60/108,592, filed November 16,1998.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to complex alcohol ester compounds and compositions that are soluble in basestocks and to lubricants and other compositions made therefrom.

2. Description of the Related Art Commercial lubricants are generally comprised of one or more basestocks, various additives, and optionally solvents. Basestocks include natural basestocks such as mineral oils and vegetable oils, and synthetic basestocks such as poly alpha olefins (PAOs), polyalkylene glycols, phosphate esters, silicone oils, and carboxylic acid esters. Much attention has been directed to synthetic basestocks in an effort to improve performance characteristics over natural basestocks. For example, mineral oil was found to be insufficient to accommodate the extreme temperature variations encountered in aircraft turbine engines. Synthetic basestocks were developed that could withstand the high temperatures and still provide a sufficiently low pour point.

Other characteristics to be considered included lubricity, viscosity and oxidation-

corrosion resistance. Synthetic basestocks have been used in engine lubricants as the entire basestock and/or as an additive or co-basestock. The latter can be advantageous in that synthetic basestocks are normally more expensive to produce than natural basestocks. Using a blend of basestocks can sometimes achieve the improved synthetic basestock properties with only a minimal increase in cost.

One class of synthetic basestocks that has been found to be advantageous is complex esters. A complex ester is generally an ester that is formed from a polyhydric alcohol, a polybasic acid and either a monoacid or a monoalcohol. One kind of complex ester is disclosed in U. S. Patent 3,086,044. In this patent, a complex ester is made by first reacting a diol with a diacid and subsequently adding a large excess of monoalcohol as a chain stopping agent. The use of excess monoalcohol is taught to change the physical characteristics of the complex ester, even though added as a second reaction step, and is suggested as preventing the development of long ester repeating chains. Another diol based complex ester is disclosed in U. S. Patent 3,377,377. This patent recites reacting a mixture of polyethylene glycol and polypropylene glycol with a diacid and an alkanol. This complex ester is taught to exhibit superior properties over complex esters made from either glycol alone. The complex esters are described as suitable for use as lubricants alone or in blends and are particularly useful in high flying aircraft where very low temperatures are encountered for prolonged periods of time.

More recently, U. S. Patent 5,750,750, described a complex ester that is useful as a basestock for various lubricants. The complex esters described are prepared by

reacting a polyhydric alcohol, a polybasic acid or anhydride thereof, and a monohydric alcohol wherein the ratio of alcohol equivalents to acid equivalents does not exceed 1.2: 1. The examples include neopentyl glycol, trimethylol propane, and pentaerythritol as the polyols. A preferred complex ester is taught to be formed by reacting trimethylol propane, adipic acid, and isodecyl alcohol which results in an ester composition having high viscosity, high viscosity index, and good biodegradability.

These esters described in U. S. 5,750,750, especially the aforementioned preferred ester composition, exhibit excellent lubricity and are particularly well suited for use as the basestock in engine oils for reducing wear and increasing fuel efficiency.

However, complex esters having a triol or higher polyhydric alcohol residue such as those exemplified in the U. S. 5,750,750 patent are not soluble in other less expensive basestocks. That is, combining small amounts of these complex esters with mineral oil or PAO results in a two phase composition. This two phase phenomenon is generally perceived as being commercially unacceptable. To avoid two phases, larger amounts of the complex ester may be used. Apparently, at higher concentrations, i. e. greater than 50 or 70 wt %, the other basestocks become dissolved in the complex ester thereby forming the desired single phase composition. But, the complex esters are generally effective at much lower concentrations. It would be desirable to provide the advantages of fuel efficiency and reduced wear derived from complex esters, such as the complex esters taught in U. S. 5,750,750, in a soluble form so as to be able to provide a one phase mixture with other basestocks even at low concentrations such 5 to 25 wt %.

SUMMARY OF THE INVENTION The present invention relates to a soluble ester composition comprising 100 parts by weight of a complex alcohol ester component and 0-2000 parts by weight of a co-solvent, wherein the composition exhibits continuous solubility up to 15 wt % in mineral oil. The complex alcohol ester component is made up of one or more triol or higher polyhydric complex alcohol esters (as is defined hereinafter). Generally the solubility performance is achieved by controlling the number and kind of complex esters contained in the complex alcohol ester component or by employing a suitable co-solvent (s) or a combination thereof. Typically, the triol or higher polyhydric complex alcohol ester contains the residue of a triol, particularly trimethylol propane, a dibasic acid and a monohydric alcohol. In one embodiment, the monohydric alcohol is preferably a C13 alcohol such as iso-tridecyl alcohol and the dibasic acid is adipic acid.

