US3505223A - Lubricant compositions - Google Patents

Description

United States Patent 3,505,223 LUBRICANT COMPOSITIONS Leonard M. Niebylski, Birmingham, Mich., assignor to Ethyl Corporation, New York, N.Y., a corporation of Virginia No Drawing. Filed Mar. 30, 1967, Ser. No. 626,963 Int. Cl. Cm 1/10, 1/38, 7/02 US. Cl. 252- 11 Claims ABSTRACT OF THE DISCLOSURE The extreme pressure wear properties of base lubricants including water, hydrocarbons, polyesters, silicones, polyethers and halocarbons is enhanced by the addition of a metal thiosulfate, especially lead thiosulfate, to the base lubricant.

Background This invention relates to improved lubricant compositions. Many lubricants which are satisfactory for ordinary lubricating applications do not provide adequate protection under the extreme conditions of high load. These high load conditions are encountered in such applications as cutting oils and bearing lubrication. Present lubricants made for these purposes include sulfurized and chlorinated hydrocarbon oils and oils containing such additives as iodine or molybdenum sulfide.

Summary An object of this invention is to provide an extreme pressure wear additive for a variety of lubricating base oils. This additive greatly increases the lubricity of these base oils under conditions of extremely high load. This and other objects are accomplished by providing a lubricating composition comprising a base lubricant and an extreme pressure wear reducing amount of a metal thiosulfate.

The amount of metal thiosulfate can vary over a wide range depending upon the base lubricant employed and the specific application for which the lubricant is designed. Generally good results are obtained when from about 0.01 to weight percent of metal thiosulfate is added. A more useful range is from about 0.1 to 25 weight percent, and a most useful range is from about 0.5 to 20 weight percent of metal thiosulfate. The metal thiosulfate is not necessarily soluble in the base lubricant and can be merely slurried into the base as a fine powder or reduced to a colloid form by the use of a colloid mill. Suitable metals include any of the metals capable of forming metal thiosulfate salts. Some examples are lithium, sodium, potassium, manganese, calcium, barium, strontium, titanium, zirconium, cadmium, zinc, nickel, cobalt, copper, iron, magnesium, lead, tin, silver, germanium, and the like, as well as mixtures of the above. When water is the base lubricant it is often desirable to use a mixture of an alkali metal thiosulfate with a normally insoluble metal thiosulfate such as lead thiosulfate because they tend to form a complex which solubilizes the normally insoluble metal thiosulfate.

Another useful class of metal thiosulfates is represented by the metal salts of Bunte acids. These compounds have the formula:

wherein R represents a hydrocarbon radical containing from 1 to about 30 carbon atoms, M is a metal including those previously listed, and n is the valence of M. The radical R can also be substituted with non-hydrocarbon "ice groups such as chloro, bromo, iodo, nitro, hydroxyl, carboxyl, carbonyl, and the like. Some representative examples of these Bunte salts are:

sodium lauryl thiosulfate potassium benzyl thiosulfate lead cetyl thiosulfate calcium eicosyl thiosulfate zinc triacontylthiosulfate magnesium methyl thiosulate barium isoamyl thiosulfate lead p-chlorophenyl thiosulfate copper p-nitrobenzyl thiosulfate silver p-hydroxyphenyl thiosulfate sodium 3,5-di-tert-butyl-4-hydroxybenzyl thiosulfate lead cyclohexyl thiosulfate.

The above compounds are readily made by the reaction of a mercaptan with sulfur trioxide, yielding a Bunte acid, which in turn is converted to a metal salt.

The preferred metal thiosulfates are the alkali metal thiosulfates, silver thiosulfate and lead thiosulfate. The most preferred metal thiosulfate is lead thiosulfate.

Suitable base lubricants include hydrocarbon-derived lubricating oils and greases, polyester lubricants, silicone oils, polyethylene oils, and halohydrocarbons.

