US3007870A - Lubricating oil compositions containing sulfurized olefins and mixed salts - Google Patents

Description

" atent 3,007,870 Patented Nov. 7, 1961 fitice 3,007,870 LUBRICATING OIL COMPOSITIONS CONTAINING 'SULFURIZED OLEFINS AND MIXED SALTS Rosemary OHalloran, Union, N.J., assignor to Esso Research and Engineering Company, a corporation of Delaware [N Drawing. Filed Dec. 31, 1958, Ser. No. 784,086

1 Claim. (Cl. 252-407) This invention relates to lubricating oil compositions having low wear and high extreme pressure properties. Particularly, it relates to compositions suitable as hypoid gear lubricants which comprise lubricating oil, a sulfurized olefin, and a mixture of alkaline earth metal salts of at least two different fatty acids. More particularly, the invention relates to lubricating compositions containing sulfur-ized olefins with a mixture of alkaline earth metal salts of low molecular weight fatty acids in combination with alkaline earth metal salts of intermediate and/ or high molecular weight fatty acids.

Lubricants containing the mixed alkaline earth metal salts of high and/or intermediate molecular weight fatty acids with alkaline earth metal salts of low molecular weight fatty acids have been finding increasing application in industry because of their anti-wear properties. While prior lubricants of the mixed-salt type have some degree of load-carrying ability, particularly under conditions involving gradual loading, their load-carrying ability is not very great under conditions of shock loading. Thus, when it was attempted to adapt the mixedsalt lubricants to applications involving high shock loading conditions, such as are met by hypoid gear lubricants, it was found that the load-carrying ability of the lubricant was insufficient for this purpose. It has now been found that by adding to the mixed-salt type lubricants, a minor proportion of a sulfurized olefin, that extremely high shock load-carrying ability results. In fact, the resulting combination results in much higher load-carrying ability under shock conditions than would have been expected from the mere additive effect of the individual components. Apparently there is some sort of chemical interaction between the salts and the sulfurized olefins which accounts for this improved performance, although the nature of this interaction is not known at the present time. In brief, it has been found possible to formulate mixed-salt containing lubricants having not only low wear characteristics but also extremely high load-carrying ability under conditions of both gradual and shock loading. Lubricants of this type are particularly useful as rear axle lubricants for automotive use where gears are subjected to sudden and great loads and must operate over long periods of time with very little wear.

The sulfurized olefins used in the invention are prepared from aliphatic or terpenic olefins having a total of C to C carbon atoms in the molecule which are sulfurized to contain about 10 to 60, preferably 35 to 45 wt. percent sulfur. The aliphatic olefins will include mixed olefins such as cracked wax, cracked petrolatum, or single olefins such as tridecene-Z, octadecene-l, eikosene- 1, and polymers of aliphatic olefins having 2 to 5 carbon atoms jper monomer such as tri-isobutylene and tetrapropylene. The terpenic olefins will include terpenes (C H sesqui-terpenes (O l-I and diterpenes (C H The monocyclic terpenes having the general formula C H are particularly useful, e.g. dipentene /CHCH2 /OH: CH -C CH-C CH CHz CH The sulfurization of the olefin is usually carried out by simply heating the olefin with free sulfur to about to 250 C. The sulfur combines with the hydrocarbon quite readily with an evolution of hydrogen sulfide. The reaction product may be blown to eliminate hydrogen sulfide, washed, and low boiling constituents may be evaporated or distilled off with steam. In many cases a small amount of free sulfur is present, not having reacted, and this may be separated by filtration. The sulfur may be either active or inactive as measured by tests for extreme pressure and corrosivity as its state is immaterial for the purpose of the present invention.

The olefins may also be sulfurized by other methods. For example, they may be heated with sulfur halides, such as sulfur monochloride and sulfur dichloride. The resulting sulfurized material will contain small amounts of chlorine and may be used in this form in lubricating compositions in which the halide is not objectionable. Or the sulfurized material may be treated with alcoholic alkali to remove the halide.

