US2298317A

US2298317A - Manufacture of lubricating greases

Info

Publication number: US2298317A
Application number: US354435A
Authority: US
Inventors: Herschel G Smith
Original assignee: Gulf Oil Corp
Current assignee: Gulf Oil Corp
Priority date: 1940-08-27
Filing date: 1940-08-27
Publication date: 1942-10-13
Anticipated expiration: 1959-10-13
Also published as: NL142820C

Description

2 Sheets-Sheet 1 @Www H. G. SMITH MANUFACTURE OF LUBRICATING GREASES Filed Aug. 27, 1940 Oct. 13, 1942.

DISCHARGE H THERMOCOUFLE fiensche l G. S e l/L,

Oct. 13, 1942, v 5 SMITH 7 2,298,317

MANUFACTURE OF LUBRICATING GREASES Filed Aug. 27. 1940 2 Sheets-Sheet 2 glwuewfm fierschd G. 6

Patented Oct. '13.,

MANUFACTURE OF LUBRICATING GREASES Herschel G. Smith, Wallingford, Pa... asslgnor to Gulf Oil Corporation, Pittsburgh, Pa., a'corporation of Pennsylvania Application August 27, 1940, Serial No. 354,435

28 Claims.

This invention relates to manufacture of lubrieating greases; and it comprises an improved method of manufacturing lubricating greases of the soap and oil type, in which'the grease constituents are subjected to agitation under vacuum during one or more of the stages of compounding, blending, extending, finishing and drawing the grease, said agitation advantageously being so accomplished that a positive upward axial flow is maintained in a relatively tall, narrow body of grease constituents with a positive downward flow at the periphery of said body and with both flows being disturbed and having a helical component, thus circulating the grease constituents with turbulent flow in a helical path and with the core and peripheral portion thereof flowing in opposite directions while in direct contact at 'their interface; and it also comprises apparatus in which this agitation under vacuum maybe readily effected and in which other steps in the manufacture of lubricating greases may also be effected conveniently and economically, said apparatus advantageously comprising a -relatively' more individual chemical. compounds.

systems but for practical purposes they may be re arded as gels. Thesoaps and oils employed are often not readily miscible at ordinary temperatures: but the miscibility improves at higher temperatu es and blending is therefore usually effected at hi h temperatures.

The lubricating oils employed in the manufacture of these greases are generally petroleum fractions or residues having properties and char- Most of of the alkali or alkali earth metals; sodium soaps and calcium soaps being widely used. Salts of various other metals, including potassium, aluminum, lead, zinc, barium, copper, magnesium and others, are also sometimes employed; usually for special purposes. The fatty acid constituents of the soaps generally have more than 8 carbon atoms, and ordinarily 16 to 18 carbon atoms. Acids containing less than 8 carbon atoms are generally of little value in producing greases of the consistency desired. -Suitable fatty acids may be obtained from various sources, including animal and vegetable fats and oils. Refinery foots from purifying animal and vegetable oils 'are in general use, and distilled fatty acids may also be'used. Sources of fatty acids suitable for grease manufacture include hard tallow, t'allow oil, stearin, cottonseed oil, fish oil, corn oil, palm oil and various hydrogenated fats.

While greases generally contain two principal ingredients-the soap and the oil-they are actually very complex colloidal systems. The

complexity is due to the fact that each of the: principal phases may include almost numberless chemical compounds. It has been estimated that a simple grease may contain five thousand or In addition, various modifying'constituents are often included in greases for special purposes.

In the manufacture of. all types of lubricating greases, the physical structure or consistency of the grease. and its stability with respect to oil separation upon aging, depend substantially on the technique of manufacture, which is usually quite as important as the ingredients used. The

ingredients, and particularly the lubricating oil,

are important from the standpoint of final lubricating properties; but the physical characteristics are also of great importance in connection with application and serviceability of the grease.

One desideratum in the manufacture of greases is to obtain a finished grease of high uniformity. Since the grease comprises a plurality of phases with numerous constituents in each phase the production of a uniform product is generally not a simple matter. necessary and this must generally be coupled with careful control of temperature, especially during the finishing stage of the grease. Generally, agitation must be so thorough as to be Thorough agitation is always substantially a colloiding treatment; and the apparatus employed must be designed accordingly.

Many variations in grease-making practice have been suggested heretofore, and several of them are intended to result in the production of a moreuniform grease. However, in many of these methods gases or vapors are developed in the grease mixture at the operating temperatures, or are trapped in the grease during agitation. This occlusion or inclusion of a gaseous phase in the grease has highly undesirable results. It impairs the uniformity of the product and it may also lead to reactions involving one or more of the grease constituents. One of the objects achieved by my invention is the elimination of gaseous inclusions in greases, which makes possible a product of substantially greater uniformity-a homogeneous colloidal gel.

More specifically, I have found that by conducting some or all of the finishing stages of grease manufacture under a suitable vacuum, difliculties due to gas inclusions may be eliminated. Operating under vacuum also makes possible a more thorough and vigorous agitation of the grease components, resulting in a more uniform product, having highly desirable characteristics, which are discussed in more detail hereinbelow.

I have found that a vacuum may be applied during the manufacture of greases, and especially during certain stages of manufacture, without adding substantially to the cost of manufacture. In fact, when the vacuum is applied in a suitable manner and in suitable apparatus, a substantial saving in the cost of manufacture, as compared with prior methods, is effected. Thus, in accordance with the present invention, I am able to pre-' pare superior greases; and I am able to prepare these at a cost lower than that required heretofore in the manufacture of inferior grades ofgreases.

This invention is applicable to the manufactureof many types of greases, including hard greases of high soap content and smooth consistency, such as locomotive driving journal compounds, and also including substantially all types of cup greases, fiber greases and special greases, including universal joint lubricants, wheel bearing greases, brake cylinder compounds, etc. In the manufacture of these various individual greases, the steps in the complete manufacturing procedure may vary somewhat; but in all cases, there is included the step of agitating under vacuum during one of the later stages of manufacture. This step is one of the features of the improved manufacturing procedure which constitutes a part of this invention.

