US2619461A - Lubricating grease - Google Patents

Description

Patented Nov. 25, 1952 LUBRIOATING GREASE George F. Ford, Bartlesville, kla., assignor to Phillips Petroleum Company, a corporation of Delaware No Drawing. Application January 4, 1950, Serial No. 136,839

' 3 Claims.

This invention relates to greases. In one aspect, this invention relates to a grease having properties normally attributed to gel greases and properties normally attributed to fiber greases. In another aspect, it relates to a greasehaving properties superior to many properties of greases normally called gel greases and of greases normally called fiber greases.

In the art of grease-making, both gel greases and fiber greases are known. In some cases, the same ingredients may be used to make these two greases and the type of grease produced is governed by the process through which the grease is manufactured. Lubricating greases most commonly are comprised of a lubricating oil and an alkali metal salt of a fatty acid, although fatty acid salts other than alkali metal salts may frequently be used.

Fiber greases are usually produced by a process in which initially a fat or tallow is saponified by caustic alkali in the presence of a portion of the lubricating oil, this saponification being carried out at a temperature approximately at the boiling point of the caustic solution after which the temperature is raised to 220-240 F. so that at least most of the water present is vaporized and removed from the grease-making vessel. The mass present in the kettle is agitated or stirred during the process to facilitate saponification and to aid in the formation of a fibrous structure in the oil-soap mixture. Additional oil is added during the dehydration and cooling stages to bring the composition to the proper proportion of oil and soap. The temperature range during the oil addition may range from 240 F. down to about 140 F. or even lower. It will be noted that in this procedure, the grease will contain, in addition to oil and soap, some glycerol and unvaporized water, which are ordinarily not objectionable. In some cases, however, fatty acids are neutralized in the presence of the oil instead of saponification of glycerides in which case greases containing substantially no glycerine are formed. Numerous modifications of these processes may be used, relatively slow cooling of these greases being desirable in at least most cases.

In the production of a gel grease, a neutral soap, such as a metal salt of a fatty acid, is heated with oil to a temperature sufficiently above the melting point of the soap that with slight stirring a single liquid phase is produced. This liquid is then cooled, preferably quickly, and the grease produced has a gel structure. The grease may subsequently'be Worked to produce a smooth grease of desirable characteristics.

Gel greases are most suitably produced from high viscosity index, low viscosity oils and metal salts of fatty acids. Viscosity index (hereinafter called V. I.) is a measure of the change in viscosity caused by change in temperature, an oil having a high viscosity index changing less in viscosity over a given temperature range than one having a lower index, see Dean 8; Davis, Chem. Sz Met. Eng. 36, 618 (1929). The oils are suitably from 100 to 700 viscosity Saybolt Universal seconds (hereinafter called S. U. S.) preferably from 150 to 500 S. U. S., at 100 F., and with a V. I. of or above. Suitable soaps include those not only containing an alkali metal radical, but also aluminum, barium, etc. Gel-type greases, especially those containing alkali metal soaps, have the ability to lubricate high speed bearings, have excellent work stability, good operational temperature range, and better oxidation stability. However, they do not cling to metal surfaces, are not good sealants, bleed excessively on standing, tend to spatter, and will not return to their original condition if overheated. v

The fiber greases are most suitably produced from low V. I. (e. g. less than 90), high Viscosity (e. g. greater than 150 S. U. S. and preferably greater than 500 S. U. S. at F.) oils and an alkali metal salt of a fatty acid, usually the sodium salt. These fiber greases are good in many applications because of their ability to adhere to metal surfaces. Also, these greases are readily sealed in bearings with simple, economical seals, thus not having to be replaced often due to leakage or presence of foreign material, such as dust and dirt, which hasworked into the bearing. However, the fiber greases are not satisfactory for lubrication of high speed bearings, are useful only over a relatively small range of temperatures, and have poor work stability, completely losing their body, or resistance to penetration by a conical object, in about onehundredth the number of milling or working strokes that a gel grease can easily stand without any substantial loss of body. By the milling or working strokes is meant the number of strokes on a grease worker carried out according to standard procedure with an AN-G worker (Army-Navy grease worker).