Sulfurized olefins and their preparation are well known in the art (eg see US. Patents 2,312,750; 2,398,271 and 2,412,633) and their preparation forms no part of this invention.

The mixed-salt component of the lubricant will generally comprise in a molar ratio about 4 to 15, e.g. 5 to 10 moles of alkaline earth metal salt of a C to C fatty acid or fatty acid anhydride per mole of alkaline earth metal salt of the higher molecular weight fatty acid. The higher molecular weight acid may be entirely an intermediate molecular weight fatty acid or entirely a high molecular weight fatty acid, or blends thereof.

The C or C fatty acid portion of the mixed-salt is either acetic, propionic acid or acetic anhydride.

Intermediate molecular weight acids which may be used for the salt formation include those aliphatic, saturated or unsaturated, unsubstituted, monocarboxylic acids containing 7 to 12 carbon atoms per molecule, e.g., capric, caprylic, nonanoic acids, etc.

The high molecular weight carboxylic acids that can be used will include the saturated and unsaturated greasemaking fatty acids that are commonly known in the art. In general, these fatty acids have from 12 to about 30 carbon atoms, preferably about 14 to 22 carbon atoms per molecule, and saponification values of from 300 to 150. Suitable fatty acids include myristic acid, palmitic acid, stearic acid, the various hydroxy stearic acids, oleic acid, arachidic acid, behenic acid and the like. Naturally occurring fatty acids such as fish oil acids, tallow acid, etc. may also be utilized directly or after hydrogenation to decrease any undesirably high degree of unsaturation. Mixtures of these high molecular weight fatty acids, e.g. hydrogenated fish oil acids with oleic acid, in any proportions, are also operable, as are fractions obtained by distillation, extraction or crystallization.

The metal component of the mixed-salt thickeners of this invention will be an alkaline earth metal such as calcium, strontium, barium and magnesium. Mixtures of the grease-forming metals may be employed if desired. The metals are usually reacted with the acids in the form of metal bases, such as hydroxides or oxides. Calcium is preferred.

The lubricating oil used in the compositions of the invention may be a mineral lubricating oil having a Dean-Davis V.I. of 20 to 110, and of 70 to 150, preferably 90 to 100 SUS viscosity at 210 F.

Various other additives may also be added to the lubricating composition in amounts of about 0.1 to 10.0 weight percent, based on the total weight of the composition. For example, oxidation inhibitors such as phenyl a-naphthylamine; corrosion inhibitors; pour depressants, and the like may be added.

The metal mixed-salt portion of the final lubricating composition may be prepared by coneutralization of the acids with suitable bases. This is generally done in situ, in the lubricating oil. The coneutralized mixture is then heated to dehydrate the composition. However, the coneutralization method of preparation is not essential as the mixed-salt components may be separately prepared and then blended together. The sulfurized olefin is generally mixed in after the preparation of the mixed-salt material.

More specifically, the lubricant compositions of the invention are best prepared by dispersing the higher molecular weight acids and alkaline earth metal base (e.g. calcium hydroxide) in the lubricating oil; heating the mixture to a temperature within the range of about 130 to 180 F.; then adding the low molecular weight fatty acid followed by heating to about 225 to 350 F. to dehydrate the composition. The resulting product is then cooled to a temperature of about 180 to 200 F. and the sulfurized olefin and conventional lubricating additives added. The product is further cooled to about 120 to 150 F. and may then be homogenized at high rates of shear before cooling to room temperature.

The compositions of the invention will comprise a major proportion of mineral lubricating oil, about 5 to 15 wt. percent, preferably 6 to 10 Wt. percent of mixedsalt and 1 to 20 wt. percent, preferably 2 to 6 wt. percent of the sulfurized olefin.

