US20060264340A1

US20060264340A1 - Fluid compositions for dual clutch transmissions

Info

Publication number: US20060264340A1
Application number: US11/133,553
Authority: US
Inventors: Ramnath Iyer; Samuel Tersigni; Jeffrey Milner
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-05-20
Filing date: 2005-05-20
Publication date: 2006-11-23
Also published as: KR100731562B1; KR20060120460A; CN1880419A; JP2006328393A; DE102006023219A1

Abstract

An additive composition and lubricating fluid are disclosed that provide high steel-on-paper friction durability, good metal-metal extreme pressure performance characteristics and synchronizer performance. The lubricating fluid includes a base oil, a succinimide dispersant, a succinimide friction modifier, and a phosphonate. Also disclosed is a method for lubricating a dual clutch transmission employing a plurality of wet clutches, with the lubricating fluid of the disclosure.

Description

BACKGROUND

1. Field
The present disclosure relates to a lubricant and a method for lubricating an automated dual clutch transmission having a plurality of wet clutches.
2. Brief Description of the Prior Art
Dual clutch transmissions, also known as double clutch or twin clutch transmissions, of a variety of types are known. Dual clutch transmissions are known to employ either dry or wet clutches. Some dual clutch transmissions employing wet clutches include hydrodynamic torque converters. For example, European publication EP 1 052 421 A, Nov. 15, 2000, discloses a multiple clutch system for a transmission, with two multi-disk clutches that are coaxial with each other, and each clutch is assigned to one of two shafts. The two clutches are arranged in a sealed chamber, which contains lubricating oil.
Volkswagen, for example, has introduced an automated dual clutch transmission (DCT) in Europe. Progressive improvements in the design and performance of automatic transmission and wet brake systems, and other friction-depending lubricants, requires concomitant progressive improvements in the design and performance of automatic transmission fluids, fluids for wet brake systems, and additive packages (concentrates) used in the formulation of automatic transmission fluids and wet brake fluids.
DCT's have an automatic direct-shifting gearbox (DSG) provided with an integrated dual clutch. These DCT's are designed to provide better fuel economy. However, these DCT's differ from automated manual transmissions since the DCT's typically do not include a torque converter. Instead, coordination of manual transmission gears is achieved through the use of dual wet clutches. As a result, performance requirements for fluids for lubricating DCT's involve elements of both manual transmission lubricants, and elements of automatic transmission lubricants. One or more of synchronization, extreme pressure performance, steel-on-steel friction material performance and steel-on-paper friction durability may be important for these DCT's.
Published European patent application publication number EP 0 020 037 discloses a lubricating oil composition containing a friction-reducing amount of an additive selected from the group consisting of oil soluble aliphatic hydrocarbon-substituted succinimide and succinamide and mixtures thereof wherein said hydrocarbon substituent contains about 12 to 36 carbon atoms. Similar friction modifiers are disclosed for use in automatic transmission fluids in U.S. Pat. Nos. 5,171,466; 5,312,555; 5,328,619; 5,358,652; 5,464,549; 5,505,868; 5,652,201; and 5,817,605.
The use of low molecular weight succinimide friction modifiers made from amines in automatic transmission fluids is disclosed in U.S. Pat. Nos. 5,750,476; 5,811,377; 5,840,662; 5,942,472; 6,225,266; and 6,337,309; and European patent application publication number EP 0 975 714.
The use of phosphonates in various functional fluids such as engine oil, automatic transmission fluids, gear oils, and power transmission fluids is disclosed in one or more of U.S. Pat. Nos. 4,158,633; 4,325,827; and 3,206,401; British patent application publication no. GB 1,247,541 and International published patent application nos. WO 98/47989, WO 90/09425, and WO 90/09386.
Accordingly, there is a need in the art for improved lubrication compositions and methods for use in conjunction with automated dual clutch transmissions (DCT's).

SUMMARY OF THE EMBODIMENTS

In a first aspect, the present disclosure relates to an additive composition for a transmission fluid for use in automated dual clutch transmissions. The additive contains at least a dispersant, a friction modifier, and a phosphonate. This additive is useful in automatic transmission fluids for meeting the performance requirements for use of such fluids in automated dual clutch transmissions.
In another aspect, the additive composition may be combined with a base oil to provide an automatic transmission fluid useful for meeting performance requirements in automated dual clutch transmissions.
In another aspect, the present disclosure relates to a method for increasing steel-on-steel friction, stabilizing steel-on-steel friction, and/or delivering good synchronizer performance by lubricating a transmission with a lubricating transmission composition including a major amount of a base oil and an additive composition as described herein.
In another aspect, the present disclosure relates to a method of lubricating an automated dual clutch transmission with a lubricating composition including a major amount of a base oil and an additive composition as described herein.

