AU706692B2 - Lubricating oil compositions for internal combustion engineshaving silver bearing parts - Google Patents

Description

-Ia- 01 02 03 04 BACKGROUND OF THE INVENTION 06 This invention relates to lubricating oil compositions for 07 use in engines having silver bearings. In a further aspect, 08 the invention relates to the protection of silver bearing 09 parts in internal combustion engines.

11 As is well known, lubricating oils for heavy duty diesel 12 engines require crankcase lubricating oils which are 13 stabilized against oxidation and which limit the formation 14 of engine deposits. In addition, these crankcase lubricating oils must also have a high alkalinity to 16 neutralize acids formed during fuel combustion.

17 18 Many heavy duty railroad and tugboat diesel engines in use 19 in the United States and certain other countries pose an additional lubrication problem, because they have silver- 21 surfaced engine parts, such as silver or silver-plated 22 bearings. While the foregoing properties of oxidation 23 stability, deposit control and alkalinity can be achieved by 24 the use of lubricating oil additives known in the art, many of the resulting oils cause unacceptable corrosion and wear "26 to silver-surfaced diesel engine parts. Silver, or silversurfaced bearing parts, pose a special problem since many of 28 the bearing protection additives which are effective to protect bearings surfaced with other materials, brass, copper-lead, bronze, aluminum, are ineffective to protect 31 silver bearing parts or, for example as in the case of .:32 materials such as zinc dlthiophosphates (commonly used in lubricants to provide lead bearing protection) are 34 deleterious to silver bearings.

01 02 03 04 06 07 08 09 11 12 13 14 16 17 18 19 21 22 23 24 .25 26 28 .32 .329 "31 32 33 34 Typically, lubricating oil compositions for such engines have a TBN of from 5 to 30. This alkalinity is typically achieved by inclusion of a requisite amount of a calcium overbased sulfurized alkylphenate in the composition.

However, the overbased alkylphenate is also detrimental because it imparts undesirable wear to the silver coating on the silver wrist-pin bearings.

At present silver protection is largely provided by the use of lubricants containing chlorinated paraffins or other chlorinated additives. Examples of halogenated additives used to provide silver protection are, for example, described in U.S. Patent Nos. 4,131,551; 4,169,799; 4,171,269; 4,320,016; 4,428,850; and 4,464,276. However, a problem has arisen with respect to the use of halogenated additives in that they are perceived as presenting environmental problems. Thus, there is a need for lubricants which provide silver protection without the inclusion of halogenated additives.

In view of this need the art has already developed certain halogen-free or reduced halogen silver corrosion inhibitorcontaining lubricants. For example, U.S. Patent Nos. 4,764,296 and 4,734,211 disclose a marine and railway diesel engine lubricating oil composition containing certain polyhydroxy esters as silver wear inhibitors. These patents also disclose lubricating oil compositions containing a mixture of these polyhydroxy esters and chlorinated paraffins. U.S. Patent No. 4,820,431 discloses a method for reducing silver wear in marine and railway diesel engines using similar lubricating oil compositions. U.S. Patent No. 4,171,270 discloses lubricating oil compositions containing a sulfurized overbased calcium alkylphenolate and a sulfurized naphthenic base oil-containing composition 01 02 03 04 06 07 08 09 11 12 13 14 16 17 18 19 21 22 23 24 2 26 27 28 29 30 31 :32 e.e333 34 having a sulfur content of from 1 percent to 6 percent by weight. These compositions are also thought to have silver protective properties. U.S. Patent 4,871,465 discloses lubricating oils containing as a silver protectant a sulfurized olefin, sulfurized fatty acid, sulfurized hydroxyaromatic, sulfur containing heterocyclic compounds, organic sulfide or dithiocarbamate and the reaction product of a saturated aliphatic dicarboxylic acid with an optionally substituted aminoguanidine. U.S. Patent No. 2,795,548 teaches that certain borate-glycol complexes were found to give effective lubrication over long periods with very low weight loss of silver bearings. U.S. Patent No. 4,278,553 discloses a railway diesel engine lubricant containing a silver corrosion inhibitor comprising a benzotriazole compound present in concentrations from about 0.5 to 2.0 wt% and U.S. Patent No. 4,285,823 discloses a diesel lubricant composition containing a silver corrosion-inhibiting amount of an N-substituted 5-amino-lH-tetrazole. Commonly assigned U.S. Patent No.

