Lubricant compositions

Abstract

Lubricant compositions comprising a novel additive combination to improve the anti-oxidant and rust-inhibiting properties of these compositions are disclosed. The additive combination comprises an alkylene dithiocarbamate and an aliphatic hydrocarbon-substituted succinic acid or certain derivatives thereof. Lubricant compositions containing the novel additive combination are useful in a variety of applications.

Description

The invention herein is concerned with lubricating compositions comprising a novel combination of additives to improve both the anit-oxidant and rust-inhibiting properties of these compositions.

More specifically, the subject lubricating compositions comprise a major proportion of a lubricating oil, and a minor proportion, sufficient to improve the anti-oxidant and rust-inhibiting properties of the composition, of an additive combination. This additive combination comprises (A) one or more anti-oxidants based upon alkylene dithiocarbamates and (B) one or more rust inhibitors based upon hydrocarbon-substituted succinic acids or certain derivatives thereof.

The additive combination of the present invention is effectively employed in the lubricating compositions designed for a variety of uses. Likewise, the combination is effective in compositions based upon both natural and synthetic oils of lubricating viscosity. Also, the subject additive combination is effective in lubricating compositions containing additional additives.

The subject additive combination can be effectively employed in a variety of lubricating compositions formulated for a variety of uses. Thus, lubricating compositions containing the subject additive combination are effective as crankcase lubricating oils for spark-ignited and compression-ignited internal combustion engines, including automobile and truck engines, two-cycle engine lubricants, aviation piston engines, marine and low-load diesel engines, and the like. Also, automatic transmission fluids, transaxle lubricants, gear lubricants, metal-working lubricants, hydraulic fluids, and other lubricating oil and grease compositions can benefit from the incorporation of the present additive combination therein.

Lubricant compositions containing the subject additive combination are particularly useful as lubricants for steam turbines. Lubricant compositions designed for use in large steam turbines are unique in that they require very careful formulation to protect the machinery from rust and corrosion under very severe conditions of use. Technically, these steam turbines are used for the generation of electricity, and are of either stationary or marine installation. The volume of lubricant required for a turbine can, typically, be in the range of 10,000 or 20,000 gallons of lubricant. The change interval of lubricant for present day turbines is in the range of 3 to 5 years, and it is desired to increase this interval to about 10 years, if suitable lubricating compositions can be developed. Lubricating compositions used in these turbines are continuously subjected to operating temperatures in the neighborhood of about 340.degree.F., and it is desired for increased efficiency of the turbines to use operating temperatures in the range of 600.degree.-700.degree.F., if suitable lubricating compositions can be developed. Another problem encountered in the operation of these turbines is that moisture from the steam is continuously being introduced into the lubricant. The anti-oxidant component in the majority of lubricating compositions presently used for steam turbines is based upon a hindered phenol type additive. While these hindered phenols are excellent anti-oxidants, they suffer from the fact that they sublime under the operating temperatures employed and, accordingly, provision must be made to continuously introduce a new supply of antioxidant into the lubricating composition to replenish that lost through sublimation.

The anti-oxidant component of the subject additive combination comprises one or more alkylene dithiocarbamates corresponding to the general formula;

R.sub.1 R.sub.2 N--C(S)--S--X--S--(S)C--NR.sub.3 R.sub.4

wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently radicals selected from the group consisting of hydrogen and alkyl, or R.sub.1 and R.sub.2 taken together with the nitrogen to which they are attached are R.sub.5, or R.sub.3 and R.sub.4 taken together with the nitrogen to which they are attached are R.sub.6, wherein R.sub.5 and R.sub.6 are independently 5- or 6-membered heterocyclic groups. The combined total number of carbon atoms of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 is at least about eight and X represents an alkylene radical having up to about 8 carbon atoms. This component is used in the range of from about 0.1 to about 5% by weight of the lubricant composition, with a preferred range of from about 0.25 to about 1.0%.

Each of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 will preferably be an alkyl radical having from 1 to about 18 carbon atoms. The preferred range of carbon atoms in each of these alkyl radicals is from 1 to about 8. The total number of carbon atoms in R.sub.1, R.sub.2, R.sub.3 and R.sub.4 is at least about 8 with an upper limit of about 70 carbon atoms. However, the upper limit of the total number of carbon atoms is usually about 32.

When R.sub.1 and R.sub.2 are taken together with the nitrogen atom to which they are attached, they form a 5- or 6-membered heterocyclic group, R.sub.5, and when R.sub.3 and R.sub.4 are taken together with the nitrogen atom to which they are attached, they form a 5- or 6-membered heterocyclic group, R.sub.6. Thus, R.sub.5 and R.sub.6 are, independently, heterocylic radicals selected from the group consisting of pyrrolidinyl, piperidino, morpholino, and piperazinyl. The heterocyclic radicals, R.sub.5 and R.sub.6, may contain one or more, preferably one to three alkyl substituents (C.sub.1 -C.sub.6) on the heterocyclic ring. Thus, for example, R.sub.5 or R.sub.6, may be 2-methylmorpholino, 3-methyl-5-ethylpiperidino, 3-hexylmorpholino, tetramethylpyrrolidinyl, piperazinyl, 2,5-dipropylpiperazinyl, piperidino, 2-butylpiperazinyl, 3,4,5-triethylpiperidino, 3-hexylpyrrolidinyl, or 3-ethyl-5-isopropylmorpholino. Preferably, R.sub.5 and R.sub.6 are, independently, members selected from the group consisting of pyrrolidinyl and piperidino.