DETAILED DESCRIPTION

In a first aspect, the present disclosure relates to an additive composition for use in transmission fluids. The additive contains at least a dispersant, a friction modifier and a phosphonate. This additive is useful in automatic transmission fluids for meeting the performance requirements for use of such fluids in, for example, dual clutch transmissions (DCT's). Embodiments of the present disclosure may exhibit improved steel-on-steel friction as well as steel-on-paper friction performance capability, extreme pressure performance, and synchronizer performance. In particular, the present invention helps to deliver good synchronizer performance in synchronization systems employing, for example, sinter linings or carbon linings which may be used in dual clutch transmission systems.
One advantage of the compositions of the present invention is that these compositions are substantially zinc-free. By “substantially zinc-free” is meant that the compositions of the present invention may contain zinc as an impurity, and that these compositions are formulated without addition of metallic zinc or zinc compounds, other than zinc or zinc compounds which may be present as a minor impurity in one or more of the components of the compositions of the present invention.
Dispersant
One component of the additive composition of the present disclosure may be one or more conventional ashless dispersants. Suitable ashless dispersants are those having basic nitrogen and/or at least one hydroxyl group in the molecule, such as a succinimide dispersant, a succinamide dispersant, a succinic ester dispersant, a succinic ester-amide dispersant, a Mannich base dispersant, or a hydrocarbyl amine or polyamine dispersant.
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. For example, the synthesis of various ashless dispersants of the foregoing types is described in such patents as U.S. Pat. Nos. 2,459,112; 2,962,442, 2,984,550; 3,036,003; 3,163,603; 3,166,516; 3,172,892; 3,184,474; 3,202,678; 3,215,707; 3,216,936; 3,219,666; 3,236,770; 3,254,025; 3,271,310; 3,272,746; 3,275,554; 3,281,357; 3,306,908; 3,311,558; 3,316,177; 3,331,776; 3,340,281; 3,341,542; 3,346,493; 3,351,552; 3,355,270; 3,368,972; 3,381,022; 3,399,141; 3,413,347; 3,415,750; 3,433,744; 3,438,757; 3,442,808; 3,444,170; 3,448,047; 3,448,048; 3,448,049; 3,451,933; 3,454,497; 3,454,555; 3,454,607; 3,459,661; 3,461,172; 3,467,668; 3,493,520; 3,501,405; 3,522,179; 3,539,633; 3,541,012; 3,542,680; 3,543,678; 3,558,743; 3,565,804; 3,567,637; 3,574,101; 3,576,743; 3,586,629; 3,591,598; 3,600,372; 3,630,904; 3,632,510; 3,632,511; 3,634,515; 3,649,229; 3,697,428; 3,697,574; 3,703,536; 3,704,308; 3,725,277; 3,725,441; 3,725,480; 3,726,882; 3,736,357; 3,751,365; 3,756,953; 3,793,202; 3,798,165; 3,798,247; 3,803,039; 3,804,763; 3,836,471; 3,862,981; 3,936,480; 3,948,800; 3,950,341; 3,957,854; 3,957,855; 3,980,569; 3,991,098; 4,071,548; 4,173,540; 4,234,435; 5,137,980; 5,652,201; and Re 26,433, herein incorporated by reference. Other suitable dispersants may be found, for example, in U.S. Pat. Nos. 5,198,133; 5,256,324; 5,389,273; and 5,439,606, herein incorporated by reference.
In some embodiments, the ashless dispersant may comprise 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 about 180°-220° C. The polyolefin may be 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 about 900 to about 3000 as determined by gel permeation chromatography (GPC).
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-dodecylpropanediamine, N-aminopropyl-piperazine, ethanolamine, N-ethanol-ethylenediamine, and the like.
Suitable amines may include alkylene polyamines, such as propylene diamine, dipropylene triamine, di-(1,2-butylene)triamine, and tetra-(1,2-propylene)pentamine. A further example includes the ethylene polyamines which can be depicted by the formula H₂N(CH₂CH₂NH)_nH, wherein n may be an integer from about 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 they may form mono-alkenylsuccinimides and bis-alkenylsuccinimides. Commercially available ethylene polyamine mixtures may 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 commercial mixtures may have approximate overall compositions falling in the range corresponding to diethylene triamine to tetraethylene pentamine. The molar ratio of polyalkenyl succinic anhydride to polyalkylene polyamines may be from about 1:1 to about 2.4:1.
The Mannich base ashless dispersants may be formed by condensing about one molar proportion of long chain hydrocarbon-substituted phenol with from about 1 to about 2.5 moles of formaldehyde and from about 0.5 to about 2 moles of polyalkylene polyamine.
In some embodiments, the ashless dispersant may comprise the products of the 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, such as 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.
The dispersant may be present in an amount of from about 1% to about 6% by weight, based on the total weight of the lubricating composition. As a further example, the dispersant may be present in an amount of about 2 wt % to about 4 wt % in the lubricating composition (or finished fluid). The dispersant may be present in an amount of about 10 wt % to about 60 wt % in the additive composition.
Boron-Containing Dispersant
In certain embodiments, the additive composition may comprise at least one boron-containing dispersant, wherein the boron-containing dispersant is free of phosphorus. The boron-containing dispersant may be formed by boronating (borating) an ashless dispersant having basic nitrogen and/or at least one hydroxyl group in the molecule, such as a succinimide dispersant, succinamide dispersant, succinic ester dispersant, succinic ester-amide dispersant, Mannich base dispersant, or hydrocarbyl amine or polyamine dispersant. Methods that can be used for boronating the various types of ashless dispersants described above are described in U.S. Pat. Nos. 3,087,936; 3,254,025; 3,281,428; 3,282,955; 3,338,832; 3,344,069; 3,533,945; 3,658,836; 3,703,536; 3,718,663; 4,455,243; and 4,652,387.
In some embodiments, a boron-containing dispersant may comprise, for example, a boronated polyisobutylene succinimide or bis-succinimide or a mixture thereof. The polyisobutylene may have a molecular weight from about 210 to about 1300 amu, as a further example from about 900 to 1300 amu, and as an even further example from about 1200 to about 1300 amu.
A boron-containing dispersant may comprise from about 0.1 wt % to about 0.7 wt % of boron. As a further example, a boron-containing dispersant may comprise from about 0.25 wt % to about 0.7 wt % of boron.
Phosphorus-Containing Dispersant
In certain embodiments, the additive composition may comprise at least one phosphorus-containing dispersant e.g., a phosphorylated dispersant. The phosphorus-containing dispersant may be prepared by phosphorylating either a non-boronated dispersant or a boronated dispersant.
When the dispersant contains both phosphorous and boron, the phosphorus- and boron-containing dispersant may comprise, a phosphorylated and boronated polyisobutylene succinimide or bis-succinimide or a mixture thereof. The phosphorus- and boron-containing dispersant may comprise a polyisobutylene having a molecular weight of about 900 amu. Further, the phosphorus- and boron-containing dispersant may comprise the reaction product of a polyisobutylene succinimide with a boric acid (i.e., B(OH)₃) and a phosphorus acid (i.e., H₃PO₃).
The boron and phosphorus may be present in an amount of, for example, about 200 ppm or more of total boron and phosphorus in the lubricating composition (or finished fluid). As a further example, the boron and phosphorus may be present in an amount of, for example, about 400 ppm or more of total boron and phosphorus in the lubricating composition.
The Friction Modifier
The additive composition and/or lubricating composition may contain a friction-improving amount of a friction modifier, such as an amount that improves steel-on-steel friction, steel-on-paper friction, and/or synchronization performance.
Friction modifiers suitable for use in the present invention include such compounds as aliphatic fatty amines or alkoxylated aliphatic fatty amines, alkoxylated aliphatic ether amines, aliphatic carboxylic acids, aliphatic fatty acid amides, alkoxylated aliphatic fatty acid amides, aliphatic fatty imidazolines, and aliphatic fatty tertiary amines, 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 or other primary amines such as those taught in EP-A-0389237, as well as mixtures of two or more friction modifiers. Friction modifiers suitable for use in the present invention are described in the following U.S. patents, incorporated herein by reference for their disclosures relating to friction modifiers: U.S. Pat. Nos. 5,344,579; 5,372,735 and 5,441,656.
A suitable friction modifier may be selected from one or more of oil soluble aliphatic hydrocarbon-substituted succinimides and mixtures thereof wherein said hydrocarbon substituent contains about 12 to 36 carbon atoms. The aliphatic substituent on the succinic group can be any aliphatic hydrocarbon group containing about 12 to 36 carbon atoms including alkyl, alkenyl and polyunsaturated hydrocarbon groups.
Examples of these friction modifiers include:

