US2527789A

US2527789A - Process of and apparatus for cooling a lubricant

Info

Publication number: US2527789A
Application number: US666790A
Authority: US
Inventors: Arnold A Bondi
Original assignee: Shell Development Co
Current assignee: Shell Development Co
Priority date: 1946-05-02
Filing date: 1946-05-02
Publication date: 1950-10-31
Anticipated expiration: 1967-10-31
Also published as: GB642948A

Description

A. A. BONDl Oct' 31, 1950 PROCESS OF AND APPARATUS FOR COOLING A LUBRICANT Filed May 2, 1946 3 Sheets-Sheet l INVENTOR 4W. fl

ATTORNEY PROCESS OF AND APPARATUS FOR COOLING A LUBRICANT Filed May 2, I946 V A. A. BOND! 3 Sheets-Sheet 2 INVENTOR;

ATTORNEY A. A. BONDI Oct. 31, 1950 PROCESS OF AND APPARATUS FOR COOLING LUBRICANT Filed May 2, 1946 3 Sheets-Sheet 3 INVENTOR, M a:

A. m x,

' ATTORNEY.

Patented Oct. 31, 1950 TENT OFFICE v PROCESS OFAND APPARATUS FOR COOLING A LUBRICANT Arnold A. Bondi, New Orleans, La., assignor, by

mesne assignments, .to ShellDevelopment Com- ,pany, San Francisco, Calif., a corporation of Delaware Application May 2, 1946, Serial No. 666,7 90

Claims.

- The present invention relates to a process of and apparatus for the cooling of lubricants and I especially lubricating greases,

.More'particularly, the present invention relates to a process of quickly tcooling a lubricating grease containing a soap base which because of its inherent structure, or because of the presence of a crystallization.inhibitor, prevents the formation of hard soap granules and subsequent disintegration'of the igreaseiupon" the quick chilling. Whllecthe invention is,:'in general, applicable to all greases. 'IhaNing the characteristics above stated, it is ofpa'rticularivalue in the quick cooling of allubri'cating grease containing an alkali metaltsoapofa higher fatty acid, said-grease also containinga fsuit'able lubricating oil, preferably afmineral oil, although there may be substituted fo'r'pa'rt 'of the mineral oil animal and/or vegetable oils.

From a process stan'dpoint the invention comprises feeding'a grease of the character set forth in ahot fluid condition .to a heat conductive or heat conducting surface, formingon said surface art-bin layer 'of'the grease, and exposing the grease whileiin a quiescentstate to the action of a heat a-b'sorbingmedi-um until there is produced-a gelled coherentm'ass of grease. Inother Words, while the l grea'se is cooling, it is not subject to any shearing stress.

'The'invention also relates toa novel apparatus for cooling lubricating greases of the character herein set forth which enables the grease to be cooled in a relatively rapid manner in the absence of any shearing stress, that is while the grease is maintained in a quiescent state. Lrubr icating greases at the present time 'are ordinarily cooled'by flowing the molten grease into asuitable pan or the like where a relatively thick layer of grease is formed, and the grease is then slowly cooled until substantially solidified or gelled. e

It has also been proposed to cool grease by rapid fiowthrough a narrow annulus through two concentric cylinders, one of which is provided with a jacket through whichcooling water flows, and the other of said cylinders is equipped with scraper blades, one of said cylinders rotating at relatively-high speed. This method of cooling is applicable to only certain lubricating greases containing aluminum soaps or lithium soaps, orbo-th' aluminum soaps and lithium soaps. v The present inventionis' particularly applicable to the quick"-'coolin'g 'of an-hydrous soda base -greases, and greases of this character can not-be cooled in the apparatu's of the character -set forth, since during the cooling step the anhydrous soda base greases would be subjected to a shearing stress, and this seriously affectsthe property of the grease.

It may also be pointed out that another disadvantage of cooling greases while effecting rapid shearing of the grease during cooling is the excessive energy consumption of the cooling equipment, said energy consumption amounting to about 30 H, P. hours per thousand pounds of lubricating grease cooled. In contradistinction, employing the present invention, only 2 H. P. hours per thousand pounds of grease cooled are required.