5,244,591 teaches that certain unsaturated carboxylic acid, oleic acid, provides silver bearing protection particularly when used in combination with a small amount of a sulfurized olefin.

A continuing need exists for additives which provide silver protection without presenting potential environmental problems and preferably, which are readily available. As before mentioned, a significant problem in meeting this need is the unpredictability of additive response with respect to silver bearing systems. One simply cannot predict whether a given additive will provide silver bearing protection based on its properties in lubricants for non-silver bearing engines or a general characterization of the additives' properties or function. Thus, for example as previously 01 02 03 04 06 07 08 09 11 12 13 14 16 17 18 19 21 22 23 25 26 27 28 29 30 31 25 :328 30 31 mentioned, zinc dithiophosphates which are widely used to provide wear and oxidation protection, are recognized to be deleterious to the silver bearing parts of engines; see, for example, U.S. Patent No. 4,849,118. It is also well recognized that providing silver bearing protection is not merely a matter of neutralizing engine acid; see, for example, U.S. Patent No. 3,779,920, column 1, lines 20-30 and U.S. Patent No. 4,849,118, column 2, lines 24-35. U.S.

Patent No. 3,933,662 is directed to lubricating compositions which are described as having improved neutralization capacity and rust inhibition by virtue of the incorporation therein of the combination of a polyoxylated compound and an alkaline earth metal carbonate. The '662 patent is more specifically concerned with providing rust protection for ferrous metals; see column 2, lines 43-45, and all of the lubricating compositions described in the examples contain a zinc alkyldithiophosphate.

Polyoxyalkylene compounds have been used as lubricating oil additives in compositions for use in the upper cylinder chamber of marine diesel cylinder engines of the crosshead type. For example, U.S. Patent No. 4,402,845 discloses lubricant compositions having a TBN of from 50 to 100 which are used in marine diesel cylinder engines of the crosshead type and which contain a polyethylene glycol compound of the formula: R- CH 2 0 (CH 2 CH20) H wherein n ranges from 7 to 40 and R is an alkyl group containing from 11 to 15 carbon atoms. These compounds are disclosed as improving the spreadability of marine diesel engine cylinder oils after injection of the oil into the interior of the cylinder chamber. In column 2, line 40 of 01 02 03 04 06 07 08 09 11 12 13 14 .16 1 **1 18 .'19 "21 22 **23 23 24 25 25 26 27 .28 *29 32 33 the patent, TERGITOL® 15-S-20 is cited as a particularly preferred compound. Similarly, U.S. Patent No. 4,479,882 discloses a process for improving the spreadability of a lubricating oil composition having a TBN of from 50 to 100 for use in a marine diesel engine of the crosshead type by incorporating therein a polyalkoxylated phenoxy compound of the formula: R--O

(CH

2

CH

2 0)nH wherein R is an aliphatic hydrocarbyl group having from 5 to 70 carbon atoms and n ranges from 14 to Two cycle railroad diesel engines and the similar type engines used in some tugboats should also be contrasted with the large marine diesel engines used in freighters or other large ships. Both railroad type diesel engines and the large marine diesel engines are heavy duty diesel engines, the internal components and operating conditions of these engines are quite different. Two cycle railroad diesel engines are characterized by and distinguished from large marine diesel engines by many factors including silver wrist-pin bearings. Silver coatings are used in the wristpin bearings because this metal imparts superior advantages in wear resistance to the bearing when operated under such extreme conditions. In contrast, large marine engines do not require silver coating of any of their internal parts.