n-dodecynyl succinimide,
1-methyltridecyl succinimide,
2-ethyltetradecyl succinimide,
n-hexadecenyl succinimide,
n-octadecyl succinimide,
n-octadecenyl succinimide,
1-methyleicosyl succinimide,
n-docosenyl succinimide,
4-ethyltriacontyl succinimide, and
n-hexadecenyl succinimide.

In an embodiment, the aliphatic hydrocarbon group may be bonded to the succinic group at a secondary carbon atom. These compounds have the formula:

wherein n is a small integer from about 2 to about 4 and Z is the group:

wherein R₁and R₂are independently selected from the group consisting of branched and straight chain hydrocarbon groups containing about 1 to about 34 carbon atoms such that the total number of carbon atoms in R₁and R₂is about 11 to about 35.
Examples of these friction modifiers are:

1-ethyltetradecyl succinimide
1-methylpentadecenyl succinimide
1,2-dimethyl octadecenyl succinamide
1-methyl-3-ethyl dodecenyl succinimide
1-decyl-2-methyl dotriacontyl succinimide.

In another embodiment, R₁and R₂may be straight chain aliphatic hydrocarbon groups. These friction modifiers have improved solubility in lubricating oil. Examples of these friction modifiers are:

1-methylpentadecyl succinimide
1-propyltridecenyl succinimide
1-pentyltridecenyl succinimide
1-tridecylpentadecenyl succinimide
1-tetradecyleicosenyl succinimide.

The above friction modifiers may be made from linear α-olefins containing about 12 to about 36 carbon atoms by isomerizing the α-olefins to form a mixture of internal olefins and reacting this mixture of internal olefins with maleic acid, anhydride or ester forming an intermediate and reacting the intermediate with ammonia to form amide, imide, or mixtures thereof. Friction modifiers made from isomerized linear α-olefins have greatly improved oil solubility compared with friction modifiers made with linear α-olefins.
Isomerization of the linear α-olefin can be carried out using conventional methods. One suitable method is to heat the linear α-olefin with an acidic catalyst. Especially useful acid catalysts are the sulfonated styrene-divinylbenzene copolymers. Such catalysts are commercially available and are conventionally used as cation exchange resins. In the present method they are used in their acid form. Use of such resins for isomerizing linear α-olefins is described in U.S. Pat. No. 4,108,889, incorporated herein by reference.
The compositions of the present invention may include mixtures of two or more friction modifiers. For example, a mixture of one or more succinimide friction modifiers with one or more amine friction modifiers may be employed.
The Phosphonate
The additive composition of the present disclosure may contain one or more phosphonates having the formula:

wherein R¹is an alkyl or alkenyl group containing about 12 to about 30 carbon atoms and wherein R²and R³are each independently hydrogen, an alkyl, or an alkenyl group. As examples, suitable alkyl groups may include methyl, ethyl, propyl, isopropyl, n-butyl, t-butyl, isobutyl, or any combination thereof. Examples of these phosphonates are dimethyl triacontylphosphonate, dimethyl triacontenylphosphonate, dimethyl eicosylphosphonate, dimethyl hexadecylphosphonate, dimethyl hexadecenylphosphonate, dimethyl tetracontenylphosphonate, dimethyl hexacontylphosphonate, dimethyl dodecylphosphonate, dimethyl dodecenylphosphonate, and the like.
In an embodiment R¹is an alkyl or alkenyl group containing about 16 to about 20 carbon atoms. Examples of these phosphonates are dimethyl hexadecylphosphonate, dimethyl hexadecenylphosphonate, dimethyl octadecylphosphonate, dimethyl octadecenylphosphonate, dimethyl eicosylphosphonate, and the like.
Suitable alkylphosphonate monoesters and processes for manufacturing the same are described in US 2004-0230068.
The phosphonates are added to the lubricating composition in an amount which improves friction performance, such as an amount that improves steel-on-steel friction, steel-on-paper friction, and/or synchronization performance. A suitable concentration may be from about 0.05 to about 3 wt %. As a further example, a suitable concentration may be from about 0.10 wt % to about 0.6 wt %.
Detergent
In some embodiments, the additive composition may also comprise a detergent. The detergent may comprise an overbased detergent, a borated detergent, and/or a borated overbased detergent. The detergent may comprise a sulfonate or a phenate. Further, the detergent may comprise a calcium-containing, a magnesium-containing, or a sodium-containing compound. The detergent may comprise, for example, a calcium sulfonate, a magnesium sulfonate, a sodium sulfonate, and/or a calcium phenate. For example, a calcium sulfonate detergent may comprise from about 1.5 wt % to about 20 wt % calcium, or as a further example from about 12 wt % to about 15 wt % calcium. Further, a calcium sulfonate detergent may comprise a total base number (TBN) of from about 3 mgKOH/g to about 450 mgKOH/g, as a further example of from about 250 mgKOH/g to about 400 mgKOH/g, and as an even further example of from about 250 mgKOH/g to about 350 mgKOH/g. A calcium phenate detergent may comprise from about 2.5 wt % to about 8.5 wt % calcium, or for example about 5 wt % calcium. Further, a calcium phenate detergent may comprise a TBN of from about 50 mgKOH/g to about 300 mgKOH/g, or for example, about 150 mgKOH/g.
Embodiments may contain alkali metal detergents and/or alkaline-earth metal detergents in addition or in the alternative to the detergents described above. Suitable alkali and alkaline-earth metal detergents may include oil-soluble neutral or overbased salts of alkali and alkaline-earth metals with one or more of the following acidic substances (or mixtures thereof): sulfonic acids, carboxylic acids, salicylic acids, alkyl phenols, and sulfurized alkyl phenols.
Oil-soluble neutral alkali and alkaline-earth metal-containing detergents are those detergents that contain stoichiometrically equivalent amounts of alkali and alkaline-earth metal in relation to the amount of acidic moieties present in the detergent. Thus, in general the neutral alkali and alkaline-earth metal detergents will have a low basicity when compared to their overbased counterparts. Methods of preparation of overbased alkali and alkaline-earth metal-containing detergents are known in the art and there are numerous commercially available overbased detergents on the market.
The alkali and alkaline-earth metal detergents include, but are not limited to, neutral and overbased sodium sulfonates, sodium carboxylates, sodium salicylates, sodium phenates, sulfurized sodium phenates, calcium sulfonates, calcium carboxylates, calcium salicylates, calcium phenates, sulfurized calcium phenates, lithium sulfonates, lithium carboxylates, lithium salicylates, lithium phenates, sulfurized lithium phenates, magnesium sulfonates, magnesium carboxylates, magnesium salicylates, magnesium phenates, sulfurized magnesium phenates, potassium sulfonates, potassium carboxylates, potassium salicylates, potassium phenates, and sulfurized potassium phenates.
The additive composition may be combined with a base oil to provide a power transmitting fluid. Such a power transmitting fluid may comprise a finished fluid.
In another embodiment, an automatic transmission fluid, or a dual clutch transmission fluid, may comprise an additive composition disclosed herein. The fluid may be suitable for an automated dual clutch transmission such as a DCT that employs at least two wet clutches. In an embodiment, the transmission fluid may be used in a DCT does not include a torque converter.
In another embodiment, a method of increasing steel-on-steel friction, stabilizing steel-on-paper friction and/or delivering good synchronizer performance may comprise lubricating a transmission with a lubricating composition comprising a major amount of a base oil and an additive composition as described herein.
A lubricating fluid may include other additives, such as, for example, one or more of an antiwear agent; an antioxidant or an antioxidant system, such as an amine antioxidant or phenolic antioxidant; a corrosion inhibitor or a corrosion inhibitor system; a metal deactivator; an anti-rust agent; one or more additional friction modifiers; a dye; a seal swell agent; an anti-foam agent; a surfactant; a viscosity index improver; a perfume or odor mask; and any suitable combinations thereof.
Sulfur-Containing Components
In some embodiments, the additive composition may also comprise one or more sulfur-containing components. For example, the additive composition may comprise a thiadiazole and/or a sulfurized fatty acid ester.
Suitable thiadiazoles include dialkyl thiadiazoles, including but not limited to an ashless dialkyl thiadiazole. Dialkyl thiadiazoles suitable for the practice of the present invention may be of the general formula (I):

