US2057212A - Process for stabilizing mineral oils - Google Patents

Description

Oct. 13, 1936. B. H. SHOEMAKER ET AL 2,057,212

PROCESS FOR STABILIZING MINERAL OILS Filed Oct. 31, 1932 3 Sheets-Sheet 1 'lacgirgg Tzifiw (101259) flouns 6 Tmpcmtara-Dggrws F Jn0entor.s:- F Dermrdfthoamlwr MrzrzcthTzylor BYBMQI I ATTORNEY Oct. 13, 1936. B. H. SHOEMAKER Er AL 2,057,212

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J2me inJtoans drbvantor F Demamlflflzoarrzaker Kenneth Taylor BY BMKZ. BM

ATTORNEY Patented Oct. 13, 1936 UNITED STATES PROCESS FOR. STABILIZING MINERAL OILS Bernard H. Shoemaker, Hammond, Ind., and Kenneth Taylor, Chicago, Ill., assignors to Standard, Oil Company, Chicago, 111., a corporation of Indiana Application October 31, 1932, Serial No. 640,386

10 Claim.

This invention relatesto the stabilization of mineral oils and it pertains more particularly to a process and composition for preventing sludge and color formation in lubricating oils when used under conditions conducive to deterioration.

Mineral oils, and particularly lubricating oils, when used in internal combustion engines or under conditions where the oil comes in contact with hotsurfaces, deteriorate andform sludge,

P deteriorate in colonfcrm varnish-like products that deposit on the surfaces being lubricated and the viscosity of the oil increases with use. This deterioration of mineral oils is particularly noticeable with oils used to lubricate internal com- 3 bustion engines. The sludge formed collects on the piston rings and causes them to stick. Also, sludge collects in the oil pumps and oil lines and greatly retards the flow of oil and in some cases plugs up the oil lines and small passages.

' The object of our invention is to provide a method for stabilizing mineral oils and particularly lubricating oils against deterioration.

Another object is to provide a method for inhibiting thesludge formation of mineral oils by i adding to the oil an inhibiting catalyst.

Another object is to prevent the increase in viscosity of the oil upon continued use.

Another object'is to provide a method for prenventing color deterioration of the oils.

A further object is to provide a process for preventing the formation of varnish-like products in lubricating oils and the staining of the parts to be lubricated.

In internal combustion engines, it is very important that the lubricating oils be stable as to sludgeformation. We have found that motor oils have a great tendency to sludge and deteriorate at the high operating temperatures generally encountered in internal combustion engines such as are used in automobiles and airplanes. At these high temperatures it is common for lubricating oils to decompose and form sludge and coke on the pistons and in the ring grooves of the pistons. Thisresults in sticking of the rings which,

5 in turn,allows more oil to gain access to the cyl- 5 to note that a relativelysmall increase in temperature will greatly increase the rate of sludge formed. The sludge stability of the oil with reference to temperature, shown in Figure 1, was determined by heating a quantity of oil to the desired temperature and bubbling air through the sample at therate of liters per hour. At intervals, 10 grams samples were withdrawn and tested for sludge by the precipitation method described in American Society of Testing Materials Proceedings, volume 24, page 967.

Another undesirable characteristic of lubricating oils is their increase in viscosity upon use. The curve shown in Figure-2 illustrates this property of mineral oils. It will be observed that the Saybolt viscosity increases greatly upon use. The results expressed by the curve in Figure 2 were obtained by maintaining a Pennsylvania oil at 340 F. and bubbling preheated air through the oil at the rate of 100 to 150 liters per hour. It is apparent that when mineral oils are used at elevated temperatures'in internal combustion engines, the viscosity increases upon continued use and the oil will become so viscous that a heavy load is put upon the engine, especially when starting. This is particularly noticeable in cold weather.

Another common and undesirable property of mineral oils and particularly those lubricating oils used in contact with hot surfaces, such as in internal combustion e es. is the development of color. Curve A in Figure 3 shows the rate of color formation when a heavy Mid-Continent lubricating oil is heated to 340 F. while air is bubbled into the oil at the rate of 10 liters per hour. Curves B and C show the rate of color formation in the same oil when a small amount of sodium butylate and potassium butylate, re spectively, are dissolved in the oil. It is apparent from the curves that a small amount of these alkaline alcoholates are very effective for retarding color formation.

