US3242082A - Method of grease manufacture - Google Patents

Description

March 2 9 F. BADGETT ETAL 3,242,082

METHOD OF GREASE MANUFACTURE 2 Sheets-Sheet 1 Filed May 22, 1963 Air mm a

L. F. BADGETT ETAL 3,42,U82

METHOD OF GREASE MANUFACTURE March 22, 1966 2 Sheets-Sheet 2 Filed May 22, 1963 Q2 w m/ 9 cow United States Patent 3,242,082 METHOD 0!? GREASE MANUFACTURE Lloyd F. Badgett, Port Arthur, William R. Hencke,

Groves, and Fred T. Crookshank, Port Arthur, Tex.,

assignors to Texaco Inc, New York, N.Y., a corporation of Delaware Filed May 22, 1963, Ser. No. 282,330 7 Claims. (Cl. 25234) This invention relates to improvements in grease manufacture and more particularly to an improved low temperature method for the preparation of soap thickened greases.

The so-called low temperature methods of grease manufacture comprise saponifying a saponifiable fatty acid material with a metal base in the presence of a portion of the lubricating oil employed in the grease, heating the grease mixture at a higher temperature below the melting point of the soap for dehydration and soap conditioning periods, and then cooling with the addition of the re mainder of the lubricating oil employed in the grease. These methods have very important advantages in convenience and economy over the soap melt processes wherein a mixture of lubricating oil and soap is heated at a high temperature above the melting point of the soap and the mixture then cooled by various means, ordinarily at a rapid rate. However, the low temperature methods have the disadvantages of generally producing much lower yields than the soap melt processes and of requiring very long manufacturing times, due both to the long heating times required to obtain satisfactory yields and product quality and to the long cooling times necessitated by the inability of the grease mixture to accept at a rapid rate the additional oil which is added during the cooling. The present invention provides an improved low temperature process for the preparation of soap thickened greases, wherein very large reductions in manufacturing times as well as improved yields and other advantages are obtained. We obtain these advantages by employing a method which comprises essentially continuously recirculating a minor stream of grease mixture through a recycle line from a maintained relatively dilute body thereof in the heating and cooling steps and introducing the oil added during the cooling into the circulating stream of grease mixture, the combined stream of grease mixture and added oil being subjected to turbulent mixing before it is introduced into the maintained body of grease mixture. Shearing of the recirculating stream of grease mixture may be employed during the oil addition, and during other steps of the process if desired, very suitably by means of a shear valve located in the recycle line after the point of oil injection.

Grease mixtures prepared in the above manner contain relatively long soap fibers Which are present in the form of a well-dispersed or loosely agglomerated fiber m-at prior to the cooling step, as shown by electron micrographs, very differently from the strongly agglomerated soap fibers obtained by the conventional low temperature methods. The method of adding the additional oil at a lower temperature to a recycle stream of the grease mixture during the cooling step has the efiect of partially warming the additional oil and mixing it with soap fibers before it is introduced into the body of grease mixture. The grease mixtures obtained by the method involving recirculation during the development of the soap fibers are particularly adapted to receive the additional oil added in this manner at a very rapid rate because of the dispersed or loosely agglomerated condition of the soap fibers. However, this method of adding the additional oil during cooling may be employed very advantageously with grease mixtures obtained by other means also, including the conventional 3,242,082 P e t d Ma 2 1 19.55

low temperature methods and soap melt methods. In the case of grease mixtures prepared by such other methods, it is usually necessary to employ shearing of the recirculating stream after the oil addition thereto in order to carry out the oil addition at a substantially increased rate.

The preferred embodiment of this invention comprises carrying out the preparation of the grease mixture with a kettle charge containing only a relatively small amount of lubricating oil and adding preheated oil to the grease mixture following the saponification and substantial dehydration as a means of obtaining greatly shortened saponification and dehydration times and of heating the grease mixture rapidly to the top temperature. The amount of oil which is added in this manner is suflicient to give a grease mixture before the cooling step and preferably during at least a substantial portion of the heating step comprising oil and soap in a ratio of at least 1:1, repectively, and most suitably at least about 4:1, respectively, with greases such as calcium and lithium hydroxy fatty acid soap thickened greases which are difiicult to prepare in satisfactorily smooth form. The preheated oil is very advantageously introduced into the recirculating stream of grease mixture in the same manner as the introduction of oil added during the cooling step.