The numerical values of the penetration as given herein are mioropenetrator values. Micropenetrator values are penetration values made according to the A. S. T. M. Test D-21'7- l4'1, but modified so as to use a micropenetrator needle, plunger, and cup, as described by Kaufman, Finn and Harrington in Industrial and Engineering Chemistry, Analytical Edition 11, 108-110 (1939).

Gel greases having satisfactory lubricating properties can seldom be made with oils having viscosities higher than 500 to 700 S. U. S. However, gel type greases made from oils of higher viscosities are desirable and are often needed. My invention, therefore, permits the incorporation of such a higher viscosity oil (in the form of a fiber grease) in a gel type grease. The resulting grease then contains at least a substantial proportion of high viscosity oil and at the same time passes properties of a gel type grease.

Blending of a high viscosity oil directly with a gel grease usually produces a fiuid mass without grease structure and is, therefore, not a satisfactory grease. When mixing a high viscosity oil with a melted soap according to usual procedure for making a gel grease, and after cooling, the mass is thick and of little lubricating value.

An object of my invention is to provide a grease having properties normally attributed to those of gel greases and properties normally attributed to fiber greases.

Another object of my invention is to provide a grease having some properties superior to those normally attributed to gel and to fiber greases.

Another object of my invention is to provide amethod for the production of a grease having properties superior to some of the properties of gel greases and fiber greases.

Another object of my invention is to provide a method for producing a grease having gelgrease properties but containing at-least some high viscosity oil.

Qther objects and advantages of my invention will become apparent upon reading the following specification.

I have found that a grease comprising a mixture of these two types of grease produced in a manner to be described retains the desirable properties of each' type of grease and minimizes the undesirable properties found in each type of grease. Initial step of the process is production of the two individual greases.

Soda base gel greases madewith oil of viscosity preferably of 150 to 500 S. U. S. at 100 Rare heated toincorporate the sodium salt of a fatty acid into the oil. The mixture is cooled quickly and the resultingmass workedto obtain a homogeneous mass of good penetration for a gel grease. Aluminum base gel greases are prepared by heating the aluminum salt of the fatty acid with ,the oil and the mixture is cooled slowly. After cooling this latter grease may or may not be worked to improve its homogeneity. Lithium and other alkali metal gel greases are made in about the same manneras the sodium greaseand they are likewise worked to obtain homogeneous greases of good stability.

The fiber grease is produced by saponification of a fatty acid, or an ester, such as tallow. or

animal fat, in a high viscosity (e. g. greater than 150 S. U. S. and preferably greater than 500 S. U. S. at 100 F.) lowV. I. (e. g. less than 90) oil to produce a mixture containing about 50 per cent soap. The soap concentrateisthen heated to 200-250 F. to remove most of the water. More cold oil of high viscosity and low V. I. is added with stirring to produce the fiber grease. gel grease is then incorporated with stirring (not severe. working) into the fiber grease, the temperature in this mixing step being from 60 to 170 F., preferably from 110 to 140 F. It is preferred that the two greases to be mixed should have about the same consistency. The final grease should comprise 5 to 95 per cent, preferably 20 to 70 percent, of the gel grease; and it shall contain between 8 and 20 weight per cent soap.

The fibrous-gel grease, as the grease of this invention may be quite aptly termed, has a fiber greases tendency to cling to metal surfaces, and has much less tendency to bleed than conventional gel grease. The present greaseis also less temperature sensitive, whereas a conventional fiber grease softens and a conventional gel The grease hardens on heating. It is especially noteworthy that the fibrous-gel grease is, as prepared by the process of this invention, quite work stable, and thus retains its lubricating properties during use.

In one specific embodiment of this invention, a neutral oil is solvent extracted, for example with phenol, to produce a high V. I., parafiinic fraction and a low V. I., relatively non-paraifinic fraction. The high V. I. fraction is of relatively low' viscosity and the low V. I. fraction is of relatively high viscosity. The parafilnic fraction is then used in making one grease constituent and the non-parafiinic fraction in making another. The two greases are thenmixed to produce the fibrous-gel grease of this invention.

The examples following all contain the same ingredients except Example 5 which includes only the 170-180 S. U. S. oil of Example 1.

