US3196110A - Materials useful as lubricating oil additives - Google Patents

Description

United States Patent search and Engineering Company, a corporation of Delaware No Drawing. Filed Mar. 12, 1962, Ser. No. 79,238 20 Claims. (Ci. 25232.7)

This invention relates to new materials which are useful as lubricating oil additives in automatic transmission fluids, rear axle lubricants, etc., and which are particularly useful in transaxle systems. Particularly, the invention relates to a material obtained by reacting an alcohol ester of a mercapto acid with a lead oxide in the presence of an ashless oil-soluble phosphosulfurized hydrocarbon material, which product is suitable for use as an extreme pressure (E.P.) additive in lubricating compositions.

Recently, in certain makes of automobiles the transmission and the rear axle systems have been combined into a single mechanical unit located proximate the rear wheels of the automobile. This combined unit is known as a transaxle unit and is primarily designed to eliminate the conventional hump extending along the floor of the automobile. The combined mechanism requires a lubricant which has the properties of both an automatic transmission fluid and a rear axle lubricant. The lubricant, therefore, must be extremely table to heat and oxidation, have good antiwear properties and at the same time have the extreme pressure properties required for the hypoid gears associated with the rear axle. In addition to these basic properties, a transaxle lubricant must be inert to a Wide variety of materials used in the construction of the combined units. The problem of formulating such a lubricant has been particularly difficult since the conventional extreme pressure additives previously used in rear axle lubricants tend to attack the rubber seals and other parts of the transmission system. On the other hand, many of the mild extreme pressure additives used in transmission oils were insufiicient in their extreme pressure properties to impart the desired degree of extreme pressure properties suitable for the rear axle unit.

It has now been found that a supeior extreme pressure additive obtained by reacting an alcohol ester of a mercapto acid with a lead oxide, in the presence of an ashless oil-soluble phosphosulfurized hydrocarbon material, will solve the above-mentioned problems. A lubricating composition containing this additive exhibits good extreme pressure properties and is not deleterious to the various parts of the lubricated system.

While the exact nature of the reaction product is not quite clear, the reaction product is known to contain lead, sulfur and phosphorus in varying amounts, depending upon the proportions and ratios of the reactants. It is also known that certain proportions and ratios are critical to the formation of a successful reaction product, and that the omission of any one of the initial ingredients will result in an unsuitable product. For example, the omission of the phosphosulfurized hydrocarbon material from the reaction mixture produces an oil-insoluble reaction product which is unsuited for use as an extreme pressure agent. Similarly, the omission of the mercapto acid ester also produces an oil-insoluble reaction product, which product is highly deficient in lead content,

In general, any lead oxide is operable in the invention although PbO is the preferred oxide.

The mercapto acid esters operable in the invention are those having the general formula:

HS(CH ),,COOR wherein n is an integer of l to 4 and R represents an alkyl radical of a C to C alcohol, e.g., a C to C alcohol.

Acids used in preparing the esters include mercapto acetic acid (thiovanic acid), mercapto propi-onic acid, etc. Alcohols which can be used include the straight and branched chain aliphatic alcohols such as n-butanol, C Oxo alcohol, lauryl alcohol, stearyl alcohol, etc. The alcohols which are especially preferred are the high molecular Weight straight chain alcohols, e.g., tallow alcohol, for the reason that the resulting reaction products exhibit better E.P. properties. Alcohols lower than C, produce esters with objectionable odor.

Esters of the above type are readily prepared by straightforward esterification techniques, with or Without catalyst, and preferably using a solvent such as hexane as a water-entraining agent. If desired, the solvent-ester mixture may be washed with water and neutralized with sodium bicarbonate solution (if an acid catalyst such as NaHSO -H O is used), followed by more water washing before stripping and filtering.

While the above type of mercapto acid ester has been found particularly effective, other similar sulfur-containing esters have been found inelfective. Thus, in order to obtain the desired extreme pressure properties, it appears desirable that the sulfur atom of the ester compound be located proximate the end or" the molecule. For example, esters prepared from materials having the sulfur in the center portion of the molecule, such as Kromfax glycols (plus fatty acids) having the formula:

HOCH CH SCH CH OH While having excellent oxidation stability and good rubber resistance, have considerably less extreme pressure properties. As a further example, ester disulfides are not entirely satisfactory. An ester disulfide of mercapto acetic acid having the formula:

ROOCH CSSCH C0OR can be prepared by reacting the ester of chloroacetic acid with Na S. The use of this ester disulfide with the lead oxide and phosphosulfurized hydrocarbon material to form a reaction product similar to that of the invention results in an extremely low utilization of lead, thereby making such use impractical for an extreme pressure agent since a certain proportion of lead in the product of the invention appears to be essential to obtain extreme pressure properties.