In accordance with the present invention, it

has been found that various types of greases can be successfully cooled if the grease is fed to a steel belt or the like so as to form a relatively thin continuous layer on the steel belt and subject it to a current of air or other cooling medium, so that the grease while being carried along with the belt is cooled in a uniform fashion free from shearing stress. By cooling in this manner, an unusual degree of transparency and smoothness of the finished grease can be produced, this same transparency and smoothness being extremely desirable characteristics of the grease. Further, the cooling of grease in this manner results in a grease of higher consistencies, and lesser amounts of soap can be used to produce a grease of equal consistency.

It is one ,of the objects of the present invention therefore to provide a method for the cooling of grease comprising feeding the grease in hot fluid condition to a heat conductive surface in an amount to form a thin layer on the surface, and then exposing the grease in the absence of shearing stress to the action of a heat absorbing medium.

A second object of the present invention is to flow a compounded grease in hot fluid condition onto a relatively thin metal band so as to form a thin layer varying from approximately 0.1" to one inch in thickness on the band,-and to thereafter move the metal band and grease through a cooling zone to form a highly transparent grease.

' A third object of the present invention is to Subject grease spread in a thin layer and in fluid condition on a metal band to' movement through a cooling zone while subjecting the grease to a counterflow of cooling air so as to rapidly cool the same to the desired consistency.

A fourth object of the present invention is to quickly cool lubricating greases spread in thin layers while in a quiescent state when they are not subjected to shearing stress, said lubricating greases being insensitive toquick cooling, as herein set forth, in that they do not disintegrate subsequent to chilling and form hard soap granules. By thin layers of grease is meant layers of lubricating grease which are less than about one inch in thickness. Some greases by virtue of their structure are inherently insensitive to quick cooling as herein set forth, and others must have present crystallization inhibitors which may be organic or inorganic, said inhibitors preventing the formation of hard soap granules during and after cooling, said hard soap granules causing the lubricating grease to disintegrate. The invention is particularly applicable to the quick 0001- ing, as herein set forth, of anhydrous soap greases containing 3 to 25% of a sodium soap of a higher fatty acid; and also to lubricating greases containing a lithium soap of the higher fatty acids, the lithium soap content varying from 3% to 20%, said percentages being taken on the total weight of the grease.

A fifth object of the present invention is to subject the grease While in a thin layer and in a quiescent state where it is not subjected to shearing stresses to a heat absorbing cooling medium, and thereafter terminate the cooling of the grease at a temperature permitting the soap content of the lubricating grease to crystallize, and then maintaining the grease in a quiescent state above the critical crystallization temperature, whereby the crystals of the soap present in the grease continue to grow. As a given grease, and especially the hydrous or anhydrous sodium soap and lithium soap greases start cooling from their heated fiuid state, when the critical temperature is reached, the soap content of the grease begins to crystallize. If the lubricating grease is cooled below the critical temperature, the tendency of the soap content of the lubricating grease, as for example, the sodium soap of the higher fatty acids or the lithium soap of the higher fatty acids, to crystallize is substantially destroyed or inhibited, and simultaneously the growth of the soap crystals is inhibited. For anhydrous lubricating greases made with a mineral oil or any other hydrocarbon oil, or with an animal or vegetable oil, said grease containing about 3% to about 25% total soap content of which the sodium soap or" the fatty acid may comprise 3% to 25%, the critical cooling temperature beyond which the grease should not be cooled in order to prevent crystallization of the soap content of the grease is 160 F. However, the total soap content of the grease may include in addition from 3% to 25% of a sodium soap of a fatty acid, 6.1% to 2% of other soaps, as for-example, 0.1% to 2% of aluminum, barium, calcium, magnesium, or lithium soaps of saturated fatty acids of the character herein set forth and, particularly, those saturated fatty acids having between 14 and 22 carbon atoms in a molecule. The grease may also contain in addition from 3% to 25% of a sodium soap of a fatty acid, about 0.1% to about 2% of aluminum, barium, calcium, magnesium, or lithium soaps of 12-hydr0Xy stearic acid. The grease may also obtain in addition from 3% to 25% of sodium soap of a fatty acid, up to 2% of a mixture of soaps other than the sodium soap, as for example, a mixture of any or all of the soaps above set forth ranging from 0% to 100% of either component. For example, there may be up to 1% of aluminum soap of a fatty acid and up to 1% of a lithium soap of 12-hydroxy stearic acid or 4 other hydroxy stearic acid, the balance of the soap content of the grease being 25% of a sodium soap of a fatty acid. In other words, it is clear from the above that the total soap content of the sodium soap grease may include small percentages ranging from .l% to 2% of other soaps.

