GB1581653A - Lubricating oil additive composition - Google Patents

Description

PATENT SPECIFICATION ( 11) 1 581653

C: ( 21) Application No 31321/79 ( 22) Filed 31 March 1977 b.1 ( 62) Divided out of No 1581651 ( 19) ( 31) Convention Application No 673063 _ 1 ( 32) Filed 1 April 1976 in ( 33) United States of America (US) ( 44) Complete Specification published 17 Dec 1980 _-I ( 51) INT CL 3 C 10 M 1/38 1/32 1/34 3/26 3/28 3/32 ( 52) Index at acceptance C 5 F 102 103 111 131 136 323 324 326 330 332 333 342 343 370 372 373 415 451 452 477 491 519 537 591 593 598 605 609 X 610 621 622 623 632 640 642 646 658 672 674 678 691 762 809 A B KK ( 72) Inventor WARREN LOWE ( 54) LUBRICATING OIL ADDITIVE COMPOSITION ( 71) We, CHEVRON RESEARCH COMPANY, a corporation duly organised under the laws of the State of Delaware, United States of America, of 575 Market Street, San Francisco, California, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the 5 following statement:-

This invention relates to an antioxidant additive composition for a crankcase lubricating oil and to a lubricating oil composition having improved antioxidation properties.

Hydrocarbon oils are partially oxidized when contacted with oxygen at 10 elevated temperatures for long periods The internal combustion engine is a model oxidator, since it contacts a hydrocarbon motor oil with air under agitation at high temperatures Also, many of the metals (iron, copper, lead, nickel, etc) used in the manufacture of the engine and in contact with both the oil and air, are effective oxidation catalysts which increase the rate of oxidation The oxidation in motor oils 15 is particularly acute in the modern internal combustion engine which is designed to operate under heavy work loads and at elevated temperatures.

The oxidation process produces acidic bodies within the motor oil which are corrosive to typical copper, lead, and cadmium engine bearings It has also been discovered that the oxidation products contribute to piston ring sticking, the 20 formation of sludges within the motor oil and an overall breakdown of viscosity characteristics of the lubricant.

Several effective oxidation inhibitors have been developed and are used in almost all of the conventional motor oils today Typical of these inhibitors are the sulfurized oil-soluble organic compounds, such as wax sulfides and polysulfides, 25 sulfurized olefins, sulfurized fatty acid esters, and sulfurized olefin esters, as well as zinc dithiophosphates and the oil-soluble phenolic and aromatic amine antioxidants These inhibitors, while exhibiting good antioxidant properties, are burdened by economic and oil contamination problems It is preferred to maintain the sulfur content of the oil as low as possible, while at the same time receiving the 30 benefits of the antioxidation property A need, therefore, exists for an improved antioxidant that is stable at elevated temperatures, that can be employed in reduced concentrations, and that is economical and easy to produce.

U.S Patent 2,718,501 discloses a synergistic mixture of a sulfurcontaining compound such as a wax sulfide or dioctadecyl disulfide, and an aromatic amine 35 compound having at least 2 aromatic rings, such as phenyl alpha-naphthyl amine, for use in preventing oxidation in lubricating oils.

U.S Patent 2,729,691 discloses a mixture of an arylamine antioxidant and a synergistic amount of an alkylenediamine for protecting organic material from oxidation 40 U.S Patent 2,958,663 discloses an extreme pressure lubricant composition containing from 0 01 to 5 per cent each of sulfurized oleic acid, C,8-C 22 alkenyl succinic acid, chlorinated paraffin wax containing from 20 to 60 per cent chlorine, diphenylamine and N,N-salicylal-1,2-propylenediamine.

U.S Patent 3,345,292 discloses stabilized alkyl substituted diaryl sulfides for use as functional fluids where the stabilizer can be diarylamine or alkylated phenol.

It is an object of this invention to provide a synergistic additive composition having antioxidant properties in crankcase lubricating oil compositions.

