Power transmission fluids

Abstract: Power transmission fluids having a Brookfield viscosity of 13,000 mPa s (13,000 cP) or less at -40°C, a viscosity of at least 2.5 mPa s at 150°C in the ASTM D-4683 method, and a viscosity of at least 6.8 mm²/s (6.8 cSt) at 100°C after 40 cycles in the FISST of ASTM D-5275 comprise at least 50 wt% of 55N to 125N hydrotreated mineral oils, 5 to 40 wt% of hydrogenated poly-α-olefin oligomer, 2 to 20 wt% of acrylic viscosity index improver and other additive components. The compositions possess a combination of performance properties necessary for electronically controlled automatic transmissions equipped with torque converter clutches capable of operating in a continuous slip mode.

Description: TECHNICAL FIELD This invention relates to oil-based power transmission fluid compositions, especially automatic transmission fluids, of enhanced performance capabilities. BACKGROUND The continuing development of new power transmission equipment such as automatic transmissions equipped with electronically controlled torque converter clutches capable of operating in a continuous slip mode, gives rise to ever-increasing demands for new automatic transmission fluids capable of meeting performance requirements sought by the original equipment manufacturers. For example, the need has arisen for automatic transmission fluids capable of meeting a number of specifications which include not only a number of performance requirements but an array of physical property parameters as well, including excellent viscometrics at high and low temperatures, and extremely high shear stability as reflected by the ASTM D-4683 method (Savant Viscosity Loss Trapezoid Method) and the ASTM D-5275 method (FISST or Fuel Injector Shear Stability Test), formerly known as the ASTM D-3945b method. This is illustrated by GB-A-2267098, US-A-5344579 and EP-A-454395 each of which describes lubricants with excellent viscometric properties. THE INVENTION It has been found possible to fulfill the foregoing need while at the same time providing automatic transmission fluids that are advantageous from the environmental and economic standpoints. Pursuant to this invention fluids are provided which have little or no content of metals, and the small amount of metal if present is typically an innocuous metal such as calcium. At the same time while certain synthetic base oils are desirable for use in such fluids because of properties which they may contribute to the overall product, they tend to be relatively expensive. However, this invention makes possible the achievement of excellent performance in fluids in which a major amount of the base oil is of mineral origin thereby minimizing costs. In accordance with this invention there is provided a power transmission fluid composition wherein the composition has on a weight basis an oil-soluble boron content of 0.001 to 0.1%, an oil-soluble phosphorus content of 0.005 to 0.2%, and either no metal additive content or an oil-soluble metal content as one or more metal-containing additives of no more than 100 ppm; wherein said composition comprises: a) at least 50 wt% based on the total weight of said composition of one or more hydrotreated mineral oils in the range of 55N to 125N; b) 5 to 40 wt% based on the total weight of said composition of hydrogenated poly-α-olefin oligomer fluid having a viscosity in the range of 2 to 6 cSt at 100°C; c) an active ingredient basis, 5 to 20 wt% based on the total weight of said composition of an acrylic viscosity index improver in the form of a solution in an inert solvent; d) an effective seal-swelling amount of at least one seal swell agent selected from oil-soluble dialkyl esters, oil-soluble sulfones, and- mixtures thereof; e) a dispersant amount of at least one oil-soluble ashless dispersant; f) a friction modifying amount of at least one oil-soluble friction modifier; and g) oil-soluble inhibitors selected from the group consisting of foam inhibitors, copper corrosion inhibitors, rust inhibitors, and oxidation inhibitors. In addition, the components referred to above are selected and combined such that finished composition has (i) a Brookfield viscosity of 13,000 cP or less at -40°C, (ii) a viscosity of at least 2.6 mPa.s at 150°C in the ASTM D-4683 method, and (iii) a viscosity of at least 6.8 cSt at 100°C after 40 cycles in the FISST of ASTM D-5275. It will be seen from the above that although the fluid composition contains on a weight basis from none to no more than 100 ppm (parts per million) of metals, the compositions of this invention do contain one or more components containing boron or phosphorus or a combination of boron and phosphorus, which elements of course are not classified as metals. Likewise small amounts of silicon in the form of silicone foam inhibitor may be, and preferably are, present in the compositions. Despite the fact that the base oils of the fluid compositions of this invention predominate in oils of mineral origin instead of synthetic lubricant, these fluid compositions have excellent low temperature and high temperature viscosity properties and possess high shear stability. This is made possible in part because the mineral oils used pursuant to this invention are hydrotreated mineral oils. Other contributing factors are the characteristics of the particular poly-α-olefin oligomer fluids and acrylic viscosity index improvers used in the compositions of this invention. In short, the unification of the herein-described components a), b) and c) in the proportions set forth above makes it possible to achieve these vitally important high and low temperature viscosity and shear stability properties. It is important to note that prior general purpose lubricant compositions, crankcase lubricant compositions, gear lubricant compositions, metal working fluid compositions, cutting oil fluid compositions, slideway lubricant compositions, manual transmission fluid compositions, transformer oil compositions, hydraulic fluids, etc., cannot be used in the practice of this invention. The performance parameters which must be achieved and that have been achieved pursuant to this invention cannot be realized by any such compositions that have been designed, used or suggested for use for such other purposes. The present invention involves highly specialized