US2334239A - Stabilizfd grease composition - Google Patents

Description

Patented Nov. 16, 1943 orncs,

and Gus Kaufman,

New York, N. Y., asslgnors to The Texas Company, New York N. Y., a corporation, of Dela- No Drawing. ApplicationDeeember 30,1941,

Serial N0. 424,924

. v Claims. This invention relates to stabilized grease compositions and moreparticularly to anhydrous lime soap greases andmethodsof preparingthem.

compositions of this invention, fatty acids are used in the preparation of the lime. soap rather than fats or fatty oils in order to avoid the libera- Ordinarily, lime soap cup greases,- as usually manufactured, are composed of mineral lubricating oiL-lime soap prepared from fats, such as tallow or tallow oil, a portion 'of the glycerine liberated in the saponiflcation of the fat remaining unvolatilized, and a small amount of water to bring about the proper texture and tostabilize the product against separation. In the manufacture of these greases, it is diiilcult to adjust'the water content required for stabilization. The final products have poor heat stability, relatively lowmelting points of the orderjof 200 F. and bea low and break down into gelled soap lumps and free oil when heated to a temperature at, above, or even below their melting points because of loss of stabilizing water. Such greases are unsuit able for use in bearings which operate at elevated temperatures due to the fact that the greases break down in the bearings at about 150-175 F.

These ordinary'cup greases also have poor storage stability, are susceptible to oxidation, become rancid, develop red to brownish colors on the surface and cause corrosion; pitting and even seizure of the bearings packed therewith. In view of tion of glycerine which would normally be retained in the product at temperatures of manufacture. While the, soap in the grease may be prepared from the customary fatty acids such as stearic, palmitic, tallow fatty acids, etc., and a fairly good product obtained, it has been found that a superior product having a higher melting point. increased heat stability, better texture, consistency and resistance to oxidation is obtained by the use of saturated fatty acids of higher molecular weight. These fatty acids may be split from hydrogenated oils or fats, particularly marine or fish oil. Preferably, the fatty acids should contain in excess of 40% of saturated acids higher in molecular weight than stearic acid. As an example, commerically' available fatty acids known these limitations, the held of use of such cup greases has been limited primarily to cups on shafting and the like whereelevated temperatures much above 175 F; areinot encountered and where the grease is used up rather rapld1y, requiring frequent replenishment.

In our co-pending application, Serial No. 352,- I 116, filed August 10, 1940, of which this application is a continuation-in-part, there is disclosed and claimed a stabilized anhydrous lime-soapv grease which consists of a lubricating oil, lime soap and a stabilizing mixture of lanolin, and an ester of a higher fatty acid and a polyhydrio alcohol, such as glyceryl monostearate. In addi- 'tion to these components of the stabilizing mixture, there is also disclosed and claimed the use of critical amounts of high molecular weight free ,fatty acids. 7 According to the present invention, a stabilized grease composition may be obtained by incorljporating in a lime soap rease a stabilizing mixture consisting of castor oil and esters of higher fatty acids and polyhydric alcohols. V'I'his stabilizing mixture may be modified as in the eased the co-pending application bythe use of additional critical amounts of high molecular weight free fatty acids.

In the manufacture of the stabilized grease as Snodotte acids," having the following composition, have been found to be eminently suitable:

7 Per cent by weight Myristic (C14) 9 Palmltic (Cm) 22 Stearic (Cu) 27 Arachidic (Cat) 22 Behenlc (C22) 20 Typical tests on ,a'vcommercially available Snodotte acid and specifications which the acids should meet are as follows:

Example Specifications Saponlflcatlon N0 197 195-206 Neutralization N o..- 193 -196 IodineNo l l 4 Titer, '0 54.6 64-56 1 Maximum.

uct is that known as Hydrofol acids which are also saturated fatty acids split from hydrogenated fats of this character. V i