When operating under our preferred conditions as described herein, grease preparations are carried out with reductions in the manufacturing time as high as 80 percent or more of the time required by the conventional low temperature procedures, as Well as with improved yields and other advantages. The procedure thus offers a means of obtaining greatly increased grease production with ordinary grease making equipment by relatively low equipment investments in pumps, heat exchangers and piping. A special advantage of this invention lies in the fact that it provides an answer to the long standing demand in the industry for a low temperature method of grease manufacture which can be carried out in a single eight-hour work shift.

FIG. 1 is a diagrammatic illustration of one form of apparatus suitable for making greases in accordance with this invention.

FIG. 2 is a graphic representation of the manufacturing time required for a 10,000 pound batch of a calcium 12-hydroxystearate grease both by conventional plant manufacture and by the method of this invention.

Referring in more detail to FIG. 1, numeral 1 represents a jacketed grease kettle equipped with stirrer 2 and adapted to be heated to an elevated temperature above about 350 F. In carrying out the grease preparation, the grease kettle is charged with saponifiable material, lubricating oil, in .an amount equal to about 0.25 to about 10 times the weight of the saponifiable material, and metal base in approximately the stoichiometric amount required to react with the saponifiable material. Ordinarily water is also added to the charge in an amount equal to about 0.5 to about 10 times the weight of the metal base. In some cases, where water is required to obtain a complete reaction, it is found that a reduction in the manufacturing time required may be obtained by employing a waterfree kettle charge and blowing the reaction mixture with steam at a temperature above about 200 F. until the saponification issubst'antially complete. The kettle contents are heated with stirring until saponification and dehydration are substantially complete, as shown by the cessation of foaming, and then heated further to a higher temperature to complete the dehydration and to condition the soap.

The maximum temperature to which the grease mixture is heated is ordinarily in the range from just below the melting point of the soap to about F. below the melting point of the soap. In some cases, it may be heated at or even slightly above the melting point of the soap for a period which is insuificient to obtain complete melting of the soap. The heating cycle in the grease preparation ordinarily includes a period of at least about 15 minutes within the top temperature range, ordinarily from about 15 minutes to about 1 hour. Longer heating periods within the top temperature range may be einployed although they are generally not necessary with grease preparations carried out by the method of our invention.

During the heating cycle and preferably before the grease mixture has been heated to the maximum temperature, recirculation of the grease mixture around the kettle is begun by turning valves 6 and 8 to the open position and starting pump 12. The grease mixture passes through line 5, containing valve 6, line 10 containing valve 8, pump 12, and line 14 containing pressure gauge 15 and shear valve 19. Lines 5, 10 and 14 may be jacketed or otherwise provided with means for applying additional-heating and cooling to the recirculating stream of grease mixture. The shear valve is suitably a gate valve, which is preferably in the wide open position at least until dehydration of the grease mixture is substantially complete. Valve 19 is located a sufiicient distance from kettle 1 to avoid spraying into the kettle when it is operated under a back pressure, suitably a distance equal to at least about 12 times the diameter of pipe 14. As indicated in FIG. 1, the recycle stream of grease mixture is preferably returned at the top of the grease kettle, or at least at a point above the surface of the body of grease mixture within the kettle. This has the advantage of greatly increasing the rate of water evaporation in the dehydration step, thereby very materially shortening the dehydration step, particularly where a relatively large amount of water is employed in the saponification.

Circulation of the grease mixture through the recycle system during the heating cycle following the saponification step is carried out at a rate sufficient to give one batch turnover within about 22 minutes, such as in about 0.3-22 minutes, and preferably in about 0.4-15 minutes, based on the weight of the grease mixture during the heating cycle, or in about 0.2515 minutes, and preferably 0.3-12 minutes, based upon the average weight of grease mixture during the heating cycle when the process is carried out with additional oil added during the heating step as described hereinbelow. Recycling during the cooling cycle is suitably carried out at a rate sufficient to provide a batch turnover in about 0.535 minutes, preferably in about 1-20 minutes, based on the Weight of the finished grease, or in about 0.4-27 minutes, and preferably about -17 minutes, based on the average Weight of grease mixture during the cooling cycle. In general, faster recycling rates in the heating step result in smoother products and increased yields, particularly in the case of lithium and calcium hydroxy fatty acid soap thickened greases. When recycling is employed during the saponification and dehydration steps upon a charge containing only a minor amount of the lubricating oil employed in the grease, recycling rates resulting in a batch turnover in about 0.1-15 minutes, and preferably in about 0.25- minutes, may be employed.