wherein R₁and R₂may be the same or different hydrocarbyl groups, and/or one of R₁and R₂may be hydrogen, and x and y independently may be integers from 0 to 8. In one aspect, R₁and R₂may be the same or different, linear, branched, or aromatic, saturated or unsaturated hydrocarbyl group having from about 6 to about 18 carbon atoms, particularly from about 8 to about 12 carbon atoms, and x and y each may be 0 or 1.
Suitable dialkyl thiadiazoles include 2,5-bis(hydrocarbyldithio)-1,3,4-thiadiazoles. Examples of other suitable dialkyl thiadiazoles include, for example, 2,5-bis(hydrocarbylthio)-1,3,4-thiadiazoles, 2-(tert-hydrocarbyldithio)-5-mercapto-1,3,4-thiadiazoles, and bis-tert-dodecylthiothiadiazole.
Suitable dialkyl thiadiazoles also include those such as described in U.S. Pat. Nos. 2,719,125, 2,719,126, 3,087,932, 4,149,982, 4,591,645, and 6,528,458, and which descriptions are incorporated herein by reference. Mixtures of dialkyl thiadiazoles of formula (I) with monoalkyl thiadiazoles may also be used within the scope of the present invention.
As used herein, the term “hydrocarbyl group” or “hydrocarbyl” is used in its ordinary sense, which is well-known to those skilled in the art. Specifically, it refers to a group having a carbon atom directly attached to the remainder of a molecule and having a predominantly hydrocarbon character. Examples of hydrocarbyl groups include:
(1) hydrocarbon substituents, that is, aliphatic (e.g., alkyl or alkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl) substituents, and aromatic-, aliphatic-, and alicyclic-substituted aromatic substituents, as well as cyclic substituents wherein the ring is completed through another portion of the molecule (e.g., two substituents together form an alicyclic radical);
(2) substituted hydrocarbon substituents, that is, substituents containing non-hydrocarbon groups which, in the context of the description herein, do not alter the predominantly hydrocarbon substituent (e.g., halo (especially chloro and fluoro), hydroxy, alkoxy, mercapto, alkylmercapto, nitro, nitroso, and sulfoxy);
(3) hetero-substituents, that is, substituents which, while having a predominantly hydrocarbon character, in the context of this description, contain other than carbon in a ring or chain otherwise composed of carbon atoms. Hetero-atoms include sulfur, oxygen, nitrogen, and encompass substituents such as pyridyl, furyl, thienyl, and imidazolyl. In general, no more than two, or as a further example, no more than one, non-hydrocarbon substituent will be present for every ten carbon atoms in the hydrocarbyl group; typically, there will be no non-hydrocarbon substituent in the hydrocarbyl group.
Alternatively, sulfurized fatty acid esters such as linear C₁₄-C₁₈saturated or unsaturated chain monocarboxylic acid esters which are cross-linked by sulfur moieties in the forms of mono-, di- and poly-sulfides, may be employed. The relative fraction of the different sulfur bridges depends on reaction conditions and the relative amount of sulfur employed. The details of sulfurization of fatty acids are found in several references such as Organic Sulfur Compounds by L. Bateman and C. G. Moore, and Mechanism of Sulfur Reaction by W. A. Pryor. One exemplary material is sulfurized oleic acid with a sulfur concentration of about 5 to about 15% of the total weight of the sulfurized oleic acid ester, incorporated as the mono- and di-sulfides.
The amount of the thiadiazole or sulfurized fatty acid ester is selected to add sulfur to the composition in the amount of about 0.0075 to about 0.5 weight percent sulfur, based on the total weight of the composition.
Base Oils
Embodiments of the lubricating fluid may comprise a major amount of a base oil. Base or lubricating oils contemplated in preparing the power transmission fluids of the present disclosure may be derived from natural lubricating oils, synthetic lubricating oils, and mixtures thereof. Further, the base oil may comprise any suitable base oil or mixture of base oils for a particular application.
In some embodiments, additives may be provided in an additive package concentrate. Further, some embodiments may comprise a diluent, e.g., a diluent oil. A diluent may be included to ease blending, solubilizing, and transporting the additive package. The diluent may be compatible with a base oil and/or the additive package. The diluent may be present in any suitable amount in the concentrate. A suitable diluent may comprise a process oil of lubricating viscosity.
The additive combinations can be incorporated in a wide variety of base oils in effective amounts to provide suitable active ingredient concentrations. The base oils not only can be hydrocarbon oils of lubricating viscosity derived from petroleum (or tar sands, coal, shale, etc.), but also can be natural oils of suitable viscosities such as rapeseed oil, etc., and synthetic oils 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; alkyl esters of carbonic or phosphoric acids; polysilicones; fluorohydrocarbon oils; and mixtures of mineral, natural and/or synthetic oils in any proportion. The term “base oil” for this disclosure includes all the foregoing.
The additive combinations can thus be used in compositions, in which the base oil of lubricating viscosity is a mineral oil, a synthetic oil, a natural oil such as a vegetable oil, or a mixture thereof, e.g. a mixture of a mineral oil and a synthetic oil.
Suitable mineral oils include those of appropriate viscosity refined from crude oil of any source including Gulf Coast, Mid-continent, Pennsylvania, California, Alaska, Middle East, North Sea, and the like. Standard refinery operations may be used in processing the mineral oil. Among the general types of suitable petroleum oils are solvent neutrals, bright stocks, cylinder stocks, residual oils, hydrocracked base stocks, paraffin oils including pale oils, and solvent extracted naphthenic oils. Such oils and blends of them are produced by a number of conventional techniques which are widely known by those skilled in the art.
