US1966821A - Grease and its manufacture - Google Patents

Description

UNITED STATES PATENT orFicr.

GREASE AND ITS MANUFACTURE Gus Kaufman, Beacon, N. Y., assignor to The Texas Company, New York, N. Y., a corporation of Delaware No Drawing. Application August 15, 1931 Serial No. 557,385

4 Claims. (Cl. 879) This application is a continuation-in-part of eral oil and fat or fatty acid are not only heated my copending application filed July 1, 1930, together to a high temperature but they are Serial No. 465,144. V maintained at a high temperature for a sub- 5 This invention comprises a method of heat stantial period during which the aforementioned treating oils used in the preparation of lubricatincr'easein viscosity occurs. In the light of the ing greases, and particularly heat treating a mixprior art method this heating may be said to be ture of a mineral oil and a soap forming mateneedlessly" prolonged.

rial, such as a fatty oil, fatty acid and the like. The physical and chemical properties of The invention also has reference to the prepagreases made according to the methods of the ration of lubricating greases having a hardness prior art are largely dependent upon the nature or penetration especially adapting them for use of the ingredients used in their preparation. as lubricants for driving journals of locomotives Thus it has been customary, for example, to conand having a relatively low soap content and trol the hardness of gre by varying th 8091p relatively high mineral oil content. content, the hardness of the grease as common- Broadly, my invention contemplates the prep- :7 p p usually being roughly directly D Y aration of grease or lubricating compositions portional to its soap content.

composedmainly'of hydrocarbon oil and a soap Ev n wh n V ry h h m l in P n 1 high prepared and combined in such a manner that titer fats are employed in the preparation of a the physical properties of the resulting grease, h grease y the Prior art methods, the D such as melting point and hardness, may be content of the resulting product may very greatly 7 varied to a considerable extent substantially inexceed that o my product avin he sa ha ddependently of the soap content. ness and prepared from lower melting point fats. The invention contemplates an improved By fo wi e method of y invention method of manufacture of grease compositions imp ved ea s Produced, Certain of the 25 wherein the hydrocarbon oil and fatty oil incharacteristics of which may be varied at will, gredients are preliminarily heated, preferably in but generally speaking one'which has a melting admixture, under various conditions of temperapoint appreciably lower than that of grease of ture or during various periods of time at various corresponding hardness manufactured by contemperatures in order to effect a digestion or ventional methods of practice from substantially 30 conversion. The extent of this conversion may similar type ingredients. Greases made by emconveniently be controlled by regulating the inploying my invention may contain materially crease in viscosity to a predetermined point. lower proportions of soap than greases prepared When the desired extent of conversion has been by the prior art methods. In other words, if it efiected, alkaline material is added to react with is desired to produce a grease having a certain 30 the saponifiable constituents of the digested oil consistency or hardness the soap content necesmixture to form a final product of desired physisary to attain such consistency or hardness may cal and chemical characteristics. be reduced to any desired extent up to 30 to 50% It has been common in the prior grease making less soap, and in some instances considerably art to heat the mineral oil or hydrocarbon and greater reduction by the use of my invention.

40 fat or fatty acid together to the desired tem- As a consequence of this the resultant grease perature for carrying out saponification, which will contain a larger proportion of hydrocarbon might have been in some instances as high as or lubricating oil, thus tending not only to very 400 to 500 F. The aqueous solution of saponimaterially increase the lubricating qualities but fying agent was then added without further also to greatly reduce the cost, inasmuch as a 45 delay insuch regulated quantities that the water portion of the more expensive soap ingredient would be flashed ofi continuously, thus avoiding will have been replaced by the less expensive the possibilities of boil-overs due to excessive mineral oil ingredient. foaming. The time of manufacture of a batch Likewise it has been found that lower viscosity was also materially reduced by this method. lubricating oils may partially or wholly replace 50 According to the present invention the minhigher viscosity lubricating oilsinthe preparation of greases by my method, while attaining the same consistency or hardness as when using the more viscous oils. By the substitution of lower viscosity oils for higher viscosity oils while maintaining a given consistency or hardness, considerable advantages have been experienced in reducing the frictional resistance on account of the presence of the lower viscosity lubricating oil.