The alkylene radical, X, in the subject dithiocarbamates may be either a straight-chain alkylene, a branched-chain alkylene, or an aromatically substituted alkylene. In general, the range of carbon atoms in this alkylene group is from 1 to about 8. The preferred alkylene radical is methylene (--CH.sub.2 --).

The alkylene dithiocarbamates are known in the art and several methods for their preparation are also known. The anti-oxidant activity in motor oil of various alkylene dithiocarbamates has been reported by Denton and Thompson, Inst. Petrol. Rev. 20 (230) 46-54 (1966).

U.S. Pat. No. 2,384,577 issued to Thomas discloses a suitable general method for the preparation of the subject alkylene dithiocarbamates. This method involves the reaction of a salt of a dithiocarbamic acid with a suitable dihaloacyclic hydrocarbon in the presence of a suitable reaction medium. Suitable reaction media include alcohols, such as ethanol and methanol; ketones, such as acetone and methyl ethyl ketone; ethers, such as dibutyl ether and dioxane; and hydrocarbons, such as petroleum ether, benzene and toluene. This reaction is generally carried out at a temperature within the range of from about 25.degree. to 150.degree.C. depending upon the boiling point of the solvent used as the reaction medium. Nakai, Shioya, and Okawara, Makromol. Chem. 108 95-103 (1967) have reported the preparation of various ethylene dithiocarbamates by the reaction of an ethanolic solution of ethylenedichloride with an ethanolic solution of the appropriate sodium N,N-di-substituted dithiocarbamates.

U.S. Pat. Nos. 1,726,647 and 1,736,429 issued to Cadwell describe the preparation of phenylmethylene bis(dialkyldithiocarbamates), such as phenylmethylene bis(dimethyldithiocarbamate). The preparative procedure of Cadwell's patents is similar to that disclosed by Thomas and involves the reaction of a salt of a dialkyldithiocarbamate with benzal chloride to prepare the subject phenylmethylene bis(dialkyldithiocarbamates). Cadwell also discloses the preparation of the intermediate salt of a dialkyldithiocarbamate by the reaction of a dialkylamine, carbon disulfide, and an inorganic base.

A rather elegant process for the preparation of ethylene dithiocarbamates has been reported by Pilgram, Phillips and Korte, J. Org. Chem. 29 1848-50 (1964). This process involves the reaction of cyclic phosphoramidites derived from ethylene glycol with tetraalkylthiuram disulfides to form the corresponding ethylene bis (dialkyldithiocarbamates). The preparation of ethylene bis(dipropyldithiocarbamates) from tetrapropylthiuram disulfide and 2-piperidino-1,3,2-dioxaphospholane is exemplary of the Pilgram et al. process.

Unsymmetrical alkylene dithiocarbamates, such as ethylene (tetramethylene dithiocarbamate) (dibutyl dithiocarbamate) are conveniently prepared by suitable modification of the above procedures. Thus, one such modification involves the reaction of a mixture of amines with carbon disulfide and the inorganic base to prepare the intermediate salts, i.e., the substituted dithiocarbamates. The substituted dithiocarbamates derived from the mixed amines is then reacted with the appropriate dihaloalkane. Another modification involves the reaction of an excess of the dihaloalkane with one substituted dithiocarbamate, isolating the resulting monoester-halide, and reacting this monoesterhalide with the other substituted dithiocarbamate.

The anti-rust component of the subject additive combination comprises one or more rust inhibitors selected from the group consisting of aliphatic hydrocarbon-substituted succinic acids, aliphatic hydrocarbon-substituted succinic anhydrides and esterified reaction products obtained by the partial esterification of the aliphatic hydrocarbon-substituted acids or their anhydrides with at least one alkylene oxide or alkylene glycol. This partially esterified reaction product is prepared by the esterification of from about 0.1 mole to about 1.0 mole of the alkylene oxide or the alkylene glycol per mole of the aliphatic hydrocarbon-substituted succinic acid or anhydride.

This anti-rust component of the additive combination is used in an amount sufficient to improve the rust-inhibiting properties of the subject lubricant composition. Generally, the amount of the anti-rust component is in the range of from about 0.01 to about 1% by weight of the lubricant composition. The preferred range of the anti-rust component is from about 0.02 to about 0.1% by weight.

The compounds comprising the rust inhibitor used to prepare the subject lubricating compositions are known in the art, as well as methods for their preparation.

The aliphatic hydrocarbon-substituted succinic acids, which may be used as an anti-rust component and which are the precursor acids of the anhydride and ester anti-rust components, correspond to the general formula: ##SPC1##

wherein R' respresents the aliphatic hydrocarbon substituent.

The aliphatic hydrocabon substituent, R', will have from about 6 to about 80 aliphatic carbon atoms, with a preferred range of carbon atoms in the range of from about 8 to about 30. Accordingly, the molecular weight of the hydrocarbon substituent will, broadly, be in the range of from about 80 to about 1,150, with a preferred range of from about 110 to about 450.