According to one aspect of the invention, there is provided an antioxidant 5 additive composition for a crankcase lubricating oil, the additive composition comprising in admixture ( 1) an oil-soluble antioxidant selected from sulfurized aromatic and alkyl sulfides and polysulfides, sulfurized olefins, sulfurized carboxylic acid esters and sulfurized ester-olefins, and ( 2) a tertiary amine of the general formula: 10 (R 2)a N, or wherein each R 2 is independently C 3-Co alkyl, phenyl, or phenyl substituted by 1 or 2 alkyl groups of I-12 carbon atoms, R 4 is alkylene of at least 2 carbon atoms, X 15 is hydrogen or -NA 2 with each A being independently C,-C,8 alkyl, and Het is a carbon chain forming with the N atom a 5 or 6-membered heterocyclic ring, optionally containing in place of one carbon atom an additional O hetero atom.

According to another aspect of the invention, there is provided a lubricating oil composition comprising an oil of lubricating viscosity and an antioxidant 20 additive composition as described above.

It has been found that the defined antioxidants in combination with the defined amines complement each other in a synergistic manner, resulting in a combination having antioxidant properties superior to either additive alone The amine component alone has virtually no antioxidant effect However, when the 25 defined combination of amine and antioxidant is added to a lubricating oil, less of the antioxidant is needed to obtain oxidation control than when the amine is not present.

Preferably, from 2 to 40 millimols of an oil-soluble zinc salt is present per kilogram of the lubricating oil composition While this zinc salt is not required to 30 achieve the synergistic effect from the combination of the antioxidant and the amine, an improved lubricating oil composition results from the use of all three additive components.

The compositions of this invention are highly stable additives for crankcase lubricating oils and impart excellent antioxidant properties to these oils 35 In a preferred embodiment of the lubricating oil composition, 0 25 to 10 weight per cent of the antioxidant is present and 0 001 to 5 weight per cent of the amine is present The weight ratio of the antioxidant to amine is ordinarily in the range of 1 to 0 001-21.

More preferably, 0 25 to about 2 weight per cent of the antioxidant is present 40 in the lubricating oil More preferably, the amine is present in the amount of 0 01 to 0.3, preferably 0 05 to 0 3 weight per cent.

In a further preferred embodiment, from 9 to 30 mmols per kilogram of the oilsoluble zinc salt is present.

The class of antioxidants which may be used are conventional sulfur 45 containing antioxidants selected from sulfurized aromatic and alkyl sulfides and polysulfides, e g sulfurized wax sulfides or polysulfides, sulfurized olefins, sulfurized carboxylic acid esters and sulfurized ester-olefins.

The sulphurized fatty acid esters are prepared by reacting sulfur, sulfur monochloride, and/or sulfur dichloride with an unsaturated fatty ester under 50 elevated temperatures Typical esters include C,-C 20 alkyl esters of C 8C 24 unsaturated fatty acids, such as palmitoleic, oleic, ricinoleic, petroselinic, vaccenic, linoleic, linolenic, oleostearic, licanic, paranaric, tariric, gadoleic, arachidonic and cetoleic Particularly good results have been obtained with mixed unsaturated fatty acid esters, such as are obtained from animal fats and vegetable oils, such as tall oil, 55 linseed oil, olive oil, castor oil, peanut oil, rape oil, fish oil and sperm oil.

Exemplary fatty esters include lauryl tallate, methyl oleate, ethyl oleate, lauryl oleate, cetyl oleate, cetyl linoleate, lauryl ricinoleate, oleyl linoleate, oleyl stearate, and alkyl glycerides.

Cross-sulfurized ester olefins, such as a sulfurized mixture of C,0-C 25 olefins 60 with fatty acid esters of C,0-C 2 S fatty acids and C,-C 2 S alkyl or alkenyl alcohols, wherein the fatty acid and/or the alcohol is unsaturated may also be used.

1,581,653 Sulfurized olefins which may be used as an antioxidant in the practice of this invention are prepared by the reaction of the C 3-C 6 olefin or a lowmolecularweight polyolefin derived therefrom with a sulfur-containing compound such as sulfur, sulfur monochloride, and/or sulfur dichloride.