Hydrocarbon oils include those of a wide viscosity range of from about SAE-S to SAE-SO. These oils can be prepared using any of the well-known refining methods such as solvent refining. When the oils are to be used as cutting oils, it is preferred that they have a viscosity of about SUS at 100 F. In this use, they are often used in the form of water emulsion. Typical hydrocarbon oil formulations of this invention are represented by the following examples, in which all percentages are by weight.

EXAMPLE 1 To a Pennsylvania neutral mineral oil having a viscosity of 185 SUS at 100 F. is added 0.1 percent of lead thiosulfate.

EXAMPLE 2 To a mid-continent, solvent-refined neutral mineral oil having a viscosity of 290 SUS at 100 F. is added 3 percent of sodium thiosulfate.

EXAMPLE 3 To a California neutral mineral oil having a viscosity of 382 SUS at 100 F. is added 5 percent of potassium thiosulfate.

EXAMPLE 4 In a solvent-refined paraflinic mineral oil having a viscosity of SUS at 100 F. is slurried 20 percent of a silver thiosulfate powder.

EXAMPLE 5 To a solvent-extracted Pennsylvania bright stock having a viscosity of 500 SUS at 100 F. is added 7 percent of lead lauryl thiosulfate Bunte salt.

EXAMPLE 6 To a polybutene oil having a viscosity of 114 SUS at 100 F. is added 0.5 percent of a finely-divided lead thiosulfate.

EXAMPLE 7 To a polymerized trimethylene having a viscosity of 367 SUS at 100 F. is added 3 percent of lead eicosyl thiosulfate Bunte salt.

The metal thiosulfate additives are useful in a wide range of hydrocarbon-derived greases containing various metal soaps as thickening agents such as calcium stearate, lead oleate or sodium oleate. The following examples Will serve to illustrate the use of metal thiosulfates as extreme pressure wear reducing agents in some hydrocarbon-derived greases.

EXAMPLE 8 To a calcium oleate thickened grease containing about 82 percent of a hydrocarbon oil having a Saybolt viscosity at 100 F. of 300 is added percent of lead thiosulfate.

EXAMPLE 9 To a lead oleate thickened grease containing about 94 percent of a Pennsylvania mineral oil having a Saybolt viscosity at 100 F. of 200 is added 3 percent of sodium thiosulfate.

EXAMPLE 10 To a calcium stearate thickened grease containing about 87 percent of a California mineral oil having a Saybolt viscosity at 100 F. of 241 is added percent of silver thiosulfate.

EXAMPLE 11 To a grease containing 88 percent of a California mineral oil having a Saybolt viscosity at 100 F. of 300 and thickened with a mixture of calcium stearate and calcium oleate is added 15 percent of calcium lauryl thiosulfate Bunte salt.

The polyester lubricant base materials used in formulating the lubricant compositions of my invention may be either oils or greases. The oils may be formed by the reaction of a polycarboxylic acid with a mono-hydric alcohol, the reaction of a polyhydric alcohol with a mono-carboxylic acid, reaction between a polyhydric alcohol and a polycarboxylic acid, or combinations of the above reactions such as, for example, reaction of a dicarboxylic acid with a glycol and a mono-hydric alcohol, reaction of a glycol with a dicarboxylic acid and a monocarboxylic acid, or the reaction of a glycol, a mono-hydric alcohol, a dicarboxylic acid and a mono-carboxylic acid. The acids may be mono-carboxylic aliphatic acids such as, for example, propionic acid, valeric acid, Z-ethyl enanthic acid, 2,2 dipropyl butyric acid or 3 (Z-methylhexyl) valeric acid. They may contain unsaturated linkages, such as, for example, in senecioic acid, sorbic acid, or angelic acid; they may be polycarboxylic aliphatic acids such as succinic acid, glutaric acid, azelaic acid, 5-octene-1,8-di carboxylic acid, or 3-hexene-2,3,4-tricarboxylic acid, and they may be aromatic or cycloaliphatic acids, such as cyclohexaneacetic acid, 1,4 cyclopentylenebis acetic acid, phthalic acid, hemimellitic acid, and terephthalic acid.

