US2589973A

US2589973A - Lubricating grease composition

Info

Publication number: US2589973A
Application number: US124942A
Authority: US
Inventors: Jr Paul V Smith; Arnold J Morway
Original assignee: Standard Oil Development Co
Current assignee: Standard Oil Development Co
Priority date: 1949-11-01
Filing date: 1949-11-01
Publication date: 1952-03-18
Anticipated expiration: 1969-03-18
Also published as: GB683962A; NL73467C

Description

Patented Mar. 18, 1952 UNITED STATES PATENT OFFICE GREASE COMPOSITION lfaul fi s nith, J13, Westfield, and Arnold J. Morway, I iahway, N, 1., assignors to Standard Oil Development oe oean a corporation of Delaware NdDrawing. Application November 1, 1949, SerialNo. 124,942

eon a (01. 252-41) invention pertains to lubricatinggrease,

compositions oi-iinproved structural'stabilityicontaining hydrbxfy 'etheracidsoapsl' It rela es else.

nc ed;c ei j vd methera pha c en f his. en ral th ns-lee BirtB'tBttl Q O and 1 B (4, B iEF QQQE where R1 and R2 are aliphatic hydrocarbon groups of 3, to, 12 carbon atoms each, preferably, but not necessarily saturated, R3. is an aliphatic, hydrocarbon group, of 2 to 6. carbon atoms, and m, is an integer of at least 1, preferably 1 to. 2. 0]: l to. 3. Preferably, R1 and R2 arev 6 to 10 carbon atoms h nd the o a q i is car on at R3, contains preferably 2 to 3 carbon atoms. I he a ig t us. nta ns. refer b o 16 to 24 ca fbon'atoms, about, being specifically preferred. twill be not d that he (De-Rs. rad calin, th s hain mail be r e te 2 to 3 imes. Q e e imqre lneaxti u a an ac d o i rmu s Wa lace H? FQE H. A Q 3 i. e, the ether oi 12 hydroxy stearic acid, is found to he an especially suitable material for forming the soap, but th entir cla of om lo us sawrated acids, within the limits of chain length mentioned above. ma be em l e D ti of; certain unsaturated acids, such as ricinoleic,

may lso. be. used. emcneth sp c fic, compound which may be employed are.8-(I -hYG fQXY-E Vh: oxy) -stearic acid, 12- (fit-hydroxy-ethoxy),-stear ic. acid, 12 (e hydroxy-ai-propoxy) ricinoleic.

acid, 10-(B-hydroxy-isobutoxy) -pa1mitic acid, mixed hydroxy-alkyl etherv derivatives, of hydroxy acids prepared by chlorinatin fatty. acids and hydrolyzing the'chloroacids, etc.

In order to produce .the branched chain hydroxy ether. acids mentioned above, the, following metm 0d may be pursued. Hydroxy. acids, for example those. of natural occurrence, such as ricinoleic (hydroxy. stearic). acid, may. be, reacted with an olefin oxide such as. ethylene, oxide or, propylene oxide. The reaction maybe, carriedout. without a catalyst, but it is, preferable to use a Eliiedel Crafts. catalyst such asBFs, SnCh, or thelike,

For. example, 0.1 mol (3. gof; hydroxy, stearic. acid was. dissolved in toluene, containing 0.5 1nl.- of SnClr. The. mixture was stirred rapidly in a B-necked flask while 20 g. (0.45 mol) of ethylene oxide was bubbled The reaction temperati 1re was kept between, 5,01. and 609-. ,C. The solyent. was removed by. keeping. the flask ina steambath for several hours. The remaining. product, which solidified on cooling, was analyzed for acid and found to have an acid. value, of 0.21 1 centi-equiva lents. per gram, corresponding. to better than a purity of acid. The small non-acidic resi: dueprobably was toluene. With longer treatment on the steam bath, the acid may be made practi cally pure.

