US2733208A

US2733208A - Hours at

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Publication number: US2733208A
Authority: US
Publication date: 1956-01-31
Anticipated expiration: 1973-01-31

Description

Jan. 31, 1956 MIGROPENETRATION MMJIO AT 77F.

Fild Dec. 15, 1952 E. o. FORSTER 2,733,208

MIXED ALKALINE EARTH METAL SOAP GREASE COMPOSITIONS 2 Sheets-Sheet 1 FIGURE"! ALKALINE HOURS AT 250% FIGURE2 ACID HOURS AT 250w.

Eric 0. Forster Knveflor B I 72 Clflorneg E. O. FORSTER Jan. 31, 1956 MIXED ALKALINE EARTH METAL SOAP GREASE COMPOSITIONS 2 Sheets-Sheet 2 Filed Dec. 15, 1952 Ou-Sr-Bo HOURS AT 250 F.

Eric 0. Forster nventor United States Patent NIIXED ALKALINE EARTH METAL SOAP GREASE COMPOSITIONS Eric 0. Forster, Hillside, N. J., assignor to Esso Research 3 This invention relates to mixed soap lubricating grease compositions. Particularly the invention relates to lubricating grease compositions which have excellent high temperature stability which are formed from mixtures of three alkaline earth metal soaps. More particularly the invention relates to high temperature grease compositions which consist essentially of a lubricating oil thickened to a grease consistency with a mixture of the calcium, barium and strontium soaps of high molecular weight fatty acids.

The preparation of calcium base greases as such is old in the art and is well described in the patent literature. Such greases are excellent in structure, water resistance and appearance. However, the high temperature stability of calcium greases is very poor. This is due to the necessity of incorporating Water with the calcium soaps during their preparation. At temperatures above about 200 F. the Water of formulation is driven off and the grease structure breaks down.

It has been found and forms the object of the copending application Serial No. 301,194 filed July 28, 1952, now U. S. Patent No. 2,708,659, by the same inventor that calcium greases may be improved by the incorporation of minor amounts of magnesium, barium or strontium metal soaps. These investigations have also pointed out that a combination of strontium and barium soaps show no attractive properties.

It has now been found that a combination of calcium, barium and strontium soaps result in a lubricating grease composition which combines the excellent structure, water resistance and appearance of the calcium soaps with excellent high temperature stability.

Briefly stated the grease compositions of invention are prepared by thickening to a grease consistency a lubrieating oil base stock with a mixture of the calcium, barium and strontium soaps of high molecular weight fatty acids. The greases of this invention are prepared by methods of manufacture familiar to the art and the preparation presents no special problems. Care must be taken only to prepare the most insoluble soap first, followed by the lesser soluble soap and the most soluble soap.

The preparation involves the thorough admixture of the fatty acid used with a portion of the oil base and the addition of hydroxide of the metal which forms the most insoluble soap. The metal hydroxide is usually added in the form of a dry powderor an oil slurry. After the saponification is completed, the second most insoluble metal hydroxide is added followed by the third and last metallic component. The total mixture is then dehydrated and heated to about 350 F. The remainder of the oil is then added with stirring and the final product cooled without further agitation.

The lubricating oil chosen asthe base for the grease compositions of this invention may be any of the mineral oil distillates known to the art. It shouldbe remembe'redf th'at'the mineral oil chosen for the grease base should be selected from those which would perform 2,733,208 Patented Jan. 31, 1956 the lubrication if an oil alone could be used. Paraflinic or naphthenic distillates having viscosities within the range of from 35 to 1000 SUS, preferably 40 to 250 SUS, at 210 F. may be utilized as the base for these improved magnesium greases. The lubricating oil constituent of these compositions may also be selected from a great number of the synthetic lubricants which are rapidly becoming important in the lubricating art. Exemplary of these synthetic lubes are the long chain esters, esters of dibasic acids such as sebacic and adipic acid esters, polymerized hydrocarbons such as polyolefins,

V: polymerized cracked wax, etc., alkylated aromatics, polyglycols, polyglycol ethers, polyglycol esters, polyglycol ether esters, formals of hydroxyl-containing compounds, etc.

