USRE23082E

USRE23082E - Grease compositions

Info

Publication number: USRE23082E
Authority: US
Publication date: 1949-01-25

Description

Jan. 25, 1949. J. c. ZIMMER ErAL GREASE COMPOSITION Original Filed Dec. 30, 1944 ...m0 .mdnbmuubl (.20 .du ,rmuw mdjmwmd John C. Zimmer nverzbors Gcrcfon. ZJ'. Duncan.

Reinoud 1949 GREASE CQMPOSITIONS John C. Zimmer, Union, and Gordon W. Duncan,

Westfield, N. J., allignors to Standard il Development Company. a corporation of Delaware vOriginal No. 2,444,970, dated July 13, r194:8, Serial No. 570 85, December 30, 1944.

September 25. 1948, Serial No. 51,132

Claims. (Cl. 25H32) for reiss The present invention relates to improved grease compositions, particularly reversible greases which are transparent, mechanically and thermally stable, and adapted for use in lubricated-for-life bearings or under conditions where either high temperatures, water contamination or both are encountered. Reversible greases are those grease compositions which can be heated to above their melting point and upon being cooled revert to their original consistency.

Many types of mechanical mechanisms including electrical motors and generators operate at such high speeds that high bearing temperatures are generated or equipment is installed in close proximity to a direct source oi' heat, which results in the operation of the equipment at high temperatures. If the design of the equipment or its location necessitates the use of a grease as the lubricant, then high temperature creates a diflicult lubrication problem. Although not unique in this respect, electrical generators, such as those attached to internal combustion engines, for example aircraft or Diesel locomotives provide a typical example of the requirement in high temperature lubrication. In their construction.

these generators contain sealed and lubricated anti-friction bearings, which it is contemplated will not need replacement or relubrication during the life of the generator. When the engines to which these generators are attached are operated over an extended period of time these generators, due to heat radiation, conduction, and other causes, attain temperatures which ordinary greases will not withstand. Circumstances such as these require the use of a high melting point grease, resistant to elevated temperatures. High temperature greases are customarily made using an alkali, such as sodium, Vand in order to obtain the high melting point required in a high temperature grease, a considerable excess of alkali over that needed to neutralize the fatty acid is commonly employed. High temperature greases containing excess alkali, although they possess the desired highmelting point, are deficient in several other respects. They tend to be watersoluble and readily disintegrate in contact with moisture or under humid conditions, and unless proper care is taken in selecting the fatty acid from which the alkali soap is made, evidence a strong tendency to be unstable during storage in that the soap fails to hold the oil, as manifest by free oil which has separated from the grease. Furthermore, high temperature greases containing an excess of alkali are subject to operational dimculties in that at temperatures above about Application 180 F. they may become stiff and develop a fibrous structure, and wrap themselvesaround a rotating shaft and t'hus be pulled out of its bearing, losing the soit buttery consistency desired in greases. This is particularly so when the grease is prepared from fatty oils or fatty acids containing unsaturated constituents such as oleic or linoleic acid, etc. 'Ihis tendency of a high temperature alkali grease to change its grease structure at high temperatures can be shown by an irregular resistance to flow under pressure in the range of temperatures above F. up to the melting point of the grease.

The principal object of the present invention is to produce a grease composition which will provide adequate lubrication at both high and low temperatures, and one that will not at high temperatures tend to pull out of the bearing because of its fibrous structure or break down to a semifluid liquid under the churning action. or torque of the mechanism lubricated. Another object is to provide a high temperature grease which is stable against oil separation during storage. Other and further objects such as water insolubility, oxidation stability, etc.,.will be apparent to those skilled in the art 4from-a reading of the following description.

The grease compositions made in accordance with the present invention comprise essentially a mineral lubricating oil and th'e reaction product of a salt of an oil-soluble sul-ionic acid with a salt of another acid, wherein `at least one of the metal ions is polyvalent, although other ingredients may be included in the grease compositions such as dyes, other grease-making soaps, fillers, inhibitors, E. P. additives, tack or stringiness promoters, and the like. In addition modifying agents such as mono or polyhydroxy compounds, organic bases, metal soaps, esters, phosphate esters and thioesters, xanthates, fatty oils. sulfurized materials, sulfur and chlorine-containing compounds, phenates, phenol sulfldes, phosphorous sulfide treated materials. alkylated phenols, aryl or alkyl' amines, alkanol amines, metal deactivators, etc., may be included. The metal ion of both the oil-soluble metal sulfonates and the reactant salts may be almost any desired providing the corresponding compound and the acid radicals are suitably chosen. In general, metals of either group I, such as sodium or lithium yor group II, such as calcium or magnesium, of the periodic table, are preferred a1- though for some purposes other metals such as zinc, tin, lead, aluminum or organic bases may be employed. In most cases salts of nitrogen causa oxide acids or low molecular weight organic acids are preferred for reaction lwith the oil-soluble metal sulfonate although phosphates. chromates. manganates, molybdates, stannates may also be employed. If the cation of the oil-soluble sul-- ionate is a polyvalent metal such as calcium. magnesium or barium, then the cation of the reactant salt may be a monovalent metal such as sodium. potassium, lithium, etc., an organic base or a polyvalent metal such as magnesium. calcium, barium, zinc, lead. etc. On the other hand, where the cation of the oil-soluble sulfonate is monovalent such as sodium or is an organic base,

