US2827433A - Extreme pressure lubricant composition - Google Patents

Description

United States Patent EXTREME PRESSURE LUBRICANT COMPOSITION Fred B. Fischl, Springfield, and Walter E. Waddey and Fred J. Beyerstedt, Westfield, N. J., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application March 11, 1954 Serial No. 415,692

1 Claim. (Cl. 252-465) The present invention relates to improved extreme pressure lubricant compositions and the like. It particularly relates to oils, greases and other compositions used in heavy duty lubricant service, which contain an improved combination of additive materials.

Briefly, the present invention contemplates a lubricant composition comprising a minor portion of a combination additive including a phosphorus and sulfur-containing hydrocarbon and a sulfur and halogen-containing organic compound.

It is known to compound lubricants with phosphosulfurized hydrocarbons, such as P S -treated mineral lubricating oils to form compositions useful in heavy duty serv ice, particularly where unit loads are exceptionally high, as for example in automotive differential units and hypoid gearing. These compositions are particularly effective in high torque-low speed gear operation, but their performance is from borderline to unsatisfactory in low torque-high speed gear operation. Because this deficiency has been recognized, various procedures have been employed for improving these compositions in this respect. These procedures include treatment of the additive with various substances, blending other types of agents in the composition, and the like. None of the solutions at tempted heretofore have provided a complete answer to the problem. However, in view of the availability and low cost of the phosphosulfurized materials, and their excellence in other respects for this type of service, a satisfactory means for overcoming this deficiency has been needed.

In accordance with this invention, it has been found that the extreme pressure characteristics of lubricants containing phosphosulfurized hydrocarbons is significantly improved, particularly with respect to low torque-high speed operation by the addition thereto of a relatively small amount of a halogen and sulfur-bearing organic compound, such as a halohydrocarbon sulfide. Preferably, in accordance with this invention, the concentration of the phosphosulfurized hydrocarbon is substantially in excess of that of the halogen and sulfur-containing compound in order to also insure satisfactory high torque-low speed performance.

It has been found that lubricants compounded with these two types of additives demonstrate unexpectedly superior extreme pressure performance in contrast to the predicted performance based on the effect exerted by each of the additives when used alone in the same lubricant base stock. Furthermore, the finished compositions compounded in accordance with this invention are superior in high speed-low torque extreme pressure service, and pass the rigid requirements imposed by U. S. Government specifications in this test.

'i'he results obtained in the practice of this invention are unexpected from several standpoints. While it is wellknown in the art to employ various halogenated organic compounds as additives in extreme pressure service, it was found that typical members of this class do not improve to meet the high speed-low torque ice test, either when the halogenated materials were used alone or in combination with phosphosulfurized hydrocarbons. It is indeed surprising to find that halogenated compounds containing sulfur contributed a synergistic extreme pressure improvement to the phosphosulfurized hydrocarbon, particularly when the former material is used in concentrations at which it normally imparts very little or no exheme pressure properties in ordinary lubricant base stocks. The reasons for these unexpected results cannot be explained at this time.

In the first step of the preparation of the phosphosulfurized additives employed in accordance with the present invention, a sulfide of phosphorus is reacted with a hydrocarbon material. The sulfide of phosphorus which can be employed includes P 8 P 8 P 8 P 5 or other phosphorus sulfide, and is preferably phosphorus pentasulfide (P 5 Mixtures of two or more phosphorus sulfides may also be employed as well as mixtures of elemental phosphorus and sulfur.

The hydrocarbon materials which may be reacted with a phosphorus sulfide may be parafims, olefins, or olefin polymers, diolefins, acetylenes, aromatics or alkyl aromatics, cyclic aliphatics, petroleum fractions, such as lubricating oil fractions, petrolatums, waxes, cracked cycle stocks, or condensation products of petroleum fractions, solvent extracts of petroleum fractions, etc.

As examples of monoolefins may be mentioned isobutylene, decene, dodecene, cetene (C octadecene (C cerotene (C melene (C olefinic extracts from gasoline or gasoline itself, cracked cycle stocks and polymers thereof, resin oils from crude oil, hydrocarbon coil resins, cracked waxes, dehydrohalogenated chlorinated waxes, and any mixed high molecular weight alkenes obtained by cracking petroleum oils.

