US3103493A - Lubricating greases - Google Patents

Description

United States Patent 3,103,493 LUBRICATING GREASES Aleksander Groszek and Geoffrey Hairsine Bell, Sunburyoil-Thames, England, assignors to The British Petroleum Company Limited, London, England, a iointstock corporation of Great Britain N0 Drawing. Filed June 24, 1960, Ser. No. 38,430 Claims priority, application Great Britain July 2, 1959 18 Claims. (Cl. 2S2--41) It is known to prepare lubricating greases by thickening lubricating oils with lithium hydroxy stearate. These greases may, in some cases, be prepared by dissolving pre-formed lithium hydroxy stearate in a lubricating oil at an elevated temperature, rapidly cooling the solution and milling the gel so formed so as to convert it into a grease. In many cases, however, this technique results in the formation of a slurry of coarse granules of soap in the oil. Another method of preparing lithium hydroxy stearate greases is to saponify hydrogenated castor oil in part or all of the oil to be thickened so as to cause the formation of lithium hydroxy stearate in situ. Although somewhat more complicated than the first-mentioncd method, this method has the advantage that the glycerol formed during the preparation forms a complex with the soap which imparts good mechanical stability to the grease. Again, however, the formation of a slurry of coarse granules often occurs when this method is used.

We have now found that the formation of lithium hydroxy steal-ate greases can be facilitated by the use of a particular type of lubricating oil base stock.

According to the invention, there is provided a lubricating grease which has been prepared by thickening to a grease consistency with an alkali metal soap of a hydroxy fatty acid, e.g. an alkali metal soap of a hydrorsy stearic acid such as lithium hydroxy stearatc, a liquid petroleum lubricating oil base stock consisting of or containing an aromatic fraction which has been separated from a petroleum lubricating oil fraction. Preferably the grease contains 5-15% by weight of the soap.

The liquid lubricating oil base stock may consist of a blend of the aromatic fraction and a petroleum lubricating oil fraction. Particularly suitable blends are those containing at least by weight, e.g. l075% by weight, of the aromatic fraction. A suitable petroleum lubricating oil fraction for use in the preparation of the blends is a dewaxed vacuum distillate, particularly a dewaxed vacuum distillate having a viscosity index of at least 40, preferably at least 60, and preferably having a viscosity in the range 45-200 Redwood 1 seconds at 140 F.

The aromatic fraction may be prepared by selective adsorption of a petroleum lubricating oil fraction on silica gel, activated clay, or other adsorbent material. For example, the lubricating oil fraction may be allowed to flow down a column of silica gel which is thereafter eluted with a solvent which preferentially removes from the adsorbent that part of the oil consisting of saturated hydrocarbons. A suitable solvent for this purpose is a low boiling saturated hydrocarbon e.g. petroleum ether, nhexane, n-heptane or iso-octane. The aromatic hydrocarbons which remain in the adsorbent together with most of the sulphur-, oxygenand nitrogen-containing compounds can then be displaced from the adsorbent by a strongly polar, low boiling solvent e.g. acetone, ethyl alcohol, methyl alcohol, isopropyl alcohol, ethyl ether or isopropyl ether. The aromatic fraction recovered after evaporation of the solvent may be used by itself for the preparation of the greases according to the invention, or it may be added to a lubricating oil distillate of the aforementioned type to increase the concentration of aromatics in it.

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Another method that can be used to produce a suitable aromatic fraction is the well-known solvent extraction process. The aromatic extracts obtained by treatment of lubricating oil distillates of the aforementioned type can be used per so as the base stock or they may be added to a lubricating oil distillate to increase its content of aromatic hydrocarbons.

Preferably the lubricating oil base stock is one having an aromatic content of at least 40%, especially at least 50%, by weight as determined by the rapid method of silica gel chromatography described in the Journal of the Institute of Petroleum for July 1958, volume 44, pages 212-2l5.

inspection data on several greases is given below in order to illustrate the invention. The greases were prepared from the following base oils:

Oil A.--A 160/95 grade lubricating oil (i.e. a lubricating oil having a Redwood I viscosity at F. of 160 sees, and a viscosity index of 95). Oil A contained 29% by weight of aromatics.

Oil B.-A /75 grade lubricating oil containing 42% by weight of aromatics.