Other. hydroxy acids, both aliphatic and aromatic, appear to, react similarly. The production of the hydroxy ether, acids per se forms no part of the present invention but it may be noted that the. process just described appears to be applicable" to various hydroxy. fatty acids and to aromatic acids such as, salicylic acid, and th like. The former may be said to have the general formula mentioned abQYe. The branched chain aliphatic acids of fairly. high. molecular, weight are the ones of interest in gre se m nufactur It is particularly to be noted that the alkylene oxide radical may. occur. only once. or. it may, be repeated twice or more. In general, the acids actually produced in practiceare a mixture of branchdchain compounds having, respectively, one 'alkylene'e'ther and avatar even more alkylne ether groups. Acids with more than two "such groupsm senesapp ar "tobeprese'nt in very qea'1"'s,' if at all, under the reaction conditions (1 tribes abjove,butiifiderother condition they may appear 'insub ta tia'l prostrtions.

e er i 9 r ases FO l i P P e aps of these various products are undoubtedly affected by the number of alkylene oxide radicals in series. The invention includes the various reaction products just mentioned and, in particular, greases containing soaps of acids at least with 1 to 2 and in some cases, more alkylene oxide groups.

The specific formulas of the reaction products of olefin oxides and hydroxy acids may be written in several ways, including those given above. The products may take the formula where R1 and R2 have the same meaning as above and where R3, R4, R and R6, or any of them, may be either hydrogen or a methyl group. This alkylene-oxide group 'may occur only once or more than once, e. g., twice or more. Hence, m is an integer whose value may be 1, 2, 3, or even more, but usually 1 or at most 2.

The branched chain hydroxy ether acids just described may be converted to soaps by using the appropriate metal oxide, hydroxide, or carbonate, as will be obvious to those skilled in the art. 7

The alkali metal soaps, especially the lithium soaps. of such acids, are particularly meritorious, but the calcium, barium and aluminum soaps also may be used, and indeed the metals in general. These" soaps may be mixed with each other and/or may be used in admixture with conventional soaps, e. g., the alkali or alkaline earth metal, or aluminum soaps of straight chain fatty acids. In addition, conventional salts and/or soaps of low molecular weight, such as alkali or alkaline earth metal acetates, acrylates, propionates, furoates, and the like, may also be included in the ingredients. The combination of low molecular weight salts with soaps of higher molecular weight is often advantageous, as is now well-known in the art.

Soaps of the type characterizing the present invention may be used (alone or in combination with other andconventional thickeners, as mentioned above) to prepare greases of mineral lubricating oils, synthetic oils, or mixtures thereof. The following detailed examples show lithium and calcium soaps used in various oils and combinations of oils, but the invention clearly is not limited to the lithium and/ or calcium base greases or to the specific lubricants claimed. The im'provement in stability and other characteristics of lithium soap greases is noteworthy, and this is a preferred product.

The proportions of ingredients used may be varied within usual limits, although it should be noted-that somewhat smaller quantities of the branched chain hydroxy ether acid soaps of this invention may be required in some case to thicken .a grease to a givenconsistencythan is required of conventional soaps. As little as about 3% of the new type soaps, or as much as 35% to 40%, based on the weight of the total composition, may be used. According to the present invention, the newsoaps may be used alone or they may be combined with conventional soaps. In the latter case, the hydroxy ether acid soap preferably should comprise at least one-third of the total soap. Hence, a grease composition of the present invention will comprise at least 1%, up to a maximum of about 40% by weight, of hydroxy ether acid soap, with a total soap content of 3 to Preferred ranges are 6 to 20% total soap, which preferably includes not less than 2% of the hydroxy ether acid soap and at least 4% of additional thickener, the latter being either the same or some conventional soap.

In the specific case of lithium soap greases, the use of about 8 to 12% total soap is particularly preferred, at least one-third of which soap is of hydroxy ether acid. Where firm consistency is desired with minimum soap consumption (the lithium soaps being relatively expensive) a combination of about equal parts of conventional lithium soap (e. g., lithium stearate) and the hydroxy ether acid soap is particularly desirable. In the case of calcium greases, somewhat higher quantities, e. g., 20% or more of soap, appear to be preferable.