As is noted above, the base oil can consist essentially of or comprise a portion of one or more synthetic oils. Among the suitable synthetic oils are homo- and inter-polymers of about C₂to about C₁₂olefins, carboxylic acid esters of both monoalcohols and polyols, polyethers, silicones, polyglycols, silicates, alkylated aromatics, carbonates, thiocarbonates, orthoformates, phosphates and phosphites, borates and halogenated hydrocarbons. Representative of such oils are homo- and interpolymers of about C₂to about C₁₂monoolefinic hydrocarbons, alkylated benzenes (e.g., dodecyl benzenes, didodecyl benzenes, tetradecyl benzenes, dinonyl benzenes, di-(2-ethylhexyl)benzenes, wax-alkylated naphthalenes); and polyphenyls (e.g., biphenyls, terphenyls).
Alkylene oxide polymers and interpolymers and derivatives thereof where the terminal hydroxyl groups have been modified by esterification, etherification, and the like, constitute another class of synthetic oils. These are exemplified by the oils prepared through polymerization of alkylene oxides such as ethylene oxide or propylene oxide, and the alkyl and aryl ethers of these polyoxyalkylene polymers (e.g., methyl polyisopropylene glycol ether having an average molecular weight of about 1000, diphenyl ether of polyethylene glycol having a molecular weight of about 500 to about 1000, diethyl ether of polypropylene glycol having a molecular weight of about 1000 to about 1500) or mono- and poly-carboxylic esters thereof, for example, the acetic acid ester, mixed about C₃to about C₆fatty acid esters, or the C₁₃Oxo acid diester of tetraethylene glycol.
Another suitable class of synthetic oils comprises the esters of dicarboxylic acids (e.g., phthalic acid, succinic acid, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer) with a variety of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol). Specific examples of these esters include dibutyl adipate, di(2-ethylhexyl)adipate, didodecyl adipate, di(2-ethylhexyl)sebacate, dilauryl sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, di(eicosyl)sebacate, the 2-ethylhexyl diester of linoleic acid dimer, and the complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycol and two moles of 2-ethylhexanoic acid.
Esters which may be used as synthetic oils also include those made from about C₃to about C₁₂monocarboxylic acids and polyols and polyol ethers such as neopentyl glycol, trimethylolpropane, pentaerythritol and dipentaerythritol. Trimethylol propane tripelargonate and pentaerythritol tetracaproate serve as examples.
Silicon-based oils such as the polyalkyl-, polyaryl-, polyalkoxy-, or polyaryloxy-siloxane oils and silicate oils comprise another class of synthetic lubricants (e.g., tetraethyl silicate, tetraisopropyl silicate, tetra-(2-ethylhexyl) silicate, tetra-(p-tert-butylphenyl) silicate, poly(methyl)siloxanes, and poly(methylphenyl)siloxanes. Other synthetic lubricating oils include liquid esters of phosphorus-containing acids (e.g., tricresyl phosphate, trioctyl phosphate, triphenyl phosphite, and diethyl ester of decane phosphonic acid.
Also useful as base oils or as components of base oils are hydrogenated or unhydrogenated liquid oligomers of about C₆to about C₁₆α-olefins, such as hydrogenated or unhydrogenated oligomers formed from 1-decene. 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. 3,749,560; 3,763,244; 3,780,128; 4,172,855; 4,218,330; and 4,950,822; the disclosures of which are incorporated herein by reference. Blends of such materials can also be used in order to adjust the viscometrics of the given base oil. As is well known, hydrogenated oligomers of this type contain little, if any, residual ethylenic unsaturation.
Suitable oligomers may be formed by use of a Friedel-Crafts catalyst (especially boron trifluoride promoted with water or a about C₁to about C₂₀alkanol) 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.
It is also possible in accordance with this disclosure to utilize blends of one or more liquid hydrogenated 1-alkene oligomers in combination with other oleaginous materials having suitable viscosities, provided that the resultant blend has suitable compatibility and possesses the physical properties desired.
The base oil may be an oil derived from Fischer-Tropsch synthesized hydrocarbons, a gas-to-liquid stock, and/or a mixture thereof. Fischer-Tropsch synthesized hydrocarbons are made from synthesis gas containing H₂and CO using a Fischer-Tropsch catalyst. Such hydrocarbons typically require further processing in order to be useful as the base oil. For example, the hydrocarbons may be hydroisomerized using processes disclosed in U.S. Pat. No. 6,103,099 or 6,180,575; hydrocracked and hydroisomerized using processes disclosed in U.S. Pat. No. 4,943,672 or 6,096,940; dewaxed using processes disclosed in U.S. Pat. No. 5,882,505; or hydroisomerized and dewaxed using processes disclosed in U.S. Pat. No. 6,013,171; 6,080,301; or 6,165,949.
Typical natural oils that may be used as base oils or as components of the base oils include castor oil, olive oil, peanut oil, rapeseed oil, corn oil, sesame oil, cottonseed oil, soybean oil, sunflower oil, safflower oil, hemp oil, linseed oil, tung oil, oiticica oil, jojoba oil, and the like. Such oils may be partially or fully hydrogenated, if desired.
The fact that the base oils used in the compositions of this disclosure may be composed of (i) one or more mineral oils, (ii) one or more synthetic oils, (iii) one or more natural oils, or (iv) a blend of (i) and (ii), or (i) and (iii), or (ii) and (iii), or (i), (ii) and (iii) does not mean that these various types of oils are necessarily equivalents of each other. Certain types of base oils may be used in certain compositions for the specific properties they possess such as high temperature stability, nonflammability or lack of corrosivity towards specific metals (e.g. silver or cadmium). In other compositions, other types of base oils may be suitable for reasons of availability or low cost. Thus, the skilled artisan will recognize that while the various types of base oils discussed above may be used in the various embodiments, they are not necessarily functional equivalents of each other in every instance.
The Method of Use
The additive compositions and/or lubricating fluids of the present disclosure may be employed in a method for lubricating an automatic transmission, and, more specifically, in a method for lubricating a DCT, such as, a DCT that utilizes plural wet clutches and no torque converter.
The method of the present disclosure involves lubricating a transmission with a lubricating fluid comprising:

- (a) an ashless dispersant;
- (b) a friction-modifying amount of a friction modifier; and
- (c) a phosphonate.
  The fluid is substantially zinc-free and may deliver improved steel-on-steel friction, stabilized steel-on-paper friction and/or good synchronizer performance.

EXAMPLES

Fluids for testing were prepared in targeted basestocks. The fully formulated fluids were prepared by adding components together in proportions shown below:

	TABLE 1


	Antiwear/Extreme Pressure	0.05-1.0%
	Agents
	Antioxidants	0.1-0.6%
	Rust Inhibitors	0.01-0.2%
	DMOP	0.10-0.6%
	Antifoam agents	0.01-0.1%
	Friction Modifier	0.3-1.0%
	Dispersant A	1-6%
	Seal Swell Agents	0-10%
	Polymethacrylate VII	3-25%
	Basestock	60-90%
	Diluent Oil	2-5%

Dispersants used are succinimide dispersants that may or may not contain boron and/or phosphorus. The friction modifier was a succinimide having a C₁₈-C₂₄alkenyl group. DMOP is dimethyl octadecylphosphonate. Additional friction modifiers may be used to tailor friction requirements.

Dispersant and friction modifiers provide appropriate torque capacity. Fluid compositions containing dispersant and succinimide friction modifiers have been developed to provide good friction durability. FIG. 1 is a comparison of the friction characteristics of Fluid A (Table 2) containing succinimide dispersant and succinimide friction modifier with friction characteristics before and after thermal aging.

Thermal aging was carried out by heating the fluid in a round bottomed flask equipped with a mechanical stirrer at 160° C. for 192 hours. It may be seen that the fluid is able to withstand thermal stress as the thermally stressed fluid displays good friction durability and maintains both friction level and slope characteristics that are comparable to fresh fluid.

TABLE 2


Composition of Fluid A

Component	Amount, wt %

Antioxidant	0.1-0.5
Detergent	0.1-0.6
Rust Inhibitor(s)	0-0.2
Antiwear/Extreme Pressure Agent	0.05-1.0
Lubricity Agent(s)	0.1-1.0
Anti-foam Agent(s)	0.02-1.0
Amine Friction Modifier 1	0.02-0.15
Amine Friction Modifier 2	0.02-0.1
Succinimide Friction Modifier	0.1-0.8
Borated, Phosphorylated Succinimide Dispersant	2.00-7.5
Ethoxylated Alcohol	0.01-0.5
Process Oil	0.10-1.50
Base Oil	to 100%
Total	100.0

The detergent employed in the composition was an overbased C₁₄-C₂₄α-olefin calcium sulfonate detergent. The friction modifier was a succinimide having a C₁₈-C₂₄alkenyl group. DMOP is dimethyl octadecylphosphonate. The friction modifier in combination with DMOP gives excellent synchronizer performance.
A matrix of fluids (Table 3) comprising two types of antiwear, dispersant, friction modifier and basestock showed that the same friction modifier/DMOP combination in a synthetic fluid can give excellent synchronizer performance giving 100,000 cycles in the SSP-180 synchronizer test using brass cones.

The SSP-180 test stand was developed in the Gear Research Institute at the Technical University of Munich. It allows mounting and testing of a complete synchronizer device (up to 180 mm in diameter) from a manual transmission of choice. Load conditions associated with normal transmission use are simulated during the test. The test stand consists of an electric motor, two flywheels, actuating hydraulics, an oil heating and circulation system, and a test box. The large main flywheel is connected to the electric motor via a belt-and-pulley combination to ensure a constant and stable speed source. The small flywheel is the load that the synchronizers either bring to zero speed (shift to “A” position) or accelerate to a constant speed (shift to “B” position). This is accomplished by the two ring-and-cone synchronizers mounted in the test box. The rear unit accelerates the load flywheel to synchronous speed, while the forward unit decelerates the flywheel to zero speed. The actuating hydraulics move a shift fork that engages one unit and disengages the other. During shifting, heated lubricant is sprayed onto both synchronizer units. Subjecting these units to thousands of engagements serves to test synchronizer durability (adapted from http://www.swri.org/3PUBS/BROCHURE)

TABLE 3


Synchronizer Performance of Fluids containing Friction Modifier/DMOP

Matrix

	1	2	3	4	5	6	7	8

Base Oil	Synthetic	Mineral	Mineral	Synthetic	Synthetic	Mineral	Synthetic	Mineral
GO-	1100	1200	1300	1400	1500	1600	1700	1800
10631-
AW	ZDDP	Phosphorous	ZDDP	ZDDP	Phosphorous	ZDDP	Phosphorous	Phosphorous
		Acid			Acid		Acid	Acid
AW Level	1500	1500	1500	300	1500	300	300	300
Dispersant	Succinimide	Borated	Borated	Borated	Succinimide	Succinimide	Borated	Succinimide
	Dispersant	Succinimide	Succinimide	Succinimide	Dispersant	Dispersant	Succinimide	Dispersant
		Dispersant	Dispersant	Dispersant			Dispersant
Dispersant	0.5	0.5	5	5	5	0.5	0.5	5
level
Detergent	1.5	1.5	0.35	1.5	0.35	0.35	0.35	1.5
level
	Ethoxylated						Ethoxylated	Ethoxylated
	Amine	Succinimide		Succinimide	Succinimide	Succinimide	Amine	Amine
	Friction	Friction		Friction	Friction	Friction	Friction	Friction
FM type	Modifier	Modifier + DMOP	ATF	Modifier +	Modifier +	Modifier +	Modifier	Modifier
				DMOP	DMOP	DMOP
Base Oil	Synthetic	Mineral	Mineral	Synthetic	Synthetic	Mineral	Synthetic	Mineral
Cycles	83,278	67,077	21,157	100,000	100,000	100,000	49,327	43,867
Avg	0.785	1.0565	1.17	0.615	0.3565	0.4365	0.975	0.995
Wear
High	1.107	1.1	1.1785	0.72	0.437	0.49	1.06	1.28
Wear
Avg	0.093	0.077	0.08	0.0875	0.109	0.0945	0.0815	0.098
COF
Low	0.084	0.064	0.068	0.084	0.106	0.094	0.066	0.09
COF
Avg Sp	0.094	0.158	0.553	0.062	0.036	0.044	0.198	0.227
Wear
Max Sp	0.133	0.151	0.561	0.072	0.044	0.049	0.215	0.292
Wear

In addition to contributing to good synchronizer performance and antiwear protection in the synchronizer test, DMOP also provided excellent extreme pressure performance as measured using the Falex EP (Extreme Pressure) and 4-Ball EP tests according to ASTM D-3233 and D-2783 respectively. ASTM D-3233 performance is measured by determining the threshold load at which the test surfaces seize due to the applied load at a given temperature. ASTM D-2783 measures the Weld point of a steel ball rotated against 3 stationary balls. Table 4 shows improved performance at 0.25% of DMOP compared to a similar composition without DMOP.