As was stated above there is nothing critical in the fatty acid used to form the thickeners for these new grease compositions. The acid chosen may be selected from a great number of commercially available fatty acids which includes stearic acid, oleic acid, hydroxy stearic acid, hydrogenated fish oil acid, beef fat, tallow,

' the unsaturated glycerides of various fatty acids or mixtures of the above in any proportion. The acids may be used with or without plasticizers such as the polyethylene glycols and the like. Antioxidants and other commonly used additives may be used in these preparations.

, product was cooled without further agitation.

The thickening agent of the greases of this invention consists of a mixture of the calcium, barium and strontium soap from any of the above mentioned high molecular weight fatty acids. The ratio of the three soaps used will vary from about 5 to 1 to 1 mol of calcium, barium and strontium soaps respectively to about 1 to 5 to 5 mols. The preferred compositions of this invention will contain equimolar proportions of these soaps.

. The amount of the total soap mixture that is utilized will depend upon the consistency desired in the final product. Ordinarily from about 5% by weight to 30% by weight with from about 10% to about 25% being especially preferred. To illustrate this invention-- Hydrogenated fish oil acids 15.00

Calcium hydroxide 0.72 Strontium hydroxide octa-hydrate 2.60 Barium hydroxide octa-hydrate 3.10 Mineral oil (70 SUS/2l0 F.) 78.58

Preparation The total charge of the acids and the dry calcium hydrate were mixed with one third of the mineral oil and heated until saponification was complete. The barium hydroxide was then added and after complete saponification the strontium hydroxide was added. The soapmixf, ture was subsequently dehydrated and heated to about 350 F. The balance of the mineral oil was then added gradually while the mixture was being agitated. The final ratio of the soaps of this grease was 1:1:1.

EXAMPLE II Formulation Ingredients: Weight per cent Hydrogenated fish oil acids 16.00 Sodium 'hydroxide; l '.'20 Calcium hydroxide 015 8 "Strontium hydroxide octa-hydr'ate 2.08" Mineral'oil (70 SUS/2l0- F.) 80.14

3 Preparation This composition was prepared as described in Example I except that the sodium hydroxide was added as a 50% water solution as the last of the hydroxides. The mol ratio of calcium soap to strontium soap to sodium soap was 1:1:2.

EXAMPLE III Formulation Ingredients: Weight per cent Hydrogenated fish oil acids 16.00

Sodium hydroxide 1.20 Calcium hydroxide 0.58 Barium hydroxide octa-hydrate 2.47 Mineral oil (70 SUS/210" F.) 79.75

Preparation This composition was prepared as in Example II. The mol ratio of calcium soap to barium soap to sodium soap This grease composition was prepared as described in connection with Example II. The mol ratio of the barium soap to the strontium soap to the sodium soap was 1:1:2.

The above grease compositions were submitted to the ASTM micro-penetration test at room temperature and their dropping points were obtained according to ASTM procedure. The samples were placed in an oven maintained at 250 F. and subjected to this temperature for 500 hours. At intervals during the test micro-penetrations after cooling to room temperatures were obtained on the samples. At the conclusion of the 500 hour period micropenetrations were again obtained and the samples examined for oil separation and appearance. Results of these tests show the outstanding advantage of the compositions of the invention and are set out in Table I below.

sensitive to the presence of free fatty acids or free alkali is shown it Figure 1 and Figure 2 are compared. The sodium soap containing greases have poor yields when free fatty acids are present and indicate that the structure of the sodium soaps is more sensitive to free acids than the alkaline earth soap. The dropping points appear not to be dependent upon free acidity or alkalinity. In Table II are summarized the dropping points of greases containing both free acid and free alkali. Again, the alkaline earth soap combination stands out with its remarkably high rapping point.

TABLE II.-THE INFLUENCE OF FREE ACIDITY 0R AL- KALINITY ON THE DROPPING POINT OF GREASES Acid Greases Alkaline Greases Soap System Percent g g N 9.013 0 F.

