US2842494A - Lithium base grease - Google Patents

Description

Unite States Patent Office 2,842,494 Patented July 8, 1958 LITHIUM BASE GREASE Richard A. Butcosk, East Heinpstead, N. Y., assigno'r to Socony Mobil Oil Company, line, a corporation of New York No Drawing. Application November 20, 1956 Serial No. 623,318

13 Claims. (Cl. 252-36) This invention has to do with greases characterized by a high order of effectiveness over a wide range of operating conditions. More specifically, the invention is related to lithium base lubricating grease compositions which possess outstanding mechanical stability when worked in the presence of excess water.

This application is a continuation-in-part ofmy copending application Serial No. 409,760, filed February 11, 1954, which has been abandoned.

In recent years, a demand has been created for greases of outstanding lubricating character which retain their grease structure during use over a wide range of operating conditions. For example, there has been an increasing demand for water-resistant greases by the military and by such industries as steel mills, paper mills and food canning. Until recently, lithium stearate greases have been sufficiently water-resistant to meet specifications announced by the military and industry. Now, however, specifications have been made more stringent in order that excellent lubricating performance be assured in service.

Lithium stearate greases have been designated as waterresistant or water-repellant, in accordance with their evaluation in the water washout test (specification ANG-Sa) and the water-resistant test (specification O. S. 1350). A more severe water test, more recently announced, is that involving admixture of of water with the grease and working the resulting mixture in a motor-matic worker for 100,000 double strokes. This test is fully described in the military specification MIL- G-l0924, Amendment 2. Conventional types of lithium soap greases, particularly lithium stearate greases, work to a semi-fluid condition in this latter test. A number of steps have been taken to increase the water resistance of such greases. For example, free fat, such as high titer animal tallow, has been incorporated in the grease for this purpose. This approach appears to be disadvantageous or deleterious in other respects in that the fat is unstable and generally decomposes into fatty acids and glycerin, such that the grease eventually softens in storage and also in service. Other additives such a'szinc naphthenate and zinc resinate, have been used in greases to improve the water-resistance characteristics, but they, too, soften with water.

It is an object of this invention, therefore, to provide a grease which retains its original character over a wide range of operating conditions. A primary object of the invention is to provide a grease composition characterized by excellent mechanical stability of lubricating quality and of grease-like structure, when worked in the presence of excess water. Other objects of the invention will be apparent from the following description:

These and other objects have been realized by formation of new and novel lithium base compositions, which contain mixtures of lithium soaps in which the acid components of the soaps comprise balanced proportions of wool grease fatty acids and aliphatic acids having at least about 12 carbon atoms per molecule, The same objects are also realized by forming mixtures of lithium and sodium soaps, lithium and potassium soaps, and of lithium and tin soaps, of said acids, in which mixtures balanced proportions of lithium and sodium, lithium and potassium, and lithium and tin, respectively, are main- 'tained.

Wool grease fatty acids are well known in the art. For example, they have been described in detail by E. S. Lower in the Industrial Chemist, in the March, May and October issues of 1947. As defined in the aforesaid publication, wool grease fatty acids are those fatty acids which are obtained when the soap solutions obtained in the manufacture of lanolin are acidified, may be extremley pale in color, or may be very dark to almost black, and may be nearly free from odour or have a strong acidic smell. They range from soft, limpid compositions to hard, wax-like materials, the latter usually being a paler product.

As further explained in the aforesaid publication, Wool grease fatty acids are composed, generally speaking, of the fatty acids obtained from the scouring liquids used in washing the wool in textile mills, and also the natural free wool wax acids and neutral saponifiable matter. They may also contain, depending upon the care taken in their manufacture and finish, traces of undecomposed soap from the manufacture of wool wax, and also traces of water soluble salts, mainly sodium sulfate, and also e'ven traces of free sulfuric acid used in the decomposition of'the' above-mentioned soap.