Very advantageously, the recycling is carried out for a minimum period of about minutes,and preferably for at least about 30 minutes during the heating step following the saponification, until at least 5 batch turnovers and preferably at least 10 batch turnovers, based on the average weight of the grease mixture during thisperiod, are obtained. It is preferably carried out continuously following the saponification and substantial dehydration throughout the heating cycle.

Cooling of the grease mixture is carried out by cutting off the heat to the grease kettle, and to the recycle lines if such additional heating is employed, and introducing lubricating oil from tank into the recirculating stream of grease mixture. The added oil is at a temperature substantially below that of the grease mixture, such as at least about F., and preferably at least about F., below the temperature of the grease mixture at the beginning of the cooling step. The lubricating oil passes from tank 20 into line 36 by way of line 22 containing valve 23, pump 24, line 25 and line 26 containing valve 27, dial thermometer 33, pressure gauge 34 and valve 35. Valve 35 is preferably a one way valve, most suitably of a type designed to prevent gravity flow of oil through pump 24 when the pump is not operating, such as a diaphragm controlled reducing valve or a spring loaded check valve. In line 36, the oil may pass into the recirculating stream of grease mixture at the intake of pump 12 by passing through valve 37 into line 10, or into the grease mixture at the discharge side of pump 12 by passing through valve 38 into line 14. It is preferably passed into the grease mixture at the intake side of pump 12 in order to obtain increased mixing and shearing by the action of the pump, particularly when valve 19 is in the wide open position. The oil may be introduced into the recirculating stream of grease mixture at a rate such that the ratio of the rate fo flow of the grease mixture before the point of confluence to the rate of oil injection is from about 1:1 to about 400: 1, preferably in a ratio from about 2:1 to about 150:1, and most advantageously in a ratio from about 3:1 to about 50:1, by weight, respectively. During the oil injection, valve 19 may be in the wide open position or in a partly closed position, such as to give a pressure drop across the valve of about 10200 pounds per square inch. It is usually preferable to carry out the oil injection With valve 19 in a partly closed posit-ion resulting in a pressure drop of about 25-125 pounds per square inch.

The oil addition is preferably commenced at the beginning of the cooling step, and may be carried out Over the entire cooling period or through only a portion thereof. Additional cooling may be, applied to the kettle, and also to the recirculating stream of grease mixture. The amount of lubricating oil added during the cooling may amount to from about 10 to as high as about 95 percent of the total oil contained in the grease. It will usually be from about 25 to about 75 percent of the total oil contained in the grease. When the oil addition is carried out during only a portion of the cooling step, it is advantageous in some cases to continue recirculation of the grease mixture with shearing down to the drawing temperature. Any additives employed in the grease are ordinarily added during the cooling step when the grease mixture is at a suitably low temperature, generally at below about 250 F. The cooled grease mixture is finally drawn through line 40 containing valve 41.

The grease mixture before the cooling step preferably comprises oil and soap in a weight ratio above 1:1, respectively. With greases of the type which are difiicult to prepare in satisfactorily smooth form, such as lithium and calcium hydroxy fatty acid soap thickened greases, the mixture preferably comprising oil and soap in a weight ratio of at least about 421, respectively, andmost advantageously at least about 5 :-1, respectively. Theprocedure which is regarded as the particularly preferred embodiment of this invention comprises employing only a relatively small amount of lubricating oil in the saponification mixture, and adding the remainder of the lubricating oil required to give the desired oil-soap ratio at at higher temperature than the grease mixture during the: heating step, preferably following substantial dehydra-- tion of the grease mixture. The preheated oil is very' advantageously introduced into the recycle line of the: grease mixture in the same manner as the oil added. during cooling. tank 20 to heater 3!? by way of line 22, pump 24, line; 25 and line 23 containing valve 29. Heater 30 may be anysuitable type of heater such as a coil heater as indicatcd in the diagram. From heater 30 the oil passes. into line 26 and is introduced into the circulating stream In this procedure, the oil passes fromof grease mixture at either the intake or the discharge side of pump 12 as described hereinabove in connection with the introduction of the oil during cooling. It is introduced at the discharge side of pump 12 when light oils are employed which may cause vapor locking in the pump. The temperature of the oil added in this manner is preferably substantially higher than that of the grease mixture, and may be up to or even slightly higher than the melting point of the soap. The rate at which the oil is introduced may suitably be such that the ratio of the rate of recirculation of the grease mixture to the rate of oil injection is within the ranges disclosed hereinabove in connection with the introduction of cold oil during the cooling cycle. The amount of oil added in this manner may be from about 5 percent up to about 70 percent of. the total oil employed in the grease. In the preparation of lithium hydroxy fatty acid soap thickened greases it is preferably not above about 50 percent and most suitably from about to about 30 percent of the total oil employed in the grease. A portion of this oil may be added through the kettle top, it necessary, to obtain a grease mixture which is sufficiently fluid to circulate:

Shearing of the recirculating stream of grease mixture may be carried out during the addition of the preheated oil by setting valve 19 so as to obtain a pressure drop of about 10-200 pounds per square inch across the valve. Shearing of the grease mixture in this manner may also be carried out very advantageously in some cases during other stages of the heating cycle also, particularly during the heating at top temperature.v

Greases of the types which are ordinarily finished by milling may be milled in the usual manner, such as by means of a colloid mill set at a narrow clearance. However, the milling step may generally be obviated by shearing during the grease preparation by means of a shear valve in the recycle line as described above. The manner is which this shearing is applied for optimum results, including both the severtity and duration of the shearing and the stage in the grease making process wherein it is employed, varies considerably according to the type of grease being produced, depending principally upon the character of the soap thickener.

The metal base employed in the saponification may be a hydroxide or other suitable compound of any of the metals ordinarily employed as the metal component of the soap in the preparation of lubricating greases, such as sodium, lithium, potassium, calcium, barium, magnesium, zinc, cobalt, manganese, aluminum, lead, etc., as well as mixtures of two or more metals. It is preferably a metal oxide, hydroxide. or carbonate. The greases which are most advantageously prepared by the method of this invention are those wherein the soap thickener is an alkali metal or alkaline earth metal soap, or a mixture of two or more soaps of these classes.

Suitable saponifiable materials for use in these grease preparations comprise higher fatty acids containing from about 12 to 32 carbon. atoms per molecule and hydroxy substituted higher fatty acids, their glycerides and other esters and mixtures thereof. The invention also contemplates grease preparations carried out in the manner described above wherein such higher fatty acid materials are employed in conjunction with lower fatty acid materials, such as fatty actids containing from one to about 6 carbon atoms per molecule, their glyceries and other esters. Such lower fatty acid materials may be employed in amounts giving a mol ratio of lower fatty acid to higher fatty acid from below 1:1 up to about 20:1, respectively. Also, intermediate fatty acid materials may be employed in conjunction with the higher fatty acid materials in varying amounts, ordinarily in amounts giving a mol ratio with the higher fatty acid material below about 1:1, respectively.

The oleaginous liquids employed in these greases may be any suitable oils of lubricating characteristics, includture up to 260 F. in 10 minutes.

utes, and maintained at 280-286 F. for hour.

ing the conventional mineral lubricating oils, synthetic oils obtained by various refining processes such as cracking and polymerization and other synthetic oleaginous compounds such as high molecular weight ethers and esters. The dicarboxylic acid esters, such as di-2ethylhexyl sebacate, di(secondary amyl)sebacate, di-Z-ethylhexyl azelate, di-iso-octyl adipate, etc., comprise a particularly suitable class of synthetic oils and may be employed either as the sole oleaginous component of the grease or in combination with other synthetic oils or mineral oils. The oil employed in the saponification mixture is preferably one which is substantially inert under the saponifica tion conditions, most suitably a mineral lubricating oil. Suitable mineral oils for use in these greases are those having viscosities in the range from about to about 2000 seconds Saybolt Universal at 100 F., which may be blends of lower and higher viscosity oils. They may be either naphthenic or parafiinic in type, or blends of two or more oils of these different types.

The following examples are illustrative of lubricating grease preparations carried out in accordance with this invention.

Example I A calcium 12-hydroxystearate thickened grease was prepared by the method of this invention as: described below.

The following materials were employed in the grease preparation: The lubricating oil employed was a naphthenic distillate oil having a Saybolt Universal viscosity at 100 F. of 58 seconds. The saponifiable material employed was a commercial l2-hydroxystearic acid having a saponification number of 187, an acid number of 173 and an iodine number of 5.