As suggested above, the present invention includes notonly a new composition but an improved process of preparing a composition having excellent properties of stability resistance to moisture, and the like. A grease is prepared, preferably by adding 1 to 40 parts by weight of the branched chain hydroxy ether acid (containing one or more alkylene oxide groups) to 10 to 96 parts by weight of mineral base lubricating oil. The mixture of oil and acid is next heated moderately with stirring to a temperature between 100 and 200 F., for example F. At this point, an aqueous solution of a saponifying agent, such as lithium hydroxide, sodium hydroxide, calcium hydroxide, or the like, is added in suitable quantity to neutralize the acid. An aqueous solution of lithium or calcium hydroxide, for example, is added at the temperature of about 150 F.

The mixture is next heated to a temperature of at least 212 F., and preferably a little higher, to dehydrate the grease andthereafter the temperature is further raised to cook the grease and form a grease structure. The cooking temperature is between 300 and-500 F., about 400 F. being preferred. During the various steps just described, the product is continuously stirred, preferably with a mechanical stirrer.

After cooking, the grease is cooled in thin layers, either in a close. clearance mechanical cooler or by pouring into thin layers in cooling pans or drum chilling. Thereafter, the product is homogenized and packaged.

Where it is desired to prepare a grease having extremely good temperature characteristics, for example, a grease to be used both at very low and very high temperatures as in the lubrication of airplane instruments, it may be preferable to use a substantial quantity of a synthetic oil, such as di-2eethylhexyl sebacate or the tri-ethylene glycol ester of 2-ethylhexanoic acid, or other related branched chain esters having outstanding temperature viscosity characteristics. Where such lubricants are to be used, it is preferred to prepare the soap in mineral oil, as described above, adding the synthetic oils after cooking to avoid hydrolysis of the esters. The proportions of mineral oil andester oil may be varied, but preferably at least 10% of the composition should be of mineral base oil. Aside from requirements for high and low temperature operation, the

mineral base greases are quite satisfactory in themselves.

If it is desired to prepare a lubricant which contains no mineral base oil, a preformed soap.v

should be used and dispersed thoroughly into the synthetic. oil; so. asto. obtain. a; good; grease structure. This may be done-.by-methods wells in. the; art. Conventional. greases. prepared;v eithen by forming: the. soaps.- of; straight chain. fatty acids. in situ or prepared. from; me.- formed soaps; are commonly deficient in: strut?-- tural stability especially when subj ected: to. heavy mechanical working. Greases prepared accord?! ing to: the method described above. are; superior: in this respect.

Thus, conventional lithium. base: greases. pre pared by forming: the lithium. soap. of stearic acid, hydrogenated fishoil acids, and the. like; in lubricating oil are structurally unstable. to l'ong'andsevere mechanical working. Thisinstae bility is readilyshown by workingthe.- grease. inthe standard ASTM? grease worker for about. 1000 strokes. The conventional lithium soap. greases break down into a semi-fluid product under this treatment.

On the other hand, greases prepared from the lithium soaps of hydroxy fatty acids, such as hydroxy stearic acidwherein the hydroxy group is attached: directlytothe main and. only hydrocarbon. chaizr. have good structural, stabilitybut they tend to. harden, under, high shearing; stresses. They also; possess comparatively. poor water resisting characteristics.

Accordin o. the present. invention,. gre ses prepared from: hydroxy ether acids. or. the. t p

described. above. have both good. structural. stability to mechanical working and a. good resistance: to. water; They. do not-harden under.- high shearing? stresses;

As another feature of the present invention, it: is: found that. the combination ofv the soaps oi: hydroxy'" other: acidswith. conventional soa s. y elds: a; crease: of. firmer consistenc for; a given quantity of. soap: than the conventional prod- Where: mixed; soaps; are so u ed. as; previously mentioned; the; hydr xy etheracid sea-P should; comprise at, least about one-third of; thetotalisoap; employed. Bet-terresults are obtained if approximatel equal quantities of conventional. or straight chain soap such as lithium stearate and the soap of the present invention are combined.

