DE69518673T2 - Dispersant for lubricating oil - Google Patents

Description

This invention relates to new and particularly useful dispersants that can be used as additives for natural and synthetic lubricating oils. More particularly, this invention relates to novel dispersant compositions that have reduced reactivity with fluoroelastomers while providing effective dispersing properties, particularly for motor oils for spark-ignition passenger car engines or diesel-powered trucks.

A constant problem in lubrication technology is to provide lubricant compositions that meet the requirements set by original equipment manufacturers. One such requirement is that the lubricant pass one or more fluoroelastomer degradation tests under well-specified laboratory conditions. It is an economic reality that a lubricant that fails the respective test or tests is unlikely to be accepted in the marketplace. Standard test procedures for evaluating the compatibility of lubricant compositions with fluoroelastomers include the VW PV 3334 Seal Test and the CCMC Viton Seal Test (CEC L-39-T-87 Oil/Elastomer Compatibility Test).

More recently, an even more stringent fluoroelastomer test procedure has been developed, namely the VW PV 3344 seal test. This test is so stringent that several commercially available, high-quality engine oils from various manufacturers have failed it.

Therefore, there is a need for a dispersant that meets at least one of the above standard test methods fluoroelastomers less. At the same time, it is important that the product is effective enough as a dispersant to meet various requirements in terms of sludge, varnish and wear control.

This invention effectively and efficiently meets the above requirement. The dispersant compositions of the invention meet these requirements because they have little attack on fluoroelastomers and pass all or most of one or more of the above test methods. In addition, the dispersants enable highly effective control of sludge, varnish and wear during operation of various types of engines.

According to the invention, an oil-soluble dispersant composition is provided comprising

a) an oil-soluble product prepared by reacting aminoguanidine with a long-chain alkyl or alkenyl succinic acid acylating agent in a molar ratio of 0.4 to 1.3 moles (preferably 0.8 to 1.3 moles) of aminoguanidine and/or a basic salt thereof per mole of the acylating agent, and

b) an oil-soluble product prepared by reacting (1) an acyclic hydrocarbyl succinic acylating agent and (ii) an alkylene polyamine having an average of 3 to 6 nitrogen atoms (and preferably an average of 4 to 5 nitrogen atoms) per molecule in a molar ratio of 1.6 to 2 (preferably 1.8 to 2) moles of (i) per mole of (ii) to form a succinimide, and heating the succinimide thus formed simultaneously or in any order and at a temperature in the range of 150 to 180ºC with (iii) at least one dicarboxylic acid acylating agent having less than 20 carbon atoms in the molecule and (iv) at least one boron compound to produce a product having (1) a total base number in the range of 33 to 45 mg KOH per gram of product (as active ingredient, ie excluding the weight of any solvent or diluent associated with said product) and (2) a boron content in the range of 1.0 to 1.4% by weight (again excluding the weight of any solvent and/or diluent associated with said product),

where a) and b) are present in such ratios that for every 0.7 to 1.8 parts by weight of nitrogen (preferably 0.8 to 1.7 parts by weight of nitrogen) from a) there are 0.3 to 1.5 parts by weight of nitrogen (and preferably 0.4 to 1.4 parts by weight of nitrogen) from b).

A further embodiment of this invention is a composition comprising 1 to 99 wt.% of at least one oil of lubricating viscosity and 99 to 1 wt.% of a combination of the above components a) and b) in the stated ratio.

Another embodiment is an additive concentrate formulated as a crankcase lubricating oil additive (also known as a DI package) comprising the above components a) and b) in the ratio indicated and c) at least one oil-soluble metal dihydrocarbyl dithiophosphate (preferably one or more anti-wear or extreme pressure agents made from zinc dialkyl dithiophosphate); d) at least one alkali or alkaline earth metal containing detergent (e.g. a Alkali or alkaline earth metal sulfonate, carboxylate, salicylate or sulfurized alkylphenate or a combination of two or more such detergents) and e) one or more inhibitors selected from oxidation inhibitor(s), foam inhibitor(s), rust inhibitor(s), corrosion inhibitor(s) and friction inhibitor(s), wherein components a), b), c), d) and e) are present in the additive concentrate in such ratios that mixing a minor portion of the additive concentrate into a base oil (e.g. in a concentration in the range of 3.2 to 16.1% by weight based on the active ingredients) provides an oil mixture containing a dispersing amount of a) plus b) in the above ratios, an antiwear amount of c), a detergent amount of d) and an inhibitory amount of each selected inhibitor. On an active ingredient basis, a minor dispersant amount of a) plus b) in the finished lubricating oil is typically in the range of 2 to 5.5 wt%, provided that the amount of nitrogen from b) in the finished lubricating oil does not exceed 0.042 wt%. Similarly, a minor antiwear amount of c) in the finished lubricating oil is typically in the range of 0.5 to 1.25 wt%. When the wear inhibitor is in the form of a phosphorus-containing product, a minor antiwear amount typically equates to a phosphorus content in the finished lubricating oil in the range of 0.04 to 0.12 wt% phosphorus. Likewise, a minor detergent amount of d) in the finished lubricating oil is typically in the range of 0.5 to 3.5 wt.%, a minor oxidation-inhibiting amount of an oxidation inhibitor in the finished lubricating oil is typically in the range of 0.2 to 3 wt.%, a minor foam-inhibiting amount of a foam inhibitor in the finished lubricating oil is typically in the range of 0.0002 to 0.001 wt.%, a minor rust-inhibiting amount of a rust inhibitor in the finished lubricating oil is typically in the range of 0.01 to 0.4 wt.%, a minor corrosion-inhibiting amount in the finished lubricating oil is typically in the range of 0.01 to 0.4 wt.%, and a minor friction-inhibiting amount of a friction inhibitor in the finished lubricating oil is typically in the range of 0.02 to 2 wt.%. In each case, the respective components a), b), c) and d) and each of the selected components e) may be a single component or a mixture of two or more of the specified component type.

A further embodiment provides a finished lubricating oil composition comprising a major amount of at least one oil of lubricating viscosity, a minor dispersing amount of a) and b) in the ratio given above, a minor antiwear amount of c), a minor detergent amount of d) and at least one inhibitor of e), e.g., optionally but preferably, a minor oxidation inhibiting amount of at least one oxidation inhibitor, optionally but preferably, a minor antifoaming amount of a foam inhibitor, optionally a minor antifriction amount of a friction inhibitor, optionally a minor rust inhibiting amount of a rust inhibitor and optionally a minor corrosion inhibiting amount of a corrosion inhibitor. The finished lubricating oil composition preferably also comprises a minor viscosity improving amount of at least one viscosity index improver. Accordingly, this invention provides lubricant compositions comprising oil of lubricating viscosity and one or more, preferably all, of the following components: viscosity index improver, metal dialkyldithiophosphate (most preferably zinc dialkyldithiophosphate), an alkali or alkaline earth metal detergent (preferably sulfonate, sulfurized phenate and/or salicylate), an antioxidant (preferably a phenol, aromatic amine, sulfurized olefin or copper-based agent) and an antifoam agent (preferably silicone-based). Other typical additive components may also be present. For further details, see US-A-5,137,980.