U.S. Patent No. 5,397,486, which issued on March 14, 1995, hereby incorporated by reference in its entirety, teaches that compound having the formulas: 01 02 03 04 06 07 08 09 11 12 13 14 16 :EI17 o 8 ":19 :..21 22 23 24 25 26 27 28 S":29 31 32 33 34

CH

2

OH

RXCHCHCHH; or R-X-CH R-X- R-X-CH2CHCH2OH; or R-X-CH

CHOH

wherein R is a hydrocarbyl radical having from about 4 to about 50 carbon atoms; R 1 is independently an alkylene group of from about 2 to about 6 carbon atoms; X is selected from the group consisting of oxygen, sulfur and nitrogen, preferably oxygen; n is an integer from 1 to about preferably 10 to 20; m is 1 when X is oxygen or sulfur and is 1 or 2 when X is nitrogen; with the proviso that when R 1 is ethylene, the lubricating oil should be a single grade oil and adducts of the compounds of formula B or C with alkylene oxide of from 2 to 6 carbon atoms or glycidol provide silver bearing protection in lubricating oils containing the requisite amount of an overbased calcium sulfurized alkylphenate to provide a TBN of about 5 to about SUMMARY OF THE INVENTION It has now been discovered that certain acyloxy derivatives of certain of the compounds described in U.S. Patent No. 5,397,486 are effective to provide silver bearing protection in lubricating oil.

In one embodiment the present invention provides an essentially chlorine-free and zinc dithiophosphate-free lubricating composition having a TBN of about 5 to comprising a major amount of an oil of lubricating viscosity and an amount of a silver protectant which is effective to inhibit or reduce silver wear or deterioration in internal combustion engines having silver bearing parts and wherein 01 said silver protectant is selected from the group of 02 compounds having the formula I herein below and mixtures 03 thereof: 04 0 06

II

07 R-CO-R'O) H (I) 08 09 wherein R is a hydrocarbyl radical having about from 4 to carbon atoms; R 1 is independently selected from alkylenes 11 having 2 to 8 carbon atoms; and n is a whole integer of 12 about from 1 to 30, preferably 8 to 20 and more preferably to 13 14 In a further embodiment, the invention provides a method for 16 reducing silver bearing wear in internal combustion engines 17 having silver bearing parts via the use of the present 18 lubricating composition.

19 In another embodiment, the invention provides an additive 21 package or concentrate having a TBN of 90 to 120 containing 22 a small amount, generally under 20% by wt., of a diluent oil 2 and a silver protectant selected from the group of the 24 compounds of formula I and mixtures thereof, and wherein said silver protectant and the additive providing the TBN 26 are in a relative weight ratio such that the additive :27 package may be admixed with an oil of lubricating viscosity 28 to provide a lubricant having a TBN of 5 to 30 and an amount o 29 f said silver protectant effective to provide silver 29 bearing protection.

31 32 33 34 -8- 01 DETAILED DESCRIPTION OF THE INVENTION 02 03 As above noted the compositions of the present invention 04 contain an amount of a compound or mixture of compounds, according to Formula I effective to provide silver 06 protection for engines having silver bearings. In general, 07 two theories are advanced as to why a material provides 08 silver protection; the material may act as a lubricity 09 agent or it may act as a silver pacifier provides protection by entering into a chemical reaction with silver 11 to form a bearing surface less susceptible to wear).

12 However one cannot predict that a material which provides 13 protection as a lubricating -agent or pacifier with some 14 other bearing material will provide protection for silver bearings. The term silver protectant is intended to refer 16 to a material which provides silver bearing protection 17 regardless of the particular mechanism involved. As well as 18 providing silver wear protection the compounds of formula I 19 also have excellent oil solubility which readily facilitates their use in lubricating oil compositions.

21 22 Preferably, R is a saturated or unsaturated aliphatic radical having at least eight carbon atoms more preferably 24 an alkyl or alkenyl. Preferably, the R 1 substituent has 2 f 25 to 6 carbon atoms and more preferably has 2 to 4 carbons The preferred compounds of formula I have at least one .27 preferred substituent and more preferably have a combination 28 of preferred substituents. Typically best results in terms of silver protection are obtained using the compounds of formula I wherein R is an aliphatic hydrocarbon having 14 to 31 30 carbon atoms, R 1 is an alkylene having 2 to 4 carbon :32 atoms and n is 2 to 20. In general, the compounds of 33 formula I, wherein the RC(O)O- moiety is a fatty acid 34 -9- 01 02 03 04 06 07 08 09 11 12 13 14 16 17 18 19 21 22 23 24 25 S26 27 28 29 31 32 33 34 a.

radical, provide excellent silver wear protection and readily provided commercially in large quantities.

