US2514330A - Mixed base lubricating greases - Google Patents

Description

, Patented July 4, 1950 MIXED BASE. LUBRICATIN G GREASES Arnold J. Morway, Clark Township, Union County, and Rosemary OHalloran, Elizabeth, N. J., assignors'to Standard Oil Development- Company, a corporation of Delaware No Drawing. Application June 5, 1948, Serial No. 31,398

4 Claims. (Cl. 252- 10) The" resent invention sass to' mixed" base lubricating "greases "and particularly to sodabarium soap greases which areparticularly suited for the lubrication of high speed anti-friction bearings over a broad temperature range. The invention relatesfurther toa process for producing-greases of'thetype referred to and to the improvement of viscosity-temperature characteristics of such greases;

In U. S. 'Patent'NO. 2,245,702 to Morway, one

of the present inventors; there is described a mixed base grease prepared fromthe mixed soaps of soda and baryta which has been found fairly satisfactory'for the lubrication of anti-friction bearings. The compositiondescribed in said patent, however, has certain deficiencies in that it is not usefulv over ,as wide a temperature range as may be desire'd and its viscosity and consistency vary considerably with wide changes in temperature. The greasedescribed in said patent contains'a slight'excess of alkali, for example from 0.05 to 0.3%. The composition described therein I becomesrfibrous at temperatures of about 230 to 240 F. v

It has now been found that unexpected improvements in mixed soda-barium grease may be obtained by employing fatty acids of average lower molecular weight than the acids used in the prior art and by employment of a base lubricating oil of high viscosity index. In addition, it

has been found that if the finished grease contains a small amount of free acid rather than free alkali as in the aforesaid patent, a. change in physical structure of the grease is permitted at high temperatures which makes the lubricant suitable for anti-friction bearings running at high speeds and at elevated temperatures.

It is-well known that most lubricating greases pass through a change of phase at a temperature in the approximate vicinity of the melting point of the fat or fatty acid from which the thickening soap is prepared. The phase'change occurring at this point, i. e. the uni-dimensional melting point of the soap, is slight. However, at higher temperaturesv another phase change occurs which is due toincreased thermal energy in the soap lattice and is called the bi-dimensional melting point. phenomenon by which" a soap structure which exists in threedimensions breaksdowzr in the By the latter expression is meant the second of such dimensions. At suchca phase:

change or transition point, lubricating greases lose their short fibered smooth structure andbecome very fibrous and rubbery in character.

If the change in phase referred to above occurs in a lubricating grease below the desired operating temperature, the grease is not a good lubricant. Since anti-friction bearings under many" operating conditions attain temperatures considerably higher than the normal transition or phase change temperature of greases, it is desirable to change the transition temperature. The present invention is basedupon the discovery that this can be accomplished by using a fatty acid of shorter chain length, or lower molecular weight, in producing the grease-forming soap. Apparently such a reduction in the molecular weight or chain length also decreases the solvency of the soap in the mineral oil. In addition, by the use of more aliphatic type mineral oils, i. e.

' paraifinic or predominantly paralfinic as distinguished from naphthenic or aromatic, the soap solvency in the oil is further decreased. This further raises the temperature at which phase change or transition takes place. These results.

can be obtained without so far reducing solvency of the mineral oil for the soaps that the soaps will separate from the oil on cooling.

The use of a high viscosity index oil, that is an oil that is more paraifinic than customarily used in grease manufacture, not only raises the transition temperature but also gives a product which has better temperature-viscosity relationship. The latter is an obvious advantage of the use of oil of high viscosity index but the former is quite unexpected and is contrary to the general custom of using low viscosity indexoils for most lubricating greases. As a result, lubricants,

prepared according to the present invention may be used at extremely low temperatures as Well as at very high temperatures, comparatively speaking.

By employing the three factors mentioned.-

above, namely, the shorter average length of the fatty acid chain, a base lubricating oil of high viscosity index, and a slight excess of acidity as be obtainedwith relatively less soap. Thus the soap content may be as low as 3. or 4% although Tit ma'ygalso'go as high as 25 "or. 30%rby'weight;

based on the finished grease, if a very stiif lubricant is desired. These greases obviously have more body at higher temperatures and less at lower temperatures because of the high viscosity index oil used and they give outstanding performance on the high temperature-high speed spindle test. Such greases have excellent shear stability and'do not break down upon severe mechanical working.

