US2850454A

US2850454A - Production of greases by alkali fusion of materials containing hydroxy fatty acid and glycerine radicals

Info

Publication number: US2850454A
Application number: US323511A
Authority: US
Inventors: Arnold J Morway
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1952-12-01
Filing date: 1952-12-01
Publication date: 1958-09-02
Anticipated expiration: 1975-09-02

Description

2,850,454 PRODUCTION OF GREASES BY ALKALI FUSION OF MATERIALS QG-NTAKNTNG HYDROXY FATTY AllD AND GLYCERINE RADICALS Arnold J. Moi-way, Railway, N. 5., assignor to Essa Research and Engineering Company, a corporation of Delaware No Drawing. Application December '1, 1952 Serial No. 323,511 7 Claims. (Cl. 2S2-=33.2)

The present invention relates to new and improved lubricating greases and to a new process of preparing the same. More particularly, the invention pertains to a method of manufacturing new and improved lubricating greases of high dropping point and soft consistency over a wide temperature range and to greases produced by this method.

In its broadest aspect, the invention provides for the production of greases in which the thickening agent is obtained by heating a material containing the radicals of a high molecular weight hydroxy fatty acid and glycerine at high temperature in the presence of alkali. High temperature greases of excellent quality may be produced in this manner.

Prior to the present invention, soap-thickened greases of desirable hardness characteristics and high melting or dropping point, i. e., greases melting above about 400 F. and having a smooth soft consistency over a Wide temperature range, i. e., between about 200 and 400 F., have been known. These greases have been prepared by the saponification of rapeseed oil with an excess of alkali while heating to a temperature of about 480500 F. in a lubricating oil vehicle containing a small amount of sodium sulfonate as described in U. S. Patent No. 2,265,791.

The desirable combination of excellent qualities of these greases was believed to be due largely to the use of the glycerides of C long chain acids, such as erucic acid, as the source of the soap. Rapeseed oil, mustard seed oil and the rest of the Brassidic family are the only known commercial sources for these materials. Erucic acid is present in fish oil but cannot be readily separated therefrom. Actually, soap-thickened greases having similar properties have not been prepared commercially heretofore from other glyceride-type fats or oils nor from the corresponding fatty acids as such, nor from synthetic composites approximating rapeseed oil.

More specifically, prior to the present invenion no commercial process was known by which unsaturated oils other than rapeseed oil could be converted into desirable high temperature greases. While grease products having high melting points have been obtained from these raw materials, the products are extremely hard and dry and unsuitable for ball or roller bearings requiring soft unctuous greases. This situation is unsatisfactory particularly whenever there exists a shortage of rapeseed oil as it has actually occurred during war time. Efforts to produce a good quality high temperature grease from such rapeseed oil substitutes as mixtures of 50% oleic acid and 50% erucic or behenic acid with 2% glycerine were likewise unsuccessful when the known process for producing such greases from rapeseed oil was employed. The present invention eliminates these difiiculties.

It is, therefore, an important object of the present invention to provide soap-thickened, good quality high temperature greases based on raw materials other than rapeseed oil. Other objects and advantages will appear from the following description of the invention.

it has now been found that glyceride-type fats and United States Patent l atented Sept. 2, 195a composition of such fats and oils may be used in place of rapeseed oil for the production of high temperature greases of excellent quality provided a large excess of alkali over the amount required for saponification of the glycerides or neutralization of the fatty acid is em ployed, and saponification or neutralization proper is followed by heating of the reaction mixture to such temperatures substantially exceeding 510 F. as are conducive to alkali fusion of the glycerine with accompanying evolution of hydrogen. Castor oil, which is the glyceride of ricinoleic acid, is the preferred glyceride of the invention. However, hydrogenated castor oil, i. e. castor wax, or m xtures of esters of hydroxy-stearic acids or other hydroxy fatty acids with glycerine may also be used.

