US2613182A - Keto-acid soap greases - Google Patents

Description

Patented Oct. 7, 1 952 UNITED" STATES PATENTYOFFICE inrro acin 80A GREASES Lorne W. Sproule, Warren Pattenden, and

Laurence F. King, Sarnia, Ontario, Canada, as-

signors to Standard Oil Development Company, a corporation of Delaware I i No Drawing.

Serial No. 137,030

7 Claims, (01. 252-39) The present invention relates to lubricating grease compositions and, particularly, to lubricating greases containing soaps of keto acids of the long chain monocarboxylic'type.""The inven-- tion has special application to calciumsoap greases based on such acids, but is not necessarily limited thereto.

Lime soap greases as a class are an important type of lubricants. They are widely used in-in dustry because of their smooth texture and their structure stability at ordinary temperatures. They are economical and are easily made and for this reason they are used for a majority of applications where high temperatures are never encountered. They are somewhat deficient, however, where temperatures approaching or exceeding the boiling point of water are encountered, because lime greases rely upon the presence of a small amount of Water to maintain their true colloidal grease structure. If this water is evaporated, as may occur at moderately high temperatures, the greases become grainy, the oil sep arates from the soap, and failure of-lubrication" promptly ensues. i a

It has previously been suggested that lime soap greases might be modified in various ways toimprove somewhat their high temperature properties. Thus, it has been suggested that a compleX soap be substituted for the conventional soap of straight fatty acids, for example, by introducing a metal acetate or other low molecular weight water-soluble salt which forms a complex with the normal fatty acid soap'and improves high temperature stability. It has also been-suggested by the present inventors in'a previous application, Serial No. 81,206 filed March 12, 1949, that a calcium base grease containing 12-hydroxy stearic acid 'might' have improved high temperature properties.

It has now been discoveredthat greases made from keto-acids of the long chain type, for, example, monocarboxylic acids having not less than 12 nor more than 22 carbon atoms, have outstanding high temperature properties. The

mono-keto-acids are specifically preferred. ,Apj parently, the presence of the keto group stabilizes lime soap greases in the same manner that the presence of a small amount of water stabilizes the conventional prior art products. The keto group, however, is not afiected by a rising temperature and the product remains stable where the conventional lime base grease would disintegrate upon evaporation of its normal water content. The proportions of soap to be used in such a grease tend to run somewhat higher than those of conventional lime soaps, but, in general, proportions from 5% to 30% of lime soap, based on the weight of the total composition, appear to be operable. Specifically, proportions of 10 to about 25% are preferred. The soap may contain other constituents but preferably is preponderantly the soap'of one or more of the keto-acids coming within the description given above. Thus; commercially available products, or products which'can readily be prepared from conventional rawmaterials may contain other acids such as hydroxy acids ornormal fatty acids along with a major proportion of the keto-a-cid product. The keto-stearic acids are particularly suitable, e. g. l2-ketow-stearic acid, ll-:eto-stearic acid, and various other isomers.

The invention may more fully :be understood by reference to the: following specific example:

Example A grease was prepared by heating 20 parts by weight of a lz-keto-stearic acid, 20 parts of mineral base lubricating oil, and 2.7 parts of hydrated lime. These ingredients were cooked to a temperature of 250 F; and thereafter additional lubricating oil of mineral base was added, together with 1 or 2% of water, until the soap content approximated about 22% ofthe weight of,the finished grease. The product thereafter was cooled to about 180 F. and packaged. It showed the following inspection:

Keto-Stearic Acid Grease Soap Content, Percent 22 Worked Penetration 77 F Free Acid, Percent Free Alkali, Percent Dropping Point, F

Water Resistance-Percent" Water Absorbed at F.

265 F.nil 150 F.nil. Temperature at which Grease 280 F.trace. F.-trace Separates 290 F.1% 180 F.-39%.

305 F.l4% .r

1 100 grams of grease are placed in agrease worker. 20 c. c. of water is'addecl and worked for 300 strokes. If no free water is present, an

from glacial acetic acid, the final product hav- The reaction product was recrystallized ing an acid number of 186. The product was analyzed and found to contain 89% by weight of 12-keto stearic acid and 11% of 12-hydroxy stearic acid.

The table above shows comparisons between the product of the example and a standard commercial lime soap grease of about the same consistency. The soap used in the commercial grease was a mixture of calcium oleate and calcium stearate. It should be noted, as previously indicated, that the soap content of keto-stearic acid grease is higher than that of the commercial product, about 22% of l2-keto stearic acid soap producing a grease of the same consistency as 13% of standard lime soap. In larger batches, the difference is not quite as great, the soap content being more nearly equal, but it appears that somewhat more soap of the keto-acid type is required than of standard fatty acid soaps to produce a product of a given consistency.

