US3451930A - Lubricant composition for highly stressed gears - Google Patents

Description

United States Patent 3,451,930 LUBRICANT COMPOSITION FOR HIGHLY STRESSED GEARS George A. Mead, Scotch Plains, N.J., assignor to Esso Research and Engineering Compan a corporation of Delaware No Drawing. Filed Sept. 16, 1966, Ser. No. 579,833 Int. Cl. Cl0m 3/42 U.S. Cl. 252-32.7 4 Claims ABSTRACT OF THE DISCLOSURE This invention concerns an improved lubricating oil composition which is particularly useful in mechanical systems, wherein the gears are under high stresses as, for example, in rear axles and in tractor transmissions. In particular the invention concerns a gear lubricant containing in combination an alkaline earth metal salt of a hydrocarbon sulfonic acid, a metal salt of a dialkyl dithiophosphoric acid and a chlorinated hydrocarbon.

There are many modern day mechanical systems wherein a lubricant must serve both as a transmission fluid and as a gear lubricant. One such system is what is known as a transaxle unit wherein the transmission and the rear axle system of an automobile are combined into a single mechanical unit located near the rear wheels of the automobile. Another such system is the transmission of a modern farm tractor. In such mechanical systems the gears are placed under high stress and thus require a lubricant which will perform satisfactorily.

In accordance with the present invention it has been found that an unusually effective gear oil composition capable of satisfactory lubrication under conditions wherein the gears are under very high loads, e.g. 5 00,000 pounds per square inch, can be prepared by incorporating into the composition a combination of three types of additives. One of these is an alkaline earth metal salt of a hydrocarbon sulfonic acid having a molecular weight in the range of about 400 to 900. A second component is a metal salt of a dialkyl dithiophosphoric acid and the third component is a chlorinated hydrocarbon. Each of these additives has been employed in the past as a component of a lubricating composition. Chlorinated hydrocarbons are well known components capable of imparting extreme pressure properties to a lubricating oil. Metal salts of dialkyl dithiophosphoric acids are known in the art as anti-wear agents and as anti-oxidants. Alkaline earth metal salts of hydrocarbon sulfonic acids have been employed in the art primarily as dispersants. It has now been surprisingly found that these three types of additives in combination exert a synergistic improvement in loadcarrying capacity.

The alkaline earth metal salts employed in this invention are the metal salts of hydrocarbon sulfonic acids wherein the acids have molecular weights in the range of about 400 to 900. The alkaline earth metal salts include those of calcium, strontium and barium. Sulfonic acids from which the salts are prepared are classified generally as either petroleum sulfonic acids or synthetic sulfonic acids. Petroleum sulfonic acids are produced by treating petroleum fractions, including lubricating oil distillate fractions, the socalled white oil distillates, or other petroleum fractions such as petrolatum, with suitable sulfonating agents including sulfur trioxide, concentrated sulfuric acid and fuming sulfuric acid. Synthetic sulfonic acids are prepared by treating relatively pure synthetic hydrocarbons in the same manner. Usually the synthetic hydrocarbons are alkylated aromatic hydrocarbons such as the products of alkylation of benzene, toluene, xylene or naphthalene. Typically benzene is alkylated with a polymer of propylene or butylene, e.g. butylene trimer, to form a C alkyl benzene which is then sulfonated as above-described. The natural or synthetic sulfonic acids whose alkaline earth metal salts are used in this invention include alkane sulfonic acids, aromatic sulfonic acids, alkaryl sulfonic acids, and aralkyl sulfonic acids.

