US2929781A - Process for making a lithium-calcium base grease - Google Patents

Description

March 22, 1960 A. BEERBOWER EVAL 2,929,781

PROCESS FOR MAKING A LITHIUM-CALCIUM BASE GREASE Filed April 18, 195e 2 Sheets-sheet 1 I March 22, 1960 PROCESS FOR MAKING A LITI-iIUM-CALCIUM BASE GREASE Filed April 18, 1956 A. BEERBOWER EVAL 2 Sheets-Sheet 2 Alan Beerboyer Rosemar O Halloran Hans G.

sferdal United States Patent PROCESS FOR MAKING A LITHIUM-CALCIUM BASE GREASE Application AprilV 18, 10956, Serial No. 579,037

1 Claim. (Cl. 252-40) This invention relates to a new and improved method ior manufacturing lubricating grease compositions. More particularly, this invention relates to a process for the preparation of lubricating grease compositions containing lithium and calcium soaps of high molecular weight fatty acids in molar ratios of from about 2:1 to 8:1 mols of lithium soap to mols of calcium soap. The invention is. especially adapted for continuous or semi-continuous manufacture of such greases.

Lubricating grease compositions containing lithiumcalcium -soap thickeners are known in the prior art. ILS.V Patents 2,641,577 and 2,646,401 describe in Vdetail V,composition and preparation of such lubricating greases. These` greases were prepared bysaponifying saturated or unsaturated fatty acids with calcium hydroxide and an aqueous solution of lithium hydroxide in the presence of mineral lubricating oil. Dehydration was then effected by heating the grease until it melted and then, subsequently pan-cooling, stirring-down and milling. It has also been recently suggested that lithium-calcium `soap thickened greases could be prepared from the more Y Saturated fatty acids by dehydrating the grease mixture at; temperatures below the melting point of the grease or soap thickener. By employing the latter method, the expensive and time consuming pan-cooling and stir-down steps are eliminated.

I-.u accordance with the present invention, it has now been found that lithium-calcium soap thickened greases may be economically produced on a continuous or semicontinuous basis. More specifically, it has been discovered that a mixed soap-oil concentrate can be prepared with dry calcium hydroxide and dry lithium hydroxide monohydrate in a closed system under a pressure of about 60 to 150 p.s.i.g'. and at a temperature within the range of about 29.0 to 375 F. This soap-oil concentrate, containing from aboutV 40 to 75 weight percent of the lithium and calcium soaps can then be diluted with additional oil in. a continuous soap concentrate-oil blender to give an outstanding multipurpose grease thickened with from about 8 to 14 weight percent of the lithium and calcium soaps and useful for automotive, aircraft and industrial lubricating services.

In addition to the obvious advantages afforded by the inycntive grease-making process in lending itself readily to continuous or semi-continuous operation, other advantages; accrue from the fact that only about one iifth of the grease need be heatedV to the high cooking tempera.- tures. and dehydrated and, furthermore, from the elimination; of the need'for evaporating the water used in the prior art process in making upthe lithium hydroxide and the calcium hydroxide reactants.

Thus, broadly, the present invention comprises the essential features of (l) preparing a soap-oil concentrate containing lithium soap and' calcium soap in a closed system under a pressure of about 60 to 150 p.s.,i.g. and ai temperature of about 290 to 375." F. and (2) diluting such grease concentrate with additional oil in a con- ICC tinuous or semi-continuous operated soap concentrate-oil blend.

In preparing the grease compositions of the invention, the oil employed both in making the grease concentrate and in subsequently diluting the concentrate to obtain the desired proportion of oil in the nished grease compositoin may be any of the conventionally used mineral or synthetic lubricating base stocks. In general, these lubricating oils should have a viscosity of about 50 to 2,000 SUS at F. and about 35 to 200 SUS at 210 F., an A.S.T.M. pour point of about +20 to -75 F., a liash point of about 350 to 650 F., and a Viscosity Index of about 0 to 60 or higher. Conventionally refined and treated mineral oil base stocks derived from paraiiinic, naphthenic and mixed base crudes having the properties listed above are especially useful in preparing the grease compositions of this invention.

