US3074884A

US3074884A - Solids thickened greases containing petroleum oxidates

Info

Publication number: US3074884A
Application number: US744294A
Authority: US
Inventors: Herbert J Pitman
Original assignee: Texaco Inc
Current assignee: Texaco Inc
Priority date: 1958-06-24
Filing date: 1958-06-24
Publication date: 1963-01-22
Anticipated expiration: 1980-01-22

Description

fi lnited iSitates This invention relates to improved lubricating greases thickened with finely divided solids and more particularly to such greases containing small amounts of certain petroleum oxidates.

In my co-pending application Serial No. 744,293 filed of even date herewith, it is disclosed that extreme pressure properties are imparted to lubricant compositions, including solids thickened greases, by means of Wax oxidates obtained by oxidizing paraihn Waxes separated from distillate oils up to high neutralization numbers above about 200 and under conditions which result in an acidtype product.

In accordance with the present invention it has been found that highly oxidized acid-type petroleum oxidates obtained by oxidizing parafiin fractions, including the oxidates disclosed in my said co-pending application, impart improved dispersion of the particulate thickener in solids thickened greases, with consequent substantially improved grease yields, when they are incorporated in such greases in amounts below those required toimpart improved extreme pressure properties. These oxidates oiier important advantages as dispersants in solids thickened greases over compounds which have been employed for this purpose heretofore, such compounds being gen erally low boiling compounds which cause hazardous or unpleasant fumes during the grease manufacture or storage, as well as other disadvantages. In addition, I have found that these oxidates are employed very advantageously in compositions containing relatively large amounts of fatty oils, including sulfurized fatty oils, wherein other dispersants of various types are ineffective.

The petroleum oxidates employed in accordance with this invention are partial oxidation products obtained by oxidizing heavy paraffinic distillate fractions up to neutralization numbers of at least about 200, such as neutralization numbers in about the range 200-550, and under conditions which produce an acid-type product, having a ratio of neutralization number to saponification number above 0.5. Oxidates of this character are produced by the method which comprises blowing air through the parafiinic charge while the charge is maintained at an elevated temperature in the range from about 200 F. to about 400 F. and under a pressure in the range from slightly above atmospheric up to about 500 pounds per square inch, with an air feed rate from about to about 60 cubic feet of air per hour per pound of wax charge. Suitable feed stocks for the reaction include parafiinic distillate lubricating oils, preferably those having viscosities above about 150 seconds Saybolt Universal at 1.00 F. and most suitably having viscosities in the range from about 155 seconds Saybolt Universal at 100 F. to about 120 seconds-at 210- F., and waxes separated from parathnic distillate oils, including refined waxes, crude scale waxes and slack waxes, preferably containing not more than about percent by weight of oil, and most advantageously containing not more than about 10 percent by weight-of oil. The reaction is. preferably carried out at a temperature in about the range 250 F.-350 F., most suitably in about the range 270 F.-330 F., and under a pressure in about the range -300 pounds per square inch, most suitably in. about the range 50-250 pounds per square inch gauge. An oxidationcatalyst is preferably employed when the reaction is carried out at pressures below about IOU-pounds atom per square inch or When the charge is a lubricating oil or a wax containing more than about 5 percent by weight of oil. Thepreferred catalyst is a metal permanganate, most suitably potassium permanganate, which may be employed in an amount from about 0.01 to about 1.5 percent by weight of the charge.