Another embodiment involves the use of components a) and b) in the ratio given above in a minor amount in oil of lubricating viscosity to impart dispersibility and to minimize degradation of fluoroelastomers that come into contact with the oil either during additive qualification testing or during use under actual operating conditions.

In any of the embodiments described above, it is preferred, but not required, that component a) is a borated component, i.e. a product thereof is heated with a boron compound or other suitable boron source at a sufficiently high temperature to produce a product having a boron content in the range of up to about 1% by weight, excluding the weight of any solvent and/or diluent associated with the product.

These and other embodiments of this invention will be understood from the following description and the appended claims.

Base oils

The base oils used to prepare the compositions of the invention may be natural or synthetic oils of lubricating viscosity or suitable mixtures thereof. Thus, the base oils may be hydrocarbon oils derived from petroleum (or tar sands, coal, shale, etc.). The base oils may also be or contain vegetable oils of suitable viscosity, such as rapeseed oil, etc. Synthetic oils may also be used, such as hydrogenated polyolefin oils, poly-α-olefins (e.g. hydrogenated or unhydrogenated α-olefin oligomers such as hydrogenated poly-1-decene), alkyl esters of dicarboxylic acids, complex esters of dicarboxylic acid, polyglycol and alcohol, etc. Mixtures of mineral, vegetable and/or synthetic oils in any suitable proportions may also be used.

In most cases, the base oil is preferably a petroleum-derived mineral oil of a type or viscosity suitable for use in the manufacture of a passenger car engine oil, a heavy-duty diesel engine oil or a drive train lubricant.

Component a)

For convenience, the term "AG dispersant" is used to refer to a product prepared by reacting aminoguanidine or a basic salt thereof with a hydrocarbyl-substituted succinic acid or anhydride in a molar ratio of 0.4 to 1.3 moles of the aminoguanidine or basic salt thereof per mole of the succinic acid or anhydride compound. Likewise, the term "borated AG dispersant" is used to refer to a product prepared in two steps, namely (i) by reacting aminoguanidine or a basic salt thereof with a hydrocarbyl-substituted succinic acid or anhydride in a molar ratio of 0.4 to 1.3 moles of the aminoguanidine or basic salt thereof per mole of the succinic acid or anhydride compound. the succinic acid or succinic anhydride compound, and (ii) boronizing the product thus prepared.

To prepare the AG dispersant, a mixture of an aliphatic hydrocarbyl substituted succinic acid derivative (acid, anhydride, lower alkyl ester or acyl halide) and aminoguanidine or a basic salt thereof are heated, preferably under an inert atmosphere, at a temperature in the range of 80 to 200°C, preferably in the range of 140 to 200°C, with temperatures in the range of 160 to 170°C being most preferred. The reaction can be carried out in the presence or absence of a solvent or reaction diluent. When using alkenylsuccinic acylating agents in which the alkenyl substituent is derived from a polyolefin of lower molecular weight (e.g., GPC number average molecular weight of 1,300), the acylation reaction is preferably carried out without a reaction diluent and a diluent such as a mineral oil is added to the reaction product only after its preparation. For alkenylsuccinic acylating agents in which the alkenyl substituent is derived from a polyolefin of slightly higher molecular weight (e.g., GPC number average molecular weight of 2,100), the reaction should be carried out in a suitable diluent such as a process oil or similar. Reaction times are typically in the range of 1 to 4 hours. Suitable inert atmospheres include nitrogen, argon, krypton, neon, etc. As stated above, the present invention requires the use of a product prepared using from 0.4 to 1.3 moles of aminoguanidine or a basic salt thereof per mole of the aliphatic hydrocarbyl-substituted succinic acid derivative.

To prepare a borated AG dispersant, the AG dispersant prepared as described above is heated in combination with a suitable boron-containing material so that the resulting product contains up to about 1% boron by weight (excluding the weight of any diluent or solvent associated with the product). Temperatures in the range of about 80 to 200°C are generally sufficient for a boration reaction. Suitable methods for carrying out the boration are well known to those skilled in the art. In this connection, reference is made to US-A-3,087,936, 3,254,025, 3,322,670, 3,344,069, 4,080,303, 4,426,305, 4,925,983 and 5,114,602.

AG dispersants are characterized by an infrared peak in the region of 1590 cm⁻¹. In addition, the spectrum may show a peak in the region of 1690 cm⁻¹, but AG dispersants that do not have this peak can also be used. When prepared at molar ratios of about 1:1 or less, a peak appears at 1725 cm⁻¹. In the examples of US-A-5,080,815, the peak at 1590 cm⁻¹ is almost absent. The chemical structures of the products of the invention are not known, but based on their infrared spectra they do not appear to contain significant triazole components, as evidenced by the absence of the IR peak at 1640 cm-1 present in the examples of US-A-5,080,815.

Processes for preparing suitable aliphatic hydrocarbyl substituted succinic acid derivatives (acid, anhydride, lower alkyl ester or acyl halide), such as alkenyl succinic anhydrides, for use in the reaction with aminoguanidine or basic salts thereof are known. Such acylating agents are extensively described and discussed in the literature, e.g. US-A-3,215,707, 3,219,666, 3,321,587, 3,254,025, 3,282,955, 3,361,673, 3,401,118, 3,912,764, 4,110,349, 4,234,435, 4,908,145, 5,071,919, 5,080,815 and 5,137,978. In fact, suitable acylating agents of this type are produced in large quantities and are widely used for the preparation of dispersants. Preferred acylating agents used to prepare component a) are derived from a polyalkene having a number average molecular weight determined by GPC in the range of 900 to 5,000. Most preferably, they have a number average molecular weight in the range of 1,200 to 2,500. Although homo- and copolymers of various 1-olefins can also be used to prepare the acylating agents, commercial grades of polyisobutene are preferred.

The synthesis of typical AG dispersants and borated AG dispersants is described in the following examples.

Example A-1

To a reaction vessel is added 1665 g (0.48 mole) of 60% active polyisobutenyl succinic anhydride (PIBSA) (prepared from polyisobutylene with a number average molecular weight of about 2060), 76.8 g (0.56 mole) of 98.5% aminoguanidine bicarbonate (AGB) and 600 g of a neutral 100 base oil. The molar ratio of AGB to PIBSA is 1.2:1. The mixture was heated under a stream of nitrogen with stirring for 2 hours at 170°C. The product is filtered while hot and then allowed to cool.

