US 3903001 A
An improved method of lubrication of a controlledslip differential comprises using a lubricant comprising a static friction reducing amount of an aliphatic phosphate ester and a hydrocarbon base stock having a kinematic viscosity at 210 DEG F. in the range of 1.5-200.0 c.s. and containing a major amount of a hydrogenated polymer of C3-C12 olefin, such as a "true" isobutylene oligomer or of a blend of at least one C13-C29 naphthene and from 0.1-20 parts by weight, based on said naphthene of at least one member from at least one of the following groups (a), (b), (c) and (d):
Description (OCR text may contain errors)
United States Patent [1 Gates et al.
[4 1 Sept. 2, 1975 LUBRICANT FOR A CONTROLLED-SLIP DIFFERENTIAL  Assignee: Sun Research and Development Co.,
221 Filed: Jan. 17, 1972  Appl. No.: 218,394
 US. Cl 252/32.7 E; 252/46.6; 252/49.8; 252/59; 252/75; 252/78  Int. Cl..... C10m 3/42; ClOm 3/40; ClOm 3/32  Field of Search 252/32.7 E, 49.8, 59, 78, 252/46.6, 75; 260/950 OTHER PUBLICATIONS Rounds, .lour. Chemical & Engineering Data, Vol. 5, No 4, (1960), pp. 499-507.
Primary ExaminerDelbert E. Gantz Assistant Examiner-I. Vaughn Attorney, Agent, or Firm-George L. Church; .1. Edward Hess; Barry A. Bisson [5 7 ABSTRACT An improved method of lubrication of a controlledslip differential comprises using a lubricant comprising a static friction reducing amount of an aliphatic phosphate ester and a hydrocarbon base stock having a kinematic viscosity at 210F. in the range of 1.5-200.0 c.s. and containing a major amount of a hydrogenated polymer of C C olefin, such as a true isobutylene oligomer or of a blend of at least one C -C naphthene and from 01-20 parts by weight, based on said naphthene of at least one member from at least one of the following groups (a), (b), (c) and (d):
a. a synthetic liquid C --C olefin homopolymer copolymer, or terpolymer;
b. a member from group (a) above which is at least partially hydrogenated;
c. a severely hydrorefined containing less than 1% hydrocarbons; and
d. a severely hydrorefined paraffinic lube containing less than 1% of gel aromatic hydrocarbons;
and wherein the amount of said blend which is present in said base stock is sufficient to provide a greater coefficient of traction, measured at 600 ft./min., 200F., 400,000 p.s.i., than would be provided by substitution of the same amount of ASTM Oil No. 3 for said blend in said base stock. The preferred lubricant also contains an extreme pressure additive (e.g. tricresyl phosphate).
naphthenic lube of gel aromatic 20 Claims, 4 Drawing Figures PATENTEUSEP'ZIQYS 3.903.001
sum 1 er 4 FIGURE l mIPA m n n n NH] 11V CONTROLLED-SLIP DIFFERENTIAL PATENTED SEP 2 suanaum FIGURE2 "ROXANA LVFA" FRICTION vs. SLIDING SPEED SLIDING SPEED (FT. lMlN.)
LUBRICANT FOR A CONTROLLED-SLIP DIFFERENTIAL CROSS REFERENCE TO RELATED APPLICATIONS The present application is related to the following listed United States applications,
Serial No. Filing Date Title/Inventor(s) 621,443 3-8-67 Synthetic Lubricants from Low (Now Abandoned) Molecular Weight Olefms RICHARD S. STEARNS-IRL N. DULING DAVID S. GATES 679,801 1 1-1-67 Traction Drive Transmission Con- 5 (Now U.S. 3,597,358, taining Adamantane Compounds as issued 8-3-71) Lubricant IRL N. DULING- FREDERICK I. GLAZIER-DAVID S. GATES and ROBERT E. MOORE 679,833 1 1-1-67 Traction Drive Transmission Con- (Now US. 3,595,796. taining Naphthenes, Branched issued 7-27-71 Paraffins, or Blends of Naphthenes and Branched Parafiins as Lubricant IRL N. DULING and DAVID S. GATES 679,834 1 1-1-67 Blending Branched Paraffin Fluids (Now US. 3,595.797, for Use in Traction Drive Transissucd 7-27-71) mission IRL N. DULING-DAVID S.
GATES and MARCUS w. HASELTINE 679,851 1 1-1-67 Traction Drive Transmission Con- (Now U.S. 3,598,740, taining Paraffnic Oil as Lubriissued 8-10-71 cant IRL N. DULING-DAVID S.
GATES-THOMAS D. NEWINGHAM 784,487 12-17-68 Conversion of Adamantanc Hydro- (now U.S. 3,646,224, carbons to Monools ROBERT E.
issued 2-29-72) MOORE 794.844 1-24-69 Friction Drivc Fluid IRL N.
(Now U.S. 3,608,385, DULING and FREDERICK P.
issued 9-28-71 GLAZIER 812,516 2-19-69 Catalytic Hydrofinishing of Pet- (Now U.S. 3,619,414, roleum Distillates in the Lubissued 1 1-9-71 ricating Oil Boiling Range IVOR W. MILLS-MERRITT C. KIRK, .IR. and ALBERT T. OLENZAK 823,138 5-8-69 Reaction for Linking Nuclei of (Now U.S. 3,560,578, Adamantane Hydrocarbons issued 2-2-71) ABRAHAM SCHNEIDER 850,717 8-18-69 Hydrorefincd Lube Oil and Pro- (now abandoned) cess of Manufacture IVOR W.