It has also been observed that the use of the mercapto acid, instead of the ester, is not suitable in that it results in an unstable and oil-insoluble reaction product as Well as a very low lead utilization. This is especially surprising in view of the two possible reactive sites for the lead to attach itself to the acid, -i.e., carboxyl and mercapto groups,

The ashless oil-soluble phosphosulfurized hydrocarbon materials, which are utilized in the compositions of this invention, are prepared by reacting a sulfide of phosphorus, for example, P 8 with a suitable hydrocarbon so as to form an oil-soluble material. The preferred hydrocarbon starting materials are polymers of C to C olefins prepared by the polymerization or copolymerization of low molecular weight olefins and diolefins such as ethylene, propylene, butylene, isobutylene, butadiene, isoprene, and cyclopentadiene. Polymers of monoolefins wherein the molecular weight (Staudinger) ranges from about 400 to about 20,000 and preferably ranges from about 400 to about 10,000, e.g., 700 to 2,000, are particularly eflfective in preparing the phosphosulfurized hydrocarbons of the invention. The most commonly employed polyolefin is a polyisobutylene or polybutene hav ing an average molecular weight (Staudinger) of about 500 to 1200, e.g., about 900.

acted with the phosphosulfurized hydrocarbon.

the phosphosulfurized hydrocarbon less than 1.5%.

Preferably, the phosphosulfurized hydrocarbon is prepared by reacting approximately four moles of hydrocarbon base stock (e.g., a polyolefin) per mole of phosphorus penta'sulfide. A slight excess of phosphorus pentasulfide over the 1 to 4 mole ratio can be used to insure complete phosphosu-lfurization. The phosphosulfurization reaction is generally conducted under anhydrous conditions at temperatures of 150 to 600 F. for a period in the range of 0.5 to 15 hours. A very slight amount of an alkyl phenol or alkyl phenol, sulfide, preferably in th range of 0.001 to 1.0 percent by weight, can be added as a catalyst in the phosphosulfurization reaction. It has also proven very useful to treat or blow the phosphosulfurized product with an inert gas, such as nitrogen, for a period of 10 minutes to 2 hours to aid in reducing subsequent hydrogen sulfide evolution and its corresponding odor. The preparation of phosphosulfurized hydrocarbons and the use of catalysts in the phosphosulfurization reaction are more fully described in U.S. Patent The resulting acidic phosphosulfurized hydrocarbon may be utilized without further modification, or may be further neutralized by the following procedures.

.with a C -C alkylene oxide, preferably ethylene oxide,

although higher alkylene oxides may be used. The a1- koxylation may be carried out at elevated temperature, e.g., 230-300 F., in the presence of a suitable catalyst, such as a boron trifluoride, ether complex, or caustic soda, for an extended period of time, e.g., 1 to 5 hours, until the degree of alkoxylation desired has been achieved. Thus, from 1 to 10 moles of alkylene oxide may be reacted with one mole of phosphosulfurized hydrocarbon. The stability of the final product may be increased by steam-stripping the phosphosulfurized product prior to reaction with the alkylene oxide.

The phosphosulfurized product may also be neutralized with an amide of carbonic acid, which may alternatively be defined as a derivative of carbamic acid. Examples of such derivatives are carbamic compounds represented by the general formula:

wherein R is hydrogen or an alkyl group containing 1 to 20 carbon atoms. Specific compounds which may be used are urethane and urea, or the corresponding thio derivatives, e.g., thiourea and ammonium carbamate.

The reaction with the carbonic acid amide may be carried out at elevated temperatures from 250 F. to 350 -F., preferably between 285 and 340 F. The amide is gradually added to the reacting mass over a period of time from A to 10 hours, preferably from 1 t 3 hours, until the required amount of amide has been re- Preferably, from 1.5 to 3 moles of amide are used per mole of phosphosulfurized product.

Greater storage stability is provided for the final additive if the phosphosulfurized hydrocarbon is steamstripped prior to reaction with the amide. Thus, the phosphosulfurized hydrocarbon may be contacted with steam at a temperature of about 285 to 325 F. for a period of time to bring the acid number of the mixture to a value preferably above 25, or the sulfur content of For example, the steaming may be continued for from 2 to 5 hours, while the quantity of steam used is preferably be tween to by weight of the phosphosulfurized hydrocarb on.

Since in commerc1al practice, the phosphosulfurized phosphosulfurized polyisobutylene in 32 wt. percent minratio lies between 1.021 and 1.5:1.

eral lubricating oil, all of the following ranges are based upon a solution of 68 wt. percent phosphosulfurized polyisobutylene in oil. It is understood, however, that if a different concentration of said polyisobutylene in oil is used, or if 100% active phosphosulfurized polyisobutylene is used, then of course, the relative proportions of reaction ingredients are accordingly changed.