Example A-2

The procedure of Example A-1 is repeated. Instead of the PIBSA of Example A-1 with higher molecular weight, a chemically equivalent amount of PIBSA produced using a polyisobutylene with a number average molecular weight of about 1290.

Example A-3

The procedure of Example A-1 is repeated with the difference that the molar ratio of AGB to PIBSA is 1.1:1.

Example A-4

Example A-3 is repeated with the difference that the PIBSA from Example A-2 is used.

Example A-5

Product prepared as in Example A-3 is borated by heating 2290 g of the 44% active product with 212.5 g of a superborated polyisobutenyl succinic ester amide containing approximately 2.5% boron at 160°C for 2 hours. The resulting product is diluted with 154 g of oil to give a product containing 0.2% boron.

Example A-6

Example A-5 is repeated using 2000 g of the product formed in Example A-4 and 185.6 g of the superborated ester amide. The boron content of the borated product when diluted with 134 g of oil is 0.2%.

Example A-7

Product prepared as in Example A-1 (2290 g) is borated by heating with 572.5 g of the superborated ester amide and diluting with oil to give a product containing 0.5% boron.

Example A-8

Example A-7 is repeated except that 2000 g of active product prepared as in Example A-2 is used instead of the higher molecular weight product of Example A-1.

Examples A-9 to A-15

The procedure of Example A-1 is repeated seven times in the same manner, each time changing the proportions of AGB and PIBSA so that the molar ratios of AGB to PIBSA are 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, and 1:1, respectively.

Examples A-16 to A-22

Examples A-9 to A-15 are repeated, but using the product prepared as in Example A-2 instead of the product prepared in Example A-1.

Examples A-23 to A-36

The respective products prepared in Examples A-9 to A-22 are boronized to a boron content of 0.2% using the boronization process of Example A-5.

Example A-37

Example A-1 is repeated with the difference that 1.0 mole of AGB is reacted with 0.8 mole of PIBSA. Borination to a boron content of 0.2% is carried out with boric acid at a suitable temperature between 145 and 165ºC. Water is driven off after completion of boration at about 155ºC and 40 mm Hg.

Component b)

This oil-soluble ashless dispersant is obtained by reacting (i) an acyclic hydrocarbyl succinic acid acylating agent and (ii) an alkylene polyamine having an average of 3 to 6 nitrogen atoms (and preferably an average of about 4 to about 5 nitrogen atoms) per molecule in a molar ratio of 1.6 to 2 moles (preferably about 1.8 to 2) of (i) per mole of (ii) to form a succinimide, and heating the succinimide thus formed simultaneously or in any order and at a temperature in the range of 150 to 180°C with (iii) at least one dicarboxylic acid acylating agent having less than 20 carbon atoms in the molecule and (iv) at least one boron compound to produce a product having (I) a total base number in the range of 33 to 45 mg KOH per gram of product (excluding the weight of any solvent or thinner associated with that product) and (2) a boron content in the range of 1.0 to 1.4% by weight (again, excluding the weight of any solvent and/or thinner associated with that product).

Aliphatic hydrocarbyl substituted succinic acid derivatives (acid, anhydride, lower alkyl ester or acyl halide), such as succinic anhydrides, used as reactant (i) are of the same general type as those used to prepare component a). Reference is therefore made to the above description for further details. However, it will be understood that the acylating agents used to prepare components a) and b) do not have to be identical. For example, the number average molecular weights of the polyolefins used to prepare the respective succinic acylating agents may be the same, but may also be different from one another, whereby the number average molecular weight of one of the polyolefins may be higher than that of the other. Similarly, the succinic acylating agents used to prepare components a) and b) may both be (and preferably are) anhydrides, although it is also possible to use different types of functionalised succinic acylating agents to prepare the respective components (e.g. an anhydride to prepare one of the components and a free acid to prepare the other).

Alkylene polyamines having an average of about 3 to about 6 nitrogen atoms per molecule used as reactants (ii) in the preparation of component b) are generally referred to in the art as dialkylene triamines, trialkylene tetramines, tetraalkylene pentamines and pentaalkylene hexamines. The alkylene groups of these materials may each have 2 to 4 or more carbon atoms. Preferably, polyethylene polyamines are used, i.e., the polyalkylene polyamines in which the alkylene groups are ethylene groups (i.e., dimethylene groups). The alkylene polyamines used in the synthesis of component b) may be substantially pure compounds of the indicated structure (e.g., substantially pure tetraethylene pentamine of the formula H₂NC₂H₄-NH-C₂H₄-NH-C₂H₄-NH-C₂H₄-NH₂) or industrial grade materials derived from various manufacturers. For example, these industrial-grade products are often referred to as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine, although they typically include linear, branched, and cyclic species.

The dicarboxylic acid acylating agent having less than 20 carbon atoms in the molecule used as reactant (iii) in the post-treatment of the succinimide is preferably selected from: (a) acyclic dicarboxylic acids having up to 6 carbon atoms in the molecule in which the carboxyl groups are attached to adjacent carbon atoms, (b) anhydrides of these dicarboxylic acids, (c) acyl halides of these dicarboxylic acids, and (d) acyclic mono- and/or dihydrocarbyl esters of these dicarboxylic acids having not more than 7 carbon atoms per hydrocarbyl group. Examples of these acylating agents include maleic acid, maleic anhydride, α-ethylmaleic acid, malic acid, fumaric acid, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride, succinic acid, succinic anhydride, α-methylsuccinic acid, α,α-dimethylsuccinic acid, α,β-dimethylsuccinic acid, α-ethylsuccinic acid, thiomalic acid, tartaric acid, the monoalkyl esters of the above acids in which the alkyl group has 1 to 7 carbon atoms, the dialkyl esters of the above acids in which each alkyl group has 1 to 7 carbon atoms, the monoalkenyl esters of the above acids in which the alkenyl group has 2 to 7 carbon atoms, the dialkenyl esters of the above acids in which each alkenyl group has 2 to 7 carbon atoms, the acyl chlorides of the above acids, and the like. The most preferred post-treatment agent used in this invention is maleic anhydride.

Reactant (iv) is a boron-containing material of the same general type used to borate component a) according to a preferred embodiment. Similarly, the temperature and other boration conditions may be the same or similar to those used to prepare a borated version of component a). Therefore, reference is made to the discussion above for further details. However, it will be understood that the borating agents and conditions used to prepare component b) and those used to prepare a borated version of component a) need not be identical. Thus, for example, the borating agents may both be the same boric acid, boric ester, boron halide, boron oxide, ammonium borate, organoborane or superborated ashless dispersant. Conversely, the borating agent used to prepare one of the components may be different from that used to borate the other. Likewise, the times and temperatures as well as the ratios of the components used for the respective boronizations can be the same or different - one component can be boronized more strongly than the other.

Suitable processes for preparing component b) are illustrated in the following examples.