MILLS and GLENN Rv DIMELER 876,993 1 I-14-69 Friction or Tractive Drive Fluid (now U.S. 3,645,902, Comprising Adamantanes IRL N.
issued 2-29-72) DULING-FREDERICK P. GLAZIER- DAVID S. GATES and ROBERT E. MOORE 5 877,462 1 1-17-69 Combination of Traction Drive (now abandoned) and Traction Fluid Comprising Saturated Cyclic Compounds IRL N. DULING and FREDERICK P. GLAZIER 3,256 8-19-69 Friction or Tractive Drive Fluid (now U.S. 3,648,531. IRL N. DULING-FREDERICK Pv issued 3-14-72) (now abandoned) (now US. 3,778,487
issued 12-11-73) (now U.S. 3,737,477 issued 6-5-73) (now US. 3,676,521, issued 7-1 l-72) GLAZIER-DAVID S. GATES and ROBERT E. MOORE Process for Producing Polyisobutylene Oil ALFRED E.
HIRSCHLER and GARY L. DRISCOLL DULING and FREDERICK P.
GLAZIER Polyisohutylene Oil Having a High Viscosity Index GARY L. DRISCOLL IRL N. DULING and DAVID S.,
GATES Process of Preparing Synthetic Lubricants from Low Molecular Olefins RICHARD S. STEARNS- IRL N. DULING and DAVID S.
GATES Synthetic Lubricants from Low Molecular Weight Olefins RICHARD S. STEARNS-IRL N DULING -Continued Serial No. Filing Date Title/Inventor( s) (now U.S. 3,646,233 issued 2-29-72) and DAVID S. GATES 80,779 10-14-70 Reaction of Normal Paraffins with Adamantane Compounds ROBERT E. MOORE 116,985 2-19-71 Lubricant for Controlled-Slip (now U.S. 3,825,495 issued 7-23-74) Differential THOMAS D. NEWINGHAM-ALEXANDER D. RECCHUITE- JOHN Q. GRIFFITH, III-MARCUS W. HASELTINE, .IR.
Combination of Tractive Drive and Traction Fluid Comprising Saturated Cyclic Compounds IRL N. DULING and FREDERICK P. GLAZIER Chemical Reaction Products of Polyisobutylene GARY L. DRISCOLL and MARCUS W. HASELTINE, JR.
137,556 4-26-71 Chemical Reaction Product of Sulfur, Lard Oil and Polyisobutylene ALEXANDER D, RECC- HUITE-GRAY L. DRISCOLL Traction Transmission Containing Lubricant Comprising Gem- Structured Polar Compound MARCUS W. HASELTINE, JR. and GARY L. DRISCOLL Lubricant Comprising Gem-Structured Organo Compound GARY L. DRISCOLL and MARCUS W. HASELTINEJR.
(now U.S. 3,715,313 issued 2-6-73) (now U.S. 3,793,203 issued 2-19-74) (now U.S. 3,843,537 issued 10-22-74) (abandoned lO-2-72) Combination of Tractive Drive and Traction Fluid Comprising Saturated Cyclic or Acyelic Compounds IRL N. DULING and FREDERICK P. GLAZIER The disclosure of all of the above cited applications is hereby incorporated herein (by this reference). In particular, these applications disclose blended lubricants which are useful in the present invention, additives which can be useful in such lubricants and processes for making individual components of such blends.
BACKGROUND OF THE INVENTION As has been reported by R. L. Kostelak in Lubricalion Vol. 56, No. 4, 1970 (pg. 49 et seq.), the principle of operation of the conventional differential in todays American automobile remains the same as the Pecqueur differential, invented in 1827. Although this conventional differential generally performs very satisfactorily, it has one serious shortcoming; namely,
stalling," which occurs when either rear wheel loses traction. Due to the kinematics of the conventional differential design, the driving torque is divided equally between the two rear wheels and is limited by the wheel with the least traction. Hence, when one wheel loses traction, the vehicle does not move.
To prevent this shortcoming, engineers have developed many ingenious ideas and mechanisms. Each manufacturer has his own descriptive name for his particular mechanism; for example, Chevrolet Positraction, Chrysler Sure-Grip, and Ford Traction-Lok. Generally, however, a differential incorporating one of these mechanisms is called a locking or limited slip or controlled-slip differential.
The limited slip differential (sometimes referred to as LSD") used in the American passenger car is essentially the same as a conventional differential except for the incorporation of some form of friction members (e.g. clutch plates or friction cones). The Kostelak article describes the conventional differential and typical controlled-slip differentials.
Another pertinent article is Lubricants for Limited Slip Differentials by John W. Allen, given at Fuels and Lubricants Meeting, Society of Automotive Engineers, Houston, Texas, Nov. l3, 1966.
Another description is found in US. Pat. No. 3,236,771 to H. .l. Matson, issued Feb. 22, 1966. The Matson patent also describes some problems encountered in lubrication of an LSD.
SUMMARY OF THE INVENTION In a combination of a controlled-slip differential and a lubricant therefor, an improvement comprises using a lubricant comprising a hydrocarbon base stock having a kinematic viscosity at 210F. in the range of l.5200.0 es. and containing a hydrogenated true oligomer of isobutylene or a blend of at least one C, C naphthene and from 01-20 parts by weight, based on said naphthene, of at least one member from at least one of the following groups (a), (b), (c) and a. a synthetic liquid C -C olefin homopolymer (such as a true oligomer of isobutylene), copolymer, or terpolymer;
b. a member from group (a) above which is at least partially hydrogenated (preferably, to an iodine number less than 20, more preferably less than and/or having a 195 UVA less than 2.0);
c. a severely hydrorefmed naphthenic lube contain ing less than 1% of gel aromatic hydrocarbons; and
d. a severely hydrorefined paraffinic lube containing less than 1% of gel aromatic hydrocarbons;
and wherein the amount of said blend which is present in said base stock is sufficient to provide a greater coefficient traction, measured at 600 ft./min., 200F., 400,000 p.s.i., than would be provided by substitution of the same amount of ASTM Oil No. 3 for said blend in said base stock. The preferred lubricant has a viscosity in the range of 5-50 c.s. at 210F., (typically 10-20 c.s.), has a channel point below 32F. (more preferred below 10F, typically 0 to F.) and also contains an extreme pressure (EP) additive (c.g. tricresyl phosphate, zinc dithiophosphate, etc.) and an additive which lowers the static friction of the lubricant (e.g. a surface-active, organic phosphate ester of a linear aliphatic, ethoxylated alcohol).
