US3242084A - Method of grease manufacture - Google Patents

Description

March 22, 1966 G. s. BRIGHT ETAL 3,242,084

I METHOD OF GREASE MANUFACTURE Filed May 22, 1965 Wm w United States Patent 3,242,084 METHOD OF GREASE MANUFACTURE Gordon S. Bright, Port Arthur, and William R. Green, in, Groves, Tex., assignors to Texaco lino, New York, N.Y., a corporation of Delaware Filed May 22, 1963, Ser. No. 282,341 Claims. (Cl. 252-39) This invention relates to an improved method for the manufacture of calcium hydroxy fatty acid soap thickened greases of the so-called rheopectic type, which undergo a large amount of hardening upon moderate shearing of the type to which they are subjected in automotive bearings in service.

In accordance with this invention, low soap content calcium hydroxy fatty acid soap thickened greases of the rheopectic type are prepared by a low temperature method carried out with recirculation of the grease mixture through a recycle line on the grease making zone during the heating up to a maximum temperature below the melting point of the soap, and optionally during the cooling step also. By carrying out the process under the preferred conditions, which comprise forming a relatively dilute soap slurry and recirculating continuously during at least that portion of the heating cycle wherein the major amount of fiber development takes place, with substantially no additional shearing of the grease mixture, fluid greases containing as high as about percent, and ordinarily about 2-12 percent by weight of calcium hydroxy fatty soaps are obtained which thicken to N.L.G.I. No. 0-2 grade consistencies upon moderate shearing.

Calcium hydroxy fatty acid soap thickened greases prepared in theabove manner contain long well shaped soap fibers in a highly agglomerated condition, accounting for the low viscosity of the product. While we l do not wish to be limited by any theory, it is thought that the effect of the conditions of our process in producing the grease consistency characteristics required for a rheopectic grease is due to the increased tendency of the longer fibers thus produced to form agglomerates, together with the reduced amount of energy input required to redisperse the fibers in these agglomerates due to their smooth fiber form. The affect moderate shearing of these greases in producing a large change in conistency is in marked constrast to the effect of such shearing upon calcium hydroxy fatty acid soap thickened greases obtained by low temperature methods of the prior art, whereby little or no change in consistency is ordinarily obtained by only moderate shearing.

In accordance with the preferred embodiment of our invention, the grease mixture is recirculated continuously during both the heating and cooling cycles and additional oil at a lower temperature is introduced into the recycle stream during the cooling process, as described by L. F. Badgett, W. R. Hencke and F. T. Crookshank in their copending application Serial No. 282,330, filed of even date herewith. The process is also carried out very advantageously by introducing additional oil at a higher temperature than the grease mixture into the recycle stream during heating to the maximum temperature, as also described in the said application of Badgett et al.

The grease making process of our invention is preferably carried out with no shearing of the grease mixture obtained by the saponification step aside from that necessarily obtained by the recycling operation and the effect of the stirrer. However, shearing during the saponifioation may be employed very advantageously in some cases, suitably by means of a shear valve in the recycle line operated at a pressure drop of about -200 pounds per square inch, preferably at about -125 pounds per Patented Mar. 22, 1966 square inch, where difiiculty is experienced in obtaining a smooth product.

The figure is a diagrammatic illustration of one form of apparatus suitable for making greases in accordance With the preferred embodiment of this invention.

Referring in more detail to the figure, numeral 1 represents a jacketed grease kettle equipped with stirrer 2 and adapted to be heated to elevated temperatures above about 350 F. In carrying out the grease preparation, the grease kettle is charged with saponifiable material, lubricating oil, and a calcium metal base, such as calcium oxide, calcium hydroxide or calcium carbonate, in approximately the stoichiometric amount required to react with the saponifiable material. Water may be added to the charge also, suitably in an amount equal to from about 0.5 to about five times the weight of the metal base, although the presence of water is not required. The lubricating oil and saponifiable material are employed in a Weight ratio of at least about 2:1, respectively, and preferably at least about 3:1, respectively. They are most suitably employed in a weight ratio from about 3:1 to about 5:1, respectively.

The kettle contents are heated with stirring up to the maximum temperature employed, which ordinarily requires about 1-5 hours, including a holding period which is preferably employed in the maxim-um temperature range for at least about 15 minutes.