Physical characteristics of wool grease fatty acids, and of a typical wool grease fatty acid product, are illustrated below in the following tabulation:

PHYSICAL CHARACTERISTICS oi wooL GREASE FATTY ACIDS Range Typical Moisture .percent 1-5 2 Unsaponlflable. do A 3-7 5 Saponlfiable, do. -98 Free Fatty Acids, as Oleic d0 70-95 84 Free Neutral Fat .do. 0-5 None Saponification Value -190 170 Iodine Value; 20-50 25-34 Titer 40-45 40-43 The above tabulation is descriptive particularly of wool grease fatty acids as produced in the United Kingdom. More recently in the U. S. A., with the advent of the 'recovery'of lanolin alcohols and cholesterol from degras, wool grease fatty acids of somewhat different physical and chemical characteristics are available, and are a preferred material.

U. s. A. WOOL GREASE FATTY ACIDS RECOV- ERED AS A BY-PRODUCT OFLANOLINHALCO- HOLS AND CHOLESTEROL MANUFACTURE Acid number 105-125 Saponification number -165 Iodine number (Hanus) 10-20 Titer, "C- t 50-53 Acetyl number 45-75 Water percent 1-3 Typical of such materials are vegetable, animal andfish fatty oils, and hydrogenated fatty materials thereof, such as stearin, hydrogenated tallow fatty acids, hydrogenated soya bean fatty acids, hydrogenated fish oils and partial hydrogenated marine, vegetable, and animal oils. Preferred herein, together with the wool grease fatty acids, are stearic acid and palmitic acid, and myristic acid. A particularly outstanding grease is obtained with balanced proportions of wool grease fatty acids, stearic acid and hydroxy stearic acid.

One of the most critical relationships involved in the formation of the lithium-lithium base greases of this invention, is the balanced proportion of the lithium soap acid components. It has been found that the desired waterresistant characteristic is obtained only by using from about percent by weight to about 80 percent by weight of wool grease fatty acids, with the remainder of the :acid components comprising aliphatic acids of the character described above. Outstanding grease compositions are obtained when the balance of acid components comprises from about 25 percent by weight to about 50 percent by weight of wool grease fatty acids, with the remainder being the aforesaid aliphatic acids. For example, when lithium soaps of wool grease fatty acids are totally absent from corresponding lithium base grease compositions, the latter have unsatisfactory waterresistant characteristics. Even when the lithium soaps of wool grease fatty acids are present in combination with other lithium soaps, such as lithium stearate, but in inadequate proportions, the resulting compositions are found to be unsatisfactory. Such a grease composition is one wherein the lithium soaps of wool grease fatty acids represent less than about 15 percent by weight of total fatty acid content. Another feature to be noted is a grease containing only lithium soaps of wool grease fatty acids, is inferior to greases of this invention; that is, such a grease sets up in prolonged storage or in other words, the grease becomes much firmer in consistency such that it fails to lubricate properly when used.

The finished lithium-lithium greases can be somewhat acidic, somewhat basic in reaction or can be neutral. That is, the finished greases can contain acid equivalent to as much as 0.5 percent by weight of oleic acid, or can contain alkali equivalent to as much as 0.2 percent by weight of lithium hydroxide. correspondingly, the lithium-sodium, lithium-potassium and lithium-tin greases can also be acidic, neutral or basic; and substantially the same limits of acidity and alkalinity obtain. As indicated above, mixtures of lithium and sodium soaps of the foregoing acids are also contemplated herein. When such mixtures are used, the mole ratio of lithium to sodium (Li:Na) of the lithium and sodium compounds used in the pre-formed soaps or the soaps formed in situ will be between about 15:1 to about 3: 1, with preference being given to ratios within the range of about 6:1 to about 4: 1.

Contemplated herein also are mixtures of lithium and potassium soaps of the foregoing acids. The ratio of lithium to potassium (LicK) of the lithium and potassium compounds used in the preformed soaps or the soaps formed in situ will be between about 50:1 to about 10:1; preferred ratios are those from about 40:1 to about :1.

Also indicated above as coming within the bounds of this invention are mixtures of lithium and tin soaps. The ratio of lithium to tin (LizSn) of the lithium and tin compounds used in the preformed soaps or the soaps formed in situ varies from about 5021 to about 8:1; preferred ratios range from 30:1 to about 20:1.