Example 1 A first gel-type grease was made from a-l- 180 S. U. S. oil (solvent extracted. Midcontinent neutral, V. I. above with 20 per cent sodium stearate and worked .1000 strokes on an AN-G plate using an A. S. T. M. grease worker. A second or fiber-type grease was made from a. 750 S. U. S. naphthenic oil (V. I. of 60) using 20 per centsodium stearate. The first grease was incorporated at F. with stirring into an equal portion of the second grease. The resulting grease was then worked 80,000 strokes on the AN-G worker and had a micro-penetration after this treatment of 114. The final product possessed desirable properties normally attributed to gel grease and'to fiber greases.

Example 2 This grease was the same as the grease of Example 1 except thatthe oil not retained in the first grease prior to working was drained off and incorporated into the second grease during its formation. The final grease produced was worked with the AN-G workerfor 80,000 strokes, after which it hada micro-penetration of 148. The first grease of thisexample accordingly contained a little more-than 20 per cent sodium stearate and the second grease constituent contained a little less than 20 per cent sodium stearate. The greases of Examples 1 and 2 are excellent fibrous gel greases.

Example 3 Same as Example 1, except that the first grease was not worked prior to incorporation into the second grease. After 80,000 strokes on the AN-G grease worker, the micro-penetration was.303..

Example 4 A gel-type grease was made by mixing equal portions of the two oils of Example 1, adding sodium stearate to obtain a 20 per cent concentration in the final grease, heating to, 464 F., and quickly cooling. This grease after 80,000 strokeson the grease worker had a micro-penetration of 298.

Example 5 A gel grease of 20 per cent sodium stearate is made with the 170480 viscosity oil of Example 1, and the grease is worked. This gel grease has a micro-penetration of 70-75 after 80,000 strokes on the AN-G grease worker.

Example 6 A- lithium stearate gel grease was made-using 20 per cent lithium stearate in -180 S, U. S.

oil of Example 1. A sodium stearate fiber grease was made using per cent sodium stearate in 750 S. U. S. oil of Example 1. The two greases were mixed in equal proportions and worked 80,000 strokes using the AN-G plate of the grease worker. The micro-penetration was 230. While not quite the equal of the greases of Examples 1 and 2 in work stability, this grease had good characteristics. Lithium base gel greases ordinarily have a penetration in the range of 200 to 250.

Example 7 An aluminum stearate gel grease was made using 20 per cent aluminum stearate in 170-180 S. U. S. oil of Example 1. A sodium stearate fiber grease was made using 20 per cent sodium stearate in 750 S. U. S. oil of Example 1. The two greases were mixed in equal proportions and worked 80,000 strokes using the AN-G plate of the grease worker. The micro-penetration was 126.

It will be noted that the fibrous-gel grease of Example 1 had nearly as gOOd work stability as the best gel grease, the grease of Example 5. The fibrous-gel grease, however, has the additional advantage of clinging to metal surfaces and ease of retention in the bearing. A fiber-type grease alone will usually break down on 1000 strokes of working to a point of being rather fiuid. Thus, the advantages of the present invention are evident from the previous examples.

It should be noted that my fibrous grease of Example 1 has a penetration of 114 which value is substantially the equivalent of a good quality gel grease. A grease of this latter type, as in Example 5, has a penetration of 70-80. Greases which vary only points in penetration are considered to have very nearly the same hardness or consistency. My fibrous-gel grease of Example 1 exhibited the excellent penetration value of 114 after 80,000 strokes in a grease worker. This might be contrasted with a conventional fibrous type grease which ordinarily breaks down to a thick, soupy mass after 1000 strokes of working.

In the art this type of grease is believed to be a completely new grease, one having workability properties of a good gel grease and yet the clinging to metal surfaces and bleed-free properties of a fiber grease. Fiber greases withstanding 80,000 strokes on a grease worker and yet having a good penetration value is believed unknown in the art, as 1000 strokes often breaks them down.

Comparing Example 1 with Example 5, it is unexpected that a mixture, no matter how oompounded, of 50 per cent fiber grease, which breaks down in 1,000 strokes, should be more than the average of such a fiber grease and the gel grease of Example 5, yet unexpectedly the combined grease of Example 1 was substantially as good under 80,000 strokes working as that of Example 5, and had a non-bleeding, tacky character absent in the grease of Example 5.