Recirculation of the grease mixture through the recycle line is carried out during the heating at least up to about 240 F. and is begun at least as soon as dehydration is substantially complete. It is preferably begun at least as soon as the saponification is substantially complete. Recirculation of the grease mixture 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, which is suitably a gate valve. Valve 19 is located a suffioient distance from kettle 1 to avoid spraying of the grease mixture into the kettle when the valve is operated under a back pressure, suitably a distance equal to at least about 12 times the diameter of pipe 14. 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. Pump 12 is preferably of a type wherein the fluid being pumped is subjected to only a relatively small amount of sheaning. It is suitably a positive displacement rotary type pump wherein the grease mixture is sheared at a rate below about 10,000 reciprocal seconds and preferably at a rate below about 5,000 reciprocal seconds.

In carrying out the process by the preferred embodiment of this invention, the grease mixture: is circulated continuously during the saponification and during the remainder of the heating cycle and the cooling cycle also, with valve 19 in the wide open position following the saponification step. During the saponification step, valve 19 may be in a partly closed position so as to give a pressure drop of about 20-200 pounds per square inch, and very suitably in about the range 25-125 pounds per square inch across the valve. Shearing of the recycled stream may be continued in this manner for a short period following the saponification step, preferably for a period not in excess of about 15 minutes and before the grease mixture has been heated above about 240 F. Such a procedure is useful in some cases in. the preparation of greases which are particularly difficult to prepare in satisfactorily smooth form. However, it is not ordinarily necessary or desirable, and our preferred procedure involves no substantial shearing of the grease mixture following the saponification step.

Circulation of the grease mixture through the recycle system during the heating cycle following the saponification step is carried out at a rate sufiicient to give one batch turnover within about 22 minutes, such as in about 03-22 minutes, and preferably in about 04-15 minutes, based on the weight of the grease mixture during the heating cycle, or in about 0.25-10 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, and preferably in about l20 minutes, base on the weight of the finished grease, or in about 0.427 minutes, and preferably about 05-17 minutes, based on the average weight of grease mixture during the cooling cycle.

Very advantageously, the recycling is carried out for a minimum period of about 15 minutes, and preferably for at least about 30 minutes during the heating cycle following the saponification, until at least 5 batch turnovers and preferably at least batch turnovers, based on the average weight of the grease mixture during this period, are obtained.

The maximum temperature to which the grease mixture is heated is ordinarily in the range from about 250 F. to just below the melting point of the soap. In the preparation of calcium 12-hydroxystearate thickened greases employing paratfinic lubricating oils, the grease mixture is preferably heated to a top temperature in the range from about 260 F. to about 275 F. The grease mixture is usually heated within this temperature range for a time from about 15 minutes to about 2 hours. However, in some cases the process may be carried out with no holding period in the high temperature range.

Cooling of the grease mixture is carried out by cutting off the heat to the kettle, and to the recycle line 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 100 F., and preferably at least about 150 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 by the action of the pump. The oil may be introduced into the recirculating stream of grease mixture at a rate such that the ratio of the rate of flow of the grease mixture before the point of confluence to the rate of oil addition 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 1, by weight, respectively.

The oil addition is preferably commenced at the beginning of the cooling step and may be carried out over the entire cooling period or during 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 90 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. Any additives employed in the 4. grease may be added during the cooling step, preferably when the grease mixture has been cooled to about 250 F. or lower. The cooled grease mixture is finally drawn through line 40 containing valve 41.

In the grease preparation carried out by the method comprising a particularly preferred embodiment of this invention, the saponification is carried out in the presence of lubricating oil in a ratio from about 2:1 to about 4:1, respectively, with the saponifiable material, and preheated oil is introduced into the recirculating stream of grease mixture during the heating step, preferably beginning when the grease mixture is at a temperature in about the range 220-250 F. in .an amount suflicient to give an oil-soap ratio of at least about 5:1 and preferably from about 7:1 to about 12:1, respectively. The added oil is preferably preheated to a temperature substantially above the temperature of the grease mixture as a means of rapidly bringing the grease mixture up to the top temperature. The preheated oil is introduced into the recycle line by passing from tank 20 to heater 30 by way of line 22, pump 24, line 25 and line 28 containing valve 29. Heater 30 may be any suitable type of heater, such as a coil heater as indicated in the diagram. From heater 30 the oil passes into line 26 and is introduced into the circulating stream of 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. 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 in some cases. The rate at which this 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 up to about 70 percent of the total oil employed in the grease. It is ordinarily from about 20 to about percent of the total oil contained in the finished grease.