Under the above conditions, the reaction consists almost entirely of formation of oxygenates of various types with no more than a small amount of polymerization,'the neutralization and saponification numbers of the paraflin charge increasing rapidly up to very high values while the viscosity increases only very slowly up to a viscosity Saybolt Universal at 210 F. of less than 500 seconds, and usually to less than about 200 seconds. The products formed in the first stages of the oxidation reaction are largely simple alcohols, aldehydes, ketones, acids and esters. As the oxidation proceeds further, the formation of more highly oxidized products takes place at increasing rates, and the highly oxidized products obtained by carrying out the oxidation to neutralization numbers of about 200 or higher therefore contain relatively large amounts of oxygenated fatty acidssuch as hydroxy fatty acids, kct'o fatty acids and dicarboxylic acids. These highly oxidized products also contain relatively large amounts of low molecular weight oxygenates, containing about l-3 carbon atoms per molecule, including low molecular Weight acids, aldehydes, ketones, etc., formed by degradation reactions. This low molecular weight fraction may be separated, if desired, by any suitable means such as by distillation or extraction from the higher molecular weight oxidate fraction employed in accordance with this invention. When the presence of low boiling compounds in the lubricant composition is not objectionable, the crude oxidate may be employed or a relatively light fraction of the oxidate obtained by separating heavier portions, may be employed. The low molecular weight oxygenates may be very conveniently removed by Water washing, which results in a lowering of the neutralization number of the oxidate to Within about the range -350. Particularly suitable oxidat'es are those having neutralization numbers in about the range 250-550, and a ratio of neutralization number to saponification number of at least about 0.6, or the, water insoluble portion of such oxidates having neutralization numbers of at least about 200.

The greases of this invention comprise oleaginous liquids thickened to a grease consistency by means of finely divided solids and containing petroleum oxidates of the character described above in amounts effective to impart substantially increased hardness to the greases on the basis of their ASTM Worked Penetration at 77 F. The optimum amount of oxidate will vary somewhat with the particular oxidate employed. In general, the amount of oxidate will vary from about 0.05 to about 2.0 percent by weight of the grease composition, the optimum amount usually being in the range from about 0.1-1.0 percent by weight of the composition. The finely divided solid is employed in a suificient amount to impart a grease consistency to the composition. Ordinarily it will be present in an amount between about 5 and about 35 percent by weight of the composition, although smaller or larger amounts may be employed in some cases, such as, for example, from about 2 to about 45 percent by weight of the composition.

The solid, thickening agents employed in these greases may be any of those in general having the property of forming a gel structure when they are dispersed in lubrieating oils in finely divided form. Such materials include principally siliceousrnaterials, such as silica and metal sili cates,- including both artificial and naturally occurring clays, graphite, carbon black, metal. oxides of various types, suchas zinc oxide, magnesium oxide, aluminum oxide, etc., and organic pigments of various types, such as indigo and the phthalocyanines.

A preferred class of thickening agents for use in these greases comprises colloidal inorganic materials having at least a substantial part of their surface coated with a hydrophobic surface-active agent, either by adsorption, as disclosed, for example by F. H. Stross et al. in U.S. 2,65 8,869, or by chemical reaction between the inorganic material and the surface active compound as described, for example, by J. W. Jordan in US. 2,531,440. Particularly suitable materials or the latter type are the socalled onium clays, obtained by a base exchange reaction between a clay and a quaternary ammonium compound, preferably having at least one aliphatic hydrocarbon sub- .stituent group of ten or more carbon atoms, such as for example, dimethylethyldodecyl ammonium hydroxide, dimethy'lbenzyllauryl ammonium chloride, triethyloctadecyl ammonium chloride, etc. The reaction is preferably carried out employing at least about 40 per ent, and most suitably at least about 70 percent by Weight of the quaternary ammonium compound theoretically required for a complete reaction on the basis of the measured base exchange capacity of the clay.

The lubricating oils employed in these greases may be any suitable oils of lubricating characteristics ordinarily employed in lubricating greases, including the conventional mineral lubricating oils, synthetic oils contained by various refinery processes, such as cracking and polymerization, and other synthetic o-leaginous compounds, such as high molecular weight ethers, esters, silicones, etc. Suitable mineral oils include paraiiinic and naphthenic oils having viscosities in the range from about 80 seconds Saybolt Universal at 100 F. to about 225 seconds Saybolt Universal at 210 F., and preferably having viscosities in the range from about 100 to about 600- seconds Saybolt Universal at 100 F. Synthetic oils, inc1uding particularly the dicarboxylic acid esters, may be employed very advantageously to produce greases for operations at elevated temperatures.

