US2576031A - Lubricating grease containing soaps of tall oil - Google Patents

Description

- used in the earlier product.

Patented Nov. 20, 1951 LUBRICATIN G GREASE CONTAINING SOAPS OF TALL OIL Arnold J. Morway, Rahway, and John J. Kolfenbach, Somerville, N. J., assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application April 9, 1949, Serial No. 86,586

7 Claims.

The present invention relates to lubricating greases and particularly to lubricating greases which contain as thickening agents mixtures of high and low molecular weight metal salts of organic acids.

In an application Serial No. 57,565 filed October 30, 1948, by Morway and Young, now Patent No. 2,516,136, of which one of the present inventors was a co-inventor, there is disclosed a new type of lubricating grease composition which is particularly suitable for hightemperature lubrication. The grease in question combines salts of heterocyclic acids with conventional soaps, for example the soaps of hydrogenated fish oil acids having an average chain length in the fatty acid radical of about 18 carbon atoms, or, more broadly, 14 to 22 carbon atoms. The patent points out that furoic acid may be added to the fatty acids in the presence of mineral oil and neutralized to form the salt and the soap and these are simultaneously dispersed in the mineral'oil to form lubricating grease. The saponifying agent, for example sodium hydroxide, forms a sodium furoate along with the usual sodium soap. The patent points out that other cyclic acids of comparable molecular weight and structure may be used in lieu of furoic acid. For example, derivatives of thiophene may be used and the salts of other low molecular weight acids having similar properties are contemplated.

The present invention is based upon the discovery that greases of the general type set forth in said patent may be produced very economically by substituting tall oil for the fatty oils or acids Certain unexpected advantages accrued from such use and constitute a major aspect of the present invention, as will be more fully pointed out hereinafter.

In another copending application Serial No. 60,615 filed November 17, 1948, by the present applicants, now Patent No. 2,518,137, a process for preparing high temperature lubricating greases is described wherein furoic acid salts and analogous materials are produced in situ by using an aldehyde which is converted first into an acid and then. into a salt by the well-known Cannizzaro reaction. In the present case, lubricating greases may be prepared by the same process, the essential difference being that tall oil is used in lieu of conventional fatty acids, the salts of low molecular weight being produced by the Cannizzaro reaction which results when aldehydes such as furfural or thiophene aldehyde, benzaldehyde, and the like, are treated with a strong base such as sodium hydroxide.

In recent years, supplies of fats and fatty acids have at times been scarce and in some cases almost unobtainable. Hydrogenated fats and fatty materials have been used to some extent to pro- .vide saturated or substantially saturated materials which are preferred for grease making, but in many instances these materials have not been available or, if available, have been prohibitive in price. According to the present invention, tall oil which is a relatively cheap by-product of the wood pulp industry may be used to form materials which replace conventional fats and fatty acids totally or in part in forming the soap ingredient of lubricating greases of the type under discussion. Thus, lubricating greases containing the soaps of tall oil, particularly the alkali metal soaps and especially the sodium soaps, are particularly effective in combination with the corresponding salts of the lower cyclic acids, e. g. those containing 4 to about 7 carbon atoms such as furoic acid, thiophene carboxylic acid, benzoic acid, salicylic acid, and the like. To some extent tall oil soaps may also be combined with other low molecular weight salts than the furoates, e. g. with acrylates, acetates, and other lower aliphatic salts.

In the preparation of greases of this character, the cyclic or other low molecular weight acid may be added directly to the composition if the Cannizzaro reaction is not desirable, or if the aldehydes are not available. In many cases, the use of the corresponding aldehyde, particularly furfural, is justiiied economically as a source of the low molecular weight acid which forms the salt component. because of the availability and cheapness of this material. When the neutral or substantially neutral salts and soaps are derived from relatively inexpensive aldehyde and the relatively inexpensive tall oil, either as the principal or as the total thickening ingredients, the resulting grease product is quite inexpensive and has very useful properties. Tall oil acids or tall oil saponified with sodium hydroxide and dispersed in mineral oil gives greases of low dropping point, undesirably fibrous, and poor oxidation and structural stability.

The addition of the cyclic acid salt in combination with soaps of tall oil acids, improves the oxidation stability far beyond that obtained with tall oil soap alone in greases. In fact the furoic acid salt appears to act as a synergist for the commonly used oxidation inhibitor phenyl alpha naphthylamine. High dropping point, smooth short fiber structure and excellent structural stability are also obtained.