Preferably, the C -C naphthene has a glass transition temperature in the range of to -30C. and contains as a structural nucleus, a cyclohexyl hydrindan, di(cyclohexyl) alkane, adamantane, spirodecane, spiropentane, perhydrofluorene, perhydrobiphenyl, perhydroterphenyl, decaline, norbornane, perhydroindacene, perhydrohomotetraphthene, perhydroacenaphthene, perhydrophenanthrene, perhydrocrysene, perhydroindane-l-spirocyclohexane, perhydrocarylophyllene, pinane, camphane, perhydrophenylnaphthalene or perhydropyrene.
These blended hydrocarbon base stocks are described in the aforementioned applications of Duling et a1 (e.g. see Ser. No. 33,023, filed Apr. 29, 1970) and in the application of Driscoll et al. The true oligomers of isobutylene are described in the applications of Driscoll et a1).
One important property of an LSD lubricant is the relationship between the static coefficient of friction and the dynamic coefficients of friction at various sliding speeds. Generally, the required coefficients are for steel on steel; however, other reference materials can be used (e.g. steel on paper) depending on the mechanism to be lubricated.
The preferred methods for obtaining the required friction coefficients include two.
One is the LVFA (or Low Velocity Friction Apparatus) method. The LVFA method is described by T. D. Newingham in Publication 774A of the Society of Automotive Engineering (National Fluids and Lubricants Meeting, Tulsa, Oklahoma, Oct. 303 1, 1963) The second method is the R-H method, which is described by M. L. Haviland et a1, Friction Characteristics of Controlled-Slip Differential Lubricants, pp 828-843, S. A. E. Transactions (1967).
Certain of the lubricants of the present invention, as will be further described hereinafter, produce unusual and very desirable friction curves when measured by either of these methods. These desirable curves can be described as low static-high dynamic friction. A key component of these desirable lubricants is an effective amount of a surface-active organic phosphate ester of a linear aliphatic, ethoxylated alcohol, said amount (e.g. 0.1-10 wt%) being effective to reduce the static friction while not greatly reducing the dynamic friction.
BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings, FIG. 1 is an illustration of a controlled-slip differential and will be referred to with reference to a test method for comparing the dynamic torque obtained from a given combination of lubricant and controlled-slip differential. The test can be useful in comparing various lubricants in a given differential.
For example, in a limited slip differential (LSD), the Contact plates can be surfaced with swirl patterns to produce high friction. When the plate has become worn, the friction drops drastically and the LSD fails to perform any better than a conventional differential. With a high traction-LSD fluid, the friction property is inherent in the fluid itself and is not completely dependent on the patterned contact surfaces. Thus, the lubricated contacts can have high friction (or traction) even when badly worn.
With reference to FIG. 1, torque measurements are made by attaching a belt 10 around one of the rear wheels 8 and connecting the belt end to a calibrated spring scale 11. The other rear wheel 1 is then turned by hand to slip the differential. The measurement when slip begins is taken as the break-free torque. A second measurement is determined at approximately 40 rpm (with the wheel 1 being driven by a motor).
The differential in FIG. 1 consists of a ring gear 4, a differential pinion 6 and cross shaft, and a right 7 and a left 2 clutch plate attached to the differential case. The wheels are connected to the differential pinion by the right 5 and the left 3 side gears. Clutch plates are also attached to the left and right axle shafts. The differential assembly and the lubricant are contained in a housing 9.
F lGS. 2, 3 and 3 illustrate, for a number of lubricants, the relationship between the static coefficient of friction and the dynamic coefficient of friction at various sliding speeds. The FIGS. 2 and 4 data was obtained by the LVFA method; whereas, the FIG. 3 data was obtained by the R-H method.
EXAMPLE 1 466 g. of a commercial a-methyl styrene polymer, obtained by conventional acid-catalyzed polymerization, is placed in a 1-liter round bottomed flask, attached to a 1-inch column, and dry-distilled with essentially no reflux or fractionation at a pot temperature of about 290C, and a vapor temperature of about 210C. under a vacuum of about 6 millimeters of mercury. 373 g. of distillate are obtained and about 73 grams of material remain in the bottom of the flask at the end of the distillation. The commercial a-methyl styrene polymer has a softening point of 210F., a Gardner-Holdt viscosity of J-L, a specific gravity of 1.075, a refractive index at 20C. of 1.61 a molecular weight of 685, an iodine number of 0, an acid number of 0, and a saponification number of 0.
EXAMPLE I1 300 g. of the distillation product of Example 1 is placed in a 316 stainless steel bomb along with 7.5 grams of Raney nickel catalyst and the bomb is pressured to 3,000 p.s.i.g. of 100% hydrogen while heat is applied until the temperature in the bomb is 150C. At that point an exothermic reaction occurs and heating is discontinued. The temperature is allowed to rise to about 230C. and the hydrogen pressure is maintained at 3,000 psi. for 6 hours at which time the bomb is slowly cooled to ambient temperature while maintaining the hydrogen pressure at 3,000 p.s.i. in order to avoid dehydrogenation of the hydrogenated product. The resulting perhydrogenated poly (oz-methyl styrene) oil is topped to remove components boiling below 125C. The remaining perhydrogenated naphthene product has a KV210 of l 1.07 c.s. and a KV100F. of 327.8 c.s. Analysis by nuclear magnetic resonance (NMR) shows the oil of this example to contain about 40% of trimers (mostly hydrindan form), and 60% di mers, mainly 1,1,3-trimethyl-3-cyclohexy1 hydrindan.