In another embodiment, the complex alcohol ester component has a carbon: oxygen weight ratio of at least 4.2: 1. This ratio can be attained by using, for example, higher molecular weight dibasic acids. Accordingly, the use of a mixture of adipic acid and dimeric oleic acid can provide good solubility. Alternatively, the selection and/or amount of co-solvent can also render the overall composition fully soluble. In this embodiment, ester co-solvents such as polyol esters having a hydroxyl number of at least 5 can be advantageously employed. Other ester co-solvents include full esters such as phthalates, adipates and polyol esters.

The present invention also relates to novel complex alcohol esters per se and to a distribution of such esters and higher homologues and/or partial esters thereof.

Furthermore, the present invention relates to a lubricant composition that contains the soluble composition of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a composition that contains a complex alcohol ester component and optionally a co-solvent. The term"complex alcohol ester component"as used herein collectively refers to all triol or higher polyhydric complex alcohol esters contained in the composition, be it a single species or a plurality of species. A"triol or higher polyhydric complex alcohol ester"as used herein means a compound having a plurality of ester moieties and containing the residues of a triol or higher polyhydric alcohol compound, a polybasic acid compound and a monohydric alcohol. That is, the triol or higher polyhydric complex alcohol ester is the result of esterifying the polyhydric alcohol compound, the polybasic acid compound and the monohydric alcohol to form a complex alcohol ester comprised of the corresponding residues. The complex alcohol ester component contains only these kind of complex alcohol esters. Other kinds of complex alcohol esters such as those made from a diol are not included within the definition of the"complex alcohol ester component." Similarly, other kinds of esters, even if co-formed during the esterification reaction, e. g., ester compound of polybasic acid and monoalcohol such as an adipate, are not included within the scope of"complex alcohol ester component."Both of these kinds of esters may be present in the soluble composition, such as in the form of a co- solvent, but are simply not included within the complex alcohol ester component. In

short, the"component"embraces all the triol or higher polyhydric complex alcohol esters and only the triol or higher polyhydric complex alcohol esters contained in the soluble composition.

For completeness, the triol or higher polyhydric complex alcohol esters may also contain a diol residue in addition to the triol or higher polyhydric alcohol residue.

That is, a single complex alcohol ester compound that contains both an esterified triol residue and a esterified diol residue therein is considered to be a"triol or higher polyhydric complex alcohol ester"in as much as this species contains a triol or higher polyhydric alcohol residue. Such mixed polyols are, however, generally not preferred.

The esterification reaction that forms the triol or higher polyhydric complex alcohol ester (s) usually produces a range of complex alcohol ester products depending in part on the molar feed ratios. These products may include partial esters, full monomers, dimers, trimers and other higher homologues, owing to the multivalent acid and hydroxyl compounds. As used herein, a monomer of any complex alcohol ester, hereinafter simply"monomer,"corresponds to a polyhydric alcohol having each hydroxyl group esterified with a polybasic acid and the remaining acid moieties on each of these polybasic acids being esterified with a monohydric alcohol. That is, the polybasic acids are end capped by reaction with the monohydric alcohols. In this regard, the monohydric alcohol can be thought of as a chain stopping agent to prevent or retard oligomerization ; i. e. the formation of dimers, trimers, etc. Dimers, trimers and other higher homologues are formed when a polybasic acid is esterified with two or more polyhydric alcohols, instead of with one polyhydric alcohol and one

monohydric alcohol. Thus, while a monomer contains one polyhydric alcohol residue, a dimer contains two polyhydric alcohol residues, a trimer three and so on. A partial ester is a monomer or higher homologue thereof where one or more of the hydroxyl groups of the polyhydric alcohol is not esterified. The complex alcohol ester component can contain the entire distribution of monomer, dimer, trimer, partial esters, etc., of the tnol or higher polyhydric complex alcohol ester formed in the esterification reaction, or, one or more fractions thereof.

The soluble composition of the present invention exhibits continuous solubility up to 15 wt % in mineral oil. The phrase"continuous solubility up to 15 wt%"means that at all treat rates from greater than zero up to and including 15 wt % the composition is soluble in the recited basestock. Here the wt % represents the amount of the composition added based on the amount of basestock as being 100%. A composition that is continuously soluble up to 15 wt % is soluble across the entire concentration range from 0 to 15 wt %, and not merely at a portion of the range.

Conversely, the 15 wt % should not be taken as an upper limit on the solubility. That is, the composition may well be, and usually is, soluble above 15 wt % if it is continuously soluble up to 15 wt %. Indeed, frequently complex esters that are insoluble at lower concentrations become soluble at higher concentrations, presumably because the basestock becomes dissolved in the complex ester. Thus, complex esters can be insoluble at a concentration of 5 wt %, but soluble/miscible at 30 wt %.