In accordance with the present invention, to 97 weight percent, preferably to weight percent, of a mixture of the mercapto acid ester and oil solution of the phosphosulfurized hydrocarbon material (68 wt. percent in mineral oil) are preferably heated to a temperature between 200 and 450 F., preferably 280 to 370 F., with stirring. The mineral oil, which is used merely for convenience purposes to produce a material which is easier to handle, has been shown not to enter into the reaction. While the weight ratio of the mercapto acid ester to the phosphosulfurized hydrocarbon mineral oil solution may range from 0.2:1 to 2.521,, the preferred 3 to 25 weight percent, preferably 5 to 15 weight percent, lead oxide is then preferably added in small increments over a period of about 10 to 180 minutes to the above hot mixture so as to maintain the temperature within the desired range. The above weight percents are based on the total weight of the resulting mixture of the ingredients. The solid lead oxide readily dissolves and the resulting solution is maintained between the above temperatures for a sufiicient time so as to effect a complete reaction, e.g. 10 to 240 minutes, preferably to minutes. The resulting solution is then preferably filtered hot through a diatomaceous earth or other filtering means to remove insoluble material. Upon cooling, the solution forms a semi-solid material which easily and completely dissolves in oil and which contains 2.5 to 20 weight percent, preferably 4 to 12 weight percent lead; 2 to 15 weight percent, preferably 3 to 10 weight percent sulfur; and .2 to 2.0 weight percent, perferably .5 to 1.5 weight percent phosphorus.

Certain variations in the above procedure can be uti- 'lized, although optimum lead utilization (i.e., the ratio of lead in the final product to the initial lead added) and oil solubility of the final product is attained using the above procedure and the preferred quantities of reactants. For example, the lead oxide may be added at temperatures below 200 F. In such instance, the lead oxide may not dissolve as readily and longer reaction times may be necessary to achieve a practical utilization of the lead. Furthermore, the reaction temperature and reaction time are interdependent, i.e., a low reaction temperature, while impractical with a short reaction time, may be successfully utilized by increasing the reaction time. Additionally, the weight percent of lead om'de added will also affect the lead utilization. While any weight percent Within the above-stated range will produce a suitable product, the preferred ranges, i.e. 5 to 15 weight percent lead oxide, will result in an optimum lead utilization. Similarly, the use of the preferred ratios of the mercapto acid ester to the phosphosulfurized hydrocarbon material solution will generally ensure optimum lead utilization and oil solubility, whereas the use of the other ratios, while still operable, may be below the optimum.

The finished reaction product, being oil soluble, can then be utilized as an additive in a suitable base oil. The additive is merely blended with the base oil in the required amount.

The base oil for transmission or transaxle use is preferably a mineral lubricating oil having a viscosity of about 75 to 500 SUS at 100 F. and a viscosity index of about 80 to 120. Preferred mineral oil are those having viscosities of 100 to 200 SUS at 100 F. and viscosity indexes of 90 to 105. These mineral oils may be derived from either paraffinic or naphthenic crude oils which are refined by conventional mehods. If the additive is to be used for a heavy industrial gear oil ape 5 plication, however, heavy oils, asphalts, waxes, etc. may be used to thicken the product.

The additives of the invention are also useful in synthetic oil compositions such as polysilicone oils, diester oils such as di-Z-ethylhexyl sebacate, glycol ether oils such as the Ucon oils, formals, polycarbonates, etc.

The final oil compositions will generally contain 1 to 20 weight percent of the additive, based on the finished composition, depending on the end use of the oil. Preferred compositions will contain about 2 to 10 weight percent of the additive. oil may also be prepared.

The above compositions may also contain various other additives such as thickeners, viscosity index improvers, pour point depressants, antioxidants, rust inhibitors, other extreme pressure additives, antiwear additives, etc.

For automotive use, a viscosity index improver is generally utilized in amounts of .5 to 10.0 weight percent, preferably 1.0 to 5.0 weight percent of active ingredient, based on the total weight of the finished composition. The viscosity index improvers can be used to thicken low viscosity base oils to the preferred viscosity for a transaxle lubricant (e.g., 150 to 300 SUS at 100 F.) These viscosity index improvers are long-chained polymers of about 10,000 to 1,000,000 Staudinger molecular weight. Examples of such materials include polyisobutylene; copolymers of vinyl acetate with dialkyl fumarates or maleates; polymethacrylates; etc.

The invention will be further understood by the following examples which include a preferred form of the invention.

EXAMPLE 1-PREPARATION OF THE REACTION PRODUCTS OF THE INVENTION Part IPrepztratin of tallow mercapto acetate ester from tallow alcohol and mercapto acetic acid (thiovam'c acid) An ester of the invention was prepared on a pilot plant scale. A commercial alcohol derived from the reduction of tallow fatty acids was used, which is manufactured by Archer Daniels Midland Corporation and known as Adol 63. It consists roughly on a weight basis of about /3 straight chain C saturated alcohol and about /2. C saturated alcohol and is a solid with a melting point of 55 C. In the preparation of the ester, 5 gallons of hexane was charged to a 30-gal lon Dowtherrn jacketed glasslined reaction kettle. A 50-lb. bag of tallow alcohol was added in chunks, and low heat turned on the jacket. After 35 minutes the alcohol had dissolved in the hexane solvent, and the temperature rose to 107 F. in the kettle. The stirrer was turned on, 17.8 pounds of thiovanic acid was added and the vacuum adjusted to prevent fumes. Heat was increased slowly for one hour until the hexane started a very gentle reflux (145 F. kettle temperature). This reflux was held for 24 hours while the Water of reaction (1621 g.) was trapped off. Then the reflux return was cut off and the hexane was drawn off over a period of about 30 minutes. Vacuum and heat were gradually applied and the remainder of the hexane was removed over an additional one and one-half hours as the kettle contents reached 220 F. under 29.3" Hg vacuum. The product was cooled to about 150 F. and drawn through a paper filter into pails for storage. The yield was 64.17

pounds of crude ester containing 9.5 weight percent sulfur.

