Lubricating compositions

United States Patent Office „ 3,041,284 __ - Patented June 26, 1962 , 3,041,284

LUBRICATING COMPOSITIONS

George M. Calhoun, Berkeley, and Wfiliam A. Hewett, Oakland, Calif., assignors to Shell Oil Company, a corporation of Delaware

No Drawing. Filed Aug. 8, 1958, Ser. No. 753,882

Claims. (Cl. 252—48.6)

This invention relates to lubricants, particularly those useful for lubrication under severe operating conditions, such as those under extreme high speed and at high temperatures.

It is well known that the high pressure occurring in certain types of gears and bearings may cause rupture of lubricant films with consequent damage to the machinery It is known that various base lubricants can be improved in their protective properties for rubbing surfaces by the addition of certain substances, so-called extreme pressure agents, so that excessive wear, scuffing and seizure which normally follow a break in the film lubricant are minimized or prevented.

It is known that certain compounds of metal-reactive elements, such as certain compounds of chlorine, sulfur and phosphorus, as well as certain other compounds, such as some compounds of lead, impart extreme pressure properties to various lubricants. Notable among the substances heretofore used are the lead soaps, phosphoric acid esters, free or bound sulfur and certain chlorinated organic compounds. A principal objection to many of these extreme pressure agents is their generally high reactivity with the metallic surface, causing etching, corrosion and discoloration of the metal surface. Another objection to chemically reactive extreme pressure agents is that they alter the original chemical nature of the contacting surface, which under certain conditions is undesirable. Aflditionally, because of the activity of agents of this type, they usually, are depleted rapidly resulting in only a temporary solution to the problem of extreme pressure lubrication.

It has now been discovered that improved extreme pressure lubricants are provided by a suitable lubricating oil containing an oil-soluble thiaether containing at least two oxygen-containing radicals or groups and in which at least one of any such thiaether sulfur atom is separated from one of the polar groups by a chain of from 1 to 4 carbon atoms and from any other polar group by a chain of at least 7 carbon atoms. The thiaethers are mercapto modified ethylenically unsaturated higher aliphatic (cyclic or acylic) compounds containing oxygen-containing radical or polar group, wherein such polar group is either a terminal or an internal group and is an alcohol (—OH), ether .(—O—), acid (—COOH—) or ester (—COOC—) functional group. At least one thiaether sulfur is associated with one of the polar group in a radical represented by —S—(CH₂)_n—X where X is —OR' or —COOR', and the R’s being hydrogen or Q_₄ alkyl radical and n is an integer of from 1 to 4, preferably 1. The number of —S—(CH₂)_n—X units in the final compound depends on the degree of unsaturation of the unsaturated aliphatic polar compound and generally varies from 1 to 4, preferably from 1 to 2. Compounds of this type can be represented by the formula

Compounds of the type under discussion can be prepared by reacting a mercapto compound with an unsaturated acid or other equivalent compound. The mercapto compounds include the mercapto aliphatic carboxylic acids such as mercapto acetic acid, mercapto propionic acid, mercapto butyric, or mercapto-alkanols such as 2-mercaptoethanol, 2- and 3-mercaptopropanol, 2-, 3- and 4mercaptobutanol, or ethers of said mercaptoalcohols such as methyl or octyl 2-mercaptoethanyl or mercapto esters, e.g., ethyl mercapto acetate or ethyl mercaptobutylate, and mixtures thereof. The unsaturated long-chain polar containing compounds which are reacted with the mercapto compound may be a long-chain unsaturated fatty acid, e.g. oleic acid, linoleic acid, linolenic acid, erucic acid’ ricinoleic acid or an unsaturated fatty alcohol, e.g., oleyl alcohol, ncinoleyl alcohol, etc., or unsaturated esters in which either the fatty acid or alcohol can be unsaturated or where both the acid and alcohol portion of the ester are unsaturated, e.g., methyl oleate, ethyl oleate, oleyl stearate, oleyl undecenoate, lauryl oleate, glycerol trioleate, vinyl oleate, oleyl oleate, or the like.