The alcohols used in preparing the polyester lubricant base materials may be aliphatic mono-hydric alcohols such as propanol, Z-ethyl 3 hexanol, 2-ethyl-4-propy1 heptanol, Z-butanol, or Z-methyl propanol. They may be polyhydric aliphatic alcohols such as, 1,6-hexamethylene glycol, 1,10-decamethylene glycol, 2-hexene-1,6-diol, and 1,6-heptylene glycol, and they may be monoor polyhydric alicyclic or aromatic alcohols, such as 4-[m-(2-hydroxyethyl)phenyl]butanol, 3 (Z-hydroxyethyl)cyclohexanebutanol, p-(hydroxymethyl)phenethyl alcohol, cit-methylp-xylene-a,u'-diol, 1,4 cyclohexane-fi,/3'-diethyldimethanol, 2,3-bis(4-hydroxybutyl)-benzyl alcohol, 4,4-[3(3- hydroxyhexyl)-o-phenylene]dibutanol, and S [3-(3-hydroxypropyl)cyclopenta 2,4 dienylene13-ethyl amyl alcohol.

The polyester base greases used in formulating lubricant compositions of the invention are formed by admixing a soap with a diester oil. Such soaps may be derived from animal or vegetable fats or fatty acids, Wool grease; rosin, or petroleum acids. Typical examples of such soaps are lead oleate, lithium stearate, aluminum tristearate, calcium glycerides, sodium oleate, and the like. In addition, the diester greases may contain unreacted fat, fatty acids, and alkali; unsaponifiable matter including glycerol and fatty alcohols; rosin or wool grease; water; and certain additives which may function as modifiers or peptizers.

The preferred diester lubricant materials used in formulating the preferred lubricant compositions have the following generic formula:

COORi wherein R is divalent aliphatic hydrocarbon radical which may be saturated or unsaturated and has from 2 to 10 carbon atoms and -R and R are branched chain alkyl groups having from about 4 to 20 carbon atoms.

As shown by the above generic formula, the diesters utilized in formulating the preferred lubricant compositions include esters of succinic, glutaric, adipic, pimelic, suberic, azelaic and sebacic acid. Typical examples of such esters are diisooctyl azelate, di(Z-ethylhexyl) sebacate, disec-amyl sebacate, diisooctyl adipate, di(2 ethylhexyl)- adipate, di(Z-ethylhexyl) azelate, di( 1 methyl-4-ethyloctyl)glutarate, di-isoamyl adipate, di(2 ethylhexyl)- glutarate, di(Z-ethylbutyl)adipate, di-tetradecyl sebacate and di(Z-ethylhexyl) pinate.

The more preferred diesters are prepared by esterifying one mole of a dicarboxylic acid having the general formula: HOOC(CH COOH, where x is an integer of from 2 to '8, with 2 moles of a branched chain alcohol containing from about 4 to about 16 carbon atoms. Typical of the reactions embraced herein are the reactions of succinic, glutaric, adipic, pimelic, suberic or azelaic acid with sec-amyl alcohol, 3-methyl butanol, 2 ethyl hexanol or the branched chain secondary alcohols undecanol or tetradecanol.

The preferred diester lubricant fluids have molecular Weights ranging from about 300 to about 600-and freezing and pouring points from about -40 to less than about F. The flash and fire points range from about 300 F. to about 500 F. and their spontaneous ignition temperatures range from about 100 to about 800 F. The diesters made by reacting a dicarboxylic acid with a branched chain alcohol have been found to have superior viscometric properties as compared with diesters made by reacting dihydric alcohols with mono-carboxylic acids, and thus, diesters prepared by the former method are preferred in formulating the lubricant compositions of my invention.

In formulating the polyester grease compositions Within the scope of my invention, I have found that the greases prepared by admixing a lithium soap with the polyester oils have superior oxidative stability as compared with greases formulated with other soaps, such as, for example, the sodium, calcium or lead soaps. Thus, the polyester greases employing a lithium soap constitute a preferred embodiment of lubricant compositions within the scope of my invention.