Additives of the usual types may be employed in these greases, suchas, for example, oxidation inhibitors, corrosion inhibitors, anti-wear agents, tackiness agents, extreme pressure agents, and so forth. The grease preparation may be carried out by any suitable manner for accomplishing a thorough dispersion of the thickener and oxidate in the lubricating oil base, such as by milling the grease mixture in a colloid mill or in a paint mill. The mixing may be carried out at ordinary temperatures or at elevated temperatures up to about 300 F., or higher if desired, in order to dissolve any additives employed. In preparing greases thickened with inorganic colloidal materials treated with a hydrophobic surface-active agent, the preparation may be carried out by the so-called in situ method wherein the inorganic material is treated in the presence of all or a portion of the lubricating oil employed in the grease. The oxidate material may very suitably be added before or during this reaction.

The following examples are given for the more fully disclosing the invention.

EXAMPLE 1 p A grease representative of the lubricating compositions of this invention is obtained from the following materials in the indicated proportions by Weight:

purpose of Estersil 10.0 Oxidate 0.4 Mineral lubricating oil Remainder The mineral lubricating oil is a residual fraction of about 84 seconds Saybolt Universal viscosity at 210 F. from a mixed base crude.

The estersil is a finely divided amorphous silica which has been made oil wettable and Water resistant by esterification of the surface with ,butanol. It has a particle size of 8-10 millirnicrons and comprises 88-89 percent silica.

The oxidate is a material obtained by oxidizing a slack Wax having an oil. content of 6 percent. The oxidation is carried out in an aluminum reactor by passing air through the Wax containing 0.1 percent by Weight of potassium permanganate at 330 F. under a pressure of 65 pounds per square inch for 5.5 hours, employing an air feed rate of 15 cubic feet of air per hour per pound of charge. An oxidate is obtained having a saponification number of 535, a neutralization number of 294, a viscosity of 369 seconds Saybolt Universal at 210 F, and containing 4.1 percent by weight of unsaponifiable material. 'Phis oxidate is employed in the grease Without separation of any oxidate fractions.

The grease is prepared by mixing together the above materials in the indicated proportions and passing the mixture once through a Manton-Gaulin Homogenizer with valve settings at 5000 pounds and at 2500 pounds.

A buttery grease is obtained, having an ASTM worked penetration at 77 F. of 288, as compared with 351 for the base grease Without the oxidate and 341 for the same grease containing 1.0 percent by Weight of acetone as a dispersant in place of the oxidate.

EXAMPLE II A grease representative of a preferred embodiment of this invention is obtained from the following materials in the indicated proportions in percent by Weight:

in isopropyl alcohol solution, employing stoichiometric proportions of the reactants on the basis or the measured base exchange capacity of the bentonite.

The mineral lubricating oil is a blend in about a 4040 ratio by weight respectively of a refined parathnic residue oil having a viscosity at 210 F. of about 160 seconds, and a refined paratfinic distillate fraction having :1 Saybolt Universal viscosity at F. of about 182 seconds.

The sulfurized lard oil is a product obtained by heating lard oil with sulfur in the usual manner. Typical tests upon this material include a gravity, APT, of 12.8, a Saybolt Universal viscosity at 210 F. of 258 seconds and a sulfur content of 7.73 percent.

The oxidate is a Water washed fraction of a crude oxidate of the character described hereinabove, obtained by oxidizing a -127 F. melting point semi-refined wax containing about 0.4 percent by weight of oil, from. a parafiinic distillate fraction. The water Washing is carried out by mixing the oxidate with about twice its Weight of water at 15 0-170 F., settling and separating the water layer and dissolved oxygenates. This process is repeated twice.

The grease is prepared by mixing the organo-clay and additives into the mineral lubricating oil and milling in a Premier Colloid Mill with one pass at 0.003 inch clearance.

