US3907692A - Complex soap lubricating grease - Google Patents

Abstract

A calcium complex soap lubricating grease comprising lubricating oil and calcium soaps, the calcium soap being prepared from fatty acid, calcium hydroxide, sodium phosphates, and sodium borates.

Description

United States Patent Ullmann et al.

[ Sept. 23, 1975 COMPLEX SOAP LUBRICATING GREASE Inventors: Dietrich Ullmann, Moers;

Hans-Dieter Grasshoff, Hamburg-Kirchwerder, both of Germany Assignee: Deutsche Texaco Aktiengesellschaft,

Hamburg, Germany Filed: Feb. 4, 1974 Appl. No.: 439,203

Related U.S. Application Data Continuation-impart of Ser. No. 251,665, May 9, 1972, abandoned.

Foreign Application Priority Data May 10, 1971 Germany 2122978 U.S. Cl. 252/18; 252/25 Int. Cl. ....C10M 3/18; ClOM 5/14; ClOM 7/20; ClOM 7/24 Primary ExaminerDelbert E. Gantz Assistant Examiner-l. Vaughn Attorney. Agent, or FirmT. H. Whaley; C. G. Ries; Henry W. Archer [57] ABSTRACT A calcium complex soap lubricating grease comprising lubricating oil and calcium soaps, the calcium soap being prepared from fatty acid, calcium hydroxide, sodium phosphates, and sodium borates.

4 Claims, No Drawings COMPLEX SOAP LUBRICATING GREASE CROSS-REFERENCE TO COPENDING APPLICATION This application is a continuation-in-part of coassigned patent application Ser. No. 251,665 filed May 9, 1972 and now abandoned.

BACKGROUND OF THE INVENTION This invention is concerned with a lubricating grease particularly intended for use with automatic or centralised lubricating systems and which does not undergo appreciable changes in consistency when used at temperatures above about 200C.

Experience has shown that calcium complex soap lubricating greases used with friction bearings harden at high temperatures causing the bearings to run hot and, in the extreme case, resulting in engine damage.

This hardening can only be explained by assuming that the complex formation of the calcium complex soap lubricating greases is still incomplete and contin' ues when the temperature of the bearings is above 200C. The increase in consistency is observed especially with those calcium complex soap lubricating greases exceeding a mole ratio of low molecular carboxylic acids of carbon number below 4 to high molecular carboxylic acids of carbon number above 3, of 5:1.

Solutions to problems of this kind can not be ob tained simply by combining the known elements of different lubricating greases. In the production of lubricating greases, it has been observed again and again that the solution to a problem is dependent on minor changes in composition. For instance, the use of an additional component added in a minor amount to greases of different compositions, may lead to different, even to opposite, effects with regard to the final product. These circumstances, therefore, led to a number of proposed solutions to the problems in this field of lubricating greases as described in the patent literature and to a belief in the unpredictability of the results obtained by effecting such variations in composition.

DESCRIPTION OF THE PRIOR ART The prior art to which this invention relates is already aware of the patents discussed hereinbelow.

US. Pat. No. 3,170,879 discloses lubricating greases containing pure fatty acids only and a very slight excess of calcium hydroxide to reduce local overheating.

US. Pat. No. 3,186,944 discloses a water-containing multi-purpose grease composition, wherein the complex soap contains Ca-hydroxy stearate, and/or Ca-acetate and Ca-carbonate which is produced in situ from urea, besides a Ca(OI-I) excess of from 1 to 8 percent by weight plus from 0.1 to 0.5 percent by weight of water. The grease described by the patentee is completely different from the grease of this invention, since it contains water whereas that of the invention is an anhydrous one and cannot contain any water since it is used at temperatures ranging above the boiling point of water. Furthermore, the excess amount of Ca(OH) in the grease of the patent is below the Ca(OI-l) excess range claimed here.

In US. Pat. No. 2,988,507 are proposed sodium soap greases containing an excess of alkali and, sodium phosphate in order to improve the oxidation resistance and the extreme pressure properties. The patent concerns a grease that is not at all comparable with the grease of this invention, which is employed in other fields of lubrication. The only feature that may be deemed pertinent is the addition of sodium phosphates. However, in this invention, sodium phosphate is added only in connection with sodium tetraborate in order to improve the rheological properties of the calcium grease for high-temperature lubrication, whereas in the case of the sodium grease the addition of sodium phosphate is made to improve especially the pressure properties.