Inithe manufacture of the greases of this invention, the proportion of soap may vary within quite wide limits, depending upon the grade or consistency of the grease desired. The propor tions of soap, for example, may vary from about 6 to 30% or more, giving greases of the ordinary rangeof consistency. The amount of lime employed to form soaps by reacting with the fatty acids may be slightly less than the chemically equivalent amount so that the resulting grease contains a smallexcess of fatty acid of the order Another suitable commercially available prodmelting point. The-use of an' excess of" lime oi the order of. 0.5% and over; on the basis-.01 the finished grease, results in a granularrproduct. having. littlev grease structure Whichissubject" to oil separation and which isotherwi'sez'generally,

unsuitable. It; free fatty acid. isdesired inzthe grease composition; itmay be obtained by adding a deficiency of lime as indicatedabove;.or"the':

proportion of 0.4 to0.8% of any of the-high'molecular weight fatty acids may beadded to th composition containing neutral soap.

Proportions of: free acid of theorder of 1%.or moreshould be avoided-since such. proportions result in a .product whichzhasalower shortperiodfof time. This increase in body isof the finished grease, and in imparting an added resistance to discoloration and crust' formationi' on the surface of the grease in the presence of.

excessive atmospheric humidity. An added ad'- vantage inthe use of castor'oilis'its ability to prevent the swelling of rubber surfaces which are usually found inmany types of lubrication systems. ,Typical-testsqf' a castor oil which may be used according to thepresentinventionare the following:

Saponification No 181.2

OH value (sealed .tube method) 164 Iodine No 1 v we 8&6 Free fatty acid, per centias. oleic acid) 4-.8 Flash,. F 535 Fire, F 615 Visa/210 F., S. U ..100

The other component of the stabilizer usedin glycol. Suitable esters of. glycerines andglycols are the. partial esters containing i'ree hydroxyl groups but in the case of the polyglycols and polyglycerines, which are polyhydric alcohols containing ether linkages, .both the partially and:

completely esterified compounds may be used.

' Examples of compounds which havebeen iound to be suitable are glyceryl monostearate, triethylene glycolmonostearate and triethylene glycol distearatmthelast mentioned being an vperature gradualla'up toabout260 F. to 280 F.

The basev becomes proto effect dehydratiom. gressiveiy cleareraswater is removed and finally is in aclear-gel form upon complete dehydration.

At this stage theheat is cut oil and the glyceryl" monostearate is'added ather in thei'orm of small piecesor; in; solution in, an equal proportion of the mineral-oilemployed. The'remainder oi the mineral oil is added slowly in small'increments' while the'mass is stirred andallowed to cool; slowly. the range of'about:220F. to 190? F; .the grease tends, to become progressively more In the range of about l908 F.-to 1 50 F. the grease starts to pick opaque, adhesive and softer.

up: body 1 upon .continued' stirring and builds up to a very heavy,;stiff" body in'a comparatively accompanied. by'alevelingofi or. a rise in temperature. When-there is no further increase in body uponcontinued. stirring,. the product .is tested ior hardness' andiit necessary, the hard-- 'ness' isadjusted' by the addition of fatty acids melted: in" a s mail amount of 'oil which, promotes g'reaten's'tifi ness'zor yield. The required proportion, of" 'castor oil. is then. added to give the product a more-.adhesiveltexture. and glossy appearance. It is: preferredto prepare the above product as a'heavy grease and the lightergrades may be preparedby, thinning the heavy grease with 'additionalmineral oil. I

The "iact 'thattheflgrease in the: range of about 190 "F. to 150 Fi'build's upjto a very heavy body upon 'continu'edfstlrrin'g with an accompanying leveling" ofl or, rise-in temperature signifies that a" novel change takes place. In the ordinary grease: manufacturing processes, continued stirring results in: a thinning .offlthe grease. It is believed thattheyleveling.offIonrise of temperature; which represents an evolution of heat is perhaps theresult ofa sudden crystallizationor g'elation andiniaybe analogous to theevolution of heat during Eth'e crystallization of certaininorexample of a completely esterifiedproduct 'containing ether linkages.