This hydrocarbon substituent, R', is either a saturated or a substantially saturated aliphatic hydrocarbon substituent, depending upon the preparative method used. It may contain olefinic unsaturation up to a maximum of about 5 percent olefinic linkage based upon the total number of carbon-to-carbon covalent linkages present in the substituent. Preferably, the number of olefinic linkages will not exceed about 2 percent of the total covalent linkages. The hydrocarbon substituent may contain inert polar substituents provided they do not alter substantially the hydrocarbon character of the hydrocarbon substituent. Preferably, the upper limit on the percentage of polar substituent is about 10 percent by weight based upon the total weight of the hydrocarbon substituent. Exemplary polar substituents include halo, carbonyl, oxo (--O--), formyl, nitro, thio (--S--), etc.

The exact nature of the hydrocarbon substituent depends upon the method used to prepare the acids or their anhydrides. In essence, the preparation of these acids or anhydrides involves the reaction of an olefinic aliphatic hydrocarbon compound or a halogenated olefinic aliphatic hydrocarbon compound with maleic acid or anhydride to form the corresponding substituted succinic acid or anhydride. The product of this reaction is an alkenyl succinic acid or anhydride, which may be hydrogenated to the completely saturated, alkyl succinic acid or anhydride.

The source of the olefinic aliphatic hydrocarbon compound used for the preparation of the aliphatic hydrocarbon-substituted succinic acids or anhydrides depends upon the molecular weight range and nature of the substituent desired. For the preparation of the subject succinic acids or anhydrides with a hydrocarbon substituent of lower molecular weight, a preferred source of this hydrocarbon substituent is the low molecular weight polymers of the C.sub.2 -C.sub.4 olefins. Representative examples of these lower molecular weight polymers are tetrapropylene, triisobutylene, tetraisobutylene, etc. For the preparation of the succinic acids or anhydrides with a higher molecular weight substituent, a convenient source is the substantially saturated polymers or copolymers of monoolefins having from 2 to about 30 carbon atoms. Exemplary of these, are the higher molecular weight polymers of ethylene, propene, 1-butene, isobutylene, 1-octene, and 3-cyclohexyl-1-butene. Exemplary of useful copolymers are those derived from the copolymerization of isobutene with butadiene, isobutene with chloroprene, 1-hexene with 1,3-hexadiene and 1-octene with 1-hexene. Polymers of medial olefins, i.e., olefins in which the olefinic linkage is not at the terminal position, are also useful. These are illustrated by 2-butene, 3-pentene and 4-octene. Other convenient sources of the higher molecular weight aliphatic hydrocarbon substituent include substantially saturated petroleum fractions, saturated aliphatic hydrocarbons derived from highly refined high molecular weight white oils, and synthetic alkanes such as those obtained by the hydrogenation of high molecular weight olefin polymers.

These aliphatic hydrocarbon-substituted succinic acids and anhydrides are known in the art, and methods for their preparation, as well as representative examples of the types useful in the present invention are described in detail in the following U.S. Pat. Nos.: 3,172,892; 3,216,936; 3,219,666; 3,271,310; 3,272,746; 3,278,550; 3,281,428; 3,306,908; 3,316,771; 3,373,111; 3,381,022; 3,341,542; 3,344,170; 3,448,048; 3,454,607; 3,515,669; 3,522,179; 3,542,678; 3,542,680; 3,579,450; 3,632,510; 3,632,511; and 3,639,242. These patents are expressly incorporated herein by reference for their disclosure of the preparation of the subject acids or anhydrides and specific representative examples of such acids or anhydrides.

The alkylene oxides or alkylene glycols used to prepare the esterified reaction product with the above aliphatic hydrocarbon-substituted succinic acids or anhydrides will have from 2 to about 20 carbon atoms. Preferably, they will have from 2 to about 6 carbon atoms.

Representative examples of alkylene oxides useful in the preparation of the esterified reaction products of this invention are ethylene oxide, propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide, cyclohexene oxide, and 1,2-octylene oxide.

The glycols used to prepare the subject partially esterified reaction product may be either an alkylene glycol or a polyalkylene glycol. These glycols contain at least one alkylene oxide unit having from 2 to 7 carbon atoms. The most satisfactory glycols are those derived from ethylene oxide or propylene oxide or mixtures of these.

The polyethylene glycols correspond to the formula;

HO(CH.sub.2 CH.sub.2 O).sub.n CH.sub.2 CH.sub.2 OH

wherein n is an integer having a value of from 1 to about 9, preferably 1 or 2.

The polypropylene glycols correspond to the formula;

HO[CH(R")--CH(R'")--O].sub.m CH(R")--CH(R'")OH

wherein either R" or R'" is a methyl group and the other R is a hydrogen, and m is an integer having a value of from 1 to about 6, preferably 1 or 2.

Representative examples of alkylene glycols useful in the preparation of the esterified reaction products of this invention are ethylene glycol, propylene glycol, trimethylene glycol, butylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, diisobutylene glycol, and tributylene glycol.