The following table shows typical results obtained by the use of the oxidates which are employed in accordance with this invention in the above grease composition, containing 8-10 percent of the organo-clay, 10 percent of sulfurized lard oil and one percent of tricresyl phosphate. These greases also contained one percent by Weight of finely divided carbon black as a colorant. Comparative data are included which were obtained upon this composition containing petroleum oxidates of two different types, representative of petroleum oxidates which have been employed heretofore in lubricant compositions for various purposes, and also upon the composition containing acetone, which is commonly recommended as a dispersant in bentone-type greases, In the table, Oxidate A is a 'water washed oxidate having aneutralization number of 182, a saponification number of 283, a non-saponifiable content of 16 percent, and a Saybolt Universal viscosity at 210 F., of about 56 seconds, from a crude oxidate having a neutralization number of about 250, obtained by blowing air through the wax charge containing 0.4 percent by weight of potassium permanganate for 6.5 hours while the charge is maintained at 270 F. and under a pressure of 65 pounds per square inch gauge, employing an air rate of 20 cubic feet of air per hour per pound of charge. Oxidate B is a Water washed oxidate having a neutralization number of 232, from a crude oxidate having a neutralization number of 343, a saponification number of 515, a nonsapom'fiable content of 2.8, and a Saybolt Universal viscosity at 210 F. of about 98 seconds, obtained by blowing air through the wax charge containing 0.4 percent by weight of potassium permanganate for 11.5 hours while the charge is maintained at 270 F. and under a pressure of 75 pounds per square inch gauge, employing an air rate of 13.3 standard cubic feet of air per hour per pound of charge. Oxidate C is a water washed oxidate having a neutralization number of 60 and a saponification number of 193, from an oxidate obtained by oxidizing a paraffin wax of the type described above under difierent conditions which resulted in an oxidized product having a neutralization number of 72, a saponification number of 242, a non-saponifiable content of 29.6 percent and a Saybolt Universal viscosity at 210 F. of 134. Oxidate D is a water Washed oxidate having a neutralization number of 101 and a saponification number of 211, from an oxidate obtained by oxidizing a refined parafiin distillate oil having a Saybolt Universal viscosity at 100 F. of about 150 seconds, the crude oxidate having a neutralization number of 94, a saponification number of 267, a non-saponifiable content of 17.5 percent and a Saybolt Universal viscosity at 210 F. of about 196 seconds.

As shown by the above table, a yield advantage represented by about 20 points in ASTM worked penetra tion is obtained in this grease composition by employing 0.3 percent by weight of the highly oxidized wax oxidates described above. With Oxidate A, having a neutralization number of about 180, the effectiveness is optimum at about 0.3 percent concentration, and decreases rapidly with higher amounts of the oxidate. With the more highly oxidized Oxidate B, the effectiveness is likewise optimum at about 0.3 percent concentration but remains about constant up to a concentration of about 2.0 percent and thereafter decreases. On the other hand, only a very small yield advantage is obtained with 0.3 percent of the wax oxidate having a neutralization number below 100 (Oxidate C), and no improvement is obtained with the 101 neutralization number oxidate obtained by oxidizing a lubricating oil fraction (Oxidate D). Acetone is not an etfective dispersant in this grease, containing a sulfurized fat and tricresyl phosphate as extreme pressure 6 additives, as shown bythe penetrations obtained upon Grease No. 5.

Timken tests on the above greases showed no increase in extreme pressure properties with Oxidate A at concentrations up to and including 0.5 percent. With the higher neutralization number oxidate, an improvement in the Timken values was obtained starting with about 2.0 percent concentration and increased with increasing concentration of the oxidate, while the yield improvement de creased.

EXAMPLE III A grease representative of a different embodiment of this invention is obtained from the following materials in the indicated proportions in percent by weight:

Carbon black 10.0 Oxidate 0.5 Mineral lubricating oil Remainder The mineral lubricating oil in the above formulation is a residual fraction of about seconds Saybolt Universal viscosity at 210 F. from a mixed base crude.

The oxidate is a material having a neutralization number of 311, a saponification number of 482, a non-saponifiable content of 5.3 and a viscosity Saybolt Universal at 210 F. of about 66, obtained by oxidizing a refined parafiinic distillate oil having a Saybolt Universal viscosity at F. of about seconds under conditions including a temperature of 300 F., a pressure of 250 pounds per square inch gauge and an air rate of 20 standard cubic feet of air per hour per pound of charge, employing 0.6 percent by weight of potassium permanganate in the charge.