To further illustrate the lubricant compositions of my invention, the following examples show typical ester lubricant compositions within the scope of the present invention. Unless otherwise specified, the percent composi tion given in these examples is on a weight basis.

EXAMPLE 12 To diisooctyl adipate having a viscosity of 35.4 SUS at 210 F. is added 10 percent of calcium thiosulfate.

EXAMPLE 13 To di(1-methyl-4-ethyloctyl)glutarate is added 0.1 percent of lead thiosulfate.

EXAMPLE 14 To di(2-ethylhexyl)adipate is added 25 percent of an equal mole mixture of cuprous thiosulfate and sodium thiosulfate.

EXAMPLE 15 To diethylphthalate is added 3 percent of lead thiosulfate and 2 percent of silver thiosulfate.

EXAMPLE 16 To di-sec-amyl sebacate having a viscosity of 34.2 SUS at 210 F. is added percent of lead cetyl thiosulfate Bunte salt.

EXAMPLE 17 To di(2-ethylhexyl)sebacate having a viscosity of 37.4 SUS at 210 F. is added 7 percent of lead thiosulfate.

The term silicone as used in this specification refers to a group of synthetic compounds containing silicon and organic groups. Silicone oils are well known to have a high degree of thermal stability and can be used at very high temperatures. Their viscosity index is high and the silicone oils and greases change relatively little in flow properties over a wide temperature range. In spite of these desirable characteristics, however, the widespread adoption of silicone oils has been hampered because they have relatively poor lubricity as compared with conventional hydrocarbon oils. The present invention alleviates this problem, especially under extreme pressure conditions. It is, therefore, an object of this invention to provide silicone lubricants, both greases and oils, with improved lubricity. The silicone oils and greases serving as the base lubricant in this embodiment of the invention include the polysiloxane oils and greases of the type polyalkyl, polyaryl-, polyalkoxy-, and polyaryloxy-, such as polydimethylsiloxane, polymethphenylsiloxane, and polymethoxyphenoxysiloxane. Also included are silicate ester oils such as tetraalkyloxy and tetraaryloxy silanes of the tetra-Z-ethylhexyl and tetra-p-tertbutylphenyl types and the silanes. Also included are the halogen-substituted siloxanes such as the chlorophenylpolysiloxanes. The polyalkyl-, polyaryland polyalkylpolyarylsiloxanes are the preferred types of silicone base lubricants. The following examples illustrate typical silicon base lubricants containing the metal thiosulfate additives. The percentages given are on a Weight basis.

EXAMPLE 18 To Dow-Corning 200 silicon fluid (a dimethylpolysiloxane) having a viscosity of 100 centistokes at 25 C., an open cup flash point of 575 F., a pour point of 67 F., and a specific gravity of 0.97 at 77 F. is added 5 percent of a finely-ground lead thiosulfate.

EXAMPLE 19 To some Dow-Corning 710 silicon fluid (a phenylmethylpolysiloxane of high phenyl content) having a viscosity of 475-525 centistokes at 25 C. and an open cup flash point of 575 F. is added 0.1 percent of sodium thiosulfate powder.

EXAMPLE 20 To Dow-Corning 44 silicon grease (a polymethyl-polyphenylsiloxane grease of medium consistency having a serviceable temperature range of from 30 to 400 F.) is added 25 percent of nickel thiosulfate.

EXAMPLE 21 To Dow-Corning 550 silicon oil (a phenylmethylpolysiloxane having a viscosity of 100150 centistokes at 25 C.) is added 5 percent of a finely-divided iron thiosulfate powder.

EXAMPLE 22 To monoethyldiethoxy monoacetoxysilane liquid having a boiling point of 191.5 C. is added 10 percent of lead thiosulfate.