The invention will. be more fully understood by reference. to the following examples:

Example I 10.00% hydroxy' ether acid of; invention. of molecular weight. about; 363 (derived from. ethyl-- one oxide, treatment of- IZ-hydroxy stearic 1.23%. ItiOH-HiO 68.77% di-z -ethylhexyl. sebaoate 20.00%- reflned coastal type. mineral oil, of: 37

S. U. s. viscosity at: 2.10? F.

The hydroxy ether acid. evidently was. a mi ture of products containing a single ethylene oxide radical and two, or possibly more, ethylene oxide radicals in series. It was added to the cold mineral oil: andcharged to a fire heated grease kettle. The mixture was next warmed to 150 F. while agitating. Th lithium hydroxide, dissolved in boiling water, was next added to neutralize the acid and form the soap in mineral oil. After the mass was dehydrated (225 F.), the ester constituent. was added and the grease further heated to 400 F. The hot molten grease was then poured onto a drum chiller for quick cooling; The molten grease oncooling' was collected by scraping from thecrease kettle. on passing: through. a. Qorncll; homogenizer The; product- Qt: stable struts ture and had a texture.

Properties:

Free alkalinity (as LiQH).% 0.1.0.. ASTM worked penetration 77- Penetrationaiter work g. 1.. ..0.00.st.1:Qke

ASTM' worker employing fine hole worker plate mm../ 10 2,97

Dropping: point: u'- 351$ Appearance. tExcellent, smooth, buttery- Prepared in similar manneras shown in Example I; The grease was of a: softconsistency having a worked penetration at 350 mm./10 and a dropping point. of 326 F.

Example: 1 1' Equal. portions; f the. two. gr ases. p pared, above. were mixed. and; heated to. 4500* E: The; hotmolten grease at 400- F.,, wa poured; into pans in shallow layers and cooled". Aftercool:- ing, the grease was of excellent, smooth struc-- ture.

Worked penetration. at, 77 pm-[101... 3,10 Dropping point F. 3,44 Example. L1!

5.00% lithium stearate 5.00% lithium; soap.- of; acid. f iny riti0. .1. as. in;

, Example 90 .00% mineral. oil. in. Example The combined? soaps werev dispersed in. the mineral oil: at 4.20 E: and; c oled. By either rapid; cooling" h nla ers n cooling-- pans) or slow cooling, anexeellent smooth grease was obtained.

Worked; penetration, 60. strokes 77f Ea.

a Penetration. after 1.40.000 strokes worker- A few experiments. have been run also to determine the efiectiveness or the. calcium soaps as thiokeners for mineral oil: and estersp boiling water for 3 ,hours.

Klan acid, derived by treating l z-hydroxy stear-ic acid with ethylene oxide andhaving a molecular Weight of 363was employed. The following greases were prepared.

Example VI 20.00% hydroxy-ether acid 2.30% hydrated lime 77.30% naphthenic-type oil of about 100 S. U. S. viscosity at 100 F., and 40 S. U. S. at 210 F.

Example VII 20.00% hydrofol acids 54 (hydrogenated fish oil acids) Stearic acid could be used instead.

3.00% hydrated lime 77.00% mineral oil as in Example VI Prepared similar to above Example VI.

' EzrampZe VII I.

The two greases of Examples VI and VII were mixed together in equal proportions and heated to 250260 F. (Grease fluidized at 275. F.) On cooling, an excellent smooth greaseofexceHent structure stability wasformed. Ioi about 220 mm./10 penetration. 4

Dropping point, 288 F. Boiling water test-10 grams of grease placed in No disintegration .or separation of the grease. No cloudiness in In preparing greases according to this invention;.-the:. particular metal oxide or hydroxide used for-saponification should be selected that-is most suitable for the intended purpose. The lithium and'calcium base greases have good water resistance. Lithium greases show. superior stability but of course the calcium greases are less expensive. Soda base greases may readily be prepared in the same manner but they'are-"less water resistant. Mixed base greases of these and other metals also may be prepared.

While the foregoing examples all relate 'to'" the lithium and the calcium soaps, some of which are commonly more'difiicult to prepare than the more conventional metal base products, it will be understood that various other metal bases will be used with equal-facility and with comparable beneficial results. It will also be understood that conventional additives maybe included in the! grease compositions without altering theimbasic properties; Thus, the usual apti-oxidants, corr s oain b eek n aasem ext p e liegsejcbp ij wherein R1 and R2 areialkyligroupslof .3 to -12 2-to 6 carbon atoms;v

2. A'lubri'cating grease composition consisting" essentially of a lubricating oil thickened to a grease consistency with 3 to 40% of soap of allphatic carboxylic acid, at least one-third of said soap being 'a metal soap of branched chain hydroxy aliphatic acid of 18 to 23' carbon atoms, the hydroxy group being on a side chain and the acid radical containing at least one C2. to C3 alkylene ether group in a side chain.