Oil P.-An aromatic oil obtained from oil B by adsorption of oil B on a column of silica gel, elution of the saturated hydrocarbons with ism-octane and recovery of the aromatic hydrocarbons by elution with isopropyl alcohol followed by evaporation of the latter. The aromatic fraction obtained in this way amounted to 41.3% by weight of the original oil.

Oil D.A material extracted from a waxy petroleum vacuum distillate by i'urfural. The undissolved material obtained after this furfural extraction and dewaxing was a lubricating oil of /95 grade. Oil D was recovered from solution in the furfural and had a sulphur content of 5.1% by weight and an aromatic content of 87% by weight.

Oil S.--A material extracted from a waxy petroleum vacuum distillate by furfural. The undissolvcd material obtained after the furfural extraction and dewaxing was a lubricating oil of 65/100 grade. Oil S was recovered from solution in the furfural and had a sulphur content of 5.78% by weight and aromatic content of about 85% by weight.

Oil T.-A material obtained by hydrofining oil D to reduce its sulphur content. Oil T had a sulphur content of 1.46% by weight and an aromatic content of 80% by weight.

Oil Q.A blend of oil A and oil D containing 75% by weight of oil A and 25% by weight of oil D. Oil Q contained 44% by weight of aromatics.

Oil R.-A blend of oil A and oil D- containing 50% by weight of oil A and 50% by weight of oil D. Oil R contained 58% by weight of aromatics.

Oil U.A blend of oil A and oil T containing 75% by weight of oil A and 25% by weight of oil T. Oil U contained 42% by weight of aromatics.

Oil V.A blend of oil A and oil T containing 50% by weight of oil A and 50% by weight of oil T. Oil U contained 55% by weight of aromatics.

OH l-V.--A blend of oil B and oil S containing 75% by weight of oil B and 25% by weight of oil S. Oil W contained 53% by weight of aromatics.

0:! X. A blend of oil B and oil S containing 50% by weight of oil B and 50% by Weight of oil S. Oil W contained 63% by weight of aromatics.

The aromatic contents of oils A, B, P, Q and R were determined by the rapid method of silica gel chromatography mentioned above.

EXAMPLE 1 Two greases according to the invention and two greases for comparison were prepared using pre-forrned commercial lithium hydroxy stearate and the base oils A, B and P specified above. Each of the four greases was formed by dissolving the soap in the oil at 225 C., pouring the solution into a cooled tray and milling the gel W and X are of better consistency than the correspond ing comparative grease B2.

We claim:

1. A lubricating grease consisting essentially of a petroso formed in a roller mill at 0.005 inch ga The 'soap 5 leurn lubricating oil base stock and a thickening agent, contents and various inspection data on these four greases in which the thickening agent is an alkali metal soap of are given in Table l, in which greases P1 and P2 are asoap-forming hydroxy fatty acid and the petroleum lubrigreases according to the invention and greases A1 and eating oil base stock contains at least 40% by weight B1 are greases prepared for comparison. of an aromatic fraction which has been separated from Table 1 a petroleum lubricating oil fraction.

2. A lubricating grease according to claim 1, in which the soap is an alkali metal hydroxy stearate. m iff ala 3. A lubricating grease according to claim 2, in which the soap is a lithium hydroxy stearate. Base unused on A O B on ml 4. A lubricating grease according to claim 1, in which Content or mmtiiics in the base oil, 42 :00 100 the base stock has been prepared by blending a petroleum sdil p c iii i ezli i'mtion, 13 lubricating oil fraction and an aromatic fraction which Penetration 11 50 or has been separated during the preparation of a petroleum g fgf k I lubricating oil fraction. 100,000 Sll'0 kCS 20 5. A lubricating grease according to claim 4, in which l l ele d fl sl fll Tlylmgpcrccnt wt III: 1 3 at least one of the petroleum lubricating oil fractions was a dewaxed vacuum distillate. 1 Semmquid Slurry. 6. A. lubricating grease according to claim 5, in which It will be Seen that the greases according to the gheledlestviiged vacuum distillate had a viscosity index of vention (greases P1 and P2) are of good consist n y 7 A lubrlating grease according to claim 6, in which even though smaller soap concentrations than usual were the dewaxed vacuum distillate had a viscosity index of employed. Grease P1 which has a smaller soap conat least 60 cenlratlon than B1 very.much l i pene' 8. A lubricating grease according to claim 5, in which tration. Grease P2 is comparable in penetration and p the viscosity of the dewaxed vacuum distillate was in stability With grease B1 although its soap contentiation the range of 200 Redwood I seconds at 140 F. is very much less. G1 ease P2 also has a satisfactory drop oint and gives a satisfactor p rformarm: in the bleed A lubncatmg grease accordmg to Clalm m whlch y w the base stock contains 40-75% by weight of the aromatic fraction.