The carbon black is a commercial channel black having a measured surface area of 280 square meters per gram.

The grease is prepared by mixing together the above materials and milling in a Charlotte mill at 0.004 inch clearance.

The grease described above is a soft smooth grease having a dropping point above 500 F. and an ASTM worked penetration of 320, as compared with 338 for the grease without the wax oxidate.

EXAMPLE IV A grease representative of a still different embodiment of this invention is obtained from the following materials in the indicated proportions in percent by weight:

Indigo 35.0 Diphenyl-p-phenylenediamine 1.0 Tricresyl phosphate 3.0 Mineral oil 4.3 Oxidate 0.5 Synthetic ester Remainder The synthetic ester is obtained by reacting together sebacic acid, 2-ethylhexane-1, 3-diol and 2-ethylhexano1 in about a 2:1:2 ratio, respectively, and consists predominantly of the compound The mineral oil is a refined paraffinic distillate oil having a Saybolt Universal viscosity at 100 F. of 330 seconds. The indigo is the dye grade product having an average particle size of about 0.1 micron diameter and a measured surface area of about 10 to 50 square meters per gram. The oxidate is the lower boiling 10 percent cut of the oxidate described in Example III, having a neutralization number of 641.

The grease is prepared by mixing the indigo and oleaginous base containing the oxidate by means of an electric stirrer until a smooth paste is formed. The inhibitors are then added and the grease is finished by milling with two passes through a Premier Colloid Mill at 0.002 inch clearance.

acreage The grease described above is a soft, smooth grease having a dropping point of about 500 F. and an ASTM worked penetration at 77 F. of about 360, as compared with about 371 for the grease without the oxidate.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim: a

1. A lubricating grease consisting essentially of a major proportion of an organic lubricating oil having incorporated therein a finely divided normally solid gelling agent selected from the group consisting of silica, metal silicates, and hydrophobic combinations and reaction products thereof with organic hydrophobic surface active compounds, graphite, carbon black, metal oxides, indigo and phthalocyanines, said gelling agent being present in suflicient amount to form a grease, and about 005-20 percent by weight of the grease composition, a petroleum oxidate having a neutralization number of about 150- 550 and a ratio of neutralization number to saponification number of at least 0.5, obtained by reacting a parafiinic distillate fraction selected from the class consisting of lubricating oils and waxes with air at a term perature in the range 200 F.-4-00 F. under a pressure of about 30-500 pounds per square inch gauge, with an air feed rate of -60 cubic feet of air per hour per pound of charge until an oxidized product having a neutralization number in about the range 200-550 is obtained, said oxidate being present in the grease in an amount suihcient to impart increased hardness to the composition on the basis of its ASTM workedpenetration at 77 F. but below the amount required to impart improved extreme pressure properties to the composition.

2. A lubricating grease according to claim 1 wherein the said oxidate has been separated from water-soluble oxidates by water washing.

3. A lubricating grease according to claim 1 wherein the said paraflinic distillate fraction is reacted with air at a temperature in about the range 250-350 F. and under a pressure of about 30-300 pounds per square inch gauge.

4. A lubricating grease according to claim 1 wherein the said oxidate is a water washed fraction of a crude oxidate having a neutralization number in about the range 250-550, and a ratio of neutralization number to saponiiication number of at least about 0.6.

5. A lubricating grease according to claim 1 wherein the said gelling agent is an inorganic colloidal material having at least a substantial portion of its surface coated with an organic hydrophobic compound.

6. A lubricating grease according to claim 5 wherein the said gelling agent is bentonite which has been treated with a quaternary ammonium compound containing at least one aliphatic hydrocarbon group containing at least 10 carbon atoms.

7. A lubricating grease according to claim 1 contain ing a minor amount of a sulfurized fatty oil.

8. A lubricating grease according to claim 1 wherein the said oxidate is present in an amount of about 0.1-1.0 percent by weight.