A sixth object of the present invention is to provide a method of continuously cooling lubricating greases in thin layers of the character herein set forth and while in a quiescent state, the rate of cooling of the grease being varied as the grease cools from its hot fluid state, said procedure improving the quality of the resulting grease.

A seventh object of the present invention is to quickly cool greases of the character herein set forth while in thin layers in successive cooling zones, one cooling zone being adjacent the hot end of the cooling belt, and the other zone being adjacent the discharge end of the cooling belt, said zones being for convenience designated respectively hot and cold cooling zones, there passing through the zones a cooling medium, and there being a differential between the velocity of i the cooling medium in the two successive cooling zones. The ratio of the velocity of the cooling medium in the cold zone to the velocity of the cooling medium in the hot zone varies over the range of 1:1 to 10:1. 7

An eighth object of the present invention is to provide an apparatus for the cooling of grease consisting substantially of a continuous metal band or belt capable of supporting the grease in substantially horizontal position, so as to enable the same to be spread out thereon in the form of a relatively thin uniform layer, and to provide a cooling zone or chamber through which the band or belt moves so as to rapidly and uniformly cool the same.

A ninth object of the present invention is to provide an apparatus for the cooling of grease comprising a horizontally disposed thin metallic belt, means to move the belt, and means providing a cooling zone about the belt, means to feed fluid grease to the surface of the belt adjacent one end, and means to remove the solidified grease from the other end of the belt.

A tenth object of the present invention is to provide an apparatus including a cooling zone for grease through which a thin metallic belt is moved, and a feeding zone which is suitably arranged so as to be free from the free flow of cooling medium so that rapid cooling of the grease is inhibited in the feeding zone and the fluid grease tends to spread out into a uniform layer.

An eleventh object of the present invention is to provide a novel apparatus for the cooling of grease, including a thin metallic belt and means to suppl cooling air both above and below the belt and in substantial parallelism with the belt so as to uniformly cool a layer of grease disposed on the upper surface of the belt.

A twelfth object of the present invention is to provide novel supporting means for the belt which support the belt uniformly over its entire width and which may be adjusted so as to bring the belt into absolute horizontal position, said supportingmeans being so disposed that a minimum of air resistance to the flow of cooling air is produced thereby.

Other objects and advantages of the present invention will become apparent from the subsequent description and figures of the drawing,

wherein:

Figure 1 is a-plan vviewof a grease cooling appara us in a or a ce. wi h t e. ese t invention;

Fig. 2 is a detail of the end of the beltshom ing the cooling means and baflling means taken substantially on the line ,2.2 of Fig. 1;

Fig. 3 is a section taken on the. line 33 of Fig. 2, illustrating the grease feeding means;

Fig, 4 is a detail of the. supporting means for the upper portion of the belt}.

. Fig. 5 is a section taken substantially the line 5.5 of Fig. 1;

Fig. 6 is a side elevationof the grease cooling apparatus of the presentinvention;

Fig. '7 is a section taken substantially along. the line 1?! of Fig. 6; V

Fig. 8 is an enlarged detail of the. means for removing the grease from the belt;

Fis- 9 is a e levation of a mod fied. form of the grease coolingv apparatus; and.

Fig. 10 is a plan view thereof.

Fig. 11 is an enlarged s de elevation. of a portion of the casing partly broken away to show the diverting baffies.

Referring to the, figures of the drawing, and particularly Fig. 1 thereof, a grease cooling apparatus in accordance with the present invention is indicated in general at, [0, The apparatus includes a sheet metalfcasing which is generally rectangular in cross. section, as best shown in Fig. 7, including a top ll and a. pair 0f. sides 12 and I3. The casing is, supported as by longitudinal I-beams l4, carried on transverse beams [-5. which are in turn supported in any conventional fashion on the columns [6. The casing is. pr f ably o t c ed f sheet metal r m y be constructed of any'suitable thin material of suflicient. structural strength.