The term sulfonate as used herein and in the appended claims includes both neutral sulfonates, i.e. those wherein the sulfonic acids have been neutralized with an equal mole equivalent of metal base, and high alkalinity sulfonates wherein additional metal base in excess of that required for simple neutralization has been reacted with the sulfonic acids to form an alkaline product which is then normally blown with an acidic gas such as CO Overbased or high alkalinity sulfonates can have base numbers of from 30 to as much as 350. Base number is defined in numerical terms equivalent to milligrams of KOH per gram of the material. It is preferred to employ in the present invention an alkaline earth metal sulfonate having a total base number of at least 60 and more preferably one having a total base number of from about 200 to 350 in order to impart rust inhibiting properties to the composition. Specific examples of alkaline earth metal sulfonates that can be employed in the present invention include a barium petroleum sulfonate of about 95 0 molecular weight, calcium C alkyl benzene sulfonate (from benzene alkylated with diisobutylene), barium C alkyl benzene sulfonate (from benzene alkylated with tetraisobutylene), calcium petroleum sulfonate of about 880 molecular weight, calcium salt of sulfonated bottoms from C alkyl benzene (C group from tetrapropylene) overbased to 200 base number, a barium salt of 560 molecular weight petroleum sulfonic acids and the calcium salts of petroleum sulfonic acids of about 450 molecular weight overbased to a base number of about 225.

The metal salts of dialkyl dithiophosphoric acids are well known in the art. It is common practice to prepare dialkyl dithiophosphoric acids by reacting phosphorus pentasulfide with an aliphatic alcohol or a mixture of aliphatic alcohols containing the desired range of alkyl groups in a molar ratio of approximately 4 moles of alcohol for each mole of phosphorus pentasulfide. The acids are then neutralized with an oxide, hydroxide or carbonate of a polyvalent metal, or alternatively with a reactive polyvalent metal salt. The present invention employs polyvalent metal salts of dialkyl dithiophosphoric acids prepared from alcohols having in the range of from about 3 to about 12 carbon atoms. The dialkyl dithiophosphoric acids Whose salts are used in this invention include not only those made from a simple aliphatic alcohol such as ispropyl, normal butyl, normal decyl, etc., but also from mixed aliphatic alcohols including the C or C alcohols obtained by reaction of olefins With carbon monoxide and hydrogen and subsequent hydrogenation of the resultant aldehydes. Also there can be used dithiophosphoric acids obtained from such mixtures as isopropyl alcohol mixed with methyl isobutyl carbinol, a combination of primary amyl alcohol and isobutanol, a combination of mixed amyl alcohols and technical lauryl alcohol, a mixture of isopropyl alcohol and C OX0 alcohol, and the like. Mixed acids obtained by reaction of individual alcohols separately with P 8 ca also be employed in the preparation of the metal salts. The metals employed in making the salts are those of Group II of the Periodic Table including zinc, cadmium, barium and magnesium. Zinc salts are particularly preferred.

The halogenated hydrocarbons employed in the present invention are preferably chlorinated hydrocarbons, although iodinated, fiuorinated, or brominated hydrocar- The weight percents given are on the basis of the total composition. In the above combination of additives the The invention will be better understood when reference is made to the following examples which include a preferred embodiment:

bons may also be used. The halogenated hydrocarbons 5 will have a halogen content within the range of about Example 1 35 to 75 wt. percent, or more preferably from 40 to 70 r wt. percent. The hydrocarbons that are halogenated will A number o gear 011 eomposltlehs were p pf o fe have carbon corrtorrts ranging from about C8 to C24 The 10 as the base oil a solvent refined neutral lubricating orl halogenated hydrocarbons are produced through the direct havlhg vlscoslty 0f 0 SUS at 100 F. The three add1- halogenatiorr of tho hydrocarbons or by other known two components that were employed were a chlorinated means. In the case of chlorinated hydrocarbons it is oohstttoto not less than Po P of the ehtlre both ordinarily necessary only to bubble the chlorine through b o of the three types of addltlvese the hydrocarbon in the liquid State For example ffi 15 mgredrent that is present 1n the least concentration should wax can be heated to a temperature in the range of about P t wax of 50% ChlOrHle ntent, a Zlnc dlalkyl d1 to and chlorine bubbled through it until the thiophosphate and an overbased calcium sulfonate. The desired amount of chlorine has been introduced. Iodina- Chlorinated wax was a Purchased materhfl havihg a Viscotion of hydrocarbons is taught in US. Patent 3,184,413. shy of 200 SUS at F-, and a speclfic gravity of 128 The hydrocarbons that are halogenated include aliphatic at (10-6 P gahoh)- The overbased oalolum hydrocarbons and terpenes. Chlorinated paraffin wax is sulfohato w a Pbrohased motenal whloh was oohooh' particularly preferred, og a paraffin wax of mo1t trate in mineral Oll of a calcium sulfonate derlved from ing point that has been chlorinated to 40% chlorine consyhthotlo atkylotod aromatlo hydrocarbons whotelh the tent or a iffi wax of melting point that has sulfomc acid-s averaged about 420 molecular weight. The been chlorinated to 50% chlorine content. Other examoohoohtrate oo'htalhod 114% ootblbth toptesohtlhg P ples include chlorinated kerosene of 42% chlorine con- Ptoxlmatoly wt Percent oalohhh sultohate and 24 to tent, chlorinated polyisobutylene of 850 molecular weight 25 -l e s- The total base number w about containing 47% chlorine, fiuorinated petrolatum containb mllhgtams of KOH p gram The t y ing 55% fluorine, and iodinated polyisobutylene of 780 thlophosphatewas l a putehtfeed materlal whleh molecular weight containing 70 wt. percent iodine. Poly- 30 slsteo of an h h oohtahhhg about 25 P e halogenated isoparaffins may also be used, including 2 of mineral lubricating Oil and about 75 wt. percent of mm drohloro 4 oh1orornothy1 24 dirrrothy1 porttane and 5 dlalkyl dithiophosphates derived from the treatment ot a t ifl 2 2 4 t i th 1 pontano' mixture of lsobutanol and mixed amyl alcohols with The base oil used in compounding the gear oils of this 2 5 followed y nehtrfihlatlen w t Zlne 0X1deinvention will include any of the base oils that are con- Each of the gear on colhPosltlohS was Prepared by ventionally employed for this service and can thus vary Simple mixing of the additives with the lubricating oil widely in refinement, type and viscosity. They can be debase. In some of the compositions only one additive was rived from a variety of crudes including paraffinic, naphemployed in other compositions two of the additives were thenic, asphaltic or mixed base and they can be treated employed, and in a third set of compositions all three of by any of the conventional refining methods including hy- 40 the additives were employed. The load-carrying ability or". dfogeh e g, aeiel treating extraction, In general, each of the compositions was determined using the Mean the viscosity Wlll be in the range of from about 60 to 3500 Hertz Load Test. SUS at 1000 or o usually t the T g about The Mean Hertz Load Test is designated as Method to 21000 b 353. synthetli l F P- may 6503.1 of Federal Test Method Standard No. 791a, dated fiig g gi 5 &3 g gg gg g 2 22 23 25 in July 27, 1964. Briefly described it involves use of the addition to the combination of additives described above, wen-known 4'ban extreme presspre test apparatus (also other additives for their known functions including anticalled, the Shell t' test machine) Wherem steel ball foam agents, rust inhibtors, corrosion inhibitors, demulsiheld a ow 1s Pressed agamst three other Steel bans fiers, metal deactivators, pour point depressants and the fixed Posmon Screw and the first is like either singly or in combination, rotated against the other balls under set conditions of The additive combination of the present invention will force, temperature and speed of rotation. In this particular be employed in the gear oil composition withi th test the force is gradually increased until welding occurs. centration ranges set forth below: Then the scars on the steel balls are measured, and the Weight percent 5 mean load is calculated from those measurements. concentration The ingredients in each of the compositions tested and Broad Preferred the test results expressed as the Mean Hertz Load, kg., Metalsuuonate 0 3A 0 5 3 are given in the following Table I. The concentration or ifliiegilgggflgig 1 j ach of the additives in the table is the actual amount Higfigelgtglgalgggtfigpon sutfi 0 0 that was present, ignoring the diluent oil when such was present in the additive as supplied.