Suitable soap forming hydroxy fatty acid materials which may be employed in the production of these greases are essentially saturated hydroxy fatty acids containing 12 or more carbon atoms and one or more hydroxyl groups separated from the carboxyl group by at least one carbon atom, the glycerides and lower alkyl esters of such acids. Preferably, the acid contains about 16 to about 22 carbon atoms per molecule. Such materials may be obtained from naturally occurring glycerides or produced synthetically by methods such as the 'hydroxylation of fatty acids or the hydrogenation of ricinoleic acid or castor oil. Particularly suitable materials of this character are l2-hydroxystearic acid, the methyl ester thereof, and hydrogenated castor oil.

The lubricating oils employed in these greases include particularly the conventional mineral lubricating oils, having Saybolt Universal viscosities in the range from about seconds at 100 F. to about 225 seconds at 210 F., and synthetic hydrocarbon oils having viscosities in this range, such as those obtained by cracking and po lymerizing products of the Fiseher-Tropsch process and the like. The mineral lubricating oils may be either naphthcnic or paraffinic oils, or blends of different oils of these types. Other synthetic oleaginous compounds such as polyesters, polyethers, etc. having viscosities within the lubricating oil viscosity range may also be employed in these greases as at least part of the lubricating oil component. Suitable compounds of this type include particularly the aliphatic dicarboxylic acid diesters, such as, for example, di-Z-ethylhexyl sebacate, di(secondary amyl) sebacate, di-2-ethylhexyl azelate, di-iso-octyl adipate, etc. However, a lubricating oil which is substantially unreactive under the saponification conditions is preferably employed in the saponification mixture, mineral lubricating oils being particularly suitable for this purpose,

Various additives of the usual types, such as corrosion inhibitor-s, oxidation inhibitors, extreme pressure agents, antiwear agents, etc., may be employed in these greases. Suitable oxidation inhibitors include particularly those of the amine type, such as diphenylamine, phen'ylalpht'u napthylamine, tetramethyl diaminodiphenyl methane, etc. Very advantageously, the greases may contain from about 3 to 12 percent by weight of a sulfurized fatty oil, such as sulfurized sperm oil, containing about 5-15 percent by weight of sulfur, and about 1 to 3 percent by weight of a lead soap, such as lead naphthenate. Lead naphthenates obtained from relatively low molecular weight naphthenic acids, such as those having molecular weights in about the range from about 120 to 235, and preferably in the range from about 200 to about 230, are particularly suitable for this purpose. By means of this additive combination, good extreme pressure properties are imparted to these calcium hydroxy fatty acid soap greases without any substantial impairment of their rheopectic properties.

The following example is illustrative of grease preparations carried out in accordance with the preferred embodiment of this invention.

Example I A calcium 12-hydroxystearate grease was prepared in the manner described below.

The equipment employed in the preparation of this grease was a 150 pound capacity steam-heated laboratory kettle with auxiliary equipment for grease circulation with oil injection into the recycle stream as shown in FIG. 1. The circulation equipment consisted of a 1% inch pipe connecting the kettle drawoff with .a No. 2 Globe Rota Piston pump having a capacity of 1 gallon per 100 revolutions, or 18 gallons per minute, and a inch pipe extending from the pump to the top of the kettle.

In carrying out the grease preparation, the grease kettle was charged with 7 pounds of 12-hydroxystearic acid having a neutralization number of 179, a saponification number of 187 and an iodine number of 5, and 28 pounds of a refined paraflinic distillate oil having a Saybolt Universal viscosity at 100 F. of 342 seconds and a viscosity index of 93.5. Stirring of the mixture was begun, and one pound of lime with an equal weight of water were added to the mixture. Heating of the kettle was then begun and circulation of the grease mixture through the recycle line also was begun at a rate of 120 pounds per minute. The mixture was heated up to about 220 F. in about 35 minutes, at which time foaming had stopped. Injection of 28 pounds of the paraflinic oil into the recycle stream at the intake side of the pump was then begun at a rate of 50 pounds per hour while the temperature was maintained at about 220 F. by kettle heating. The mixture was then heated up to 250 F. in about 1 hour and maintained at 250 to 273 F. for about 72 minutes with continued recirculation and stirring. The heat was then cut off and 62.75 pounds of the lubricating oil were added in the same manner at a rate of 50 pounds per hour while the temperature dropped from 273 to 195 F. in about 79 minutes. A fluid product was obtained which was too soft for penetration tests.