EXAMPLE III A blend of two commercially available polybutene polymers (i.e., 90 vol.% lndapol L-l00 and 10% Oronite Special 6) is completely hydrogenated to produce a hydrogenated polybutene oil which analyzes 0.5 mole percent olefin by the ultraviolet absorbence method. The hydrogenation is at 200C, 2,000 psi. of 100% hydrogen for 6 hours using Harshaw Nl0l04P catalyst.
The resulting hydrogenated polyolefin oil has a KV210F. of 13.54 es. and a KVlOO of 162.8.
EXAMPLE IV A blended base oil was compounded from 61.0 volumes of the naphthene product of Example 11 and 33.1 volumes of the hydrogenated polyolefin oil of Example 111. Then 5.9 volumes of a commercial limited slip axle additive (Lubrizol Company, Anglamol 99LS) was added to the blend to produce a formulated lubricant.
Table 1 describes typical properties of Anglamol 99LS.
TABLE 1 Specific Gravity at 60F., (15.6C.) 1.055 Pounds per Gallon at 60F., US. 8.79 Pounds per Gallon at 60F., 1MP. 10.55 Viscosity at 210F., (989C) SUS 60 Viscosity at 210F., cSt. 10.2
Weight Percent of:
Typical Sulfur 29.2 Phosphorous 2.0
Similarly, other blended base oils (e.g. comprising synthetic paraffins and naphthenes) and other gear oil additives can be used to formulate such lubricants. Other useful additives are those mentioned by F. G. Rounds, Journal of Chem. and Eng. Data, Vol 5, No. 4, October, 1960, pp. 504-505. Useful blended base oils and additives are disclosed, for example, in previously cited applications Ser. Nos. 33,023, and 52,301.
EXAMPLE V Another useful lubricant for a controlled-slip differential, and which is also useful for lubrication of a traction drive transmission, comprises a blend'of the following (all hydrogenations are to at least 98% saturation):
The use in this lubricant of high and low viscosity fractions of the naphthene and paraffin is an example of dumbelLblending to improve viscosity index.
The Ultraphos 1 1 additive is a surface-active, organic phosphate ester of a linear aliphatic, ethoxylated alcohol, and is further described hereinafter.
The synthetic sulfurized oil is the invention of Alexander D. Recchuite and is the subject of application Ser. No. 135,466 (now abandoned). This oil can be used as a replacement for sulfurized sperm oil and can be made by heating sulfur and a blend of from 3095% lard oil and 5% of one or a mixture of C -C acyclic monoolefin. For example, 10 weight percent of sulfur was added at 250F. to weight percent of a blend 200F., and, finally, blown with air for 1 hour.
Another procedure for making the synthetic sulfurized oil is to heat the lard oil-olefin blend to about 300F., add sulfur (e.g. 5-25%) over a 30 minute period (with agitation), then bring the temperature to 335F., maintain for 2 hours, cool to 200F. and finally blow with air for 16 hours. This latter procedure was used for the synthetic sulfurized oil in the above listed lubricant.
The channel point of a lubricant is determined by drawing a channel with a spatula in a sample of lubricant, at a given temperature, and finding the maximum temperature where the walls of the channel no longer cave-in.
EXAMPLE VI A well-worn limited slip differential in a 1965 Buick Skylark (driven over 65,000 miles) was used to compare lubricants, by the previously described method.
The used, original fill fluid was replaced with a fresh conventional petroleum-based LSD fluid (e.g. solvent refined paraffinic lube plus Anglamol 99LS). Torque measurements were made periodically for the next 500 miles. For the last 100 miles, a 6 p.s.i. difference in air pressure in the rear tires caused the differential to slip constantly. It was believed that this tire pressure difference caused the fresh fluid to work into the contact areas. At the end of 500 miles, the conventional fluid was replaced with the blended traction-LSD fluid of Example lV, which had the same viscosity at 100F. and the same additive system as the petroleum-LSD fluid. After 40 miles of driving with the 6 p.s.i. air pressure differential in the rear tires the torque measurement at the low speed dynamic conditions was nearly double that observed when the petroleum-LSD fluid was used. There was little difference in the break-free torque since the static friction is primarily dependent on the additive system. Table 2 presents the test data obtained from this testing.
TABLE 2 Torque Through Worn Limited Slip Differential Torque (Lbs) Odome- Break-Free rpm Fluid 80 92 Traction-LSD Fluid charged A graphic representation of the results of this testing can be found in Design and Development of Fluids for Traction and Friction Type Transmissions, by M. W. Haseltine, Jr. 1. N. Duling, P. E. I-Iagstrom, R. J. Stenger and J. S. Gates, Society of Automotive Engineers Publication 710937 (Meeting Oct. 26-29, 1971, St. Louis, M0.)
The high dynamic friction also helped reduce chatter. With high dynamic friction, static friction can increase to a higher level before chatter will occur. Thus, low static modifying additives are effective for a longer period of time in a high traction-LSD fluid. This results in longer LSD fluid life before chatter occurs. In the present invention a preferred low static friction modifier is 01-10% of a surface-active organic phosphate ester of a linear, aliphatic ethoxylated alcohol.
EXAMPLE VII Conventional petroleum-LSD lubricant and the blended Traction-LSD" lubricant of Example IV were compared in four limited slip differentials, by the previously described test method. The results of these tests are summarized in Table 3. The performance of each differential was improved when lubricated by the blended traction-LSD lubricant.
TABLE 3 Chev. 1969 Petroleum-LSD Traction-LSD Fluid Original Torque Through Various Limited Slip Differentials Odometer at Fluid Torque, lhs.