Additional useful alkylene glycols include the following: HO(CH.sub.2 CH.sub.2 O).sub.7 CH.sub.2 CH.sub.2 OH; HO[CH(CH.sub.3)CH.sub.2 O].sub.5 CH(CH.sub.3)CH.sub.2 OH; HO[CH.sub.2 CH.sub.2 O].sub.3 --[CH(CH.sub.3)CH.sub.2 O].sub.3 --CH(CH.sub.3)CH.sub.2 OH.

The esterified reaction product of the hydrocarbon-substituted succinic acids or anhydrides is a partially esterified product. Thus, from about 0.1 mole to about 1.0 of the alkylene oxide of alkylene glycol is reacted per mole of the acid or anhydride. This partially esterified product may be prepared by any of several methods known in the art. One such method consists of mixing the anhydride and the glycol in the absence of a solvent and heating this mixture at a temperature above about 100.degree.C., preferably between about 150.degree. and 300.degree.C. for a period of time sufficient to effect the reaction. When the partial esterification is effected using an alkylene oxide a convenient preparative method involves adding the alkylene oxide portion-wise to the anhydride at a temperature within the range of from about 50.degree. to about 100.degree.C.

Of course, the substituted succinic acid can be used in any of the preparative methods in the place of the anhydride. However, since the succinic acid readily undergoes dehydration at temperatures above about 100.degree.C. to form the anhydride, in most cases it is preferred to use the anhydride.

In some instances it may be advantageous to conduct the esterification using a solvent as this improves mixing and control of the reaction temperature. Useful solvents include xylene, toluene, diphenylether, chlorobenzene, and mineral oil. Any water formed during this esterification is conveniently removed by distillation as the reaction proceeds.

The esterification may be conducted in the presence of a catalyst. Useful esterification catalysts include sulfuric acid, pyridine hydrochloride, hydrochloric acid, benzenesulfonic acid, and p-toluenesulfonic acid. The amount of catalyst used is generally in the range of from about 0.1 to about 5% by weight.

Further details concerning the esterification of the subject type of hydrocarbon-substituted succinic acids and anhydrides with alkylene oxides and alkylene glycols is found in the prior art, such as U.S. Pat. Nos. 2,962,443; 3,405,042; 3,117,091; 3,255,108; and 3,381,022.

The additive combination of the present invention is effectively employed using base oils of lubricating viscosity derived from a variety of sources. Thus, base oils derived from both natural and synthetic sources are contemplated for the preparation of lubricating oil and grease compositions of the present invention. The natural oils include animal oils, such as lard oil; vegetable oils, such as castor oil; and mineral oils, such as solvent-refined or acid-refined mineral oils of the paraffinic and/or naphthenic type. Also base oils derived from coal or shale are useful.

Useful synthetic lubricating base oils include hydrocarbon oils derived from the polymerization or copolymerization of olefins, such as polypropylene, polyisobutylene and propylene-isobutylene copolymers; and the halo-hydrocarbon oils, such as chlorinated polybutylene. Other useful synthetic base oils include those based upon alkyl benzenes, such as dodecylbenzene, tetradecylbenzene, and those based upon polyphenols, such as biphenyls, and terphenyls.

Another known class of synthetic oils useful as base oils for the subject lubricant compositions are those based upon alkylene oxide polymers and interpolymers, and those oils obtained by the modification of the terminal hydroxy groups of these polymers, (i.e., by the esterification or etherification of the hydroxy groups). Thus, useful base oils are obtained from polymerized ethylene oxide or proplyene oxide or from the copolymers of ethylene oxide and propylene oxide. Useful oils include the alkyl and aryl ethers of the polymerized alkylene oxides, such as methylpolyisopropylene glycol ether, diphenyl ether of polyethylene glycol, and diethyl ether of propylene glycol. Another useful series of synthetic base oils is derived from the esterification of the terminal hydroxy group of the polymerized alkylene oxides with mono- or polycarboxylic acids. Exemplary of this series is the acetic acid esters or mixed C.sub.3 -C.sub.8 fatty acid esters or the C.sub.13 Oxo acid diester of tetraethylene glycol.

Another suitable class of synthetic lubricating oil comprise the esters of dicarboxylic acids, such as phthalic acid, succinic acid, oleic acid, azelaic acid, suberic acid, sebacic acid, with a variety of alcohols. Specific examples of these esters include dibutyl adipate, di(2-ethylhexyl)sebacate, and the like. Silicone based oils such as polyalkyl-, polyaryl-, polyalkoxy-, or polyaryloxy-siloxane oils and the silicate oils, i.e., tetraethyl silicate, comprise another useful class of synthetic lubricants. Other synthetic lubricating oils include liquid esters of phosphorus-containing acid, such as tricresyl phosphate, polymerized tetrahydrofurans, and the like.

The subject additive combination can be used alone or in combination with other lubricant additives known in the prior art. A brief survey of conventional additives for lubricating compositions is contained in the publications, LUBRICANT ADDITIVES, by C.V. Smalheer and R. Kennedy Smith, published by the Lezius-Hiles Co., Cleveland, Ohio (1967) and LUBRICANT ADDITIVES, by M.W. Ranney, published by Noyes Data Corp., Park Ridge, N.J. (1973). These publications are incorporated herein by reference to establish the state of the art in regard to identifying both general and specific types of other additives which can be used in conjunction with the additive combination of the present invention.