. As another part of the present invention, I have devised an improved apparatus for making these uniform colloidal lubricating greases'from soap and oil, in which I use a tall, relatively narrow, cylindrical metal casing having a smooth inner surface. External heating and cooling means, and means for producing a vacuum within the casing, are provided. Within the casing I mount an agitating device which advantageously includes a coaxial pair of conveyors rotating in opposite directions. One of these is a bladed conveyor positioned adjacent the casing wall'with as little clearance as may be, and thus capable of producing powerful shearing stresses when rotated. Cooperating with this element and adapted to provide return circulation is an axial agitator and conveyor; and for this element I to be especially advantageous. Elements car- .ried by the two conveyors extend radially, and

when passed through the charge they provide additional mixing and development of shearing stresses.

In order. that the invention may be more readily understood, it will now be described with reference to the accompanying drawings, which show, somewhat diagrammatically, certain arrangements of apparatus within the purview of the invention, and useful in the performance of the described process. In these drawings:

Fig. l is a vertical sectional view of a vertical columnar type kettle;

Fig. 2 is a cross sectional view of the kettle, taken on line 22 of Fig. 1;

Fig. 3 is an enlarged fragmentary view of a scraper blade, taken on line 3-3 of Fig. 1;

Fig. 4 is an enlarged fragmentary view of another portion of the agitator, taken on line 4-4 of Fig. 1;

Fig. 5 is a view in elevation of the grease kettle assembled with one form of auxi1iary equipment, including a motor and a separately enclosed gearing for rotating the agitators;

Fig. 6 is an enlarged vertical section of the en-. closed gearing shown in Fig. 5; and

Fig. 7 is a sectional view of another type of I,

driving mechanism for the agitators in the kettle.

Referring to the drawings and more especially to Figs. 1 to 6, the apparatus includes a thinwalled kettle l0, advantageously fabricated from sheet=-steel and having a rounded bottom II and a rounded dome-like cover l2 detachably secured thereto at a fluid-tight joint It. The kettle is fabricated in any suitable way as by welding. The interior height is advantageously great compared to the diameter, as shown; at least about .1.5 times as great and often 3 or 4 times as great The kettle is conveniently supported on pillars It, by means of lugs l8, as shown. An inlet connection II at the top servesfor introduction of liquid grease ingredients, and means for removal or drainage of the kettle contents is provided by a valved outlet ll at the bottom. The movable part of the valve l8 advantageously includes a plug I! which, in closed position, becomes flush with the interior ofthe kettle bottom as shown, to prevent pocketing.

A connection 20 with suitable exhausting means (not shown) permits the interior of the kettle to be put under vacuum when desired; and a manhole 22 permits introduction of solids and inspection. A thermocouple 2| of compact type is perature measurement. Heating means are profind a particular type of helical ribbon convey r vided for the kettle, conveniently inthe form oi steam coils 2i surrounding the kettle for a ma or .j portion of its length, and advantageously ,nne, welded thereto. The line-welding ,may,be applied after an initial tack-weld, a nd insures rapid heat transfer between the coils and the kettle wall at all desired temperatures jifin insulating jacket 26 covers the coils'as sho wn 'lf cooling rather than heating is desired, cold water, etc.,

can be run through the coilis 'in neuior steam,

An ordinary jacket may be substituted'for the coil 25, ifdesired, but the line-welded coil makes it possible to heat and cool more rapidly.

Within the kettle is a double agitator-mixer assemblage. This includes a helical agitator of the conveyor type having 'an' axle 21, advantageously of tubular construction, on which is mounted a helical ribbon 28 by means of struts 9. At its lower end this inner 'helical agitator terminates with a stub shaft 30, seated for rotation in a thrust bearing 3|. At its upper end it is provided with a shaft 32, extending through the top of the kettle in the form shown in Fig. 1, by which the helix is rotated. v

There is also provided an outer, coaxial, independently rotated agitator or conveyor, includ ing a frame 33 closely spaced from the ribbon 28 and having attached thereto a plurality of staggered and inclined paddle blades 34. At their ends, these blades carry flexible metal scraper elements 35 arranged to scrape the kettle walls (Figs. 2, 3 and ,4) and clamped to the blade ends as shown at 36, for example. A bottom-scraping blade 31 is attached to frame 33, and is shaped to conform to the kettle bottom, as shown. It is advantageously cut out, as shown'at 38, to clear the thermocouple 2|.

Advantageously the interior of the kettle is smooth and accurately cylindrical, so that grease is continually removed from the walls and bottom by the scrapers without leaving any dead pockets or dead films. The annular zones of the kettle walls traversed by scrapers 35 slightly overlap, so that all parts of the wall are subjected to scraping action; there are no dead annular spaces untouched by the scrapers.

The bottom of frame 33 is provided with a bearing collar 39 surrounding the stub shaft 30 above the kettle by a support 41 receives the ends Shaft 32 is seated in an I of

shafts

32 and 4|. upper bearing 48 in the housing, and shaft 4| is seated in a lower bearing 49, sealed at 50 to prevent leakage of lubricant (not shown) from the housing. Shaft 32 .carries a gear meshing with a gear 52 on a jack-shaft 53, and shaft 4| through the kettle wall at a gland 56 and driven carriesa sprocket 54 containing a stufling gland 55 to prevent leakage of lubricant. The sprocket is driven from a sprocket 56 on the jack-shaft 53 1 by a chain 51. The jack-shaft extends through the top of the housing and is driven by a geared speed-reduction motor 58 through a coupling 59.

Shafts

32 and 4| are thus driven'in opposite directions.

The ratios of gears 5| and 52, and of

sprockets

54 and 56, are so selected that the inner helical agitator 28 is driven at a somewhat higher an gular speed than the outer agitator blades 34. These ratios are so selected that the quantity of material in the kettle moved downward a given distance by the outer agitator during a given period is about equal to the quantity moved upward by the inner agitator during the same period. The gearing in box is shown as speedincreasing gearing, but speed-reduction gearing can be provided instead, depending on the speed of the motor 58.