The synthetic lubricating oils which may also be employed include esters of monobasic acids (c g. an ester of C8 Oxo alcohol with C8 Oxo acid, an ester of C13 0x0 alcohol with octanoic acid, etc.), esters of dibasic acids (e.g. di-2-ethyl hexyl sebacate, di-nonyl adipate, etc.), esters of glycols (eg. C13 Oxo acid diester of tetraethylene glycol, etc.), complex esters (eg-the complex ester formed by reacting one mol of tetraethylene glycol with two mols of sebacic acid and two mols of Z-ethyl-hexanol; the complex ester formed by reacting one mol of tetraethylene glycol, one mol of C8 Oxo alcohol, one mol of adipic acid, and one mol of C8 Oxo acid, etc.), esters of phosphoric acid (eg. the ester formed by contacting three mols of the mono-methyl ether of ethylene glycol with one mol of phosphorous oxychloride, etc.), halocarbon oils (eg. the polymer of chlorotrifluoroethylene containing twelve recurring units of chlorotriiiuoro- `ethylene), alkyl silicates (eg. methyl polysiloxanes, ethyl polysiloxanes, methyl-phenyl polysiloxanes, etc.), sulite esters (e.g. ester formed by reacting one mol of sulfur oxychloride with two moles of the methyl ether of ethylene glycol, etc.), carbonatos (e.g. the carbonate formed byy reacting C8 Oxo alcohol with ethyl carbonate to form a half ester and reacting this half ester with tetraethylene glycol), mercaptals (e.g. the mercaptal formed by reacting Z-ethyl hexyl mercaptan with formaldehyde),.formals e.g. the formal formed by reacting C13 Oxo alcohol with formaldehyde), polyglycol type synthetic oils (eg. the compounds formed by condensing butyl alcohol with fourteen units of propylene oxide, etc.), or mixtures of the above in any proportions.

The mol ratios of the lithium soap to the calcium soap used in preparing the grease compositions of the invention may vary from about 2:1 to 8:1, the preferred mol ratio range being about 3:1 to 6:1.

The naturally occurring or synthetic fats or fatty acids employed in formulating the above soaps may be any of the commonly known grease-making materials. Examples, of these materials include saturated or unsaturated fatty acids having iodine numbers within the range of Oto and having about 12 to 30, preferably about 14 to 22, carbon atoms per molecule, such as lauric, myristic, palmitic,V stearic, l2-hydroxy stearic, 9,10-dihydroxy stearic, behenic, myrstoleic, palmitoleic, oleic, linoleic, cottonseed oil fatty acids, palm oil fatty acids, hydrogenated fish oil fatty acids, lignoceric, ricinoleic, erucic acids and their mixtures and/or their glycerides such as lard, beef, rapeseed, palm, menhaden, herring, castor oils, etc.

The proportions in which the mixed soaps and oils should be employed in order to make the soap-oil concentrate in the iirst step should be about 20 to 85%, preferably about 40 to 70%, of the mixed soaps and about 15. tor 8,0%, preferably about 30 to 60%, of the oil base. The finished grease compositions of the invention will:

lordinarily contain about to 20%, preferably about 8 to '14%, of the lithium and calcium soaps and about 80 to 95%, preferably about 86 to 92%, of the oil.

Minor amounts, in the order of about 0.01 to by weight, of conventional lubricating grease additives lcan also be incorporated in the grease compositions of this invention. Examples of such additives include oxi- Edation inhibitors, corrosion and rust inhibitors, extreme pressure agents, metal deactivators, stn'nginess additives and the like. In general, the lubricating grease compositions of the invention may be prepared by charging a portion of lubricating oil, about 2 to 10% of the total oil employed in preparing the linished grease composition and dry hydrated lime to a rapid soap cooker, Stratco contactor or a similar vessel capable of being used for pressure saponiication. See Boner, Manufacture and Application of Lubricating Greases (Reinhold Publishing Corp., New York, 1954), pages 251 to 255, for a detailed description of such equipment.