The mere addition of the sodium salt of Iuroio acid in combination with either a Simple sodium linoleate or a. simple sodium oleate, both components of tall oil acids, do not give greases of good structural stability. Moreover, in the past, the rosin acids which are an important ingredient in the conventional tall oil of commerce were believed to be objectionable. However, when tall oil is used in combination with the furoic acid salts it appears that small quantities of rosin acid soaps which result are beneficial. However, no atttempt is made here to explain the behavior mechanism in the performance of such greases.

Furfural is a widely available and inexpensive material, widely used as a selective solvent in industry. Tall oil is a by-product of the paper pulp industry as noted above. Another by-product obtained in the sulfate-paper process is sulfate turpentine, a product objectionable for use in lubricants because of its odor and color. Trimble, in U. S. Patent 2,310,046, describes the refining of sulfate turpentine simultaneously with crude tall oil by using furfural. Separation of the turpentine and tall oil is accomplished by distillation under reduced pressure. Any furfural remaining in the tall oil, either as the monomer or polymer, may be determined and this residue may be left in the refined tall oil. Upon saponification of the tall oil the salts of furoic acid are also produced. Sufficient furfural may be added if needed, to form the required proportions of low molecular weight salts required for the grease.

Any commercial type of tall oil acids may be employed in carrying out this invention. However, the acids obtained by at least one complete distillation of the crude tall oil are preferred.

The invention will be better understood by reference to the following specific examples:

EXAMPLE I Charging formulation Per Cent Free Alkalinity-0.22% as NaOH.

In the manufacture of this grease, the furfural (1 part by weight) and a portion of the mineral oil (3 parts) were charged to a grease kettle and stirring initiated. A cold aqueous 33 solution of NaOH (shown in the above formulae as part of the Cannizzaro reactions) was next added. After the reaction is completed as shown by subsidence of the temperature of reaction, the tall oil (having an acid number of 183.2 and Sap. No. of 185.2) was added and neutralized with the balance of the NaOH as a 40% aqueous solution.

The temperature was next raised by external heating to 400 F. while adding the balance of the mineral oil in small portions. At this tem- 'peraturethe phenyl alpha naphthylamine, used as an antioxidant, was added and the grease was drawn into pans for cooling. It could be worked down in the kettle while cooling if desired. The cold grease was then homogenized by working in the grease kettle to a smooth, uniform product, after which it was filtered and packaged. This grease contained about 6% sodium furoate and about soda soap of tall oil.

' '4 The following properties were found upon inspection:

Worked penetration 180 mm./10. Structure stability, as measured by a penetration of 268 mm./10 after working 100,000 strokes with a fine hole worker plate Excellent. Dropping point, F Above 500. 50 hour separation test, 60 mesh cone at 210 F. (per cent separation) None. Wheel bearing test, 6 hours at 220 F Pass. Oxidation test, Norma Hoffman bomb 102 hrs. to 5 p. s. i.

drop in pressure. 1 No slumping, no oil separation, slight hardening.

position of poor structural stability resulted. The composition lost its solid consistency and broke down after working in a standard grease worker for 50,000 strokes to a semifluid mass which could be poured.

EXAMPLE III The same formula as shown in Example I was used and the same method of manufacture, except that the tall oil employed contained more rosin soap, having the following chemical and physical properties:

Acid value 175.0 Composition (approx.) fatty acids as oleic and linoleic acids per cent 30 Rosis acids do 70 In this example the tall oil was mixed with equal portions of hydrogenated fish oil acids (HydIOfOl Acids 54) Properties of Grease Free alkalinity 0.32% as NaOH. Worked penetration mm./ 10 210. Structural stability Excellent. (Penetration a f t e r 100,000

s t r o k e s fine hole worker plate) 248. Dropping point F 500+.

Separation (50 hours at 210% None. Wheel bearing test 6 hours at Pass.

220F hours 5 Norma Hoffman oxidation p. s. 1. drop in (210 F.) ()2 pressure.