automatic transmission fluid compositions, an area which is generally regarded in the art as constituting perhaps the most complex area of technology in the entire field of lubrication and power transmission fluids. The compositions of this invention are thus of greatest utility and are especially adapted for use as automatic transmission fluids, and especially for use with the new generations of automatic transmissions equipped with electronically controlled torque converter clutches capable of operating in a continuous slip mode. The compositions of this invention can also be used as hydraulic fluids, although all of the excellent performance capabilities of the present compositions are unnecessary for such usage. Preferably, the ashless dispersant used in the compositions of this invention is a phosphorus-containing dispersant, and more preferably, a boron- and phosphorus-containing dispersant. In one embodiment the entire phosphorus and boron content of the finished fluid is supplied by a boron- and phosphorus-containing dispersant, such as a boron- and phosphorus-containing succinimide dispersant, a boron- and phosphorus-containing Mannich base dispersant, or the like. In another embodiment the entire boron content of the finished fluid is supplied by a boron- and phosphorus-containing dispersant whereas the phosphorus content is supplied in part by the boron- and phosphorus-containing dispersant and in part by a non-dispersant metal-free oil-soluble nitrogen- and phosphorus-containing antiwear/extreme pressure agent such as an amine phosphate, or the like. In this latter embodiment it is especially preferred to proportion these components such that a major amount of the phosphorus content in the finished fluid is supplied by the dispersant and a minor amount is supplied by the non-dispersant antiwear/extreme pressure agent. The finished compositions preferably contain a combination of all of the inhibitors referred to above. Each such inhibitor type, whether comprised of one or more individual component materials of that type, is present in an amount that is at least sufficient to provide the functional performance for which it has been selected. Thus in accordance with this preferred embodiment, the finished fluid will contain a foam-inhibiting amount of one or more foam inhibitors, a copper corrosion-inhibiting amount of one or more copper corrosion inhibitors, a rust-inhibiting amount of one or more rust inhibitors, and an oxidation-inhibiting amount of one or more oxidation inhibitors. In selecting these components it is important to ensure that the components are mutually compatible with each other, and that none of them significantly detracts from or interferes with the performance capabilities of the overall finished fluid composition. In this connection, while other inhibitor components can be used, preferred compositions are those in which the oil-soluble inhibitors include at least one 2,5-bis(alkyldithio)-1,3,5-thiadiazole, at least one ring-alkylated diphenylamine, at least one sterically-hindered tertiary butyl phenol, at least one calcium sulfurized alkylphenate, at least one alkyloxypropylamine, at least one ethylene oxide-propylene oxide copolymeric surfactant, at least one aliphatic monocarboxylic acid, at least one alkyl glycol nonionic surfactant, and silicone foam inhibitor. The compositions of this invention preferably include at least one N-aliphatic hydrocarbyl-substituted diethanol amine in which the N-aliphatic hydrocarbyl-substituent is at least one straight chain aliphatic hydrocarbyl group free of acetylenic unsaturation and having in the range of 14 to 20 carbon atoms. Particularly preferred compositions are those which further include at least one N-aliphatic hydrocarbyl-substituted trimethylenediamine in which the N-aliphatic hydrocarbyl group is at least one straight chain aliphatic hydrocarbyl group free of acetylenic unsaturation and having in the range of 14 to 20 carbon atoms, or at least one hydroxyalkyl aliphatic imidazoline in which the hydroxyalkyl group contains from 2 to 4 carbon atoms, and in which the aliphatic group is an acyclic hydrocarbyl group containing from 10 to 25 carbon atoms. Component a) As noted above, a major amount of the oleaginous liquids of this invention is compounded from hydrotreated mineral base oils falling in the range of 55N to 125N. Oils of this type can be obtained from commercial petroleum refiners that utilize hydrotreating in their mineral oil refining operations. Examples of such materials are 60N, 80N and 100N mineral oils available, for example, from PetroCanada Limited. Hydrotreated oils are typically characterized by having reduced contents of impurities such as sulfur, nitrogen, oxygen and metals. Also, hydrotreating converts unsaturates in the oil, such as olefins, into saturated compounds. When conducted-at moderate or higher severity, hydrotreating can remove wax from the base stock and thereby lower its pour point The hydrotreated base oils used in the practice of this invention should be substantially free of wax. Component b) This component is one or more hydrogenated poly-α-olefin oligomer fluids having a viscosity at 100°C in the range of 2 to 6 cSt. Such fluids are formed by oligomerization of 1-alkene hydrocarbon having 6 to 20 and preferably 8 to 16 carbon atoms in the molecule and hydrogenation of the resultant oligomer. - Hydrogenated oligomers formed from 1-decene are particularly preferred. Methods for the production of such liquid oligomeric 1-alkene hydrocarbons are known and reported in the literature. See for example U. S. Pat. Nos. 3,763,244; 3,780,128; 4,172,855; 4,218,330; and 4,950,822. Additionally, hydrogenated 1-alkene oligomers of this type and of suitable viscosity grades are available as articles of commerce, for example, under the DURASYN trademark from Albemarle Corporation. Suitable 1-alkene oligomers are also available from other suppliers. Preferred oligomers are formed by use of a Friedel-Crafts catalyst (especially boron trifluoride promoted with water or a C 1-20 alkanol) followed by catalytic hydrogenation of the oligomer so formed using procedures such as are described in the foregoing U.S. patents. Other catalyst systems which can be used to form oligomers of 1-alkene hydrocarbons, which, on hydrogenation, provide