Change Break-Free 40 RPM Odometer at Torque Test Chev. 1969 Petroleum-LSD Traction-LSD Pontiac 1970 Petroleum-LSD Traction-LSD Ford Original Original Original Petroleum-LSD Traction-LSD Any of the usual gear lube additives can be used in the lubricant-differential combination of the present invention; however, especially beneficial results are obtained when 0.25-l% (based on the base stock) Ultraphos l l (or less preferred, Ultraphos 12) is used as one of the additives. Ultraphos 11 is marketed by Witco Chemical Company and has the following typical properties:
KV 23.44 c.s. ASTM-Vl 142 KV 2l7.20 c.s. VTF-Vl 132 Melting Point 0C. Glass Transition Temperature 62C. Elemental Analysis Carbon 58.16% Hydrogen 10.47% Oxygen 20.44% Ash 1.58% Phosphorous 5.77% Sulfur 0.4% (Schoniger) Nitrogen 0.l0% Chlorine 10 ppm Alternatively, Antara LB400 (General Aniline and Film) can be used instead of Ultraphos as a low static modifier.
Another useful multipurpose additive package which is useful in such lubricants is 2-15% Anglamol 93, which has been previously described and which is a product of Lubrizol Company and comprises a mixture of zinc phosphorodithioate and chlorinated hydrocarbons, a typical analysis being 3% Zn, 3% P, 16.5% Cl and 16.0% S. A useful extreme pressure additive can consist essentially of tricresyl phosphate, or a zinc dialkyl dithiophosphate, or a mixture thereof.
The present invention involves novel compositions which contain chemical reaction products which can be produced by the action of sulfur or sulfur monochloride on lard oil and the polyolefins or polyolefin oils of the aforementioned application-Ser. No. 52,301. Such cosulfurized compositions are described in copending application Ser. No. 137,556 and are useful as lubricant additives, particularly in lubricants for tractive drives and limited slip differentials, and are generally useful as a replacement for sulfurized sperm oil.
A novel substitute for sulfurized sperm oil can be obtained by sulfurizing a blend of 90 to 30 parts by weight of lard oil and 10 to 70 parts of an olefin containing 12 to 128 carbon atoms. The sulfurization is carried out using elemental sulfur. Sulfur monochloride can be used for both sulfurizing and chlorinating simultaneously. The sulfurization involves cooking at from 330 to 445F. for 20 minutes to 10 hours followed by blowing with a gas (preferably, at from 125 to 340F. for 30 minutes to 20 hours) to remove hydrogen sulfide. With sulfur monochloride, the preferred cooking temperature is in the range of 150-250 (under pressure if desired). The sulfurized oils can contain from to 25 weight percent sulfur as based on the blend of olefin and lard oil (i.e., 5 to 25 parts by weight of sulfur, per 100 parts by weight of olefin-lard oil blend).
For example, one embodiment of the invention involves using the previously described lubricants and from O. ll 0% of a composition consisting essentially of a sulfur-containing chemical reaction product of a mixture of lard oil and a true isobutylene oligomer, that is, a branched olefin hydrocarbon having 4N carbon atoms where N is an integer from 3-32, said olefin hydrocarbon having the formula:
CH cm I CH-,,+C CH, II z I CH CH, n
wherein n is an integer from O to 29 inclusive, and
wherein Z is:
For example, in tetraisobutylene, for one isomer, n is l and Z is (D); for another, n is 2 and Z is (B); for another n is 2 and Z is (A); for another, n is l and Z is (C); for another n is l and Z is (E). For triisobutylene, for one isomer, n is 0 and Z is (D); for another, n is 0 and Z is (C) or (E); for another, n is l and Z is (A); and for another n is l and Z is (B).
The sulfurized product can be produced by blending from 90 to 30 parts of lard oil and from 10 to parts of polyisobutylene, sulfurizing the blend and then blowing the co-sulfurized blend (or co-reaction product) with a gas to remove hydrogen sulfide. The lard oil and olefin generally are blended together at from 65F. to 340F. and the sulfur added while the blend is within this temperature range. In general, the preferred process conditions are those taught in application Ser. No.
- -l35,466 of Recchuite, filed on Apr. 19, 1971.
The preferred commercial lard oil generally is described as winter grade lard oil. The principal difference between the less preferred grades such as No. l lard oil and the preferred grade is in the greater amount of saturated free fatty acids present in the less preferred grades, which can reduce the solubility of the product. The polyisobutylene, suitable for use in the present invention, can contain from 12 to 40 carbon atoms, preferably from 12 to 24 carbon atoms, more preferred 16 or 20. The amount of sulfur generally varies from about 5 to 25 percent by weight as based on the blend of lard oil and polyisobutylene. An inactive sulfurized product is generally desired; therefore, the preferred oils can contain from 6 to l 1 percent as based on said blend. Under the reaction conditions specified herein, this amount of sulfur will become chemically bonded in an inactive form. The resultant product containing 6 to 1 1 percent sulfur, as based on the blend of lard oil and polyisobutylene, is useful as a friction modifier for many applications as well as a cutting oil The amount of sulfur in a given sample of oil is readily determined by X-ray fluorescence. After the amount of total sulfur is determined 100 g. of the oil sample and 20 g of copper powder are placed in a tall 250 ml. beaker setup on a hot plate and equipped with a thermometer and an Unger stirrer operated at 1,750 rpm. The sample is heated to 350F. within a 5 minute period and maintained at 350i 5F. for 1 hour after which it is cooled and filtered through filter paper to remove the copper powder. The sulfur content of the sample is again determined by X-ray fluorescence which is the inactive sulfur. The loss of sulfur (total minus inactive sulfur) is the amount of active sulfur in the original. The amount of active sulfur in the sulfurized oil being used as a friction modifier should be less than about 2.5%. Generally the preferred friction modifiers which contain 6-1 1% total sulfur will also contain from 1 to 2% active sulfur.