Trained over suitable pulleys l1 and re is a steel belt I9, provided with a pair Qf'strips prefalong erably of a synthetic rubber, indicated at 211 and 2 respectively. These strips, which extend. entirely around the belt adjacent the edges thereof, prevent the hot grease rom, flowing off the edgesv of the. belt. They are preferably bolted to the belt. by suitable bolts not shown, althoughv they may be riveted or otherwise suitably fixed to the belt. The right hand pulley I8 is driven by means of a. suitable belt 22' from a variable speed transmission and motor indicated in general at 2.3 (Fig. 1). The belt is keptunder tension by a suitable tension means consisting of a tensioning frame 24 urgedby means. of a weight '25 connected to the tensioning frame as by cables 25 and turned over suitable pulleys 21;. Preferably, the weight 25 is sufficient to urge the frame 24 and journals 28 for the pulley I! with suhicient force so that the steel belt is kept constantly under'tension, and tends to assume a horizontal position. The upper course of the beltis preferably supporte on a plurality fofu-shaped steel rods, best shown in Fig. 4, and indicated by the reference numeral 29. A plurality of steel rods 2 9 are distributed across the width of the belt in any suitable manner. The lower ends of the steel rods are passed through supporting frame members 30, and are provided with a threaded section carrying nuts 3| and 32. This permits either endof' the rods to be raised or lowered, so that the belt may be supported thereon in an absolutely horizontal position. Further, the useof these rods does not present any substantial air resistance to the flow of cooling air which is passing alongthe lower surface of=the steel belt I 9. The cooling air is fed into the outlet end'flof the casing-about'thebelt from' 6 a pair of blowers 3.3V and 34, the blower; 33 being. positioned to direct air along the upper surface of. the belt, and the blower 3.4 to direct air along the lower surface of the belt, as shown in Fig. 6. A baffle is provided within the casing, indicated at so that the air fiow from the upper blower 33 is in substantial. parallelism withthe upper surface of the belt I9. A plurality of discharges are provided from the lower blower, one dis charge being on each side of the casing, and indicated at 36 and 3'8 respectively. It will be. noted that these discharges also feed in substantially parallel to the lower surface of the belt, and at the outlet end of the casing. The air is. exhausted from the casing as by a stack 38 di rectly communicating with the upper or top of the inlet end of the casing, and provided with a pair of

ducts

39 and 39a. communicating with the casing below the upper course of the belt, as best shown in Figs. 1 and 6. The lower course of the belt is supported in conventional fashion on idler pulleys. 4,0. The'lower course. of the belt lilav may also be supported in, any suitable manner, but preferably by steel rods as described above and as shown for support of the upper course of the belt E9. in Fig. 4. This lower course l9a..of the belt may, be encased and provided with means of supplying cooling medium throu h the casing. In this manner, the lower course I So may be used for the cooling of the grease, whereby the capacity of a given installation may be approximately doubled.

Grease is fed into the apparatus and dis tributed uniformly over the surface of the. belt as by an inlet conduit 41, feeding into a header 42, provided with a plurality of distributing outlets 43. Positioned between the. outlets Q3 and the exhaust stack 38 is an adjustable bafiie id which prevents too rapid cooling of the grease 'immediately after being fed, and permits the grease in hot liquid condition to spread out on the surface of the belt in a uniform layer. A dam in the form of an angle and indicated at 45. is provided to. prevent the grease from flowing off the end of the belt. Preferably the dam. or angle iron i5 is provided with oil resistant synthetic rubber ends or surfaces where it is in contact with the grease Y about 25 to 50% than the cross sectional area and there is thus provided prior to the exhaust stack of the device a relatively warm zone which is free from the cooling medium, i. e. as otherwise the coldair striking the grease is likely to causev chilling and non-uniformity in layer structure of the header 42..

The belt as shown in Fig. 6, is rotatedin a clock- Wise, direction, and; the cooled grease is removed from the'beltas. by a scraper 46, best shown. in

Fig. .8. A funnel 4'! ispositioned to catch the grease being removed from the belt and distribute.

the same into either one of a pair of

tanks

48 and 45 respectively, asshown in Fig..5.. The funnel 4"! is provided with a pair of ports. at. eachof its, sides, closed by sliding covers 511 and 55; When the cover 5l is in the position shown in Fig. 5,

grease will be fed into the tank When the" cover is slid downwardly to close the opening, and the cover 50 is slid upwardly to open the port, grease will be fed into the tank 49. The

tanks

48 and 49 are provided with conical bottoms, and feed through a valve 52 and a positive displacement pump 53 into a suitable grease strainer 54.