US. Pat. No. 2,861,043 concerns alkaline earth complex soap greases, preferably calcium complex soap greases, containing calcium salts of high molecular and low molecular fatty acids and inorganic salts (10 to 50 percent by weight of the complex soap). The inorganic salts contemplated therein include alkaline earth metal silicates. In column 2, lines 66 ff., it is stated that other possible additives to the thickening system may include Na PO Na I-IPO and Nal-I PO potassium phosphate, sodium borate, potassium borate. There is a minor excess of saponifying agent (hydrated lime) present. However, by recalculating the examples, it is shown to range below the value of 10 percent by weight of Ca(Ol-l) excess claimed herein as the lower limit.

German Offenlegungsschrift No. 1,444,926 describes a process for producing a complex grease proposing in combination the use of a low-molecular and a highmolecular acid as well as of a common soap thickener and further proposing the addition of aluminium oxides or aluminium hydroxides to the complex grease. The thickener is then worked up to a complex grease.

German Pat. No. 850,051 mentiones a process for producing high-pressure-stable, consistent lubricating greases based on oils and soaps, minor amounts of different inorganic salts being added to the consistent greases.

German Pat. No. 1,044,328 describes lubricating oils which are obtained from synthetic oils or mineral oils with a certain content of a complex metal soap. The complex metal soap should contain at least one metal soap of at least one high-molecular monocarboxylic acid and at least one low molecular monocarboxylic acid. British Pat. No. 875,732 discloses a lubricating grease mixture of lubricating oil, an inorganic gelling agent, and a small amount of a finely distributed alkaline earth salt of a carboxylic acid containing from 1 to 10 carbon atoms, German Pat. No. 1,594,587 proposes a lubricating grease based on mineral oil or on a synthetic lubrication liquid and organobentonite in order to solve this problem, the lubricating grease containing a carboxylic acid of high-molecular weight and of low molecular weight, both acids being capable of forming alkaline earth metal salts.

It is already known to produce practically anhydrous calcium soap lubricating greases by co-using calcium acetate, the greases comprising dropping pour temperatures up to about 300C. The term calcium complex soap grease" has become an acceptable term for such lubricating greases. These greases substantially consist of lubricating oil and a consistency-giving thickening agent, that is, calcium complex soap. Hereinafter, the term lubricating oil is used for mineral oils, fatty oils, synthetic oils, and for mixtures of agents of one or more of these materials. Fatty oils" are those greases and oils originating from fauna and flora which, substantially consist chemically of mixed glycerine esters of higher fatty acids having an even carbon number. The products obtained by chemical conversion, e.g., converted esters and partial saponification are related to this category of substance. The group of synthetic oils includes hydrophobic substances of liquid to pasty consistency, containing carbon, hydrogen, and oxygen. To this group belong, for example, those waste products from the production of alkyl benzenes which serve as wash raw materials basis, e.g., mixtures of compounds like diaryl-alkane, dialkyl benzene, aromates with longchain alkyl groups, etc. Beside the calcium soaps of normal animal, vegetable, or synthetic fatty acids, re spectively, having a carbon number above 3, the calcium complex soap contains calcium salts of fatty acids having a carbon number below 4, as well, especially calcium acetate. These fatty acids concern aliphatic saturated and unsaturated acids having branched and unbranched structures. Because of their high dropping points, the calcium complex soap greases are intended for lubrication uses at high temperatures. In practice, it was noted that the calcium complex soap greases often failed in the lubrication of antifriction bearings because running dry took place, a factor independent of the temperature of the bearing. The term running dry means that all lubricant between the touching, rolling or sliding parts has worn away, i.e., the bearing has run dry. This running dry causes overheating due to friction and usually, in consequence, a ruined or burned up engine.

It is not known which of the properties of a lubricating grease causes failure by running dry. Apparently, the concurrent forces of rheology of a lubricating grease and of its surface activity play an important but 7 still unknown part.

While this running dry of antifriction bearings can be observed in practice, it can be observed also on test runs. The SKF-Anti-Friction-Bearing-Lubrication- Testing Machine, according to German Technical Publication DIN 51 806, gives a limited bench test. The lubricating grease is tested under radial stress in two equal self-aligning roller bearings in said testing machine within a predetermined test time. A test-run B is conducted at 1500 rpm and under additional heating conditions.