While the reaction mechanism is not fully understood, it may be postulated that, in the second high teminvolved:

(Fat) Sapzmincation CH2OOCR.OHOOCR.CH2OOCR 3NaOH Glycerlne Soap CI'IQOH OHOH. CHZOH 3RCOOZx'a CH2OH.CHOH.CH2OH Dehydration Cannizzarro (5) Fusion CHZ=OHGHZOH NaOH CH OH-COONh. 2H: Reaction (1) illustrates the conventional saponification reaction of the first, low-temperature stage of the invention. The second, i. e., the high temperature, stage may involve reactions (2)(5).

The sodium acrylate produced forms a complex soap with the soap formed in accordance with Equation 1, such as sodium ricinoleate, to impart a high dropping point to the grease. A part of the acids of the castor oil or castor wax originally used or the sodium soaps thereof may form under fusion with sodium hydroxide at elevated temperatures sodium sebacate and octenol-2, as shown below.

(6) CH (CH CHOHCH CH= CH(CH C0 OH-i- CH CH CHOHCH CH= CH (CH COONa+ NaOH NaOOC(CH COONa+C H OH+H 5l0-570 F. until foaming caused by gas evolution oils containing the radicals of high molecular weight hydroxy fatty acids and mixtures approm'mating the ceases. It is particularly to be noted that this second reaction does not initiate below this range when employing the starting materials of the present invention.

Within this range, the temperatures required in the second stage are higher for saturated or hydrogenated fats and fatty acids than for unsaturated saponifiable materials. In the case of the former, alkali fusion accompanied by gas-evolution and roamin may begin at about 550. F. and stop'at about570 F., as compared to about 530 and. 550 F. for the corresponding temperatures in the case of unsaturated saponifiable mate: rials. On the other hand, whenrapeseed oil is used in accordance with the known procedure, saponific'ation' is completed at about 3'O03'50 F. and gas evolution and foaming begin at about 450 F. and terminate at about Soap-forming basematerials useful for the purposes of the present invention are quite generally saturated or unsaturated or hydrogenated naturally occurring glyceride-type fats and oils of animal or vegetable nature containing hydroxy groups in their" fatty acid radical, such as castor oil,. castor wax, etc., which begin to react with alkali to produce, hydrogen at temperatures above about 510 F., as well as mixtures. of saturated and/or unsaturated high molecular weight hydroxy' fatty acids with glycerine. .Mixtures of hydroxy fatty acids and glycerine with non-hydroxy fatty acids or glycerides of hydroxy or non-hydroxy fatty acids can, of course, be used. The preferred unsaturated acids are thosecontaining: at least 18 and up to about 20 carbon atoms, particularly ricinoleic and hydroxy stearic acids. When mixtures of hydroxy fatty acids and glycerine are used, the proportion of glycerine is preferably that corresponding to or approximating the glyceride of the hydroxy fatty acid involved and should notexceed about twice that amount. In the latter case, correspondingly larger amounts of alkali should be used. The raw materials of the invention may be combined with rapeseed oil or other suitable fats, oils and fatty acids in a wide range of proportions.

As in the case of greases based on rapeseed oil alone, the addition of small amounts, say, about A to about 2% based on the finished grease, of anoil soluble sulfonic compound derived from petroleum should be added to increase the soft and unctuous quality of the grease and its temperature stability. This material also acts as a rust preventative. A petroleum sulfonic acid or an alkali metal soap thereof may be used for this purpose. Other conventional greaseadditive's, such as anti-oxidants, especially amino compounds, dispersants, extreme pressure agents containing sulfur, etc., may be added.