In the form of the apparatus shown in Figs. 9 and 10, an intermediate pair of

exhaust ducts

55 and 55a are provided at a point 56 located approximately one-third of the distance between the hot end of the casing and the cold end of the casing, the point 55 being closer to the hot end of the casing. The point 55 definitely marks the dividing line between the so-called fhot zone A and the so-called cold zone B. Also within the main casing 57 which corresponds to the casing I0 shown in Figs. 1 to 6, inclusive, there are provided

adjustable baffles

58 and 58a which serve to regulate the relative amount of air flowing through the

discharge ducts

55 and 55a respectively and the balance of the main casing. The intermediate exhaust ducts may be connected to the exhaust ducts 39 or communicate directly with the stack 38.

Utilizing the form of apparatus shown in Figs. 9 and 10, a portion of the cooling area or other cooling gaseous medium may be exhausted, that is let out at an intermediate point of the casing 57, the amount of air which is let out being regulatedby means of the

baffles

58 and 58a to thereby perform the first stage of cooling at a higher temperature level, that is at a lower rate of cooling as is desirable with some greases in order to improve their quality. In other words, the time of cooling is divided up into two periods, a first period and a second period. The rate of cooling when the grease is hot, that is during the first period, is lower than the rate of cooling during the second period when the grease has already cooled somewhat and started to gel. By exhausting the cooling medium intermediate the hot and cold ends of the cooling grease layer, there is maintained a control over the velocity of flow of the cooling medium in the casing while the cooling medium is in contact with the moving layer of the grease. The distance through whichthe grease spread ina thin layer travels from the hot end of the grease layer to the cold end of the grease layer is divided, as stated, into what may be termed a hot zone A and a relatively cool zone B, and the grease is then cooled in these zones or stages, namely a first stage and a second stage. In the first stage at and adjacent the hot end of the grease layer the velocity of the cooling medium is preferably lower than the velocity of the cooling medium in the second cooling stage at and adjacent the cool discharge end of the grease layer. The ratio of the velocity of the cooling medium in zone B, that is, the second stage, to the velocity of flow of the cooling medium in the hot zone A, that is the first stage, may vary over the range of 1:1 to :1. In other words, the rate of cooling in zone A is lower than the rate of cooling in the second coolin stage in zone B. More specifically, the rate of cooling of the lubricating grease from its hot fluid state which may be as high as 450 F. down to about 200 to 275 F. is slower than the rate of cooling in the second cooling stage in zone B where the grease cools to about room temperature which in different localities may vary from about 40 F. to 120 F. If desired, the cooling may be carried out in two stages so that in zone B the grease is cooled down to about 200 F., that is above the critical temperature of the grease where the at temperatures as high as 120 F.

grease is in a rubbery stage, and then the grease' may be stored and converted to a gelled buttery texture.

The cooling medium may be conditioned by adjusting its temperature and/or velocity, and by other physical or chemical characteristics to cool the grease at a slower rate of cooling in zone A than in zone B. For example, for soda soap grease the rate of cooling in zone A may be such as to cool the grease down to 200 F. to 275. F. during a time period of travel initially therethrough than the period of travel in zone B. For example, with 100 foot belt, zone A may have a length of 33 and zone B a length of 66%. Witha uniform rate, of coolingin each zone, the grease may be cooled down to 200 to 275 F. in zone A and from 200 to 275 F. to room temperature in zone B. The ratio of the time of cooling in zone B to zone A when it is desired to cool at different rates may Vary from 2:1 to 5:1.

Preferably the grease is fed to the belt at such a speed so that a layer of grease of the proper thickness is produced. If the layer on the belt is more than approximately one inch thick, the rate of cooling will be prohibitively low, and in the case of certain greases the grease will tend to flow in an uncontrollable manner along the belt, due to the slow rate of gelation. If the layer is less than 0.1, the rate of heat transfer through the grease is more rapid than the rate of heat removal from the grease by the air stream within the practicable range of air pressures, and air velocities. Preferably, the grease is cooled by air at room temperature, but the air used for cooling purposes maybe passed through a suitable refrigeration plant and supplied to the cooling duct at. a temperature as low as 0" F. On the other hand, where warm outside temperatures prevail, the cool air may be supplied In other words, in general the cooling air at atmospheric or higher pressures may be supplied at temperatures of 0 to 120 F. Preferably however, the grease should be cooled to approximately and therefore the cool air should be supplied at a temperature lower than 90 F. and preferably between 40 F. and 90 F. Since the grease moves in a thin layer on the belt, the various particles of grease are not displaced relative to one another, andcthere is no shearing stress set up.