SUMMARY OF THE INVENTION Unexpectedly, it has now been found that it is possible to produce a calcium complex soap lubricating grease substantially consisting of lubricating oil and calcium soaps characterized by an amount of calcium in the form of calcium hydroxide exceeding by from 10 to 60 percent by weight the amount required for saponification of those normal fatty acids or soap formers having a carbon number about 3 percent therein. An excess of from 30 to 40 percent by weight of calcium in the form of calcium hydroxide is preferred.

DISCLOSURE In a preferred embodiment of the invention a calcium complex soap lubricating grease, from 0.1 to 4.0 percent by weight of a salt mixture based on the total weight of the lubricating grease are added during the process of production. The salt mixture consists of phosphates and borates of the alkali group of the periodic system of elements. Adding the salt mixture, especially in the form of sodium salts, to the calcium complex soap lubricating grease leads to an improvement of special properties of the complex soap lubricating grease. It is to be understood that sodium phosphate means sodium salts of the o-phosphoric acid (H PO and of polymer phosphoric acids obtained therefrom by heating, all acid-hydrogen atoms being substituted by sodium. Sodium borate is to be understood as salts corresponding to sodium phosphates. The salts may either contain crystal water or can be free of it. In the salt mixture, the ratio of sodium phosphate to sodium borate can vary from 1:4 to 4: 1.

The improved calcium complex soap lubricating grease is especially adapted for lubricating antifriction bearings for high temperatures operation. For example, the calcium complex soap lubricating greases of the subject invention are suitable as antifriction bearing greases at bearing temperatures up to 220C.

The examples below illustrate in non-limiting fashion the present invention:

EXAMPLE I 200 kg (kilograms) of lubricating oil having a viscosity of 41 cSt/50C. are brought to a temperature of from about 50C to 60C. in a vessel with a stirring means. 63 kg of an animal fatty acid soap former having a neutralization number 202 and 88.5 kg of an animal neutral grease having a saponification number of 196 are introduced thereinto in a melted state. After adding 3 to 4 liters of water, 27.8 kg of calcium hydroxide, slurried in 40 kg of lubricating oil, and 59.3 kg of calcium acetate, slurried in kg of lubricating oil, are added to the batch. Then, further a mix of 5 kg of sodium o-phosphate and 5 kg of borax dissolved in water is added. Upon the temperature of the contents of the vessel increasing to between C. to 170C., an additional 428.4 kg of lubricating oil are added. Subse quently, the temperature of the batch is further increased to 250C. thereby forming the complex soap. After cooling off and homogenizing, a calcium complex soap grease having a penetration range of from 265 to 295 and having a dropping point of about 300C. according to German technical publication DIN 51 806 on the SKF-Antifriction-Bearing-Grease-Testing Machine. Even, after having been stored for a year, the grease did not show any appreciable change in its characteristics, especially as to the pentration and to the dropping point.

EXAMPLE II 150 kg (kilograms) of a naphthene based mineral oil of a viscosity of 50 cSt/50C. are heated together with 125 kg of oleic acid soap former in a vessel, as mentioned before, to a temperature of 60C. After reaching this temperature, 46.7 kg of calcium hydroxide, slurried in 60 kg of mineral oil. 41.3 kg of acetic acid, 6.5 kg sodium o-phosphate, and 2.5 kg of borax dissolved in water are added one after the other to the vessel. The vessel temperature then is increased to 200C., followed by the addition of 567 kg of mineral oil, the mineral oil being adjusted to a temperature of 120C. by a heat exchanger.

To form the complex soap, the temperature of the mixture is increased to 255C. After cooling the grease to a temperature of about 25C. followed by homogenization, a lubricating grease of NLGI-Class 2 is obtained having a dropping point of about 300C.

EXAMPLE III kg (kilograms) of a fatty acid soap former of animal origin (hardened blubber fatty acid) with a saponification number of 208 are saponified by adding 28.7 kg of calcium hydroxide in the presence of 350 kg of a paraffin base mineral oil having a viscosity of 40 est/50C., in a vessel at a temperature of 75C. This is followed by adding thereto 75 kg of calcium acetate and a mixture of 8.3 kg of sodium o-phosphate and of 3.9 kg of borax dissolved in water then, the temperature of the content of the vessel is increased to 250C.,

to form the complex soap. At a temperature of 175C.,

teristics after having been stored for one year.