It is to be understood that mixtures of lithium soaps with more than one soap of the other metalssodium, potassium and tincan be used. That is, the final composition can contain lithium, sodium and potassium soaps; lithium, potassium and tin soaps; lithium, sodium and tin soaps; lithium, sodium, potassium and tin soaps. In such mixtures, the balance of acids defined above is main tained. Similarly, .the mole ratio of lithium to other metals will fall within the bounds indicated above.

The total quantity of soaps (lithium and lithium; lithium and sodium; lithium and potassium; lithium and tin; etc.) is also balanced in order to provide greases of the desired character. The soaps comprise from about 5 to about 30 percent (by weight) of the finished greases, and preferably from about 7 to about 20 percent.

Inasmuch as methods for the preparation of lithium, sodium, potassium and tin soaps, and greases containing the same, are well known in the art, discussion of the same is believed to be unnecessary here. It is to be understood, however, that preformed soaps can be incorporated in oil to make the greases; and that the soaps can be formed in situ. Illustrative examples, however, are furnished hereinbelow as a guide.

It will be understood also that a variety of lithium, sodium, potassium and tin compounds can be used in preparing the soaps present in the new grease compositions. For example, lithium compounds such as the hydroxide, carbonate and hydride can be used. Typical of the sodium and potassium compounds useful herein, in addition to the individual metals, are the carbonates and hydroxides. Of the tin compounds which are useful herein, the stannous halides are advantageous in effecting double decomposition; of these, stannous chloride is preferred.

The mineral oil constituent of the greases of this invention can be of varied character. The oil constituent, is characterized by a viscosity (SUV) of greater than one second at 100 F., and generally from about 60 to about 6000 seconds at 100 F. The oil may be of naphthenic or of parafiinic character. Typical oils are a naphthenic mineral oil, having a SUV of 70 seconds at 100 F., and a solvent-refined, naphthenic oil having a SUV of 80 seconds at 100 'F.

Grease compositions of this invention may be pre pared from preformed soaps, or the soaps may be made in situ in a grease-forming base of the character described above. It will be clear that when the soaps are prepared in situ by a procedure such as that illustrated below, there will be formed a mixture of wool grease fatty acid soaps and of the aforesaid aliphatic acid or acids, with the metals used being distributed between the said acids. Obviously, when only lithium soaps are involved, the mixture will comprise lithium wool grease fatty acid soaps and one or more lithium soaps of one or more aliphatic acids. Where a mixture of lithium and sodium soaps are desired, then the resulting mixture will comprise: lithium wool grease fatty acid soaps, a lithium soap or soaps of the aliphatic acid or acids, sodium wool grease fatty acid soaps and a sodium soap or soaps of the aliphatic acid or acids. correspondingly, when the mixture to be formed 18 one of lithium and potassium soaps or lithium and tin soaps, the distribution of soaps will correspond .to that in the case of lithium and sodium mentioned directly above.

It has been found, however, that in preparing the grease compositions of this invention from preformed soaps, a lithium soap of the aliphatic acid (i. e. other than lithium wool grease fatty acid soap) must be present. Or, expressed in another manner, at least some of the wool grease fatty acid soap present must contain lithium, sodium, potassium or tin. This feature is demonstrated hereinafter by a comparison of greases made with preformed soaps; the grease made with sodium stearate and lithium wool grease fatty acid soap is so different (so poor) in water-resistance or water-repellancy that it is outside the scope of this invention.

A typical procedure for preparing the greases, in situ, is the following. All of the fatty materials, wool grease fatty acids and, for example, hydrogenated tallow fatty acids and 3040 percent of the total mineral oil, are charged to a suitable grease kettle. The resulting mixture is heated to about 140460 F, and then the required proportion of lithium hydroxide monohydrate dissolved in water, is added. -This is followed by addition of a water rinse. After this, the mixture so obtained is heated to- 380-390 F., o; :r a period of one to three hours At this point, .the balance of mineral oil used in preparing the grease compositions, is added, and the total mass is reheated to 390-400 F. for a period of one to two hours. The resulting liquid product is withdrawn from the grease kettle into pans for cooling to room temperature (70-80 F.), which cooling generally requires two to ten hours. The cooled blocks of grease which are so obtained, are milled to a buttery product of the desired penetration.