The compounds of formula I are generally known compounds and can be prepared by using or adapting known procedures. In many instances, the compounds of formula I can be readily obtained in large quantities from commercial sources. In many instances, it will be more convenient to use a mixture of compounds in the present invention because the compounds or starting materials therefor, are more economically provided as mixtures. For example, commercial oleic acid, used to prepare the oleate of formula I, will also typically contain minor amounts of other fatty acids. In general, the compounds of formula I can be obtained by reacting the desired R carboxylic acid RCOOH) with an alkali metal hydroxide sodium hydroxide) and the desired alkylene oxide. The n values can be controlled by adjusting the ratio of alkylene oxide to acid. In general, it is preferred to conduct the reaction step wise and remove the byproduct glycol-water by distillation after each step or conduct the reaction as a continuous process with continuous distillation off of the byproduct.

The compounds of formula I can also be prepared by reacting the corresponding poly(oxyalkylene)diol, having terminal hydroxy groups, HO- (RI0)H, with the desired RCOOH acid. The diols can be produced using similar procedure as used to produce hydrocarbyl poly(oxyalkylene) alcohols, for example the addition of lower alkylene oxides, such as oxirane, ethylene oxide, propylene oxide, the butylene oxides, or the pentylene oxides to the hydroxy compound under polymerization conditions, and adjusting the ratio of reactants to provide the diol as the primary product.

Additional information regarding the production and 01 02 03 04 06 07 08 09 11 12 13 14 16 17 18 19 21 22 23 24 26 27 re 28 29 oleo 31 32 33 S 34 34 properties of these polymers are for example disclosed in U.S. Patent Nos. 2,841,479 and 2,782,240, and Kirk-Othmer's "Encyclopedia of Chemical Technology", vol. 19, p. 507, and my co-pending application Serial No. 08/099,632, all of which are hereby incorporated by reference in their entirety.

In order to be useful as a lubricating oil additive, the additive must be sufficiently lubricating oil soluble and compatible in the fully formulated composition. That is to say that the compound I shall be sufficiently soluble in a formulated lubricating oil composition to provide a wearinhibiting amount of the compound in the oil which amount does not precipitate or cause other components in the composition to precipitate from the composition under ambient conditions about 20 0 Preferably, the silver protectant is soluble and compatible to a level of at least 0.1 weight percent in the formulated composition and more preferably to a level of at least 0.3 weight percent for a period of at least about one month and preferably for a period of at least about six months. As noted above, one of the advantages of the compounds of formula I is that in general such compounds have excellent oil solubility. Thus, this will generally not be a concern however, in any event methods for determining oil solubility and compatibility for these compositions are well known in the art and can be determined by the exercise of routine skill. For example, precipitation from a formulated lubricating oil composition at ambient conditions can be measured by either actual precipitation from the oil composition or the formation of a "cloudy" solution which evidences formation of insoluble wax particles. As noted above, the compounds of formula I are oil soluble single grade and multi-grade oils. It has been further found that the solubility of such compounds are -11- 01 further enhanced when the R hydrocarbyl radical is attached 02 to the carboxy group by a branched carbon atom.

03 04 Definitions 06 As used herein the following terms have the following 07 meanings unless expressly stated to the contrary: 08 09 The term "essentially chlorine-free" refers to the absence of chlorinated compounds to provide silver protection and 11 the absence of any amounts of chlorinated compounds which 12 could be considered to have an adverse effect on the 13 environment.

14 The term "zinc dithiophosphate-free" refers to the absence 16 of zinc dithiophosphates such as are conventionally used to 17 provide wear protection for other bearing materials, notably 18 lead, but are deleterious to silver bearing materials. The 19 term "TBN" refers to total base number and is a measure of the ability of the lubricant to neutralize acid as 21 determined by the procedure described in ASTM D2896-85, and 22 in general terms, is the neutralization capacity of one gram 23 of the lubricating composition expressed as a number equal .24 to the mg of potassium hydroxide providing the equivalent 25 neutralization. Thus, a TBN of 10 means that one gram of 26 the composition has a neutralization capacity equal to 10 mg 27 of potassium hydroxide.