Fig. 7 shows another driving mechan sm for the compound agitators, which has the advantage of rendering the interior of the kettle readily accessible by simply removing the cover.

Shafts

32 and 4| both terminate within the kettle, at a point below joint l3. The inner driveshaft 32 is supported by a bearing 60, advantaadjacent the walls of the kettle.

at a suitable speed by a motor or other power means (not shown).

In the apparatus described, a number of features cooperate to produce the characteristically advantageous results of my invention.

For example, the tall and relatively narrow kettle maintains the charge or grease mixture in the form of a tall column during the compounding, blending and finishing operations. In this form, a greater amount of grease is maintained in contact with the kettle shell; and this facilitates temperature control. Likewise a lesser amount of grease is exposed at the top of the kettle and this minimizes oxidationwhen air is present above the grease.

The charging arrangement shown in the drawing is also convenient, since all materials can be delivered to the kettle and the kettle operation can be completely controlled from a charging platform (not shown) near the top of the kettle. The-feed pipe or inlet IT conveniently serves to deliver all of the liquid grease constituents to the kettle; these including mineral oils, fatty oils, molten fatty acids, aqueous solutions of alkali, etc., which may be admixed prior-to charging or may be introduced separately. If

desired, separate pipes or inlets for the different iiquids may be provided, and this is sometimes advantageous when very large kettles are employed. However, the number of openings or,

inlets in the kettle should generally be held to a minimum as this facilitates'the maintenance of the kettle in a gas-tight condition during vacuum operation.

The vacuum connection 23 mav also be used for controlling pressure during stages when the kettle is operated under superatmospherie conditions; during saponification, for example. Thus a branch of this pipe may be employed for venting the kettle, as by means of a pressure release valve; and the same or another branch maybe connected to a'source of compressed gas. A pressure gage may also be connected to this line. Thus the single connection may be. used to control all pressures during the various operations, by means of suitable connections and valves.

The compound agitator illustrated in the drawing is highly eflicient and the concentric rotation of the agitators in opposite direction produces a double motion agitation which is most efiicient in producing grease having a uniform gel structure. By agitation of this type, the grease mixture is maintained in turbulent flow with a major flow upwardly at the .center of the kettle and a major flow dovmwardly around the upwardly moving core of grease and In addition both major flows have a superimposed spiral component. This highly disturbed flew. in ad.- dition to producing uniform blending, gives better control of the temperatures of the grease. Rapid heat exchange with relatively quick heating and cooling are obtained, without local overheating or chilling.

In this improved agitator the design of the inner helical agitator conveyor is important. The relatively narrow spiral ribbon of this element picksup the grease at the bottom of the kettle and lifts it upwardly to the top of the body of grease mixture, where it flows radially to join the outer downwardly flowing grease. Some of this upwardly flowing central core of grease is also forced outwardly toward the walls while thoroughly agitating it. For this pur-' pose the vanes are set at a substantial angle to the plane of rotation, with the result that the grease is forced downwardlyin a continuous spiral path adjacent the walls of the kettle. When the grease reaches the bottom of the kettle it is forced along the curved bottom by the rigid bottom scraping blade 31 until it is picked up by the inner spiral agitator as described.

In operation, the kettle is charged with grease ingredients up to a suitable level, which may be substantially below the joint 13. The temperature of the charge is brought to the desired point, usually with thorough agitation in the manner described and with at least a substantial part of the agitation effected under vacuum.

the apparatus described and shown herewith was employed. These compositions can also be made in other types of apparatus, and the process of my invention can be practiced in other types of apparatus. However, the apparatus described and illustrated offers numerous advantages, as

previously indicated.

Example 1.-In one embodiment of my invention, a hard type of sodium soap grease, useful as a locomotive driving journal compound, was prepared. For each 100 parts of finished grease to be made, the kettle was initially charged with 9 parts of a previous batch of the grease and 7 parts of-caustic soda dissolved in 9.8 parts of water. The mixture in the kettle was thoroughly stirred and superheated steam at a tempera ture of 500 to 700 F. was passed through the heating coil. To this initial charge there was added a mixture of 42.5 parts of fatty acid and 47.8 parts of lubricating oil stock, which had been pre-heated to a temperature of 175 F. to melt the fatty acid and dissolve it'in the lubricating oil. The lubricating oil stock employed was a mixture of 85 per cent of cylinder stock and 15 per cent of a wax discharge from solvent treated Mid-Continent oil. The properties of the mixture were as follows:

Wax dis- Cylinder Mixcharge stock ture Gravity, A. P. I 31.2 21.4 22. 9 Viscosity S. U. V. 210 F; B3 215 173 Flash, 06, F 520 555 550 Fire, 00, F 640 635 our, +130 +30 +80 Carbon residue, percent 4. 88 3. 71

and the maintenance of the vacuum at high temperatures, are facilitated by the dome-like cover I 2. This provides a substantial space or "gas cushion above the charge, and also serves to prevent or minimize difliculties due to frothing of the charge.

In making some types of lubricating greases it i more convenient to provide, in the initial charge to the kettle, a previously made soap, with which oil is then admixed. However, it is sometimes more convenient to make a soap in the kettle, as by charging a fatty acid and an alkali, and effecting saponification in place, usually in the presence of part of the oil constituent. Such saponification may be effected at atmospheric pressure or superatmospheric pressure or under vacuum in the apparatus described; and after this part of the process is complete the addition of the remaining oil and the blending of the charge is readily efl'ected.

As previously noted, my process and apparatus are useful in the manufacture of substantially all types of lubricating greases; and all types can be prepared free of gas inclusions. Agitation under vacuum, especially at elevated temperatures, in accordance with this invention, provides no opportunity for the entrainment of air or other gas or vapor in the grease mixture, and causes rapid removal of any gases which are already present. Under these conditions, any bubbles in the charge become too much enlarged to be retained in the grease; they agglomerate and pass out of the mass.