suitable oleaginous liquids include Ziegler catalysts such as ethyl aluminum sesquichloride with titanium tetrachloride, aluminum alkyl catalysts, chromium oxide catalysts on silica or alumina supports and a system in which a boron trifluoride catalyst oligomerization is followed by treatment with an organic peroxide. Component c) This component is an acrylic viscosity index improver which is supplied in the form of an solution in an inert solvent, typically a mineral oil solvent, which usually is a severely refined mineral oil. The viscosity index improver solution as received often will have a boiling point above 200°C, and a specific gravity of less than 1 at 25°C. In addition, it has sufficient shear stability such that the finished composition possesses a viscosity of at least 6.8 cSt at 100°C after 40 cycles in the FISST (Fuel Injector Shear Stability Test) of ASTM D-5275. On an active ingredient basis (i.e., excluding the weight of inert diluent or solvent associated with the viscosity index improver as supplied), the finished fluid compositions of this invention will normally contain in the range of 5 to 20 wt% of the polymeric viscosity index improver. Small departures from this range may be resorted to as necessary or desirable in any given situation. Suitable proprietary materials for use as component c) are available from RÖHM GmbH (Darmstadt, Germany) under the trade designations: VISCOPLEX® 5543, VISCOPLEX® 5548, VISCOPLEX® 5549, VISCOPLEX® 5550, VISCOPLEX® 5551 and VISCOPLEX® 5151, and from Rohm & Haas Company (Philadelphia, Pennsylvania) under the trade designations ACRYLOID® 1277 and ACRYLOID® 1265E. Mixtures of the foregoing products can also be used. Preferably, the acrylic viscosity index will be provided as a hydrocarbon solution having a polymer content in the range of from 50 to 75 wt% and a nitrogen content in the range of 0.15 to 0.25 wt%. Such products preferably exhibit a permanent shear stability index (a PSSI value) using ASTM test method D-3945a of no higher than 35, preferably 30 or less, and most preferably 15 or less. Component d) The seal swell agent used in the compositions of this invention is selected from oil-soluble diesters, oil-soluble sulfones, and mixtures thereof. Generally speaking the most suitable diesters include the adipates, azelates, and sebacates of C 8 -C 13 alkanols (or mixtures thereof), and the phthalates of C 4 -C 13 alkanols (or mixtures thereof). Mixtures of two or more different types of diesters (e.g., dialkyl adipates and dialkyl azelates, etc.) can also be used. Examples of such materials include the n-octyl, 2-ethylhexyl, isodecyl, and tridecyl diesters of adipic acid, azelaic acid, and sebacic acid, and the n-butyl, isobutyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, and tridecyl diesters of phthalic acid. Other esters which may give generally equivalent performance are polyol esters such as Emery 2935, 2936, and 2939 esters from the Emery Group of Henkel Corporation and Hatcol 2352, 2962, 2925, 2938, 2939, 2970, 3178, and 4322 polyol esters from Hatco Corporation. Suitable sulfone seal swell agents are described in U.S. Pat. Nos. 3,974,081 and 4,029,587. Lubrizol 730 additive (The Lubrizol Corporation) is understood to be a commercially-available sulfone type seal swell agent. Typically these products are employed at levels in the range of 0.25 to 1 wt% in the finished fluid. Preferred seal swell agents are the oil-soluble dialkyl esters of (i) adipic acid, (ii) sebacic acid, or (iii) phthalic acid. The adipates and sebacates should be used in amounts in the range of 4 to 15 wt% in the finished fluid. In the case of the phthalates, the levels in the finished fluid should fall in the range of 1.5 to 10 wt%. Generally speaking, the higher the molecular weight of the adipate, sebacate or phthalate, the higher should be the treat rate within the foregoing ranges. Component e) The ashless dispersant can be of various types including succinimides, succinamides, succinic esters, succinic ester-amides, Mannich products, long chain hydrocarbyl amines, polyol esters, or the like. Of these, the succinimides are preferred for use in the practice of this invention. Methods for the production of the foregoing types of ashless dispersants are known to those skilled in the art and are reported in the patent literature. As used herein the term "ashless dispersant" means that the dispersant does not contain any metal constituent. As made clear above, the dispersant may contain boron, and preferably contains phosphorus, and most preferably contains both boron and phosphorus, elements which of course are not metals. Thus the term "ashless dispersant" encompasses dispersants which contain either or both of boron and phosphorus, even though such dispersant when thermally decomposed may leave some residues containing boron or phosphorus, or both. The preferred ashless dispersants are one or more alkenyl succinimides of an amine having at least one primary amino group capable of forming an imide group. The alkenyl succinimides may be formed by conventional methods such as by heating an alkenyl succinic anhydride, acid, acid-ester, acid halide, or lower alkyl ester with an amine containing at least one primary amino group. The alkenyl succinic anhydride may be made readily by heating a mixture of polyolefin and maleic anhydride to 180°-220°C. The polyolefin is preferably a polymer or copolymer of a lower monoolefin such as ethylene, propylene, isobutene and the like, having a number average molecular weight in the range of 700 to 2100 as determined by gel permeation chromatography (GPC). The more preferred source of alkenyl group is from polyisobutene having a GPC molecular weight in the range of 800 to 1800. In a still more preferred embodiment the alkenyl group is a polyisobutenyl group derived from polyisobutene having a GPC number average molecular weight of 800-1200, and most preferably in the range of 900-1000. Mannich base dispersants are also a highly useful type of ashless dispersant for use in the practice of this invention. Amines which may be employed in forming the ashless dispersant include any that have at least one primary amino group which can react to form an imide group and at least one additional primary or secondary amino group and/or at least one hydroxyl group. A few