TABLE I Blend Composition, wt. percent Base oil .A-l A-2 B-l. 13-2 0-1 0-2 D E F G-l 6-2 1 tfitgtae jjjjii "rd $33 i $13 t3 Chlorinated wax 3. 0 3. 0 3. 0 3. 0 3. 0 Base 11 98. 5 97. 0 99. 0 98. 0 97. 0 94. 0 96. 5 95. 5 94. 0 s3. 5 04. 5 Mean Hertz load, kg 20. 3 42. 5 42. 3 36. 3 32. 3 32.8 26. 0 40. 7 41. s 38. 3 52. 0 47. a

l Zinc dialkyl dithiophosphates.

3 Includes oil present in additive concentrate, where applicable.

It will be noted from the test results in Table I that the addition of 1.5 wt. percent of zinc dialkyl dithiophosphate to the base oil produced a significant increase in the Mean Hertz Load, i.e. from 20.3 kg. to 42.5 kg. However when the amount of this additive was doubled to 3 wt. percent there was no further increase in Mean Hertz Load (Blends A-1 and A-2). It is also noted that the addition-of 1 wt. percent of the overbased calcium sulfonate to the same base oil produced a significant increase in Mean Hertz Load from 20.3 kg. to 36.3 kg. Here again doubling the quantity of the additive in the base oil did not result in any further increase in Mean Hertz Load (Blends B-1 and B2). The addition of 3 wt. percent of chlorinated wax containing 50 wt. percent chlorine produced a significant increase in the load reading, from 20.3 kg. to 32.8 kg. However, when the quantity of this additive was doubled there was no further increase in Mean Hertz Load (Blends C-1 and C2).

Looking now at the results obtained when combinations of two of the three ingredients were employed, it will be noted that there was no increase in the Mean Hertz Load when 2 wt. percent of the overbased calcium sulfonate was added to the composition that contained 1.5 wt. percent of the zinc dialkyl dithiophosphate (Blend D) nor when 3 wt. percent of chlorinated wax was added to the blend containing 1.5 wt. percent of zinc dialkyl dithiophosphate (Blend E). While the addition of 2 wt. percent of overbased calcium sulfonate to the oil composition that contained 3 wt. percent of chlorinated wax (Blend F) resulted in some improvement in the load reading, i.e. from 32.8 kg. to 38.3 kg, the value reached was not as high as that when 1.5 wt. percent of zinc dialkyl dithiophosphate was used alone, i.e. 42.5 kg. (Blend A-l).

Referring now to the compositions wherein all three of the components were present, it will be noted that a combination of 1.5 wt. percent of zinc dialkyl dithiophosphate, 2 wt. percent of the overbased calcium sulcfonate and 3 wt. percent of chlorinated wax gave a Mean Hertz Load of 52.0 kg. (G-l which is higher than would be expected by doubling the concentration of the individual additives or by adding one of the additives to the composition containing just one of the other additives. Similarly, one-half as much of the calcium sulfonate was employed in the composition containing all three components (G-Z). A load reading of 47.3 kg. was obtained. Thus there was a surprising synergy in the load-carrying ability of the composition when all three of the additives were present.

Example 2 Additional blends were prepared employing the same base stock, the same chlorinated wax and the same zinc dialkyl dithiophosphate as described in Example 1 but different metal sulfonates. One of these was a 45 wt. percent concentrate in oil of a neutral calcium petroleum sulfonate derived from 450 molecular weight petroleum sulfonic acids. The other was a 45 volume percent concentrate of a high alkalinity barium synthetic sulfonate derived from alkyl benzene sulfonic acids of about 460 molecular weight. The concentrate analyzed 14.5% barium and had a total base number of about 59. Blends containing all three ingredients, i.e. either of the sulfonates just described along with the zinc dialkyl dithiophosphate and the chlorinated wax, were compared with other blends containing only either of the described sulfonates. The Mean Hertz Load data that were obtained and the compositions of each of the blends are given in the following Table II. Here again, the actual concentration of each additive is given, ignoring the diluent oil.

