US2514296A - Solvent resistant low temperature lubricant - Google Patents

Description

y 1950 w A. B. SMALL ETAL 2,514,296

SOLVENT RESISTANT LOW TEMPERATURE LUBRICANT Filed Dec. 19, 194':

WATER. wan GH'T PERCENT 40110090 E10 70 0O 50 4Q 30 2O {O 'O O 10 2O 3O 4O 5O 6O 7O 60 90100 ETHYLENE Gun/cop WEIGHT DEJLCENT c? i Q5. .5 11 fi gg'i 71 52 5 Un embers B MQLQbbm-rzag Patented July 4, 1950 UNITED STATES PATENT 2,514,296, v v a A sonvnnr REsIsrANT LOW' TEMPERATURE LUBRICANT 7 v Augustus Small and Robert M. Thomagfiaton Rouge, La., assignors to Standard Oil D'evl'o'p- 'inent company, a corporation of Delaware Application"Deceriiber19, 1947, SefialNo. 792,700

. 1 M This invention relates to solvent resistant lubricants and particularly to' extremelyr low temperature lubricants which are highly resistantto hydrocarbon solvents and related compositions.

In the lubrication of machinery or equipment used in the presence ofrcer'tain solvents. at very low temperatures, considerable difficulty has been encountered in securing a composition which has the necessary low temperature lubricatingchara'cteristics and at the seine time is not soluble in hydrocarbons and other solvents of oils, greases, and the like.

It has long been known in the prior art that certain 'polyhydi'ic alcohols; such'ias glycerin and the various glycolshave certain lubricating characte'ri'stics and also that they may be'used at moderately low tmpe'ratures under some conditions; These'materials'halve been usedfor lubricating refrigeratingn'lachinery and the like with limited success biitliaive not been at all satisfactory for us'e at very low temperatures; e. g. below about +100 F.',:sin'ce t'hey'solidify. These same materials are also subject tothe limitation that they are too low in viscosity'at normal or slightly eievstedtempram res; 4

It'is an object or the present invention" to modify lub'iioar-its of'tlie an insoluble type, especially polyhydric alcohol type lubricants, in -such a way as tdara'ruaemuserui as lubricants in the presence of hydrocarbon and other organic solvents.

It is a further object to prepare a lubricating compositionbased on the use of lubricating properties of-polyhydric alcohols Which Will be useful at various temperatures, especially for lubri- 4, n. insane i i ma e irfg oils of miner-arch type 'iiiay'bethickened to produce lubricating rease compositions by the use of various metalisalts retty acids. it is alsoknow; that thep'olyliydriclalcohols, such as glycerin and the ag e-e1 arei elaaveiy insolublein 4 iistjdescribed, E1": e .m the prior a t, without s, to use "someof .the'alkali met'al soaps combination v viitl'i gncerm for; lubricatin g piirpd s l" flow discovered, how ever that ice tain steps, i} e nietals alts'. of -fatty acids vvli'ch vare I t ordinarily compatible with 1 b b fi h 1 g ably. with a de'fi iiteiamountfof water ss pointed out liereirlaften to remiss s; rsaery ubrmatihg coiiip sit ns f r u eat. v

(1 equipment in the preser ally I incompatible temperatures; we'tave isca trea asti hat as;

8 Claims. (01. 2'52-3'3.s)

wherethe polyhydric alcohol does not satisfacy h oa wh c isuuc ed th i tin properties and thernechanical stability of such compositions are materially improved by the use of a Sm l am nt zitab e w t n a nt r surface active material, {The present invention is particularly characterized by the I use of an optimum amount of water with the polyhydric aloe-- hol to l w i fieci re so id fi ation te r t r It a in o re Preferably h se. Q a we face acti a ri ,.sn fi a a w i nga i to s re a .int ma em xtqre 01 M! w th u c n oc m f ex rem vnl wr m ra ur characteristics to lubricants of the polyhydric o a dso n pev, a r