The oil and hydrated lime are intimately mixed to obtain a slurry, and then the soap forming fat or fatty acid material is added, followed by the addition of dry lithium hydroxide monohydrate. Alternatively, the lithium hydroxide monohydrate may be added with the lime to the slurry. The resulting mixture is then heated in the closed system to a temperature within the range of about 290 to 375 F., preferably about 300 to 340 F. and at a pressure of about 60 to 150 p.s.i.g., preferably about 75 to 125 p.s.i.g., for about l0 to 60 minutes. The pressure of the cooker or vessel is then reduced and vacuum applied to effect substantially complete dehydraation. Alternatively, the soap concentrate may be dehydrated under vacuum in a separate unit such as a. Cornell homogenizer.

Following dehydration, the soap concentrate is mixed or blended with additional oil in a high speed mixer or disperser such as a Lancaster mixer to obtain the desired grease consistency. The oil blended with the soap concentrate will ordinarily be cold, i.e. at ambient temperature or about 50 to 100 F. Only enough additional oil to result in a grease mixture having an oil concentration of about 10 to 20% need be added at this stage of the process. The iinal portion of the oil can be added to the grease mixture when the latter is passed to a grease kettle, if desired. After the addition of the remainder of the oil, the grease is then cooled to a temperature of about 100 to 150 F. in the grease kettle or any conventional equipment such as the Votator, scraped surface chillers, etc.

The -cooled grease may then be homogenized at high rates of shear in the order of 50,000 to 500,000 reciprocal seconds in such milling or homogenizing devices as a Morehouse mill, Charlotte mill, ink mill, Gaulin homogenizer, etc. The outlet temperature of grease leaving the milling or homogenizing device Will be about 110 to 160 F. Where it is desirable, special additives may be added to the grease prior to homogenization. The

resulting grease composition may then be deaerated in any of the conventional equipment described on pages 278-9 of Boner, supra.

In order to more clearly set forththe invention, reference is now made to the accompanying drawing, Figure I, which is a flow diagram illustrating a method of producing grease compositions of this invention. It is to be understood, however, that modifications as to equipment, its arrangement, type, and kind of materials and their proportions can be resorted to without departing from the concept of this invention.

Referring now to Figure I, the reference numeral 1 designates a rapid soap cooker in the form of a substantially cylindrical closed vessel provided with a vent 9, which may be attached to a vacuum pump. Cooker 1 is connected via lines 10, and 11 and a circulation pump 3 to a heat exchanger 2, which may be supplied "essayer-M 4 with a suitable heating medium such as steam, Dowtherm, direct lire, hot gases, electricity, etc., in any conventional manner. A line 15 provided with a circulating pump 4 connects cooker 1 with blender 17 and other equipment employed in preparing the lubricating grease compositions of this invention.

In operation, cooker 1 is supplied with lubricating oil and hydrated lime via lines 5 and 6, respectively, the charge is mixed thoroughly with stirrer 12, and the soapforming fat or fatty acid material added via line 7. Dry lithium hydroxide is then added via line 8, and the resulting mixture continuously circulated by pump 3 through lines 10, 15 and 11 to heat exchanger 2. Sucient heat is supplied through heat exchanger 2 to raise the temperature of the `f zrease mixture to about 290 to 375 F. A pressure of about 60 to 150 p.s.i.g. is maintained in cooker 1 during this heating step. After saponication is completed in about 10 to 60 minutes, the pressure in the cooker is reduced and vacuum applied to cooker 1 to eiect substantially complete dehydration, the water vapor being removed via line 9. The heated soap-oil concentrate is then Withdrawn through line 15 and fed by means of pump 4 to the high speed mixer or blender 17. Simultaneously, cold lubricating oil is supplied from oil reservoir 16 by pump 21 via line 22 to mixer 17. The diluted soap-oil concentrate is fed to grease kettle 18 via line 25 where it is further diluted with cold lubricating oil from oil reservoir 16 via line 24 to obtain the desired proportions of soap and oil in the finished grease composition. As an alternative method of diluting the soap-oil concentrate, all of the oil desired in the finished grease maybe blended with the soap concentrate in mixer 17 or the mixer may be by-passed with the blending being carried out entirely in grease kettle 18.

Following thorough mixing in grease kettle 18, the grease mixture may be passed via line 27 to a milling or homogenizing device 19 and subjected to high rates of shear. If desired, conventional lubricating grease addiv tives may be supplied to the grease via line 28 or added to the kettle prior to homogenization. The homogenized grease may then be fed to deaerator 20 via line 29 and subsequently packaged.