' From the standpoint of effectiveness, availability and' cost, glyceryl monostearate is pre-* ferred. A commercially available .glyceryl mono stearate which we have used to advantage, is' a.

product now sold by Glyco Products Company, of New York, .New. York, as ,Glyceryl Monostearate S which has the following character-- istics: I Free fatty acid; per cent (as oleic acid) ..g 3.61

OHvalue (sealed tube method) 344 I In the manufacture of lime soap 'g-reasesac.- cording. to the present invention, the 'fatty, acids and a. portion of the mineral oil are charged-to" a kettle and heated with stirring to melt theacids. The lime ina slurry-witha small amount of water is then slowly added with .continued heating. and agitation to effect :the formationof the lime soap, the temperatures being. main-'" tained at about to 180 F. until a smooth paste or liquid is obtained. Heatingv and --agita-- tion are then continued while raising the term ganic substances.

g In view of neyi ssfpreiie'rgy from the system, the'grease'isfleft in amore stable structural state so that subsequent texture change during storage aremminimized. Nov matter what explanation is given tofthese "phenomena, theyresultin grease of a structure thatis peculiarly resistantto objectionable hardening during storage.

'It has been found that the optimum result dee scribed previously whichresult from the addi i tionof the stabilizing mixture of thepresent invention to a iliinesoap grease mayv b obtained by the addition of. the various components with-r in thefollowing'rangeof. proportions. These percen'tage-ranges are' based upon an-analysis of, the finished greasecornposition. 1

As. an sample-t1 the preparation or o "3W5v der lubricant, the following exampleis presented A mixtureof' 25" pounds of Snodotte acid s,.30.1 pounds offa' mineraldubricating oil of an S. A. E. '.40 grade, 16.9pounds of-afmineral lubricating oil of an SIAZ -E'.-'20tgrade", l6 20 grams oi lime, and 7. pounds of water; was 'charged'to a kettle and. heated" while; stirring at "about 200 F; until a" smooth paste or liquid was obtained. The heating= andiagitat'ioniwere then continued while rais- .B'ef cent weight ing the temperature gradually up to about 260 F. to 280 F. to efiect dehydration. The paste became progressively clear as water was removed and finally was in a clear gel form upon complete or substantially complete dehydration. At this stage the heating was discontinued and a solution of 6.25 pounds of glyceryl monostearate in a mineral lubricating oil was added. There: after, 184.7 pounds of a blend of mineral lubricating oils in the proportion of 63% lubricating oil of an S. A. E. 40 grade and 37% lubricating oil of an S. A. E. 20 grade were slowly added in graduated portions while the mass was being stirred and allowed to cool slowly. In the range of about 220 F. to 200 F. the grease became progressively more opaque, adhesive, and softer. In the range of about 200 F. to 170 F. the grease started to pick up body upon continued stirring and built up to a stiff body in a short time. At approximately 170 F; a control penetration was run according to the usual A. S. T. M. method. The reaction mass was then adjusted by the addition of small increments of mineral oil blend to obtain a penetration of approximately 225 at 77 F. 1494 grams of castor oil were then added to depress the yield and give the product a more adhesive texture and a glossy appearance. The product was then drawn at about 140 F. as the finished grease composition which contained 13.0% soap, 1.3% glyceryl' monostearate, 1.9% castor oil, and 83.5% mineral oil. v I

The term anhydrous" as used herein is intended to include compositions which may contain traces up to 0.15% of water as determined by the ordinary methods of analysis.

Obviously many modificationsand variations of the invention, as hereinbefore set forth, may

be made without departing from the spirit and amount of lime soap of high molecular weight fatty acids sufficient to impart to saidmineral oil the consistency of a grease, and a minor proportion of a stabilizing mixture consisting of castor oil and an ester of a higher fatty acid and a polyhydric alcohol, said ester being of the group consisting of partial esters and esters containing ether linkages.