We have found that mineral oils, and particularly lubricating oils, can be stabilized against deterioration as illustrated by sludge formation, increase in viscosity upon use, staining of the surfaces to be lubricated and color formation, by adding to the oil a small quantity of an alkaline alcoholate or mixture of alkaline alcoholates. We have found that the alkali metal alcoholates and alkaline earth metal alcoholates, as well as the thio alcoholates, are particularly suitable for stabilizing mineral oils in this respect. The compounds used for stabilizing these oils have the following general formula:

wherein x-is a mono-valent alkaline metal and x1 is a di-valent alkaline metal, 13 represents an oxygen or sulfur atom and R. represents an alkyl,

cyclo-alkyl or aralhl radical or derivatives.

thereof. We may use the aliphatic alcoholates,

cyclic alcoh'oiates aralkyl alcoholates, examalcohols such as cyclo hexanol, cyclo butanol,

hydro phenols, cyclo hexyl mercaptan and the like; secondary and tertiary aralkyl alcohols such as benzyl alcohol, phenyl ethyl alcohol, dibenzyl alcohol, tolyl alcohols and thelike;

also the alkaline metal derivatives of organic compounds capable of forming the enolic structure, such as acetoacetic ester and ketones, are eiiective for stabilizing mineral oils. The tautomeric forms of acetoacetic ester are:

on I cnlc=cncooclm cur -c l cmcooclm The alkaline metal eel-mum or the enolic tautomer of the above esters and other compounds such as ketones contain the following characteristicgroup:

wherein R represents an alkalimetal.

' 'Ihe stabilized oils are prepared by dissolving a small amount of the alcoholates therein. The preferred amounts range from 0.1 to 0.5%, the

amount varying with specific materials. Howdesired.

ever, larger amounts up to 1% may beused if ;The following table'illustrates the results obtained with a heavy Mid-Continent lubricating oil, having an original true color of 21, when stabilized with alkaline alcoholatesat a tempera- .ture of 320 F. V 7

Table 1 Tnm Ior Sludglng Example Btabilizar Percent m a 5 (hours) hours hours 10 1 Control 1435 am an 2 (4H|0Na.- 0. I 248 87 3 041100 0.2 1% m 30 v 4v 0.4 m in 5 0.2 12 7B0 l 6 0.8 116 151 41 7 0.3 IN 478 41 8 0.4 m 12:0 9 .03 mo 10 0.8 82 111 42 ii 0.2 flit U5 as 12 Namethyl ethyl hclone--. 0.2 100 30 13 Na-mothyi ethyl vire 0.8 to 82 44 14 0.3 84 70 41 15 Nil-bitty (tort)- 0.2 an 1055 i0 nty 0.3 l3l 210 45 i7 Na-decylato. 0.4 675 18 Na-triothylena glycol: 0.3 516 lh-om the above table it is apparent that the alcoholates of alkaline metals 'are very eii'ective for preserving color and retarding sludge formation in lubricating oils. It shouidbe noted that formation in lubricating oils.

gained very little in color. Curves C and B in Figure 3 further show the extent of color stabilization 'over longer periods of time. It will be observed that'after-100hours, the color of the oil is substantially'one-third the color of the unstabilized oil. It should be further noted that V the alkaline-alcoholates derived from the low molecular weight metaissuch as lithium and sodium, and the high molecular weightalcohols such as butyl amyl and cyclo heal alcohols, are particularly eflective for stabilizing the oils against sludge formation.

The following table further shows the effectiveness of the alcoholates for inhibiting sludge The particular oil used was v a heavy Mid-Continent lubricating oil which hadbeen treated with 2 lbs.- of sulphuric acid per gallon of oil.

Table 11' V Sludge time in horns rcorm oi slud g l:

Control 02 NaOGJI- m5 0 o K0011!- 18 We have found it particularly desirable to add small quantities of an alcoholate to oils for seasonal storage to inhibit color and sludge formation. "As indicated by the above tables, it is apparent that the alcoholates are very eifective for inhibiting the deterioration of the oil.