In general, these additional additives include detergents of the ash-containing type, ashless dispersants, viscosity index improvers, pour point depressants, antifoam agents, extreme pressure agents, anti-wear agents, other rust-inhibiting agents, other oxidation inhibitors, and corrosion inhibitors.

The ash-containing detergents are the well known neutral basic alkali or alkaline earth metal salts of sulfonic acids, carboxylic acids or organo-phosphorus-containing acids. The most commonly used salts of these acids are the sodium, potassium, lithium, calcium, magnesium, strontium, and barium salts. The calcium and barium salts are used more extensively than the others. The "basic salts" are those metal salts known to the art wherein the metal is present in a stoichiometrically larger amount than that necessary to neutralize the acid. The calcium- and barium-overbased petrosulfonic acids are typical examples of such basic salts.

The extreme pressure agents, corrosion-inhibiting agents, and oxidation-inhibiting agents, are exemplified by chlorinated aliphatic hydrocarbons, such as chlorinated wax; organic sulfides and polysulfides, such as benzyldisulfide, bis-(chlorobenzyl)disulfide, dibutyl tetrasulfide, sulfurized sperm oil, sulfurized methyl ester of oleic acid, sulfurized alkylphenol, sulfurized dipentene, sulfurized terpene, and sulfurized Diels-Alder adducts; phosphosulfurized hydrocarbons, such as the reaction product of phosphorus sulfide with turpentine or methyloleate; phosphorus esters such as the dihydrocarbon and trihydrocarbon phosphites, i.e., dibutyl phosphite, diheptyl phosphite, dicylohexyl phosphite, pentaphenyl phosphite, dipentylphenyl phosphite, tridecyl phosphite, distearyl phosphite, and polypropylene substituted phenol phosphite; metal thiocarbamates, such as zinc dioctyldithiocarbamate and barium heptylphenol dithiocarbamate; and Group II metal salts of phosphorodithioic acid, such as zinc dicyclohexyl phosphorodithioate, and the zinc salts of a phosphorodithioic acid.

The ashless detergents or dispersants are a well known class of lubricant additives and are extensively discussed and exemplified in the above-cited publications by Smalheer et al. and Ranney and the references cited therein. Particularly useful types of ashless dispersants are based upon the reaction products of hydrocarbon-substituted succinic acid compounds and polyamines or polyhydric alcohols. These reaction products may be post-treated with materials, such as alkylene oxides, carboxylic acids, boron compounds, carbon disulfide and alkenyl cyanides to produce further useful ashless dispersants.

Pour point depressing agents are illustrated by the polymers of ethylene, propylene, isobutylene, and poly-(alkyl methacrylate). Anti-foam agents include polymeric alkyl siloxanes, poly(alkyl methacrylates), terpolymers of diacetone acrylamide and alkyl acrylates or methacrylates, and the condensation products of alkyl phenols with formaldehyde and an amide. Viscosity index improvers include polymerized and copolymerized alkyl methacrylates and polyisobutylenes.

When additional additives are used in lubricant compositions comprising the subject additive combination, they are used in concentrations in which they are normally employed in the art. Thus, they will generally be used in a concentration of from about 0.001 up to about 25% by weight of total composition, depending, of course, upon the nature of the additive and the nature of the lubricant composition. For example, ashless dispersants can be employed in amounts from about 0.1 to about 10% and metal-containing detergents can be employed in amounts from about 0.1 to about 20% by weight. Other additives, such as pour point depressants, extreme pressure additives, viscosity index improving agents, anti-foaming agents, and the like, are normally employed in amounts of from about 0.001 to about 10% by weight of the total composition, depending upon the nature and purpose of the particular additive.

A clear understanding of the new additive combination of this invention and lubricant compositions containing this combination may be obtained from the examples given below, which illustrate the presently preferred best modes of carrying out this invention.

EXAMPLE 1

A lubricating composition suitable for use as a steam turbine lubricating oil is prepared using a 200 N base mineral oil, 0.05% of an oil solution (37% oil) of a partially esterified dodecenyl succinic acid, 1% of methylene bis(dibutyldithiocarbamate), and 200 ppm of a conventional anti-foaming agent based upon a polymer of 2-ethylhexyl acrylate and ethyl acrylate.

The partially esterified dodecenyl succinic acid used above is prepared by treating 95 parts by weight of a 61% oil solution of dodecenyl succinic acid with 5 parts by weight of propylene oxide.

The methylene bis(dibutyldithiocarbamate) used above is prepared by the reaction of dibutylamine, carbon disulfide, sodium hydroxide and methylene dichloride.