Part IIReacti0n product A Reaction product A was prepared by heating 140 grams of the tallow mercapto acetate ester containing 9.5 weight percent S (as previously described), and 93.5 grams of a neutral mineral oil solution containing 68 weight percent of a phosphosulfurized polyisobutylene, said solution containing 5.2% S and 2.7% P, based on the total weight of said solution, to 325 F. with stirring. The mineral oil had a viscosity of 150 SUS at 100 F.

Concentrates of the additive in.

The tallow mercapto acetate ester melted at about F. and formed a uniform solution with the phosphosulfurized polyisobutylene as the mixture wa further heated. 22.6 grams of lead oxide (PbO) which contained 92.5% Pb was then incrementally added to the mixture over a one-hour period, with stirring, while the temperature was maintained at 325 F. The lead oxide readily dissolved and the resulting black solution was aged, with stirring, for an additional hour at 325 F. The black solution was then filtered hot (325 F.) through Hyfio, a commercial diatomaceous earth, and then allowed to cool. The filter medium showed negligible amounts of solid black material. The black filtrate, upon cooling to room temperature, formed a semi-solid black final product which was easily and completely soluble in oil. Analysis of the final product showed that it contained 6.7 weight percent Pb, 6.27 weight percent S, and .98 weight percent P. The original weight percents of these ingredients in the reaction mass were 8.1 weight percent Pb, 7.1 weight percent S, and .98 weight percent P. These figures represent utilizations of 82% for Pb, 88% for S, and for P.

The phosphosulfurized polyisobutylene was prepared by treating a polyisobutylene of about 900 molecular weight (Staudinger) with about 10% by weight of P 8 for about eight hours at a temperature from 180 C. to 220 C. to form an ashless, oil-soluble acidic hydrocarbon product.

EXAMPLE 2EFFECT OF VARIATIONS IN THE PREPARATION OF THE REACTION PRODUCTS OF THE INVENTION Part IReacti0n products B and C In order to determine the effect of eliminating one of the reactants, the following reaction products were prepared using the procedure of Example 1, with the following exceptions.

Reaction product B was prepared using the same amounts of reactants as described in Example 1, except that the ta-llcw mercapto acetate ester was eliminated and replaced by an equal amount of a solvent neutral mineral lubricating oil of about SUS viscosity at 100 F. Heat evolution during the reaction was negligible. The resulting reaction product was filtered and showed a negligible quantity of lead. The filter medium showed a large amount of solid black particles.

Reaction product C was prepared using the same amounts of reactants as described in Example 1, except that the phosphosulfurized polyisobutylene was replaced by an equal amount of the same solvent neutral mineral lubricating oil. Heat evolution during the reaction was about equal to a normal reaction, such as Example 1, Part II. The reaction product, after filtering, was amber colored and contained only trace quantities of lead. The filter medium showed a large amount of solid black partioles.

It may be safely concluded, therefore, that all three components are necessary to form the reaction products of the invention. The heat evolutions and filterabilities of the two reactions indicate that the lead oxide will not react if the ester is eliminated, and that while a reaction will take place it the phosphosulfurized hydrocarbon is eliminated, the resulting product will be insoluble and therefore unsuitable for use as an oil additive.

Part IIReac'ti0n product D was prepared by the reaction of tallow chloroacetate with sodium sulfide (Na S) and elemental sulfur in a waterisopropanol mixture. Reaction product D was therefore prepared following the general procedure of Example 1, except that the tal-low mercapto acetate ester was replaced by the disulfide described above.

Analysis of the final reaction product showed a lead '8 had the reaction time at the lower temperature (Reaction 6) been increased. The workable temperature range is seen to be generally 260 to 350 F.

The workable range of reaction times is indicated by utilization of only 6%, as compared to the 82% obtained Reactants 2, 3, and 8, which indicate that the reaction with the mercapto ester. times may be satisfactorily varied from 25 to 180 min This result indicates that the disulfide is not sufficiently utes. However, these reaction times are also dependent reactive to be suitable in preparing the products of the upon such variables as temperature, rate of lead oxide invention, addition, and reactor sizing, etc.