EXAll/[PLE As one example of a grease made according to the present invention, the following formula was employed:

12.50% hydrogenated fish oil fatty acids (predominately palmitic acid) 1.70% sodium hydroxide 0.78% barium hydroxide octahydrate 0.40% phenyl-alpha naphthylamine antioxidant 71.87% extracted Panhandle distillate (150 vis./

100, SUS) I 12.80% extractedCoastal distillate (80 via/100,

SUS)

concentrate was heated further as the remainder of the lubricating oil was added slowly. This was continued until the soap was completely dispersed in the mineral oil at a temperature of between 375 and 425 F. The grease was then poured into pans for cooling and homogenized to the desired consistency at room temperatures.

Although the foregoing is a desirable method for preparing greases of the mixed soda-barium type, they can easily be prepared by other well known methods. The temperatures employed may be as low as 350 or as high as 500 F. or more if desired. Hydrogenated fish oil acids which have an average composition of less than 18 carbon atoms per molecule and more than 14 are very satisfactory but other acids may be used if desired. In general, the fatty acids having 14 to 18 carbon atoms and even slightly higher acids in minor proportions are quite suitable, but it is important that the average should be at least slightly less than the composition of stearic acid, 1. e. 18 carbon atoms. Otherwise, oil solubility of the soaps is too great to realize the full benefits of this invention. Similarly, if the average composition is C14 or lower, the oil insolubility is too great. Simple acids such as lauric, myristic, or palmitic may be used in mixtures with each other or with stearic acid as desired to obtain the proper average.

The grease in the example, as noted above, was prepared from a base oil composed predominantly of extracted Panhandle distillate with a small amount of extracted Coastal distillate. The viscosity index of the combined oils was about 93.

For comparative purposes, two similar compositions were prepared from other oils and subjected to high speed spindle tests at a temperature of 250 F. The first was prepared from a straight Coastal distillate having a viscosity index of 50 and the second from a Rodessa distillate having a viscosity index of 113.- The performance data are shown in Table 1.

TABLE 1 Performance of Soda-Barl- The spindle test apparatus used in these runs is the ABEC-NLGI Committee Test as described in the Committees Technical Bulletin No. 5. It consists of a 204 type ball bearing mounted on a belt-driven spindle under a thrust load of 14-15 D. s. i. This is operated at 250 F. and 10,000 R. P. M. on a 22-hour cycle, (2 hours at room temperature) until failure occurs. Failure 00- curs when the bearing is running under such friction that the operating temperature rises 25 F.,

TABLE 2 Performance of Soda-BariumGi-eases at 250 F.

Mineral Oil Panhandle Rodessa Dis- Distillate tillate Via/210 F., SUS .u 44 44 Viscosity Index 113 Hrs. Spindle Life at 10,000. RPM 1, 874 500-1, 100

In general, the low temperature properties of a grease are governed by its soap content, and the pour point and viscosity (at the test temperature) of its mineral oil. Therefore, improve ments in performance may be obtained by lowering any of these factors. Dewaxing, or dilution of the mineral oil, or lowering the soap content are all possibilities.

Dewaxing the Panhandle distillate from its original +30 F. pour point to 0 F, pour point definitely improves its low temperature characteristics at -40 F., 17.4 sec./rev., as compared to 37.1 sec/rev. However, this grease did not have as good high temperature characteristics as the undewaxed stock as shown in Table 3.

es ae. ce ta niae .l. see .t ah

appease .iqua tie rofsthis aphan ees gcls .arap *such a nat e .:tha --.:,th.e ch se. :wi x ctediGoast l1d prove -.th ig ow t mpera urew mperti sm atu e. p rfo m mthi way ae easeqfjan ll n co i ation:;f&p opeti anzbe =p --du zed-. 15

I The comparative propelities of a straight Panale rd ti lat and, 9 Panha dle ldi lla eS Wi-th.l %.Q ;C a le L, arezshow an f am 1 It w ll-b not tena tisuzlarly that the .;1.ow m e tur torqu l b ntiel law-er .a n i "mixe oi lub c the. st a h P h n rd l t ser as sced-bdridmergdses Panhandle Panhandle Distillate Distillate .-l- Coastal Distillate messiah-hydrogen eee s a ii h high wi ld a ue f, t

rodu d "w th; b ly bo r 14%... .59 l 5. 1 abla a a dagils ie ver- .age charn lengths are used to form .the -soaps.