After cooking the sulfurized oil is blown with a gas to remove H 5. Any gas may be used which dissolves (or otherwise removes) H 8 and does not significantly react with the sulfurized oil. Suitable gases include air, nitrogen. carbon dioxide and gaseous perhalogenated hydrocarbons. Air is preferred for obvious economic considerations. The blowing is most simply carried out by bubbling the gas through the sulfurized oil. Alternatively the oil may be sprayed into the gas or a falling curtain of the oil in the gas may be used. Generally the blowing is carried out at from 125 to 340F. 1n the-case of the sulfurized oils containing minimal active sulfur the blowing should not be carried out above about 250F. when air is the gas. When a high sulfur content (16-30%) oil is being made it is preferred to use gas blowing temperatures above 190F. as this minimizes the active sulfur lost in processing.
The sulfur may be added either as elemental sulfur or sulfur monochloride (S Cl The elemental sulfur is usually preferred for the low sulfur (6-1 1%) oils but S Cl is often preferred for the cutting oil applications because the chlorine also reacts with the oil and serves to improve the antiweld characteristics of the product.
The sulfurized oils described above are useful as friction modifiers in fluids of the present invention to reduce the static friction more than the dynamic friction. Generally, in such fluids the sulfurized oils are used at from 0.5 to typically 15%, of the overall fluid.
EXAMPLE VIII A three necked, l liter, round-bottomed flask was equipped with a mechanical stirrer, a gas inlet tube (which also serves for intermittent product removal),
stopped and the layers permitted to separate. The top oil layer (170 ml.) was removed and the nitromethane (bottom) layer was returned to the reactor with 5 m1. (3% of product volume) fresh nitromethane added to compensate for solubility losses. After four twentyminute runs, the reaction was stopped. The catalyst in the nitromethane layer was readily killed with water with some production of l-lCl fumes. No difficulty with an exotherm was encountered when killing the catalyst. The combined oil layers (665 ml. including 20 ml. nitromethane) were washed with water, with 5% sodium hydroxide solution, and twice more with water. A solvent such as pentane or hexane can be added to facilitate handling.
Although the oil of this example contains all of the novel polyisobutylene oligimers in the series C, C ..C fractional vacuum distillation can be used to obtain fractions relatively pure in a given oligimer (e.g. C or tetraisobutylene").
1n the reaction of this example, small amounts of water in the catalyst and/or feed material can act as a reaction promoter. If extremely pure materials are used in the process, a small amount of water can be added to initiate or hasten the reaction. A lower alcohol (e.g., methanol) or acid (e.g., acetic acid) can also be used as such a promoter. Generally, the reaction rate can be increased (over anhydrous) by addition of 0. ll.5 moles H O per mole of SnCl Polyolefin products, such as that of this example, can contain residual tin and chlorine (e.g., 2505,000 ppm Cl). These elements, particularly the tin, can be present as a metal-organic compound which imparts EP (extreme pressure lubricant) properties to the product. However, if one desires, the chlorine (e.g., 2,000 ppm) can be removed from the product by heating the product with calcium oxide (lime) followed by filtration. Mild catalytic hydrogen treatment (e.g. 200 psi. of H ,200C., Harshaw Nl-0l04P catalyst) can also be used to reduce the tin and chlorine content to very low levels (e.g., Cl from 2,000 ppm. to 6 ppm) and the resulting polyisobutylene (which can be present with hydrogenated polyisobutylene) can be used to produce the sulfurized product of the present invention.
EXAMPLE IX Polyisobutylene oil, produced as in Example I, was fractionally distilled, at atmospheric pressure, to obtain a product which contained at least weight percent of the C isobutylene oligimer (i.e., tetraisobutylene). The predominantly C fraction boiled in the range of 190245C. and over volume percent boiled at 240C. Analysis by vapor phase chromatography showed that this predominantly C fraction contained less than 10 weight percent C oligimer and less than 10 weight percent of the C and higher oligimers.
EXAMPLE X Twenty-two hundred and sixty ml. of winter strained lard oil were blended with 400 m1. of tetraisobutylene (prepared as in Example 3) in a 5 L kettle equipped with a vibromixer. The mixture was heated to 250F. and the vibromixer operated at maximum speed. Sulfur (239 g) was added and the temperature of the mixture raised to 375F. for 2 hours. The mixture was then cooled to 200F. and air was bubbled through the mixture by means of a glass tube at a moderate rate (below that at which splashing and agitation take place) for one hour. The resulting sulfurized oil was analyzed and found to contain 8.23% sulfur. A ten gram portion of the sulfurized oil was dissolved in 100 g. of a commercially available solvent refined paraffinic lube having a Similarly, lubricants can be compounded comprising a synthetic sulfurized oil and/or a surface active, orgame phosphate ester of a linear aliphatic ethoxylated alcohol and various hydrogenated fractions of true Linear "true" Pulyisobutylenc Oil (Unhydrogenated).
viscosity at 2l0F. of 40.45 SUS, an ASTM viscosity 5 f 1n 0 ls index of 104 and containing 12% aromatics (by ASTM polylsoPutylene (or of g f f polyole 1 D2007). The oil solution remained clear with no sepa- Propemes of some Such true polylsobutylene 011s are ration after being tested at 36 F. overnight and for one Summarized below Comparison, P p of P week at room temperature. troleum lubes are included) in Table 4.
