US2403104A - Lithium greases - Google Patents

Description

Patented July 2, 1946 LITHIUM GREASES Elvln B. Lien, Berkeley, Calif., asaignor to Union Oil Company of California, Los Angeles, Calit, a corporation of California No Drawing. Application October 17, 1942,

Serial No. 462,413

13 Claims. 1

-This invention relates to lubricating greases, and the principal object thereof is to p odu a stable lubricating grease tree from tendency to bleed" and to increased starting and running torque at low temperatures, and which is at the same time both water-resistant and stable to temperature fluctuations and pressure changes.

Primarily, the invention resides in a lithium soap grease which is rendered particularly suitable for extremely low temperature use, wherein the low temperature. properties are imparted through the presence of a small proportion, e. g. 5%, of a so-called unsaponifiable oil obtained as a by-product from the production of soaps from acidic materialsproduced by oxidation of highly parafflm'c petroleum lubricating oil. Also, the lithium soap grease produced under this invention is rendered particularly stable against leakage of oil or tendency to bleed or weep. Furtherinore, such products are found to be appreciably improved in physical appearance in that they are unusually clear and brilliant in comparison with greases not containing the unsaponifiable oil.

The lithium soap used in the grease may be prepared in any known or preferred manner from any appropriate fatty acid or other soap-making acidic material suitable for grease manufacture.

For example, asuitable grease may be made from lithium stearate which is produced in any appropriate manner from commercial stearic acid, such as by reacting lithium carbonate or other suitable lithium base withstearic acid. Similarly, other fatty acids such as oleic acid, palmiticacid and the like or mixtures of these acids may be used according to well understood soapmaking procedure. n Thus, both animal and vegetable fatty acid may be employed.

These lithium soaps may be employed in suit-.

able mineral lubricating oils in varying proportions according to the particular type of grease desired. Normally, the stiffer the grease desired, the greater the soap proportions. Whereas, a

I thin grease might contain only 1% or 2% 0! the soap, heavier-bodied greases will contain from 4% or 5% of soap up to 10% or 15% or any other desired proportion. Such greases have been described in patents. issued to Clarence E. Earle Nos. 2,274,673, 2,274,674, 2,274,675 and 2,274,676, I

and various acidic materials appropriate therefor are indicated in those patents. In addition it may be desirable for some uses to use other acidic materials such as naphthenic acids derived from petroleum whereby lithium naphthenates are produced. It may also be desirable for some pur- 2 i poses to employ synthetic acids produced by oxidation of lubricating oils, or the sulfonic acids obtained as a. by-product in the manufacture of white oils.

The present improvement renders greases of this type thoroughly stable, especially for low temperature uses such as for airplane lubrication, and protects them against a tendency to leak or "bleed some of the oil, especially where it is important to use low viscosity lubricating oils. This tendency is controlled or completely overcome by the employment therein of a small percentage, such as 5%, of the indicated unsaponiflable oil or oily material which is recovered in connection with the production of metal soaps from the oxidation products of the modern highly parafilnic lubricating oils such as those which are produced by solvent extraction of paraffin about 50 lbs. and 200 lbs. A typicaloperation is to air-blow at a temperature of about 320 F. and

under a pressure of lbs. gage. Air blowing is carried on for a, time to produce commercially maximum oxidation or other substantial degree of oxidation. The oxidation batch which then.

contains substantial amounts of acidic materials, as indicated by a typical saponification value of 80, is then reacted with sodium hydroxide, or other suitable base at a temperature of 250 F. and a pressure of 60 lbs. per square inch, to form the desired sodium soap or other desired metal salt. Separation of the unsaponifiable oil is realized by mixing the sodium soap and oil with a quantity of water, e. g. 25% water, heating the batch to around 180 F. to 200 F., agitating, and allowing the whole to settle. The soap layer settles to the bottom leaving an emulsion layer in the middle and a relatively clear unsaponifiable oil ontop. The soap and emulsion layersare easilyseparated from-the unsaponifled oils which "consist principally of unoxidized hydrocarbons,

It has been discovered that when minor proportions or this oil are used in the lubricating oil employed in the grease production, an otherwise present tendency of the grease to bleed out some of the oil is overcome. This function is especially desirable where low viscosity oils, such as transformer oils or very light lubricating oils are employed for the grease production. In addition to reducing this sweating tendency, the described unsaponifiable oil also imparts appreciable physical difierence in that the product containing the unsaponifiable oil is clearer and almost transparent, as distinguished from a grease The amount of saponifiable oil may vary from the indicated For example, as little as about 2% is efi'ective in lowering torque, reducing bleeding of oil, and rendering the product I clearer. Again, larger proportions such as 6% or 30 improve compatibilty.