As pointed out hereinbefore in connection with Figure 2, the viscosity oi the oil greatly increases as the oilis used and we find thatvthe presence of a small amount of alcoholatas will retard this increase in viscosity upon use.

The term "stabllim" is used in our application in a generic sense to include the of the oil against deterioration in any of the foregoing respects, such as sludge formation, color formation, increase inviscosity and the formation of varnish-like products. The alkaline compounds ;used in our invention are not reducing agents and their stabilizing action cannot be explained by the theory upon which the action of antioxidants is explained. However, it isthought that the deterioration oi. mineral oils is accompaniedvby the formation of intermediate acidic products, and the alkaline derivatives of compounds containing the alcoholate structure retard the formation of these intermediate acidic products and thereby stabilize the mineral oils against deterioration. Our invention is not limited to the specific alcoholats disclosed above, but it includes the, alkaline metal derivatives of other reference to certain oils and compounds, the scope of our invention is not limited thereby except insofar as set forth in the claims.

We claim:

1. A sludge-resistant mineral lubricating 011 comprising a viscous hydrocarbon lubricating oil and from 0.1 to 0.5% of an alkali metalalcoholate having the following formula:

X-BR wherein X represents a mono-valent alkali metal, B represents an oxygen or sulfur atom, and R represents an alkyl, cyclo-alkyl, or aralkyl radical.

2. A sludge-resistant mineral lubricating oil comprising a viscous hydrocarbon mineral oil and a small proportion of an oil-soluble alkaline metal alcoholate.

3. A sludge-resistant mineral lubricating oil comprising a viscous hydrocarbon mineral oil and from 0.1 to 0.5% of an alkali metal alcoholate dispersed therein, said alcoholate having the following formula: V

XBR

wherein X represents a mono-valent alkali metal, B represents an oxygen atom, and R represents an alkyl radical containing at least 3 carbon atoms, a eyclo-alkyl or aralkyl radical.

4. A sludge-resistant mineral lubricating oil comprising a viscous hydrocarbon mineral oil and from 0.1 to 0.5% of an oil-soluble alkali metal alcoholate having the general formula:

wherein X represents a sodium atom, B represents an oxygen atom, and R represents an alkyl radical containing at least 4 carbon atoms.

5. A sludge-resistant mineral lubricating oil comprising a viscous hydrocarbon mineral oil and a small proportion of an oil-soluble alkali alcoholate selected from the group consisting of sodium propylates, sodium butylates, potassium butylates, sodium amylates, potassium amylates,

lithium butylates, and the sodium derivatives of butyl mercaptan.

6. A sludge-resistant mineral lubricating oil comprising a viscous mineral oil and from 0.1 to 0.5% of an alkali metal alcoholate selected from the group consisting 01' sodium propylate, sodium butyiate, potassium butyiate, sodium amylate, and potassium amylate.

'7. A sludge-resistant hydrocarbon lubricating oil comprising a viscous hydrocarbon mineral oil and a small proportion of an alkali metal alcoholate selected from the group consisting of sodium propylate, sodium butyiate, potassium butyiate, sodium amylate, potassium amylate, lithium butyiate, and sodium derivatives of butyl mercaptan.

8. A sludge-resistant mineral lubricating oil comprising a viscous hydrocarbon mineral oil and a small proportion of an oil-soluble alkali metal derivative of the enolic form of an aliphatic ketone.

9. A sludge-resistant mineral lubricating oil comprising a viscous hydrocarbon mineral oil and a small proportion of an oil-soluble alkali metal derivative of the enolic form of an aliphatic ketone, said alkali metal derivative containing the following group wherein R represents an alkali metal.

10. A sludge-resistant lubricating oil comprising a viscous mineral oil having incorporated therein a small proportion of an oil-soluble alkaline alcoholate of the following formula:

wherein X1 represents a divalent alkaline metal, B

represents an oxygen or sulfur atom, and R represents an alkyl, cycle-alkyl or aralkyl radical.

BERNARD H. SHOEMAKER. KENNETH TAYLOR.

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