TABLE 4


	Falex EP D-3233	Falex EP D-3233
	Fail load (lbs)	Fail load (lbs)	4-Ball EP
DMOP (wt. %)	@ 100° C.	@ 150° C.	ASTM D-2783

0.25	2125	2000	260 Kg Weld
0.00	1250	1000	210 Kg Weld

As used throughout the specification and claims, “a” and/or “an” may refer to one or more than one. Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, percent, ratio, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and claims are approximations that may vary depending upon the desired properties sought to be obtained by the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
While the present disclosure has been described in some detail by way of illustration and example, it should be understood that the embodiments are susceptible to various modifications and alternative forms, and are not restricted to the specific embodiments set forth. It should be understood that these specific embodiments are not intended to limit the invention but, on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Claims

1. A method of lubricating a dual clutch transmission with a lubricating fluid comprising the step of lubricating a dual clutch transmission with a substantially zinc-free lubricating fluid comprising:

(a) an ashless dispersant;

(b) a friction modifier;

(c) a phosphonate; and

(d) a base oil.

2. The method of claim 1, wherein the base oil comprises a natural lubricating oil, a mixture of natural lubricating oils, a synthetic oil, a mixture of synthetic oils, or a mixture of natural and synthetic oils.

3. The method of claim 1, wherein the dispersant comprises boron.

4. The method of claim 3, wherein the boron-containing dispersant comprises from about 0.1 wt % to about 0.7 wt % of boron.

5. The method of claim 1, wherein the dispersant comprises phosphorous.

6. The method of claim 1, wherein the dispersant comprises phosphorous and boron.

7. The method of claim 6, wherein the dispersant comprises up to about 400 ppm total phosphorous and boron.

8. The method of claim 1, wherein the phosphonate is selected from the group consisting of phosphonates having the formula:

wherein R¹is an alkyl or alkenyl group containing about 12 to about 30 carbon atoms and wherein R²and R³are each independently hydrogen, an alkyl, or an alkenyl group.

9. The method of claim 8, wherein the phosphonate is selected from the group consisting of dimethyl triacontylphosphonate, dimethyl triacontenylphosphonate, dimethyl eicosylphosphonate, dimethyl hexadecylphosphonate, dimethyl hexadecenylphosphonate, dimethyl tetracontenylphosphonate, dimethyl hexacontylphosphonate, dimethyl dodecylphosphonate, dimethyl dodecenylphosphonate, dimethyl hexadecylphosphonate, dimethyl hexadecenylphosphonate, dimethyl octadecylphosphonate, dimethyl octadecenylphosphonate, and dimethyl eicosylphosphonate.

10. The method of claim 8, wherein the phosphonate is selected from the group consisting of phosphonates wherein R¹is an alkyl or alkenyl group containing about 16-20 carbon atoms.

11. The method of claim 8, wherein the phosphonate comprises dimethyl octadecylphosphonate

12. The method of claim 1, wherein the lubricating composition comprises from about 0.05 to about 3 wt % of the phosphonate, based on the total weight of the lubricating composition.

13. The method of claim 1, wherein the shifting of gears in the dual clutch transmission comprises synchronization of an engaged and a non-engaged partial transmission shaft.

14. The method of claim 1, wherein the lubricating fluid further comprises at least one sulfur-containing compound.

15. A dual clutch transmission fluid comprising:

(a) an ashless dispersant;

(b) a friction modifier;

(c) a phosphonate; and

(d) a base oil,

wherein the dual clutch transmission fluid is substantially zinc-free.

16. The transmission fluid of claim 15, wherein the base oil comprises a natural lubricating oil, a mixture of natural lubricating oils, a synthetic oil, a mixture of synthetic oils, or a mixture of natural and synthetic oils.

17. The transmission fluid of claim 15, wherein the dispersant comprises boron.

18. The transmission fluid of claim 17, wherein the boron-containing dispersant comprises from about 0.1 wt % to about 0.7 wt % of boron.

19. The transmission fluid of claim 15, wherein the dispersant comprises phosphorous.

20. The transmission fluid of claim 15, wherein the dispersant comprises phosphorous and boron.

21. The transmission fluid of claim 20, wherein the dispersant comprises up to about 400 ppm total phosphorous and boron.

22. The transmission fluid of claim 15, wherein the phosphonate is selected from the group consisting of phosphonates having the formula:

23. The transmission fluid of claim 22, wherein the phosphonate is selected from the group consisting of dimethyl triacontylphosphonate, dimethyl triacontenylphosphonate, dimethyl eicosylphosphonate, dimethyl hexadecylphosphonate, dimethyl hexadecenylphosphonate, dimethyl tetracontenylphosphonate, dimethyl hexacontylphosphonate, dimethyl dodecylphosphonate, dimethyl dodecenylphosphonate, dimethyl hexadecylphosphonate, dimethyl hexadecenylphosphonate, dimethyl octadecylphosphonate, dimethyl octadecenylphosphonate, and dimethyl eicosylphosphonate.

24. The transmission fluid of claim 22, wherein the phosphonate is selected from the group consisting of phosphonates wherein R¹is an alkyl or alkenyl group containing about 16-20 carbon atoms.

25. The transmission fluid of claim 22, wherein the phosphonate comprises dimethyl octadecylphosphonate

26. The transmission fluid of claim 15, wherein the lubricating composition comprises from about 0.05 to about 3 wt % of the phosphonate, based on the total weight of the lubricating composition.

27. The transmission fluid of claim 15, wherein the lubricating composition further comprising at least one sulfur-containing compound.