Table 4 COMPARISON OF LPlB* WITH PETROLEUM BASE OILS LPIB l 1.54 4.37 40.3 H1.P1B** 118 1.35 3.53 37.7 20.1 75 155 naphthcnic Oil 52 1.39 4.27 40.0 36.9 90 225 LPlB 100 2.39 8.78 54.6 235 HLPlB 102 2.47 9.21 56.2 139 70 255 naphthcnic Oil 31 2.26 9.53 57 212 70 295 paraffinic lube 98 2.63 10.28 60 163 0 345 LPlB 98 4.46 24.9 119 305 HLPlB 100 4.20 22.3 108 810 75 315 naphthenic oil 0 3.60 22.9 1 10 I730 45 320 hydrogenated naphthenic oil 7 3.60 22.0 106 1330 -50 325 paraffinic lube 104 4.27 22.9 l 10 747 0 385 HLPIB 96 7.17 55.3 256 3,650 50 380 naphthenic oil 2 5.63 54.9 255 12,500 350 paraffimic lube 103 7.36 55.1 256 3,860 0 450 HLPIB 88 11.70 124.1 574 11.810 50 415 naphthenic Oil 0 8.55 128.4 595 94.400 10 390 hydrogenated naphthenic oil 0 8.52 l27.0 588 91,000 5 390 paraffinic bright stock 97 12.38 l26.l 584 16,300 0 495 ""Fully Hydrogenated 1rue" Linear Polyisubutylene (hydrogenation with Ni on Kieselguhr, 1000 psi H 400F).
EXAMPLE Xl Winter strained lard oil (2,525 ml.) was blended with 450 ml of 80+% pure triisobutylene (prepared by a distillation similar to that used in Example 6 but at a lower temperature), in a 5 L kettle equipped with a vibromixer. The mixture was heated to 250F. and the vibromixer operated at maximum speed. These conditions were maintained while 266 g. of sulfur were added over a period of minutes. The temperature was raised to 375F. for 2 hours. The mixture was then cooled to 200F. for 1 hour and air was bubbled through the mixture by means of a glass tube at a moderate rate below that at which splashing takes place. The resulting sulfurized oil was analyzed and found to contain 8.5% sulfur as based on the total composition. A 10 gram portion of the sulfurized oil was dissolved in 100 g. of the solvent refined paraffinic lube described in example X. The oil solution remained clear with no separation after being tested at 36F. overnight and for 1 week at room temperature.
EXAMPLE Xll A useful lubricant. for a controlled-slip differential, and which is also useful for lubrication of a traction drive transmission, comprises a blend of the following (the hydrogenation was to at least 98% saturation):
synthetic sulfurized oil of Example X Made by hydrogenation of a IZ.0 cs. (at 2l0F.) distillate fraction of the product of Example VI".
EXAMPLE XIlI Friction data was obtained for a number of oils. The friction data was used to plot the curves in FIGS. 2, 3 and 4 hereof. The data for FIGS. 2 and 4 were obtained by the LVFA method (using the apparatus marketed by Roxana Machine Works, St. Louis, Missouri). The data for FIG. 3 was obtained by the R-H Friction method, using the General Motors Corporation apparatus.
The following Table identifies the oils of FIGS. 2, 3 and 4:
The blended hydrocarbon portion of Oil 4 Oil 1 plus 1 vol 7: Ultraphos ll Oil 1 plus additives Oil 3 plus 1 vol. 7(- Ultraphos ll Commercial Petroleum base LSD fluid (Texaco TL3450) Hydrogenated true polyisobutylene Oil 6 plus l vol. 7: Ultraphos l l Oil 6 plus 5 vol. 7: Ultraphos ll *The additives are those of the lubricant of Example V. excepting the Ultraphos l l.
"Oil 4 is the lubricant of Example V The curve for Oil 1 in FIG. 2 shows that the blended hydrocarbon base oil used in the lubricant of Example V had a higher static friction than the dynamic friction at sliding speeds in the range of about -120 feet per minute. The blended base oil of Example V was a blend of naphthenes (i.e., hydrogenated a-methyl styrene oligomers) and hydrogenated polyolefins (i.e., polybutenes).
The curve for Oil 2 in FIG. 2 shows that the Ultraphos 1 l (a surface active phosphate ester of a linear aliphatic ethoxylated alcohol) produced a lowered static friction in the blended naphthene-hydrogenated polyolefin hydrocarbon base oil, without greatly altering the average dynamic friction.
Similarly, the curves for Oils 3 and 4 establish that the other additives in the lubricant of Example V did not appreciably lower the static friction but that the phosphate ester additive (Ultraphos 11) produced the low static friction in the lubricant.
The friction curve for Oil 5 of FIG. 2 is that of a conventional commercial prior art lubricant (containing a petroleum base oil) for a limited slip differential. The curve for Oil 5 shows that this prior art lubricant has a much higher static friction than the average dynamic friction in the 20-120 feet per minute range of sliding speed.
The curves of FIG. 3 show that similarly shaped curves, to those of FIG. 2, are obtained by the R-I-l method.
The curves of FIG. 4 show that the phosphate ester additive can be used to lower the static friction, without greatly altering the dynamic friction in hydrogenated polyolefin oils, particularly oils consisting essentially of hydrogenated true polyisobutylene. The hydrogenated polyisobutylene used in Oils 6, 7 and 8 had a viscosity at 210F of 33.5 c.s. (158 SUS) and at 100F. of 742 c.s. (3,440 SUS).
The curves for Oils 7 and 8 of FIG. 4, indicate that a lubricant containing a major portion of a hydrogenated polybutene oil (especially a true polyisobutylene) and the phosphate ester in amount effective to lower the static friction can be useful as a lubricant for a limited slip differential. Other, conventional lube oil additives, e.g., antiwear, dispersant, antirust, antifoam, extreme pressure (EP), and oxidation inhibitors, can also be added to such a lubricant.
Other uses for a lubricant containing the phosphate ester and the hydrogenated polybutylene oil are in wet clutches (such as are marketed by Borg Warner for heavy duty trucks) and in wet brakes (as those used in tractors). For wet clutches and brakes a lower viscosity oil (e.g., 40-500 SUS at 100F.) is generally desirable.