The above-described examples are given for illustrative purposes and should not be regarded as limiting the invention, the scope of which is set forth in the following claims.

Having described my invention, I claim:

1. A method for producing a grease comprising mixing a fat with a quantity of oil, saponifying the fat of said mixture With a caustic alkali in the presence of said oil, heating the saponified mixture to a temperature from 200 to 250 F.,

admixing with said saponified mixture an additional quantity of oil, stirring the admixture to produce a fiber structure therein, to the stirred fibrous admixture incorporating with stirring a quantity of gel grease at a temperature between the limits of 60 to 170 F. and the quantity of gel grease incorporated comprises 5 to per cent of the final grease.

2. In the method of claim 1, incorporating said gel grease into said stirred fibrous admixture at a temperature between the limits of to F. and the quantity of gel grease incorporated comprises 20 to 70 per cent of the final grease.

3. In the method of claim 1, the proportion of fat mixed with said quantity of oil is such as to yield a saponified mixture containing at least 50 per cent soap.

4. A method for producing an improved grease comprising melting a neutral soap, admixing with the melted soap a quantity of a first oil to produce a single oil-soap phase, cooling the mixture quickly and working the cooled mixture to produce a smooth first grease, adding to some fatty acid material a quantity of a second oil, saponifying said fatty acid material in the presence of said second oil with a caustic alkali, heating this saponified mass to a temperature between the limits of 200 and 250 F., into the heated mass admixing an additional quantity of said second oil, and into this latter admixture incorporating with stirring said first grease at a temperature between the limits of 60 to 170 E, the proportion of said first grease so incorporated constituting from 5 to 95 per cent of the final grease product.

5. In the method of claim 4, said first oil has a viscosity index above 90 and a viscosity between the limits of 100 and 700 seconds, Saybolt Universal at 100 F. and the second oil has a viscosity index below 90 and a viscosity above 100 seconds, Saybolt Universal at 100 F.

6. In the method of claim 4, said first oil has a viscosity index above 90 and a viscosity between the limits of and 500 seconds, Saybolt Universal at 100 F. and the second oil has a viscosity index below 90 and a viscosity above 150 seconds, Saybolt Universal at 100 F.

7. In the method of claim 4, solvent extracting a lubricating oil stock to produce a raffinate oil having a viscosity index above 90 and a viscosity between the limits of 150 and 500 seconds Saybolt Universal as said first oil, and an extract oil having a viscosity index below 90 and a viscosity above 150 seconds Saybolt Universal at 100 F. as said second oil.

8. In the method of claim 4, the proportion of fatty acid material and second oil is so chosen that the saponification product thereof contains at least 50 per cent soap.

GEORGE F. FORD.

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

UNITED STATES PATENTS Number Name Date 2,257,945 Fraser Oct. 7, 1941 2,475,589 Bondi July 12, 1949 OTHER REFERENCES Klemgard-Lubricating Greasespages 84, 85, 584 and 585, pub. 1937 by Reinhold Pub. Corp., New York, N. Y,

Claims (1)

1. A METHOD FOR PRODUCING A GREASE COMPRISING MIXING A FAT WITH A QUANTITY OF OIL, SAPONIFYING THE FAT OF SAID MIXTURE WITH A CAUSTIC ALKALI IN THE PRESENCE OF SAID OIL, HEATING THE SAPONIFIED MIXTURE TO A TEMPERATURE FROM 200* TO 250* F., ADMIXING WITH SAID SAPONIFIED MIXTURE AND ADDITIONAL QUANTITY OF OIL, STRIPPING THE ADMIXTURE TO PRODUCE A FIBER STRUCTURE THEREIN, TO THE STIRRED FIBROUS ADMIXTURE INCORPORATING WITH STIRRING A QUANTITY OF GEL GREASE AT A TEMPERATURE BETWEEN THE LIMITS OF 60* TO 170* F. AND THE QUANTITY OF GEL GREASE INCORPORATED COMPRISES 5 TO 95 PER CENT OF THE FINAL GREASE.