representative examples are: N-methyl-propanediamine, N-dodecyl- propanediamine, N-aminopropyl-piperazine, ethanolamine, N-ethanol- ethylenediamine and the like. Preferred amines are the alkylene polyamines, such as propylene diamine, dipropylene triamine, di-(1,2-butylene)triamine, and tetra-(1,2-propylene)pentamine. The most preferred amines are the ethylene polyamines which can be depicted by the formula H 2 N(CH 2 CH 2 NH) n H wherein n is an integer from one to about ten. These include: ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexamine, and the like, including mixtures thereof in which case n is the average value of the mixture. These depicted ethylene polyamines have a primary amine group at each end so can form mono-alkenylsuccinimides and bis-alkenylsuccinimides. Commercially available ethylene polyamine mixtures usually contain minor amounts of branched species and cyclic species such as N-aminoethyl piperazine, N,N'-bis(aminoethyl)piperazine, N,N'-bis(piperazinyl)ethane, and like compounds. The preferred commercial mixtures have approximate overall compositions falling in the range corresponding to diethylene triamine to tetraethylene pentamine, mixtures generally corresponding in overall makeup to tetraethylene pentamine being most preferred. Especially preferred ashless dispersants for use in the present invention are the products of reaction of a polyethylene polyamine, e.g. triethylene tetramine or tetraethylene pentamine, with a hydrocarbon substituted carboxylic acid or anhydride made by reaction of a polyolefin, preferably polyisobutene, of suitable molecular weight, with an unsaturated polycarboxylic acid or anhydride, e.g., maleic anhydride, maleic acid, fumaric acid, or the like, including mixtures of two or more such substances. When the ashless dispersant contains phosphorus, it serves as a multipurpose component in that it an antiwear/extreme pressure agent as well as a dispersant. Accordingly, when a phosphorus-containing or boron- and phosphorus-containing dispersant is used it can supply all or a portion of the requisite phosphorus content of the finished fluid composition. Methods suitable for introducing phosphorus or boron or a combination of phosphorus and boron into ashless dispersants are known and reported in the patent literature. One may refer, for example, to such U.S. patents as 3,087,936; 3,184,411; 4,747,971, and 4,857,214. The procedures that are described in U.S. 4,857,214 are especially preferred for use in forming component e) of the compositions of this invention. Accordingly, one preferred group of phosphorus- and/or boron-containing ashless dispersants comprises aliphatic hydrocarbyl-substituted succinimide of a mixture of cyclic and acyclic polyethylene polyamines having an approximate average overall composition falling in the range of from diethylene triamine through pentaethylene hexamine, said succinimide being heated with (1) at least one phosphorylating agent to form a phosphorus-containing succinimide ashless dispersant; or (2) at least one boronating agent to form a boron-containing succinimide ashless dispersant; or (3) either concurrently or in any sequence with at least one phosphorylating agent and at least one boronating agent to form a phosphorus- and boron-containing succinimide ashless dispersant. Particularly preferred ashless dispersants for use as component e) are aliphatic hydrocarbyl-substituted succinimides of the type described above which have been heated concurrently or in any sequence with a boron compound such as a boron acid, boron ester, boron oxide, or the like (preferably boric acid) and one or more inorganic phosphorus compounds such as an acid or anhydride (preferably phosphorous acid, H 3 PO 3 ) or a partial or total sulfur analog thereof to form an oil-soluble product containing both boron and phosphorus. The use of the partial or total sulfur analogs is less preferred. The amount of ashless dispersant on an "as received basis" (i.e., including the weight of impurities, diluents and solvents typically associated therewith) is generally within the range of 1 to 15 wt%, typically within the range of 1 to 10 wt%, preferably within the range of 1 to 6 wt%, and most preferably within the range of 2 to 5 wt%. Component f) The compositions of this invention contain one or more friction modifiers. These include such compounds as aliphatic amines or ethoxylated aliphatic amines, aliphatic fatty acid amides, aliphatic carboxylic acids, aliphatic carboxylic esters, aliphatic carboxylic ester-amides, aliphatic phosphonates, aliphatic phosphates, aliphatic thiophosphonates, aliphatic thiophosphates, etc., wherein the aliphatic group usually contains above about eight carbon atoms so as to render the compound suitably oil soluble. Also suitable are aliphatic substituted succinimides formed by reacting one or more aliphatic succinic acids or anhydrides with ammonia. One preferred group of friction modifiers is comprised of the N-aliphatic hydrocarbyl-substituted diethanol amines in which the N-aliphatic hydrocarbyl-substituent is at least one straight chain aliphatic hydrocarbyl group free of acetylenic unsaturation and having in the range of 14 to 20 carbon atoms. A particularly preferred friction modifier system is composed of a combination of at least one N-aliphatic hydrocarbyl-substituted diethanol amine and at least one N-aliphatic hydrocarbyl-substituted trimethylene diamine in which the N-aliphatic hydrocarbyl-substituent is at least one straight chain aliphatic hydrocarbyl group free of acetylenic unsaturation and having in the range of 14 to 20 carbon atoms. Further details concerning this friction modifier system are set forth in U.S. Pat. Nos. 5,372,735 and 5,441,656 both by Ohtani et al. Another particularly preferred friction modifier system is based on the combination of (i) at least one di(hydroxyalkyl) aliphatic tertiary amine in which the hydroxyalkyl groups, being the same or different, each contain from 2 to 4 carbon atoms, and in which the aliphatic group is an acyclic hydrocarbyl group containing from 10 to 25 carbon atoms, and (ii) at least one hydroxyalkyl aliphatic imidazoline in which the hydroxyalkyl group contains from 2 to 4 carbon atoms, and in which the aliphatic group is an acyclic hydrocarbyl group containing from 10 to 25 