Notably in the case of greases employed in the lubrication of driving journals of locomotives, it is necessary generally to provide a grease which is very hard as compared with greases employed on other types of machinery. Such locomotive driving journal lubricants manufactured by the methods of the prior art commonly contain between 40% and 50% of the sodium soap of a high melting point fatty acid, or equivalent fat, this high percentage of soap having been found necessary to attain the desired hardness in the finished grease. Theseprior art driving journal lubricants commonly have a high melting point of about 450 F. On the other hand, a similarly hard grease for driving journal lubrication may be prepared according to my invention from similar ingredients with a soap content lower than 40%, and which soap content may vary even to as low as 20 to 25%. The grease prepared according to this invention may therefore contain a correspondingly larger proportion of mineral oil and may on this account have very superior lubricating qualities.

Such a low soap content and relatively high oil content grease has been found to be especially adapted to the very severe conditions present in locomotive driving journal lubrication. Furthermore, such grease may have a melting point of 350 to 400 F., which is considerably lower than that of the prior art greases, as pointed out above.

The relatively low melting point is believed to be a distinct advantage in the lubrication of locomotive driving journals, since the grease tends to soften and feed onto the bearing surface at a lower bearing temperature, and generally tends to maintain the journal at a lower operating temperature than is the case with the usual driving journal grease.

So far as I am aware, the commercial driving journal compounds of the prior art have been prepared solely with cylinder oils or cylinder stock "as the mineral oil constituent. Heretofore it has been deemed necessary to use a heavy mineral oil of that character to furnish the proper lubrication for such heavy duty journals, and also to atgreases, having desired lubricating and other physical properties, which may be composed of mineral and fatty oil or fatty acid ingredients of varying nature and physical characteristics and wherein the physical properties of the final product, particularly its consistency or hardness, may substantially be controlled irrespective of either its soap content or of the particular type of mineral or fatty oil used in its preparation. The petroleum or hydrocarbon lubricating oil constituents may be of the nature of a cylinder oil or cylinder stock and may embrace either a distillate or a residual product derived from either paraffin or naphthene base, or mixed paraffin and naphthene base crudes, or, on the other hand, may be of the nature of a pale oil or a fraction of lower boiling range than cylinder oil though derived from any of the foregoing crude sources. The fatty oil or fatty acid may be derived from either animal or vegetable origin, such as hard tallow, tallow oil, fleshing grease, stearin, elaine oil, castor oil, cottonseed oil, residual pitchy material resulting from the destructive distillation of fatty oils and fatty acids, and the like, and may also embrace hydrogenated fats.

The general procedure followed in preparing lubricating compositions in accordance with my invention is as follows: The hydrocarbon or mineral lubricating oil and fatty oil ingredients are mixed in suitable proportion, depending upon the quantity of these ingredients desired in the final product and are heated to a desired digestion or conversion temperature. During this heat treatment the oils are preferably continuously stirred. This temperature of treatment may range from approximately the melting point of the resulting grease, as for example 400 F., or even lower, to upwards of 600 F. The heated mixture .of oils is then maintained substantially constant at the desired temperature for a predetermined period of time or until the mixture attains a desired degree of digestion or conversion, preferably determined by a progressive increase in the viscosity of the admixture. The digested mixture is then saponified in the usual manner by addition thereto of a suitable alkaline material such as caustic soda, lime, or the like, either with or without prior cooling of the digested mixture.

