulfurized oleic acid.

6. A lubricating composition comprising a major amount of a mineral lubricating oil, a minor amount sufficient to inhibit corrosion, of a saturated alkyl dibasic aliphatic acid of at least 16 carbon atoms, and from about 0.01% to about 0.1% by weight of a sulfurized unsaturated fatty acid having from 8 to 26 carbon atoms.

7. A composition comprising a major amount of a mineral oil, a minor amount sufllcient to inhibit corrosion, of a saturated alkyl dibasic aliphatic acid of at least 16 carbon atoms, and from about 0.01% to about 0.1% by weight of a sulfurized unsaturated fatty acid having from 8 to 26 carbon atoms.

8. A composition comprising a major amount of a mineral oil, a minor amount sufllcient to inhibit corrosion, of an unsaturated alkyl dibasic aliphatic acid of at least 18 carbon atoms, and from about 0.01% to about 0.1% by weight of a sulfurized unsaturated fatty acid having from 8 to 26 carbon atoms.

9. A composition comprising a major amount of a mineral oil, a minor amount sumcient to inhibit corrosion, of a saturated alkyi adipic acid of at least 16 carbon atoms, and from about 0.01%

' 10 to about 0.1% by weight of a sulfurized unsaturated fatty acid having-at least 8 carbon atoms. a

10. A lubricating composition comprising a major amount of a mineral oil, a minor amount sufficient to inhibit corrosion of a saturated alkyi glutaric acid having at least 16 carbon atoms. and a wear reducing amount of less than 0.1% by weight of a sulfurized unsaturated fatty acid having at least 8 carbon atoms.

11. A composition comprising a major amount of an oleaginous base, a minor amount suilicient to inhibit corrosion, of an alkyl dibasic aliphatic acid of at least 16 carbon atoms, and from about 0.01% to about 0.1% by weight of a suifurized unsaturated fatty acid having at least 8 carbon atoms.

12. A composition comprising a major amount of a mineral oil, a minor amount sufficient to inhibit corrosion, of an alkyl dibasic aliphatic acid of at least 16.carbon atoms, and from about 0.01% to about 0.1% by weight of a sulfurized unsaturated fatty acid having at least 8 carbon atoms.

13. A composition comprising a major amount of a mineral oil, a minor amount sufllcient to inhibit corrosion, of an unsaturated alkyl dibasic aliphatic acid of at least 16 carbon atoms, and from about 0.01% to about 0.1% by weight of a sulfurized unsaturated fatty acid having at least 8 carbon atoms.

GEORGE L. PERRY.

nnrnnnncns man The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,974,299 Churchill Sept. 18, 1934 2,279,688 Larsen Apr. 14, 1942 2,334,158 Von Fuchs et a1. Nov. 9, 1948 2,371,142 Barnum Mar. 18, 1945 2,398,202 Zubiin- Apr. 9, 1868