carbon atoms. For further details concerning this friction modifier system, reference should be had to U.S. Pat. No. 5,344,579. Generally speaking, the compositions of this invention will contain up to 1.25 wt%, and preferably from 0.05 to 1 wt% of one or more friction modifiers. Component g) This component will normally comprise a plurality of inhibitor components serving different functions. The inhibitors may be introduced in a preformed additive package which may contain in addition one or more other components used in the compositions of this invention. Alternatively these inhibitor components can be introduced individually or in various sub-combinations. While amounts can be varied within reasonable limits, the finished fluids of this invention will typically have a total inhibitor content in the range of 6 to 15 wt% and preferably 7 to 13 wt%, both on an "as received basis" - i.e., including the weight of inert materials such as solvents or diluents normally associated therewith. Foam inhibitors form one type inhibitor suitable for use as inhibitor components in the compositions of this invention. These include silicones, polyacrylates, surfactants, and the like. One suitable acrylic defoamer material is PC-1244 (Monsanto Company). Copper corrosion inhibitors constitute another class of additives suitable for inclusion in the compositions of this invention. Such compounds include thiazoles, triazoles and thiadiazoles. Rust or corrosion inhibitors comprise another type of inhibitor additive for use in this invention. Such materials include monocarboxylic acids and polycarboxylic acids. Examples of suitable monocarboxylic acids are octanoic acid, decanoic acid and dodecanoic acid. Suitable polycarboxylic acids include dimer and trimer acids such as are produced from such acids as tall oil fatty acids, oleic acid, linoleic acid, or the like. Products of this type are currently available from various commercial sources, such as, for example, the dimer and trimer acids sold under the HYSTRENE trademark by the Humko Chemical Division of Witco Chemical Corporation and under the EMPOL trademark by Henkel Corporation. Another useful type of rust inhibitor for use in the practice of this invention is comprised of the alkenyl succinic acid and alkenyl succinic anhydride corrosion inhibitors such as, for example, tetrapropenylsuccinic acid, tetrapropenylsuccinic anhydride, tetradecenylsuccinic acid, tetradecenylsuccinic anhydride, hexadecenylsuccinic acid, hexadecenylsuccinic anhydride, and the like. Also useful are the half esters of alkenyl succinic acids having 8 to 24 carbon atoms in the alkenyl group with alcohols such as the polyglycols. Other suitable rust or corrosion inhibitors include ether amines; acid phosphates; amines; polyethoxylated compounds such as ethoxylated amines, ethoxylated phenols, and ethoxylated alcohols; imidazolines; aminosuccinic acids or derivatives thereof, and the like. Materials of these types are available as articles of commerce. Mixtures of such rust or corrosion inhibitors can be used. Oxidation inhibitors constitute still another group of inhibitors which are preferably included in the compositions of this invention. These materials are exemplified by the phenolic antioxidants, aromatic amine antioxidants, sulfurized phenolic antioxidants, and organic phosphites, among others. Most preferred are sterically hindered tertiary butylated phenols, ring alkylated diphenylamines and combinations thereof. The amounts of the inhibitor components used will depend to some extent upon the composition of the component and its effectiveness when used in the finished composition. However, generally speaking, the finished fluid will typically contain the following concentrations (weight percent) of the inhibitor components (active ingredient basis): Inhibitor Typical Range Preferred Range Foam inhibitor 0 to 0.1 0 01 to 0.08 Copper corrosion inhibitor 0 to 1.5 0.01 to 1 Rust inhibitor 0 to 0.5 0.01 to 0.3 Oxidation inhibitor 0 to 1 0.1 to 0.6 Other Components Very small amounts of certain metal-containing detergents such as calcium sulfurized phenates can also be used. However, as noted above, if an oil-soluble phenate is used it should be proportioned such that the finished fluid contains no more than 100 ppm of metal, and preferably no more than 50 ppm of metal. These sulfurized phenates are preferably neutral salts containing a stoichiometric amount of calcium, and in any event should have a total base number (TBN) of not more than 200 mg KOH/gram. In another preferred embodiment, the finished fluid will contain only two sulfur-containing additive components, namely, (i) one or more oil-soluble calcium sulfurized alkylphenates and (ii) one or more oil-soluble 1,3,5-thiadiazole copper corrosion inhibitors such as a 2,5-bis(alkyldithio)-1,3,5-thiadiazole. In other words, these preferred compositions are devoid of conventional sulfur-containing antiwear additives such as sulfurized olefins (sulfurized isobutylene, etc), dihydrocarbyl polysulfides, sulfurized fatty acids, and sulfurized fatty acid esters. When the phosphorus content of the finished fluid is not completely supplied by use of a phosphorus-containing ashless dispersant (or a boron- and phosphorus-containing ashless dispersant), the remainder of the phosphorus content is preferably supplied by inclusion in the composition of one or more phosphorus-containing esters or acid-esters such as oil-soluble organic phosphites, oil-soluble organic acid phosphites, oil-soluble organic phosphates, oil-soluble organic acid phosphates, oil-soluble phosphoramidates, and oil-soluble phosphetanes. Examples include trihydrocarbyl phosphates, trihydrocarbyl phosphites, dihydrocarbyl phosphates, dihydrocarbyl phosphonates or dihydrocarbyl phosphites or mixtures thereof, monohydrocarbyl phosphates, monohydrocarbyl phosphites, and mixtures of any two or more of the foregoing. Oil-soluble amine salts of organic acid phosphates are a preferred category of auxiliary phosphorus-containing additives for use in the fluids of this invention. Sulfur-containing analogs of any of the foregoing compounds can also be used, but are less preferred. Most preferred as a commercially-available auxiliary phosphorus additive is an amine phosphate antiwear/extreme pressure agent available from Ciba-Geigy