In the following examples I have described advantageous methods of making several types of grease compositions within the purview of the present invention. In the described procedures,

The fatty acid used in this case was a, highmelting point product produced by the hydrogenation of a fish oil, followed by splitting the glyceride and recovering the fatty acid. This fatty acid had the following properties:

Melting point; F., capillary tube 128 Neutralization number 191 Iodine number, Mod. Hanus 8.0 Saponiflcation number 198 During and after addition of the mixture of lubricating 'oil and fatty acid, the contents of the kettle were heated rapidly, with control of the oil addition to prevent boiling over and excessive foaming. When all of the oil mixture was added, a temperature of about 350 F. had been reached. This temperature was maintained until the boiling and foaming subsided, and the kettle was then closed and a vacuum of 10 to 11 inches mercury (19 to 20 inches Hg, absolute pressure) was applied. The temperature was gradually increased to 450 F. over a period of four hours. The steam was then cut off from the kettle and thorough stirring was continued for approximately one hour, with the vacuum maintained. The vacuum was then released. agitation was stopped. and a sample of the grease the grease, which was then in a thin pasty condition; and the agitators were again operated while the grease cooled slowly to 400 F. Water was then circulated through the coils to reduce the temperature of the batch to the filling temtrimmings from a previous batch. instead of circulating water through the coils or jacket, and this is sometimes advantageous.

The grease was then drawn from the kettle through a IO-mesh screen into molds, applying low air'pressure to expedite the flow, with care that no air was included in the flowing grease, The grease was allowed to cool in the molds for about thirty hours, until it would form a smooth firm cheese" when pressed and cut. The grease was then pressed hard (applying a total pressure of at least twenty tons) and removed from the molds, cut and wrapped. The composition of this grease was as follows:

Parts by Ingredient weigh,

Lubricating oil stock Sodium soap of a fatty acid 46. 7 Water by distillation Trace Free NaOH 0. 8

Tests of the grease showed the following properties;

Water by distillation, per cent A. S. T. M. D 95-30 modified Trace. Freealkalinity as NaOH, per

cent 0.8. Ash, per cent 9.21.

Nature NazCOs.

Considerable difiiculties have been encountered heretofore in attempting to prepare hard greases of this type which are entirely uniform in character and free from soft spots and gas inclusions. These difficulties are eliminated when employing thorough and rapid agitation and uniform heating, with the critical blending and finishing operations efiected under vacuum, in accordance with this invention. Hard greases of high quality are thus prepared, in an economical manner.

Example 2.In another embodiment of my invention, the grease produced was of a semifibrous type and relatively soft consistency, useful as a universal joint lubricant. The final composition of this grease was approximately as follows:

Ingredients 322 2 3 Lubricating oil, Texas 6. 8 Lubricating oil, Mid-Cn 81.0 1 Sodium soap oi tallow 9. 8 Sodium soapoI-stearic acid l. 4 Glycerine 1.0 Free fatty acid as 'oleic 0. 04 Oil of cassia 0.002

The Texas lubricating oil used in this grease was an acid treated oil of 750 viscosity S. U. V.

' a solvent-treated, reduced centrifuged 011 of 175 eating all Gravity, A. P. I 22. 2 25. 7 Viscosity, S. U

210 64. 170. 9 Flash, 00, F 390 570 Fire, 00, "F 430 640 Four, "F l0 +10 Color, N. P A 3. 75 7. 5 dil.

, Carbon residue, percen 0. 24 0. 78

Neutralization number 0. 02 0. 04

The tallow employed in this grease as a constituent of the soap was edible beef tallow? The stearic acid was the single pressed grade. The properties of these constituents were:

In preparing thisgrease the initial charge to the kettle was 9.5 parts tallow, 1.3 parts stearic acid, 6.8 parts Texas lubricating oil and 4 parts Mid-Continent lubricating oil (for each 100. parts by weight of the finished grease).

The mixture was heated to a temperature between 150 and 175 F., and 1.7 parts NaOH dissolved the mixture was heated to 255 F. in two hours, with thorough agitation. superheated steam v was then applied while the temperature of the soap concentrate was raised to. 375 F. in two hours. The soap concentrate was then cooled at 300 F. in about 1.25 hours, with saturated steam in the coils. Nine parts of the Mid-Continent lubricating oil, preheated to 150 to 175 F.

at F. The Mid-Continent lubricating oil was 75 were ,then added in about 1.25 hours, thus reducing the soap content of the batch to about 35 per cent and cooling the grease to about 200 F. A vacuum of 20 inches of mercury was then applied to the grease, and was maintained while the-grease was finished by thoroughly working in 68 parts of Mid-Continent lubricating oil preheated to F. and the small amount (0.002 part) of oil of cassia. During this stage, the grease cooled to a temperature of about F. in three hours. The agitators were then stopped, the vacuum was relieved, and the grease was drawn slowly into drums to-avoid trapping air in the grease. This grease had the following properties:

Melting point,-F., Hawxhurst 270.

Flow point: F., method 58, Gulf 275. Penetration, A. S. T. M. D217-38 T: 77 F., 150 g., 5 sec.: Unworked. 243. Worked 290. Texture Semi-fibrous. Water by distillation, percent A. S.

T. M. D 95-30--- Nil. Free acidity as oleic, percent 0.04 Stability test, Grease Method 201,

Gulf Good.

As in the previous example, the application of vacuum during the finishing stage, with thorough agitation and temperature control, resulted in a grease having exceptional uniformity and other desirable characteristics.

Example 3.-In a further embodiment of my invention, a grease having a mixed calcium and sodium soap base, and of a type useful as a wheel-bearing lubricant, was prepared. The

The tallow and stearic acid used in this grease had the following properties:

composition of the final grease was approxi- 10 mately as follows:

Parts by Ingredient weight 500 viscosity at 100 F., solvent treated Texas oil 39. 6 120 viscosity at 210 F. solvent treated Mid-Continent reduced centrifu ed 011 39. 6 Calcium soap of ow 1. 6 Sodium soap of tallow 8. l Calcium soap of stearic acid... 1.6 Sodium soap of stearic acid- 8. 1

0e ne 1. 0 Free fatt acid as oleic 0. 2 Dipheny amine 0. 2

The lubricating oils employed in the manufacture of this grease had the following properties:

120 viscosity at 500 viscosity 210 F. solvent at 100 F. soltreated Midvent treated Continent 3 Texas oil reduced centriiuged oil Gravity, "A P I 25.0-27.0 25.0-27.0 Viscosity. S

210 120-130 Flash, 00, Min. 410 Min. 605 Fire, 0C, F Min. 575 Pour, "F Max. 0 0 to +10 Color, N. P. A 2. 0-2. 6

Tallow Stearic acid Melting point, .F., capillary tube. 115-120 Min. 130. Color Pale yellow to Pale ellow white. to w ite.

