US2383147A - Low temperature greases - Google Patents

Description

Patented Aug. 21 1945 UNITED STATES PATENT OFFICE LOW TEMPERATURE GREASES John D. Morgan. South Orange. N. 1., assignor to Cities Service Oil Company, New York, N. Y., a. corporation of Pennsylvania.

No Drawing. Application August 27, 1942,

Serial No. 456,365

5 Claims. '(cl. 252- 36) This invention relates to low temperature greases. More specifically the invention'relates to those greases which have a comparatively uniform viscosity throughout the temperature range in which the grease is to be used.

I have discovered'that many synthetic alkyl esters of organic acids are good lubricants and are well adapted for the manufacture of low temperature greases. Examples of such alkyl-esters are--alkyl ricinoleates, alkyl lactates, alkyl benzoates and dialkyl oxalates. These esters have very goodviscosities which adapt them for making low temperature greases but these esters are quite expensive compared to the cost of mineral oil lubricants. 7

vI have also found that greases made from synthetic esters are-compatible with greases made from mineral oil lubricants and when these two greases are blended a comparatively V small amount of alkyl ester grease will greatly improve the low temperature viscosity characteristics of the mineral oil grease. low temperature grease may be made by using a small amount of a'more expensive synthetic ester grease blended with a mineral oil lubricant grease. i

The primary object of the present invention is to provide an improved low temperature grease by utilizing a blend of a mineral oil and asynthetic alkyl ester grease.

Experimental-work has shown that the synthetic esters do not form stableemulsions with all of the alkali and alkaline earth metal soapsof fatty acids. Further the technic of making greases with synthetic esters is different from the technic of making greases with mineral oils. I

have discovered, however, that up to 30% of stable greases made from synthetic esters may be blended'with greases made from mineral oils and still stay in stable suspensions.

. Accordingly another object of the invention is to provide a method or making a stable grease when using a substantial proportion of alkylorv ganic ester lubricants'in combination-with a mineral oil lubricant base;

In my work on lubricants I have found that al- -kyl esters of monoba ic acids, such as ricinoleic and lactic acids, and he aliphatic esters of dibasic acids, such as oxalic acids have the proper boiling point, melting point, and viscosity characteristics, which adapt them for lubricants. I have also found thatthe alkyl esters of aromatic carboxylic acids, such as the benzoates, have the Proper physical properties to adapt them for lubricants.

Accordingly an effective Temper- Viscosity ature, F. centistokes -4o 69. 5 Ethyl lactate" g g g 200 75 135 Butyl lactate l, .Q 8 g 2 200 l 93 40 231 Isobutyl lactate 8 3:1 200 .93

Tests have shown that the methyl, ethyl, butyl,

and -propyl acetyl ricinoleates all havelubricating properties and desirable viscosity characteristics. For example, butyl acetyl ricinoleate has the following kinematic viscosities:

Temperature, Viscosity F. centistokes 1 Very viscous.

The alkyl lactates have boiling points and melting points-which well adapt them as lubricants. For example, ethyl lactate boils at 311 F., butyl lactate at 370- F., and isobutyl lactate at 350 ingviscosity characteristics:

to 390 F.. These alkyl lactates have the follow- The dialkyl oxalates'have very desirable boiling and melting points which adapt them for low temperature greases. Viscosity characteristics of diethyl and dibutyl oxalates are as follows:.

Temper- Viscosity ture, F. ceutistokes -40 14. Diethyl oxalate 8 200 -40 0 Dibutyl oxalate 100 2. r 200 e l.

The physical properties of the alkyl benzoic a i esters are well adapted-for the manufacture grease in that the boiling point of these esters is high, the productsare practically all colorless liquids and the melting points are verylow. The

vi'scosities of some of these esters have been determined as follows:

Temperature, degrees F.

l Viscous.

A lithium base grease can be made from a mineral oil lubricant preferably, a lubricant of a naphthenic base crude oil, by blending from 4 to 12% lithium stearate with 86 to 96% naphthenic base oil and from .5 to 3% aluminum stearate. Preferably 1% of an antioxidant, such as tributyl phosphite and sulfurized tricresyl phosphite may be added to the mineral oil prior to the blending of mineral oil with the lithium soap. Other soaps .may be used for blending with the mineral oil lubricant, such as sodium and potassium st'earates, or sodium, potassium and lithium scans of other fatty acids. It is preferred, however, to

. use the lithium soap because such soaps are found to have better low temperature viscosity characteristics.

A stable grease may be made using an alkyl acetyl ricinoleate as a lubricating base. For example, a grease has been produced utilizing butyl 'acetyl ricinoleate 93%, lithium stearate 6%, and

.To this ricinoleate is of desirable viscosity. A

aluminum stearate 1%.

preferably added 1% ofan extremepressure lu-' tates when using sodium or calciumbase rease,

for example sodium or calcium stearates, oleates or palmitates. -A stable grease that will not bleed has been made using 93% ethyl lactate, 6% so- 50 dium steal-ate and 1% of an extreme pressure additive, such as Polane or tricresyl phosphite. Up to 30% of the ethyllactate sodium grease may be blended with a lithium soap mineral oil base grease, such as described above, to provide a sat-' 55 isfactory low temperature grease.

A low temperaturegrease can be produced by dissolving 6% of lithium stearate in 93% butyl oxalate and 1% of an extreme pressure additive, such as'Polane. Other dialkyl oxalates, such as the diethyl, diisobutyl, and diisoamyl, may be substituted for the dibutyl in making a satisfactory grease. Up to 30% of the dialkyl oxalate greases may be blended with a lithium soap mineral oil base grease, such as describedabove, tomake a satisfactory low temperature grease. A suitable low temperature blended grease may comprise from 5% to 30% of dibutyl oxalate, from 63% to 88% of a mineral lubricating oil, and 6%. of lithium stearate.