Another class of organic sulfur-containing compounds which may be used is 5 sulfurized aliphatic esters of an olefinic mono or dicarboxylic acid, for example aliphatic alcohols of 1-30 carbon atoms, used to esterify monocarboxylic acids such as acrylic acid, methacrylic acid and 2,4-pentadienoic acid or fumaric acid, maleic acid, or muconic acid Sulfurization is carried out by reacting these esters with elemental sulfur, sulfur monochloride and/or sulfur dichloride 10 The preferred antioxidants are the sulphurised aromatic and alkyl sulfides, such as sulphurised dibenzyl sulfide, dixylyl sulfide, dicetyl sulfide, diparaffin wax sulfide and polysulfide and cracked wax-olefin sulfides Particularly preferred are the sulphurised derivatives of the paraffin wax thiomers described in U S Patent 2,346,156 15 All of the sulfides and polysulfides included within the scope of this invention are sulfurized sulfides and polysulfides That is, the sulfide or polysulfide has been reacted with additional sulfur, sulfur monochloride or sulfur dichloride after the intitial formation of the sulfide Residual chlorine that may be present in the antioxidant after sulfurization is not detrimental and may be beneficial 20 The second component of the additive composition for use in lubricating oils is a tertiary amine.

The oil-soluble tertiary amines which can be used are those of the formula (R 2)3 N or H eg N+ R 4 +>X 25 In the non-heterocyclic compounds, each R 2 is independently C 3-Co alkyl, phenyl or phenyl substituted by 1 or 2 alkyl groups of up to 12 carbon atoms.

Preferably each R 2 is the same and is selected from C 3-C 6 alkyl or phenyl.

Typical alkyl-substituted phenyl groups include tolyl, xylyl, tetrapropenylphenyl and octylphenyl 30 For the heterocyclic compounds, Het is a carbon chain forming with the N atom a 5 or 6-membered heterocyclic ring optionally containing in place of one carbon atom an additional O hetero atom R 4 is alkylene of at least 2 carbon atoms, and X is hydrogen or -NA 2 where each A is independently C 1-C 18 alkyl Each N atom has no bonds directly to a hydrogen atom The ring may be substituted by one 35 or two alkyl groups that do/not affect the synergistic activity of the amine.

The compounds are conventional compounds that can be prepared by wellknown methods.

The zinc salts which may be used in this invention are oil-soluble zinc salts.

They are used in the lubricating oil to supply from 9 to 40 mmols of zinc per 40 kilogram of oil.

The zinc salt is preferably a zinc dihydrocarbyldithiophosphate having from 4 to 20 carbon atoms in each hydrocarbyl group The zinc dihydrocarbyldithiophosphate is formed by reacting the corresponding dihydrocarbyldithiophosphoric acid with a zinc base, such as zinc oxide, zinc 45 hydroxide and zinc carbonate The hydrocarbyl portions may be all aromatic, all aliphatic, or mixtures thereof.

Examplary zinc dihydrocarbyldithiophosphates include:

zinc di(n-octyl)dithiophosphate, zinc butyl isooctyl dithiophosphate, 50 zinc di( 4-methyl-2-pentyl) dithiophosphate, zinc di(tetrapropenylphenyl)dithiophophate, zinc di( 2-ethyl 1-hexyl)dithiophosphate, zinc di(isooctyl)dithiophosphate, zinc di(hexyl)dithiophosphate, 55 zinc di(ethylphenyl)dithiophosphate, zinc di(amyl)dithiophosphate, zinc di(alkylphenyl)dithiophosphate, zinc butylphenvldithiophosphate, and zinc di(octadecyl)dithiophosphate 60 1,581,653 Preferred compounds are those zinc dihydrocarbyldithiophosphates having from 4 to 18 carbon atoms in each hydrocarbon group Especially preferred are the zinc dialkyldithiophosphates wherein each alkyl group typically contains from 4 to 8 carbon atoms and the zinc di(alkylaryl)dithiophosphates wherein each alkylaryl group contains from 15 to 21 carbon atoms 5 The lubricating oil composition of the invention may conveniently be prepared by admixing, by conventional mixing techniques, the desired amount of antioxidant and amine in a suitable lubricating oil The selection of the particular base oil and amine, as well as the amounts and ratios of each, depends upon the contemplated application of the lubricant and the presence of other additives Generally, 10 however, the amount of oil-soluble antioxidant employed in the lubricating oil will vary from 0 25 to 10, and usually from 0 25 to 2, weight per cent The tertiary amine will range from 0 01 to 2, and usually from 0 01 to 0 3 preferably from 0 05 to 0 3, weight per cent based on the weight of the final composition The weight ratio of organic oil-soluble antioxidant to amine will generally vary from 5-20 to 1, and 15 usually from 10-20 to 1.