In general, the belt is preferably approximately feet long, and moves at a speed of 13 feet per minute, so that the total time of cooling for the average grease is approximately 7 minutes, This is sufi'icient to cool thegrease and set the same atleast to a jelled mass. The

blowers

33 and 34 maybe a standardtype of blower capable of blowing approximately 30,000 cuaft. a minute, and the

tanks

48 and 49 are capable of, holding one charge of the belt. In the case of a belt approximately 6 ft. wide andlOO ft. long,

this would amount to approximately 15,000

7 pounds. By providing two tanks of this type,

the grease may be allowed to remain in a quiescent condition after cooling.

The present apparatus and process may be applied to the cooling of aluminum stearate base 9 greases which containv small polyalkylene glycols, these polyalkylene glycols being preferably those above the tri-alkylene glycols and including the polyethylene glycols, the polypropylene glycols, the polybutylene" glycols and/or the monoesters of the aforementioned polyglycols having a molecular weight varying from about 500 to 6500. Good results have been obtained by using polyglycols having a molecular weight of about 700.

The method and apparatus herein set forth is especially applicable to soda base greases which either by virtue of their structure or because of the admixture of crystallization inhibitors have been made insensitive to quick chilling in thin layers in that they do not disintegrate subsequent to' cooling in thin layers. By quick cooling is I meant cooling in thin layersfrom approximately 400 F. or 450 F., but preferably from around 330 to 380 F. to room temperaturein a period of less than 'onehour, and preferably in less than thirty minutes when the grease is cooled in units. l of 100' long and 6' wide'.'- Preferably the grease canbe'quickly cooled in a time period of 3'to 15 minuteswhen spread in thin layers and cooling down from 450 F. to room temperature. More specifically, an anhydrous sodium soap grease containing between 3 and 25% of a sodium soap Of a higher fatty acid, as for example sodium stearate,

may be cooled in accordance with the present inhibitors such as the alkylene polyglycols, their.

esters and aromatic others, as w'ell'as-other poly ethers including" aromatic, aliphatic, and cycloaliphatic ethers containing at least one hydroxyl groupper molecule. Thesecompounds are designated crystallization inhibitors, that is the prevent the soap in the lubricating grease from forming hard granules which separate from the oil of the grease and cause the grease to disintegrate.

A soda soap grease which is particularly adapted-for cooling in accordance with the present process is set forth in co-pending application, Serial No. 655,887, filed March 20, 1946.

A typical soda base grease which may be cooled utilizing the present apparatus may comprise the a following ingredients:

Stearic acid, 200 gms. (3.35%) Hydrogenated Castor Oil, 35 gms. (0.58%)

' Polyethylene Glycol I500 molecule wt, 10 gms.

(0.166%) V Coastal pale oil, 100 vis., 500 gms. (8.35%) Sodium Hydroxide, 32.5 gms. (535%) I Metallic Sodium, 18.5 gms.

Coastal pale oil, 100 630 gms. (10.5%) p Coastal red oil, 2000-vis., 4600 gms. ("76'.5l9%) temperature raised to 260 F. until the reaction mass assumes a syrupy appearance. There is then added additional coastal oil and additional amounts of higher red oil, and the temperature is maintained at grease is then fed on to the belt IQ of the present apparatus at such'a rate so that a depth of grease layer of one-half inch is produced. Cooling air mately '7 minutes, and is then dischargedinto one. of the tanks 48. 01 50. The temperature of the. grease upon discharge to the tank is 150 F. The

grease is then strained through the strainer 54;

There is produceda non-bleeding transparent soda base chassis grease of excellent mechanical stability, having the 'ASTM work penetration of 298idecimillimeters after. 60 strokes, and 318 decimillimeters after 300 strokes. The resulting grease had a melting point of 348 F., and acidity equivalent to 0.08% oleic acid. Other'types of.

grease may be cooled in the present apparatus;

and in accordance with the present method. For example, as. previously pointed out, aluminum stearate grease maybe cooled in the pres- I ent apparatus.