28 29 The term "hydrocarbyl" refers to an organic radical composed 30 of carbon and hydrogen which may be aliphatic, alicyclic, 31 aromatic or combinations thereof, aralkyl. The 32 hydrocarbyl radical may have a straight- or branched- chain 33 of carbon atoms and may be saturated or unsaturated.

34 Q.\OPER\AXD\43384-96 116- 26/4/99 11A Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

0

S

i00 0* -12- 01 02 03 04 06 07 08 09 11 12 13 14 16 17 18 19 21 22 23 24 25 26 30 31 32 28 32 33 34 *0e0 Preferably the hydrocarbyl radical is free of acetylenic unsaturation.

Lubricating Compositions The lubricating compositions can be conveniently prepared by simple blending or mixing of the compounds of formula I with an oil of lubricating viscosity. The compounds of formula

I

may also be preblended as a concentrate or package with various other additives in the appropriate ratios to facilitate blending of a lubricating composition containing the desired concentration of additives. Typically the lubricating composition of the invention contains about from 0.8 to 3 wt%, preferably about from 0.85 to 2 wt% based on the total weight of the composition, of a silver protectant selected from the lubricating oil soluble compounds of formula I and mixtures thereof. More preferably, the lubricating composition contains about from 0.9 to 1.5 wt% of the said silver protectant.

The lubricating composition has a TEN of about 5 to preferably 15 to 25. This is a measure of the alkalinity or neutralizing capacity and is typically provided by the addition of basic detergents or overbased materials. The function of the basic component is to neutralize acid oxidation products, such as sulfuric acid in the case of diesel fuels. Various types of overbased materials can be used, such as, for example, sulfurized and/or carbonated phenates, salicylates, and sulfonates. Various overbased phenates are described in U.S. Patent Nos. 2,680,096; 3,036,971; 3,336,224; 3,437,595; 3,801,507; and 4,251,379.

Various overbased sulfonates are described in U.S. Patent Nos. 2,616,904; 2,626,207; 2,767,209; 3,126,340; 3,524,814; and 3,609,076.

-13- 01 02 03 04 06 07 08 09 11 12 13 14 16 17 18 19 21 22 23 24 S26 27 28 29 30 31 32 -33 34 :0*0.

The present lubricating oil compositions will also typically contain, in addition to the silver protectant, various other additives used to impart desirable properties to lubricating oil compositions used for internal combustion engines having silver bearing parts. Thus, the lubricating composition will typically contain one or more of the following additives: detergents or detergent-dispersant, dispersants, ashless dispersants, overbased detergents, oxidation inhibitors and most preferably will contain a combination of such additives and may contain other additives designed to improve the properties of lubricating oil compositions. Such additives are generally commercially available and can be made by known procedures; however, if desired, additional details regarding the manufacture of, for example, overbased calcium sulfurized alkylphenate detergents and succinimate dispersants can be had by references to my co-pending application 08/099,632, hereby incorporated by reference in its entirety and the references cited therein.

The base oil can be a mineral, synthetic or natural oil (vegetable or animal-derived oils), but from an economic standpoint, is preferably a mineral oil. Solvent refined and hydrorefined base oils may also be used. Frequently a mixture of different oils is used as the base oil. The individual oils typically have viscosities of about from 4 centistokes to 40 centistokes at 100 0 C, and preferably 8 to 14 centistokes at 1000C. The base oil or mixture of base oils are typically preselected so that the final lubricating oil, containing the various additives, including the silver protectant, has a viscosity at 1000C of 4 to 22 centistokes, preferably 10 to 17 centistokes and more preferably 13 to 17 centistokes.

-14- 01 02 03 04 06 07 08 09 11 12 13 14 16 17 18 19 21 22 23 24 25 26 28 S29 30 31 32 33 34 Detergent-dispersant additives are designed to keep sludge, carbon and products derived from the partial oxidation of the diesel fuel or base oil, suspended in the base oil.

Suitable detergent-dispersants include phenate and sulfonate metallic detergents, for example, calcium phenate or sulfonate. Various ashless dispersants are described in U.S. Patent Nos. 3,172,892; 3,219,666; 3,282,955; and 3,361,673. Succinimide and succinate ester ashless dispersants are typically prepared by the reaction of polyisobutenyl succinic anhydride with a polyalkylene polyamine or polyol, respectively.