Regarding suitable lubricating oil bases, mineral oils o'runsapo'nifiable' synthetic oils should be used until alkali fusion is completed. For example, a mineral oil maybe employed in this stage of the process. After fusion and after recrystallization of the soap at a temperature below 300 F., any desired type'of lubricating oil including ester-type synthetic oils may be added. A

Greases, in accordance with the invention, quite generally, may be prepared as follows. The glyceride or a mixture of high molecular weight hydroxy fatty acids with glycerine is charged together with about 50% of the total lubricating oil requirement to a heated grease kettle and warmed to about 130-150 F. Alkali metal hydroxide, preferably sodium hydroxide is added in an amount at least twice, but preferably greater than twice, as much as that required to saponify the fat or acid. An excess of IUD-125% over saponification requirements should be used, preferably in the form of a 40-50% aqueous solution of NaOH. The temperature is then raised to about 300-350 F. and the balance of the lubricating oil is added. Heating iscontinued to melt the mass completely andbeyond this point until foaming begins, becoming appreciable at temperatures of about 510-550 F. Foaming is usually violent enough to require top stirring which prevents overflowing. The temperature is further raised until foaming commences to recede, which takes place after a temperature rise of about20 F. This temperature which usually falls between about 530 and 570 F. is maintained for about 20-40 minutes until foaming has ceased.

The grease may then be allowed to cool to about 300- 330 F. whereupon at least a portion of the remaining. excess alkali may be neutralized by the addition of fat or fatty acid. The grease should have a free alkalinity of less than 1.0%. Thereafter, further quantities of lubrieating oil may be added to adjust the grease consistency to the desired degree. Concentrations of 15-30 wt. percent, based on the finished grease, of total soap-type thickener are suitable for the purposes of the invention.

Regarding the cooling stage, it is noted that cooling times of about 822 hours have been used heretofore when working with rapeseed oil. Similar cooling times may be employed in the present process. found, however, that the cooling time may be shortened to as little as 6-10 hours for the temperature interval from about 570 F. to about 200 F. when sufiicient' acid is added during the cooling process completely to neutralize any excess free alkalinity remaining after fusion and to have even a slight excess of acid in the finished grease, as itis disclosedand claimed more broadly in the copending Morway" application Serial No. 289,898,

filed May 24, 1952, now abandoned, and assigned to the same interests. In addition to substantialsavings in processing equipment due to. the shortened cooling times, the greases so prepared have satisfactory lubrication life without any loss inhigh temperature quality.

Greases obtained in accordance with the present inventionhave dropping points substantially in excess of 400 F. They have a soft, unctuous consistency attemperatures above 2 0 F. and retain the same over. a wide temperature range.

The invention will be further illustrated by the following specific examples which represent preferred modifications ofthe invention.

EXAMPLE I Formulation Ingredients: Wt. percent Castor oil 22.00 Sodium hydroxide 5.00

Sodium sulfonate blend (50% mineral oil and 50% Na sulfonate)' a a Phenyl alpha-naphthylamine (oxidation inhibitor) r 1.00 Condensation product of propylene diamine and salicylaldehyde (oxidation inhibitor) 0.50 I

Naphthenic-type mineral oil having a viscosity of 50 S. S. U. at 210 F 70.50

to 300 F. The oxidation inhibitors were added and the grease cooled to 200 F. At this temperature the grease was filtered, homogenized and packaged. 1 Analysis of the fatty acid extracted from the soap thickener in this grease shows that the fatty acid has undergone changes and differs from the original castor oil as follows:

Mixed fatty Fatty acids acids from extracted castor oil from grease It has been EXAMPLE II Formulation Ingredients: Wt. percent Rapeseed oil 11.00 Castor oil 11.00 NaOH 5.00 Sodium sulfonate blend (50% mineral oil,

50% Na sulfonate) 1.00 Phenyl alpha-naphthylamine 1.00 Condensation product of propylene diamine and salicylaldehyde 0.50

Naphthenic-type mineral oil having a viscosity of 50 S. S. U. at 210 F 70.50

The grease was prepared similarly as described in Example I.

1 Hydrofol acids are hydrogenated fish 011 acids correspond ing in saturation to commercial stearlc acid.

The grease was prepared as described in Example I. The dropping point of this grease during manufacture was as follows:

Sample taken at 513 F.--398 F. Sample taken at 530 F.424 F.

The properties of the greases of Examples I, II and III are tabulated below in comparison with those of a grease prepared from rapeseed oil in the conventional manner.