8% may be introduced with increase in the desirable effects, up to an unsaponifiable oil content of about 10%, beyond which-there does not appear to be a constantly'increasing appreciable improvement. However, at least for some uses, it

-is possible to replace all of the lubricating oil or of mixed base, as desired, and obviously, the

viscosity .of the oil will vary with the grease required.

In connection with avoidance of torque increase at low temperatures tests were made with a test shaft rotating in a'packed bearing and under a constant force, using greases made with transformer oil, as in the following table:

Composition Grease T Sfeconds Trans. em or one 0mm, Lithium 5; p rotation on stearate on Percent Percent P F.

5.7 None 67 1,300 5.7 5.0 67 430 0.0 None -55 1,000 9.0 5.0 -s5 120 This shows a reduction in torque to about onethird where substituting 5% unsaponifiable' oil in same A to produce sample B and a reduction to about-one-eight where making a similar substitution in sample!) (where the soap content is greater) to produce sample D. In zaddition to employing the described unsaponifiable oil for the purposes indicated, it is SAE grades from inasmuch as there is sometimes a tendency for lithium greases to darken substantially after manufacture. A very desirable material for this purpose has been found to be phenyl alpha naphl thylamine. An adequate proportion is about 0.2%

of the grease, but this may be varied according to the extent of control desired from perhaps as little as 0.05% to perhaps as much as 1.0%, although greater proportions than 1.0% can be 19 employed, if desired, to further increase the oxidation resistance of the grease. Another suitable anti-oxidant is p-phenylene diamine. Also,

other high boiling point 'arylamines and other inhibitors may-be'emplo'yed in somewhat similar proportions.

In addition to employing lithium soaps, such as lithium stearate, there are occasional instances where it seems desirable to add smaller proportions of other soaps. For example, about 20 to 2% of calcium stearate, sodium stearate, magnesium stearate, or especially aluminum stearate,

or soap or similar acid, may be added to a grease containing in the order of 10% of lithium stearate. Similarly, small proportions of these additional soaps maybe addedto greases containing either less or more lithium stearate, such as to greases containing 4% or 5% of lithium stearate or other lithium soap. The purpose of these.

additions, when desirable to employ them, is to Variations in the product and in the method of its production will be apparent to those skilled in the art. For example, the compatibility-improving soaps may be prepared from any acid 36 previously mentioned for 1ithium=soaps. I

v I claim: v 1 I v 1. A lubricating grease comprising mineral oil,

a minor proportion of lithium soap, and a minor proportion of unsaponifiable oil obtained from 40 the recovery of synthetic acids produced by the oxidation of lubricating oil fractions. 2. A lubricant comprising mineral lubricating oil, about 1% of lithium soap, and a minor proportion of unsaponiflable oil obtained as a byproduct after recovery of synthetic acids produced bythe oxidation of a petroleum lubricatin oil fraction.

3. A lubricant comprising a petroleum fraction of lubricating viscosity, a minor proportion of lithium-soap to thicken the oil, and a minor flcient to reduce tendency to increase torque at sub-normal temperatures.

4. A lubricant according to claim 3 wherein the unsaponifiable oil is present in excess of about 2% of the total composition. I so 5. A lubricant according to claim 3 wherein the soap is present in proportion in excess of about 1% and the unsaponiflable oil is present in excess of about 2%.

6. A lubricating grease comprising a mineral 5 oil fraction having lubricating viscosity, a minor proportion of lithium soap to thicken the oil, and a minor proportion uflicient to prevent bleeding oi unsaponiflable oil obtained after separation of synthetic acids produced by' the oxidation 01' a refined petroleumfraction.

'7. A lubricant comprising a petroleum frac tion of lubricating viscosity, 9. minor proportion between about 1% and 25% of lithium soap, and I a minor proportion between about 2% and 1 sometimes desirable to add an oxidation inhibitor, of unsaponifiable oil obtained after separation of synthetic acids produced by the oxidation of re- 10. A lubricant according to claim 3 contain ing phenyl alpha naphthyiamine in a minor proportion sufllcient to act as an oxidation inhibitor. 11. A lubricantaccording to claim 3 containing a minor proportion suflicient to act as a compatibility agent of a soap 0! the class consistin oi! calcium, sodium, magnesium and aluminum soaps. 4 v

12. A lubricant according to claim 3 containing a high boiling oint aryl amine in minor proportion suflicient to act as an oxidation inhibitor.

13. A lubricant according to claim 2 wherein the unsaponiflable oil is present in proportion suiiicient to reduce tendency to increased torque at subnormal temperatures.

- ELVIN 28. HEN.