Pa III 10 Reaction 3 further shows that the oil diluent for the phosphosulfurized polyisobutylene is not necessary for a A reaction was performed following the general prosuccessful reaction. Although the reaction mass was Cedure of Example 1, xcept that the tallow mercapto more difiicult to handle, a comparable result was obtained acetate ester was replaced with an equal molar amount of using a 100% active ingredient material without the inmercapto acetic acid. Analysis of the reaction product clusion of the oil diluent. showed extremely low lead utilization. Inspection of the filter medium showed large deposits of black particles EXAMPLE 3LABORATORY PERFORMANCE OF indicating that the product was not solubilized. THE REACTION PRODUCTS OF THE INVENTION Experimental runs were repeated with increasing t amounts of the phosphosulfurized polyisobutylene solu- A base 9 Was Prepared havlng follOWlng g tion until it was finally determined that generally at least ems y Welghti a 0.221 ratio by weight of mercapto acid to the polyisobutylene solution was needed to solubih-lze the product 46.9 parts low cold test coastal distillate of 76 SUS/ 100 This compares to a 1.421 ratio which was used with the and 63 ester, as indicated in Example 1 46.9 parts Midcontrnent neutral-150 SUS/ 100 F. and

, Analysis of the reaction product using this 0.2:1 ratio 100 showed a lead utilization of only 39%. 50 Parts e A This result indicates that use of a mercapto ester rather Part Y P 719 than a mercaptoacid is preferred. Part Addmve B Part IV The inspections on this base stock blend are:

Gravity, API 30.8 A number of reactions were performed with varying SUS l 181.3 reactant amounts, reaction temperatures, and reaction SUS 118/ 48.6 times in order to determine the optimum conditions. The 35 sequence of steps was the same as described in Example 1. Cloud, 6 The results of these experimental determinations are Flash COC, F. 360 shown in the following table. ir C C, 385

TABLE I Reaction charge Procedure Reaction product Reaction Reaction Analysis Percent Percent Ratio: tempera- Reaction Percent Oil P190 1 Pb Ester to ture, time, lead solubility V PPB 2 F. minutes Percent Percent Percent utilization Pb s P 11.8 10.8 2.821 320 40 5.3 48 Insoluble.

8.8 8.1 2.011 325 180 6.6 Soluble. 10. 0 9. 2 4 1. 4:1 325-350 25 6. 5 71 Do. 8. 0 7. 3 1. 4:1 325-350 75 6. 2 Do. 8. 8 8.1 1. 411 320 40 6. 9 85 Do. 8.8 8.1 1. 4;1 260 40 4.1 51 Do. 15. 8 14. 3 1. 4:1 350 40 11.6 82 D0. 7. 3 6. 8 111 325-350 25 5. 8 85 D0. 8.0 7. 3 1:1 325-350 75 6.3 86 Do.

:1 Percent PbO based on total weight of reactants.

' 2 Phosphosulfurized polyisobutylene solution, 68 wt. percent, active ingredient in mineral oil except for reaction 3.

3 Reaction time after PbO addition.

4 Reaction 3 used a active ingredient phosphosuliurized polyisobutylene without the mineral oil diluent. The ratio is expressed as if oil were present for comparison purposes.

The following conclusions may be drawn from Table I. 60 Additive A is a 33 wt. percent solution of polyisobutyl- Reaction 1, when compared to Reactions 2, 3, and 7, for example, indicate that use of a 2.821 ratio of ester to phosphosulfurized polyisobutylene will produce an oilinsoluble product and a low lead utilization, whereas ratios of 1.4:1 and 1:1 will produce an oil-soluble prodnot and a high lead utilization. The limiting ratio appears to lie somewhere between 2:1 and 2.811, with the optimum performance being obtained at a 1.4: 1 or lower ratio. 5

The effect of the reaction temperature on the lead utilization may be shown by a comparison of'Reaction 5 with Reaction 6. A higher lead utilization was obtained at about 320 F. than at 260 F. However, the reaction times were the same in both cases and it is likely ene of about 10,000 molecular weight in 67 wt. percent of aosolvent neutral mineral oil of SUS viscosity at The Acryloid 710 was a polymethacrylate viscosity index improver.

Additive B consisted of 37 /2 volume percent of a copolymer of Lorol B fumarate and vinyl acetate, 12.5 volume percent of the condensationproduct of chlorinated wax and naphthalene and 50 volume percent of a neutral mineral oil of 45 SUS at 100 F. The copolymer is primarily a viscosi y index improved while the condensation product is a pour depressant.

To '97 parts by weight of the above base oil were added 3 parts by weight of various of the reaction prodthat a higher lead utilization would have been obtained 75 ucts of Example 6.