PROPERTIES OF GASTOR OIL GREASES COMPARED WII'JIH GREASE THICKENED WITH SOAP OF RAPESEED OI Rapeseed Example Example Example 011 grease I II III Composition, weight percent:

Rapeseed oil 22.00 11.00 Castor oil 11. 22. 00 Castor wax 14. 67 Hydrogenated fish oil glyeeride 7. 33 NaOH 4. 75 5. 00 5. 0D 5. 00 Sodium sulfonate blend (50% mineral oil, 50% Na sulfonate) 1. 00 1. 00 1. 00 1. 00 Phenyl alpha-naphthylamine 1. 00 1. 00 1. 00 1. 00 Condensation product of propylene diamine and salicy1aldehyde 0. 50 0. 50 0. 50 0. 50 Mineral oils 70. 75 70. 75 70. 75 70. 75 Properties:

Percent free alkalinity (N'aOH) 0. 30 0.30 0.20 0.30 Dropping point, F 500+ 500+ 500+ 500+ Penetrations, F.

Unworked 252 240 309 276 Worked, 60 strokes 265 268 335 308 Worked penetration after homogenization to ultimate hardness 177 203 329 232 Norma-Hoffman oxide tion, hours to 5 p. S. i. drop in 0; pressure..." 110 150 100 212 Maximum temperature of manufacture, F 500 530 530 5.50

It has further been found that the grease of the present invention will prevent friction oxidation. In the lubrication of heavy truck front wheel bearings, the inner and outer bearings of the wheel assembly are slipped over the wheel spindle. In actual practice the inner bore surfaces tend to turn only a small portion of a complete revolution while being subjected to heavy intermittent shock loads. the occurrence of fretting corrosion. After short periods of operation with common soap-thickened lubricants, corrosion between the inner race bore surfaces and the spindle occurs. Further operation results in the spread of iron oxide into the bearing itself resulting in early bearing failure. A further complication is the welding of the bearing to the spindle, if this fretting corrosion is not observed early. When this occurs, the spindle must be removed and replaced. This is very expensive.

Lubrication of wheel bearings with the lubricant of the present invention materially reduces this oxidation corrosion and gives excellent lubrication for long periods of operation. Truck wheel assemblies employing a grease prepared as described in Example 11 have gone to brake band replacement, i. e. to approximately 75,000-

-90,000 miles, and even then thelubricant was in good condition. This effect is substantially superior to that of greases prepared with rapeseed oil in the conventional manner, which permit early occurrence of mild fretting corrosion.

The present invention is not limited to any theory of the process of grease manufacture nor to the specific examples set forth above. The relative proportions of the grease constituents may be varied within the limits indicated to obtain greases of different consistency and varying characteristics.

In the following claims, the terms saponifying, saponifiable and saponification refer to the formation of soaps by an alkali treatment of fats, oils and/or fatty acid.

What is claimed is:

1. A process of preparing lubricating greases containing a major proportion of lubricating oil, which comprises charging to a reaction vessel a mixture consisting essentially of about 5 0% of said proportion of a mineral lubricating oil and a minor grease making proportion of a soap-forming material containing the radicals of a high molecular weight hydroxy fatty acid having in the range of 18 to 20 carbon atoms per molecule and of glycerine in an amount corresponding to the glyceride of said acid, heating the mixtureto a temperature in the range of 130 to 150 F., adding to said heated mixture sodium hydroxide in an amount in the range of to in excess of that required to saponify said soap-forming material, thereafter raising the temperature of the mixture to in the range of 300 to 350 F., adding the balance of said lubricating oil to the mixture so heated,

continuing heating to melt the mass and beyond this point to a temperature in the range of 510 to 550 F. suffi cient to liberate gas and cause foaming, further raising the temperature to a level in the range of 530 to 570 F. until foaming subsides, cooling the mixture to a temperature in the range of 300 to 330 F. and adjusting the free alkalinity of the mixture to less than one percent.