Percent Oleic 2 Cn/Sr/Na s x-p. 99 53%2558 EXAMPLE V Formulation Ingredients: Weight per cent Hydrogenated fish oil acids 10.00 Calcium hydroxide 0.73 Barium hydroxide octa-hydrate 3.10 Aluminum stearate 5.00 Mineral oil (70 SUS/210 F.) 81.17

Preparation This grease was prepared as Example II except that instead of the sodium hydroxide solution, aluminum stearate was added at this point. The mol ratio of cal- TABLE I.-HIGH TEMPERATURE (1115313 8? STABILITY 500 HRS. OVEN TEST AT An examination of the properties of these .four greases points out that it is not possible to use any combination of three soaps arbitrarily. Only the greases of invention are satisfactory. For instance, if sodium is substituted for any of the three alkaline earth metals, the resulting greases bear the mark of weakness of soap structure. This is shown in Figure 1 in which the Worked micropenetrations of these greases are shown as a function of the storage time at 250 F. The oven storage test enables one to differentiate between heat stable and heat unstable greases. This diflerentiation can be directly related to the stability of the structure arrangement of the soap molecules. While the alkaline earth mixture is not sensitive to a storage time of 500 hours at 250 F., the sodiumcontaining greases appear to soften and to be Subject to transitions. That the alkaline earth metal greases are not cium to barium to aluminum soap is 1:1: 1, the aluminum soap being calculated on the basis of a distearate.

This composition was prepared as Example 'V. The mol ratio of barium to strontium to aluminum soap was 5 1:1:1, calculating the aluminum soap as a distearate.

The formulations disclosed herein must be distinguished fromcomplex soap greases. In these compositions only physical mixtures of soaps are involved, While in the complex soap greases a new species is formed which is responsible for the properties of the resulting grease.

To reiterate briefly this invention relates to mixed base lubricating greases that have excellent high temperature stability properties which are prepared by thickening a lubricating oil with a mixture of the calcium, barium and strontium soaps of high molecular weight fatty acids. From 5% to 30% by weight, preferably to 25% by weight of the total soap mixture is used as the thickening agent. In the preferred composition a mineral lubricating oil is thickened to a grease consistency with from 10% to 25% by Weight of an equimolar mixture of the calcium, barium and strontium soaps of high molecular Weight substantially saturated fatty acids. Oils having a viscosity of from 35 to 1000, preferably 40 to 250 SUS at 210 F. may be used as the grease bases.

What is claimed is: I

1. A lubricating grease composition which consists essentially of a lubricating oil base stock containing combined therein a grease forming amount of a mixture of calcium, barium, and strontium soaps of high molecular Weight fatty acids, said mixture containing a molar ratio of calcium to barium to strontium soaps within the range of from 5:1:1 to 1:525.

2. A composition according to claim 1 wherein there is present from 5.0% to 30.0% by weight of the total soap mixture.

3. A composition according to claim 1 wherein the lubricating oil has a viscosity at 210 F. within a range of from to 1000 SUS.

4. A lubricating grease composition consisting essentially of a mineral lubricating oil base stock thickened to a grease consistency with from about 10.0% to about 25.0% by Weight of a mixture of soaps comprising about equimolar proportions of the calcium, barium, and strontium soaps of high molecular weight fatty acids.

5. A process for the preparation of lubricating greases which comprises the steps of forming a calcium soap in a lubricating oil, then forming a barium soap and a strontium soap respectively, heating the total mixture to above the transition point of the soaps, adding additional lubri eating oil, and then cooling the heated mixture.

2,070,781 Brunstrum et a1 Feb. 16, 1937 2,389,523 Leyda Nov. 20, 1945 2,417,430 McLennan Mar. 18, 1947 2,417,433 McLennan Mar. 18, 1947 2,628,195 Allison et a1. Feb. 10, 1953 2,628,202 Allison Feb. 10, 1953 FOREIGN PATENTS 449 Great Britain Oct. 11, 1886 1,659 Great Britain Mar. 1, 1890 610,190 Great Britain Oct. 12, 1948 622,945 Great Britain May 10, 1949 746,309 France May 26, 1933

Claims

1. A LUBRICATING GREASE COMPOSITION WHICH CONSISTS ESSENTIALLY OF A LUBRICATING OIL BASE STOCK CONTAINING COMBINED THEREIN A GREASE FORMING AMOUNT OF A MIXTURE OF CALCIUM, BARIUM, AND STRONTIUM SOAPS OF HIGH MOLECULAR WEIGHT FATTY ACIDS, SAID MIXTURE CONTAINING A MOLAR RATIO OF CALCIUM TO BARIUM TO STRONTIUM SOAPS WITHIN THE RANGE OF FROM 5:11 TO 1:5:5.