The additives can be prepared by the methods described by Koenig et al. JACS 79, 362 (1957) or Fitzgerald Jr. Org Chem. 22, 197 (1957) and preferably at low temperatures, from room temperature to about 50° C. and in the presence of a free radical catalyst such as azo or peroxide catalysts or ultraviolet light and a non-reactive solvent such as benzene, toluene, xylene, or the like. Suitable initiators include various free radical-yielding, heterocyclic and alicyclic peroxides, such as diethyl peroxide, tertiary butyl hydroperoxide, dibenzoyl peroxide, ditertbutyl peroxide, dimethylthienyl peroxide, dicyclohexyl peroxide, dilauroyl peroxide and urea peroxide. These are mentioned by way of non-limiting examples of suit35 able organic peroxides. Other initiating compounds known include emulsion redox systems, such as a mixture of sodium bisulfite and persulfate, ammonium persulfate, alkali metal perborates, azo compounds, such as alpha,alpha-azodiisobutylronitrile, etc.

The following examples illustrate the preparation of suitable additives for use in accordance with the present invention. *

EXAMPLE I

About 600 grams of oleic acid and 223.5 grams of mercaptoacetic acid were mixed in a flask at 20-25° C. About 240 drops (30 drops at a time) of t-butyl hydroperoxide were added over a period of 2 hours and the temperature was kept at about 37° C. The reaction mix50 tore was diluted with 2 volume of diethyl ether, washed with 12 liters of water to pH 4, dried over Na₂SO₄, filtered and the solvent stripped at 155° C. and 2 mm. pressure. The final product was a mixture of 9- and 10-carboxymethylmercaptostearic acid and analyzed as follows:

Percent C

Percent H

Percent O

Percent S

Eq.

Wt.

Found.

Theory.

R- R

L J-[s-(CHj)_n-x]_n where R is an oil-solubilizing hydrocarbyl radical, preferably C₈_₃₀ alkyl radical, R'' is an alkyl radical, preferably of at least 7 carbon atoms, Y is an oxygen-containing radical such as alcohol, acid, ether or ester group, and in the case of the latter two an additional R radical is ⁷⁰present, X and n are the same as defined above.

64.2

64.2

10.2

10.2

17.0

17.1

8.74

8.56

183

187

EXAMPLE II

About 600 grams of ethyl oleate and 223.5 grams of mercaptoacetic acid were mixed in a flask at 20-25° C. About 240 (30 drops at a time) of Lbutyl hydroperoxide were added over a period of 2 hours and the temperature was kept at about 37° C. The reaction mixture was diluted with 2 volumes of diethyl ether, washed with 12 liters of water to pH 4, dried over Na₂SO₄, filtered and the solvent stripped at 155° C. and 2 mm. pressure. The

3,041,284 final product was a mixture of ethyl 9- and 10-carboxymethylmercaptostearate which analyzed as follows:

FoundTheory.

<td> Percent C</td><td> Percent H</td><td> Percent O</td><td> Percent S '</td>

<td> 65.7</td><td> 10.5</td><td> 16.0</td><td> 7.75</td>

<td> 65.6</td><td> 10.5</td><td> 15.9</td><td> 7.97</td>

472

402

Fq.

Wt.

EXAMPLE HI

About 600 grams of ricinoleic acid and 223.5 grams of mercaptoacetic acid were mixed in a flask at 20-25 ° C. About 240 drops (30 drops at a time) of t-butyl hydroperoxide were added over a period of 2 hours and the temperature was kept at about 27 ° C. The reaction mixture was diluted with 2 volumes of diethyl ether, washed with 12 liters of water to pH 4, dried over Na₂SO4, filtered anH the solvent stripped at 155° C. and 2 mm. pressure. The final product was a mixture of 9- and 10-carboxymethylmercapto-12-hydroxystearic acid with a determined equivalent weight of 207 (theory 195).