Fo -t e ub cat on of aahine r w ch us operate in v the presence of lici uid hydrocarbons, ps aIOne hare b iilu edto a limited. x t but the soaps, ,vvhen used alone arecuite unsatis ac r be use ihe ld 119 p ovi meq d lu ea fi ms a d thafi cro ded r 1 1 3 9 Su l rica s. dqr t remain. fi t v to reduce r ion, err stsndesi e iod iii m Ithas also been suggested in the prior-art that certain Q DS;.S l' as th sq ium s ap mi t e emuls f ed withglycerin and oil'to provide lubricants for use in the presence of hydrocarbons or at moder-r ately low temperatures These are usable attemperatures ofthe order of 0 0, ora few degrees below,but they arenot satisfactory for extremely Other soaps of saturated or unsaturated aliphatic acids, u h a t ahn iaiea: e r a and t li and m xtur s t r on a e co n clz n. fi ly edf rmtwiih o h d e l ho a d a m lla oun of w te tq rma g l em:

perature lubricant, If the soap-is not wetted flihe, ly dr c; a c h lra Small u nt t Wet e t sho l bez iplp sl, t b a n a stablecomposition. Other known bodying agents for grease may; be used instead of soaps for some purposes; Examples are carbon black or 13611130111 ite which-maybe used singly or in;. combination and with oriyrithout soaps but the preferred thickening agentsare the metal soaps; of the 5 fatty acids whi h a e o iat ordina te a-v tures and-which are not water. soluble; ;-,I'he=s0apsshould be very finely divided to obtain-a fine grained stable composition. w

As the principal liquid liibiicating ingredients ofgreasesmade according to the present invenby themselves, solidify at temperatures only a few degrees below the freezing point of water, but those which are useful in the present invention have the peculiar property of remaining plastic f or soft and grease-like in texture at temperatures far below their normal freezing points andeven as low as -150 F., or lower, when combined. with optimum quantities of water. Certain of the'socalled carbitols, i. e. mono'alkyl ethers of diethylene glycol, have fairly low freezing points per se, but the important criterion is not the freezing point of the alcohol as such but rather the hardening point or the point below which the lubricant ceases to function effectively as a lubricant. The carbitols are mentioned in Morgan Patent No. 2,383,915 as possible low temperature lubricants, for example temperatures that are subzero but above 40 F., but they are not suitable per se for use at extremely low temperatures such as 100 F. or below.

Thus the use of an optimum amount of water with the polyhydric alcohol, or derivative, so as to retain a degree of mobility at verylow temperatures is adistinct and important feature of the invention, although in some compositions and for some purposes it is not absolutely essential. The optimum amount of water varies somewhat with the polyhydric alcohol or ether employed but in general it appears to lie between and 50% by weight and usually between 25 and 35% based onthe composition of the alcohol (or ether) plus water. In the case of ethylene glycol, for example, the optimum composition of the glycol and water is about 70% glycol and 30% water by weight. With glycerin the optimum water content appears to be about the same.

The use of a wetting agent has been mentioned as a desirable feature'of the invention. When a soap is used which is not soluble in the polyhydric alcohol, the wetting agent renders the soap compatible with the polyhydric alcohol, or

the alcohol-water mixture. The water-insoluble soaps are normally preferred and hence the use of a wetting agent ordinarily is essential. With some compositions, and for some purposes, however, it maybe omitted.

The sulfonates are satisfactory wetting agents, as are also the oleates, etc.,-of polyhydric' alcohols, such as'pentaerythri'tol, and the like. The wetting agent employed may be selected from a wide variety of known agents, so long as it is effectiveto promote the formation of an intimate mixture of the metal soap and the poly-- hydric alcohol or equivalent liquid lubricating material. Ordinarily the quantity of wetting agent required is'very small, for example of the order of 0.1 to 0.5%, based on theliquidlubricant (i. e. without soap). A broader range of 0.01 to 5.0%, based on the entire grease composition appears to have utility, but in general a quantity of the general order of 0.1 to 2.0% appears quite satisfactory. The wetting agent may be omitted only if the soap is adequately wetted by the polyhydric alcohol per se.

Example 1' A liquid lubricant composition without water 4 was first prepared, consisting of a mixture of 29% by Weight of finely divided zinc stearate and about 71% of glycerin with a very small amount, about 0.1%, based on the glycerin, of a wetting agent. The particular wetting agent used in this example was a dioctyl sodium sulfosuccinate having. the formula NaOSOznoooc n The composition of Example 1 was a grease like material having the finely divided soap well dispersed in the glycerin. It was tested by the use of a standard ASTM penetrometer at various temperatures and was found to have a penetration at 11 F. of 250. At -108 F. the penetration was only 36 and at -142 F. it was 0. The latter indicates that the grease was solid at 142 F. but it still had a slippery feel, doubtless due to surface melting and could provide some lubrication even at that low temperature.