Grease compositions of this invention have been compared with conventional lithium stearate and lithium hydroxy stearate greases, by subjecting said greases to the test described in military specification MIL-G-10924, amendment 2. As indicated earlier, this test involves working the greases with percent by weight of water, in a Motor-Matic Worker for 100,000 double strokes.

The results of these tests are tabulated below in Table I.

Table l A typical procedure for preparing a grease containing lithium and sodium soaps, isthe following:

All of the fatty materials, wool grease fatty acids and stearic acid and -40 percent of the total mineral oil are charged to a suitable grease kettle. The resulting mixture is heated to about 140-160 F., and then the required proportions of lithium hydroxide monohydrate and sodium hydroxide, dissolved in water, are added. This is followed by addition of a water rinse. After this, the mixture so obtained is heated to 380-390" R, over a period of one to three hours. At this point the balance of mineral oil used in preparing the grease composition, is added, and the total mass is reheated to 390-400 F. for a period of one to two hours. The resulting liquid product is withdrawn from the grease kettle into pans for cooling to room temperature (7080 R), which cooling generally requires two to ten hours. The cooled blocks of grease which are so obtained, are milled to a buttery product of the desired penetration.

Hydrogenated Tallow Fatty Acids, Percent Hydrogenated Soya Bean Fatty Acids, Percent. 12 Hydroxy Stearic Acid, Percent 8. 00 9. 50 Wool Grease Fatty Acids, Percent 3. 85 8.50 3.00 1.50 fithiunli glylrdrlgxidtelfilionohygragvPercerg r 1. 1. 70 1. 55 1. 65 1; 50 1. 35

inera a chic 7 S at 1 Percent .2 .i s9. 00 89. 15 86. 87. 45 87.35 89.00 89. 15 Penetration (Unworked) at 77 F 300 230 260 250 300 2 300 Worker Test (100,000 with 10% water), 420+ 321+ 308 345 379 365 420+ Review of the data tabulated above in Table 1, reveals that grease composition 1, which contains no lithium soap of wool grease fatty acids, is characterized by poor waterresistance. This is seen by the value 420+. A similar result is found for grease composition 7; this grease contains only a lithium soap of 1'2hydroxy stearic acid. In contrast, grease. compositions 2 through 6 are all of excellent water-resistance character. Each of the latter greases is formulated from balanced proportions of wool grease fatty acids and other acids. In the latter greases, thev percentage of wool grease fatty acids ranges from about 15 percent to about 80 percent of the total acid components of the lithium soaps.

Additional greases illustrating those of this invention, are shown below in Table H. These greases are shown in a solvent-refined mineral oil in contrast to the naphthenic mineral oil vehicle used in the greases of Table I.

Table II.-S0lvent-refined mineral oil 80" at 100 F.

Hydrogenated Tallow Fatty Acids, percent. 8. 00 8. 00 8.00 Wool Grease Fatty Acids, percent 3. 85 2. 75 2.00 Lithium Hydroxid e-Monohydrate, percent... 1. 70 1. 57 1. 48 MineralOil, 80 SUV at 100 F., percent 86. 45 87. 68 88. 52 Pan Cooled Yes Yes Yes Penetration at 77 F. (Unworked) 305 207 300 Worker Test (100,000XK with 10% HzO) 287 346 373 Still further greases of the character contemplated herein, are those shown below in Table III. Here the oil vehicle is an acid-treated and solvent-treated mineral oil of higher viscosity than of the oils used shown in Tables I and II.

Table III.Acid-treated and solvent-treated mineral oil A lithium-sodium grease composition (13) of this invention is shown below in Table IV.

Table IV Stearic acid, percent 8.00 Wool grease fatty acids, percent 3.00 LiOI-LH O, percent 1.63 0.30

NaOI-I, percent Mineral oil (solvent-refined, 500 SUS F),

percent 87.07 Penetration (unworked) 270 Worker test (l00,000 with 10% H O)- 350 A typical procedure for preparing a grease containing lithium and potassium soaps is much the same as that given above for the lithium-sodium grease. The only change made is in the use of potassium hydroxide in place of sodium hydroxide.

Representative of the lithium-potassium soap greases is that shown (14) in Table V below.