Example B-1

In a first reaction stage, polyisobutenyl succinic anhydride (PIBSA), which was prepared from polyisobutylene with a number average GPC molecular weight of about 1,300, and tetraethylenepentamine (TE-PA) are reacted in a molar ratio of 1.8:1 at 165 to 170°C for 4 hours. In a second reaction stage, maleic anhydride (MA) is added to the product of the first reaction stage in an amount of 0.35 moles per Moles of TEPA from the first stage are added and the resulting mixture is heated at 165-170ºC for 1.5 hours. Oil is then added. In a third reaction step, boric acid is added to the second stage reaction mixture at a temperature of 150-155ºC in an amount of 4.0 moles per mole of TEPA originally used. The mixture is heated at 150ºC for one hour; then water formed in the third reaction step is removed by applying a 40 mm vacuum for one hour. The resulting succinimide is both acylated and borated and has a nitrogen content of 1.74% and a boron content of 1.20%.

Example B-2

The procedure of Example B-1 is repeated except that the amount of boric acid is reduced to 3.0 moles per mole of TEPA initially used. The final product, diluted with 100% Solvent Neutral Mineral Oil to a nitrogen content of 1.70%, contains 0.82% boron.

Example B-3

Repeating Example B-1, further reducing the amount of boric acid to 2.0 moles per mole of TEPA initially used, produces a concentrate (which is diluted as in Example B-1) with a boron content of 0.62%.

Example B-4

Example B-1 is repeated using 3.2 moles of boric acid per mole of TEPA initially used. The product concentrate (diluted as in Example B-1) contains 0.88% boron.

Example B-5

The procedure of Example B-1 is repeated except that the reaction with boric acid is carried out before the reaction with maleic anhydride and the amount of boric acid used is 3.0 moles per mole of TEPA used in the first reaction step. The final product (diluted as in Example B-1) contains 0.9% boron.

Example B-6

Example 5 is repeated with the difference that the maleic anhydride and boric acid are reacted simultaneously with the succinimide produced in the first reaction stage. Such a product contained 1.66% nitrogen and 0.87% boron when diluted with 100% solvent neutral mineral oil.

Example B-7

In a first reaction step, polyisobutenyl succinic anhydride (PIBSA), prepared from polyisobutylene having a GPC number average molecular weight of about 1,300, and tetraethylenepentamine (TEPA) in a molar ratio of 1.8:1 are reacted at 165-170°C for 4 hours and then mineral oil is added. In a second reaction step, maleic anhydride (MA) is added to the product of the first reaction step in an amount of 0.3 moles per mole of TEPA of the first step and the resulting mixture is heated at 165-170°C for 1.5 hours. In a third reaction step, boric acid (BA) is added to the second stage reaction mixture at a temperature of 150-155°C in an amount of 3.0 moles per mole of TEPA used in the first step. The resulting mixture is heated at 150-155°C for 2.5 hours. The additive concentrate has a nitrogen content of 1.8% and a boron content of 0.9%.

Example B-8

The procedure of Example B-7 is repeated except that in the first stage PIBSA and TEPA are reacted in a molar ratio of 1.7:1. In the second stage the MA is used in an amount equal to a molar ratio of 0.4:1 based on the TEPA used in the first stage. In the third stage the boric acid (3.0 moles per mole of TEPA used in the first reaction stage) is added in an oil slurry. The diluted product has a nitrogen content of 1.95% and a boron content of 0.64%.

Example B-9

In the first reaction step, polyisobutenyl succinic anhydride having a number average GPC molecular weight of about 1,200 and TEPA in a molar ratio of 1.8:1 are reacted. In a second step, maleic anhydride is added to the reaction product of the first step in an amount of 0.35 moles per mole of TEPA used in the first step and the resulting mixture is heated at 165 to 170°C for 1.5 hours. Mineral oil is then added. In a third reaction step, boric acid is added to the reaction product of the second step in an amount of 0.4 moles per mole of TEPA used in the first step and the resulting mixture is heated at 150 to 155°C for 3 hours. The product has a nitrogen content of 1.85% and a boron content of 0.15%.

Component c)

Methylhydrocarbyldithiophosphates are generally prepared by reacting phosphorus pentasulfide with one or more alcohols or phenolic compounds or diols to produce a hydrocarbyldithiophosphoric acid, which is then neutralized with one or more metal-containing bases. When a monohydric alcohol or phenol is used in this reaction, the final product is a zinc dihydrocarbyldithiophosphate. On the other hand, when a suitable diol (e.g., 2,4-pentanediol) is used in this reaction, the final product is a zinc salt of a cyclic hydrocarbyldithiophosphoric acid (see, e.g., U.S. Patent No. 3,089,850). These cyclic derivatives function essentially the same as the dihydrocarbyl analogues.

Suitable oil-soluble metal dihydrocarbyl dithiophosphates include molybdenum dihydrocarbyl dithiophosphates, nickel dihydrocarbyl dithiophosphates, copper dihydrocarbyl dithiophosphates, cadmium dihydrocarbyl dithiophosphates, cobalt dihydrocarbyl dithiophosphates, and similar materials. The hydrocarbyl groups include cyclic and acyclic groups which may be both saturated and unsaturated, such as alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, cycloalkylalkyl, aralkyl, and the like. Of course, the hydrocarbyl groups may also contain elements other than carbon and hydrogen, provided that these elements do not interfere with the predominantly hydrocarbon character of the hydrocarbyl group. Thus, the hydrocarbyl groups may contain ether oxygen atoms, thioether sulfur atoms, secondary or tertiary amino nitrogen atoms, and/or inert functional groups such as esterified carboxylic acid groups, keto groups, thioketo groups, and the like. The preferred materials are the oil-soluble Zinc dihydrocarbyldithiophosphates, particularly the oil-soluble zinc dialkyldithiophosphates and especially the oil-soluble zinc dialkyldithiophosphates in which the alkyl groups are a mixture of primary and secondary alkyl groups. Such primary and secondary alkyl group mixtures can be prepared by forming a mixture of two or more zinc dialkyldithiophosphates to yield a mixture or combination of zinc dialkyldithiophosphates having the desired types and proportions of primary and secondary alkyl groups. Alternatively, the mixtures of primary and secondary alkyl groups can be prepared by reacting phosphorus pentasulfide with a mixture or combination of primary and secondary alcohols to yield a zinc dialkyldithiophosphate product having the desired types and proportions of primary and secondary alkyl groups.

The phosphorodithioic acids from which the metal salts are prepared can be formed by the reaction of about 4 moles of one or more alcohols (cyclic or acyclic) or one or more phenols or a mixture of one or more alcohols and one or more phenols (or about 2 moles of one or more diols) per mole of phosphorus pentasulfide, and the reaction can be carried out in a temperature range of about 50 to about 200°C. Generally, the reaction is complete in about 1 to 10 hours. During the reaction, hydrogen sulfide is released.