Figure II represents another processing method by which the grease composition of the invention may be prepared. According to this process a plurality of cookers are employed. Any two or more of these cookers can be used for a given operation, and then most advantageously operated alternately to provide continuous feeding of the soap-oil concentrate to the subsequent blending and finishing steps.

In operation, cookers'40 and 41 are supplied with the soap-oil constituents via lines 43, 44, 45 and 46 as similarly described in the processing method represented by Figure I. Cookers 40 and 41 are closed vessels wherein saponification of the fat or fatty acid material and formation of the soap-oil concentrate can be carried out under the prescribed temperatures and pressures of this invention. As noted above, cookers 40 and 41 are preferably operated alternately, and in actual use while the soap-oil concentrate of one of the cookers is being fed to the other equipment, another soap-oil concentrate is being prepared in the other cooker. If desired, three cookers can be used for simultaneous charging, cooking and discharging. Thus, the overall grease-making system may be operated on a continuous basis.

Both cooker 40 and 41 are connected to heat exchanger 42.V The charge of cooker 41 is circulated through heat exchanger 42 via lines 49, 50 and 70 and pump 51. The charge of cooker 40, on the other hand, is circulated to heat exchanger 42 via lines 48, 52, 50 and 70 and pump 51. It is to be understood, of course, that the preparation and circulation of the soap-oil concentrate is carried out only in one cooker at a time. For example, if the grease-making process is started by charging the oil, saponiable material, lime and dry lithium naomi hydroxide monohydrate to cooker 40, `this batch of soapoilconcentrateis completed prior to charging cooker 41. Following our example, the finished soap-oil concentrate of vcooker I40 is fed to vacuum dehydrator 53 via lines 48 Aand 60. This vacuum dehydrator may be any conventional type of `apparatus suitable for this purpose such as a Cornell homogenizer. V'Instead of a vacuum dehydrator an accumulator tank or stripping tower may similarly be .used to dehydrate the soap-oil'concentrate. While the contents of cooker 40 are being passed to the vacuum dehydrator, the soap-oil concentrate constituents are charged .to cooker .41 and lcirculated through heat exchanger 42, as. described above.

lAlfter the soap-oil concentrate has been substantially dehydrated Ai n dehydrator 53, it--is 'fedto a high `speed mixer or blender-61 via pump v54`and line 5S. Cold lubricating o'il is simultaneously supplied to blender .61 via line 59 and -punip from Aoil reservoir 56. The dilutedsoap-oil concentrate yis then passed through cooler 63 viav line 62. Any v,convention'al.scraped surface cooling or chilling unit maybe employed in this stage. The cooled grease composition may then be fed via line 64 to a milling or homogenizing device 65, wherein it is subjected to high rate of shear. Following homogenization, the grease may be passed through a deaerator 68 via line 67 and then finally packaged.

In accordance with an alternate grease-making method of the invention, the dehydrator may be positioned after mixer or blender 61. As shown in Figure II the soapoil concentrate may be passed directly to mixer 61 via lines 60 and 60. The diluted soap-oil concentrate from mixer 61 is then passed to dehydrator 53' and cooler 63, as set forth above.

The following examples are presented to illustrate the preparation and various characteristics of suitable greases manufactured according to the process of this invention.

1 Saponication No. 197 mg. KOH/gm. Iodine No. 40.

This grease was prepared by charging the hydrated lime and the lithium hydroxide monohydrate in about of the mineral lubricating oil to a rapid soap cooker, as illustrated in Figure I, with continuous stirring to form a slurry. The animal fatty acids were charged to the cooker followed by the addition of a little more oil as a line Wash. The amount of ingredients added to the cooker were such as to produce a soap-oil concentrate (percentages above) containing about 55% of mixed lithium soap and calcium soap in the oil, with a mole ratio of lithium soap to calcium soap of about 4 to l. The resulting mixture was heated in a closed system at a temperature of about 345 F. and at a pressure of `about 120 p.s.i.g. for about 10 minutes, with continuous recycling through a steam heated heat exchanger. pressure in the cooker was then reduced and vacuum applied to the cooker to effect substantially complete dehydration. The total cooking and dehydration t1me was about 30 minutes. The hot soap-oil concentrate (345 F.) was passed to a Lancaster mixer where it was diluted with cold mineral lubricating oil (80 F.) to give a grease having a mixed soap content of about 13.5%. This grease composition was passed through a grease kettle where it was further diluted with the remainder of the lubricating oil to give a mixed soap content of 12.1% and cooled to 117 F. A sample (No. l) ofthe cooled grease was then milled in a Charlotte mill at a cone clearance of 0.027", amilling rate of 181 lbs/hr. and