EXAMPLE IV

About 600 grams of glyceryl trioleate and 223.5 grams of mercaptoacetic acid were mixed in a flask at 20-25° C. About 240 drops (30 drops at a time) of t-butyl hydroperoxide were added over a period of 2 hours and the temperature was kept at about 37° C. The reaction mixture was diluted with 2 volumes of diethyl ether, washed with 12 liters of water to pH 4, dried over Na₂SO4, filtered and the solvent stripped at 155° C. and 2 mm. pressure. The final product was a mixture of glyceryl tris(9- and 10-carboxymethylmercaptostearate) with a determined equivalent weight of 445 (theory 387).

, EXAMPLE V

About 600 grams of oleyl alcohol and 223.5 grams of mercaptoacetic acid were mixed in a flask at 20-25° C. About 240 drops (30 drops at a time) of t-butyl hydroperoxide were added over a period of 2 hours and the temperature was kept at about 37 ° C. The reaction mixture was diluted with 2 volumes of diethyl ether, washed with 12 liters of water to pH 4, dried over Na₂SO4, filtered and the solvent stripped at 155° C. and 2 mm. pressure. The final product was a mixture of 9- and 10-carboxymethylmercaptostearyl alcohol.

EXAMPLE VI

About 600 grams of oleyl oleate and 223.5 grams of mercaptoacetic acid were mixed in a flask at 20-25° C. About 240 (30 drops at a time) of t-butyl hydroperoxide were added over a period of 2 hours and the temperature was kept at about 37° C. The reaction mixture was diluted with 2 volumes of diethyl ether, washed with 12 liters of water to pH 4, dried over Na₂SO₄, filtered and the solvent stripped at 155° C. and 2 mm. pressure. The final product was a mixture of 9- and 10-carboxymethylmercaptostearyl 9- and 10-carboxymethylmercaptostearate. The compound was completely oil soluble.

Following the above procedures the following additional compounds were prepared:

EXAMPLE VII

0-(9- and 10-[2-hydroxyethyJmercapto]-stearoyl)-5-hydroxyl-3-thiavaleric acid.

EXAMPLE VIII

9- and 10-(2-hydroxyethylmercapto)-3-thiaheneicosanoic acid.

EXAMPLE IX

5-hydroxy-3-thiamyl 9- and 10-carboxymethylmercaptostearate.

EXAMPLE X

9- and 10-carbomethylmercaptostearyl-(2-hydroxyethylmercapto)-undecenoate.

The cercapto-modified acids, alcohols, esters, etc., in general, are oil-soluble and can be used in amounts of from about 0.5% to about 20%, preferably from about 1% to about 5% by weight. With certain oils the mer5 capto-modified acids or alcohols form opaque solutions, but they can be rendered transparent by addition of a small amount (0.1-10%) of an oil-soluble branchedchain aliphatic monohydric alcohol, oil-soluble high molecular weight fatty acid or monoester of said fatty acid 10 and polyhydric alcohols. The alcohols, fatty acids or monoesters effectively clarify oils containing mercapto acids or alcohols as described without destroying the extreme pressure properties of such oil compositions. The mercapto-modified unsaturated esters as described in Ex15 ample VI form clear transparent oil compositions and generally do not require any clarifiers.

Oil-soluble alkanols which are particularly useful as clarifiers are the so-called “OXO” alcohols of 3 to 5 carbon atoms, and copolymers of mixtures of such alkenes, 20 by catalyzed reaction with carbon monoxide and hydrogen in accordance with the conditions of the “OXO” process, as is well known in the art. The composition of a typical C₈-OXO-alcohol mixture derived from a mixture of C₇-olefins, produced by polymerization of a typical 25 olefin refinery cracked gas fraction of C3-C4 hydrocarbons given in Table I.

TABLE I

Alcohol: Percent, wt.