Y high molecular weight (350-500 or more broadly 300 to 600) acids, particularly those produced when treating petroleum distillates with turning areactantsaltmustbeselectedhavingapoly- Y valent metal ion such as calcium, barium. magnesium or lead.

In general, maximum bodying or thickeningand melting point raising eileets are obtained by employing an amount oi reactant salt auch that the number of anions of the reactant approximates the number of sulfonate ions present. Smaller amounts of the water-soluble constituents yield a softer and lower melting product, whereas amounts in excess of that indicated above tend to give cloudy products with little further increase in hardness or melting point. s

Since the presence of certain ions as impurities in the sulfonate solution tends to block the formation of the desired grease, e. g., chloride ion in the case of calcium sulfonate-calcium acetate complex greases, such ions must be removed or inactivated.- In the. above example, the chloride may be removed by water washing or, if an absolutely clear grease is not required, the chloride may be inactivated by incorporating sufilcient lead acetate with the calcium acetate to combine all the chloride ions as insoluble lead chloride. Some calcium sulfonates as manufactured contain calcium hydroxide as an impurity or combined as a complex with the sulfonate. In this case, reaction with the desired free acid may be employed to form the grease structure or the grease may be-left alkaline with no adverse eiect. Y

Experience has established in grease making and in the use of greases that it is best practice to select as the lubricating oil in the grease an oil of the same type as would have been selected if a liquid lubricant could be used. A wide range of lubricating oils is therefore permissible in grease production. In general, the base oil in the compositions of the present invention comprises an oil having S. U. V. in the range of from about 30 to 220 seconds at 210 F. However for the production oi most greases of the type contemplated by this invention, it is preferred to use a base oil having a viscosity of from 100 to 2,500 at 100 P.

The oil-soluble metal sulfonates previously referred to may be synethetically derived by sulfonating olens, aliphatic fatty acids, or their esters, alkylated aromatics or their hydroxy derivatives, partially hydrogenated aromatica. etc., with sulfuric acid or other sulfonating agents. However the soaps oi' so-called mahogany acids which are usually produced during treatment of lubricating oil distillates with concentrated sulfuric acid (85% or higher concentration) remain in the oil after settling .out sludge. These sulfonic acids may be represented as whereRisoneormorealkyLalkaryloraralkyl groupsandthearomaticnucleusmaybeasingle acid to produce white oil, are normally recovered as sodium soaps by neutralizing the acid oil with sodium hydroxide or carbonate and extracting with aqueous alcohol. The crude soap extract is iirst recovered asa water curd after removal of alcohol by distillation and a gravity separation oi' some-oi' the contaminating salts (sodium carbonate, sulfates and suliltes). These materials still contain considerable quantities of salts and" consequently are normally purled by addition o! a more concentrated alcohol followed by storage to permit settling of salt brine. The alcohol and water are then stripped out and replaced with af light lubricating oil to yield the commercial purified concentrate, generally containing from 2570% sodium sulfonate.

Polyvalent metal sulfonates are prepared from acid-treated oils or extracted sulfonic acids by neutralizing directly with an oxide, hydroxide or carbonate of the desired metal or direct reaction of the acid with metals such as zinc or magnesium. AHowever itis often more movement to prepare them from the sodium salt by double decomposition. Thus, the polyvalent metal salts may be made by precipitating the sodium sulfonates from alcoholic solutions with a polyvalent metal salt. For example, the calcium metal sulfonate may be prepared by precipitating from alcohol solutions with calcium chloride, inorganic salts being then removed by washing with water. The calcium sulfonates are then dehydrated in the presence of suiilcient oil to yield an ultimate concentrate containing from 10-60% of calcium sulfonate in oil. Or an oil solution of sodium sulfonate may be emulsitiedwith an aqueous solution of a polyvalent metal salt followed by dehydration and separation of the inorganic sodium salt formed.