The herein set forth process of cooling and apparatus may be used for the cooling of lithium base greases. Atypical lithium soap grease may be compounded as follows:

Lithium stearate 9;5' Solvent refined coastal oil, 75 vis. at 100 F. 61.5 Solvent refined Bright stock oil 30.

The above ingredients are mixed and cooked at a temperature of about 390 F. in the conventional manner. belt. I 9 at such a rate as to provide-a spread layer of grease of about in thickness. A 100 foot unit of. the grease is cooled in 8 minutes from a temperature of about 390 F. to a temperature of" about F. and there is produced a grease of smooth buttery textureh'aving a worked penetration after 60- strokes of 319 decimillimeters, and after 300 strokes of 335 decimillimeters, the grease hada melting point of 335 F.

In calculating the belt speed, the following formula is used:

where Ub=belt speed V/ t=vo1ume to be produced per unit time h=thickness of grease layer w=width ofbelt For a belt of given dimensions therefore, the only true variable is ,h if a certain. rate of :heat 7 removal is to be attained, since the equation applies: 1

Where q/t equals rate of. heat removal perunit following time, 1 equals belt length, flu). equal an exponen tial function of the temperature difference be-.

tween grease and air along, the belt. Av equals the rate of a heat transfer of the grease, and Q0 equals the total amount of heat to be removed,

per unit of area. It is obviousthereforefrom the.

two equations above that the belt speed canbe readily determined once the belt dirnensions'and rate of production under given'temperaturecon- Per cent The'greaseis then pumped on to the" 1 1 ditions have been fixed, since, as previously pointed out, the thickness of the grease layer should be kept within certain definite limits. Preferably the air velocity is one which will give a heat transfer coeflicient above 4 B. t. u. per hour per square foot per degree F. in order to remove the heat faster from the grease surface over a major area of the belt than it is conducted to the surface from within the interior of the grease mass. The corresponding air. velocity can then be determined from the graph given in William H. McAdams Heat Transmission, 1942, p. 206. Obviously, there are upper limits of air velocities which can be used best on economic considerations, since the power required increases rapidly with the volume of air handled.

In general, in carrying out the present invention, the saponifiable organic constituents of the grease making batch may be any of the saponifiable organic constituents used generally in the production of a grease. Fatty acids usually used in grease making are in general the saturated fatty acids containing up to 32 carbon atoms, and usually from 14 to 22 carbon atoms; and the unsaturated acids containing up to 32 carbon atoms and usually ranging from 18 to 22 carbon atoms. Instead of using the fatty acids, the glycerides thereof may be used as well as the monohydric alcohol esters of said fatty acids or the wax esters of said acids. .The oil constituent of the grease making batch is usually a mineral oil such as well known in the art, but may be a vegetable oil or an animal oil or fat usually used in the production of anhydrous soda base greases or in the production of lithium soap greases. The saponifying medium may be sodium hydroxide or metallic sodium. More specifically, the fatty acid constituent of the grease making batch which may be a saturated fatty acid or an unsaturated fatty acid includes stearic acid, 12-hydroXy stearic acid, 9,10-dihydroxy stearic acid, 4-hydroxy palmitic acid, iso-stearic acid, iso-palmitic acid, 12-hydroxy, 9-oleic acid (ricinoleic acid), oleic acid,

used in the sense common in the art; namely,

that the amount of moisture present is less than 25% based on the weight of the grease and pref erably is less than .1% based on the weight of the grease. In general, the polymerized. higher pol alkylene glycols having between 2 and 6 carbon atoms in the alkylene groups are effective carrying out the present invention, but those containing the ethylene and propylene groups are preferred. However, the butylene, amylene, and hexylene glycols may be used. The average molecular weight of the polyethylene glycols used in carrying out the present invention may vary from 200 to 7000 or 400 to 7000, the pre--' ferred molecular weight varying. from 1000 to 4000. It appears that the most effective average molecular weight is about 1500. However, any of the compounds set forth in applicants application Ser. No. 655,887 may be used in carrying out the present invention.