Thus, 627 grams (4.86 moles) of di-n-butylamine, 240 grams (3 moles) of a 50% aqueous solution of sodium hydroxide, 200 grams of toluene, and 200 grams of isopropanol are added to a reactor. Carbon disulfide (228 grams, 3 moles) is slowly added to the above mixture over a period of about 5 hours, while the temperature of the reaction mixture is maintained under about 42.degree.C. After completion of the addition of the carbon disulfide, the mixture is slowly heated to about 65.degree.C. to expell any unwanted carbon dilsulfide. Methylene dichloride (255 grams, 3 moles) is added slowly to the reaction mixture over a period of about 2.5 hours and during this addition period the temperature will increase to about 75.degree.C. After the addition of the methylene dichloride, the mixture is heated for an additional 2 hours at a temperature in the range of 60.degree.-65.degree.C. The mixture is then washed with four 150 ml portions of water and the last traces of volatile material are stripped from the reaction mixture using a vacuum of about 120 mm Hg at a temperature of about 122.degree.C. After vacuum stripping, the mixture is filtered to yield the desired clear liquid product, methylene bis(dibutyldithiocarbamate).

EXAMPLE 2

A lubricating composition suitable for use as a steam turbine lubricating oil is prepared using a 200 N base mineral oil, 0.05% of the oil solution of the partially esterified dodecenyl succinic acid used in Example 1, and 0.5% of methylene bis(dibutyldithiocarbamate).

When the methylene bis(dibutyldithiocarbamate) used as the anti-oxidant of Example 2 is replaced with methylene bis(tetramethylenedithiocarbamate), or benzylidene bis(pentamethylenedithiocarbamate), or 1,4-butylene bis(butyldithiocarbamate), or 1,8-octylene bis(diethyldithiocarbamate), or 1,3-propylene bis(decyldithiocarbamate), or 1,4-hexylene bis(dipropyldithiocarbamate), or ethylene bis(4-morpholinecarbodithioate), or ethylene bis(1-piperazinecarbodithioate), suitable lubricating compositions are obtained.

EXAMPLE 2-A

When the partially esterified dodecenyl succinic acid used above is replaced with the reaction product (0.25:1 mole) of 1,2-butylene oxide and dodecenyl succinic anhydride; or the reaction product (0.1:1 mole) of dipropylene glycol and hexadecyl succinic anhydride; or the reaction product (0.2:1 mole) of ethylene oxide and a polyisobutenyl succinic anhydride, wherein the polyisobutenyl substituent has about 24 aliphatic carbon atoms; or a polypropylene succinic acid, wherein the polypropylene substituent has about 60 aliphatic carbon atoms; suitable lubricating compositions are obtained.

EXAMPLE 3

A lubricating composition suitable for use as a steam turbine lubricating oil is prepared using a 200 N base mineral oil, 0.05% of the oil solution of the partially esterified dodecenyl succinic acid used in Example 1, and 1% by weight of ethylidene bis(dibutyldithiocarbamate).

The ethylidene bis(dibutyldithiocarbamate) used above is prepared by a process analogous to that used to prepare the anti-oxidant component in Example 1 using di-n-butylamine, carbon disulfide, sodium hydroxide, and ethylidene dichloride.

EXAMPLE 4

A lubricating composition suitable for use as a gear oil is prepared using a SAE 90 base mineral oil, 0.5% of zinc 2-ethylhexylisobutyl phosphorodithioate as a combination extreme pressure agent and oxidation inhibitor, 0.1% of the partially esterified dodecenyl succinic acid of Example 1, 1.6% (0.5% sulfur) of methylene bis(dibutyldithiocarbamate), and 200 ppm of the anti-foam agent of Example 1.

When the methylene bis(dibutyldithiocarbamate) is replaced with benzylidene bis(diethyldithiocarbamate), or methylene bis(3-ethylpiperidinecarbodithioate), or 1,4-butylene bis(decyldithiocarbamate), or 1,8-octylene bis(diisopropyldithiocarbamate), or ethylene bis(3,4-dimethylpyrrolidinecarbodithioate), suitable lubricating compositions are obtained.

EXAMPLE 4-A

When the partially esterified dodecenyl succinic acid used above is replaced with the reaction product (0.3:1 mole) of trimethylene glycol and a polyisobutenyl succinic anhydride, wherein the polyisobutenyl substituent has about 80 aliphatic carbon atoms; or the reaction product (0.9:1 mole) of propylene glycol and a diisobutylene succinic anhydride; or a poly(ethylene-propylene)substituted succinic acid, wherein the poly(ethylene-propylene)substituent has about 30 aliphatic carbon atoms; or the reaction product (1:1 mole) of an alkylene glycol corresponding to the formula HO[CH.sub.2 CH.sub.2 O].sub.3 --[CH(CH.sub.3)CH.sub.2 O].sub.3 --CH(CH.sub.3)CH.sub.2 OH and dodecenyl succinic anhydride; suitable lubricating compositions are obtained.

EXAMPLE 5

A lubricating composition suitable for use as a crankcase lubricant is prepared using a 10W-40 mineral lubricating oil base and, as additives, 8.8% of a polyisodecylacrylate viscosity index improver; 2.92% of an ashless dispersant, which is the reaction product (1:2 eq.) of a polyisobutenyl succinic anhydride and tetraethylene pentamine prepared according to the procedure of U.S. Pat. No. 3,127,892; 3.05% of a dispersant which is the reaction product (1:1 eq) of a polyisobutenyl succinic anhydride and tetraethylene pentamine and boric acid as described in U.S. Pat. No. 3,254,025; 1.61% of a dispersant which is the reaction product (1:1 eq) of a polyisobutenyl succinic anhydride and pentaerythritol; 0.56% of a 61% solution of dodecenyl succinic acid in oil; 1.50% of methylene bis(dibutyldithiocarbamate); 0.78% of a commercial hindered phenol based anti-oxidant; and 40 ppm of an anti-foaming agent.

