US2339873A

US2339873A - Grease preparation

Info

Publication number: US2339873A
Application number: US470162A
Authority: US
Inventors: Arnold J Morway; John C Zimmer
Original assignee: Standard Oil Development Co
Current assignee: Standard Oil Development Co
Priority date: 1942-12-26
Filing date: 1942-12-26
Publication date: 1944-01-25
Anticipated expiration: 1961-01-25

Description

Jan. 25, 1944. A, J. MORWAY ETAL 2,339,873

GREASE PREPARATION Filed Dec. 26. 1942 2 Sheets-Sheet 1 HEA T/IVC KETTLE SCREW SCRAPfiR FIG-J .2 BJ en/wavy Patented Jan. 25, 1944 Arnold J. Morway,

County, and John C.

Clark Township. we. Zimmer,

Union, N. 8., al-

signors to Standard Oil Development Company, a corporation-of Delaware Application December as, 1942, Serial no. 470,162

16 Claims.

This invention relates to the process for preparing lubricating greases and also to the products themselves, especially adapted to withstand advantageously service conditions of local high temperatures coupled with sudden and irregular shock load effects often exerted in muddy or water-drenching environment. The invention relates particularly to greas compositions containing aluminum stearate as the main soap ingredient.

The many and varied type advances that have been made in the mechanical art in recent times have placed an onus upon the lubricating art. For mechanical systems operating under high pressures, low speeds and oftentimes. as in commercial tractors and Army tanks, in a muddy or water-drenching environment. only grease compositions are suitable as lubricants for the slow-moving parts. In this field of lubrication, however, it is generally recognized thatmany compositions are employed simply because they are the best available and not for the reasons of any particular adaptability. Moreover, as mechanical improvements are being made. it is bein recognized more clearly that the making and using of grease compositions present a. very highly specialized field of lubrication, and that for development of the art, it is necessary to'have available definite information as to both' the blending characteristics of the various constituents in the grease composition and to the service conditions under which the composition is to be employed.

Thus, a composition to be suitable as a lubricant for the slow-moving parts of modern Army tanks and commercial tractors must have many unusual characteristics. Among such unusual characteristics are that of being markedly tacky and adhesive in nature; of having the capacity to withstand severe load and shock operations. even when the parts aresubmerged in a muddy or water-drenching environment; and of capacity of being sumciently mobile to be handled and dispensed at normal atmospheric temperatures from greas gun equipment; and of consistency to be able to flow under its own weight, but yet not fluid enough to leak out or be splattered from the machinery parts under operating conditions. Furthermore, a suitable lubricating greasefor such type of machinery is that the composition must preferentially wet metallic surfaces, even when heated or submerged in water and maintain under these conditions a. persistently heavy film of lubricating properties which will also act as a seal against the entrance of water and dirt ll idly cooled to a temperature of about 150 F. V

to the bearing parts under operating conditions.

Criteria of quality of grease compositions are specific ranges in value of consistency as indicated by the work penetration test (A.- S. T. M. D217, 3ST), the 25 gram cone penetration test (similar to the A. S. T. M. except that in the A. S. T. M. test the cone weighs grams), the B. I. L. Mobilometer (Ind. Eng. Chem. An. Ed. May 15, 1940. pa es 285-7), of body density, of adhesiveness to metallic surfaces, or internal cohesion and of melting points. These characteristics depend upon the physical and chemical relationships of the ingredients in the composite and the reaction of the composite to the effects of speed, pressure and heat during service. In many commercial greases, a relationship between the various constituents is desirably attained so that a composite is formed consisting of a minor portion of a, colloidal dispersion of metal soaps in a relatively stable emulsion of a major portion of a colloidal dispersion of other and difierent type metal soaps in a mineral oil of suitable consistenpy. It is considered particularly important that the colloidal phase be relatively stable and form a satisfactorily adhesive lubricating film on the bearing surfaces, and that the colloidal phase offer substantial resistance toward heat conduction from the surface film into the mass so as to minimize the effect of friction, speed and load during service upon the bulk of the grease coinposition. i