Referring again to the sodium soap greases i lcluding the anhydrous sodium soap greases produced in accordance with the present invention, said greases may carry from 1% to 50% of a sodium soap of a fatty acid of the character herein set forth, but more usually carry from about 1% to 15%, and preferably from 37 to '7 or 10%. V

The amount of the polyalkylene glycol including the polyalkylene glycols having between 2 and 6 carbon atoms in the alkylene groups of a molecular weight hereinbefore referred to may be present in the grease in amounts ranging from about .01% to .1% based on the weight of the grease, but preferably the minimum amount present in the grease should be about 05% in order for the-grease to be efiiciently and quickly;

cooled within the spirit of the present invention.

The preferred limit then becomes about. 05% to.

1.0% or greater amounts.

What is claimed is:' 1. The method of producing an-improved grease containing up to 25% of an alkali metal soap-Se lected from the class consisting-ofsodium. and

lithium soaps of a higher fatty acid; comprising 1 feeding the grease in a hot fluid condition to a heat-conductive moving surface, forming a thin soap of a higher fatty acid, comprising feeding the grease in a hot fluid condition to a heatconductive moving surface, forming a thin layer of less than about one inch thick of grease thereon, and cooling the grease while in a quiescent state by subjecting the greaseto the action of a stream of counter-current airfor'from about -3 to 15 minutes until there is produced a smooth homogenous grease.

3. The method of producing an improved grease containing from about'3% to 25% of a lithium soap of a higher fatty acid comprising.

feeding the grease in a hot fluid condition to a heat-conductive moving surfaca'forming a thin layer of less than about one inch thick of grease thereon, and cooling the grease while in a quiescent state by subjecting the grease to the action of a stream 'of counter-current air for from about 3 to 15 minutes'until there is produced a smooth homogeneous grease.

i. The method of producing an improved grease containin from about 3% to 25% of a sodium soapof a higher fatty acid and from- 0.1% to 1% of a grease structure modifier selected from the polyalkylene glycols having a molecular weight between 200 and 7000, com

prising feeding the grease in .ahot'fiuid condition to a heat-conductive moving surface,: forming a thin layer of less than about one in .1 thick of grease thereon, and cooling the:grease while in.

a quiescent state by subjecting the grease to the action of a stream of counter-current air for from about 3to 15 minutes until there is pro-' duced a smooth homogeneous grease.

5. The method of producing an improved grease containing from about 3% to 25% of a.

sodium soap of a mixture of stearic acid and hydrogenated castor oil in which the stearic acid is present in predominant amount and from 0.1%. to 1% of a grease structure modifier selected from.

the polyethylene glycols having a molecular 13 weight'between 200 and 7000 comprising feeding the grease in a hot fluid condition to a heat-conductive moving surface, forming a thin layer of less than about one inch thick of grease thereon, and cooling the grease While in a quiescent state by subjecting the grease to the action of a stream of counter-current air for from about 3 to 15 minutes until there is produced a smooth homogeneous grease.

ARNOLD A. BONDI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Fuller, Jr Feb. 10, 1914 Number Number 14 v Name Date Bausman June 1, 1915 Passburg Dec. 18, 1917 Gates Apr. 19, 1921 Mathy July 26, 1921, Hartshorn Oct. 2, 1923 Restein Mar. 17, 1925 'Wagner Dec. 7, 1926 Greer et a1. Apr. 8, 1930 N111 Nov. 28, 1933 Dotzer et a1. Dec. 19, 1933 Rasmussen Aug. 3, 1937 Downey Nov. 15, 1938 Scott Mar. 14, 1939 Randolph July 14, 1942 Bausman Jan. 5, 1943 Arnold Nov. 21, 1944 Bax et a1 Aug. 27, 1946 FOREIGN PATENTS Country Date Great Britain 1903

Claims

1. THE METHOD OF PRODUCING AN IMPROVED GREASE CONTAINING UP TO 25% OF AN ALKALI METAL SOAP SELECTED FROM THE CLASS CONSISTING OF SODIUM AND LITHIUM SOAPS OF A HIGHER FATTY ACID, COMPRISING FEEDING THE GREASE IN A HOT FLUID CONDITION TO A HEAT-CONDUCTIVE MOVING SURFACE, FORMING A THIN LAYER OF GREASE THEREON, AND COOLING THE GREASE WHILE IN A QUIESCENT STATE BY SUBJECTING THE GREASE TO THE ACTION OF A COUNTER-CURRENT GASEOUS HEAT ABSORBING MEDIUM FOR LESS THAN AN HOUR UNTIL THERE IS PRODUCED A SMOOTH HOMOGENEOUS GREASE.