Such a grease would provide satisfactory lubrication down to about 108 F;

. Emample 2 Another example of a grease prepared without the use of water, was a composition consisting of about 50% by weight of zinc stearate, 50% by weight of a glycol (ethylene glycol) and 0.1% by weight of the wetting agent referred to in Example 1. This material was found to have a grease-like consistency at quite low temperatures, as also was the case in Example 1, the penetration being 250 at 1l F. and 10 at -142 F. Thus the composition of Example 2 was somewhat softer at the extremely low temperature than that of Example 1, indicating that ethylene glycol grease is somewhat better than glycerin base lubricant for extremely low temperature lubrication. It was still objectionably hard at the very low temperature of -142 F. but would lubricate satisfactorily down to about F.

Example 3 Another example of a grease including water, according to the present invention, was prepared in the form of a composition having the follow-.

sodium sulfonate itself isa salt obtained by neutralizing with NaOH the oil-soluble sulfonic acid produced by treating petroleum residuums or heavy oil fractions with strong sulfuric acid.

The composition of Example 3 was tested for penetration in the same manner as Examples 1 and 2 and was found to have a penetration of 250 (25 mm.) at -11 F. and 30 (3.0 mm.), at 142 F. This indicates that ethylene glycol, with a relatively small amount of water, mixed with a suitable thickener such as zinc stearate, has a softer consistency at very low temperatures than the non-aqueous compositions of Examples 1 and 2'. In general, the glycols are somewhat softer than glycerin at very low temperatures and they are therefore useful at somewhat lower temperatures. The use of the wetting agent, sodium sulfonate in this instance, served to maintain physical stability of the lubricant, preventing separation of the finely divided soap from the lycol and water,

The lubricant composition of Example 3 was usedover an extended period in a butyl rubber reactor operating at low temperatures most of the time. The reactor varied over a temperature range from -150 F. during normalproduction of polymerupto +160 F. during times when the reactor was being cleaned. Under allconditions, the lubricant of Example 3 was .found to give satisfactory performance. The composition of this example, though not a true grease in the sense of having a micelle structure, was greaselike in appearance and maintained-good plasticity and moderate torque resistance even atthe extremely low temperatures indicated.

From the foregoing data it is evident that lubricants of the glycerin or glycol type may be thickened to a grease-like consistency by the employment ofsuitable soaps, such as nine stearate, for example, or-any of the oil-insolublesoaps, where the grease is to be unaffected by hydrocarbons, in various proportions. Proportions preferred are 'from 20 to 50% of Zinc stearate or equivalent soap, based on the total composition. Amounts :as low as about up to as high as 60 1% or more of thesoap may be-employed, depending somewhat upon the intended operating temperature. When the-soap is not wetted by the polyhydric alcohol, as is the case with zinc stearate, .a wetting agent is employed.

The wetting agent must be soluble at least to a moderate degree in the polyhydric alcohol and preferablyshould have a greater afiinity'for the metal to be lubricated than has thehydrocarbon liquid or other solvent which is present at the pointof lubrication. When such wetting agents are :used, theyappear to .help to establish onthe metallic surface to be protected a more stable lubricating film which is not readilyremoved by the hydrocarbons.

Various wetting agents, preferably of the sulfonate type, maybe employed in suitable concentrations, usually within the limits of .01 up to 5%, based .on the total composition. The secondary alcohol sulfonates are among those especially preferred. These may be conventionally .prepared by reacting anappropriate secondary alcohol with maleic anhydride followed byaddition of .sodium bisulfite. Alternatively, an appropriate petroleum fractionmay be sulfonated and the sodium or other alkali or alkaline earth metal sulfonate obtained and used in small proportions, for example 0.01 to a maximum of about 5.0%, based on the weight of the total composition. The composition of Example 3, of about 47% zinc stearate, about 37% glycol, about 8% water, and about "33 of the 25% alcohol-solution of wetting agent quite satisfactory.

While the sulfonate etype wetting agents are preferred, by which .is meant the conventional petroleum sulfonates, the salts of sulfonat'ec alcohols and of the sul'fonated aliphatic ester: such as dioctyl sodium sulfo+succinate described above, and their obvious equivalents, it will be understood that other surface active agents, such as some of the esters, may be employed. Certain of the aliphatic alcohols, *for example, isopropyl alcohol, have some Wetting properties but these alcohols are notsatisfactory for use, for example in lubricants for low temperature operation as in butyl rubber reactor machinery, because the solvents present, such as methyl chloride, would dissolve and extract the monohydric alcohols out of the lubricant. In all cases, it is desirable, as noted above, that the wetting agent should have agree argreater aifinity for the metal to be lubricated thanhasthe solvent to be resisted.