2. A stabilized grease composition according to claim 1 in which the ester is glyceryl monostearate.

3. A stabilized grease composition according to claim 1 in which the fatty acid constituent of the lime soap is a mixture of saturated'fatty acids from a hydrogenated fatty oil.

4. A stabilized grease composition comprising a homogeneous mixture of a mineral oil, an amount of lime soap of high molecular weight fatty acids sufficient to impart to said mineral oil the consistency of a grease, and a minor proportion of a'stabilizing mixture consisting of free higher fatty acid, castor oil, and an ester of a. higher fatty acid and a polyhydric alcohol, said ester' being of the group consisting of partial esters and esters containing ether linkages.

5. A stabilized grease composition according to claim 4 in which the ester is glyceryl monostearate.

6. A stabilized grease composition according to claim 4 in which the fatty acid constituent of the lime soap is a mixture of saturated fatty acids from a hydrogenated fatty oil.

7. A stabilized grease composition comprising a homogeneous mixture of a mineral oil, 6-30% lime soap, about 13% castor oil, and about 0.51.9% esters of a higher fatty acid and a poly-.

hydric alcohol, said esters being of the group consisting of partial esters and esters containing ether linkages.

8. A stabilized grease composition comprising a homogeneous mixture of a mineral 011, an amount of lime soap sufficient to impart to said mineral oil the consistency of a grease, about 0.4-0.8% free higher fatty acid, about l-3% castor oil, and about 0.5-1.9% esters of a higher fatty acid and a polyhydric alcohol, said esters being of the group consisting of partial esters and esters containing ether linkages.

9. A stabilized grease composition according to claim 8 in which the ester is glyceryl monostearate.

10. A stabilized grease composition comprising a homogeneous mixture of a mineral oil, about 6-30% lime soap, about 0.4-0.8% free higher fatty acid, about 1-3% castor oil, and about 0.5-1.9% esters of a higher fatty acid and a polyhydric a1- cohol, said esters being of the group consisting of partial esters and esters containing ether linkages.

11. A method of preparing a stabilized grease composition which comprises heating a mixture of mineral oil. high molecular weight fatty acids, and a proportion of lime to yield an excess of fatty acid of from 0.40.8%, the amounts of high molecular weight fatty acids and lime used being sufficient to impart to said mineral oil the consistency of a grease, heating at a higher temperature to drive off any water and to form an anhydrous soap base with the mineral oil present, adding an ester of a higher fatty acid and a polyhydric alcohol, adding more mineral oil, cooling and agitating the mixture until the mixture no longer stiffens under continued agitation, adding a small amount of castor oil, and drawing the lubricant at a temperature below 200 F.

12. The. method of claim 11 in which the ester is glyceryl monostearate.

13. A stabilized grease composition comprising a homogeneous mixture of a mineral oil, about 6-30% lime soap, and a minor proportion of a stabilizing mixture consisting of castor oil and an ester of a higher fatty acid and a polyhydric alcohol, said ester being of the group consisting of partial esters and esters containing ether linkages.

14. A stabilized grease composition comprising a homogeneous mixture of a mineral oil, about 6-'30% lime soap, and a minor proportion of a stabilizing mixture consisting of free higherfatty acid, castor oil, and a polyhydric alcohol, said ester being of the group consisting of partial esters and esters containing ether linkages.

15. A stabilized grease composition comprising a homogeneous mixture of a mineral oil, an amount of lime soap of high molecular weight 4 fatty acids sufllcient to impart to said mineral oil the consistency of grease, and a minor proportion of a stabilizing mixture consisting of 0.4-

0.8% free higher fatty acid, castor oil, and anester of a higher fatty acid and a polyhvdric a1- cohol, said ester being of the group consisting of partial esters and esters containing ether link- ROBERT S. BARNEIT. GUS KAUFMAN.