easerwith u materia lyafiect z ez h m-- uc :a c mpes tion wa a d ti at .a inth E ed x qd rba z am. .g' es .iof t ,1 ven ie ipr ductsiof aqprqximately the same .-consistency' Yes This of advantage because ]-,a large soap .con-

tent adversely afiects the low temperature performanceofithe'grease-a indicated by atorque off37.1 for a grease "containing 15.6% soap as compared with torqueof" 23:9=for the same type The ue-eer e "minimum soap content ,is advantageous for reasons of economy as w'ell as for improved lowtemperature performance. By

she iattyacid a e .used-morerso p i e ui to give the grease a stable structure. Also, such soaps increase the torque resistance of the grease at low temperature, as shown in Table 4.

Hydrogenated fish oil acids of different types vary in composition as regards the chain length of their constituents. Thus one commercial fatty acid marketed as 51-HO contained 15.8%.

myristic (C14) acid, 56.6% palmitic (C15) acid,

20.4% stearic (C18) acid, 3.4% arachidic (C20) acidand 1.3% behenic (C22) acid. Another, sold under the trade name Hydrofol 51 contained 8.5% myristic, 35.2% palmitic, 28.2% stearic and i 15.0% and 8.8%, respectively, of arachidic and behenic acids. The former was used in the ex- .famplermbove, :w'hereas the 5 as, greater torque, when used in thes rl ttermasxusedinsth greases iofifables. l p Q .i

greases prepared with soaps of higher .fatty s, re. acidsbf longer average c'n ai .01 lout the .difference in oils employed is also-pi gspme impbr'mnee, as indicated below in Table..5.

It should be noted that -grea'sescontainin'g as are-too soft f for use at elevated temperatures bec us s P9 1 hea "st i ib Thesis? {of .655 ontaine abp 1 o u aps Extracted RoQessa. Distillate i were YOoastal i t l a mesa-an g "It smite kite-d thaeth "-respective-minera1 one er "Table- 5 "had approximately the same viscosity letrg o sag t*trie aqdess distillate had a rnuch "higheryiscositytindex. p h

A th u h .th gere se .01 t i in c prepa e wit emal un sq ex ss fre e flinity as; well as free facidity, itghas been found tha t e pr enc o ag al iamc n gireefatt acid substantiall limproves thehigh tempera- ;ture iperforman of the product, [without detrifment to "the Qoxidation resistance or'shear 1 stabil ity. Evidently t, ireeifatty acidihas. somejsQ1- iri cy-.efie tm v etm th si ase rom e n rubbery at the high test temperature. The 'data 0 in Tablefishow thesuperiorlife of various greases il ydrnfol 5. :a ds, beingacida dalkaline;

spe i ly.

' meme Hig h etemperatune :performafic of ws odabarium v:- :grea'ses From thezforegQing-it 'vwill .bei'seensthat mixed base greases having excellent properties of shear stability, resistance to oxidation, yield values, and high temperature structure stability may be produced from the sodium-barium soaps of relatively low molecular weight fatty acids. As suggested above, the extracted Panhandle distillates are particularly desirable as base lubricating oils, but the invention is not limited to the use of such oils. In some cases, it is desirable to add some Coastal stock to cut back the extracted Panhandle becauseof the high pour point of the Panhandle. A mixture or blend having approximately the following characteristics appears to be highly suita- 'ble "as a base'forth'e greases of this invention, but

the invention is not by any meanslimited thereto.

via 1009'n.,,sus', 143.1 Via/210 n, s s' -1 42.5 Vis. index H 92 Flash- F 385 Pour ..Q Y V Y F +25 In general a lubricating grease prepared from oils of-;fair1y high-viscosityindex, for-example 80 to 125,-thickened with-5 or 6 to 25 .or. 30%, prefer- The limitations stated therein are asodiumbarium soap weight ratio of from 1 to 1, to about 10 to 1 which corresponds to mol ratios of from about 1.2 to 1 to about 12 to 1. The limits'in the case of the present type of compositions are greater, especially with regard to the upper limit, a

theoverall range being between about 1 to 1 and 30 to 1, on a sodium soap/barium soap. mol ratio basis. Preferably the mol ratio is in the range from about 15 to-1 to,about to 1. The preferred range in thepresent compositions is therefore considerably higher than the upper limit of the prior art compositions, which differ however infse'veralother ways. Especially suitable is a mol ratio from about 1'2 to 1 to. about 19 to 1.