The present invention relates to the manufacture of grease compositions containing an aluminum soap of a saturated fatty acid, contain n between about 10 and 24 carbons in the molecule, such as aluminum stearate as the main constituent. The particular feature of the invention is the means afforded for controlling the manufacture of such type greases without the formation of the usual hard, gritty lumps or of the highly fluid type masses sometimes obtained when the rate of cooling is not very carefully controlled. When aluminum stearate, for example, in an amount of about 8% by weight is admixed and heated with a mineral oil and the mass cooled, the'desirable transition in structure of the mass from'being a stringy liquid to a consistency of relatively solid gel does not generallysatisfactorily occur. The cause of such failure has not been clearly established. It would seem, however, from photomicrograph that a recrystallization of the aluminum stearate occurs at a temperature below about 150 F. Thus, if a mineral oil-aluminum stearate mixture is rapor below, the aluminum stearate crystallizes and thereisobtainedamixtureofoilandccarsely dispersed soap granules.

To obviate such a disadvantage in the preparation or greases, cooling from 140' I". to 180 I". in. shallow pans holding between about 50 and 100 lbs.,- havins a depth of several inches was eiiected in prior art processing.

Usually, the cooled mass from this pan cooling,

as it is termed, was then passed to settling equipment, stirred or reworked. as it is commonly termed, to develop a uniform c .product being about 2 to 1. .The amounts in ncy, and then the mass was filtered into the shipping con-v tainingaluminum stearate as theminimum soap ingredient were time and labor consuming, re-

quiredextensive floor space and, due to the reworking required after such cooling, there was also involved a consistency loss based upon the quantity of aluminum stearate employed.

It has now been found that when small quantitles of an aromatic amine, such as phenyl alpha naphthylamine or phenyl beta naphthylamine and the condensation product of an 'aromatic aldehyde, such as salicylic aldehyde, and and aliphatic polyamine, such as ethylene diamine, are incorporated in blended mixtures of aluminum stearate and mineral oil, thecom-j posites in bulk can be cooled rapidly with agitation to temperatures as low as 15' F., and in layers of about V4 of an inch thick to temperatures as low. as 50 F. without granulation or decomposition. These additive compounds are usually added in small quantities to the molten or rubbery aluminum stearate dispersions in oil at the mineral oil aluminum stearate blending temperatures of between 280 F. and 300 F. The use of such additive compounds thus permits the preparation of aluminum special type greases on a large scale continuous basis, and greatly expedites their manufacture. Furthermore, the use of such compounds facilitates the packaging. of the grease directly from the cooling devices into large shipping containers without reworking or pounds, greases may be prepared with the different forms of aluminum stearate, that is, the distearate may be used, or at least a large portion of the aluminum stearate-blended with the oil may be in this form. These advantageous effects are achieved in blended compositions without the development of any disadvantageous effects upon any of the desirable lubricating properties of aluminum soap greases. These advantageous effects 1 are also achieved in aluminum soap type greases without being disadvantageously affected by the presence of accessory adf filtering. Moreover, with these additive com- -ditive materials, such as thickening agents, anticorrosive and anti-oxidation agents.

which these two additive materials are present in the compositions of the invention vary usually between 5 and 30% by weight of the amount of thealuminum soap present in the composition. The aluminmn soap is blended with the mineral oil to form a grease of suitable composition in amounts between 3 and 20%, but usually between about 3 and 10% by weight of the 011. Other compounds may be blended in the grease compositions in order to impart to the composite properties particularly desirable for service requirements.

Aromatic amines as a group have been found to be effective as one of the constituents of the additive material according to the present invention. The selection of a particular aromatic amine for a composition is made largely on-the basis of its vapor pressure and its relative effects upon oil solubility and miscibility with other constituents as'regards effecting the lowering of the transition temperature. It is also 7 amines, especially the hydroxy aromatic amines and the sulfur-bearing compounds are effective.

'Alkylated aromatic amines are notably advantageous. 0f the various aromatic amines effective for the purpose of this invention, particular mention may be made of such compounds as phenyl alpha naphthylamine, and phenyl beta naphthylamine.

The second constitutent of the additive agent, according to the invention, is the product of the condensation of about one molecular proportion of a certain type polyamine with at least two molecular proportions of a reactive type aromatic aldehyde. The suitable polyamines are those having at least two primary amino groups capable of reacting with an aromatic aldehyde to form an arylidene amine. The particular aromatic type aldehydes are those of which no more than one molecular proportion reacts with each primary amino group of the polyamine. The general structural formula of the condensation product may thus be given as in which Ar represents an aromatic ring or an unsaturated nitrogen containing heteroeyclic ring of 5 or 6 carbon atoms, and It represents an aliphatic group having two nitrogen atoms attached directly to diiferent carbon atoms of the same open chain. The. R may also represent a 6 carbon atoms member ring or a nitrogen containing heterocyclic ring, the two nitrogen atoms in the general formula being separately attached directly to adjacent ring carbon atoms or to themost closely positioned ring carbon atoms of differen rings other than the carbon atoms forming part of the linkage between the two rings. Thus, the condensation product is of the type of an arylidene amine or a Schiff base.