3,5-dimethyl hexanol 29

4,5-dimethyl hexanol. 25

3,4-dimethyl hexanol 17

5-methyl heptanol; 3-methyl heptanol 16

5-ethyl hexanol—2.3

5,5-dimethyl hexanol 1.4

Alpha-alkyl alkanols—_4.3

Others-------— 5.0

Other suitable alkanols include 6-methyl-l-heptanol, 2-npropyl-l-pentanol, 3-n-propyl-l-hexanol, 2,2-dimethyl-l40 octanol, 10,10-dimethyl-l-undecanol, 3-isopropyl-l-heptanol and the mixtures thereof.

Fatty acids useful as clarifiers include the saturated and unsaturated oil-soluble fatty acids having from 10 to 30 carbon atoms such as capric, lauric, oleic, linoleic, ricino45 leic acids and mixtures thereof.

Monoesters derived from simple alkane polyols and long chain fatty acids which are useful as clarifiers include oil-soluble glycerol monooleate, glycerol monostearate, glycerol monoricinoleate, pentaerythritol mono- and di50 laurate, pentaerythritol mono- and dioleate, pentaerythntol mono- and distearate, mono-, di-, and tri- ethylene glycol monoleate, propylene glycol monoricinoleate, triethylene glycol monostearate, sorbitol monolaurate, mannitol monooleate, mannitol dioleate, sorbitol dioleate, etc. 55 Lubricating oils useful for the preparation of compositions of this invention can be one or more of a variety of synthetic oils or natural hydrocarbon oils having a viscosity range of from 50 SUS at 100° F. to 250 SUS at 210° (SAE viscosity number ranging from SAE 5 to SAE 60 90). The natural hydrocarbon oils can be obtained from paraffinic naphthenic, asphaltic or mixed base crudes, and/or mixtures thereof. Synthetic oils include polymerized olefins, alkylated aromatics, isomerized waxes, copolymers of alkylene glycols and alkylene oxide (Ucon 65 fluids) which are described in U.S. Patents 2,425,755, 2,425,845 and 2,774,733 such as Ucon 50HB170, Ucon 50HB660 or Ucon LB550X and which are copolymers of ethylene and 1,2-propylene oxides, the mono- and diols, as well as their ether derivatives; organic esters of ali70 phatic dibasic acids such as di-2-ethylhexyl sebacate or di-2-ethylhexyl adipate and the like. The hydrocarbon oils may be blended with fixed oils such as castor oil, lard oil and the like and/or synthetic oils as mentioned or silicone polymers and the like. Typical oils of this 75 type include petroleum motor oils which are (A) paraf3,041,284 firuc in character and (B) naphthenic in character having the following properties:

<td></td><td colspan="2"> (A) (SAE 10W)</td><td> (B) (SAE 30) ₅</td>

<td> Pour point, °F____</td><td colspan="2" rowspan="4"> -10 390 44 eo</td><td rowspan="4"> -5 415 58 60</td>

<td> Flash, ° F_____</td>

<td> Viscosity, SUS at 210° F__________ Viscosity Index____</td>

<td></td>

<td colspan="4"> Other suitable oils are the gas turbine lube oils having the following properties:</td>

<td colspan="2"> Grade</td><td> 1010</td><td> 1065</td>

<td colspan="2"> Flash, COC, ° F</td><td rowspan="6"> 300 -10 59.4 0.02 None</td><td rowspan="6"> 15 465 0 . 530 0.01 None</td>

<td colspan="2"> Pour, °F_______</td>

<td colspan="2"> Viscosity, SUS at 100° F...</td>

<td colspan="2"> Neutral Number________</td>

<td colspan="2"> Ash__________</td>

<td colspan="2"></td>

<td colspan="4">^--------- 20 The following compositions are illustrative of the invention, the percentages being by weight:</td>

Composition A

Example I additive________________________2%.

1010 Mineral oil--------------------------Balance ^2o

Composition B

Example I additive_________________________2%.

Glycerol monoleate________________________2%.

1010 Mineral oil---------------------------Balance ³⁰

Composition C

Example III additive______________________2%.

Glycerol monoleate________________________8%.