The above product was changed into a smooth buttery N.L.G.I. No. 1 grade grease by moderate shearing as shown by the following tabulation:

tration (about 448) 6 Milled, 1 pass through Premier Colloid Mill at 0.003 in. clearance Unworked 303. Worked, 60 strokes 338.

circulated through shear valve at 60 p.s.i.-g. pressure drop for 1 /2 hrs.-

Unworked 306. Worked 33.9. After /2 hr. in Marlin Rockwell Bearing Test, 1750 rpm. 32.2.

Obviously, many modifications and variations of the invention, as herein-before 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. The process of preparing a rheopectic lubricating grease comprising essentially a lubricating oil as the chief component and a grease forming amount of calcium 12- hydroxy stearate, which comprises essentially saponifying a 12-hydroxy stearic acid material with a basic calcium compound at a mildly elevated temperature in the presence of a paraffinic lubricating oil which is substantially non-reactive under the saponification cdnditions in an amount equal to at least about 2 times the weight of the said saponifiable material, heating the grease mixture thus obtained up to a maximum temperature in the range from about 260 F. to 275 F. and below the melting point of the soap in from about 1 to about 5 hours with the addition of any additional amount of lubricating oil required to give an oil-soap ratio of at least about 5:1, respectively, and thereafter cooling the said grease mixture with the addition of additional lubricating oil at a substantially lower temperature than the grease mixture, said heating following the saponification and substantial dehydration in the temperature range up to at least about 240 F. being carried out upon a maintained body of the said grease mixture in a grease making zone with continuous recirculation of the grease mixture through an external recycle line at a rate such that the weight of grease mixture recirculated is at least equal to the total weight of grease mixture within about 22 minutes, said process being carried out without any substantial shearing of the grease mixture during the said heating at above about 240 F. and during the said cooling other than that resultingfrom stirring and recirculating the grease mixture through the said recycle .line.

2. The process of claim 1 wherein the said heating step is carried out with continuous recirculation of the said grease mixture at a rate such that the weight of recirculated grease mixture equals the total Weight of grease mixture in about 04-15 minutes.

3. The process of claim 1 wherein the saponification step is carried out with continuous shearing of the saponification mixture.

4. The process of claim 1 wherein the saponification is carried out in the presence of lubricating oil in an amount from 2 to about 4 times the weight of the saponifiable material and additional lubricating oil is added after the dehydration is substantially complete in an amount sufiicient to provide an oil-soap mixture comprising lubricating oil in an amount from about 7 to 12 times the weight of the said soap.

5. The process of claim 3 wherein the said additional lubricating oil is preheated to a temperature above the temperature of the grease mixture.

6. The process of claim 1 wherein the said saponifiable material is 12-hydroxystearic acid.

7. The process of preparing a fluid lubricating grease comprising essentially a mineral lubricating oil as the 7 chief component containing about 2-12 percent by weight of calcium 12-hydroxystearate and having the property of thickening to a grease consistency upon shearing, which comprises essentially saponifying a 12-hydroxy'stearic acid material with a basic calcium compound at a mildly elevated temperature in the presence of mineral lubricating oil in an amount giving a weight ratio with the said 1- hydroxystearic acid material from 2:1 to 4: 1, respectively, heating the grease mixture thus obtained up to a maximum temperature in the range from about 260 F. to about 275 F. in about 15 hours While adding additional mineral lubricating oil in an amount sufficient to give an oil-soap ratio from about 7:1 to about 12:1, respectively, and thereafter cooling the grease mixture with the addition of additional mineral lubricating oil at a lower temperature than the grease mixture, said heating and cooling being carried out upon a maintained body of the said grease mixture in a grease making zone with continuous recirculation of the grease mixture through an external recycle line at a rate such that the weight of grease mixture recirculated during the heating cycle is equal to the total average weight of grease mixture in the heating cycle in about 0.2515 minutes, said process being carried out with no substantial shearing of the grease mixture during the said heating and cooling other than that resulting from stirring and recirculating the grease mixture through the said recycle line.