EXAMPLE I 35 10. A lubricating grease according to claim 1, in which Nine greases were prepared to illustrate the propertles the aromatic fraction was obtained by solvent extraction. of greases prepared from hydrogenated castor oil by 11. A lubricating grease according to claim 1, in which saponification in situ. Greases prepared by this techthe aromatic fraction was obtained by a chromatographic nique contain glycerol produced from the hydrogenated process, castor oil. Each sample was prepared by dissolving 13 4U 12. A lubricating grease according to claim 10, in which by weight of hydrogenated castor oil in a lubricating oil the chromatographic process comprised adsorption of base stock at 100 C. Aqueous lithium hydroxide soluthe petroleum lubricating oil fraction on an adsorbent mation was added to saponify the hydrogenated Castor oil terial, elution of at least some of the aliphatic materials and the temperature raised to 170 C. to rcniiwc the with a solvent and recovery of the aromatic fraction.

Table 2 Grease Number I A2 Q l R A3 1 U l V B2 W X Base on Used 011A on o 011R OilA Oil U 011V Oil B on W OilX Content otarornatics in the base oil, percent Wt .u 2!] 44 58 29 42 42 53 63 Soap Concentration, percent wti 13 13 13 13 13 13 13 13 13 Penetration (IP50):

Unworked 253 215 102 250 225 214 239 220 10s 00 Str0kes 266 222 100 20? 243 232 220 210 205 100,000 Str0kcs 30a 2112 275 203 251 200 Drop Point (IP31), 186 us 150 100 103 188 100 189 is? Bleed Test (DTD 825), percent wt 4.3 0.2 Nil Nil Nil Nil Nil Nil Nil final traces of water. The mixture was agitated during 13. Alubricating grease according to claim 12, in which saponification and dehydration and stirring was continued the lubricating oil was adsorbed on an adsorbent selected until the temperature had fallen to below 100 C. When from the group consisting of silica gel and activated clay. room temperature had been reached the grease was milled 14. A lubricating grease according to claim 12, in which on a roller mill at a 0.005 inch gap and deaeratcd. the solvent used to elute the aliphatic materials was one The compositions and various inspection data of the selected from the group consisting of petroleum ether, nine greases prepared by the method outlined abov are -1 d i t given i Tab 2 in WhiCh greases Q W and X 15. A lubricating grease according to claim 12, in which are greases according to the invention and gr ases A the aromatic fraction was recovered by elution with a A3 and B2 are greases prepared for comparison. solvent selected from the group consisting of acetone, It will be seen that greases Q, R, U and V, particularly ethyl alcohol, methyl alcohol, isopropyl alcohol, ethyl greases R, have lower penetrations than the correspondether and isopropyl ether. ing comparative greases A2 and A3. Similarly greases 16. A lubricating grease according to claim 1, in which 5 6 the aromatic content of the lubricating oil base stock 18. A lubricating grease according to claim 1, which is at least 50% by weight. contains 545% by weight of soap.

17. A lubricating grease according to claim 1, in which the soap was prepared by the saponification in aim of References Cited in the file of this patent hydrogenated caster Oil. 5 UNITED STATES PATENTS 2,625,510 Moore Ian. 13, 1953

Claims (1)

1. A LUBRICATING GREASE CONTAINING ESSENTIALLY OF A PETROLEUM LUBRICATING OIL BASE STOCK AND A THICKENING AGENT, IN WHICH THE THICKENING AGENT IS AN ALKALI METAL SOAP OF A SOAP-FORMING HYDROXY FATTY ACID AND THE PETROLEUM LUBRICATING OIL BASE STOCK CONTAINS AT LEAST 40% BY WEIGHT OF AN AROMATIC FRACTION WHICH HAS BEEN SEPARATED FROM A PETROLEUM LUBRICATING OIL FRACTION.