The methyl, ethyl, propyl, butyl, isoamyl and benzyl benzoates may act to dissolve soaps, such as lithium stearate, oleate or palmitate, and sodium stearate to produce satisfactory low temperature greases. When making the sodium base grease it is desirable to useapproximately 1% of aluminum stearate to produce a non-bleeding grease. Up to 30% of these alkyl benzoate greases may be blended with a lithium soap min- 5 eral 011 base grease of the type described above,

in producing a satisfactory. low temperature grease. A suitable low temperature blended grease may comprise from 5% to130% of butyl benzoate, from 3% to 15% of lithium stearate,

l0 and from 60% to 88% of a mineral lubricating oil.

When 90% of the mineral oil lithium grease is blended with 10% of the greases produced from the synthetic alkyl esters described above, the average reduction inviscosity ofthe mixture compared with the viscosity of the straight mineral oil base grease at 60 F. has been approximately 40%. When 80% of the mineral oil base grease is blended with of the grease produced from the synthetic alkyl organic esters as described a 20 above the viscosity of themixtureat -60 F. has

.been found to be approximately 75% less than the viscosity of the straight mineral oil basegrease. It will be seen, therefore, that by varying the percentage blend of straight mineral oil base grease with the grease produced from the syntheticalkyl organic esters that a grease of a predetermined and desired viscosity may be produced. Furthermore the blending of the alkyl ester base greases with the mineral oil base greases has a very substantial effect in changing the viscosity of the greaselfor low temperatureoperation and thus a relatively small amount of the relatively more expensive synthetic alkyl ester base grease, may be used in obtaining a grease low temperature blended grease made in accordance with the present invention may comprise from 60% to 88% of a mineral lubricating oil, from 3% to 15% of an alkali metal soap, and from 5% to 30% of an alkyl 40 ester selected from the alkyl acetyl ricinolates,

alkyl .lactates, alkylbenzoates, and dialkyl oxalates). The synthetic alkyl esters used in the production of greases, as described above, all have good 1 lubricating properties but it is found that by blending with them from .1 to 1% of an extreme 'pressureadditive, the load-carrying capacity of the ester lubricantsis greatly increased. The additives above referred to are commercial prodagent Polane mentioned above is chlormethyl stearate. The extreme pressure agentsdisclosed in Engelke Patent No. 2,260,303, sulfurized tricresyl phosphites may be used. These additives are preferably dissolved in the lubricants prior to the time that the lubricants areblended with soaps for the manufacture of grease.

It has been found that it is quite important in However, the esters may be blended directly with the mineral oil and the desired quantities of soap added, and the mixture heated to a temperature of about 380 F., then quickly cooled in thin layers to room temperature, and a very satisfactory grease obtained.

, A naphthenic base mineral oil is preferably used in making the lithium grease as described above. The naphthenic oil which is used in making low temperature greases preferably has a 76 viscosity of approximately at 100 F. A

ucts now on the market. The extreme pressure naphthenic base mineral oil grease made with lithium soap and about 1% of an aluminum soap. a lithium soap will dissolve in 'or be compatible 4. A low temperature blended grease compris with up to 30% or any oi'thegreases made from ing a blend of about 80% oi a mineral oil grease synthetic alkyl organic esters as described above. containing from about.a6% to about 96% of a The preferred form oi the'invention having mineral lubricating oil, from 4% to about 12% been thus described whatiscialmed as new is: of a lithium soap and from 0.5% to 3% 01 an 1. A low temperature grease comprising from aluminum soap, with approximately or an 63% to 88% of a mineral lubricating oil, from a ester grease containing approximately 93% of an' alkyl ester selected from the group consisting oi 1% oi analuminum soap.

5%, to of an alkyl acetyl rlcinoleate. approxi alkyl ester selected from the group consisting oi mately 6% 01 lithium stearate and approximately 10 alkyl acetyl ricinoleates. allryi lactates, alkyl 1% of aluminum stearate. i 1 benzoates and dialkyl oxalates; about 6% of a 2. a low temperature grease comprising butyi lithium soap and about 1% or analuminum soap. benzoate 5 to 30%, lithium stearate 3 to 15%, 5. Alow temperature blended grease comprisaluminum stearate 0.5 to 1%, mineral lubricating ing a blend of about to or 'a mineral oil 60 to 88%, and an extrem pressure additive is oil grease containing irom about 86% to about- 0.1 to 1.0%. 96% of a mineral lubricating. oil trom 4% to 3.. A low temperature blended grease comprlsabout 12% of a lithium soap and from 0.5% to ing a blend of about 90% of a mineral oil grease 3% of an aluminum soap. with approximately containing from about 86% to about 96% of a 30% to 10% of an ester grease containing apmineral lubricating oil, !rom 4% to about 12% 20 proximately 93% of an alkyl ester selected from of a lithium soap and from 0.5% to 3% of an the group consisting oi aikyl acetyl ricinoleates, aluminum soap, with approximately 10%, or an alkyl lactates. alkyl benmates. and dialkyl oxester grease containing approximately 93% of an alates, about 6% of a lithium soap and about alkyl acetyl ricinoleates, alhrl mums, alkyl so 1 x benzoates and dialkyi oxalates. about 6% oi a J N D- MO GA