The invention will be further understood by the following illustrations:

A mixed-salt base lubricant was prepared from the following ingredients:

4.46 wt. percent glacial acetic acid 1.18 wt. percent Wecoline AAC acid 3.30 wt. percent hydrated lime 90.93 wt. percent mineral lubricating oil having a viscosity of 80 SUS at 210 F. and a V.I. of about 35 0.13 wt. percent phenyl a-naphthylamine This lubricant was prepared as follows: The glacial acetic acid and the Wecoline acid (28 Wt. percent caprylic, 56 wt. percent capric and 16 wt. percent lauric acids) were added to a slurry of the lime in about a fourth of the oil. This concentrate mixture was. heated to about 320 F. until the water of hydration was driven off. The mixed-salt material was then cooled, the phenyl oc-naphthylamine added and an amount of oil equal to the weight of concentrate was added, i.e. the concentrate was diluted to /2 its salt content. The diluted material was homogenized twice in a Charlotte mill. The balance of the oil was then mixed in and the product again homogenized through a Charlotte mill.

EXAMPLE I-a 4.8 wt. percent of a sulfurized cracked petrolatum containing 42 wt. percent sulfur was added to 95.2 wt. percent of the above described base lubricant by simple mixing. For comparison 4.8 wt. percent of the same sulfurized material was added to a mineral lubricating oil having a V.I. of 92 and a viscosity at 210 F. of 90 SUS. This mineral oil is the base oil used in a commercial hypoid gear oil. Both compositions were then tested for load-carrying ability in an SAE machine operating at 1,000 r.p.m. and a 14.6 shaft ratio.

4 EXAMPLES I-b TO -I-d Example I-a was repeated except that varying amounts of the sulfurized olefin was used.

EXAMPLE II This example was carried out in the general manner of Example Ia with the same mixed-salt base lubricant, but using a sulfurized olefin of the type previously described containing 43% inactive sulfur and available under the trade name of Lubrizol 08-6248. For comparison, this latter sulfurized olefin was also tested in mineral oil per se.

Lubricant A.For further comparison, a sulfurized sperm oil containing 12% sulfur was added to the mixedsalt base.

The compositions of the above lubricants and their load-carrying ability are summarized in the following table along with tests made on the mixed-salt base composition per se, and on the 92 V. I. mineral lubricating oil described above.

Table I SAE Test (scale lbs. at 1,000 r.p.m. and 14.6 ratio) Example Wt. percent of additive N 0. Mineral Mixed-Salt Lubricating Base Oil, SUS Lubricant at 210 F.

and 92 V.I.

None 20 20 I-a 4.8% sulfurized cracked petro- 450+ 195 latum (42% S). I-b 4.0% sulfurized cracked petro- 300 latum. 2.4% sulfurized cracked petro- 210 latunl. 1.2% sulfurized cracked petrolatum. Lubricant A 4.57 sulfurized Sperm Oil 70 0 II 4.0% Lubrizol 08-6248 (43% S)- 450+ 230 The above table shows that both the mixed-salt base lubricant and the comparison mineral oil had low shock load-carrying ability per se. Adding the sulfurized cracked petrolatum had an extremely large effect on the mixed-salt (Ia) while having a much lesser effect on the plain lubricating oil. Examples L1) to La! illustrate that extreme pressure properties of the mixed-salt base are significantly improved even using smaller quantities of the sulfurized olefin. Example II using a different sulfurized olefin illustrates results similar to Example I-a. Lubricant A prepared from sulfurized sperm oil illustrates the lesser efi'ect due to the low percent of sulfur present, i.e. 12%.

EXAMPLE III The composition of Example II was further tested as a hypoid gear oil for use in automobile diiferential according to the General Motor Buick l0-A Test procedure using a 1956 Buick with a 3.36:1 gear ratio.