In the accompanying drawing, there is shown graphically the eifect'ofwat'er on the penetration characteristics of a-grease type 'lubricant'consisting of water, ethylene-glycol and zinc stearate at a very low temperature of 142 F. The composition of'this figure had a solid-liquid ratio of-52.6%'liquid and 47.4% solid. The glycol and water, of course, varied. Otherwise, the composition was-essentially that of Example 3. The figureshows the striking effect of "the use of water at the very low temperature of 142- F. and it Will be noted that ethyleneglycol is softened or plasticized to'the maximum extent bya water content of approximately 30%byweight, based on the total composition of water plus polyhydric alcohol. The same is true to a large'degree of other polyhydric alcohols although the glycerin base lubricant, as noted above, is not nearly as soft, penetrable, or grease-like at this temperature as ethylene glycol, the latter being much superior for 'such'very'lowtemperature. The low penetration mumbr *of glyce'rin lubricant, Example 1, indicates conside'rable resistance to rotation or somewhat "inferior lubrication at very low temperature. I 7

The formulation-given above in Example '3 retains mobility at much lower 'temperatures than prior art compositions suchffor example, as those typifiedbythe Morgan PatentNo. 2,383,915 mentioned above. The diiference appears to be attributable mainly tothe presence of water, although the superior physical properties due to the use ofa wetting agent also'contribute. For example, ethylene glycol "alone shows a penetration of '50'at 142 F. whereas'a 70:30 mixture of glycol and water, under similar conditions, shows a penetration of 250. Mixed with zinc searate,- ethylene "glycol alone shows substantially no penetration at -l42 'F.

-Asindicated above, various glycols and derivatives thereof such as the monoalkyl ethers of ethylene glycol and the like maybe employed. As suggested above the freezing point of the glycol per se is notparticularly significant as long as the lubricating properties are preserved at operating temperatures by the effects of the water an'dto some extent, of the "wetting agent. Byuse o'fthe latterflthe mobile properties of the grease are improved, apparently, because of the unusually "intimate mixture of soap and liquid lubricant which results.

in some of the cases referred to specifically above (Examples 1 and '2) normal octyl alcohol wasreacted with maleic anhydride and sodium bisul fite to produce the particular wetting agent, but it will be understood that various other wetting agents may be used, as suggested above. While the proportions may' be varied somewhat, they usually will not exceed about 2%.

"The following table shows further "data obtained by-corhparison of compositions of glycerin or glycol (ethylene glycol) wither-without water, using various 'thickene'r's "and, in some cases, a wetting agent. In -general,'the soap ty'pe'thickeners are'better for very'low temperatures. The superior mobility-at -142 F. of a glycerin soap composition containing water over those which do not contain it is apparent from a comparison of Examples 4 and 6. The composition of Example 6 is relatively stiffer because it contains more soap. The data were obtained in the usual manner in conventional grease penetrometers by the ASTM procedure, where readings are penes nate 7 tration depths of the standard penetrometer in tenths of a millimeter.

Table I Example Composition Penetration Zinc stearate, 29.00; 4 {Glycerim 7O.943 2" 3 yettntig agent 06% mcs eara e,4 5 5 Ethylene glycol, 49.95 if jgf 53+ Wetting agcnt, 0.l0%.

30% H50 to 70% glycetm, 65.03% At o F 9 6 Z1110 stearate, 34.80% At 5 Wetting agent, 0.l7

30% E20 to 70% diethylene glycol, 7 33.00 At142 F., 0

Bentonite clay, 67.00% 309i, to 70% diethylene glycol,

7 O 8 Bentonite clay, 14.30% M 0 Zinc stearate, 14.30%.

1 This wetting agent was a commercial product, known as Aerosol 0Tconsisting of dioctyl sodium sulfosuccinate in 10% aqueous solution. Analogous esters of sulfonated dibasic or bicarboxylic acid, such as succinic acid and its homologues may be used.

It will be noted from the foregoing that bentonite, which is wetted naturally by polyhydric alcohols of the glycerine-glycol type may be used in lieu of soap as a thickener. The same is true of carbon black. The latter behaves very much like zinc stearate whereas bentonite has a greater stiffening effect, as indicated in Example 7. The bentonite grease retains mobility down to about -108 F.