Corporation as Irgalube 349. Thus, in one of its embodiments, this invention provides compositions which contain a phosphorus-containing ashless dispersant such as a succinimide, a boron-containing ashless dispersant such as a succinimide, and/or a phosphorus- and boron-containing ashless dispersant such as a succinimide, together with at least one phosphorus-containing substance selected from (1) one or more inorganic acids of phosphorus; or (2) one or more inorganic thioacids of phosphorus; or (3) one or more monohydrocarbyl esters of one or more inorganic acids of phosphorus; or (4) one or more monohydrocarbyl esters of one or more inorganic thioacids of phosphorus; or (5) any combination of any two, or any three or all four of (1), (2), (3), and (4); or at least one oil-soluble amine salt or complex or adduct of any of (1), (2), (3), (4), and (5), said amine optionally being in whole or in part an amine moiety in (i) a basic nitrogen- containing ashless dispersant such as a succinimide or (ii) a boron- and basic nitrogen-containing ashless dispersant such as a succinimide or (iii) a phosphorus- and basic nitrogen-containing ashless dispersant such as a succinimide or (iv) a phosphorus-, boron- and basic nitrogen-containing ashless dispersant such as a succinimide. The boron content of the compositions of this invention is preferably supplied by use of a boron-containing ashless dispersant or a boron- and phosphorus-containing ashless dispersant). When the boron content of the finished fluid is not completely supplied in this manner, the remainder of the boron content is preferably supplied by inclusion in the composition of one or more oil-soluble boron esters such as a glycol borate or glycol biborate. Dyes, pour point depressants, air release agents, and the like can also be included in the compositions of this invention. In selecting any of the foregoing additives, it is important to ensure that each selected component is soluble in the fluid composition, is compatible with the other components of the composition, and does not interfere significantly with the requisite viscosity or shear stability properties of the overall finished fluid composition. It will be appreciated that the individual components employed, can be separately blended into the base fluid or can be blended therein in various subcombinations, if desired. Ordinarily, the particular sequence of such blending steps is not critical. Moreover, such components can be blended in the form of separate solutions in a diluent. It is preferable, however, to blend the additive components used in the form of an additive concentrate, as this simplifies the blending operations, reduces the likelihood of blending errors, and takes advantage of the compatibility and solubility characteristics afforded by the overall concentrate. Additive concentrates can thus be formulated to contain all of the additive components and if desired, some of the base oil component a) and/or b), in amounts proportioned to yield finished fluid blends consistent with the concentrations described above. In most cases, the additive concentrate will contain one or more diluents such as light mineral oils, to facilitate handling and blending of the concentrate. Thus concentrates containing up to about 50% by weight of one or more diluents or solvents can be used, provided the solvents are not present in amounts that interfere with the low and high temperature and flash point characteristics and the performance of the finished power transmission fluid composition. In this connection, the additive components utilized pursuant to this invention should be selected and proportioned such that an additive concentrate or package formulated from such components will have a flash point of 170°C or above, and preferably a flash point of at least 180°C, using the ASTM D-92 test procedure. It is deemed possible, but not desirable, to utilize blends of components a) and b) with one or more other base oils having suitable viscosities, provided that the resultant blend contains a major proportion of the combination of components a) and b), and possesses the requisite compatibility, viscosity properties, shear stability, and performance criteria for use in accordance with this invention. Illustrative of such potentially useable auxiliary base oils and fluids of lubricating viscosity are synthetic esters such as mixed C 9 and C 11 dialkylphthalates (e.g., ICI Emkarate 911P ester oil), trimethylol propane trioleate, di-(isotridecyl)adipate (e.g., BASF Glissofluid A13), pentaerythritol tetraheptanoate and equivalent synthetic base oils. Likewise certain dewaxed highly paraffinic mineral oils having the requisite viscosity parameters ana produced by processing other than hydrotreatment may be used in small amounts as auxiliary base oils. However in all cases the overall base oil must contain at least 50 wt% (and most preferably at least 60 wt%) of hydrotreated mineral oil(s) in the range of 55N to 125N, preferably in the range of 55N to 100N, and most preferably in the range of 60N to 80N, and for best results, these hydrotreated oils should be substantially wax-free. The practice and advantages of this invention are illustrated by the following illustrative examples in which all values are percentages by weight on an "as received basis". In these Examples Component a) is composed of a mixture of PetroCanada 60N and 80N hydrotreated mineral oils, Component b) is a 4 cSt hydrogenated poly-α-olefin oligomer fluid (Durasyn 164), Component c) is Viscoplex 5151, Component d) is dibutyl phthalate in Examples 1-3 and diisooctyl adipate in Example 5, Component e) is a boronated and phosphorylated preblend composition prepared substantially as described in Example 1A of U.S. Pat. No. 4,857,214, and the Silicone fluid is a 4% solution of poly(dimethylsiloxane) in light oil. EXAMPLES 1-10 Automatic transmission fluids are formed by blending together the components in the proportions as specified in Tables 1 and 2. Components Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Component a) - 60N 33.515 33.495 33.53 33.505 35.72 Component a) - 80N 24.280 24.280 24.28 24.715 31.11 Component b) 22.00 22.00 22.00 22.00 12.00 Component c) 12.60 12.60 12.60 11.50 11.80 Component d) 2.00 2.00 2.00 2.25 4.00 Component e) 3.77 3.77 3.77 4.00 