The lubricating composition may also optionally contain viscosity index improvers ("VI improvers") to regulate viscosity, reduce viscosity changes produced by temperature changes, multi-grade oils. However, care must be taken in using VI improvers because the VI improver may be deleterious to silver bearings. Thus, it may be desirable to increase the amount of silver protectant or add additional corrosion inhibitors where VI improvers are used.

The VI improver may be a non-dispersant viscosity improver or a dispersant viscosity improver, which acts as a dispersant as well as regulating viscosity. Examples of non-dispersant VI improvers include various oil-soluble polymers typically having molecular weights in the range of 20,000 to 1,000,000 and include alkyl methacrylate polymers, ethylene-propylene copolymers, mixed alkylmethylacrylateethylene-propylene polymers, isobutylene polymers, hydrogenated styrene-diene polymers, and the like.

Dispersant VI improvers are also typically polymers, but which incorporate some degree of nitrogen functionality which imparts dispersancy to the molecular, in addition to the viscosity, regulating effect. Examples of dispersant VI improvers include styrene-based polyesters incorporating a 01 02 03 04 06 07 08 09 11 12 13 14 16 17 18 19 21 22 23 S.24 25 26 27 28 29 S30 o 30 31 32 33 34 ftefft t f succinimide or substituted succinimide N-(3'-morpholin-4-ylpropyl) succinimide] unit; mixed alkyl methacrylate-vinyl pyrrolidone polymers; aminated ethylenepropylene polymers; and the like. Compatible mixtures of VI improvers can also be used. Where a VI improver is used, it may be desirable to separately blend the VI improver with the base oil rather than part of a package with other additives. The newer synthetic or poly alpha olefin base oils may also afford multigrade performance or reduce the amount of VI improver required.

With the possible exception of the inclusion of a viscosity index improver, typically, best overall results in terms of affording the properties desired in a modern lubricating oil composition for internal combustion engines having silver bearings are obtained wherein the lubricating composition contains a compatible combination of additives representing one or more and preferably each of the above classes of additives in effective amounts as well as the silver protectant of the present invention and a sufficient amount of a neutral and/or overbased detergent, preferable both, sufficient to provide the desired neutralization capacity (typically expressed as TBN).

The lubricating composition may also contain small amounts of supplemental corrosion inhibitors without harming the properties of the composition and perhaps providing some additional benefit and as above noted, may be desirable when VI improvers are used. The corrosion inhibitor should not, of course, be a corrosion inhibitor such as, for example, zinc dithiophosphate which is itself corrosive to silver bearings. Where supplemental corrosion inhibitors are used, they are generally used in amounts of about from 0.02 to 1 wt% of the lubricating composition. Additional amounts of -16- 01 supplemental corrosion inhibitor may not be harmful but 02 generally are not beneficial. Thus, for example, the 03 composition may contain, based on the total weight of 04 lubricating composition, about 0.02 to 0.08 wt% of a sulfurized olefin corrosion inhibitor (for example, 06 cosulfurized alkenyl ester/alpha olefins) and/or up to about 07 1% by wt., preferably about from 0.5 to 0.8 wt% of 08 terephthalic acid or a salt or derivative thereof.

A

09 variety of sulfurized olefin corrosion inhibitors, as well as other corrosion inhibitors, are described in the 11 published literature and are available commercially. The 12 cosulfurized alkenyl ester/alpha olefin additives, for 13 example, typically prepared by reacting a mixture of the 14 desired olefins, typically

C

12

-C

20 linear olefins, and unsaturated esters, oleate, linoleate, with sulfur at 16 moderate to elevated temperatures via known procedures.

17 Various sulfurized olefin corrosion inhibitors or wear 18 inhibitors are described in U.S. Patent Nos. 4,053,427; 19 4,119,549 and 4,240,549. In the case of terephthalic acid corrosion inhibitors, either a solubilized form of the acid 21 is used, or more conveniently, when the additive package 22 includes a succinimide dispersant, the acid is simply 23 solubilized by reaction with the succinimide dispersant to 24 form an oil-soluble salt of terephthalic acid.