Any aromatic aldehyde which i reactive with a polyamine to produce a condensation product of the type represented by the general formula.

may be employed according to the invention, The aromatic aldehydes particularly suitable are assaeva pounds are the unsaturated cyclic aldehydes such as the pyridine and quinoline aldehydes. An aromatic aldehyde of this general class unsubstituted except for allwl and hydroxy groupings is prefer able. The aldehydes may, however, contain as substituents alkoxy, aryloxy, halogen, heterocycllc, amino, cyano, carboxyl and sulfonic groups, as well ashydroxy, alkyl and aryl radicals. Salicylic aldehyde has been found to be a singularly effective compound.

The polyamine may be any aliphatic amine containing at least two primary amino groups attached directly to two different carbon atoms of the same open chain. The amine may contain an aromatic or cyclic group substituted in the chain. In certain cases an alkyl-aryl polyamine is eilective, provided there are at least two primary amino groups attached to different substantially adjacent atoms of the ring or rings either directly or through one or more atoms which are not members of the ring. Such compounds are less advantageous than the wholly aliphatic polyamines. The preferred amines are those consisting of carbon, hydrogen and nitrogen in which at least two primary amino groups are directly attached to adjacent carbon atoms and particularly the diamines.

formfirst a slurry with a small quantity or the oil base material, the aluminum soap and the additive compounds of the invention and then to pass the slurry through an orifice mixer, to which is also supplied the further quantities of oil as are required to prepare the finished grease. The mixture is then passed through a coil heater at a temperature of about 300 F., and then allowed to settle to permit the separation of any occluded gases before passing through a helical screw type cooler. By this means, a grease can be satisfactorily prepared in large quantities on 1 a continuous basis, and the product directly passed to the shipping containers from the cooling equipment.

An illustration of the method of preparing the grease involving the use of the usual type kettle for heating and blending the constituents is a1- forded by the following description which should In preparing 'the grease compositions of thisinvention, the oil employed is preferably derived from a naphthene base crude, as for example oils of the Coastal type. The viscosity of the oil is usually above about 85 seconds Saybolt at 210 F., and preferably from to 200 seconds Saybolt v at 210 F. The aluminum soap of the saturated fatty acid and the special addition agents of this invention are added to the oil at a temperature between about 280 F. and 300 F. The heating may be carried out in a coil type heater or in the usual type kettle. A suitable heating kettle is furnished with mechanical means of agitation, usually paddles having at the outer sweeps close fitting scraper adjustments to pass over its inner surface in order to insure good heat transfer and to obviate the development of surface films. Usually the aluminum soap and the addition agents of the invention are blended with about 10% to 20% of the total quantity of the oil to be used and the mixture worked into a thick non-lumpy paste. This paste is then stirred into the balance of the oil, and heated to a temperature of between 280 F. and 300 F. and held at that temperature until all of the various ingredients are thoroughly incorporated into a smooth homogeneous mass. The mass after heating is then rapidly cooled by passing through cooling equipment to a temperature of about 90 F. The cooling may be eflected by passing the material into shallow pan and then returning the cool grease to mixing equipbe read in conjunction with the drawing as presented in Fig. l.

through line It of steam either under normal or atmospheric pressure as temperatures within the kettle l0 require. Under the conditions of such means of agitation and of a temperature between about 280 F. and about 300 F., sumcient oil of suitable character as a mineral oil base for the preparation of the grease composition is supplied from storage tank It to the kettle l0 through line I1 and admixed with the aluminum soap and additive compounds of the invention supplied through opening it to make a smooth thick paste. Further quantities of oil to make the grease of desired consistency are then supplied through line I1 and the mass agitated until a smooth homo- .geneous composition is obtained.