Although it is usually preferable to subject the petroleum and fatty oil ingredients to heat treatment after mixing, it is contemplated that these ingredients may be separately subjected to heating or digestion with subsequent mixing while in tain the desired hardness of the driving journal ,a heated state prior to saponi fication for the progrease. However, I am enabled by my invention to produce a locomotive driving journal lubricant of the usual hardness, characterized not only by the fact that the soap content may be exceptionally low, as pointed out above, but also by the fact that lower viscosity mineral oils, or at least a blend of cylinder stock and substantial amounts of lower viscosity oils, may be used. This may account in whole or in part for the fact that lower bearing temperatures obtain in the use of driving journal greases prepared according to my invention, perhaps because of the lower frictional resistance of the lower viscosity mineral oils compared with cylinder stock. Inany event, it has .been the experience in large scale practical use of such greases that they develop appreciably lower journal temperatures, and the lubrication furnished is uniformly superior to that of the prior art greases.

Broadly speaking, the preparation of my invention contemplates lubricating compositions or duction of certain lubricating compositions.

While the exact nature of the'physical and chemical changes occurring during digestion of the mixture has not been determined, apparently certain new compounds or products of reaction are formed which impart desirable qualities, especially that of hardness, to the resulting final product and which may be formed as the result of reaction during digestion or conversion, between the mineral and fatty oil, between constituents thereof, or between compounds or products formed as a result of conversion or partial decomposition of the fatty and mineral oils dur ing the heat treatment or as the result of a combination of such reactions. These reactions may result in part at least from oxidation of the hot mixture resulting from the contact of the atmosphere with the surface of the mixture, or the mechanical stirring into the mixture of some of the air over it. This theory is strengthened by reason of the fact that it has been found that the desired increase in viscosity, and resulting increase in the hardness of the final grease, is hastened somewhat by the introduction of air into the mixture.

These reactions are usually accompanied by corresponding and progressive changes in the physical characteristics of the mixture during digestion, such as discoloration and increasing viscosity, so that the duration of heat treatment may readily be controlled by observation of these progressive physical changes and is preferably determined by the change in viscosity of the digesting mixture.

The oil mixture is preferably heated to the desired digestion or reaction temperature as rapidly as possible in a conventional type grease kettle, after which it may be maintained substantially constant at the desired temperature by controlling the rate -of firing the furnace until the mixture has attained a predetermined viscosity. It is desirable to efiect more or less constant agitation of the mixture. Thus-the mixture may be raised to a relatively low temperature, for example from 400 F. to 480 F., and be maintained at substantially this temperature for a relatively long period of time, while on the other hand the oil may be heated to a relatively higher temperature, ranging from 500 F. to 700 F. or even higher, at which temperature it may be maintained for a relatively short period of time in order to bring about the desired degree of conversion.

When heating or digestion is completed, saponification may be brought about by the addition of caustic soda or other suitable soap forming chemicals to the digested or reacted mixture, preferably without prior cooling of the mixture. On the other hand, cooling may be desirable prior to the addition of the alkaline or basic material depending upon the temperature of the heat reacted mixture, in order to prevent excessive foaming or trothing during its addition.

The saponifying agent is preferably added very slowly with continued agitation of the contents 0! the kettle by the paddles in order to avoid excessive frothing or foaming.

h Upon completion of saponification the resulting grease preferably is drawn in a molten condition into suitable containers to cool. However, removal of the finished grease from the kettle in a solid or semi-solid condition, as common in the prior art, is not precluded. Likewise the molten grease may be flbred by suitable stirring during the initial cooling stages if desired.

The following specific examples are given solely for the purpose of illustrating my invention and it is to be understood that I do notmtend to limit the invention to the particular proportions, ingredients, or operating conditions recited.

In these specific examples the penetration or hardness of the resulting grease is expressed in each instance in terms of tenths of a millimeter penetration of an average sample as determined by the standard A. S. T. M. penetrometer and method for greases, and also with the same apparatus modified to the extent of having an extra weight of 475 grams placed within the penetrometer cone. Such latter reading will be termed "Penetration (Modified ASTM). This modified penetration test has been used on samples of relatively hard products to penetrate more deeply and give a higher and perhaps more accurate reading than that obtained with the same apparatus without the added weight.