EXAMPLE 5-A

When the methylene bis(dibutyldithiocarbamate) used in the above formulation is replaced with methylene bis(tetramethylenedithiocarbamate), or ethylene (tertramethylenedithiocarbamate)(pentamethylenedithiocarbamate), or 1,4-butylene(pentamethylenedithiocarbamate)(di-n-butyldithiocarbamate), or benzylidene bis(pentamethylenedithiocarbamate), or methylene (4-morpholinecarbodithioate)(1-piperazinecarbodithioate), suitable lubricating compositions are obtained.

EXAMPLE 6

A lubricating composition suitable for use as a crankcase lubricant is prepared using a 10W-40 mineral lubricating oil base, and, as additives, 8.8% of a polyisodecylacrylate viscosity improving agent; 2.92% of the ashless dispersant of Example 5; 3.05% of the boron-containing dispersant of Example 5; 1.57% of a dispersant based upon the reaction product of a chlorinated polyisobutene, acrylic acid, tetraethylene pentamine and phthalic acid; 0.56% of a 61% solution of dodecenyl succinic acid in oil; 0.78% of a commercial hindered phenol anti-oxidant; 0.75% of methylene bis(dibutyldithiocarbamate); and 40 ppm of a conventional anti-foaming agent.

EXAMPLE 7

A suitable crankcase lubricating composition is obtained when the 0.75% of methylene bis(dibutyldithiocarbamate) in the composition of Example 6 is replaced with 1.5% of methylene bis(dibutyldithiocarbamate).

EXAMPLE 8

A lubricating composition suitable for use as a crankcase lubricant is prepared using a 10W-50 mineral lubricating oil base and, as additives, 3.4% of a hydrogenated butadiene-styrene copolymer as a viscosity index improver; 0.2% of a conventional pour point depressant (PAM-140); 60ppm of a conventional anti-foaming agent; 1.0% of a dispersant based upon a reaction product of a polybutenyl succinic anhydride, tetramethylene pentamine and phthalic acid; 0.1% of a commercial thiadiazole based copper deactivator (Amoco 150); 1.0% of a 61% oil solution of dodecenyl succinic anhydride; and 1.0% of methylene bis(dibutyldithiocarbamate).

EXAMPLE 9

A lubricating composition suitable for use as a hydraulic fluid is prepared using a 200 N mineral lubricating base oil, 1.0% of a corrosion inhibitor based upon an adduct (1:1 eq) of diisooctylphosphinodithioic acid and methyl acrylate, 0.05% of an oil solution (37% oil) of the partially esterified dodecenyl succinic acid described in Example 1, and 0.25% of methylene bis(dibutyldithiocarbamate).

EXAMPLE 10

A lubricating composition suitable for use as a hydraulic fluid is prepared using a 350 N mineral lubricating base oil, 0.50% of tri(4-methyl-2-pentyl)phosphite as an extreme pressure agent, 0.05% of an oil solution (37% oil) of the reaction product obtained by the treatment of 1,000 parts of an oil solution (39% oil) of dodecenyl succinic acid with 60.5 parts of propylene oxide, and 0.25% of methylene bis(dibutyldithiocarbamate).

EXAMPLE 11

A lubricating composition is prepared using a synthetic lubricating base oil consisting essentially of the diethyl ether of propylene glycol having an average molecular weight of about 15,000, 0.05% of the oil solution of the partially esterified dodecenyl succinic acid described in Example 1, and 1% of methylene bis(dibutyldithiocarbamate).

In the above examples, as well as in the specification and claims, all percentages are expressed as percentage by weight, and all parts are expressed as parts by weight, unless otherwise indicated. Likewise, all temperatures are expressed in .degree.C., unless otherwise indicated.

The lubricating composition of the present invention may, of course, be prepared by a variety of methods known in the art. One convenient method is to add the additive combination in the form of a concentrated solution or suspension to a sufficient amount of the base lubricant to form the subject lubricating composition. This additive concentrate contains the separate ingredients of the combination in the proper ratio to each other to provide the proper ratio of anti-oxidant and rust-inhibitor in the final lubricating composition. The concrete may also contain appropriate amounts of any additional additive which it is desired to incorporate in the final composition. Generally, the concentrate will comprise from about 20 to about 90 percent of the additive combination with the balance being a substantially inert normally liquid solvent or diluent, plus any additional additive used. Suitable solvents and diluents include any of the above-discussed natural or synthetic oils, kerosene, xylene, benzene, mixtures of two or more of these and other solvents and diluents known in the art. Hereafter these substantially inert, normally liquid solvents and diluents used in the preparation of additive concentrates are referred to collectively as carriers. Normally the carriers are oil-soluble, at least to the extent of their concentration in the final lubricating compositions prepared from them.