9. A lubricating grease consisting essentially of a mineral lubricating oil as the major component, about 7-12 percent by weight of bentonite treated with a dimethyldistearyl ammonium salt, about 5-15 percent by weight of sulfurized lard oil, about 0.5-3 percent by weight of tricresyl phosphate and about 0.1-1.0 percent by Weight of a petroleum oxidate having a neutralization number of -550 and a ratio of neutralization number to saponification number of at least about 0.6, obtained by reacting a parafiinic distillate fraction selected from the class consisting of lubricating oils and waxes with air at a temperature in about the range 270 F.-330 F, under a pressure of 30-300 pounds per square inch gauge and with an air feed rate of 10-60 cubic feet of air per hour per pound of Wax charge until an oxidized product having a neutralization number in about the range 200-550 is obtained, said oxidate being present in the grease in an amount sui'licient to impart increased hardness to the composition on the basis of its ASTM Worked penetration at 77 F. but below the amount requir d to impart extreme pressure properties to the composition.

References (Iited in the file of this patent UNITED STATES PATENTS 1,863,004 Burwell June 14, 1932 2,043,923 Burwcll June 9, 1936 2,243,420 Frolich May 27, 1941 2,531,440 Jordan Nov. 28, 1950 2,652 365 Moore et al Sept. 15, 1953 2,812,306 Liehe Nov. 5, 1957 2,859,234 Clem Nov. 4, 1958 2,862,803 Oosterhout Dec. 2, 1958 2,881,140 Schrum Apr. 7, 1959 2,894,970 Mcfinley et al July 14, 1959 OTHER REFERENCES Boner: Manufacture and Application of Lubricating Greases, Reinhold Pub. Corp, N.Y., 1954, p. 738.

Claims

1. A LUBRICATING GREASE CONSISTING ESSENTIALLY OF A MAJOR PROPORTION OF AN ORGANIC LUBRICATING OIL HAVING INCORPORATED THEREIN A FINELY DIVIDED NORMALLY SOLID GELLING AGENT SELECTED FROM THE GROUP CONSISTING OF SILICA, METAL SILICATES, AND HYDROPHOBIC COMBINATIONS AND REACTION PRODUCTS THEREOF WITH ORGANIC HYDROPHOBIC SURFACE ACTIVE COMPOUNDS, GRAPHITE, CARBON BLACK, METAL OXIDES, INDIGO AND PHTHALOCYANINES, SAID GELLING AGENT BEING PRESENT IN SUFFICIENT AMOUNT FROM A GREASE AND ABOUT 0.05-2.0 PERCENT BY WEIGHT OF THE GREASE COMPOSITION, A PETROLEUM OXIDATE HAVING A NEUTRALIZATION NUMBER OF ABOUT 150550 AND A RATIO OF NEUTRALIZATION NUMBER TO SAPONIFICATION NUMBER OF AT LEAST 0.5, OBTAINED BY REACTING A PARAFFINIC DISTILLATE FRACTION SELECTED FROM THE CLASS CONSISTING OF LUBRICATING OILS AND WAXES WITH AIR AT A TEMPERATURE IN THE RANGE 200* F,-400* F. UNDER A PRESSURE OF ABOUT 30-500 POUNDS PER SQUARE INCH GAUGE, WITH AN AIR FEED RATE OF 10-60 CUBIC FEET OF AIR PER HOUR PER POUND OF CHARGE UNTIL AN OXIDIZED PRODUCT HAVING A NEUTRALIZATION NUMBER IN ABOUT THE RANGE 200-550 IS OBTAINED SAID OXIDATE BEING PRESENT IN THE GREASE IN AN AMOUNT SUFFICIENT TO IMPART INCREASED HARDNESS TO THE COMPOSITION ON THE BASIS OF ITS ASTM WORKED PENETRATION AT 77* F. BUT BELOW THE AMOUNT REQUIRED IN IMPART IMPROVED EXTREME PRESSURE PROPERTIES TO THE COMPOSITION.