2. The process of claim 1 wherein said soap-forming material is castor oil.

3. The process of claim 1 wherein said soap forming material is hydrogenated castor oil.

4. A process for preparing lubricating greases suitable for high temperature service which consists essentially of the steps of mixing a portion of the mineral lubricating oil required in the finished grease and a saponifiable material selected from the group consisting of hydroxy fatty acid glycerides and mixtures of a hydroxy fatty acid with glycerine in glyceride proportions, with an alkali metal hydroxide, the amount of said metal hydroxide being sufiicient to neutralize said saponifiable material and acidic products formed by decomposition of the glycerine under conditions hereinafter stated, heating the resulting mixture to a temperature sutficient to saponify said sa- This is a condition highly conducive to' ponifiable material, but belowthe, decomposition tempera.

5. The process of claim 4 wherein the saponification' is carried out in thepresence of. about 0.25 to 2.0 percent, based on the finished grease, ofan oil soluble sulfonic compound derived from petroleum.

6. The processof'claim 4 wherein said hydroxy fatty acid is ricinoleic acid.

7. The process ofclaim .4wherein said hydroxy fatty acid is a hydroxy stearic acid.

References Cited in the file of this patent UNITED STATESHPATENTS 2,265,791 Zimmer et a1 Dec. 9,1941

8 McLennan; ,142.2--- Mar. 18, 1947 Bondi July 27, 1948 Ashburn et a1. Sept. 28, 1948 Beebower et a1 Dec, 7, 1948 Moi-way et a1. L Apr. 26, 1949 Morway Apr; 26, 1949 Bondi Iu1y12, 1949 Swenson Nov. 8,1949 Butcosk Jan. 24, 1950 'Rudel et a1. Apr. 11, 1950 Ashburn et a1. May 23, 1950 Bondi. Mar. 13, 1951 Morway et a1. Apr. 1, 1952 Bailey May 27, 1952 FOREIGN PATENTS Great Britain. June 21, 1951 OTHER REFERENCES Chemistry of Organic Compounds, No11er,- W, B. Saunders Co.-, Philadelphia, 1952, page 692.

Claims

1. A PROCESS OF PREPARING LUBRICATING GREASES CONTAINING A MAJOR PROPORTION OF LUBRICATING OIL, WHICH COMPRISES CHARGING TO A REACTION VESSEL A MIXTURE CONSISTING ESSENTIALLY OF ABOUT 50% OF SAID PROPORTION OF A MINERAL LUBRICATING OIL AND A MINOR GREASE MAKING PROPORTION OF A SOAP-FORMING MATERIAL CONTAINING THE RADICALS OF A HIGH MOLECULAR WEIGHT HYDROXY FATTY ACID HAVING IN THE RANGE OF 18 TO 20 CARBON ATOM PER MOLECULE AND OF GLYCERINE IN AN AMOUNT CORRESPONDING TO THE GLYCERIDE OF SAID ACID, HEATING THE MIXTURE TO A TEMPERATURE IN THE RANGE OF 130* TO 150*F., ADDING TO SAID HEATED MIXTURE SODIUM HYDROXIDE IN AN AMOUNT IN THE RANGE OF 100 TO 125% IN EXCESS OF THAT REQUIRED TO SAPONIFY SAID SOAP-FORMING MATERIAL, THEREAFTER RAISING THE TEMPERATURE OF THE MIXTURE TO IN THE RANGE OF 300* TO 350*F., ADDING THE BALANCE OF SAID LUBRICATING OIL TO THE MIXTURE SO HEATED, CONTINUING HEATING TO MELT THE MASS AND BEYOND THIS POINT TO A TEMPERATURE IN THE RANGE OF 510* TO 550*F. SUFFICIENT TO LIBERATE GAS AND CAUSE FOAMING, FURTHER RAISING THE TEMPERATURE TO A LEVEL IN THE RANGE OG 530* TO 570* F. UNTIL FOAMING SUBSIDES, COOLING THE MIXTURE TO A TEMPERATURE IN THE RANGE OF 300* TO 330*F. AND ADJUSTING THE FREE ALKALINITY OF THE MIXTURE TO LESS THAN ONE-PERCENT.