The equipment employed in the grease preparation was a 150 pound capacity jacketed steam heated laboratory kettle with auxiliary equipment for grease circulation and hot and cold oil injection as shown in FIG. 1. The grease circulation equipment consisted of 1% inch pipe connecting the kettle draw-off with a No. 2 Globe Rota Piston pump having a capacity of approximately 17 gallons per minute, and a inch pipe extending from the pump to the top of the kettle and containing a shear valve. The pipes were insulated and steam traced. The oil injection system comprised a 100 pound charge tank, a controlled volume pump having a capacity of approximately 25 gallons per hour and a Graham Heliflow Exchanger for heating the oil.

Following is a detailed description of the method employed in the grease preparation: The grease kettle was charged with 33.9 pounds of lubricating oil, 11.30 pounds of IZ-hydroxystearic acid and 1.72 pounds of lime. Stirring and jacket heating of the kettle contents were begun. At the same time recirculation of the kettle contents through the recycle line was begun at a rate of 17 gallons per minute, with the shear valve in the wide open position. After 15 minutes, when the temperature of the mixture had reached 220 R, an additional 27.6

pounds of lubricating oil preheated to 290 F. were injected into the recycle stream at the intake side of the pump at a rate of pounds per hour with continued kettle heating, which brought the temperature of the mix- The kettle contents were further heated to 280 F. in an additional 20 min- The heat was then cut off and 26.8 pounds of lubricating oil at 78 F. were injected into the recycle stream at a rate of pounds per hour, which resulted in cooling the grease mixture to 236 F. in about 15 minutes. Stirring and recirculation of the grease mixture were continued while the grease mixture was further cooled to the drawolf temperature of F.

The total time required for the above preparation was 2 hours, as compared with 15.75 hours required for a laboratory preparation of the same size carried out by the conventional low temperature method employed in plant manufacture. The greases obtained by the two methods stirring for one half hour. cycle line was then discontinued and 48 pounds of the distillate oil at 100 F. were introduced into the recirculating stream of grease mixture at the intake side of '7 were generally equivalent in appearance and lubricating properties. The following tabulation shows analyses and tests obtained upon these greases.

The time required for preparing a 10,000 pound plant batch of the above grease by the recirculation-oil injection procedure described above is about 4.2 hours, calculated from the laboratory preparation on the basis of heat transfer data obtained on an oil heated plant kettle. On the same basis, the time required for a 10,000 pound batch in the same kettle by the conventional procedure is about 24.1 hours. A comparison of the times required for the separate steps of the grease making process by the above method and by the conventional procedure is shown dia grammatically in FIGURE 2.

Example II A lithium 12-hydroxystearate thickened grease was prepared by the method of this invention as described below.

The -following materia'ls were employed in this preparationi The. lubricating oil employed was a blend in about a 7:5.3 ratioby weight, respectively, of a refined Manvel residuum having a Saybolt Universal viscosity at 210 F. of about 107 seconds and a refined parafiinic distillate "oil having a Saybolt Universal viscosity at 100 F. of about 180 seconds. The saponifiable material employed was a commercial methyl 12-hydro'xystearate, having a saponification number of 178, a neutralization number of and an iodine number of 3.

The equipment employed in this preparation was the same as that employedin the grease preparation described in Example I.

Following is a detailed description of the method employed in the grease preparationrThe grease kettle was charged with 1.41 pounds of lithium hydroxide monohydrate, 4.2 pounds of water, 8 pounds of the Manvel residuum and 8.6 pounds of methyl 12-hydroxystearate.

Stirring and jacket heating of the kettle-contents were begun. Whenthe mixture was heated to 140- R, which required about 8 minutes, recirculationof the mixture through the recycle line was begun at a rate of 17 gallons per, minute with the shear valve inwide open position. At the same time, introduction of an additional 55.5

pounds of the Manvel residuum preheated to 290 F.

was begun. The preheated oil was introduced into the recycle stream .at the intake side of the pump at a rate :of 60 pounds per hour during heating of the grease .mixture to 305 9 F. The grease mixture was then further heated to' about 338 F., the time from the beginning of recirculation to the top temperature being 1.5 hours. The grease mixture was maintained at a temperature in the range 335340 F. with continued recirculation and Heating of the kettle and rethe pump at a rate of 60 pounds per hour, which resulted in cooling the grease mixture to 200 F. in 45 minutes. The grease was finished by milling with one pass through a Premier Colloid Mill set at 0.003 inch clearance.

The product obtained as described above was a smooth grease of good appearance and lubricating properties,

x 8 having an ASTM penetration-at,77 F. of 317, unworked,

and 327, worked, for a 6.9 percent lithium-12-'hydroxy stearate content.