It has now been found that oil-soluble sulfonates like alkali metal sulfonates such as the sulfonates of sodium, potassium and lithium; al-

kalme earth metal sulfonates such as the sulfonates of calcium and barium; other polyvalent metal sulfonates like those ofmagnesium, lead. copper, nickel, iron. zinc, aluminum. etc.; as well as the oil-soluble aliphatic amine sulfonates of which the di-Z-ethylhexyl-amine, cyclohexylaminel oleyl amine sulfonates are examples, can

v be converted to complex coordination compounds of the so-called Werner type which are lyophilic but not oil-soluble and which have the property of thickening lubricating oils to yield plastic high melting' point grease-like solids. 'I'he conversion of oil-soluble sulfonates to the oil-soluble complex is accomplished by reacting the oil-soluble sulfonate with a water-soluble salt of a nitrogen oxide acid such as a'nitrite or nitrate or the oilsoluble sulfonate can be reacted with a watersoluble salt of a low molecular weight carboxylic acid of which the acetate, oxalate, formate, tartrate, succinate. citrate, propionate, lactate, glycolate and Amalate are exemplary. Other watersoluble salts which may be employed alone or in combination are sulildes, thio suliltes, thio sulfates, thio xanthates, silicates, nuo silicates, borates. xanthates. etc. The formation of an oil-soluble complex depends upon the presence in the reaction of a polyvalent cation, and it is "amne n'eass'm mariana t". i1-sonne calcium, barium, lead, tin, etc. n the other hand, oil-soluble sulfonates containing monovalent cations such 'as sodium, potassium and lithium or an aliphatic amine radical must be reacted with a salt having a polyvalent metal cation.

The high temperature grease compositions of the present invention are preferably made by rst preparing a solution of the oil-soluble sulfonate in a mineral lubricating oil of the type desired, emulsifying theoil solution with an aqueous solutionor solution-suspension of the reactant salt, and dehydratingby boiling to vform the complexbodied grease. In the reaction mixture itis genlerally desirable Ito include a defoaming agent to prevent the occurrence of excessive foam during dehydration. One may also feasibly prepare the complex separatelyusually as a curdy emulsion and then incorporate it in the desired mineral lubricating .oil after the manner customarily employed in the production of grease compositions.

Ii-desired the separate components may be continuously metered by pumps into a mixing chamber in the desired proportion and the blended materials removed from the chamber, passed through homogenizlng or dispersing mechanisms, such as a Lancaster disperser, a centrifugal or a gear pump, cooled in a helical screw or jacketed cylindrical cooler and filled directly into shipping containers using the procedure known to the art for the production of greases by continuous rather than batch or kettle processes.

A practical means of preparing grease compositions of the present invention is to select an oil of the desired characteristics, treat it with concentrated sulfuric acid or other sulfonating agent to form the desired concentration of sulfonic acids in the oil, separate` the oil from tl'ie sludge formed, air blow to remove sulfur dioxide. neutralize the sulfonic acids by treatment with an oxide, hydroxide or carbonate of the desired metal, illter to remove inorganic salts, and react the resultant oil solution with an aqueous solution of the desired reactant salt. A variation of this method is to employ a double amount of the reactant salt in the sulfonic acid oil solution, the acid of the reactant salt being stripped out during dehydration. The melting point and consistency oi the nnal grease will depend directly upon the proportion and character of the oomplex in the finished grease. The oil-soluble sulfonates have combining weights ranging from 300 to 600 i. e., based on sulfonic acids of about 300 to 600 molecular weight, the choice of which is somewhat influential upon the character of the nal grease. The amount of sulionate complex present in the finished grease will range between about 0.5% for the fluid greases, up to 50% in the extremely hard greases. The exact .amount of complex to be incorporated in the nished grease is controlled by the type of grease and consistency desired. Where the sulfonate complex is made "in situ" in the mineral lubriy eating oil, two avenues of approach are open for securing the desired results. A mineral lubricating oil containing a ilxed amount such as 1, 5. 10.

20 or even 50% of soluble-sulfonate can be se lected and this solution is then reacted with suillcient of the water-soluble reactant to yield a grease containing the desired amount of sulionate complex or in other words, the desired consistency and melting point. On the other hand, an oil may be selected containing just enough soluble sulfonate dissolved therein to yield the desired amount of sulionate complex when reacted on an anion per anion basis. The foregoing reactions may be carried out at room temperature, but in general it is desirable to emul- "sify the oil solution of sulfonate and the aqueous solution of the reactant at temperatures below the boiling point of water followed by heating made at temperatures above 240 F. the finished product will be substantially'anhydrous.