26 As above noted, the present invention also provides an 27 additive package or concentrate which may be added to an oil 28 of lubricating viscosity either as the sole additive or in 29 combination with other additives. (Generally, the additive 30 package will not contain a viscosity index improver because 31 even where desired the viscosity index improver is generally 32 added to the base oil by the lubricant formulator.) Thus, a 33 preferred additive concentrate contains about from 5 to 34 14 wt% more preferably 6 to 10 wt% of the silver protectant O0oQ -17- 01 02 03 04 06 07 08 09 11 12 13 14 16 17 18 19 21 22 23 .24 24 26 :27 28 29 30 31 32 33 34 and sufficient basic material (typically overbased detergents) to provide the concentrate with a TBN of about from 60 to 180 preferably 60 to 120; and about 1 to 10 wt% preferably 2 to 6 wt% of a diluent oil. With the general exception of the VI improver, the concentrate will frequently also contain various other additives considered desirable for the intended use and generally will contain about from 30 to 60 wt% of an ashless dispersant and frequently will also contain neutral or slightly alkaline detergent in addition to the overbased detergent. The amount of overbased detergent needed to provide the requisite TBN will, of course, vary with the TBN of the overbased detergent but typically will be 20 to 80 wt% of the concentrate.

The various additive materials or classes of materials described above are known materials and can be prepared by known procedures or obvious modifications thereof and frequently are readily available from commercial sources.

A further understanding of the invention can be had from the following nonlimiting examples.

EXAMPLE 1 SILVER WEAR EVALUATION The lubricating oil compositions identified in Table 1 hereinbelow were evaluated for silver wear protection by the standard silver bearing wear test EMD 2-567, also commonly known as the "2-Holer Test" used to assess the distress rating of a silver-plated wrist pin after 25 hours of operation.

-18- 01 02 03 04 06 07 08 09 11 12 13 14 16 17 18 19 20 23 24 26 :27 28 29 30 31 32 33 34 A test formulation was prepared by blending 0.6 wt% of an ethoxylated oleate ester having an average of about ten exthoxy units per molecule, e.g.

CH

3 (CH) CH=CH (CH 2 C 0-CH 2 0) 1H, (sold under the tradename Ethofat 10/20' M by AKZO Chemical Co. Inc. of McCook, Illinois, USA) with a formulated 20W40 lubricating oil containing 4.0 wt% of a viscosity index improver and the requisite amount of a sulfurized overbased calcium phenate needed to provide a TBN of 17 and small amounts of other additives for example as ashless dispersant. The comparison formulation was the identical to the test formulation but without the ethoxylated oleate ester silver protectant.

In the 2-holer test, the normally protected silver bushing of the wrist pin bushing assembly is replaced with an unprotected silver bushing. (Normally, the bushing is protected with a thin lead flashing to protect the silver surface from corrosion and high friction during break in.) Removal of the lead flashing greatly increases the test severity. The test engine used in this evaluation had a D-1 type assembly. (The D-1 configuration uses three chromeplated and one ferrite-filled cast iron. compression rings above the piston pin with one hooked scraper-type oil control ring and one ventilated cast iron ring below the pin. The nominal compression ratio was 20:1.) The engine is kept in newly built condition by periodic replacement of the liners, pistons, rings, carriers, thrust washers, cam bearings, rods, rod bearings, main bearings, and reconditioned heads with new valves and rebuilt injectors.

For each silver wear test, the engine is thoroughly cleaned with a commercial petroleum-based solvent and the wrist pin -19- 01 02 03 04 06 07 08 09 11 12 13 14 16 17 18 19 20 21 22 23 24 25 26 o 27 o*-o 28 29 30 31 32 33 34 replaced with a new piston pin and unprotected unleaded) silver-plated pin bearings. Prior to conducting the silver wear test, the engine is given a full 9-hour and 20-minute EMD-type break-in. Following the break-in, the crankcase and air boxes are inspected for signs of bearing failure before the test phase is initiated. While under test, the engine is held at 835 rpm, 91 1.0 lbs./hr. fuel rate and 6.8 inches of Hg air box pressure by a distributed digital process control computer. The water and oil inlet temperatures are controlled at 180° 2 0 F and 210° 2 0

F,

respectively. The crankcase and all oil lines are flushed with test oil, and the crankcase is charged to its full capacity of 45 U.S. gallons. The fuel for these tests contained 0.1% sulfur and the cetane number is a nominal 47-50 No. 2 diesel. Each test is conducted using identical test conditions. The pin bearings were weighed before and after the test. The piston pin diameters and in-carrier clearances were taken before and after the test.