Table V Lithium-tin grease compositions can be prepared by the following procedure:

Heat the fatty materials and about 30-40% of the mineral oil to F. and add the LiOH dissolved in water, and the dry tin stearate. Heat and stir to dehydrate the mixture of a temperature of 400 F. Add the balance of the mineral oil in two portions and each time reheat the mixture to 400 F. Allow the product to cool to room temperature. The cooled block of grease is then milled to a buttery product of the desired penetration.

A lithium-tin grease composition (15) of the invention is illustrated below in Table VI.

Table VI Stearic acid, percent 7.00 Wool grease fatty acids, percent 3.00 LiOHH O, percent 1.60 Tin di-stearate, percent": 1.00

Mineral oil (solvent-refined, 500 SUS 100 F.),

percent 87.40

Penetration 77 F. (unworked) 261 Worker test (100,000X A with H percent 302 As indicated above, grease compositions of the type contemplated herein can be prepared with preformed soaps. Conventional procedures can be used when making use of the preformed soaps. The illustrative grease compositions shown below were prepared in the following manner.

The wool grease fatty acid soap was mixed with about thirty percent (by weight) of the total mineral oil; the mixture was heated to about 400 F., and the resultant mixture was cooled. The conventional aliphatic acid soap (i. e., the stearate) was mixed with about thirty percent of the total mineral oil; this mixture was heated and cooled in like manner. The two soap mixtures were then combined with each other and with the remainder fatty acids and the balance of said acid components comprising aliphatic acids having at least about twelve carbon atoms per molecule, the metal components of said'soaps being selected from the group consisting of lithium and lithium, lithium and sodium with the mole ratio of lithium to sodium being between about 15:1 and about 3:1, lithium and potassium with the mole ratio of lithium to potassium being between about 50:1 and about 10:1, and lithium and tin with the mole ratio of lithium to tin being between about 50:1 and about 8:1; preformed soaps of said mixtures of lithium-sodium, lithium-potassium and lithium-tin soaps comprising a lithium soap of said aliphatic acid and wool grease fatty acid soaps of said metal other than lithium.

2. A grease "defined by claim 1 wherein the mixture of soaps is formed in situ in the mineral oil.

3. A grease defined by claim 1 wherein the mixture of soaps is a mixture of preformed soaps.

4. A grease defined by claim 1 wherein the proportion of said mixture of soaps is from about 5 to about 30 percent by weight of the grease.

5. A grease defined by claim 1 wherein the wool grease fatty acids comprise from about twenty-five percent by of the oil; the resulting mixture was heated to about 400 F. The final product was cooled tom-80F. and, when so cooled, was milled to a product of the desired penetration. Grease compositions so prepared are shown in Table VII below.

Table VII.-Pref0rmed soaps Soaps 16 Sodium Stearate, percent Lithium Soaps of wool grease Fatty Acids, percent Lithium Stearate, percent- 1 Pan cooled grease was striated which was separated into oil pockets It is to be noted in Table VII that grease composition 16 is comprised of sodium stearate and of lithium soaps of wool grease fatty acids, and that it is characterized by unsatisfactory water resistance. In direct contrast, grease composition 17 has considerable water resistance; this composition is comprised of lithium stearate and sodium soaps of wool grease fatty acids.

it is to be understood that the greases of this invention can also contain other characterizing materials. For example, the greases can contain grease antioxidants such as amines, phenols, sulfides, etc., and lubricity improving agents such as free fat, free fatty acids, esters of alkyl and/or aryl acids, sulfurized fats, lead soaps, etc. These characterizing materials do not detract from the lubricating value of the greases contemplated herein; rather, these characterizing materials serve to impart their customary properties to the grease. The amount of such additives can be added to grease compositions of this invention in around about 0.01 percent to less than 10 percent by weight, and preferably 0.1 to 5.0 percent by weight. 1

Greases of this invention are applicable for general automotive uses, and are excellent aircraft greases, industrial greases and the like. a

I claim:

l. A lubricating grease comprising a major proportion of mineral oil and a minor proportion, sufficient to form a grease, of a mixture of soaps selected from the group consisting of preformed soaps and of soaps formed in situ in the mineral oil, the acid components of said soaps comprising from about fifteen percent by weight to about eighty percent by weight of wool grease components.