The alcohols used to prepare the phosphorodithioic acids by the above process are preferably primary alcohols or secondary alcohols. Mixtures thereof are also suitable. The primary alcohols include propanol, butanol, isobutyl alcohol, pentanol, 2-ethyl-1-hexanol, isooctyl alcohol, nonanol, decanol, Undecanol, dodecanol, tridecanol, and the like. The primary alcohols may have various substituent groups such as halogen atoms, nitro groups, etc. which do not interfere with the desired reaction. Suitable secondary alcohols include 2-butanol, 2-pentanol, 3-pentanol, 2-hexanol, 4-methyl-2-pentanol, 5-methyl-2-hexanol, and the like. In some cases, it is preferred to use a mixture of different alcohols, e.g. mixtures of 2-propanol with one or more primary alcohols having a higher molecular weight, especially primary alcohols having from 4 to about 13 carbon atoms in the molecule. Such mixtures preferably contain at least 10 mole percent 2-propanol and usually from about 20 to about 90 mole percent 2-propanol. In a specific embodiment, the alcohol comprises about 30 to 50 mole percent 2-propanol, about 30 to 50 mole percent isobutyl alcohol, and about 10 to 30 mole percent 2-ethyl-1-hexanol.

Other suitable alcohol mixtures include 2-propanol/butanol, 2-propanol/2-butanol, 2-propanol/2-ethyl-1-hexanol, butanol/2-ethyl-1-hexanol, isobutyl alcohol/ 2-ethyl-1-hexanol and 2-propanol/tridecanol.

Cycloaliphatic alcohols suitable for use in the preparation of the phosphorodithioic acids include cyclopentanol, cyclohexanol, methylcyclohexanol, cyclooctanol, borneol and the like. Preferably, such alcohols are used in combination with one or more primary alkanols such as butanol, isobutyl alcohol and the like.

Exemplary phenols used to prepare the phosphorodithioic acids include phenol, o-cresol, m-cresol, p-cresol, 4-ethylphenol, 2,4-xylenol, and the like. It is desirable to use phenolic compounds in combination with primary alkanols such as propanol, butanol, hexanol, or the like.

Other alcohols that may be used include benzyl alcohol, cyclohexenol, and their ring alkylated analogues.

The preparation of the zinc salts of the dihydrocarbyldithiophosphoric acids or the cyclic hydrocarbyldithiophosphoric acids is usually carried out by reacting the acid product with suitable zinc compounds such as zinc oxide, zinc carbonate, zinc hydroxide, zinc alkoxide and other suitable zinc salts. Simply mixing and heating these reactants is usually sufficient to initiate the reaction. The resulting product is usually pure enough to be used. Typically the salts are prepared in the presence of a diluent such as alcohol, water or a light mineral oil. Neutral salts are prepared by reacting one equivalent of the zinc oxide or hydroxide with one equivalent of the acid. Basic zinc salts are prepared by adding an excess (i.e., more than one equivalent) of zinc oxide or hydroxide to one equivalent of dihydrocarbylphosphorodithioic acid or cyclic hydrocarbylphosphorodithioic acid.

In some cases, the incorporation of certain ingredients such as small amounts of zinc acetate or acetic acid along with the zinc reactant facilitates the reaction and yields an improved product. For example, the use of up to about 5% zinc acetate in combination with the required amount of zinc oxide facilitates the formation of zinc dihydrocarbyl dithiophosphates.

The preferred zinc salts of dialkyldithiophosphoric acids generally contain alkyl groups each having at least three carbon atoms. Preferably, the alkyl groups contain up to 10 Carbon atoms, although higher molecular weight alkyl groups are also conceivable. Some exemplary zinc dialkyldithiophosphates include zinc diisopropyldithiophosphate, zinc dibutyldithiophosphate, zinc diisobutyldithiophosphate, zinc di-sec-butyldithiophosphate, the zinc dipentyldithiophosphates, zinc diheptyldithiophosphates, the zinc diheptyldithiophosphates, the zinc dioctyldithiophosphates, the zinc dinonyldithiophosphates, the zinc dodecyldithiophosphates, and their higher homologues. Mixtures of two or more such zinc compounds are often preferred, such as the zinc salts of dithiophosphoric acids prepared from mixtures of isopropyl alcohol and secondary butyl alcohol, isopropyl alcohol, isobutyl alcohol and 2-ethylhexyl alcohol, isopropyl alcohol, butyl alcohol and pentyl alcohol, isobutyl alcohol and octyl alcohol, and the like.

The metal dihydrocarbyldithiophosphates can be products that have been post-treated with compounds such as carboxylic acids or epoxides.

Component d)

In general, the metal-containing detergents which can be used are oil-soluble or oil-dispersible basic salts of alkali or alkaline earth metals with one or more of the following acidic substances (or mixtures thereof): 1) sulfonic acids, 2) carboxylic acids, 3) salicylic acids, 4) alkylphenols, 4) sulfurized alkylphenols, 6) organic phosphoric acids characterized by at least one direct carbon-phosphorus bond. Such organic phosphoric acids include those obtained by treating an olefin polymer (e.g., polyisobutene having a molecular weight of 1000) with a phosphorizing agent such as phosphorus trichloride, phosphorus heptasulfide, phosphorus pentasulfide, phosphorus trichloride and sulfur, white phosphorus and a sulfur halide or phosphorus thiochloride. The most commonly used salts of such acids are those of sodium, potassium, lithium, calcium, magnesium, strontium and barium. The salts may be slightly basic or overbased materials or combinations thereof. Preferably, at least a portion of component d) is an overbased metal detergent having a total base number (TBN) of at least 200, more preferably in the range of 250 to 500. In this context, the TBN is determined according to ASTM D-2896-88.

A particularly effective method for preparing the basic salts comprises mixing an acid with an excess of a basic alkaline earth metal neutralizing agent and at least one alcohol accelerator and carbonating the mixture at an elevated temperature such as 60 to 200°C.

Processes for producing oil-soluble basic and overbased alkali and alkaline earth metal-containing detergents are known and extensively described in the patent literature. For this purpose, reference is made, for example, to the disclosures of US-A-2,451,345, 2,451,346, 2,485,861, 2,501,731, 2,501,732, 2,585,520, 2,671,785, 2,616,904, 2,616,905, 2,616,906, 2,616,911, 2,616,924, 2,616,925, 2,617,049, 2,695,910, 3,178,386, 3,367,867, 3,496,105, 3,629,109, 3,865,737, 3,907,691, 4,100,085, 4,129,589, 4,137,184, 4,148,740, 4,212,752, 4,617,135, 4,647,387 and 4,880,550.

Component e)

The inhibitors that can be used in the practice of this invention include one or more Oxidation inhibitors, foam inhibitors, rust inhibitors, corrosion inhibitors and friction inhibitors.