. 8. The process of claim 7 wherein the oil-added during the heating and cooling steps is introduced into the said recycle line.

9. The process of claim 7 wherein the oil added during the heating is at a temperature above the temperature of the grease mixture but below the melting point of the soap.

10. The process of claim 7 wherein the saponification is carried out with continuous circulation of the saponification mixture through a shear valve with a pressure drop of about 25-125 pounds per square inch.

References Cited by the Examiner UNITED STATES PATENTS 2,332,202 10/1943 Calkins 25242.1 2,450,220 9/1948 Ashburn et al 252-41 2,830,022 4/1958 Nelson et al. 252-41 2,870,090 1/1959 Pitman et al. 25239- 2,886,525 5/1959 Dilworth et al. 25239 3,015,624 1/1962 Hencke et al. 25241 3,068,174 12/1962 Pelton et al 25239 3,068,175 12/1962 Roach et a]. 25239 3,079,341 2/1963 Coons et al. 25241 3,117,087 1/1964 McCormick et a1 25241 DANIEL E. WYMAN, Primary Examiner.

I. VAUGHN, Assistant Examiner.

Claims (1)

1. THE PROCESS OF PREPARING A RHEOPECTIC LUBRICATING GREASE COMPRISING ESSENTIALLY A LUBRICATING OIL AS THE CHIEF COMPONENT AND A GREASE FORMING AMOUNT OF CALCIUM 12HYDROXY STEARATE, WHICH COMPRISES ESSENTIALLY SAPONIFYING A 12-HYDROXY STEARIC ACID MATEIAL WITH A BASIC CALCIUM COMPOUND AT A MILDLY ELEVATED TEMPERATURE IN THE PRESENCE OF A PARAFFINIC LUBRICATING OIL WHICH IS SUBSTANTIALLY NON-REACTIVE UNDER THE SAPONIFICATION CONDITIONS IN AN AMOUNT EQUAL TO AT LEAST ABOUT 2 TIMES THE WEIGHT OF THE SAID SAPONIFIABLE MATERIAL, HEATING THE GREASE MIXTURE THUS OBTAINED UP TO A MAXIMUM TEMPERTURE IN THE RANGE FROM ABOUT 260*F. TO 275*F. AND BELOW THE MELTING POINT OF THE SOAP IN FROM ABOUT U TO ABOUT 5 HOURS WITH THE ADDITION OF ANY ADDITIONAL AMOUNT OF LUBRICATING OIL REQUIRED TO GIVE AN OIL-SOAP RATIO OF AT LEAST ABOUT 5:1, RESPECTIVELY, AND THEREAFTER COOLING THE SAID GREASE MIXTURE WITH THE ADDITION OF ADDITIONAL LUBRICATING OIL AT A SUBSTANTIALLY LOWER TEMPERATURE THAN THE GREASE MIXTURE, SAID HEATING FOLLOWING THE SAPONIFICATION AND SUBSTANTIAL DEHYDRATION IN THE TEMPERATURE RANGE UP TO AT LEAST ABOUT 240*F. BEING CARRIED OUT UPON A MAINTAINED BODY OF THE SAID GREASE MIXTURE IN A GREASE MAKING ZONE WITH CONTINUOUS RECIRVULATION OF THE GREASE MIXTURE THROUGH AN EXTERNAL RECYCLE LINE AT A RATE SUCH THAT THE WEIGHT OF GREASE MIXTURE RECIRCULATED IS AT LEAST EQUAL TO THE TOTAL WEIGHT OF GREASE MIXTURE WITHIN ABOUT 22 MINUTES, SAID PROCESS BEING CARRIED OUT WITHOUT ANY SUBSTANTIAL SHEARING OF THE GREASE MIXTURE DURING THE SAID HEATING AT ABOVE ABOUT 240*F. AND DURING THE SAID COOLING OTHER THAN THAT RESULTING FROM STIRRING AND RECIRCULATING THE GREASE MIXTURE THROUGH THE SAID RECYCLE LINE.

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