Concentrates of the new additive composition of this invention can be prepared for easier handling and storage of the additive Usually the concentrate will be 10 to 90 % by weight additive composition and from 10 to 90 / by weight lubricating oil diluent Preferably the additive composition comprises 20 to 80 , by 20 weight of the lubricating oil'additive concentrate This concentrate is diluted with additional oil before use.

The lubricating oil which may be used includes a wide variety of hydrocarbon oils such as napthenic base, paraffin base, and mixed base oils Other oils include lubricating oils derived from coal products and synthetic oils, e g alkylene 25 polymers (such as propylene and butylene, and mixtures thereof), alkylene oxidetype polymers (e g alkylene oxide polymers prepared by polymerizing alkylene oxides, such as ethylene oxide and propylene oxide in the presence of water or alcohol, e g ethyl alcohol), carboxylic acid esters (e g those which are prepared by esterifying carboxylic acids, such as adipic acid, azelaic acid, suberic acid, sebacic 30 acid, alkenylsuccinic acid, fumaric acid or maleic acid, with an alcohol such as butyl alcohol, hexyl alcohol, 2-ethylhexyl alcohol or pentaerythritol liquid esters of phosphorus-containing acids such as trialkyl phosphate and tricresyl phosphate, alkylbenzenes, polyphenyls (e g biphenyls and terphenyls), alkylbiphenyl ethers, esters and polymers of silicon, e g tetraethyl silicate, tetraisopropyl silicate, hexa( 4 35 methyl-2-pentyl) disilicate, poly(methyl)siloxane, and poly (methylphenylsiloxane).

The lubricating oils may be used individually or in combinations whenever miscible, or whenever made so by use of mutual solvents The lubricating oils generally have a viscosity which ranges from 50 to 5000 SUS (Saybolt Universal Seconds), and usually from 100 to 1500 SUS at 100 F 40 In addition to the antioxidant, the amine compound and the oil-soluble zinc salt, other additives may be used in the lubricating composition without affecting its high stability and performance over a wide temperature scale One type of additive which may be used is a rust inhibitor The rust inhibitor is used in many types of lubricants to suppress the formation of rust on the surface of metallic parts 45 Typical rust inhibitors include sodium nitrate, alkenylsuccinic acid and derivatives thereof, alkylthioacetic acid and derivatives thereof, polyglycols and derivatives thereof, and alkoxylated amines and derivatives thereof Other types of lubricating additives which may be used are metallic or ashless dispersants and detergents.

Typical of these are the conventional succinimides, succinates, 50 hydrocarbylalkylene polyamines, alkaline earth metal salts of alkylaryl sulfonates, and phenates.

Other types of lubricating oil additives which may be used include antifoam agents (e g silicones, organic copolymers), stabilizers and antistain agents, tackiness agents, antichatter agents, dropping point improvers and antisquawk 55 agents, lubricant color correctors, extreme-pressure agents, odor control agents, detergents, antiwear agents and thickeners.

The presence of the amine in the lubricant composition increases the antioxidation properties of the oil-soluble sulfur-containing antioxidant With this combination, less of the antioxidant is necessary in the lubricant to achieve the 60 desired antioxidation properties If the antioxidant is used at conventional levels, increased oxidation protection is obtained.

The following Example is presented to illustrate the practice of this invention.