At the conclusion of the test, the pin bearings were removed and rated according to the EMD distress demerit procedure which measures and assigns demerits based on the amount of silver which has been displaced from the bearings into the oil grooves. An average of 30 or less demerits with neither of the two bearings having 40 or more demerits is considered a passing result. The engine using the comparison lubricating oil composition had a right bearing demerit rating of 8 and a left bearing demerit rating of 440 and actually failed before completion of the test. In contrast to this engine using the lubricating oil formulation containing the compound of formula I had a bearing demerit rating of 9 for both the right and left bearings and passed the test.

01 02 03 04 06 07 08 09 11 12 13 14 16 17 18 1 1920 21 21 22 23 24 26 27 28 29 31 32 33 34 Obviously, many modifications of the invention described hereinabove and below can be made without departing from the essence and scope thereof.

-21- 01 THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 02 03 1. A method for reducing silver bearing wear in internal 04 combustion engines having silver bearings which comprises lubricating said engines with an essentially chlorine- 06 free and zinc dithiophosphate-free lubricating 07 composition having a TBN of about from 5 to 08 consisting essentially of a major amount of an oil or 09 mixture of oils of lubricating viscosity and an amount effective to inhibit or reduce wear or deterioration of 11 said silver bearings of a silver protectant selected from 12 the group of oil soluble compounds having the formula: 13 0 14 II R-CO-(RI 0O) H 17 wherein R is a hydrocarbyl radical having about from 4 18 to 50 carbon atoms; R 1 is independently selected from .19 the group of alkylenes having 2 to 8 carbon atoms, and n is a whole integer of from 1 to about 21 22 and mixtures thereof.

:.23 24 The method of Claim 1 wherein R is an aliphatic radical 25 26" having at least 8 carbon atoms.

26 27 2 3. The method of Claim 2 wherein R has from 14 to 30 carbon *29: atoms.

4. The method of Claim 1 wherein said composition has a TBN of about from 10 through 33 34

Claims (9)

1. 5. The method of Claim 1 wherein R is alkyl or alkenyl having 8 through 50 carbon atoms.
2. 6. The method of Claim 5 wherein R has 14 to 30 carbon atoms.
3. 7. The method of Claim 1 wherein n is a whole integer of from 8 to
4. 8. The method of Claim 1 wherein R 1 has 2 through 4 carbon atoms.
5. 9. The method of Claim 8 wherein R is alkyl or alkenyl having 14 to 30 carbon atoms.
6. 10. The method of Claim 9 wherein RC(0)O- is oleoyloxy.
7. 11. The method of Claim 10 wherein R 1 has 2 through 4 carbon atoms and n is a whole integer of from 8 to Q. .OPERLAXD'43384 96.116 26/4/99 -23
8. 12. A method for reducing wear substantially as hereinbefore described with reference to the Examples.
9. 13. Lubricating oil compositions substantially as herein defined with reference to the Examples. DATED this 26th day of April 1999. CHEVRON CHEMICAL COMPANY by DAVIES COLLISON CAVE Patent Attorneys for the Applicant U. U S. 9* 4 S *fl* en. S S c a S Q* I 01 02 03 04 06 07 08 09 11 12 14 *":16 17 18 19 21 **22 22 ***23 24 26 27 28 29 31 32 33 34 ABSTRACT OF THE DISCLOSURE Lubrication of internal combustion engines having silver bearing parts with essentially chlorine-free and zinc dithiophosphate-free lubricating compositions having a TBN of about 5 to 30 certain silver bearing protecting acyloxy polyalkoxy alcohols. An additive concentrate for the lubricating compositions is also disclosed. PLORON1773