Oxidation inhibitors suitable for use in the compositions of the present invention include hindered phenol antioxidants, secondary aromatic amine antioxidants, sulfurized phenolic antioxidants, sulfurized olefin antioxidants, oil-soluble copper compounds, phosphorus-containing antioxidants, and the like. Mixtures of two or more of these types of antioxidants may also be used.

Amine antioxidants, particularly oil-soluble aromatic secondary amines, may also be used. Although aromatic secondary monoamines are preferred, aromatic secondary polyamines are also suitable. Exemplary aromatic secondary monoamines include diphenylamine, ring alkylated diphenylamines containing one or more alkyl ring substituents each containing up to about 16 carbon atoms, phenyl-α-naphthylamine, phenyl-β-naphthylamine, alkyl or aralkyl substituted phenyl-α-naphthylamine containing one or two alkyl or aralkyl groups each containing up to about 16 carbon atoms, alkyl or aralkyl substituted phenyl-β-naphthylamine containing one or two alkyl or aralkyl groups each containing up to about 16 carbon atoms, and similar compounds.

A preferred type of aromatic amine antioxidant is an alkylated diphenylamine in which one or both rings are substituted by an alkyl group (preferably a branched alkyl group) having 8 to 12 carbon atoms, preferably 8 or 9 carbon atoms. One such preferred compound is commercially available under the name Naugalube 438L, a substance believed to be predominantly consists of 4,4'-dinonyldiphenylamine with branched nonyl groups.

Another useful type of oxidation inhibitor that can be used in the compositions of the present invention is one or more oil-soluble sulfurized phenolic compounds. Oil-soluble sulfurized linear α-olefins are also very good oxidation inhibitors. Copper compounds as described in US-A-4,867,890 are also suitable when used in small, controlled concentrations.

Suitable foam inhibitors are described in "Foam Control Agents" by H.T. Kerner (Noyes Data Corporation, 1976, pp. 125-176). Typical foam inhibitors include silicones and organic polymers such as acrylate polymers. Mixtures of such silicone antifoam agents such as liquid dialkyl silicone polymers with various other substances are also effective. Typical of such mixtures are silicones blended with an acrylate polymer, silicones blended with one or more amines, and silicones blended with one or more amine carboxylates. Other such mixtures include combinations of a dimethyl silicone oil with (i) a partial fatty acid ester of a polyhydric alcohol (US-A-3,235,498), (ii) an alkoxylated partial fatty acid ester of a polyhydric alcohol (US-A-3,235,499), (iii) a polyalkoxylated aliphatic amine (US-A-3,235,501) and (iv) an alkoxylated aliphatic acid (US-A-3,235,502). Also suitable are the metal salts of styrene-maleic anhydride copolymers (US-A-3,296,131).

Rust inhibitors suitable for use may consist of a single compound or a mixture of compounds that inhibit the corrosion of ferrous metal surfaces. Such materials include oil-soluble monocarboxylic acids such as 2-ethylhexanoic acid, lauric acid, myristic acid, palmitic acid, oleic acid, linoleic acid, linolenic acid, behenic acid, cerotic acid, etc.; and oil-soluble polycarboxylic acids including dimer and trimer acids such as those prepared from tall oil fatty acids, oleic acid, linoleic acid, and the like. Other suitable corrosion inhibitors include alkenyl succinic acids in which the alkenyl group has 10 or more carbon atoms such as tetrapropenyl succinic acid, tetradecenyl succinic acid, hexadecenyl succinic acid, and the like, long chain α,ω-dicarboxylic acids in the molecular weight range of 600 to 3000, and other similar materials. Products of this type are currently available from various commercial sources, e.g. dimer and trimer acids. Another useful type of acidic corrosion inhibitors are the half esters of alkenyl succinic acids having 8 to 24 carbon atoms in the alkenyl group with alcohols such as polyglycols. The corresponding half amides of such alkenyl succinic acids are also suitable. Other suitable corrosion inhibitors include ether amines, acid phosphates, amines, polyethoxylated compounds such as ethoxylated amines, ethoxylated phenols and ethoxylated alcohols, imidazolines, and the like.

Suitable corrosion inhibitors include the thiazoles, triazoles and thiadiazoles. Examples include benzotriazole, tolyltriazole, octyltriazole, decyltriazole, dodecyltriazole, 2-mercaptobenzothiazole, 2,5-dimercapto- 1,3,4-thiadiazole, 2-mercapto-5-hydrocarbylthio-1,3,4-thiadiazole, 2-mercapto-5-hydrocarbyldithio-1,3,4-thiadiazole, 2,5-bis(hydrocarbylthio)-1,3,4-thiadiazole and 2,5-bis(hydrocarbyldithio)-1,3,4-thiadiazole. The preferred compounds are 1,3,4-thiadiazoles, particularly the 2-hydrocarbyldithio-5-mercapto-1,3,4-dithiadiazoles and the 2,5-bis(hydrocarbyldithio)-1,3,4-thiadiazoles, some of which are commercially available.

Such products are generally synthesized from hydrazine and carbon disulfide by known processes (see US-A-2,749,311, 2,760,933, 2,765,289, 2,850,453, 2,910,439, 3,663,561, 3,862,798, 3,840,594 and 4,097,387). Other suitable corrosion inhibitors include etheramines, polyethoxylated compounds such as ethoxylated amines, ethoxylated phenols and ethoxylated alcohols, imidazolines and the like.

Friction inhibitors that may be used include such substances as the alkyl phosphonates disclosed in US-A-4,356,097, aliphatic hydrocarbyl substituted ammonia or alkyl monoamine derived succinimides as disclosed in EP-A-0 020 037, dimer acid esters as disclosed in US-A-4,105,571, oleamide, sulfurized linear olefins, and the like. Glycerol oleates such as glycerol monooleate, glycerol dioleate, and pentaerythritol monooleate are other examples of suitable friction inhibitors that may be used to control friction and improve fuel economy.

Other suitable friction modifiers include aliphatic amines or ethoxylated aliphatic amines, aliphatic fatty acid amides, aliphatic carboxylic acids, aliphatic carboxylic acid esters, aliphatic carboxylic acid ester amides, aliphatic phosphates, aliphatic thiophosphonates, aliphatic thiophosphates, in which the aliphatic group usually contains more than about eight carbon atoms to render the compound suitably oil soluble.

A suitable combination of friction modifier and additive that can be used in the practice of this invention is described in EP-A-0 389 237. This combination includes the use of a long-chain succinimide derivative and a long-chain amide.

If desired, other suitable additives can also be used.