EXAMPLE 23 To tribenzyl-n-hexadecylsilane liquid having a boiling point of 245-248 C. is added 20 percent of barium thiosulfate.

EXAMPLE 24 To a polyphenylpolymethylsiloxane (Dow-Corning F- 60 fluid having a viscosity of 71 centistokes at 25 C.) is

6 added 15 parts of a finely-divided silver thiosulfate powder.

The synthetic polyether base lubricants are generally polyalkylene oxide derivatives of aliphatic alcohols or phenols. They are frequently referred to as polyalkylene glycol oils and greases. The alkylene oxides most frequently used in their preparation are ethylene and propylene oxide. Also included within this group are the reaction products formed from higher polyalkylene oxides, polyglycidyl ethers and polythioglycols. Many of these substances are manufactured and marketed under the tradename Ucon. They are useful lubricants because of their high viscosity index and low viscosity in sub-zero temperature ranges. They generally have viscosities of from about 1351200 SUS at F. Tetrahydrofuran polymer oils and greases are formed by the copolymerization of tetrahydrofuran and an alkylene oxide such as ethylene oxide. These are also included within the polyether lubricant bases. The following examples will serve to illustrate this embodiment of the invention.

EXAMPLE 25 To a polyalkylene oxide oil derived from the reaction of lauryl alcohol with ethylene oxide and having a molecular weight of about 2000 is added 5 percent of lead thiosulfate.

EXAMPLE 26- To a polyether lubricant base formed by the reaction of p-isooctylphenol with propylene oxide and having an average molecular Weight of about 2500 is added 0.1 percent sodium thiosulfate.

EXAMPLE 27 To a tetrahydrofuran ethylene oxide copolymer oil having a viscosity of 83 SUS at 210 F. is added 25 percent of magnesium thiosulfate powder.

Another useful base lubricant is water. Although not as effective as many other base lubricants, it finds use in applications such as cutting lubricants because of its loW cost. Especially useful metal thiosulfates in water are the water-soluble metal thiosulfates such as those derived from alkali metals, calcium, strontium, magnesium, cadmium, zinc, nickel, cobalt, iron and manganese. Another useful class is a mixture of an alkali metal thiosulfate with a normally insoluble metal thiosulfate such as lead, mercury or copper thiosulfate. A complex forms which serves to solubilize the normally insoluble thiosulfate. From the foregonig, it is not meant to imply that the metal thiosulfates must be soluble in the base lubricant because they are very useful even When only suspended in the base lubricant.

Frequently in cutting oil applications water is used in combination with a second base lubricant in the form of an emulsion. The present thiosulfate additives are very useful in these water emulsions. The water emulsion may be made using a hydrocarbon oil or a modified oil such as a sulfurized oil. The additives are also useful in animal fats such as sperm oil and in complex base lubricants made by mixing different base lubricants such as mixtures of glycerides, paratfins, terpenes, and the like, including water emulsions of these materials.

Another useful class of base lubricants is the halocarbons. These are compounds containing carbon and halogens such as chlorinated hydrocarbons. The preferred halocarbons are those that contain fluorine. Such compounds are linear polymers built up from a recurring unit such as:

in which at least one X is fluorine and the other Xs can be chlorine, fluorine or hydrogen. Thus, these fiuorocarbons can be polytetrafluoroethylene, polymonochlorodifluoroethylene, polymonochloromonofluorethylene, and the like.

7 The following example illustrates the use of a metal thiosulfate in a halocarbon formulation.

EXAMPLE 28 To a polymonochloromonofluoroethylene is added 5 percent of lead as lead thiosulfate.

Tests have been conducted to demonstrate the extreme pressure wear reducing properties of metal thiosulfates in base lubricants. These tests were conducted using an Extreme Pressure Lubricant Tester (EP Tester), described by Boerlage in Engineering, vol. 136, July 14, 1933, pp. 467. This test machine employs 4 balls arranged in a tetrahedron. The bottom 3 balls are firmly held in a non-rotatable fixture such that the balls "are in abutting relation to each other. Their centers form the apices of an equilateral triangle. The top ball is aflixed to a rotatable spindle whose axis is positioned perpendicularly to the plane of the non-rotatable balls in a line with the center point of the triangle formed by the apices of the 3 bottom balls.