1010 Mineral oil__________________________Balance.

Composition D

Example IV additive 2%.

Glycerol monooleate5%.

1010 Mineral oil__________________________Balance.

Composition E

Example II additive2%.

1010 Mineral oil---------------------------Balance.

Composition F

Example V additive2%.

C₁₃H₂₇OH (made by “OXO” process)3.5%.

1010 Mineral oil--------------------------Balance.

Composition G

Example I additive2%.

Lauric acid 2%.

SAE 90 Mineral oil_______________________Balance.

Composition H55

Example I additive2%.

C₁₃H₂₇OH (made by “OXO” process)________2.74%.

SAE 90 Mineral oil________________________Balance.

Composition 160

Example I additive5%.

Ucon 50HB660 (polyethyle.ne-propylene glycol having a SUS at 100° F. of 660)____Balance.

Composition J05

Example I additive2%.

Di-2-ethylhexyl sebacate___________________ Balance.,

Composition K

Example VI additive_______________________2%.70

1010 Mineral lubricating oil________________ Balance.

Composition L

Example VI additive_______________________5%.

Ucon 50HB660 fluid_______________________Balance. 75

Composition M

Example VI additive____________________ 2 5%

Mineral lubricating oil (SAE 90)_____Balance.

Composition O

Example X_______________________________₂%

Ci₃H₂₇OH (made by “OXO” process)___ 2 5%

1010 Mineral oil----------------------Balance.

Composition P

Example IX________________________ ₂%

1010 Mineral oil-------------ill·Balance.

Composition Q

Example VII________________________ _ ₂ 5%

1010 Mineral oil------------Balance.

Compositions of this invention were evaluated for their extreme pressure properties on a Spur-Gear machine. The machine consists essentially of two geometrically similar pairs of gears connected by two parallel shafts. The gear pairs are placed in separate gear boxes, which also contain the supporting ball bearings. One of the shafts consists of two sections connected by a coupling. Loading is accomplished by locking one side of the coupling and applying torque to the other. The conditions of the test were:

Speed—3200 and 10,000 r.p.m.

Oil temperature—38° C. and 160° C.

Oil flow-rate—10 cc./scc.

Load in increments 5 min. at each setting

Results of the evaluations are given in Table I. For purpose of comparison, the results obtained from the use of the base oil alone and with other dicarboxylic acids are also given in Table II.

TABLE II

Composition:

A_____________

B__________

C______________

D________

E__________

F__________

K______________________

0___________

P________

Q----------------______

1010 Mineral oil-j-2% alkenyl succinic acid___

1010 Mineral oil-f-2% malonic acid__________

1010 Mineral oil-f-2% 3hexadecyl adipic acid__

1010 Mineral oil-J-2% thiodiglycolic acid_____

1010 Mineral oil+2% thio-alpha,alpha'bis - (stearic acid)_____

1010 Mineral oil+2% dodecyl-mercapto succinic acid_____________

1010 Mineral oil+2% heptylmercapto succinic acid_______________

1010 Mineral oil+2% alpha - mercapto - benzoic (acid_____________

1010 Mineral oil+10% glycerol monooleate____

1010 Mineral oil+13.25% lauric acid____________

Score Load, lbs./in. 12,700 (3200 r.p.m.). 9,900 (10,000 r.p.m.). 9,900 (10,000 r.p.m.). 9,900 (10,000 r.p.m.). 7,800 (3,200 r.p.m.). 12,000 (3,200 r.p.m.). 7,800 (3,200 r.p.m.

at 160° C.). 9,200 (10,000 r.p.m.). 8,500 (10,000 r.p.m.). 7,100 (10,000 r.p.m.).

1,400 (3,200 r.p.m.).

2,800 (3,200 r.p.m.).

1,400 (3,200 r.p.m.).

5,000 (3,200 r.p.m.).

3,500 (3,200 r.p.m.).

1,400 (10,000 r.p.m.).

4,200 (3,200 r.p.m.).

4,200 (3,200 r.p.m.).