1 Same as in Example I.

The proportions of the various ingredients may be varied over wide limits provided that the ratio between the low molecular weight salt and the soap of tall oil is maintained between predetermined limits. A very satisfactory modified soap may be made by using substantially equal parts of saturated fatty acids, such as C12 to C22 hydrogenated fish oil acids, with tall oil. As pointed out in the Morway and Young, Patent No. 2,516,136, referred to above, 1 to 3 molar parts of soap should be used with about 1 to 2 molar parts of salt. When employing the Can nizzaro reaction as disclosed in Patent No. 2,516,- 137, mentioned above, 2 parts of furfural can be used with 3 parts combined fatty acid and/or tall oil. Since tall oil consists essentially of a mixture of rosin acids and oleic acid the soaps which result are partly rosin soaps and partly oleates. The total proportions of such soaps, however, may be within the limits of about 5 to 20% by weight, based on the total composition, the salt of low molecular weight acid being in proportions of about 2 to generally speaking. Proportions of 3 to 7% salts of cyclic acid (such as furoic acid) combined with 8 to of the soaps of tall oil acids are specifically preferred, the remainder of the composition being lubricating oil.

The grade of mineral oil may be varied over wide limits as is well-known in the art. It may comprise from about 60 to 93% of the total composition and should be of appropriate lubricating grade for the' lubrication requirements. Its viscosity may be from about S. U. S. to about 150 S. U. S. at 210 F. or about 50 to 1,000 S. U. S. at 100 F. Either naphthenic or paraffinic oils, or mixtures thereof, may be used.

Conventional additives such as antioxidants, oiliness agents, corrosion inhibitors, extreme pressure compounds, and the like, may be used in usual proportions, as will be understood by those skilled in the art. While mineral base oils are preferred, they may be supplemented by or compounded with synthetic oils such as the oily esters of dibasic acids, polyglycols, and the like. The term lubricating oil as used in the following claims will be understood to apply to any of such oils or a combination thereof where not otherwise specified. Where the Cannizzaro reaction is not employed, the salts and soaps may be formed separately and combined in the oil. or they may be formed in situ as may be desired. If the Cannizzaro reaction is employed, both the soap and the salt of the cyclic acid should be prepared in situ and preferably simultaneously.

What is claimed is:

l. A lubricating grease composition consisting essentially of lubricating oil thickened to a grease consistency with a combination of 5 to 20% by weight based on the total composition, of the sodium soap of tall oil combined with 2 to 10% of the sodium salt of a low molecular weight cyclic carboxylic acid containing 4 to about '1 carbon atoms.

2. Composition as in claim 1 wherein the cyclic acid is furoic acid.

3. Composition as in claim 1 wherein the cyclic acid is thiophene carboxylic acid.

1 4. Composition as in claim 1 wherein the salt of low molecular weight acid is a benzoa'te.

5. A lubricating grease composition consisting essentially of to 93% by Weight of mineral base lubricating oil, 5 to 20% of a soda soap of tall oil and 2 to 10% of sodium furoate.

6. A lubricating grease composition consisting essentially of mineral lubricating oil having a viscosity between 35 and S. U. S. at 210 F., thickened to a grease consistency with a combination of about 15% by weight, based on the total composition, of the soda soap of high molecular weight organic material of the class consisting of higher saturated fatty acids and their esters and tall oil and comprising a substantial proportion of tall oil and about 6% of sodium furoate.

7. Composition as in claim 6 wherein the nonmetal radical of the high molecular weight soap is composed of substantially equal parts of substantially saturated fatty acids of 12 to 22 carbon atoms and tall oil.

ARNOLD J. MORWAY. JOHN J. KOLF'ENBACH.

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

UNITED STATES PATENTS Number Name Date 2,182,137 Ricketts Dec. 5, 1939 2,444,720 Bell July 6, 1948 2,514,286 Morway July 4, 1950 2,516,136 Morway et a1. July 25, 1950 2,516,137 Morway et ,1 July 25, 1950

Claims (1)

1. 6. A LUBRICATING GREASE COMPOSITION CONSISTING ESSENTIALLY OF MINERAL LUBRICATING OIL HAVING A VISCOSITY BETWEEN 35 AND 150 S. U. S. AT 210* F., THICKENED TO A GREASE CONSISTENCY WITH A COMBINATION OF ABOUT 15% BY WEIGHT, BASED ON THE TOTAL COMPOSITION, OF THE SODA SOAP OF HIGH MOLECULAR WEIGHT ORGANIC MATERIAL OF THE CLASS CONSISTING OF HIGHER SATURATED FATTY ACIDS AND THEIR ESTERS AND TALL OIL AND COMPRISING A SUBSTANTIAL PROPORTION OF TALL OIL AND ABOUT 6% OF SODIUM FUROATE.