6. .A grease defined by claim 1 wherein the aliphatic acid is stearic acid.

7. A grease defined by claim 1 wherein the aliphatic acid is hydroXy-stearic acid.

8. A grease defined by claim 1 wherein the aliphatic acids comprise a mixture of stearic acid and hydroxystearic acid.

9. A lubricating grease comprising a major proportion of mineral oil and a minor proportion, sufficient to form a grease, of a mixture of lithium soaps, the acid components of said soaps comprising about twenty-five percent by weight of wool grease fatty acids and about seventy-five percent by weight of stearic acid.

10. A lubricating grease comprising a major proportion of mineral oil and a minor proportion, sufficient to form a grease, of a mixture of lithium soaps, the acid components of said soaps comprising about one-third by weight of wool grease fatty acids and about two-thirds by weight of stearic acid.

11. A lubricating grease comprising a major proportion of mineral oil and a minor proportion, suificient to form a grease, of a mixture of lithium soaps, the acid components of said soaps comprising about one-fourth by weight of wool grease fatty acids and about threefourths by weight of stearic acid.

12. A lubricating grease comprising a major proportion of mineral oil and a minor proportion, sufficient to form a grease, of a mixture of lithium and sodium soaps formed in situ, the acid components of said soaps comprising about one-third by weight of wool grease fatty acids and about two-thirds by weight of stearic acid, the mole ratio of lithium to sodium being about 5:1.

13. A lubricating grease comprising a major proportion of mineral oil and a minor proportion, sufficient to form a grease, of a mixture of lithium and tin soaps formed'in situ, the acid components of said soaps comprising about one-third by weight of wool grease fatty acids and about two-thirds by weight of stearic acid, the mole ratio of lithium to tin being about 26:1.

References Cited in the file of this patent UNITED STATES PATENTS 2,676,149 Woods et a1. Apr. 20, 1954 FOREIGN PATENTS 550,429 Great Britain Jan. 7, 1943 7 OTHER REFERENCES Wool Wax, D. T. C. Gillespie, Hobart Pub. Co. Washington, D. C., 1948, pages 55 and 56.

Claims (1)

1. A LUBRICATING GREASE COMPRISING A MAJOR PROPORTION OF MINERAL OIL AND A MINOR PROPORTION, SUFFICIENT TO FORM A GREASE, OF A MIXTURE OF SOAPS SELECTED FROM THE GROUP CONSISTING OF PREFORMED SOAPS AND OF SOAPS FORMED IN SITU IN THE MINERAL OIL, THE ACID COMPONENTS OF SAID SOAPS COMPRISING FROM ABOUT FIFTEEN PERCENT BY WEIGHT TO ABOUT EIGHTY PERCENT BY WEIGHT OF WOOL GREASE FATTY ACIDS AND THE BALANCE OF SAID ACID COMPONENTS COMPRISING ALIPHATIC ACIDS HAVING AT LEAST ABOUT TWELVE CARBON ATOMS PER MOLECULE, THE METAL COMPONENTS OF SAID SOAPS BEING SELECTED FROM THE GROUP CONSISTING OF LITHIUM AND LITHIUM, LITHIUM AND SODIUM WITH THE MOLE RATIO OF LITHIUM TO SODIUM BEING BETWEEN ABOUT 15:1 AND ABOUT 3:1, LITHIUM AND POTASSIUM WITH THE MOLE RATIO OF LITHIUM OF POTASSIUM BEING BETWEEN ABOUT 50:1 AND ABOUT 10:1, AND LITHIUM AND TIN WITH THE MOLE RATIO OF LITHIUM TO TIN BEING BETWEEN ABOUT 50:1 AND ABOUT 8:1, PREFORMED SOAPS OF SAID MIXTURES OF LITHIUM-SODIUM, LITHIUM-POTASSIUM AND LITHIUM-TIN SOAPS COMPRISING A LITHIUM SOAP OF SAID ALIPHATIC ACID AND WOOL GREASE FATTY ACID SOAPS OF SAID METAL OTHER THAN LITHIUM.