The practical application and advantages of this invention will be apparent from the following illustrative examples. It should be understood that these examples do not represent, and should not be construed as, limitations on the generic aspects of this invention. In these examples, all percentages are by weight and on an active ingredient basis.

example 1

A finished 10W-40 lubricant according to the invention is made up of the following components:

Component Percentage

a) 3.17

b) 1.09

c) 1.06

d) 2.67

e) 1.40

Base oil, viscosity index improvers, thinner oils to 100%

Component a) is prepared as in Example A-5 and component b) as in Example B-4. Component c) is a mixture of zinc dialkyldithiophosphates, 50% of which are C3 and C6 secondary alkyl groups and 50% are C3, C4 and C8 primary and secondary alkyl groups. Component d) is a mixture of 1.32% overbased calcium sulfonate, 0.7% low base calcium sulfonate and 0.65% sulfurized alkyl phenate.

Component e) is a mixture of 0.8% tertiary butylated phenolic antioxidant, 0.2% aromatic amine antioxidant, 0.4% sulfurized olefin oxidation inhibitor and less than 0.001% silicone type foam inhibitor. Commercial materials used to prepare this component mixture include HITEC® 611, 1656, 4733, 7169 and 7304 additives (Ethyl Petroleum Additives, Ltd., Ethyl Petroleum Additives, Inc.), OLOA 216C additive (Chevron Chemical Company) and Naugalube 438L additive (Uniroyal Chemical Company). The viscosity index improver is of the OCP type (Paratone 8000; Exxon Chemical Company). The finished lubricant has a total base number (TBN) of 10 mg KOH per gram according to the ASTM D2896 method, a zinc content of 0.12%, a phosphorus content of 0.11%, a calcium content of 0.35% and a boron content of 0.02%.

Example 2

A finished 10W-40 lubricant according to the invention is made up of the following components:

Component Percentage

a) 3.11

b) 1.10

c) 0.94

d) 2.36

e) 1.50

Base oil, viscosity index improvers, thinner oils to 100%

Component a) is prepared as in Example A-37 and component b) as in Example B-4. Component c) is a mixture of C₃ and C₆ zinc alkyl dithiophosphates. Component d) is a mixture of 1.18% overbased calcium sulfonate, 0.85% low base Calcium sulfonate and 0.33% sulfurized alkyl phenate. Component e) is a mixture of 1.0% tertiary butylated phenolic antioxidant, 0.5% aromatic amine antioxidant and less than 0.001% silicone type foam inhibitor.

Example 3

A finished lubricant according to the invention is prepared from the same components as in Example 1, but using the following proportions:

Component Percentage

a) 2.97

b) 1.37

c) 1.06

d) 2.67

e) 1.40

Base oil, viscosity index improvers, thinner oils to 100%

Example 4

A lubricating oil composition according to the invention is prepared using components a) and b) as in Example 2, an overbased magnesium alkylbenzene sulfonate having a TBN of 400 as component d) and components c) and e) as in Example 1 in the following proportions:

Component Percentage

a) 3.11

b) 1.10

c) 1.06

d) 2.28

e) 1.40

Base oil, viscosity index improvers, thinner oils to 100%

The performance of the compositions of the invention can be seen from the results of the MWM KD 12E engine test, which measures the performance of diesel truck engine lubricants under controlled conditions. The performance is given on a numerical scale, where the higher the numerical value, the greater the performance. In two such tests, a lubricant according to the invention and a lubricant not according to the invention were used. Both contained, in addition to a dispersant, a mixture of primary and secondary alkyl zinc dialkyl dithiophosphates, a mixture of high-base and low-base calcium sulfonates and a sulfurized calcium alkylphenyl in almost the same relative proportions. The main difference between these two lubricants is that the dispersant in the lubricant not according to the invention consisted exclusively of a higher dose of component a). Both lubricants were formulated to the 10W-40 specification grade and had a TBN of 10 mg KOH per gram and an ash content of 1.42%. The inventive lubricant achieved a rating of 80.6 compared to a rating of 70.9 for the non-inventive lubricant.

In tests conducted in a similar manner using the Volkswagen Intercooled (PV 1431) test, it was found that a typical composition according to the invention prepared as in Example 2 gave a significantly higher piston cleanliness than a comparable non-inventive lubricant composition. In both cases, the diesel engine was operated with diesel fuel having a sulfur content of 0.3%.

In the OM 364A standard test, a 10W-40 lubricant according to the invention showed excellent dispersibility and paint control as well as good performance in terms of wear.

The excellent performance of this invention with respect to fluoroelastomer seals is demonstrated by the results of tests conducted according to VW's stringent PV 3344 procedure. In a series of tests, VITON AK6 fluoroelastomer and the SAE 10W-40 truck crankcase lubricant of Example 1 were used. Table 1 summarizes the results. Table 1 Results of Fluoroelastomer Compatibility Tests

A second series of tests was conducted using the same procedure and fluoroelastomer and a composition prepared as in Example 3. The results are summarized in Tables 2 and 3. Table 2 Results of the tests for compatibility with fluoroelastomers Table 3 Results of tests for compatibility with fluoroelastomers

Tables 1, 2 and 3 show that the lubricants according to the invention met all the requirements of the stringent VW PV 3344 procedure in these tests and thus showed excellent results. Similarly good results were achieved with other compositions according to the invention.

The term "oil soluble" as used herein means that the product in question can be dissolved or stably dispersed in a 100 Solvent Neutral mineral oil at 25ºC to a concentration of at least 1% by weight.

Claims (20)