3.77 Ethomeen T-12 0.14 0.14 0.13 0.13 0.15 Duomeen O 0.005 0.005 -- 0.005 -- Unamine O -- -- -- 0.01 0.01 Naugalube 438L 0.26 0.26 0.26 0.20 0.26 HiTEC® 4735 0.20 0.20 0.20 0.20 0.20 HiTEC® 4313 0.70 0.75 0.75 0.65 0.50 Irgalube 349 0.05 0.02 -- -- -- PC-1244 0.03 0.03 0.03 0.04 0.03 Silicone fluid 0.02 0.02 0.02 0.06 0.02 OLOA 216C 0.05 0.05 0.05 0.05 0.05 Mazawet 77 0.05 0.05 0.05 0.06 0.05 Tomah PA14 0.05 0.05 0.05 0.06 0.05 Pluronic L81 0.01 0.01 0.01 0.02 0.01 Octanoic acid 0.05 0.05 0.05 0.06 0.05 Red dye 0.02 0.02 0.02 0.02 0.02 Diluent oil - 45N 0.20 0.20 0.20 0.465 0.20 Components Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Component a) - 60N 33.595 33.765 33.720 37.570 33.795 Component a) - 80N 24.715 24.715 24.715 24.715 24.715 Component b) 22.00 22.00 22.00 18.00 22.00 Component c) 11.50 11.50 11.50 11.50 11.50 Component d) 2.25 2.25 2.25 2.25 2.25 Component e) 4.00 3.77 3.77 4.00 3.77 Ethomeen T-12 0.12 0.14 0.12 0.12 0.13 Duomeen O 0.005 0.005 -- -- 0.005 Unamine O 0.05 -- -- -- -- Naugalube 438L 0.20 0.26 0.30 0.40 0.26 HiTEC® 4735 0.20 0.20 0.30 0.20 0.20 HiTEC® 4313 0.65 0.65 0.55 0.50 0.55 PC-1244 0.02 0.03 0.04 0.02 0.03 Silicone fluid 0.02 0.02 0.06 0.02 0.06 OLOA 216C 0.05 0.05 0.04 0.05 0.05 Mazawet 77 0.05 0.05 0.04 0.05 0.06 Tomah PA14 0.04 0.05 0.05 0.05 0.06 Pluronic L81 0.01 0.01 0.01 0.02 0.02 Octanoic acid 0.04 0.05 0.05 0.05 0.06 Red dye 0.02 0.02 0.02 0.02 0.02 Diluent oil - 45N 0.465 0.465 0.465 0.465 0.465 Although each of the above compositions has not been evaluated, all experimental results obtained to date indicate that the compositions of the foregoing examples will possess (i) a Brookfield viscosity of 13,000 cP or less at -40°C, (ii) a viscosity of at least 2.6 mPa.s at 150°C in the ASTM D-4683 method, and (iii) a viscosity of at least 6.8 cSt at 100°C after 40 cycles in the FISST of ASTM D-5275. In addition, evaluations to date indicate that the compositions evaluated possess a combination of performance properties deemed necessary by an original equipment manufacturer for a new generation of electronically controlled automatic transmissions equipped with torque converter clutches capable of continuous slip operation. For example, based on existing data the compositions of this invention have the capability of exhibiting a positive slope in the plot of coefficient of friction versus sliding speed in the low speed SAE No. 2 Friction Test when performed in accordance with Ford Engineering Material Specification WSP-M2CZAA-A. That is, at 100°C the ratio of the coefficient of friction at 2 rpm to the coefficient of friction at 20 rpm is less than one and likewise, the ratio of the coefficient of friction at 40 rpm to the coefficient of friction at 120 rpm is also less than one. Moreover, the duration of the positive slope has been found to be at least 45 hours of continuous operation in the test, and has extended as long as 135 hours. Likewise, in clutch friction durability tests performed in accordance with Ford Engineering Material Specification WSP-M2CZAA-A involving 20,000 cycles, compositions of this invention have achieved the following results with SD 1777 friction material: µD values falling in the range of 0.130 to 0.170; µS values (at 0.25 seconds) falling in the range of 0.110 to 0.155; low-speed dynamic friction values falling in the range of 0.130 to 0.170; S1/D values falling in the range of 0.90 to 1.16; and stop times, in seconds, falling in the range of 0.70 to 1.0. With BW 4400 friction material, compositions of this invention have achieved the following results in the above clutch friction durability tests: µD values falling in the range of 0.110 to 0.135; µS values (at 0.25 seconds) falling in the range of 0.100 to 0.150; low-speed dynamic friction values falling in the range of 0.120 to 0.155; S1/D values falling in the range of 1.05 to 1.30; and stop times, in seconds, falling in the range of 0.80 to 1.05. In four-ball wear tests (ASTM D-4172) compositions of this invention have exhibited the following results in terms of wear scar diameters in millimeters: at 100°C and 600 rpm, wear scars falling in the range of 0.40 to 0.61; at 150°C and 600 rpm, wear scars falling in the range of 0.39 to 0.70; at 100°C and 1200 rpm wear scars falling within the range of 0.40 to 0.57; and at 150°C and 1200 rpm, wear scars falling within the range of 0.40 to 0.64. Falex EP tests (ASTM D-3233) gave the following results using compositions of this invention: at 100°C and one minute, values in the range of 1,000 to 2,000 lbs. were achieved; and at 150°C and one minute, values in the range of 1,000 to 2,000 lbs. were likewise achieved. Timken wear tests (ASTM D-2782) using compositions of this invention gave the following results: under a 9 lb. load at 100°C for 10 minutes and under a 9 lb. load at 150°C for 10 minutes, no scoring was observed. In addition, the burnish widths fell in the range of 0.42 to 0.65 mm under the 100°C test conditions and in the range of 0.46 to 0.73 mm under the 150°C test conditions. In the FZG gear wear tests compositions of this invention gave the following results at 1,450 rpm for 15 minutes: at 100°C, from a 9 stage pass to a 12 stage pass; and at 150°C, from an 11 stage pass to a 12 stage pass. Using the Aluminum Beaker Oxidation Test (ABOT) according to the Ford Mercon® Specification, after 300 hours the following results were achieved: pentane insolubles were well below 0.5 wt%; IR carbonyl increases were 20/cm and below; TAN increases were well below 4 mg KOH per gram of sample, and viscosity increases were below 30%. As used herein the term "oil-soluble" means that the substance under discussion should be sufficiently soluble at 20°C in the particular power transmission fluid composition being formulated pursuant to this invention base oil to reach at least the minimum concentration required to enable the substance to serve its intended function. Preferably the substance will have a substantially greater solubility in the fluid composition than this. However, the substance need not dissolve in the fluid composition in all proportions. It will be readily apparent that this invention is susceptible to considerable modification in its practice. Accordingly, this invention is not intended to be limited by the specific exemplifications presented hereinabove.