Another class of suitable olefinic materials are the monoolefin polymers, in which the molecular weight ranges from to 50,000, preferably from about 250 to about 10,000. These polymers may be obtained by the polymerization of low molecular weight monoolefinic hydrocarbons, such as ethylene, propylene, butylene, isobutylene, normal and isoamylenes, or hexenes, or by the copolymerization of any combination of the above monoolefinic materials.

Another class of hydrocarbons which may be employed in a similar manner are aromatic hydrocarbons, such as benzene, naphthalene, anthracene, toluene, xylene, diphenyl, and the like, as well as aromatic hydrocarbons having alkyl substituents and aliphatic hydrocarbons having aryl substituents.

Another type of hydrocarbon material which may be similarly employed is a resin-like oil which has a molecular weight of from about 1,000 to 2,000 or higher, obtained preferably from a paratfinic oil which has been dewaxed and which is then treated with a liquified normally gaseous hydrocarbon, e. g. propane, to precipitate a heavy propane-insoluble fraction. The latter is a substantially wax-free and asphalt-free product having a Saybolt viscosity at 210 F. of about 1,000 to about 4,000 seconds or more.

The phosphorus sulfide-hydrocarbon reaction product may be readily obtained by reacting the phosphorus sulfide with the hydrocarbon at a temperature of about 200 F. to about 600 F., and preferably from about 300 F. to about 550 F., using from about 5% to about 25 preferably about 10% to about 20% by weight of phosphorus sulfide based on hydrocarbon. It is advantageous to maintain a non-oxidizing atmosphere, such as an atmosphere of nitrogen, above the reaction mixture. Usually it is desirable to use an amount of the phosphorus sulfide that will completely react with the hydrocarbon so that no further purification becomes necessary. In the case of monoolefin polymers the preferred ratio is one molecular asaraes proportion of the sulfide ofphosphorus to two to five molecular proportions of polymer. In such case the reaction is continued until all or substantially all of the phosphorus sulfide has reacted. The reaction timeis not critical, and thetime required. to cause the maximum amount. of phosphorus sulfide to react will vary with the temperature. A reaction time of two to ten hoursisfrequently necessary.

Although the resulting acidic phosphosulfurized product may be used as such, it is preferred to refine it further in order to improve odor, anti-corrosive, extreme pres sure, detergency, stability and other properties. Such refining procedures are well known to the art, and include x of a soluble metal petroleum sulfonate and a metal alkyl phenol sulfide. The sulfonates may be an alkali or alkaline earth salt, including the lithium, sodium, potassium, calcium, strontium, and barium salts of the hydrocarbon sulfonates prepared by,the treatment of petroleum oils with strong sulfuric acid followed, for example, by treatment with a base of the metal. The alkali or alkaline earth metal sulfonates are most commonly used, but petroleum sulfonates of other metals may be-used if they are soluble in the lubricant in the small concentrations required in the practice of the present invention. Mixblowing with steam, alcohols, phenols, and the like at elevated temperature of about 200. to 60.0.P., reacting with various metal and ashless basic reacting .agents, treating with olefiuic hydrocarbons, etcg Thus, metallic treating agentsincludethe alkalimetal and alkaline earth metal oxides, hydroxides, hydridesand the like, specifically such compounds .of potassium, so-

dium, barium, and calcium.

Suitable ashless treating agents include nitrogcnbases such as ammonia, and organic nitrogen bases such as amines andarnine derivatives, guanidines and theirderivatives, morpholine, pyridine, quinoline .and like substances. Guanidine andits derivatives are particularly useful, the symmetrical tri-substituted compounds, such as trialkyl and trinaphthenyl guanidines and the like being usefuh Other useful compounds include the biguanides,

' esterify or combine with the titratableacidity of the phosphosulfurized material, Completely neutralized materials are usually preferred.

A particularly desirable method for reducing H 8 evolution and improving odor is that of following the teachings of U. S. Pate t 2,640,053 in which thephosphosulfurized hydrocarbon, is treated with about 0.1 to 50% of its weight of an olefinic hydrocarbon.

tures of the various sulfonates may be employed 'if desired. Preferably thesodium and calciumsulfonates are used. The most effective sulfonates are those having relatively high molecular weights such as from about 400 for monovalent to about 1100 for divalent salts. The sulfonates are generally added to the phosphosulfurized additive in concentrations ranging from 0.02 to 1.0 weight percent with preferred concentrationsranging from 0.05 to 0.3.weight percent. a