The

agresser-exit temperature of =F. 4Another sample (No. 2j) of thecooledgrease was milled in a Morehouse mill at a rate of 6,000 lbs./hr. at a stone clearance of 0.003l and a grease outlet temperature of 140 F. Both of these samples were deaerated subsequent to milling.

Inspection of these greases gave the following results:

The above data show that outstanding lubricating grease compositions containing lithium soap and calcium soap thickeners can be effectively prepared by the process of this invention.

The following example is submitted to show that it is not feasible to saponify the fat or fatty acid material with dry lithium hydroxide monohydrate at relatively low temperatures (280 F.) and at atmospheric pressure, i.e. in an open system.

Example II A grease was prepared from the following formulation: Formulation, wt. percent:

Animal fatty acids1 15.00 Lithium hydroxide monohydrate 1.90 Hydrated -lime 0.85

Mineral lubricating oil (70 SUS 210 F.) 82.25 1 Sap. No. 197. Iodine No. 40.

The grease was prepared by intermittently mixing one third of the mineral lubricating oil with the animal vfatty acids, the dry lithium hydroxide monohydrate and the hydrated lime. The resulting mixture was heated in an open grease kettle, i.e. at atmospheric pressure for two hours at 280 F. Subsequent to heating, the remainder 0f the mineral lubricating oil was added to the grease mixture while cooling the latter to F. The grease was then homogenized in a Gaulin homo'genizer at 4,000 p.s.i.g.

The finished grease was smooth, but it had a low dropping point of only about 214 F. and a worked penetration of 400 mm./ 10. On wetting the surface of the grease with alcoholic phenolphthalein, unreacted LiOH could be detected.

As previously noted, the soap-oil concentrate may first be blended with additional lubricating oil and the resulting mixture then subjected to dehydration. A greasemaking process utilizing this method is described in the following example.

Example III Formulation, wt. percent:

Animal fatty acids 12.00 Lithium hydroxide monohydrate 1.46 Hydrated lime 0.67 Lubricating oil 70 SUS 210 F 85.87

'I'he soap-oil concentrate was prepared as in Example I, up to the point at which the pressure was reduced. In this example, the wet concentrate at 345 F. was metered to a Lancaster disperser at a rate of 22.2 lb./min. and blended with oil to give the above composition plus about 1.75% water of reaction, etc. This water was then removed by passing the wet grease, at a temperature of 256 F., through a Cornell homogenizer at a vacuum of 21" of mercury, reducing the water content to 0.2% by Weight and the temperature to 207 F. The grease was v then cooled to 135 F. in a scraped Vsurface coolerLaud milled in a Charlotte colloid mill at 0.015 clearance.

The iinished grease from this operation was packaged for use.

The finished grease had the following inspections:

Unworked penetration 280 mm./ 10. Worked penetration 283 mm./ 10. Free alkali (as NaOH) 0.18%.

Wheel bearing test (1 hr., 220 F., 660

r.p.m., tilted 15):

Leakage, grams 0.6. Rating Excellent. Texture Smooth,vunctious.

V It will be further understood that the invention is not necessarily limited to the specific materials and operating conditions of the foregoing examples,vr These materials and conditions may be varied within the limits indicated in the general portions of the specicatio'n.

What is claimed is:

A process for preparing a concentrate comprising References Cited in the tile of this patent UNITED STATES PATENTS 2,389,523 Leyda Y V No'v. 2o, 194s 2,444,720 Bell July-'6,1948

2,641,577 OHalloran 7.---June 9, 1 953 p OTHER REFERENCES The Manufacture and Application of yLubricatingl Greases, Boner, Reinhold Pub. Corp. (N.Y.), 1954, pp. 171, 206, and 448. Y

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