The resulting final compositions were tested for loadcarrying ability in a standard SAE laboratory test using a 3.4 rubbing ratio at 1000 r.p.m. This test involves the use of two Timken test cups T4865l, mounted one above The Buna rubber tests indicate that the reaction products of the invention do not seriously deteriorate this rubber and are considerably better in this respect than the conventional gear oil.

the other and rotating in opposite directions. An in- 5 The results of the above tests indicate, therefore, that creasing load is applied to press the lower cup against th r ti d t f th i ti h i the upper 0116 and iihe iest lubricant is pp at t rated into a suitable base oil, will impart extreme pres- P f f The load, eXPIeSSed P at sure properties to oil without affecting its other desirable which Scoring 0f the PP? R l Obsefvfid 15 f Tftlalive properties. These characteristics particularly favor the measure of the 9 Y ability of the i- 10 use of these reaction products as extreme pressure addi- The compositions were also tested for compatibrtily fi i rtransaxle b i with Buna rubber. It is important that the Buna rubber seals used in automatic transmissions will not deteriorate. XAMPLE 4-SIMULATED ROAD PERFORM- While the seals themselves are relatively inexpensive, it ANCE OF THE REACTION PRODUCTS OF THE is necessary to substantially dismantle the entire unit in INVENTION order to replace them. Rubber screening tests were car- Part I ried out as follows: Sections of Buna rubber compound (Acadia Rubber Similar to the rubber naked for Two test 011 compos tions were formulated for testing transmission seals were cut to lengths of /2" x 2". These m a Chew 01a POWFFghde Acceleratwn Test Strips had a Sham A hardness of 77 Th5 resulting The first composrtionconsisted of 4.75 parts by Weight strips were immersed in the oil composition in a 30 cc. of theProduct of 4 of Table and 9525 Parts beaker, covered, and stored in an oven at 300 F. for by Welght of the base R of Exzfmple 100 hours. The strip was removed from the hot test T Second composmon cfmslsted of Parts by oil, placed in a beaker of original cool test oil for /2 wefght of a Product 9 Reaction 1 and Parts by hour, Washed in acetons, wiped and immediately weight of the base 011 of Example 3. Reaction 10 was jected to a Shore Durometer A hardness determination, T1111 ldlng to the procedure of Example 1, except that The higher the number, the harder the rubber. The an equal molar amount of 13 OX0 alcohol ester Was sides of the beaker mentioned above were also examined used Instead of the tauow mercapto acid e The 13 for deposits to check the stability of the composition at OX0 alcohol used to Prepare said ester is an isomeric hi h ternperatures mixture of C primary aliphatic alcohols prepared from A Multiple Oxidation Test was also run as follows: t(ifaPlfopylfinti by OX0 p The PbO charge A sample of the oil composition contained in a test tube was 33% of the total Weight of reactants and the Weight was i i d at 300 .F i a h i b th. I was ratio of ester to the phosphosulfurized polyisobutylene stirred with a steel wire stirrer, while in the presence of Solution Was a copper ire. The Sample was gmovgd ffQm the heat. Thfl lIWO test COITIPOSltlOIlS were used for lubricati b th once h d d h k A 1 Sample of ing the transmission and ditferential units of a Chevrolet the oil composition was then filtered through a #1 Whattest car which W218 tested a f s:

man filter paper and the paper was examined for sludge Chevrolet Powerglide Acceleration T est-This test deposits. Table 11 shows the resins obtained by this test; was carried out y operating a 3 c bic nch disp acei.e the number of days for the appearance of sludge in 10 ment engine connected to a 2-speed Chevrolet Powerglide [the il (deposits o paper), Transmission which was connected to a differential unit.

The reaction products tested were the products of Reac- This mechanism Was automatically operated on a dyntions 5, 6, 7, and 8 of Table I. The base oil per se, a amometer stand by means of a tape controlled electronic conventional gear oil, and a conventional transmission system. From an engine speed equivalent to about 10 oil were also tested. The results are shown in Table II. miles per hour, the engine was operated under maximum TABLE II SEA test Bum. rubber, 4 Test composition reaction scale, lbs. days/300 F. Mult. oxid. test product used in base oil (3.4 ratio at 300 I days to 1,000 rpm.) sludge in oil Shore A Deposits None 7 0 1 5 245 82 0 4 6 290 s1 0 5 7 285 81 0 3-4 s 245 81 0 6+ Conventional gear oil 450+ 1 90 Yes 1 Conventional transmission oiL. 70-100 78 0 2-6 Brittle.

The above table indicates that the reaction products throttle until it shifted from. L0 to Drive gear and had of the invention considerably improve the load-carrying reached its maximum speed of about 85 miles per hour ability and the oxidation resistance of the base oil. While in drive gear, at which point the engine was decelerated the load-carrying ability does not equal that of a conven- 70 to a speed of about 10* miles per hour. A brake signal tional gear oil, it does represent a considerable improve- Was interposed every second cycle. This test was rement over a conventional transmission oil. Furthermore, peated for the total mileage at the rate of one full cycle the oxidation resistance of the reaction products is highevery one and a half minutes. At the end of each test, er than that of the conventional gear oil and equal to transmission and difierential units were disassembled and that of the conventional transmission oil.

examined for wear or damage.

Various tests were performed with different total mileages. The results are summarized in Table III as follows:

TAB LE III and pourdepressant, are included merely to impart the required low pour point and viscosity-temperature rela- Additive Total mileage Transmission Differential Reaction Product 4 (Tal- 800 low). 2, 000 Clean, trace score on clutch plates.