The product of the example, it will be noted, had a melting or dropping point of 290 F., whereas the conventional lime grease melted at 195 F. Both showed excellent water resistance, but at 180 F. the conventional grease showed serious oil separation while the keto stearic acid grease showed only 1% separation at 290 F. Since oil separation quickly results in a failure of the lubricant, it is evident that this is an extremely important consideration where high temperature operation is involved. In this respect, greases prepared from l2-keto stearic acid are much superior to conventional lime-stearic acid greases.

While the above example is limited to a particular keto stearic acid, it will be understood that related products derived from palmitic, myristic, and lauric acids, or from the C20 and C22 fatty acids and the corresponding. glycerides, may all be used. Mixtures of them may be used also, the choice of soap stock depending upon the degree of saturation required (which is dependent upon the desired resistance to oxidation, etc.) the softness or hardness of the soap, which is dependent upon the chain length to some extent, and the like as suggested above. Satisfactory soaps have been prepared from 4-keto stearic acid. derived from hydrogenated oiticica oil but various isomers and homologs may be used within the above stated limits.

While lime is the preferred saponifying agent, other metal bases may be used of the alkali metal and alkaline earth metal groups. The greases also may contain soaps of other acids, in minor proportions, and the usual modifiers, such as antioxidants, tackiness agents, extreme pressure additives, viscosity index improvers, and the like, may be included in conventional proportions, as will be evident to those skilled in the art.

In general, the products are prepared by combining about 1 to 2 parts of the aliphatic monoketo fatty material, which may be either the fatty acid or the corresponding glyceride ester, with 1 to 2 parts by weight of the mineral base lubricating oil. A sufficient quantity of the metal base saponifying agent is added to saponify and substantially neutralize the fatty material. These ingredients are heated to saponification temperature between about 200 and 300 F. Thereafter, further quantities of oil are added, from 2 to 10 parts by weight, depending upon the consistency desired in the finished product. This additional oil is preferably a mineral base oil, but synthetic oils, such as the conventional dibasic acid alkyl esters or the polyglycols, or mixtures thereof, with each other and/or With mineral base oil, may be employed. As is well-known in the art, the esters are not very suitable for forming the original soap in situ, and when an ester base grease is desired the soap should be preformed independently or should b formed in mineral oil which does not hydrolyze during the saponification.

Soaps of the keto-acids may be preformed in much the same manner as conventional soaps and by the use of suitable homogenizing equipment these may be incorporated into lubricating oils, like other preformed soaps, to prepare the greases. The formation of the soap in situ, as described in detail above, is usually preferred.

What is claimed is:

1. A lubricating grease composition comprising a major proportion of lubricating oil thickened to a grease consistency with a minor proportion of a metal soap of 12-keto stearic acid.

2. A lubricating grease composition comprising a mineral base lubricating oil thickened to grease I consistency with a soap of a metal selected from the alkali and alkaline earth metals, said soap being predominantly of lz-keto stearic acid.

3. Composition according to claim 2 wherein the metal soap is a lime soap. 1

4. Composition according to claim 1 wherein the metal soap is a lime soap.

5. The process of preparing a lubricating grease which comprises combining about 20 parts by weight of mineral base lubricating oil, about 20 parts of an aliphatic monocarboxylic acid which is predominantly 12-keto stearic acid, and about 2.7 parts of hydrated lime, heating the mixture to a temperature of about 250 F. for a time sulficient to substantially complete saponification to form a grease thickening soap, and thereafter adding additional lubricating oil and cooling to form a grease of 5 to 30% soap content by weight.

6. A lubricating grease composition consisting essentially of mineral base lubricating oil thickened to a grease consistency with 5 to 30% by weight, based on the total composition, of the lime soap of an acid composed substantially of 11% by weight of 12-hydroxy stearic acid and 89% 12-keto stearic acid.

7. Composition according to claim 6 having asoap content of about 22% by weight.

LORNE W. SPROULE. WARREN C. PATTENDEN. LAURENCE F. KING.

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

UNITED STATES PATENTS

Claims (1)

1. A LUBRICATING GREASE COMPOSITION COMPRISING A MAJOR PROPORTION OF LUBRICATING OIL THICKENED TO A GREASE CONSISTENCY WITH A MINOR PROPORTION OF A METAL SOAP OF 12-KETO STEARIC ACID.