A description of the A. S. T. M. penetration test may be found in reports of A. S. T. M. Committee D2 on Petroleum Products and Lubricants and Methods-0f Test Relating to Petroleum Products, under the heading Tentative Method of Test for Penetration of Greases and Petrolatum, test D2l727--T. 8U

Examples 1, 2 and 3 Ingredients 1 2 3 Cylinder stock (seca viscosity Seybolt at 210 F.) 151 163 220 (Distillate) (Cyl. stock.) Per cent 37. 37 39. 78 59. 20 Paraffin distillate (372 secs. viscosity 9 Saybolt at F.) per cent 22.90 24. 36 Hard tallow per cent 29. 20 26. 10 88 Stearic acid per wnt 3. 25 2. 90 Flake caustic (98% NaOH) per cent 3. 64 3.43 4. 46 Water, per cent 3. 64 3. 43 4. 46

Time of heating oil and [at mixture 91;

lore saponification Hrs. required to beat to 485 F 5 5 2 Hrs. maintained at 485 F 7 11 14 Viscosity of mixture (secs. Saybolt at 210 F.)

Belore heating 70 73 After heating 104 111 155 Saponiiication with caustic soda solution (49% NaOH) consisting of flake caustic and water Hrs. required to add solution 4% 5% 5% Analysis of the dual product-por cent. by weight Free alkali 0. 28 Water None. 1117 Soda soap"--- 30. 60 Mineral 0' 62. 54 Free fatty acid (Oleic) 0. 14 Free neutral lat None. Undetermined material 6. 44

Physical properties of final product Melting point F 370 376 368 Penetration (ASTM method) 33 29 30 Penetration (modified ASTM) 81 75 15 These three examples resultedin relatively hard greases adapted primarily for the lubrication of locomotive driving journals. In Examples 1 and 2 the mineral oil consisted of cylinder stock and a paraflln distillate commonly known in the industry as heavy red paraflln, the calculated viscosities of the mixed oils being about 90 and 93 seconds, respectively, Saybolt at 210 F. These were heated in admixture with the tallow and stearic acid in the desired proportions to a temperature of about 485 F., and in Example 1 this temperature was maintained for about seven hours while in Example 2 the mixture was maintained at such temperature for a period of about 1 10 eleven hours. These mixtures when neutralized as nearly as practicable produced greases having nearly the same penetration, Example 2 being slightly harder, while the soap content by actual analysis was at least 5% lower in Example 1 2 compared with Example 1.

Example 3 shows the use of a heavy distillate cylinder stock having a Saybolt viscosity at 210 F. of 220 seconds which resulted, after heat subjection and neutralization with caustic soda, in a grease showing by analysis 30.6% soda soap and a penetration similar to the other examples Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A substantially dehydrated lubricating grease adapted for the lubrication of locomotive driving journals, consisting essentially of mineral lubricating oil and between 20 and 35% of soda fatty acid soap, and having a penetration by the modified A. S. T. M. method less than about 100, and a melting point of about 350 to 400 F.

2. A substantially dehydrated lubricating grease adapted for the lubrication of locomotive driving journals, consisting essentially of mineral lubricating oil and between 20 and 30% of soda fatty acid soap, and having a penetration by the modified A. S. T. M. method less than about 100, and a melting point of about 350 to 400 F.

3. A substantially dehydrated lubricating grease adapted for the lubrication of locomotive driving journals, consisting essentially of mineral lubricating oil and about 25% of soda fatty acid soap, and having a penetration by the modified A. S. T. M. method less than about 100, and a melting point of about 350 to 400 F.

4. A substantially dehydrated lubricating grease adapted for the lubrication of locomotive driving journals, consisting essentially of between 20 and 40% of soda fatty acid soap and an oil mixture of cylinder stock and a substantial proportion 01' a paraflin distillate lubricating oil, said oil mixture having a Saybolt viscosity 01' less than 125 seconds at 210 F., and having a penetration by the modified A. S. T. M. method less than about 100, and a melting point of about 350 to 400 F.

GUS KAUFMAN.