6 total composition, of a complex of calcium soap of a normal fatty acid, or of a soap former having more than 3 carbon atoms in the molecule, and of a calcium salt of a fatty acid having from 1 to 3 carbon atoms wherein the ratio of the weight of said normal fatty acid or salt former to said fatty acid having less than 3 carbon atoms ranges from about 2 to 1 to about 3 to l; and 0.1 to 4 percent by weight of a salt mixture of alkali phosphates and alkali borates, Ca (0H), being present in said lubricating grease in an amount which exceeds by to 60 percent by weight that necessary for the saponification of said normal fatty acid, or said soap former having more than 3 carbon atoms in the molecule. 2. The composition of claim 1, wherein the excess of Ca(Ol-I) ranges from to percent.

3. The composition of claim 1, wherein said salt mixture consists of sodium phosphates and sodium borates.

SHELFLIFE OF SEVERAL CALCIUM COMPLEX SOAP LUBRICATING GREASES COMPOSITIONS IN WEIGHT PERCENT Tallow Ca(OH l. A lubricating grease composition effective as an antifriction grease at temperatures up to 220C, consisting essentially of a major amount of a lubricating oil; of from about 20 to 35 percent by weight, based on the No. Talgol fatty acid Ca-acetate Excess Shelflife Borax Na-phosphate SNOZO" 9041" Ca(OH) afler 3 yrs.

in wt.%

07 I very strongly (Ex. V11) 6.0 6.0 1.7 6.0 80.3 7 hardened 08 1 (Ex. V) 6.0 6.0 2.18 6.0 79.82 37.5 little hardened 09 6.0 6.0 2. I 8 6.0 0.34 0.68 78.80 37.5 no change 10 6.0 6.0 1.7 6.0 80.3 7 very strongly hardened 1 1 6.0 6.0 2.18 6.0 79.82 37.5 little hardened 12 6.0 6.0 2.18 6.0 0.34 0.68 78.80 37.5 no change 68 (Ex. V1) 6.0 6.0 2.51 6.0 79.49 60 little hardened 69 6.0 i 6.0 2.51 6.0 1.5 1.5 76.49 60 no' change 70 6.0 6.0 2.51 6.0 2.0 2.0 75.49 60 no change 88 very strongly (Ex. IV) 6.0 6.0 1.57 6.0 80.43 hardened "SN0 20 Solvent Neutral Oil. parafllnic 9041 Machine Oil Rufl'lnute. nuphthenic We claim: 40

4. The composition of claim 1, wherein said salt mixture consists of sodium phosphates and sodium borates in the ratio of weight of from 1 4 to 4:1.

* IIK

Claims (4)

1. A LUBRICATING GREASE COMPOSITION EFFECTIVE AS AN ANTIFIRICTION GREASE AT TEMPERATURE UP TO 220*C, CONSISTING ESSENTIALLY OF A MAJOR AMOUNT OF A LUBRICATING OIL, OF FROM ABOUT 20 TO 35 PERCENT BY WEIGHT, BASED ON THE TOTAL COMPOSITION, OF A COMPLEX OF CALCIUM SOAP OF A NORMAAL FATTY ACID, OR OF A SOAP FORMER HAVING MORE THAN 3 CARBON ATOMS IN THE MOLECULE, AND OF A CALCIUM SALT OF A FATTY ACID HAVING FROM 1 TO 3 CARBON ATOMS WHEREIN THE RATIO OF THE WEIGHT OF SAID NORMAL FATTY ACID OR SALT FORMER TO SAID FATTY ACID HAVING LESS THAN 3 CARBON ATOMS RANGES FROM ABOUT 2 TO 1 TO ABOUT 3 TO 1, AND 0 TO 4 PERCENT BY WEIGHT OF A SALT MIXTURE OF ALKALI PHOSPHATES AND ALKALI BORATES, CA (OH)2 BEING PRESENT IN SAID LUBRICATING GREESE IN AN AMOUNT WHICH EXCEEDS BY 10 TO 60 PERCENT BY WEIGHT NECESSARY FOR THE SOPONIFICATION OF SAID NORMAL FATTY ACID, OR SAID SOAP FORMER HAVING MORE THAN 3 CARBON ATOMS IN THE MOLECULE.

2. The composition of claim 1, wherein the excess of Ca(OH)2 ranges from 30 to 40 percent.

3. The composition of claim 1, wherein said salt mixture consists of sodium phosphates and sodium borates.

4. The composition of claim 1, wherein said salt mixture consists of sodium phosphates and sodium borates in the ratio of weight of from 1 : 4 to 4:1.