Claims: A power transmission fluid composition having on a weight basis an oil-soluble boron content of 0.001 to 0.1%, an oil-soluble phosphorus content of 0.005 to 0.2%, and either no metal additive content or an oil-soluble metal content as one or more metal-containing additives of no more than 100 ppm; said composition comprising: a) at least 50 wt% based on the total weight of said composition of one or more hydrotreated mineral oils in the range of 55N to 125N; b) 5 to 40 wt% based on the total weight of said composition of hydrogenated poly-α-olefin oligomer fluid having a viscosity in the range of 2 mm 2 /s (2 cSt) 6 mm 2 /s (6 cSt) at 100°C; c) 5 to 20 wt% based on the total weight of said composition of an acrylic viscosity index improver; d) at least one seal swell agent selected from oil-soluble dialkyl esters, oil-soluble sulfones, and mixtures thereof; e) at least one oil-soluble ashless dispersant; f) at least one oil-soluble friction modifier; and g) oil-soluble inhibitors selected from foam inhibitors, copper corrosion inhibitors, rust inhibitors, and oxidation inhibitors; with the proviso that said composition has (i) a Brookfield viscosity of 13,000 mPa s (13,000 cP) or less at -40°C, (ii) a viscosity of at least 2.6 mPa s at 150°C in the ASTM D-4683 method, and (iii) a viscosity of at least 6.8 mm 2 /s (6.8 cSt) at 100°C after 40 cycles in the FISST of ASTM D-5275. A composition according to Claim 1 wherein said ashless dispersant is a boron-and phosphorus-containing succinimide ashless dispersant obtainable by a process which comprises heating an alkenyl succinimide dispersant in which the alkenyl group is derived from a polyolefin having a GPC number average molecular weight in the range of 700 to 2100 concurrently or in any sequence with one or more inorganic phosphorus compounds and with one or more boron compounds to a temperature at which a solids-free composition is formed. A composition according to Claim 1 or Claim 2 wherein said ashless dispersant is a boron- and phosphorus-containing dispersant and wherein said oil-soluble inhibitors include at least one 2,5-bis(alkyldithio)-1,3,5-thiadiazole, at least one ring-alkylated diphenylamine, at least one sterically-hindered tertiary butyl phenol, at least one calcium sulfurized alkylphenate, at least one alkyloxypropylamine, at least one ethylene oxide-propylene oxide copolymeric surfactant, at least one aliphatic monocarboxylic acid, at least one alkyl glycol nonionic surfactant, and at least one silicone foam inhibitor. A composition according to any one of Claims 1 to 3 wherein the one or more hydrotreated mineral oils consist of a mixture of hydrotreated 60N mineral oil and hydrotreated 80N mineral oil and the hydrogenated poly-α-olefin oligomer fluid is polyα-olefin oligomer fluid with a viscosity of 4 mm 2 /s (4 cSt) at 100°C. A composition according to any one of Claims 1 to 4 wherein said friction modifier comprises at least one N-aliphatic hydrocarbyl-substituted diethanol amine in which the N-aliphatic hydrocarbyl-substituent is at least one straight chain aliphatic hydrocarbyl group free of acetylenic unsaturation and having in the range of 14 to 20 carbon atoms. A composition according to Claim 5 wherein said friction modifier further comprises (i) at least one N-aliphatic hydrocarbyl-substituted trimethylenediamine in which the N-aliphatic hydrocarbyl group is at least one straight chain aliphatic hydrocarbyl group free of acetylenic unsaturation and having in the range of 14 to 20 carbon atoms, or (ii) at least one hydroxyalkyl aliphatic imidazoline in which the hydroxyalkyl group contains from 2 to 4 carbon atoms, and in which the aliphatic group is an acyclic hydrocarbyl group containing from 10 to 25 carbon atoms. A composition according to any one of Claims 1 to 6 wherein said composition further comprises at least one non-dispersant metal-free oil-soluble nitrogen- and phosphorus-containing antiwear/extreme pressure agent, and wherein said phosphorus content is provided by said boron- and phosphorus-containing dispersant and said antiwear/extreme pressure agent. A composition according to any one of Claims 1 to 7 wherein said oil-soluble inhibitors include (i) in the range of 0.1 to 1.0 wt% of at least one 2,5-bis(alkyldithio)-1,3,4-thiadiazole and (ii) in the range of 0.01 to 0.1 wt% of calcium sulfurized alkylphenate, the foregoing components (i) and (ii) being the only sulfur-containing additive components in said composition. A composition according to any one of Claims 1 to 8 wherein said seal swell agent is at least one dialkyl ester of (i) adipic acid, (ii) sebacic acid, or (iii) phthalic acid. A composition according to Claim 9 wherein said seal swell agent consists essentially of diisoctyl adipate or dibutyl phthalate.

Inventors: SMITH DAVID W, SRINIVASAN SANJAY, SMITH, DAVID W., SRINIVASAN, SANJAY
Applicants: ETHYL CORP, ETHYL CORPORATION
Application year: 1995
Main classification: C10M169
IPC codes: C10M169, C10N40, C10M141, C10N20