The alkaline earth metal salts of alkyl phenol. sulfides include those in which the alkaline earth metalsare calcium, barium, strontium, and magnesium. The presence of at least one alkyl group in the benzene. nucleus is usually desirable to impart oil solubility to. the compound. The alkyl group. may contain from 4 to 12 or more carbon atoms and may be straight chain or branched. From one to four. sulfur atoms mayinterconnect benzene nuclei. The. sulfide may contain only one alkaline earth metal or may have a mixture 'of at least two alkaline earth metals in the same molecule. Barium is generally the preferred metal, calcium being second choice, as a rule. 'The concentration of the alkyl phenol sulfide saltis usually in the range of 0.05 to 2.0%,

The preferred olefinic hydrocarbon materials to be reacted with the phosphosulfuriz ed material includes the terpenes, such as turpentine, dipentene, alpha-pinene, terpinene, terpineol, and'the like and such olefinic hydrocarbons as isobutylene, diisobutylenq'and the more reactive of the analogous aliphatic and cycloaliphatic materia1s. 7 V

In particular, a product sold commercially as Dipentene consisting primarily of a mixture of true dipentene with its isomers and 'minor proportions of related products, is used in proportions of about 2 to 30% by weight based on the material to be treated, the ingredients being mixed together and heated at a suitable temperature until the product is stabilized. Preferred proportions are 5 to 15% by weight. Stability is indicated by reduced evolution of H 5 gas at'ordinary temperatures and at the invention contemplates a range of soaking temperatures from as low as 60 to as high as about 400 F.

The soaking timemay be from 1 to hours, depending upon the tendency to evolve H 8 gas and upon'the degree of stability desired.

. It may also be desired to improve-the stability ofthe phosphesulfurizedproduct and to reduce its sludge-formehen'sts s by; inhibi n it w h small: am v application.

a.mono-, or di-; orpoly'sulfide.

derivatives, such as for example, the .chlorinatedand i with a metal sulfide to form usefulgmixed preferably in the range of' about 0.1 to 1.0% by weight based on the treated phosphosulfurized oil. The weight ratio of petroleum sulfonate to alkylphenol sulfide salt ispreferably in the rangeof 1:1 to 1:3.

The phosphosulfurized additive maybe'used in various proportions in lubricants depending upon the specific .In thelubrication of automotive hypoid gears, a concentration of about 3 to .20 weight percent, preferably 5 to 15% and especially 8 to 12%,.based on the total lubricant isused to impart substantial high torque extreme. pressure properties to the lubricant.

.The sulfurand halogen-containing organic compound used in combination with the phosphosulfurized hydrocarbon is preferably a halo-hydrocarbon sulfide, such as Since the aromatic brominatedalkaryl sulfides, are generally more stable and therefore less corrosive .than the sulfohalogenated such as those formed by treating 'olefins, parafiins, naphthenes and the like, with-sulfur halides may be used.

'Thus, the reaction product of sulfur chloride and paraffin 'wax, or mixtures of 'wax and kerosene may be employed.

Other useful materials maybe prepared by treating chlorinated hydrocarbons, such as chlorinated kerosenes, gas oils, mineral lubricating oil distillates, waxes, etc., with an inorganic polysulfide such as a sodium' polysulfide whereby a portion of the chlorine is replaced with sulfur to form chlorohydro'carbon sulfides. Aromatic hydrocarbons, such asalkyl aromatics, may be prepared by prior artprocesses in which halogen is first introduced into the benzeneling, and then into the alkyl'groups;

' Twoof the resulting molecules may. then be. joined by replacing the .alkyl halogen. atoms with one or more 7 sulfur, atoms by treatment with an alkali; metal sulfide; "to form theihaloaralkyl'sulfide. c p

@In another procedure, a mixture of henzyl chlorides and chlorobenzyl chlorides, for example, may be'reaqto chloroparamn war Polysulfidc, dibromodiphenyl disulfide, dichlorodibenzylsullide, chlorodimetlrylbenzyi disulfide, and the like. The halogen-containing dibenzyl disulfides, such as chlorodibenzyl disulfide, are especially preferred.

The amount of the chlorine and sulfur-containing compound used in conjunction with the primary additive may vary widely. Generally, it is used in amounts ranging from about 0.1 to 10% by weight based on the total oil, preferably about 0.3 to and especially 0.5 to 2.0% at concentrations less than the concentration of phosphosulfurized hydrocarbon used. Thus, weight ratios of phosphosulfurized hydrocarbon to the halogenand sulfur-containing hydrocarbon in the range of 2:1 to 30:1, especially 5:1 to 20:1, are useful.