Gears as new.

Gears almost as new.

Trace score on drive As indicated by the preceding data, the reaction products of the invention are'excellent additives for transmission and differential lubricants.

Part 11 Two test oil compositions were formulated for testing in a Corvair Shock Test.

The first composition consisted of 4.15 parts by weight of the product of Reaction 10 of Example 4 (prepared from a C OX alcohol ester) and 95.85 parts by weight of the base oil of Example 3.

The second test composition consisted of 3 parts by weight of the product of Reaction of Table I (prepared from a tallow alcohol ester) and 97 parts by weight of the base oil.

Each test oil composition and the base oil per se were separately tested for lubricating efliciency in the rear axle unit of a 1960 Corvair with a standard transmission.

The auto was run as follows:

Step 1: 50 miles 85 m.p.h. Step 2: Decelerate to 40 m.p.h. Step 3:

V (a) Accelerate to 65 m.p.h. in third gear (b) Turn off ignition (c) Disengage clutch (d) Coast to 60 m.p.h.

(e) Drop in clutch rapidly (f) Overrun to 30 m.p.h.

(g) Turn on ignition Repeat Steps (a) through (g), times. Step 4: Shift to second gear and decelerate to m.p.h. Step 5:

(a) Accelerateto 45 m.p.h. in second gear (b) Turn off ignition (c) Disengage clutch (d) Coast to 40 m.p.h.

(e) Drop in clutch rapidly (f) Overrun to m.p.h.

(g) Turn on ignition Repeat Steps (a) through (g) 10 times.

After each of the above tests, the gears were examined. Both test formulations were rated Pass, with the gears showing only trace scoring. The base oil test showed excessive scoring, damage and discoloring of the gears and an extremely high frictional temperature (550 F.) during the test.

The results of these tests therefore indicate the suitability of the reaction products of the invention as additives for rear axle lubricants.

While the preceding examples have illustrated the invention by using the reaction products of the invention in a specific base oil composition, said reaction products are equally applicable to other base compositions where an increase in load-carrying ability is desired. For example, the reaction products of the invention can be added ,to any suitable base oil, e.g., a Midcontinent neutral oil having a viscosity of 150 SUS at 100 F. and a viscosity index of 100, to thereby increase the load-carrying ability of said oil. The other additives, e.g., the V1. improvers tionship necessary for commercial lubricants, particularly transaxle lubricants. The additives may also be added to distillates, residuals, waxes, greases, etc., to impart mild extreme pressure properties without corrosive or prooxidant effects.

The preceding examples have generally illustrated the preparation and use of the compositions of the invention wherein the phosphosulfurized hydrocarbon material represented a 68 wt. percent active ingredient in 32 wt. percent mineral oil. However, as particularly pointed out by Reaction 3 of Table I, the mineral oil merely serves as a diluent and can be eliminated without affecting the suitability of the reaction products of the invention. Therefore, for purposes of clarity, the following claims are directed to a 100% active ingredient phosphosulfurized hydrocarbon material and the various weight percentages and weight ratios are set forth on this basis. Accordingly, the equivalent range of the mixture of mercapto acid ester and phosphosulfurized hydrocarbon material is 70 to 96 weight percent, preferably to 94 weight percent; the equivalent range of lead oxide is 4 to 30 weight percent, preferably 6 to 20 weight percent; and the equivalent weight ratio of the mercapto acid ester to the phosphosulfurized hydrocarbon .material may range from .321 to 3.7:1, preferably 1.4:1 to 22:1.

In sum, the present invention relates to lubricants which are useful for extreme pressure applications, and which have any suitable base composition, to which is added the reaction products of the invention.

What is claimed is:

1. An oil-soluble reaction product containing 2.5 to 20 wt. percent lead prepared by reacting 4 to 30 weight percent of an oxide of lead with 96 to 70 weight percent of a mixture of (a) a mercapto acid ester of the formula HS (CH COOR wherein n is 1 to 4, and R represents a C to C alkyl group and (b) an ashless oil-soluble phosphosulfurized hydrocarbon material, at a temperature between 200 and 450 F., and cooling to thereby form said reaction product, wherein the weight ratio of said ester to said hydrocarbon material is 03:1 to 3.7:1.

2. An oil-soluble reaction product according to claiml,

wherein said oxide of lead is PbO.

3. An oil-soluble reaction product according to claim 1, wherein R of said mercapto acid ester represents a C to C alkyl radical.

4. An oil-soluble reaction product according to claim 1, wherein said mercapto acid ester is the ester of mercapto acetic acid and tallow alcohol.

5. An oil-soluble reaction product according to claim 1, wherein said mercapto acid ester is the ester of mercapto acetic acid and C alcohol. i

6. An oil-soluble reaction product according to claim 1, wherein said hydrocarbon material is a polymer of a C to C mono-olefin, said polymer having a molecular weight between 400 and 10,000.

7. An oil-soluble reaction product'according to claim 6, wherein said polyolefin material is a polyisobutylene having a molecular weight between 500 and 1200.