Color, N P. A Max. 2.5.

dor Nearly odorless. Not rancid. Neutralization number. Max. 6.0. Iodine number, Mod. Hanus Max. 0 Saponification number 192-200 5" In making this grease, the initial charge to the kettle was 9 parts of the single pressed stearic acid, 9.4 parts tallow and 19.5 parts of the solvent treated Texas 011 for each 100 parts of finished grease. This charge was heated to 175 F. and a mixture of 2.43 parts NaOH dissolved in 3.23 parts water, and 0.45 part Ca(OH)z as a slurry in 0.68 part water, was added to the kettle. This mixture was heated to 250 F. in about two hours with saturated steam. superheated steam was then supplied to the coils, and the temperature of the mixture was raised to 400 F. in about 1.25 hours, followed by cooling to 325 F. in 1.5 hours. Then 19.5 parts of the solvent-treated Mid-Continent oil, preheated to 150 F., were worked in as the grease cooled to 200 F. during a two-hour period. A 20 inch vacuum was then applied, and a mixture of 20.1 parts of the solvent-treated Texas oil and 20.1 parts of the solvent-treated Mid-Continent reduced oil, preheated to 150F., was worked in with thorough agitation during a two-hour period, while the grease cooled to 160 F. The diphenylamine was then added and worked into the grease as it 7 cooled to 100 F., following which working was continued .for about an hour under the 20 inch vacuum. The grease was then drawn and had the following properties:

Gravity, -A. P. I 22.6. Specific gravity, 60/60 F 0.918. Melting point, F., Hawxhurst 273. Dropping point, F., Method 287, Gulf 345. Flow point, F., Method 58 Gulf f 240.

Penetration, A. S. T. M. D 217-38 T, 77 F., 150 8., 5 sec.:

Unworked 246. Worked 265.- Water by distillation, percent A. S. T. M. D -30 Nil. Free fatty acids as oleic 0.15.

Oxygen stability, 176v F.,

Hr. Method 272, Gulf 500.

Ash percent 3.49. Nature CaO and NazCOa. Texture Smooth, long fiber.

In this embodiment, it was again demonstrated that maintenance ofvacuum, temperature control, and thorough agitation during a finishing stage, in accordance with this invention, result,

in the production of a grease of high quality and exceptional uniformity.

Example 4.-A calcium-tallow soap grease, useful as a cup grease, was also prepared in accordance with my invention. The composition of the finished grease was approximately as follows:

Ingredient 22m Lubricating nil 77. 7 Calcium soap of tallow l9. 0 Glymrlna 1. 9 Water by distillation 1. 4

The lubricating oil used in this grease was a Texas oil of 305 viscosity at F., having the following properties:

Gravity A. P. I 21.9. Viscosity, S. U. V., 100 F 305. Flash, 00 F 360.

Fire, 00 F. 400

Pour F Below 50. Color, N. P. A 5.0.

The tallow used in this grease had the following properties:

The procedure in this case involved forming the soap concentrate under pressure and finishing under vacuum; that is, maintaining a vacuum while adjusting the water content and blending the soap concentrate with oil. The initial charge to' the kettle was 18.6 parts of tallow and 37.2

parts of the Texas oil for each 100 parts by weight of the finished grease. The tallow and oil were heated with a slurry of 2.6 parts Ca(OH) 2 in 7.8 parts of water to a temperature of 150 to 175 F. The kettle connections were then closed and saturated steam was applied to raise the internal pressure to twenty pounds per square inch. This pressure was maintained for three hours, during which saponification was effected. The contents of the kettle were then cooled to a temperature of about 200 F., and a five inch vacuum was applied, with thorough agitation, until the water content of the concentrate was reduced to approximately two per cent (on the basis of the finished grease). Then 40.5,partsof the oil preheated to 150 F. were worked into the grease under five inches of vacuum.

The completed grease was then drawn from the kettle and found to have the following properties:

Melting point, F., Hawxhurst 197 Flow point, F., Method 58, Gulf 216 Penetration, A. S. T. M.- D. 217-33 T, 77

F., 150 g., 5 sec.

Unworked 160 Worked 260 Ash:

Percent 2.02 Nature 0210 In a modification of this .procedure, the soap was formed in substantially an equal weight of oil under pressures up to 55 pounds per square inch during a period of 1 to 2 hours. The soap concentrate was then expelled or expanded into the second kettle, open to the atmosphere, and

saponification of the calcium soap concentrate,

and expansion to remove most of the excess water as steam makes it feasible to finish the grease while progressively cooling, and without the delay and expense -ofa further heating operation, In other words, greases of the type know'n as boiled calcium greases can be prepared without boiling, and with relatively low soap contents coupled with improved stability and uniformity, in accordance with this invention.

Example 5.In another embodiment of my invention, a calcium-tallow soap was employed with flake graphite and phenthiazine to produce a grease useful as an' air-brake cylinder compound. The final composition of this grease was as follows: 0 v

Ingredient Eggs Lubricating oil 79. 1 Calcium soap of tallow 15.5 Glycerine l. 5 Water by distillation- 0.4 Alkalinity as CaO 0. 24 Flake graphite 3.0 Phenthiazine 0.3

The lubricating oil in this grease was a blend of 14.3 per cent of Mid-Continent neutral oil having a viscosity of 100 at 100 F. with 85.7 per cent of solvent treated Texas oil having a hours.

viscosity of 150 at F. the following properties:

Gravity, A. P. I 27.8. Viscosity, S. U. V., 100 F 138.4. Flash, 0C, F 350. Fire, 00, "F 400. Pour, F 0. Hard freezing point, F., Westinghouse Method -1 Below .30. Color, N. P.A 2.0.