1,800 (3,200 r.p.m.).

3,400 (3,200 r.p.m.).

3,041,284 . W;

1010 Mineral oil-j-2%

C₁₃H₂₇OH (“OXO” process)___________-__- 600 (3,200 r.p.m.).

1010 Mineral oil-------- 600 (3,200 r.p.m.).

The data show the outstanding enhancement of the load-carrying ability of the oil effected by the mercaptocontaining acids of the invention, as represented by those of Compositions A through F, K, Ο, P and Q. On the other hand, malonic acid, succinic acid, 3-hexadecyl adipic acid and C₁₆-alkenyl succinic acid as well as sulfur-containing acids outside the scope used by applicants such as thiodiglycolic acid, thio-alpha,alpha'-bis(stearic acid), dodecyl-mercapto-succinic acid, heptylmercapto-succinic acid alpha-mercaptobenzoic acid, glycerol-monooleate, lauric acid or “OXO” alcohol effected only a slight improvement.

Compositions of the present invention were also tested for their corrosion and sludge resistant properties by the following methods: (1) a Timken 2126 steel bearing was immersed in a test composition and placed in an open air oven at 150° C. for 65 hours, and at the end of,the test, the bearing examined and (2) steel rods (3/16 by 3) were immersed in test compositions for 21½ hours at 150° C. and the amount of sludge formed on the rods 25 ester., was noted as shown in Table III.

formula

-Χ-[3-(ΟΗ₂),-Χ]2 wherein R is an oil-solubilizing alkyl radical of 8—30 carbon atoms, R is an alkyl radical of at least 7-10 carbon atoms, Y is an ester radical, and X is an oxy gen-containing radical selected from the group consisting of —OH and —COOH, n is an integer of from 1 to 4 and one —S—(CH₂)_nX group being separated from Y by a carbon chain of from 7 to 10 carbon atoms.

2. A mineral lubricating oil composition comprising a major amount of mineral lubricating oil and from about 1% to about 5% of a di (carboxy C_r_₄ alkyl mercapto) substituted long-chain fatty acid ester, one of said carboxy C_x_₄ alkyl mercapto, radicals being from 7 to 10 carbon atoms away from the carboxyl radical of the ester.,

3. A mineral lubricating oil composition comprising a 20 major amount of mineral lubricating oil and from about 1% to about 5% of a di(hydroxy Ci_₄ alkyl mercapto) substituted long-chain fatty acid ester, one of said hydroxy Ci_₄ alkyl mercapto radicals being from 7 to 10 carbon atoms away from the carboxyl radical of the

4. The lubricating oil composition of claim 1 containing from about 0.1% to about 10% of glycerol monooleate.

R— R

Composition table hi

Composition K---------------1010 Mineral oil +2% 3(-2-ethylhexyl) adipic acid.

1010 Mineral oil +2% 9- and 10-carboxystearic acid.

5. The lubricating oil composition of claim 1 containing from about 0.1% to about 10% of lauric acid.

6. The lubricating oil composition of claim 1 containing from about 0.1% to about 10% of an oil-soluble branched-chain Oxo alcohol.

7. The lubricating oil composition of claim 2 containing from about 0.1% to about 10% of glycerol monooleate.

8. The lubricating oil composition of claim 3 containing from about 0.1% to about 10% of an oil-soluble branched-chain Oxo alcohol.

no stain_______ badly stained.

0.7 mg. sludge.

mg. sludge.

100 mg. sludge.

The sulfur-containing compounds of this invention are useful also for providing superior load-carrying properties for lubricating oils which contain minor amounts of other agents which are non-reactive with the dicarboxylic 40 acids, such as silicone anti-foaming, agents, alkylphenol anti-oxidants, polyacrylate ester viscosity-index improvers, and the like.

This application, is a continuation-in-part of our copending patent application Serial No. 699,919, filed Decern- 45 ber 2, 1957, and which has matured as U.S. Patent 2,994,662 on. August 1, 1961.