Other useful additives (instead of or with Ultraphos 11) are Antara LB400 and Ortholeum 162. The lubricants containing the Ortholeum 162 have the better heat stability (that is, to maintain low static friction) after 100 hours aging at 300F. Ortholeum 162 consists essentially of dilauryl phosphate and other similar mixed alkyl acid orthophosphates. Other useful phosphate ester additives (to lower static friction) are the phosphate esters of ethoxylated aromatic hydroxy com pounds and their mixed esters with aliphatic hydroxy compounds. The esters can be part esters, (which produce an acidic pH in water, (e.g., pH about 2).
The blended fluids and limited slip differential lubricants referred to herein, especially that of Example IV, can be used to increase traction between two rolling elements. When traction fluid is used to lubricate high speed ball bearings for an example, the main shaft bearings in a turbine engine it reduces ball skidding. Ball skidding is one of the factors limiting shaft speed. Accordingly, such lubricants can be used for high speed and highly loaded bearings. They can also be used for lubrication of overrunning clutches. Such lubricants (in the appropriate viscosity range) can also be useful in conventional nontraction type automotive transmissions to provide improved lock-up and provide for the use of fewer clutch plates. Furthermore, a coating, generally paper, asbestos or resin, is used on clutch plates to increase the coefficient of friction between the plates. This plate coating can sometimes be eliminated when using the fluids of the present invention in such a transmission.
During engagement, there is a sliding motion between the cam or rollers and the races in overrunning clutches. Since wear occurs during the engagement period, a lubricant which reduces engagement time will reduce wear and extend service life. In one test, engagement was reduced from 1 l to two revolutions simply by replacing the conventional petroleum oil grease with a grease component of a naphthene-paraffin blend similar to that of Example IV. The traction fluid and its grease show the greatest advantage in clutches where load is high enough to elastically deform the rollers or cams.
Unless otherwise specified, all percentages herein are by weight.
An especially useful naphthene component of a blended LSD FLUID (as in Example V) is 4,9-cis-lcyclohexyl-l,3,3-trimethylhydrindane, which can be prepared in high yield (about by the hydrogenation of l-phenyl-l,3,3-trimethylindane over a catalyst containing nickel, palladium or rhodium, in which the hydrogen pressure is held in the range of 600 to 1,500 psig, and the temperature is held substantially in the range of 200C to 225C. This process is the invention of Peter Hosler and David S. Gates and is claimed in a later filed application, Ser. No. 218,338, Jan. 17, 1972.
The invention claimed is:
1. A lubricant composition comprising a phosphate ester or mixture of esters selected from a surface active organic phosphate ester of a linear aliphatic ethoxylated alcohol or a mixed alkyl acid orthophosphate and a hydrocarbon base stock having a kinematic viscosity at 210F in the range of l.5-200.0 c.s. and comprising a major amount of (A) hydrogenated liquid polymer of C C olefin or of (B) a blend of at least one C, C naphthene and from 0.1-20 parts by weight, based on said naphthene of at least one member from at least one of the following groups (a), (b), (c) and (d):
a. a liquid C C olefin homopolymer, copolymer, or
b. a member from group (a) above which is at least partially hydrogenated;
c. a severely hydrorefined naphthenic lube containing less than 1% of gel aromatic hydrocarbons; and
d. a severely hydrorefined paraffinic lube containing less than 1% of gel aromatic hydrocarbons; and wherein the amount of said phosphate ester or mixture which is present in said composition is effective to reduce the static friction, measured by the low velocity friction apparatus, of said base stock.
2. The composition of claim 1 and containing in the range of 0. l-l% by weight of said phosphate ester or mixture.
3. The composition of claim 1 wherein said major amount is of a true oligimer of isobutylene.
4. The composition of claim 1 wherein said hydrogenated polymer of component (a) and said hydrogenated polymer of component (b) are at least 80 mole percent saturated.
5. The composition of claim 1 wherein said C C naphthene has a glass transition temperature in the range of 90 to 30C. and contains, as a structural nucleus, a cyclohexyl hydrindan, di( cyclohexyl) alkane, adamantane, spirodecane, spiropentane, perhydrofluorene, perhydrobiphenyl, perhydroterphenyl, decalin, norbornane, perhydroindacene, perhydrohomotetraphthene, perhydroacenaphthene, perhydrophenanthrene, perhydrocrysene, perhydroindanel-spirocyclohexane, perhydrocarylophyllene, pinane, camphane, perhydrophenylnaphthalene or perhydropyrene. l
6. The composition of claim 1 wherein said lubricant also contains'an extreme pressure additive.
7. The composition of claim 6 wherein said extreme pressure additive consists essentially of a compound of phosphorus.
8. The composition of claim 7 wherein said extreme pressure additive consists essentially of tricresyl phosphate or a zinc dialkyl dithiopho'sphate, or mixtures thereof.
9. The composition of claim 1 wherein said naphthene comprises hydrogenated dimers and trimers of alpha-methyl styrene.
10. The composition of claim 1 wherein said C -C olefin in component (b) is at least one C, olefin.
1 l. The composition of claim 10 wherein said C olefin consists essentially of isobutylene.
12. The composition of claim 9 wherein said blend contains from 01-20 parts by weight, based on said naphthene, of a hydrogenated polymer of a C monoolefin.
13. The composition of claim 1 wherein said kinematic viscosity at 210F., is in the range of -50 c.s. and wherein the channel point is at least 10F.
14. The composition of claim 3 also containing from 0. ll0 wt of a synthetic sulfurized oil consisting essentially of a co-sulfurized blend of 9030 parts of lard oil and 10-70 parts of an aliphatic olefin containing 12 to 128 carbon atoms.
15. The composition of claim 3 wherein said true oligimer of isobutylene has 4N carbon atoms where N is an integer from 3-32 and has the formula CH CH3 where n is an wherein z is:
integer from 0 to 29 inclusive, and