US2468098A - Grease composition - Google Patents

Description

Patented Apr. 26, 1949 UNITED 2,468,098 GREASE COMPOSITION Arnold J. Morway, lark Township, Union County, N. 1., and Cloyce R. Daniels, Pittsburgh, Pa., assignors to Standard Oil Development Company,

Delaware a corporation of No Drawing. Application February 18, 1948,

I Serial No. 9,315

The present invention relates to high melting grease and particularly to soda. base greases and related compositions which have good resistance to water in addition to desirable high melting properties. The invention also contemplates an improved method for the production of sodium base greases, and other related compositions, so as to improve their high temperature and water resistant properties.v

In the prior art, the sodium base greases have been widely used for lubrication at fairly hightemperatures where moisture conditions are not particularly severe. These greases have good lubricating properties at elevated as well as at normal temperatures and, as a rule, they are easily handled and dispensed in standard grease dispensing equipment, except for the very heavy greases of high soap content, such as those con- 11 Claims. (Cl. 252-332) I composition having the 'taining about 45% sodium soap, which are tough I usually have relatively high melting points de- 1 pending upon the amount of soap present. Normal sodium greases suitable for general bearing service have dropping or melting points of the order of about 360 F. Due however to changes in grease structure below the droppingpoint,

such greases are generally suitable for use at bearing temperatures not greater than about 250 F. Hence such greases have generally been considered unsatisfactory for elevated temperature use where the design of the mechanical parts is such that a liquefied grease is unsatisfactory.

The present invention is based upon the discovery that by the use of certain low molecular weight preferably saturated organic hydroxy acids the melting or dropping point of soda soap greases may be materially raised to about 450 to 500 F. without excessive changes in their structure.

For the purposes of the present invention the lower saturated aliphatic hydroxy acids, such forming reaction to cease.

as glycolic acid and lactic acid, and the like, ap-.

added either prior to or during saponification but it is convenient and preferable to add it to the saponifiable fatty acid before saponification.

It is also desirable though not necessary to add a small quantity, 0.01 to 5% of a suitable sulfonate, such as sodium sulfonate, to improve the texture and mechanical stability of the composition. The temperature stability as well as the mechanical stability of such greases may be further improved by using a particular method of processing as will be set forth more fully below.

In order to determine the relative values of low molecular weight hydroxy aliphatic acids for raising the melting points and improving the water resistant properties of lubricating greases a following ingredients was prepared:

' v Per cent Fatty acids (oleic acid or hydrogenated fish oil acid) L 17 to 18 Low molecular weight organic acid 2 to 3 Sodium hydroxide; 4.5 Mineral lubricating oil, 50 S. S. U. at

210 F., V. I. 79 73,5 Sodium sulfonate or oil soluble sulfonic acids 2.0

The fatty acid was first mixed with the low molecular weight acid and with the sodium sulfonate, or other sulfonate, in a concentrated mineral oil solution. To these ingredients was added an equal weight of the mineral oil and the mixture was heated to a temperature of F. accompanied by stirring. Thereafter the sodium hydroxide in the form of a 35% aqueous solution was added to the mixture and heating and stirring were continued until the resulting composition was nearly completely dehydrated or at least until the mixture became so heavy as to require the addition of more mineral oil to facilitate stirring. Thereafter, the remainder of themineral oil was added a small portion at a time and the temperature was gradually increased to about 400 F. Heating and stirring were further continued until a temperature ranging between 500 and 525 F. was reached. This high temperature was then maintained for a few minutes, usually between 15 and 30 minutes, to allow time for any foam- The resulting grease was then drawn into pans and allowed to cool to room temperature without stirring and afterwards it was milled to a homogeneous plastic mass in a grease kettle or other suitable type of milling equipment. q

Experiments were conducted with various aliphatic and aromatic acids but the lower saturated aliphatic hydroxy acids, glycolic acid and lactic acid, appeared to be most satisfactory.

Grease compositions containing 2 to by weight of glycolic acid (CHzOHCOOH) or latte acid (CHsCHOHCOOH) were prepared successfully closely related compounds also may be used.

The lactic, and glycolic acids were found to TABLE Effect of low molecular weight hydroxy organic acids in soda soap grease Olelc acid ..per cent.. Hydrogenated fish'oil acids... Glycolie acid (70%) Lactic acid (85%).. Sodium hydroxide.

Mineral oil 50 S. S. U. 210 F .do sodium petroleum sulionate (mol. wt. about 400) in mineral oil .per cent.. 2.00

otn ..d 100.00

Worked penetration (180 strokes). 265...

Free alkali (as NaOH) per ce ntu 1.32

Dropping point (A. S. T. M.) 400 Structure Good It is desiable to have a small amount of excess alkali, for example, 0.6 to 1.0%, calculated as free NaOH. The dropping point is somewhat higher with increasing quantities of alkali. The sulfonate is not essential but a small amount smooths out the grease structure and tends to prevent graininess.

It will be noted that whereas the simple sodium base grease containing 20% oleic acid saponified with 4.5% sodium hydroxide had a penetration number after working of 265, the greases prepared from lactic acid were somewhatharder in consistency. With 17% of oleic acid and 3% lactic acid (85%) saponified with sodium hydroxide the dropping point was 495 F. and almost the same with hydrogenated fish oil acids substituted for oleic acid.