Zine dialkyl dithiophosphates. 2 Includes oil from concentrates.

Example 3 A gear oil blend suitable for use in the present invention is prepared by blending together 73.3 wt. percent of the base oil described in Example 1, 17.4 wt. percent of solvent-deasphalted, solvent-dewaxed Mid-Continent residuum of about 207 SSU viscosity at 210F., 0.5 wt. percent of a pour point depressant comprising wax-alkylated naphthalene, 2.0 wt. percent of a 70 wt. percent concentrate of zinc dialkyl dithiophosphates in lubricating oil, said dialkyl dithiophosphates being derived from a mixture of P 8 treated isopropyl alcohol and P 8 treated methylbutyl carbinol, 3.0 wt. percent of a chlorinated kerosene of 41% chlorine content and 4.0 wt. percent of an overbased calcium sulfonate concentrate comprising 42 wt. percent of diluent oil and the balance the overbased additive. The base number of the calcium sulfonate concentrate is 250 and the calcium sulfonate is derived from petroleum sulfonic acids of about 450 molecular weight.

Example 4 A gear oil composition was prepared by simple mixing of 74 wt. percent of the base oil described in Example 1, 17.5 wt. percent of the residuum described in Example 3, 0.5 wt. percent of the pour point depressant described in Example 3, 1.0 wt. percent sorbitan monooleate rust inhibitor, 2.0 wt. percent of calcium sulfonate concentrate, 3.0 wt. percent of chlorinated paraflin wax and 2.0 wt. percent of zinc dialkyl dithiophosphate concentrate, those last three additives being those described in Example 1. The Mean Hertz Load for this composition was found to be 56.4 kg.

This composition was used to lubricate a farm tractor transmission that contained all of the usual transmission gears together with the final drive gears, which included a spiral bevel pinion and ring gear. The transmission was run with this oil composition at an oil temperature of 180F. with a load that placed 450,000 to 500,000 p.s.i. contact stress on the final drive gears. Under those conditions the run lasted for more than 2.00 hours before failure of the final drive gears, which was considered to be excellent performance.

Thus the compositions of this invention are particularly suitable for lubricating transmissions having gears that are subjected to contact stresses of at least 450,000 pounds per square inch.

It is not intended that the specific examples herein presented limit this invention in any manner.

What is claimed is: a

1. An improved lubricating oil composition capable of serving both as a transmission fluid and as a lubricant for gears subjected to high stresses, which consists essentially of a major proportion of a lubricating oil base and a minor proportion of a load-carrying additive combination of:

A an alkaline earth metal salt of a hydrocarbon sulfonic acid having a molecular weight within the range of about 400 to 900;

B. a zinc salt of a dialkyl dithiophosphoric acid wherein the alkyl groups are within the range of 3 to 12 carbon atoms; and

C. chlorinated parafiin wax having from 35 to 75 weight percent chlorine;

each of said components A, B, and C constituting 7 at least 15 weight percent of the total of A plus B plus C; there being present in said lubricating oil composition, based on the total composition, from about 0.3 to 4 weight percent of A, from about 0.2 to 3 weight percent of B, and from about 0.5 to 10 weight percent of C; the amount of C that is present in said lubricating oil composition being such as to impart to said composition from about 0.2 to 3 weight percent of chlorine. 2. Lubricant as defined by claim 1 wherein said sulfonic acid salt has a total base number of at least 60.

3. Lubricant as defined by claim 1 wherein said sulfonic acid salt is an overbased calcium sulfonate of about 300 total base number.

4. Lubricant as defined by claim 1 wherein said dialkyl dithiophosphoric acid salt is the zinc salt of mixed C -C dialkyl dithiophosphoric acids.

References Cited PATRICK P. GARVIN, Primaiy Examiner.

US. Cl. X.R. 25275