The following example will serve to illustrate the specific embodiment of the invention:

Example A steam-jacketed scraped-wall grease kettle was charged with 3,000 grams of a 30% concentrate of calcium sulfonate (approprixmately 900 mol. wt.) and 3,000 grams of a 65 viscosity at 210 F. naphthenic distillate oil was blended in by agitating at 180 F. to 200 F. When the solution was complete, 180 grams of calcium acetate as an 18.4% aqueous solution was added, emulslilcation taking place immediately. Five drops of an organic silicon polymer was added to control foaming and the temperature rapidly brought up to 250 F., a grease structure having started to develop at 230 F. Cold water was introduced into the jacket of the kettle and stirring continued until the grease had reached a temperature of 100 F. at which point it was removed and packaged. A clear, bright grease having thefollowing characteristics was obtained.

Melting point In excess of 400 F. Penetration at 77 F. 242 Worked penetration 278 The grease was quite resistant to breakdown through contact with water, as measured by directing a stream of water against a revolving frictionless bearing packed with the grease, and, in a pressure viscosimeter, no substantial change in consistency was noted between the temperatures of F. and 350 F.

The plotted results of pressure-viscosity determinations in the range from 70 F. to 350 F. in several typical greases are shown in the accompanying drawing wherein curve A shows the pressure in pounds per square inch developed in a pressure viscosimeter by the grease made in accordance with the example of the specification. The values for curve B were obtained by testing a conventional soda base grease. Curve C represents a mixed soda lime base grease and curve D a lime soap grease. A line of demarcation is indicated in the drawing at 5 pounds per square inch pressure since it is probable that a grease having `this low resistance to flow would tend to leak out of a small clearance under very slight stress.

What is claimed is:

1.. A grease composition comprising a mineral lubricating oil and sufilcient of the complex reaction product of an oil-soluble metal salt of sulfonic acid, said acid having a combining weight of approximately 300 to 600, and a salt o1 an acid selected from the group consisting oi' low molecular weight. aliphatic carboxylic acids, in which at least one cation in the above salts is polyvalent. to thicken the mineral oil to a grease consistency. said complexreaction product being produced by dissolving said sulionate ln said mineral oii and reacting said sulfonate with said salt in the presence o! heat.

2. A grease composition according to claim 1 wherein the thickening agent is a complex reac tion product of an oil-soluble sodium sulfonate" and calcium acetate.

3. A grease composition according to claim l wherein the thickening agentia a complex reac tion product of an oil-soluble calcium sull'onate and calcium acetate.

4. A grease composition as dened in claimV 1 in which the salt is lithium acetate. 5. A grease composition comprising a mineral lubricating oil and .5-5096 of the complex reaction product of an oil-soluble metal sulfonate and a salt of an acid selected from the group consisting of low molecular weight aliphatic carbowlic acids, in which at least 1 cation in the above salts is polyvalent, said complex reaction product being produced by dissolving said sulfonate in said mineral oil and reacting said sull'onate withsaid salt in the presence of heat.

6. A grease composition comprising a mineral.

lubricating oil and 520,% of the complex reaction product of an oil-soluble metal sulfonate and a salt of an acid selected from the group consisting of low molecular weight aliphatic carboxylic acids, in which at least `1 cation in the above salts is polyvalent, said complex reaction product being produced by dissolving said sulfonate insald mineral eiland reacting said vsul- 'Ionatewithsaldsaltinthepresenceotheat 'LAgreasecomppationcompcisingamlneral" lonate complex coordinationcompound capable' 4oi' thickening oil, formed by reacting an oil solution of a sulfonate salt with an aqueous solution of a salt of a low molecular weight aliphatic carboxylic acid, ln vwhich at least one of the metallic elements ot said salts is polyvalent.

9. A method of manufacturing grease comprising reacting in the presence of heat an oil solution of a sulionate salt with an aqueous solution of a salt of a low molecular weight carboxylic acid capable of reacting with the suli'onate to give an oil-bodying lyophiiic complex coordination compound, the metallic element ot at least one oi' said salts being Wma-lent.

l0. An anhydrous grease composiidonV comprising a mineral lubricating oil and about 15% of a complex calcium sulfonate. said complex calcium sulionate being produced in situ in the mineral lubricating oil by blending a 30a', oil solution ofcaicium sulfonate` with an equal amount of mineral lubricating oill then adding y3% ol an aqueous solution ot calcium acetate of aboutV 18% of calcium acetate in water, heating to 250 F.

and cooling.

JOHN C. ZIMMER.

GORDON W. DUNCAN.V

No references cited.