1. An oil-soluble dispersant composition, comprising a) an oil-soluble product prepared by reacting aminoguanidine with a long-chain alkyl or alkenyl succinic acid acylating agent in a molar ratio of 0.4 to 1.3 moles of aminoguanidine and/or a basic salt thereof per mole of acylating agent, and b) an oil-soluble product prepared by reacting (i) an acyclic hydrocarbyl succinic acylating agent and (ii) an alkylene polyamine having an average of 3 to 6 nitrogen atoms per molecule in a molar ratio of 1.6 to 2 moles of (i) per mole of (ii) to form a succinimide, and heating the succinimide thus formed simultaneously or in any order and at a temperature in the range of 150 to 180°C with (iii) at least one dicarboxylic acid acylating agent having less than 20 carbon atoms in the molecule and (iv) at least one boron compound to produce a product having (1) a total base number in the range of 33 to 45 mg KOH per gram of product excluding the weight of any solvent or diluent associated with said product and (2) a Boron content in the range of 1.0 to 1.4% by weight excluding the weight of any solvent and/or thinner associated with this product, where a) and b) are present in such ratios that for every 0.7 to 1.8 parts by weight of nitrogen from a) there are 0.3 to 1.5 parts by weight of nitrogen from b). 2. Composition according to claim 1, in which the molar ratio in a) is 0.8 to 1.3 moles of aminoguanidine and/or its basic salt per mole of the acylation agent; in which the alkylene polyamine of b) has an average of 4 to 5 nitrogen atoms per molecule; in which the molar ratio of (i) per mole of (ii) in b) is 1.8 to 2 moles of (i) per mole of (ii); and in which for each 0.8 to 1.7 parts by weight of nitrogen from a) there are 0.4 to 1.4 parts of nitrogen from b). 3. Composition according to claim 2, in which component a) is borated to have a boron content of up to about 1% by weight, excluding the weight of any solvent and/or diluent associated with this product. 4. A composition comprising 1 to 99 wt.% of at least one oil of lubricating viscosity and 99 to 1 wt.% of a composition according to claim 1. 5. A composition comprising 1 to 99 wt.% of at least one oil of lubricating viscosity and 99 to 1 wt.% of a composition according to claim 3. 6. Additive concentrate comprising a) an oil-soluble product prepared by reacting aminoguanidine with a long-chain alkyl or alkenyl succinic acid acylating agent in a molar ratio of 0.4 to 1.3 moles of aminoguanidine and/or a basic salt thereof per mole of acylating agent, b) an oil-soluble product prepared by reacting (i) an acyclic hydrocarbyl succinic acid acylating agent and (ii) an alkylene polyamine having an average of 3 to 6 nitrogen atoms per molecule in a molar ratio of 1.6 to 2 moles of (i) per mole of (ii) to form a succinimide, and heating the succinimide thus formed simultaneously or in any order and at a temperature in the range of 150 to 180°C with (iii) at least one dicarboxylic acid acylating agent having less than 20 carbon atoms in the molecule and (iv) at least one boron compound to produce a product having (1) a total base number in the range of 33 to 45 mg KOH per gram of the product excluding the weight of any solvent or diluent associated with said product and (2) has a boron content in the range of 1.0 to 1.4% by weight excluding the weight of any solvent and/or thinner associated with this product, c) at least one oil-soluble metal dihydrocarbyl dithiophosphate; d) detergent containing at least one alkali or alkaline earth metal and e) one or more inhibitors selected from at least one oxidation inhibitor, at least one foam inhibitor, at least one rust inhibitor, at least one corrosion inhibitor and at least one friction inhibitor, wherein components a) and b) are present in such ratio that for every 0.7 to 1.8 parts by weight of nitrogen from a) there are 0.3 to 1.5 parts by weight of nitrogen from b), and components a), b), c), d) and e) are present in the additive concentrate in such ratios that mixing a minor proportion of the additive concentrate into a base oil provides an oil mixture containing a dispersing amount of a) plus b) in the above ratios, an antiwear amount of c), a detergent amount of d) and an inhibitory amount of any selected inhibitor. 7. A composition according to claim 6, wherein the metal dihydrocarbyl dithiophosphate is at least one anti-wear and/or extreme pressure agent selected from zinc dialkyl dithiophosphate. 8. A composition according to claim 7, in which the alkyl groups of the zinc dialkyldithiophosphate are a mixture of primary alkyl groups and secondary alkyl groups. 9. Composition according to claim 6, in which the component a) is borated so that it has a boron content of up to about 1% by weight, excluding any solvent and/or diluent associated with this product. 10. The composition of claim 9 wherein the metal dihydrocarbyl dithiophosphate is at least one zinc dialkyl dithiophosphate antiwear/extreme pressure agent. 11. A composition according to claim 10, in which the alkyl groups of the zinc dialkyldithiophosphate are a mixture of primary alkyl groups and secondary alkyl groups. 12. Lubricating oil composition comprising a major amount of at least one oil of lubricating viscosity and a) a minor dispersing amount of an oil-soluble product prepared by reacting aminoguanidine with a long-chain alkyl or alkenyl succinic acid acylating agent in a molar ratio of 0.4 to 1.3 moles of aminoguanidine and/or a basic salt thereof per mole of acylating agent, b) a minor dispersant amount of an oil-soluble product prepared by reacting (i) an acyclic hydrocarbyl succinic acylating agent and (ii) an alkylene polyamine having an average of 3 to 6 nitrogen atoms per molecule in a molar ratio of 1.6 to 2 moles (i) per mole (ii) to form a succinimide, and heating the succinimide thus formed is reacted simultaneously or in any order and at a temperature in the range of 150 to 180°C with (iii) at least one dicarboxylic acid acylating agent having less than 20 carbon atoms in the molecule and (iv) at least one boron compound to produce a product having (1) a total base number in the range of 33 to 45 mg KOH per gram of product, excluding the weight of any solvent or diluent associated with said product, and (2) a boron content in the range of 1.0 to 1.4% by weight, excluding the weight of any solvent and/or diluent associated with said product, (c) a minor antiwear amount of at least one oil-soluble metal dihydrocarbyl dithiophosphate; (d) a minor detergent-acting quantity of at least one detergent containing an alkali or alkaline earth metal and e) a minor amount of one or more inhibitors selected from at least one oxidation inhibitor, at least one foam inhibitor, at least one rust inhibitor, at least one corrosion inhibitor and at least one friction inhibitor, wherein components a) and b) are present in such ratios that for every 0.7 to 1.8 parts by weight of nitrogen from a) there are 0.3 to 1.5 parts by weight of nitrogen from b), with the proviso that that the lubricating oil composition contains not more than 0.042 wt.% nitrogen from b). 13. The composition of claim 12 further comprising a viscosity index improving amount of a viscosity index improver. 14. The composition of claim 12 wherein the metal dihydrocarbyl dithiophosphate is at least one zinc dialkyl dithiophosphate antiwear/extreme pressure agent. 15. A composition according to claim 14, in which the alkyl groups of the zinc dialkyldithiophosphate are a mixture of primary alkyl groups and secondary alkyl groups. 16. The composition of claim 12 further comprising a viscosity index improving amount of a viscosity index improving agent and wherein metal dihydrocarbyl dithiophosphate is at least one antiwear/extreme pressure agent selected from zinc dialkyl dithiophosphate. 17. The composition of claim 12 wherein e) comprises a minor oxidation inhibiting amount of at least one oxidation inhibitor, a minor foam inhibiting amount of a foam inhibitor, and a minor friction inhibiting amount of a friction inhibitor. 18. A composition according to claim 12, wherein component a) is borated to have a boron content of up to about 1% by weight excluding a of any solvent and/or thinner associated with this product. 19. The composition of claim 18 wherein the composition further comprises a viscosity index improving amount of a viscosity index improver and wherein the metal dihydrocarbyl dithiophosphate is at least one zinc dialkyl dithiophosphate antiwear/extreme pressure agent. 20. A composition according to claim 19, in which the alkyl groups of the zinc dialkyldithiophosphate are a mixture of primary alkyl groups and secondary alkyl groups and in which e) contains a minor antioxidant amount of at least one oxidation inhibitor, a minor antifoam amount of a foam inhibitor and a minor friction inhibiting amount of a friction inhibitor.