Claims

What is claimed is:

1. A lubricant composition comprising a major proportion of a lubricating oil and a minor proportion, sufficient to improve the anti-oxidant and rust-inhibiting properties of the composition, of an additive combination comprising (A) one or more alkylene dithiocarbamates and (B) one or more rust inhibitors selected from the group consisting of aliphatic hydrocarbon-substituted succinic acid, aliphatic hydrocarbon-succinic acid anhydride, and the reaction product obtained by the esterification of the acid or the anhydride with from about 0.1 mole to about 1.0 mole per mole of the acid or the anhydride, of at least one alkylene oxide or alkylene glycol containing up to about 20 carbon atoms; wherein the alkylene dithiocarbamate corresponds to the formula:

R.sub.1 R.sub.2 N--C(S)--S--X--S--(S)C--NR.sub.3 R.sub.4

in which R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are independently radicals selected from the group consisting of hydrogen and alkyl, or R.sub.1 and R.sub.2, taken together with the nitrogen to which they are attached, are R.sub.5, or R.sub.3 and R.sub.4 taken together with the nitrogen to which they are attached, are R.sub.6, wherein R.sub.5 and R.sub.6 are independently 5- or 6- membered heterocyclic groups, and the combined total number of carbon atoms of R.sub.1, R.sub.2, R.sub.3, and R.sub.4 is at least about 8, and X represents an alkylene radical having up to about 8 carbon atoms.

2. The lubricant composition of claim 1, wherein the anti-oxidant component of the additive combination is present in the range of from about 0.1 to about 5%.

3. The lubricant composition of claim 1, wherein the anti-rust component of the additive combination is present in the range of from about 0.01 to about 1%.

4. The lubricant composition of claim 1, wherein R.sub.5 and R.sub.6 are heterocyclic radicals selected from the group consisting of pyrrolidinyl and piperidino.

5. The lubricant composition of claim 1, wherein the aliphatic hydrocarbon substituent of the aliphatic hydrocarbon-succinic acid or anhydride has from about 8 to about 30 aliphatic carbon atoms.

6. The lubricant composition of claim 5, wherein the anti-rust component of the additive combination is the reaction product of the succinic acid or its anhydride with an alkylene oxide or alkylene glycol having from 2 to 6 carbon atoms.

7. The lubricant composition of claim 6, wherein R.sub.5 and R.sub.6 are heterocyclic radicals selected from the group consisting of pyrrolidinyl and piperidino.

8. The lubricant composition of claim 6, wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are, independently, alkyl radicals having from 1 to 8 carbon atoms.

9. The lubricant composition of claim 6, wherein the alkylene radical, X, is a methylene radical.

10. The lubricant composition of claim 6, wherein the anti-rust component is present in the range of from about 0.02 to about 0.1% and the anti-oxidant component is present in the range of from about 0.25 to about 1%.

11. The lubricant composition of claim 5, wherein the anti-rust component of the additive combination is an aliphatic hydrocarbon-succinic acid.

12. The lubricating composition of claim 11, wherein R.sub.5 and R.sub.6 are heterocyclic radicals selected from the group consisting of pyrrolidinyl land piperidino.

13. The lubricant composition of claim 11, wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are, independently, alkyl radicals having from 1 to 8 carbon atoms.

14. The lubricating composition of claim 11, wherein the anti-rust component is present in the range of from about 0.01 to about 0.1% and the anti-oxidant component is present in the range of from about 0.25 to about 1%.

15. The lubricating composition of claim 11, wherein the alkylene radical, X, is a methylene radical.

16. An additive concentrate comprising a substantially inert carrier and from about 20 to about 90 percent of the additive combination of claim 1.

17. An additive concentrate comprising a substantially inert carrier and from about 20 to about 90 percent of the additive combination of claim 8.

18. An additive concentrate comprising a substantially inert carrier and from about 20 to about 90 percent of the additive combination of claim 15.

19. A steam turbine lubricant composition comprising a major proportion of lubricating oil and a minor proportion, sufficient to improve the anti-oxidant and rust-inhibiting properties of the composition, of an additive combination comprising (A) one or more alkylene dithiocarbamates and (B) one or more rust inhibitors selected from the group consisting of aliphatic hydrocarbon-substituted succinic acid, aliphatic hydrocarbon-succinic acid anhydride, and the reaction product obtained by the esterification of the acid or anhydride with from about 0.1 mole to about 1.0 mole per mole of the acid or anhydride, of at least one alkylene oxide or alkylene glycol containing up to about 20 carbon atoms; wherein the alkylene dithiocarbamate corresponds to the formula:

R.sub.1 R.sub.2 N--C(S)--S--X--S--(S)C--NR.sub.3 R.sub.4

in which R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently radicals selected from the group consisting of hydrogen and alkyl, or R.sub.1 and R.sub.2, taken together with the nitrogen to which they are attached, are R.sub.5, or R.sub.3 and R.sub.4 taken together with the nitrogen to which they are attached, are R.sub.6, wherein R.sub.5 and R.sub.6 are independently 5- or 6-membered heterocyclic groups, and the combined total number of carbon atoms of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 is at least about 8, and X represents an alkylene radical having up to about 8 carbon atoms.