The tallow employed in this grease had the following properties:

Gravity, A. P. I 24.2. Melting point, F'.', capillary tube--. 113-116. Flash, 00, F 580.

Pour, F.. +95.- Color, N. P. A 1.5.

Odor Not rancid. Neutralization number 1.26. Iodine number, Mod.'Hanus 37.4. Saponification number 193,

This grease was manufactured by pressure saponification in part of the oil, followed by at-' mospheric evaporation of most of the excess water, and addition of the finishing oil at atmospheric pressure with final adjustment of the water content under vacuum. The initial charge to the kettle was 15.17 parts tallow, 30.34

parts oil and 0.3 part of phenthiazine per 100 parts of finished grease. This charge was heated to to F., with a. slurry of 2.15 parts -Ca(OI-I)"i in 6.4 parts of water. The kettle was then closed and saturated steam was applied until an internal kettle pressure of twenty pounds per square inch had been maintained for three ing steam from the grease as fast as practical without foaming the grease out of the kettle.

Heat was then applied to the jacket of the kettle until the water content of the grease was reduced I to approximately 2 per cent, based on the finished grease. The rest of the oil, amounting to 48.76

parts and preheated to 150 F.-, was then added quickly with agitation and 3 parts of flake graphite were also added. A fifteen inch vacuum was then applied to the grease, and thorough agitation under this vacuumwas continued until the water content was satisfactory; This required about two. hours. The grease was then drawn from the kettle and found to have the following properties:

Gravity: A. P. I 22.7. Specific gravity, 60/60 F 0.918. Melting point, F., Hawhurst 184. Flow point, F.:

Method 58, Gulf 218. Westinghouse Above 165.

Penetration, A. S. T. M. D 217-33 T,

I 0 F., 150 g., 5 sec.:

Unworked 162. Worked 162, 77 F., 150 g., 5 sec.:

Unworked 265. Worked 290. Ash, percent 1.87. Stability test, grease:

Method 201, Gulf Good. Westinghouse Method Good. Texture Smooth.

Soap by analysis, percent by weight- 14.2. Hard freezing point, F., Westinghouse Method Below -50, Filler; None.

The blended oil had The pressure was then released by bleed- In a modification of this procedure, saponification in a substantially equal weight of oil was effected under pressures of to 55 pounds per square inch, which required one to two hours. The soap was drawn from the pressure kettle into an open mixer maintained at about 250 to 300 F., so that excess water was flashed off almost instantly, in the form of steam, during the transfer. The water content was adjusted by further heating and the finishing oil and graphite were then worked in under vacuum, as previously described.

My invention is not limited to the specific prov cedures described in the above examples, but these examples illustrate some typical instances in grease manufacture in which thorough agitation under vacuum, usually with maintenance of a controlled range of temperatures, is a highly advantageous expedient, especially in finishing the grease. Numerous other procedures involving this step are within the scope of this invention.

In making'greases by the improved methods of this invention, any kettle provided with adequate means for agitating, evacuating, and controlling temperature may be employed. However, it is advantageous in making grease by these methods to employ a kettle of such design that the most effective application of the vacuum treatment and other features of this invention can be made. This end is best attained by the use of a kettle of the special design described hereinabove, which constitutes a part of this invention.

In this connection, it should be noted that the requirements to be met in the manufacture of greases of high quality at a reasonable cost are difficult, and in a sense unique. High temperatures, and temperatures over a considerable range, must be employed; and it is desirable that these temperatures be kept reasonably uniform throughout a relatively large quantity of grease, or grease constituents, during the various stages of processing. However, these materials are often heavy and stiff, even at high temperatures. Convection therefore cannot be relied on to keep the temperature uniform, and heat transfer by thermal conduction is not good. But it is generally necessary to apply heat only to the walls of the vessel in which the processing is done. Thorough agitation and circulation of the processed' materials are therefore required for the sake of uniformity of thermal treatment, as well as for uniformity in blending.

In accordance with the present invention, these conditions and requirement are advantageously met by establishing and maintaining a tall narrow cylindrical charge of grease (or grease constituents) in a hot walled vessel or kettle, the diameter of the kettle being rather small in proportion to its height. Advantageously, the complete charge in the-kettle has a height or depth which is several times as great as its diameter; at least 1.5 times as great. In this charge of grease I establish circulation or movement in opposite directions by means of compound agitators. Advantageously there is an upward movement of the core of the body, effected by means of an axial ribbon conveyor which tends to cut out the core,

or center of the charge and to lift it up to the surface of the charge. On the periphery, where the heat is applied, I establish a disturbed downward flow, advantageously by rotating inclined vanes or blades provided with means for scraping the kettle wall. This prevents local overheating drawings.

of portions of the charge, and insures the maintenance of substantially uniform temperatures throughout, while effecting the desired thorough blending of the constituents in a relatively short time.

I have found that the described agitation and circulation are readily maintained while operating at normal or elevated pressures or under any desired vacuum, in a kettle of the type previously described and illustrated in the accompanying It will now be readily understood that the process and apparatus described hereinabove are useful and efiicient in substantially all greasemaking operations. They are adapted for saponification at any desired pressures. In most grease-making procedures, it is advantageous to conduct the saponification in the presence of a part of the oil to produce a soap concentrate. This is readily accomplished in my kettle, and forms a part of the procedures of some of the specific examples hereinabove.

After saponification, or the preparation of a soap concentrate in the kettle, it is necessary to blend the soap or soap concentrate with oil to form the finished grease. This blending must be especially thorough, as previously noted, in order to obtain a satisfactorily uniform product. The compound agitators included in my kettle, operating in a relatively tall column of grease or grease constituents, are more eificient in producing a uniform blending than any means for this purpose heretofore available. blending and agitation may be readily effected under any desired vacuum in accordance with my inventions. This is highly advantageous. Violent agitation tends to trap air or other gases and vapors in the grease mixture, especially during the later stages of the' process, when the temperature of the grease is ordinarily reduced prior to filling or drawing. When operating under a suitable vacuum, however, substantially no air, or other gas or vapor, is entrapped, there being much less gas or vapor present. In fact, when operating in accordance with this invention it is possible to remove gas and volatiles previously included in the grease mixture. For example, water may be removed in this manner to obtain the desired final moisture content, and this often results in a substantial saving in operating costs, in addition to producing a grease of improved properties.