When the mass in the kettle has become smooth and homogeneous, the mixture is passed from the bottom of the kettle through line l9 to a screw scraper chiller 20. The chiller 20 has an outer jacket 2| through which a cooling medium, usually water, passes in through line 22 and out through line 23. The screw 24 within the chiller is usually operated countercurrently to the direction of the flow of the grease from line I9 and countercurrently to the direction of the cooling fluid in the jacket 2|. The scraper screw is operated by the motor 25 through gears 26 and transmission 21. The cooledgrease passes from the chiller through line 28.

In batch operation the cooled grease is recycled through line 28 to the kettle 10. By such recycling the entire quantity grease composition is brought to about the transition temperature at about the same time. When this temperature within the mass is reached, agitation within the kettle is discontinued and the mass is allowed to settle and to cool further untilthe transition in structure has been satisfactorily eiiected. The gel composition is then removed from the kettle through a T 29 on line I9 and passed to shipping containers.

In continuous operation it is usual to employ a series of kettles similarly equipped to that designated by the numeral I0 and to pass the hot mixture to the chiller in a relatively continuous stream from the various kettles through the T 30 on line II. In this manner of operation the cool-- ing effected in the chiller 2| is more complete .than thatin batchoperation, namely the cooling in the chiller is effected to about the transition temperature. The cooled grease in such operation is passed directly through a T II on line 28 'to the shipping containers wherein settling and further cooling to atmospheric temperature are agents are thoroughly admixed in quantities so as to form a free flowing slurry composition.

The slurry is then passed through line 45 to an orifice mixer 46, to which is also supplied through line 41 the further quantities of oil from the supply 40, to form the grease of the desired composition. The mixture is then passed through line ll and pump II to the coil heater 50 where.- in it is-heated to the necessary compounding temperature which is usually about 300 F. by means of ste m P s through

lines

51 and 52. The hot mixture then passes through line 53 to a surge tank ll wherein any occluded air or gas formed during the heating process is permitted to escape through the vent pipe 55. To the surge tank may also be supplied through line 56 an oil thickening agent, such as a polybutene or latex, from the tank 51. The grease mixture is Example I v Per cent Aluminum stearate 7.0 Phenyl a naphthylamine 1.0

Condensation product of ethylene diamine and salicylic aldehyde (A) 0.5

Lubricating oil of 35 Saybolt viscosity at The lubricating oil of 35 viscosity at 100 F. and the aluminum stearate were charged to a heating kettle, as illustrated in Fig. 1 and the mixture agitated by means of the paddles for about removed from the surge tank 54 through the line 58 and passed to the screw conveyor type 'The grease was prepared according to the general procedure given for the composition of Example I. The finished grease was a smooth,

clear hard gel of 340 A. S. T. ll. worked penetration.

Example III when a blend .of 7% by weight of aluminum stearate was made in 93% of lubricating'oil of 35 Saybolt Universal viscosity at 100 F. and the mass cooled according to the method described in Example I, .the product had a greasy consistency, which, on working, broke up to a material resembling ground glass floating-in oil.

Example The effect of a higher concentration of aluminum stearate in a grease composition is shown by the following grease preparation;

Per cent Aluminum stearate 18.75 Phenyl a naphthylamine 1.00 Condensation product (A) 0.50

Lubricating oil of 400 Saybolt Universal vis- I cosity at 100 F 79.75

The preparation of the grease was made according to the general procedure described in Example I at a temperature between 280 and 300 F. The mass prepared by blending the aluminum stearate in the oil presented processing diiliculties due to its rubbery and tacky character. However, on adding the amine and the condensation product, the composite became more fluid and relatively smooth. On cooling,

smooth, hard, clear homogeneous product was obtained having an A. S. T. M. penetration of 85 and a worked penetration of 179.

minutes, ata temperature of about 280 F. At

this stage, the composite is of rubbery consisttency. The amine and the condensation product were then added andthe temperature maintained at 280 F. Upon the addition of the amine and the condensation product, the consistency changed to that of a fluid mass. At this point, the heating was discontinued. and the mixture cooled by passing cold water through the kettle jacket. The grease was thus cooled with agitation to about 90 F., then agitation discontinued and the mass allowed to stand for about 30 minutes. The grease, after this period of standing, was found to be a very soft semi-fluid product.