This Buick 10-A test is an actual road test and after a 19 mile warm-up between 40 and 50 m.p.h. and a noise check, consists of high speed cycles of driving from 60 to 109 m.p.h.; 3 shock cycles at 50 to 35 m.p.h.; three shock cycles at 60 to 45 m.p.h., and three more shock cycles at 70 to 55 m.p.h., followed by 10 more high speed cycles of 60 to 109 m.p.h. The high speed cycles were carried out by rapidly accelerating from 60 to 109 m.p.h., then allowing the auto to coast until the speed was back to 60 m.p.h., then the cycle was repeated. The shock cycles were carried out by allowing the auto to coast from the higher speed until the lower speed was reached and then shifting into low gear. Upon completion of the completed test, the diiferential was disassembled and the ring and pinion gears examined. The results obtained are summarized in the following table along with similar test data obtained on a currently commercial hypoid gear oil.

Table II GEAR TOOTH CONTACT SURFACE CONDITION Pinion Ring Composition of Example II Drive Coast Drive Coast 11;. bright--- 1t. bright"- 11:. bright. nil. nil nil.

none.

Do. Do. stalling... Do. Score Do. Discoloration Do. Corrosion. Do. Commercial Gear Oil: 1

Burnish 1t. bright-.. lt. bright. Wear. nil trace. Ripplin none-. none. Ridging Do. Fittin D0. D0. Score 70% of surface was med. to heavy scored. Discoloratlon r do none. Corrosion..- do Do.

10-0 which is a chlorinated, sulfurized waxkerosene additive.

As seen from Table II, the composition of the invention, Example II, was superior to the commercial hypoid gear oil in showing no scoring and no wear, while being equal in the other respects.

The addition of other extreme pressure additives shows substantially the same result in the mixed-base lubricant as in mineral oil. Thus, 10 wt. percent of Parapoid 10C, a wax-kerosene mixture containing about 6% sulfur and about 30% chlorine, increased the SAE test of the mixedsal-t base lubricant to 315 lbs., While the same amount of Parapoid IO-C increased the comparison mineral oil (92 V1. and 90 SUS at 210 F.) to 325 lbs. As previously mentioned, it is believed that the outstanding results obtained in the present invention are due to some sort of reaction between the mixed-salts and the sulfurized olefin.

While the examples of the invention have illustrated the invention using an intermediate molecular weight fatty acid, a high molecular weight fatty acid may be correspondingly used. For example, Example I-a may be repeated, but using 1.18 wt. percent of oleic acid in place of the 1.18 wt. percent Wecoline AAC acid used to prepare the mixed-salt lubricant. Also, a sulfurized terpene may be used. For example, Example I-a is re- 50 peated but using 4.8 wt. percent of sulfurized dipentene having a sulfur content of 40 wt. pencent sulfur in place of the 4.8 wt. percent sulfurized cracked petrolatum.

and 10 wt. percent of Parapoid What is claimed is:

A lubricating composition comprising a major amount of mineral lubricating oil, about 6 to 10 wt. percent of a mixed salt material and about 2 to 6 wt. percent of sulfun'zed cracked petrolatum having a sulfur content of about 35 to 45 wt. percent sulfur, wherein said mixed salt material comprises about 5 to 10 molar proportions of calcium salt of acetic acid per molar proportion of calcium salt of a higher fatty acid having 8 to 12 carbon atoms per molecule.

References Cited in the file of this patent UNITED STATES PATENTS 2,218,132 Lincoln et al. Oct. 15, 1940 2,537,297 Alexander Jan. 9, 1951 2,735,815 Morway Feb. 21, 1956 2,815,326 Cyphers et al Dec. 3, 1957 2,842,495 Morway et al. July 8, 1958 2,846,392 MorW-ay et al. Aug. 5, 1958 2,861,043 Morway et :al Nov. 18, 1958 2,863,847 Morway Dec. 9, 1958 2,898,297 Schot-t Aug. 4, 1959 FOREIGN PATENTS 676,712 Great Britain July 30, 1952 778,567 Great Britain July 10, 1957 789,855 Great Britain Jan. 29, 1958