In operation, the 4 balls are immersed in the lubricant composition to be tested and the fixture holding the 3 bottom balls is moved upwardly forcing the 3 fixed balls against the upper rotating ball. The severity of the test can be changed by merely forcing the lower fixture upward under difi'erent pressures. When the pressure reaches the point that the lubricant fails, the heat generated by the friction between the rotating ball and the fixed balls is such that the balls weld together. In this test, the presently-known extreme pressure lubricants such as those centaining sulfurized sperm oil will weld at loads in the range of from 200 to 450 kg. The following table shows the results obtained when lead thiosulfate was added in different concentrations to a base hydrocarbon lubricant, Amoco No. 31.

Conc. (wt. percent): Max. load (kg) 100 1 450 5 800 This is the limit of the EP Tester and represents a metal contact pressure of about 1,000,000 pounds per square inch.

The above EP Test was conducted employing sodium thiosulfate as the extreme pressure additive. The following results are from that test.

Conc. (wt. percent): Max. load (kg) 0 100 2.5 450 5.0 500 From the foregoing tests, it is seen that the addition of metal thiosulfates to a base lubricant greatly increases its extreme pressure lubricating properties and results in a lubricant having better lubrication properties under high load than those previously available.

I claim:

1. A lubricating composition comprising a major amount of an organic liquid lubricating oil or grease and an extreme pressure reducing amount of a metal thiosulf-ate selected from the group consisting of lead thiosulfate and metal salts of Bunte acids having the formula:

wherein R is a hydrocarbon radical containing from 1 to about 30 carbon atoms, M is a metal and n is the valence of M.

2. The lubricating composition of claim 1 wherein said metal thiosulfate is lead thiosulfate.

3. The composition of claim 2 wherein said lead thiosulfate is present in an amount of from about 0.01 to 20 weight percent, based on the weight of said lubricating composition.

4. The composition of claim 3 wherein said base lubricant is a hydrocarbon lubricating oil.

5. The composition of claim 3 wherein said base lubricant is a diester lubricant.

6. The composition of claim 5 wherein said diester lubricant is selected from the group consisting of alkyl esters of sebacic acid and adipic acid.

7. The composition of claim 3 wherein said base lubricant is a silicone lubricant.

8. The composition of claim 3 wherein said base lubricant is a synthetic polyether lubricant.

9. The composition of claim 3 wherein said base lubricant is a halocarbon wherein the halogen is selected from the group consisting of chlorine and fluorine.

10. The composition of claim 1 wherein said metal thiosulfate is a metal salt of a Bunte acid having the wherein R is a hydrocarbon radical containing from 1 to about 30 carbon atoms, M is a metal and n is the valence of M.

11. The composition of claim 10 wherein M is lead.

References Cited UNITED STATES PATENTS 1,822,449 9/1931 Nonamaker 252-49 X 2,121,825 6/1938 Prutton 252--58 2,479,583 8/1949 McHan 252-397 2,288,288 6/1942 Lincoln 25246.4 X 2,330,239 9/1943 PruttOn 25233 X 2,805,265 9/1957 Heiberger 260-651 3,377,279 4/1968 Sibert 25225 X 3,301,782 1/1967 Knowles 252---49.7 X

5 DANIEL E. WYMAN, Primary Examiner W. CANNON, Assistant Examiner US. or. X.R.

Patent NO- Dated April 7: 97

Inventr fl Leonard M. Niebylski It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, lines G t-67, the formula reading:

0 if ll should E S f 0 Mn read [3 1 M Column 2, line 65, "trimethylene" should read trimethylethylene GihiiUf .9

SEALED me 2 51970 (SEAL) Attest:

mm x. JR- Edward Oomissiom of Patents Attesting Offim