1,581,653 EXAMPLE

The combination of the amines with this antioxidant in improving the antioxidation properties of a lubricating oil over the use of either of the components individually is illustrated by the following test The oxidation test uses the resistance of the test sample to oxidation using pure oxygen with a Dornte-type 5 oxygen absorption apparatus (R W Dornte, "Oxidation of White Oils", Industrial and Engineering Chemistry, Vol 28, page 26, 1936) The conditions are an atmosphere of pure oxygen exposed to the test oil maintained at a temperature of 340 F The time required for 100 g of test sample to adsorb 1000 ml of oxygen is observed and reported in the following Table I The test oil is Midcontinent neutral 10 oil containing 6 % of a conventional succinimide dispersant, 0 05 % terephthalic acid, 0 4 %, of a conventional rust inhibitor, and 9 mmols/kg of a zinc dithiophosphate.

TABLE I

Oxidation 15 Antioxidant Tertiary Amine Life/Hrs 1 % sulfurized 6 4 diaparaffin polysulfide " O 1 % tributylamine 7 5 20

Claims (11)

WHAT WE CLAIM IS:-

1 An antioxidant additive composition for a crankcase lubricating oil, the additive composition comprising in admixture:

(I) an oil-soluble antioxidant selected from sulfurized aromatic and alkyl sulfides and polysulfides, sulfurized olefins, sulfurized carboxylic acid 25 esters, and sulfurized ester-olefins, and ( 2) a tertiary amine of the general formula:

(R 2)3 N, or HI-t N R} X 30 wherein each R

2 is independently C 3-C 10 alkyl, phenyl, or phenyl substituted by 1 or 2 alkyl groups of 1-12 carbon atoms, R 4 is alkylene of at least 2 carbon atoms, X is hydrogen or -NA 2 with each A being independently C,-C,8 alkyl, and Het is a carbon chain forming with the N atom a 5 or 6-membered heterocyclic ring, optionally containing in place of one carbon atom an additional O hetero atom 35 2 An additive composition as claimed in Claim I, wherein the amine is a teriary amine represented by the general formula:

(R 2)

3 N wherein each R 2 is C 3-Co alkyl, phenyl or phenyl substituted by I or 2 alkyl groups of 1 to 12 carbon atoms 40 3 An additive composition as claimed in Claim 2, wherein the tertiary amine is tributylamine.

4 An additive composition as claimed in any preceding claim, wherein the antioxidant is a sulfurized wax sulfide or polysulfide.

5 An additive composition as claimed in any preceding claim, wherein the 45 weight ratio of said antioxidant to said amine is 1:0 001-21.

6 A lubricating oil composition comprising an oil of lubricating viscosity and an additive composition as claimed in any one of Claims 1 to 5.

7 A composition as claimed in Claim 6, wherein from 0 25 to 10 weight per cent of the antioxidant and from 0 001 to 5 weight per cent of the amine are present 50 in the composition.

8 A composition as claimed in Claim 6 or 7, and further comprising an oilsoluble zinc salt, said salt being present in an amount of from 2 to 40 millimols of the zinc salt per kilogram of composition.

9 A composition as claimed in Claim 8, wherein the zinc salt is a zinc 55 dihydrocarbyldithiophosphate.

1,581,653 A lubricating oil composition in accordance with Claim 6, substantially as described in the foregoing Example.

11 A concentrate for lubricating oil composition as claimed in Claim 6, comprising from 10 to 90 % by weight of the additive composition and from 90 to 10 %/ by weight of the oil of lubricating viscosity.

HASELTINE, LAKE & CO, Chartered Patent Agents, Hazlitt House, 28, Southhampton Buildings, Chancery Lane, London, WC 2 A IAT.

also Temple Gate House, Temple Gate, Bristol, BSI 6 PT.

and 9, Park Square, Leeds, L 51 2 LH, Yorkshire.

Printed for Her Majesty's Stationery Office, by the Courier Press Leamington Spa 1980 Published by The Patent Office, 25 Southampton Buildings London WC 2 A l AY from which copies may be obtained.

1,581,653