8. A lubricating oil composition suitable for lubrication of automotive transaxle systems comprising a major amount of mineral lubricating oil and about 0.5 to 10.0 weight percent of an oil-soluble reaction product containing 2.5 to 20 wt. percent lead prepared by reacting 4 to 30 weight percent of an oxide of lead with 96 to 70 weight percent of a mixture of (a) a mercapto acid ester of the formula wherein n is 1 to 4, and R represents a C to C alkyl group and (b) an ashless oil-soluble phosphosulfurized hydrocarbon material, at a temperature between 200 and 450 F and cooling to thereby form said reaction product, wherein the weight ratio of said ester to said hydrocarbon material is 0.3:l to 3.7: 1.

9. A lubricating oil composition according to claim 8, wherein said oxide of lead is PbO.

10. A lubricating oil composition according to claim 8, wherein R of said mercapto acid ester represents a C to C alkyl radical.

11. A lubricating oil composition according to claim 8, wherein said mercapto acid ester is the ester of mercapto acetic acid and ta-llow alcohol.

12. A lubricating oil composition according to claim 8, wherein said mercapto acid ester is the ester of mercapto acetic acid and C alcohol.

13. A lubricating oil composition according to claim 8, wherein said hydrocarbon material is a polymer of C to C mono-olefin having a molecular weight between 400 and 10,000.

14. A lubricating oil composition according to claim 13, wherein said polyolefin material is a polyisobutylene having a molecular weight between 500 and 1,200.

15. A lubricating oil composition according to claim 8, wherein said reaction product contains, based on the total weight of said reaction product, 2.0 to 15 weight percent sulfur, and 0.2 to 2.0 Weight percent phosphorous.

16. A lubricating oil composition according to claim 8, which contains 2 to 7 Weight percent of said reaction product and wherein said reaction product contains, 4 to 12 weight percent lead, 3 to 10 weight percent sulfur, and 0.5 to 1.5 weight percent phosphorus.

17. A method of preparing a lubricating oil extreme pressure additive containing 2.5 to wt. percent lead which comprises reacting 4 to weight percent of an oxide of lead with 96 to 70 weight percent of a mixture of (a) a mercapto acid ester of the formula HS (CH COOR 14 wherein n is l to 4, and R represents a C to C alkyl group and (b) an ashless oil-soluble phosphosulfurized hydrocarbon material, at a temperature between 200 and 450 F., and cooling to thereby form said additive, wherein the weight ratio of said ester to said hydrocarbon material is 0.3 :1 to 37:1.

18. A method of preparing a lubricating oil extreme pressure additive containing 4 to 12 wt. percent lead which comprises reacting 6 to 20 weight percent of an oxide of lead with 94 to weight percent of a mixture of (a) a mercapto acid ester of the iormula HS (CH COOR wherein n is 1 to 4, and R represents a C to C alkyl group and (b) an ashless oil-soluble phosphosulfurized hydrocarbon material, at a temperature between 280 and 370 F., and cooling to thereby form said additive, wherein the Weight ratio of said ester to said hydrocarbon material is 1.421 to 2.2: l.

w. A method of preparing a lubricating oil additive which comprises heating 80 to 94 weight percent of a mixture of (a) the ester of mercapto acetic acid and tallow alcohol and (b) an ashless oil-soluble phosphosulfurized po-lyisobutylene having a molecular weight between 500 and 1,200, to a temperature between 280 and 370 F, wherein the weight ratio of said ester to said polyisobutylene is 0.3:1 to 3.721; incrementally adding over a period of about 10 to 180 minutes 20 to 6 weight percent of P so as to maintain the temperature within said range to thereby generate a reaction and to produce a reaction mixture; aging said reaction mixture within said temperature range for about 10 to 240 minutes so as to complete said reaction; and cooling said reaction mixture to thereby form said additive; wherein said additive contains 4 to 12 weight percent Ph, 3 to 10 weight percent S, and 0.5 to 1.5 weight percent P.

29. A method of lubricating transaxle systems which comprises applying to said systems a lubricating oil composition of claim 8.

References Qited by the Examiner UNITED STATES PATENTS 12/41 Burke et al. 252-4860 X 11/60 Sabol et a1. 252-32.7

Claims (1)

1. 8. A LUBRICATING OIL COMPOSITION SUITABLE FOR LUBRICATION OF AUTOMOTIVE TRANSAXLE SYSTEMS COMPRISING A MAJOR AMOUNT OF MINERAL LUBRICATING OIL AND ABOUT 0.5 TO 10.0 WEIGHT PERCENT OF AN OIL-SOLUBLE REACTION PRODUCT CONTAINING 2.5 TO 20 WT. PERCENT LEAD PREPARED BY REACTING 4 TO 30 WEIGHTS PERCENT OF AN OXIDE OF LEAD WITY 96 TO 70 WEIGHT PERCENT OF A MIXTURE OF (A) A MERCAPTO ACID ESTER OF THE FORMULA