These data appear to indicate a small percentage, preferably either of lactic acid or glycolic acid, may be used with beneficial results in lieu of a small part of the higher fatty acid. Additional work with these acids indicated that the optimum quantity should be between about 2 and 3%, although greater or lower limits (such as 0.5 to 5%) may be employed with useful results. As suggested above it appears to be desirable though not essential to employ at least a small amount, for example 0.01 to 5% by weight, based on the finished composition, of sodium sulfonate, preferably of the type obtained from mineral oil by treatment with sulfuric acid, to give good structure and stability to the grease when a medium grade mineral oil, such as that used in the foregoing examples is employed. The average 4 It appears that a high cooking temperature of about 500 F.. for example 450 to 500 F., should be employed for preparing greases of the character referred to above. The'stability of the comand it appears that mixtures of these acids, and

atoms with sodium hydroxide.

position appears to be improved by high temperature cooking. I

The soaps of sodium base are preferably those produced by reacting the usual saturated, unsaturated or mixed fatty acids of 12 to 22 carbon The preferred sulfonate is oil soluble sodium sulfonate as described above.

Preferably the soaps of fatty acids (stearic, palmitic, myristic, etc.) are dispersed in mineral oil at, temperatures in the neighborhood of 400 F. Soaps of oleic acid or of other unsaturated fats, are preferably dispersed at a temperature of the order of 350 F. The salts of the lower acids, lactic, glycolic (and acetic, butyric, and/or acrylic acid) are particularly insoluble in mineral 2. 00 2. 00 2. 00 100. 00 100. 00 100. 00 100. 00 229 108 210 0. 8 0. 54 0. 68 0. 54 440 498 502 502 Good Good Good Grainy ate grade of lubricating oil of parafiinic, naphthene, or mixed base. Its viscosity and viscosity index should be suitable for the proposed lubricating function and it may have a viscosity from as low as 50 S. S. U. at F. to as high as 1,000 S. S. U. at 210 F. Likewise, its viscosity index may vary widely. Other conventional vegetable or animal fats and oils may replace part of the mineral oil. It is preferred, however, to use the fatty acid rather than the glyceride since the glycerine formed has too great a solubilizing effect on the soaps when the grease attains a temperature of around 200 to 250 F.

While the above examples have been limited to glycolic and lactic acid as the low molecular weight acid, it will be understood that other suitable alpha, beta, gamma, and delta hydroxy monobasic acids may be used. They are preferably saturated aliphatic acids such as glycolic, lactic, glyceric and the like, and of low molecular weight. I

It will also be understood that the greast composition of the present invention may include usual or conventional additives and modifiers, such as tackiness and stringiness agents, viscosity index modifiers, anti-oxidants, corrosionpreventive agents, extreme pressure additives and the like as will be apparent to those skilled in the art.

What is claimed is:

1. A process for increasing the melting point of a soda base lubricating grease which comprises adding to such greases 0.5% to 5% by weight,

' based on the final composition, of a low molecular adding to said grease 2 to 3% by weight of a molecular weight saturated aliphatic hydroxy acid and heating to a temperature of about 500 F.

- 3. A process for increasing the melting point oi a soda base lubricating grease which comprises adding to said grease 0.5% to 5% of glycolic acid and heating to a temperature of the range of 450 to 550 F.

i. A process for increasing the melting point of a soda base lubricating grease which comprises adding to said grease 0.5% to 5% of lactic acid and heating to a temperature of the range of s50" to 550 F.

5. A high melting lubricating grease consisting essentially of mineral oil thickened with a soda soap and 0.5% to 5% by weight, based on the finished composition, of a lower aliphatic hydroxy acid selected from the group which consists of glycolic and lactic acids and mixtures thereof.

6. A high melting lubricating grease composition consisting essentially of mineral oil thickened to grease consistency with a sodium soap and containing 0.5 to 5% by weight, based on the finished composition, of a low molecular weight saturatedaliphatic hydroxy acid, and 0.01 to 5% of a metal sulfonate having a molecular weight with the range of 300 to 500.

7. A high melting lubricating grease composition consisting essentially of mineral oil thickened to grease consistency with a sodium soap and containing 0.5 to 5% by weight, based on the finished composition, of glycolic acid.

8. A high melting lubricating grease composi- 8 tion consisting essentially of mineral oil thickened to grease consistency with a sodium soap and containing 0.5 to 5% by weight, based on the finished composition, of lactic acid.

9. A composition as in claim 5 wherein the amount of acid is 2 to 3%.

10. A high melting lubricating grease composition consisting essentially of about 70 to 80% by weight of mineral lubricating oil of about S. S. U, viscosity at 210 F., 15 to 25% sodium soap of fatty acids having 12 to 22 carbon atoms per molecule, 0.01 to 5% of an oil soluble metal sulfonate, and 0,5 to. 5% of a metal salt of a low molecular weight saturated aliphatic hydroxy acid.

ii. A composition consisting essentially of 73.5 parts by weight of mineral lubricating oil,

soap resuiting from the reaction of 17 to 18 parts of fatty acid of '12 to 22 carbon atoms with- 4.5 parts of sodium hydroxide, 2 to 3% of a sodium salt of a low molecular weight aliphatic acid selected from the group consisting of glycolic and lactic acid and mixtures thereof, and about 2 parts of a solution of sodium sulfonate of a molecular weight within the range of 300 to 500.

ARNOLD J. MORWAY. CLOYCE R. DANIELS.

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

UNITED STATES PATENTS