' The grease so prepared had an unworked penetration at 77 F. of 310 and a worked penetration at I? F. of 325 using the 25 grams cone penetra- What is claimed is:

1. A process for preparing a lubricating grease which comprises thoroughly mixing at anelevated temperature a viscous hydrocarbon oil, an aluminum soap of a saturated fatty acid containing between about 10 and 24 carbon atoms in the molecule, a small amount of a mixture of an aromatic amine and a condensation product ofthe general formula in which R represents a member of. the group consisting of aromatic rings and unsaturated heterocyclic rings of 5 to 6 carbon atoms in which the hetero atom is nitrogen, and R represents an aliphatic radical having the two N atoms attached directly to different carbon atoms of the same open chain of R, the relative amounts of the aromatic amine and condensation product being in the ratio of 2 to 1.

'2. Processaccording to claim 1-in which the is prepared by the condensation of a mono-nuclear aromatic aldehyde and an aliphatic dition, or an S. I. L. Mobilometer reading of 589. II amine.

4. Process for preparing aluminum soap greases which comprises thorough mixing at an elevated temperature a viscous mineral lubricating oil, about 3% to 8% of aluminum stearate and from about 0.15% to 3% of a mixture of an aromatic amine and a compound of formula in which R represents a member of the group consisting of aromatic rings and unsaturated heterocyclic rings of to 6 carbon atoms in which the hetero atom is nitrogen, the OH radical being attached directly to a carbon atom ortho to the CH=N group and R represents an allphatic radical having the two N atoms attached directly to difierent carbonatoms of the same open chain of R, the relative amounts of the aromaticamine and condensation product being in the ratio of 2 to 1, rapidly cooling the heated mixture to a temperature below 140 F. and allowing the mass to cool.

5. Process according to claim 4 in which the aromatic amine is a naphthylamine. 6. Process according to claim 4 in product of formula is the condensation product of a mono-nuclear aromatic aldehyde and an aliphatic diamine.

7. Process according to claim 4 in which the thorough mixing at an elevated temperature is effected by passing the ingredients first through an orifice mixture and then through a coil heater. r

8. Process for preparing aluminum soap greases which comprises thoroughly mixing at an elevated temperature a viscous mineral lubricating oil, about 3% to 8% of aluminum stearwhich the -ate and from 0.115% to 3% of a mixture of an aromatic amine and a condensation product of formula in which R represents a member of the group consisting of aromatic rings and unsaturated heterocyclic rings of 5 to 6 carbon atoms in which the hetero atom is nitrogen, the OH radical being attached directly to a carbon atom ortho to the CH=N- group and R. represents an aliphatic radical having the two N atoms attached directly to difierent carbon atoms of the same open chain of R, the relative amounts of the aromatic amine and condensation product being in the ratio of 2 to 1, rapidly cooling the heated mixture to a temperature below 140 F. in a flowing stream and allowing the cool mass to stand.

9. Process for preparing aluminum soap grease according to claim 8 in which the rapid cooling is eflfected by passing through a helical screw scraper type cooling equipment in which the flow of the heated mixture is in the opposite direction to that of the motion of the screw and countercurr'ent to the flow of the fluid in the cooling Jacket mixture ofan aromatic amine and a compound in which R represents a member of the group consisting of aromatic rings and unsaturated heterocyclic rings of 5 to 6 carbon atoms in which the hetero atom is nitrogen, the OH radical being attached directly to a carbon atom ortho to the CH=N- group and R represents an aliphatic radical having the two N atoms attached directly to different carbon atoms of the same open chain of R, the relative amounts of the aromatic amine and condensation product being in the ratio of 2 to 1, rapidly cooling the heated mixture in a flowing stream to a temperature below about F. and then allowing the mixture to stand.

12. A semi-fluid lubricating grease comprising a viscous mineral lubricating oil, about 3% to 8% of an aluminum soap of a saturated fatty acid containing between 10 and 20 carbon atoms in the molecule and a small quantity of a mixture of an aromatic amine and a condensation product of an aromatic alkyl and an aliphatic diamine of formulain which Ar represents an aromatic ring, the OH group being attached directly to a ring carbon atom in an ortho position to the -,CH=N-- group and R represents an aliphatic radical having the two nitrogen atomsattached directly to difierent carbon atoms of the same open chain of R, the ratio of the aromatic amine tothe condensation product being 2 to 1, the whole being worked into a homogeneous mass.

13. A semi-fluid grease according to claim 12,

in which the aluminum soap of the saturated fatty acid containing between 10- and 20 carbon ARNOLD J. MORWAY. JOHN C.