The additives of the present invention may be employed not only in ordinary oil-base lubricants, but especially find application in heavy duty types of lubricants that have been compounded with detergent additives such as metal soaps and the like, dyes, pour depressors, antioxidants, viscosity index improvers, thickeners, corrosion inhibitors, etc. Suitable base stocks include animal, vegetable and mineral and synthetic oils. Preferably, they are mineral oils that have been refined by usual procedures, including acid and/or alkali treatment, solvent extraction, etc., although other oleaginous base stocks may be used.

For example, synthetic oils, including polymerized olefins, cracking coil tar fractions, animal, vegetable or fish oils or their hydrogenated products, etc., may be used alone or in admixture with mineral oils. Synthetic oils of the ester, polyester, polyether and related types may be used. These include di-Z-ethyl-hexyl sebacate, dibasic acid esters, polyalkylene oxides, etc. Especially suitable, however, are the high viscosity mineral oils having utility in extreme pressure service such as those having SSU viscosities at 210 F. of 50 to 150 or higher, and soap thickened greases prepared from mineral oils and the like.

Various modes of practicing this invention are specifically illustrated in the following examples:

EXAMPLES I. Description of additives Additive A.-A deasphalted, dewaxed, acidand claytreated Panhandle mineral oil bright stock having an S. U. S. viscosity of 170 at 210 F. was treated in a nitrogen atmosphere with about 17% by weight, based on the oil, of P 5 for about hours at a temperature of about 425 F. The product was filtered, and was then treated with 9.5 Weight percent of commercial dipentene and 1.0 weight percent of a stabilizer at a temperature of about 380 F. with stirring for one hour.

The commercial dipentene employed contained about 31% dipentene, 39% terpinolene, 6% alpha-pinene, 10% para-cymene, 7% alpha terpeneol, 5% 2,4(8)-p-methadiene, and 2% residue.

The stabilizer employed was a blend containing about 33 weight percent of sodium petroleum sulfonate having a molecular weight of about 500 and 67 weight percent of barium tert.-octyl phenol sulfide resin.

The treated product, after cooling to room temperature, was designated as Additive A. It had a phosphorus content of 3 weight percent, a sulfur content of 5.9 weight percent, and an S. U. S. viscosity at 210 F. of about 288.

Additive B.This additive consisted of commercial chlorodibenzyl disulfide containing about 20 weight percent sulfur and 13 weight percent chlorine.

Additive C.-This material was a chlorinated camphene containing about 65 weight percent chlorine.

about 65 weight percent chlorine.

II. Description of oil base stocks Base Stock I.This was an SAE grade gear oil consisting of about 47 weight percent of a deasphalted Mid- Continent crude residuum and 53 weight percent of a Mid-Continent acid-treated lubricating oil distillate. This mineral oil blend had an SUS viscosity of about 922 at F. and about 81 at 210 F.

Base Stock lI.-This was also an SAE 90-grade mineral oil prepared from solvent extracted Mid-Continent lubricating oils, and had SUS viscosities at 100 and 210 F. of about 864 and 79, respectively.

Base Stock lIl.This was another SAE 90-grade mineral oil similar to Base Stock 11. It had SUS viscosities at 100 and 210 F. of about 847 and 77, respectively.

111. SAE test results Oil blends containing either Additives A or B or a mixture of the two in Base Stock 1 were tested in the SAE extreme pressure testing machine according to the procedure designated CRC-L17. The machine was operated at 1000 R. P. M. at a 14.721 rubbing ratio on the bearing cups. The minimum pressure that can be applied under these conditions is 10-15 scale pounds. In carrying out the test, pressure is increased until failure of the cups is obtained. The maximum reading before failure is designated as the SAE machine rating. The re sults of the tests are shown below in Table I.

TABLE I.ADDITIVE IN OIL BLEND, WT. PERCENT Additive A Additive B SAE Test Oil Blend (PzSs-trt. Ohlorodiben- Results, Scale,

Hydrocarbon) zyldlsulfide) Pounds 1 X Average of two runs. 2 100% Base Stock 1.

The addition of 1% of the chlorodibenzylsulfide to the oil did not show a measurable improvement in the extreme pressure properties of the base oil. The addition of 10% of the phosphosulfurized hydrocarbon effected a substantial improvement, but an unexpected improvement of over 50 scale pounds was obtained by using a mixture of 9% phosphosulfurized hydrocarbon and 1% of the chlorodibenzyl-disulfide. This degree of improvement is all the more extraordinary in view of the fact that the sulfur and chlorine compound in the concentration used was ineffective when used alone. At most, the individual performance of the additives would indicate that the two additives together would impart an improvement of no more than that obtained by the addition of additive A alone.