-When operating in accordance with this invention, a stable homogeneous grease'having a uniform continuous gel structure free from occluded air and other undesirable gases is very readily obtained.

While my invention has been described with special reference to certain embodiments and features thereof which are now considered most desirable, it is to be understood that the invention is not limited thereto, but may be variously embodied and practiced within the scope of the appended claims.

What I claim is:

1. The improved process of manufacturing lubricating grease free from occluded gases, which comprises establishing a vertically elongated charge of grease constituents including a soap and a lubricating oil, applying heat peripherally to said charge, thoroughly agitating said charge to blend the said constituents, and maintaining the charge under a substantial vacuum during the agitation thereof, the vacuum being suflicient to prevent the trapping and occluding of gases And this eificient and the thorough agitation comprising a positive downward, turbulent flow of the peripheral 'portion of the charge, the peripherally heated material being continuously admixed with the downwardly flowing peripheral portion by such turbulent flow, and a positive upward, turbulent flow of the core of said charge, the said upward and downward flows being in direct, contact at their;

and cooling said vessel and the contents thereof,

means for thoroughly agitating a charge in the vessel, said agitating means including an inner helical ribbon agitator and a concentric outer paddle agitator'provide'd with scrappers posi-.

tioned to contact the said inner surface of the vessel, means for rotating said agitators concentrically. and in opposite directions, means for maintaining the desired absolute pressure in the vessel, and means for withdrawing finished grease from said vessel. g

3. Apparatus for manufacturing lubricating grease, comprising in combination a vertically elongated kettle, means for applying heat peripherally to said kettle, an agitator mounted within said kettle, a pressure-tight closure for the top of the kettle, means for maintaining a vacuum within the kettle when closed, means for operating said agitator with the kettle maintained under vacuum, means for withdrawing contents from the bottom of the kettle, and means for charging the kettle through the said closure, said agitator being a compound agitator comprising an inner helicoid ribbon adapted to impart an upward flow to the central portion of the contents of the kettle and an external agitator having a plurality of vanes adapted to impart a downward flow to the peripheral portion of the said contents, said vanes being provided with terminal scrapers adapted to free the walls of the kettle from adhering deposits.

4. As an improved agitator for grease kettles and the like, a compound agitator comprising an inner helicoid ribbon adapted to impart an upward flow tothe central portion of the contents of the kettle and an external agitator having a plurality of vanes adapted to impart a downflow to the peripheral portion of said contents, the said vanes being provided with terminal'scrapers adapted to free the walls of the kettle from adhering deposits.

5. As an improvement in making stable,

homogeneous lubricating greases having a uniform gel structure, the improvement which comprises continuously circulating a grease mixture containing a soap and lubricating oil, while maintaining said mixture in the form of a vertically elongated, cylindrical column,'by flowing the core and peripheral portion of said mixture in opposite directions with the core and peripheral portion in direct contact to produce turbulent flow at their interface, the core having a positive upfiow and the peripheral portion having a positive downflow and both flows having a helical component and being turbulent, such 6. The improved process of claim 5 wherein the grease mixture is peripherally heated and the heated portion is continuously intermixed with the downfiowing peripheral portion and this admixture is recycled, the said circulation being continued until the grease mixture is brought to a substantially uniform temperature throughout saitc:I column by said turbulent flow in a helical pa 7. The improved process of claim 5 wherein the grease is peripherallycooled and the cooled portion is continuously intermixed with the downflowing peripheral portion and this admixture is recycled, the said circulation 'being continued until the grease is brought to a substantially uniform temperature throughout said column by such turbulent flow in a helical path.

8. The improved process of claim 5 wherein a substantial vacuum is maintained over the top 01' said column of grease during said circulation, the

applied vacuum being suflicient to preventthe occlusion of air and other gases in the so-circulated grease.

9. The improved process of claim 5 wherein the soap is formed in situ in the oil under increased pressure, while continuously circulating the mixture, and wherein the pressure is subsequently released while continuing said circulation of the grease mixture.

10. As an improvement in the manufacture of lubricating greases by methods in which the grease constituents are agitated during compounding, blending, extending and finishing, the improvement which comprises thoroughly agitating the grease mixture under vacuum during at least one of the said operations, the agitated grease mixture beingcontinuously circulated and exposed to .a vacuum equivalent to a subatmospheric pressure of at least five inches of mercury below atmospheric pressure and the agitation and vacuum being so adjusted relative to each other as to produce a final grease substantially free of occluded gas and vapors.

11. An improved apparatus for manufacturing stable homogeneous lubricating greases, comprise ing a vertically elongated kettle, a pressure-tight closure for the top of the kettle, means for charging the kettle, means for' maintaining a vacuum within the kettle when closed, an agitator mounted within said kettle and means for operating said agitator with the kettle maintained under vacuum, said agitator being a compound agitator comprising an inner helicoid ribbon and an external agitator having scrapers contacting the inner walls-of the kettle, said inner and outer agitators being concentric and capable of rotatmg in opposite directions to cause a positive upward flow of the central portion and a positive downflow of the peripheral portion of the con-' tents of the kettle, with the said upward and downward flows in direct contact at their interface, and means for withdrawing the grease from the bottom of the kettle.

12. In an apparatus for manufacturing lubrieating greases, an improved compound agitator comprising an outer agitator and an inner agitator mounted concentrically about a common vertical axis and capable of being rotated in opposite directions about said common axis and means for so rotating said outer and inner agitators in opposite directions, the outer agitator being a paddle agitator comprising a rectangular frame and having a plurality of inclined paddles circulation being continued until a grease having 7 a uniform gel structure is obtained.

mounted in staggered arrangement on the opposite vertical sides thereof, said paddles extending outwardly from said frame and being free at the a helicoidal agitator comprising a helicoid ribbon mounted on and spaced from a rotatable shaft,

. the said helicoidal agitator being rotatably mounted within said frame.