3. A lubricating grease composition consisting essentially of a lubricating oil thickened; to agrease consistency with a metal soap of aliphatic carboxylic acid, said thickener comprising at least one-third part by weight of a metal soap of a hydroxy ether acid having the general formula Rs I'M e -0E (I: R5 in a1- HRz'oooH wherein R3, R4, R5, and Re are each selected from the class consisting of methyl groups and hydrogen and wherein R1 and R2 are each alkyl groups of 3 to 12 carbon atoms, totaling 14 to 18 carbon atoms. v

4. Composition according to claim 3, wherein said oil comprises a synthetic ester oil; I

5.-Composition according to claim 3, wherein said oil is mineral oil.

6. Composition according to claim 3, wherein said soap of hydroxy ether acid is an alkali metal soap Y 7. Composition according to claim 3,'wherein said soap of hydroxy ether acid islithium-soap.

8. A lubricating grease composition consistin essentially of a lubricating oil thickened to a grease consistency with about 8 to'12 by weight, based on'the total composition, of soap" of :aliphatic carboxylic acid which includes at'least' one-third part of lithium soap of an acidhaving the general formula u I 5-3 m-bn-RJ-do. onwherein R1 and R2 are alkyl groups of 6 to 10 carbon atoms each, totaling 14 to 18 carbon atoms, n is 2, and m is an integer of 1 to 3.

9. Composition according to claimiZ-wherei'n the metal of the soap is an alkali metal.

10. Composition according to claim 2 wherein the metal of the soap is an alkaline earth metal.

11. Composition according to 'claini'i2 wherein the metal of the soap comprises lithium: 12'. Composition according?to-iclainrrztwhereiir the metal of the soap comprises calcium,-'

13. Composition according toclaim 3, wherein thehydroxy ether acid has the formula c lmcmon F 0 cngcnmtnqcnm ooon" 15. The process of preparing a stable metal base grease which comprises-adding; toflO parts by weight of a branched chain hydroxy ether carbon atoms each and R; is an alkyl group of saturated aliphatic acid of 17 to 23 carbon atoms and having the hydroxy group on a side chain, to 10 to 96 parts of mineral base lubricating oil, heating to a temperature of 100 to 200 F., adding an aqueous solution of a metal base to saponify said acid in situ in said oil, heating to a temperature of at least 212 F. to dehydrate, adding a synthetic ester oil, further cooking to a temperature of 300 to 500 F. to form a grease structure, and cooling in thin layers.

16. Process according to claim 15, wherein the metal base is lithium hydroxide.

1'7. Process according to claim 15, wherein the metal base is calcium hydroxide.

18. Composition as in claim 8, wherein the lubricating oil comprises a substantial proportion of di-2 ethylhexyl sebacate.

19. Composition as in claim 8, wherein the lubricating oil comprises a substantial proportion of tri-ethylene glycol ester of 2-ethylhexanoic acid.

PAUL V. SMITH, JR. ARNOLD J. MORWAY.

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

UNITED STATES PATENTS Number Name Date 2,435,328 Guest Feb. 10, 1948 2,435,829 Guest Feb. 10, 1948 2,436,347 Zimmer et a1 Feb. 17, 1948 2,450,221 Ashburn et a1 Sept. 28, 1948 2,457,640 Bruson et a1 Dec. 28, 1948 2,475,589 Bondi July 12, 1949 FOREIGN PATENTS Number Country Date 615,188 Great Britain "Jan. 3, 1949

Claims

1. A LUBRICATING GREASE COMPOSITION CONSISTING ESSENTIALLY OF LUBRICATING OIL THICKENED TO A GREASE CONSISTENCY WITH 3 TO 40% BY WEIGHT, BASED ON THE TOTAL COMPOSITION, OF METAL SOAP OF ALIPHATIC CARBOXYLIC ACID, SAID METAL SOAP COMPRISING AT LEAST ONE-THIRD PART OF A SOAP OF AN ACID HAVING THE GENERAL FORMULA