. The excess quantity of acid maybe varied i somewhat but should be keptrather ,low. In general it should be fromas low as 0.01% and in general from 0.05 to 0.5% by weight calculated as free oleic acid.

I It will be understoodthatthe greases prepared according 'to this invention may contain conventional additives such as antioxidants, tackiness agents, extreme pressure additives, corrosion inhibitors, and other materials such as are well known in the art. It is generally preferred toinclude a small amount of a suitable antioxidant such as phenyl alpha napthylamine or phenyl beta naphthylamine and the like, although such material are not always required. When included they should be added in proportions of 0.1 to about 1% by weight,'based' onthe composition, 04 or 0.5% usuallybeing preferred. In general, the oil composition, which may include these additives and is referred to generally as lubricating oil in the claims should have V. I. of at least 80 and preferably 85 to 115. The

oil will preferably comprise 75 to 94%. of the composition and the soap from about 6 to 25%,

although these limit may be exceeded forspecific purposes.

What is claimed is:

lated as me oleic 'acid.

consistingessentially or aminer'al base meacating oil having a viscosity index of at least '80 thickened to a grease consistency with a mixed sodium-barium soap of fatty acid having an average of less than 18 carbon atoms, wherein the molar ratio of soda soap to barium soap is between 1 to 1 and 30'to '1 said grease containing a slight excess of said fatty acid suflicient to give a free acidity of 0.01 to 0.5% by weight, calcu- 2. A lubricating grease composition consisting essentially of to 94% mineral base lubricating oil having a viscosity of 50 to 500 SSU at 100 *F. and a viscosityindex of between and- 115,'and 6 to 25% of a mixed sodium-barium soap ofhyfdrogenated"'fish' oil acids having an average molecular composition of less than 18 carbon atoms and atleast 14 atoms, wherein" the molar ratioof'soda soap to barium soap is between lto 1 and 30 to 1 said grease having a sufiicient excess of said acids to give v.a free acidity of 0.05 to 0.5% by weight, calculated as oleic acid.

3. A lubricating grease consisting" essentially of ,80 to mineral base lubricating oil having a viscosity index of at least 80, about 10 to 20% of mixed sodium-barium soaps of aliphatic ,car.-

'boxylic acids having an average composition of more than 14 and less than 18 carbon atoms, wherein the molar ratio of soda soap to barium soap is between 1 to 1 and '30 to 1 about 0.1 to 1% of an antioxidant, said grease having a suflic'ient excess of said acids to give-a free acidity of about to 0.5% by weight, calculated as free oleic 4; .A lubricating grease composition consisting REFERENCES CITED h The following references are of record-in the file 'of this patent:

UNITED STATES PATENTS Number Name Date 2,005,553 Miller June 18, 1935 2,245;702f Morway June'1'7, 1941 2,318,847 Flint et a1. May 11, 1943 2,449,312 Murray et al Sept. 14; 1948 2,451,032 Morway et al. f Oct. 12,1948 2,468,099 Morway Apr. 26, 1949 2,487,080

Swenson Nov. 8,1949

Claims (1)

1. AN ANTI-FRICTION BEARING LUBRICATING GREASE CONSISTING ESSENTIALLY OF A MINERAL BASE LUBRICATING OIL HAVING A VISCOSITY INDEX OF AT LEAST 80 THICKENED TO A GREASE CONSISTENCY WITH A MIXED SODIUM-BARIUM SOAP OF FATTY ACID HAVING AN AVERAGE OF LESS THAN 18 CARBON ATOMS, WHEREIN THE MOLAR RATIO OF SODA SOAP TO BARIUM SOAP IS BETWEEN 1 TO 1 AND 30 TO 1 SAID GREASE CONTAINING A SLIGHT EXCESS OF SAID FATTY ACID SUFFICIENT TO GIVE A FREE ACIDITY OF 0.01 TO 0.5% BY WEIGHT, CALCULATED AS FREE OLEIC ACID.