The total manufacturing time, aside from the milling step, for the above preparation was 2 hours and 50 minutes. This represents a very large saving in manufacturing time over the times required by the prior art methods for the preparation of lithium hydroxy fatty acid soap thickened greases, including that of W. R. Hen'cke et al. described in US. 3,015,624. In addition, applicants process provides yields which are at least equivalent and generally superior to thoseobtain'ed by the Hencke et a1. process, being greatly superior to those obtained by the older prior art processes.

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.

We claim:

1. In a low temperature process for preparing a soap thickened grease which comprises providing a hot grease mixture comprising a portion of the lubricating oil contained in the finished grease and soap dispersed therein, said grease mixture having been heated to a temperature in the range from just below the melting point of the soap to about F.'below the melting point of the soap, and thereafter cooling the said grease mixture with the addition of the remainder of the lubricating oil contained in the finished grease at a substantially lower temperature than the grease mixture, the improvement which comprises introducing the lubricating oil added during the cooling into a minor recirculated stream of the grease mixture which is continuously withdrawn from a maintained body of the great mixture and subjecting the combined stream of grease mixture and added lubricating oil to turbulent mixing before returning the said combined stream tothe said maintained body of grease mixture, the ratio of the rate of circulation of the grease mixture and the rate of introducing the said lubricating oil being from about 1:1 to about 400: 1, respectively., by Weight.

2. The process of claim 1 wherein the said combined stream ofgrease mixture and lubricating oil is passed through a shear valve with a pressure drop across the said valve of about 10-200 pounds per square inch.

3. The process of claim 2 wherein the pressure drop across the said valve is about 25 -125 pounds per square inch. 1

4. The process of claim 1 wherein the said grease mixture before cooling comprises lubricating oil and soap in 'a ratio o f at least :1 respectively, by weight.

p 5. The process of claim 1 wherein the said grease mix ture is recirculated at a rate such that the weight of recirculated grease mixture equals the total average weight of grease mixture in the cooling cycle in about 0.4 27 minutes. t l

6. The process of claim 1 wherein the said soap is chosen from the class consisting of alkali metal and alkaline earth metal soaps of higher fatty acids and hydroxy fatty acids, and mixtures thereof.

7. The process of claim 1 wherein the said grease is finished by milling.

Claims (2)

1. IN A LOW TEMPERATURE PROCESS FOR PREPARING A SOAP THICKENED GREASE WHICH COMPRISES PROVIDING A HOT GREASE MIXTURE COMPRISING A PORTION OF THE LUBRICATING OIL CONTAINED IN THE FINISHED GREASE AND SOAP DISPERSED THEREIN, SAID GREASE MIXTURE HAVING BEEN HEATED TO A TEMPERATURE IN THE RANGE FROM JUST BELOW THE MELTING POINT OF THE SOAP TO ABOUT 75*F. BELOW THE MELTING POINT OF THE SOAP, AND THEREAFTER COOLING THE SAID GREASE MIXTURE WITH THE ADDITION OF THE REMAINDER OF THE LUBRICATING OIL CONTAINED IN THE FINISHED GREASE AT A SUBSTANTIALLY LOWER TEMPERATURE THAN THE GREASE MIXTURE, THE IMPROVEMENT WHCIH COMPRISES INTRODUCING THE LUBRICATING OIL ADDED DURING THE COOLING INTO A MINOR RECIRCULATED STREAM OF THE GREASE MIXTURE WHICH IS CONTINUOUSLY WITHDRAWN FROM A MAINTAINED BODY OF THE GREAT MIXTURE AND SUBJECTING THE COMBINED STREAM OF GREASE MIXTURE AND ADDED LUBRICATING OIL TO TURBULENT MIXING BEFORE RETURNING THE SAID COMBINED STREAM TO THE SAID MAINTAINED BODY OF GREASE MIXTURE, THE RATIO OF THE RATE OF CIRCULATION OF THE GREASE MIXTURE AND THE RATE OF INTRODUCING THE SAID LUBRICATING OIL BEING FROM ABOUT 1:1 TO ABOUT 400:1, RESPECTIVELY, BY WEIGHT.

6. THE PROCESS OF CLAIM 1 WHEREIN THE SAID SOAP IS CHOSEN FROM THE CLASS CONSISTING OF ALKALI METAL AND ALKALINE EARTH METAL SOAPS OF HIGHER FATTY ACIDS AND HYDROXY FATTY ACIDS, AND MIXTURES THEREOF.

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