1V. Full scale gear tests These tests were carried out on various blends of the additives and oil base stocks described in Examples I and 11, above. The tests, designated as the High Speed- Low Torque Axle Test, CRO-L-19, and the High Torque- Low Speed Axle Test, CRC-L-20, were conducted in accordance with the U. S. Ordnance Specification MIL- L-2105. The base oils are incapable of passing either of these stringent tests. The oils containing photosulfurized hydrocarbons have in general excellent L-20 characteristics, but L-19 performance is frequently borderline or unsatisfactory. On the other hand, the conventional halogenated extreme pressure additives are generally either deficient in L-20 performance or are tooo corrosive to be used in high quality gear oils. In general, oils containing the conventional halogenated organic compounds -are definitely deficient -=in L- l9 perfoifirnance, ei-

ther, with or without the addition ofphosphosulfnrized hydrocarbons' However, the cor'nbinationof the phosphosulfurized additive and thesulfur andhalogen-containing hydrocarbon was found to impart consistently superior L-19 performance to a variety of gear lubricants throttle decelerationffrom to'60VM. .P. H. 'After ten such cycles, the gear teeth are'jjinspectedfor scoring. If ,no scoring'is noted,"the oilgpass'esj the test, whereas the oil fails the gear teeth scoring islight 'or severe.

An oil is borderline if the scoring is slight.

TABLE II V SAE 90 V y Wt. Full-Scale Gear Oil Oil Additives used in Oil Percent Test 7 lend Base Blend, Weight Percent Chlorine Stock V i in Oil 7 I I None Nil Fail-.. Fail. I A (phosphosuliurized Nil do Pass. I Hydrocarbon). p 7

6 I A, 1% B (Ohlorodi 0.13 Pass" Do.

benzyl disulfide). 7 I 7.4% A; 0.6% Z inc'stea- 1.3 Fail"; Not

rate 2.0% C (Chlorine Tested i fired Qamp r t I 9.5% A, 0.5% D (Penta- 0.33 do 'Do.

chlorophenol). I 9.7% A, 0.3% E (Trichlo- 0.20 do.' Do. ro Acetie Acid) 3H 9% A, 1% B- 0.13 *Pass Pass. 2 III 10%"A Nil Fail-.- Do. 12;.-.1 1H -9%-A-,-1%-B-;-. *0.-13 Pass Do.

1 Added as corrosion inhibitor to offset corrosivity-ot Additive C. 1 Base 0115 alone fail both L-19 and L-20 tests. M s

I With reference to.Table 11,. it is observed-that alLolf the blends containing both. Additives'..A..and B:.pass e i both Igeartests whereasoils containing only Additive A failed the L 19 testbut passed the L-20 test. "Further.-

5 more, thegoils containing .Additives :A: and B were .not

corrosiveto metals and: metLsat-isfactorily, other specification requirements imposed .onjsuch gear: oils. V

The combination of sulfur-free, halogen-containing organiccornpounds with therphosphosulfurized hydrocar- -1'0 hon 'didlnotimprovetthexoils is'uflicientlyfto meet the L19 test, even though the: halogen. concentration, in the oil blend-was from almost 2 to .10 times. greater than that in the oils f ofthe' :present invention. i *In this. connection, the chlorinated aliphatic compounds impartcorl 15 ros'ive characteristics to the finished .oi1s,-.and 'the' .HSGZOf an auxiliary corrosioninhibitorwas neededinoil blend'7.

What isbl'aimedi's: T. An improved eXtremepre'ssure lubricating oiLwhich comprisessa-mineral oil having. an SUS viscosity at 20 21051 inthe-rangeof to ;8 to .12 wt. percent of a dipentene-treatedreaction product 'of amineral lubricatingoil and P S formed at a temperature in therange of 200 to" 600 K, and 0.5 to 2 wt. percentof 'chlorodibenzyldisulfide,-- the weight. ratio of said .dipen- -25 tene-treated reaction product to said disulfide being in the range o f 5:1 try-20:1.

References Cited in the: file of this patent UNITED STATES PATENTS Prutton Apr. 4, 1939 2,450,405 Berger et a1. Oct. 5, 1948 2,712,528 Hill July 5, 1955