The solid ingredients are needed to prevent loss of the lubricant when the temperature is raised. At very low temperatures the polyhydric alcohol and water mixture sets to a soft gel of grease-like consistency, but as soon as the temperature is raised, for example to 50 F., it becomes quite fiuid and loses most of its lubricating value. Hence the preferred composition contains enough thickener to prevent complete liquefaction upon foreseeable temperature rises. The amount of finely divided solid thickener may very widely but usually it will be not less than about 10% by weight and it may be as much as about 60% of the total composition.

Although the optimum quantity of water is preferred, it will be noted from the foregoing data that in some special cases water can be omitted. It may be used with polyhydric alcohols in proportions up to a 50-50 mixture. Preferably at least of the liquid constituent should be water, the range of 25 to 35% and especially about 30% being particularly preferred. Hence the over-all composition may comprise 10 to 60%, preferably to 50%, of a hydrocarbon insoluble thickener such as zinc stearate, other soaps, or other grease thickening finely divided solids, and 40 to 90% of liquid constituent, essentially hydrocarbon insoluble polyhydric alcohol preferably containing enough water to materially increase its fluidity at very low temperatures, e. g. at -100 F. or lower. Preferably, also, the composition contains a small amount of wetting agent unless the solid thickener is directly wetted by the alcohol as explained above.

The preferred polyhydric alcohol compounds are the aliphatic alcohols-having 2 to 4 carbon atoms, glycol, glycerol, and glycol ether (diethyl- 8 one glycol) being specifically preferred. Others of similar characteristics as regards low temperature gelation, especially with water, may be employed.

We claim:

1. A lubricating composition resistant to hydrocarbon solvents consisting essentially of 40 to by Weight of a polyhydric alcohol having lubricating properties, said alcohol being selected from the group which consists of glycerine, C1 to C4 glycols and the lower monoalkyl ethers thereof which have freezing points below 0 0., combined with enough water to substantially increase iluidity of said alcohol below a temperature of about F., 10 to 60% of zinc stearate, and 0.01 to 5.% of a sulfonate type wetting agent which has a greater affinity for the surfaces being lubricated than said solvents to maintain dispersion of said stearate in said alcohol and water.

2. A composition according to claim 1 wherein said polyhydric alcohol is glycerin.

3. A composition according to claim 1 wherein said polyhydric alcohol is a glycol.

4. A composition according to claim 1 wherein said polyhydric alcohol comprises ethylene glycol.

5. A composition according to claim 2 wherein said wetting agent is a sulfonated maleic acid ester of a secondary alcohol.

6. A composition according to claim 2 wherein said wetting agent is a dioctyl sodium sulfosuccinate.

7. A lubricating composition having approximately the following formula Per cent Zinc stearate 47.4 Ethylene glycol 36.8 Water 9.8 Isopropyl alcohol 4.0 Oil-soluble sodium petroleum sulfonate 2.0

8. A lubricating composition resistant to hydrocarbon solvents consisting essentially of 40 to 90% by weight of a polyhydric alcohol having lubricating properties, combined with enough water to substantially increase mobility of said alcohol below a temperature of about -100 F., 10 to 60% of zinc stearate, and 0.01 to 5% of dioctyl sodium sulfo-succinate.

' AUGUSTUS B. SMALL.

ROBERT M. THOMAS.

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

UNITED STATES PATENTS Switzerland Mar. 1, 1939

Claims (1)

1. A LUBRICATING COMPOSITION RESISTANT TO HYDROCARBON SOLVENTS CONSISTING ESSENTIALLY OF 40 TO 90% BY WEIGHT OF A POLYHYDRIC ALCOHOL HAVING LUBRICATING PROPERTIES, SAID ALCOHOL BEING SELECTED FROM THE GROUP WHICH CONSISTS OF GLYCERINE, C1 TO C4 GLYCOLS AND THE LOWER MONOALKYL ETHERS THEREOF WHICH HAVE FREEZING POINTS BELOW 0*C., COMBINED WITH ENOUGH WATER TO SUBSTANTIALLY INCREASE FLUIDITY OF SAID ALCOHOL BELOW A TEMPERATURE OF ABOUT -100*F., 10 TO 60% OF ZINC STEARATE, AND 0.01 TO 5% OF A SULFONATE TYPE WETTING AGENT WHICH HAS A GREATER AFFINITY FOR THE SURFACES BEING LUBRICATED THAN SAID SOLVENTS TO MAINTAIN DISPERSION OF SAID STEARATE IN SAID ALCOHOL AND WATER.

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