13. In an apparatus for manufacturing lubri-' cating greases, an improved compound agitator comprising an inner helical ribbon agitator and a concentric outer paddle agitator provided with outer end thereof. and the inner agitator being prising a helicoid ribbon mounted on and spaced from a rotatable shaft and said outer agitator comprising a plurality of inclined vanes mounted on opposite sides of an agitator frame in staggered arrangement and extending outwardly from said frame, said frame being rotatably mounted on the shaft of said inner agitator and surrounding said inner helicoid ribbon, the vanes of said outer agitator being so inclined as to force the peripheral portion. of the grease downward when the outer agitator is rotated. v

15. As an improved agitator for grease kettles and the like, a compound agitator comprising an inner helical ribbon agitator and a concentric outer paddle agitator provided with scrapers positioned to contact the said inner surface of the kettle, said inner and outer agitators being concentrically mounted in the kettle and being capavble of rotating in opposite directions, the paddles of said outer agitator being so inclined as to force the peripheral portion of the grease downward when the agitator is rotated in the kettle.

16. The process of manufacturing improved lubricating greases free of occluded gas, comprising heating together grease constituents including a lubricating oil and a soap, and thoroughly blending the constituents by agitation under a substantial vacuum'until a stable homogeneous grease is obtained, the charge of-said grease constituents being subjected to a vigorous and thorough agitation comprising a positive upfiow of the core of said charge and a positive downfiow of the peripheral portion thereof, the said upfiow and downflow being in direct contact at the interface of said core and peripheral portion with turbulent flow and intermixing at said interface and the applied vacuum being sufiicient to prevent the trapping and occluding of gas, the said heating, agitation andvacuum being so adjusted and correlated as to produce a stable homogeneous grease having a uniform continuous gel structure free from occluded gas.

17. An improved apparatus for manufacturing lubricating grease, comprising in combination a vertically elongated kettle, means for applying heat peripherally to said kettle, an agitator mounted within said kettle, a pressure-tight closure for the top of the kettle, means for maintaining a vacuum within the kettle when closed, means for operating said agitator with the kettle maintained under vacuum, means for withdrawing the contents from the bottom of the kettle,

closure, said agitator being a compound agitator comprising an inner element and an outer element adapted to cause a positive upfiow of the central portion of the contents of the kettle and a positive downfiow of the peripheral portions of said contents with the said upward flow and downward flow in direct contact at their interface, the said outer element being a paddle agitator carrying scrapers adapted to free the walls of the kettle from adhering deposits and said inner element being a helicoid ribbon agitator, said inner and outer elements being centrally mounted within the kettle on concentric shafts driven by a single power source external to the kettle.

18. The process of manufacturing improved lubricating greases free of occluded gas comprising heating together grease constituents including a lubricating oil and a soap and thoroughly blending the constituents by agitation in a kettle clos'ed to the atmosphere under a substantial vacuum until a stable homogeneous grease is obtained, the agitated grease mixture being continuously circulated and exposed to said vacuum, said agitation beingv such as to blend the grease constituents into a homogeneous gel structure and the applied vacuum being equivalent to at least five inches of mercury below atmospheric pressure and being suillcient to prevent the trapping and occluding of gas, the heating, agitation and vacuum being so adjusted and correlated as to produce a stable homogeneous grease having a uniform continuous gel structure free of occluded gas.

19. The process of claim 18,- wherein said grease constituents are established in the form of a vertically elongated body of relatively small diameter and maintained in such form during the heating and agitation under said vacuum.

20. The process of claim 18, wherein said agitation under substantial vacuum is continued while the temperature of the grease is reduced to the drawing temperature.

21. The process of claim 18, wherein the said grease is a hard grease suitable for use as a locomotive driving journal compound, said hard grease comprising a uniform mixture of mineral lubricating oil,.sodium soap and petroleum wax,

' mounted within said kettle, a pressure-tight cloand means for charging the kettle through said sure for the top of the kettle, means for maintaining a vacuum within the kettle when closed, means for operating the agitator with the kettle maintained under vacuum, means for withdrawing contents from the bottom of the kettle, and means for charging the kettle through said closure, the said agitator being a compound agitator adapted to cause a positive upward flow of the central portion of the contents of the kettle and a positive downward flow of the peripheral 'portion of said contents, with the said upward flowinterface.

25. The process of manufacturing lubricating grease, which comprises establishing and maintaining a vertically elongated charge of grease constituents including a soap and a lubricating oil, agitating said charge by continuously raising the core thereof to the top of the charge and causing a positive downward flow of the peripheral portionof-the charge around said core, and maintainingthe charge under a substantial vacuum during said agitation,'the said downflow being in direct contact with said core, producing turbulent flow and intermixing at the interface of said core and peripheral portion, and said vacuum being sufficient to prevent trapping and occluding of air during such agitation and flow.

26. The process of claim 25, wherein said soap is formed by. saponifi'cation 'under pressure in the presence of apart of the said lubricating oil and the pressure is rapidly released after saponification is complete to remove most of the water and wherein the partially dehydrated soap concentrate so obtained is admixed with the remainder of said lubricating oil to form said 'charge, the soap concentrate and added lubricating oil being blended into a stable homogeneous grease by said agitation and circulation under a substantial vacuum.

27. The process of claim 25 wherein said charge is heated to facilitate blending, and then cooled while said agitation is continued under said vacuum.

28. In the manufacture of improved lubricating greases substantially free of occluded gases and vapors, the improvement'which comprises agitating a grease mixture including a lubricating oil and a soap in a kettle closed to the atmos phere under a vacuum suflicient to prevent the trapping and occluding of gases and vapors during the agitation, the agitated grease mixture being continuously circulated and exposed to a .justed relative to each other as to produce a grease having a uniform continuous'gel structure .free from occluded air and other undesirable gases and'vapors.

HERSCHEL G. SMITH.