The composition is considered"soluble"if it passes the following test. The composition and specified basestock are added at room temperature (approximately

23°C) to a four ounce glass jar and the cap secured thereon. The jar is shaken vigorously for about one minute and then placed at rest and observed. If after ten minutes at rest the liquid inside the jar remains in one phase, then the composition is soluble. If two phases are observable within the ten minutes, then the composition is not soluble. Preferably the soluble composition of the present invention remains in a single phase for at least one hour, more preferably for at least 24 hours at all concentrations, up tol5 wt %. Also, the soluble composition is preferably continuously soluble in PAO 6 (poly alpha hexylene), more preferably PAO 4 (poly alpha butylene), up to 15 wt % and it is further preferred that the composition maintain a single phase for at least one hour and more preferably for at least 24 hours in the prescribed test.

It has now been discovered that a composition can be formulated that exhibit the above-recited solubility by controlling the structure of the complex alcohol esters and/or the co-solvent supplied therewith. Triol or higher polyhydric complex alcohol esters are more soluble in mineral oil and other basestocks when they are rendered less polar; i. e. the dielectric constant for the ester molecule is reduced. Thus, limiting the growth of oligomers and providing mostly monomer and dimer forms of the complex ester reduces the molecular weight and increases the solubility of the ester compound.

However, increasing the molecular weight of the individual monomer such as by lengthening the monoalcohol chain, also generally increases solubility. Further, branching tends to reduce solubility while linearity tends to increase solubility. The former generally increases polarity while the latter generally decreases polarity. By

taking these phenomena into account, a complex alcohol ester component can be produced that exhibits good solubility.

Alternatively, forming a complex alcohol ester component that has a carbon to oxygen weight ratio of at least 4.2: 1, preferably 4.7-10.5: 1, more preferably 5-10: 1, also improves solubility in basestocks. Unexpectedly, the complex alcohol ester component exhibit solubility in mineral oil and other hydrocarbon solvents above a C: O weight ratio of 4.2: 1. This can be most easily achieved by lengthening the carbon chain of the dibasic acid residue. For example, by using a dibasic acid mixture of adipic acid and dimerized oleic acid or other unsaturated fatty acid, the average chain length of the dibasic acid residue is increased, thereby increasing the C: O weight ratio.

The C: O weight ratio can also be increased by lengthening the monoalcohol carbon chain.

In more detail, the polyhydric alcohols suitable for use in forming triol and higher polyhydric complex alcohol esters to be used in the complex alcohol ester component include those represented by the formula R (OH) n wherein R is an aliphatic or cycloaliphatic hydrocarbyl group having 3 to 25 carbon atoms and n is at least 3 and generally not more than the number of carbon atoms in R. Typically n is 3-5 and more preferably 3. The"hydrocarbyl group"is a hydrocarbon group that may be substituted or interrupted by a chlorine, nitrogen and/or oxygen atoms. Accordingly compounds containing oxyalkylene groups such as polyetherpolyols are included within the meaning of the above formula. Preferably, R is an unsubstituted, branched or straight chain hydrocarbon group having 4 to 20 carbon atoms. More preferably, R is a neo-

hydrocarbon group and the polyhydric alcohol is a neo-triol. Examples of suitable polyhydric alcohols include trimethylol ethane, trimethylol propane, trimethylol butane, mono-pentaerythritol, di-pentaerythritol technical grade pentaerythritol (approximately 88% mono-, 10% di-, and 1-2% tri-pentaerythritol) and mixtures thereof. The most preferred polyhydric alcohol is trimethylol propane.

The polybasic acids are generally aliphatic acids having 2 to 36 carbon atoms and two or more carboxylic acid groups, or the anhydride thereof. Preferably the polybasic acid is a diacid, a dimer acid, or a mixture thereof. Diacids include adipic acid, azelaic acid, sebacic acid, and dodecandioic acid. The preferred diacid is adipic acid. Dimer acids are acids that result from dimerization of unsaturated fatty acids having 12 to 19 carbon atoms and optionally hydrogenated to remove any remaining unsaturation. The preferred dimer acid is a dimer of oleic acid. In most embodiments, adipic acid is used either alone or in combination with other polybasic acids. When a mixture of diacids and dimer acids is used, the proportion of dimer acid in the polybasic acid feed can vary over a broad range, but typically is at least 5 mol % and not more than 80 mol %, more preferably 5 to 50 mol %. The resulting triol or higher polyhydric complex alcohol esters typically contain the dimer acid residue in an amount of 5 to 75 mol % of the polybasic acid residues.

The monohydric alcohol used in the present invention includes alcohols having 2 to 18 carbon atoms. Branched alcohols having 5-18 carbon atoms are preferred in some embodiments. Examples of suitable monohydric alcohols include n-pentyl alcohol, iso-pentyl alcohol, n-heptyl alcohol, iso-heptyl alcohol, n-octyl alcohol, iso-

octyl alcohol, 2-ethyl hexyl, n-nonyl alcohol, iso-nonyl alcohol, n-decyl alcohol, iso- decyl alcohol, tridecyl alcohol, and stearyl alcohol. In general, the monohydric alcohol is preferred to have 8-18 carbon atoms. Iso-decyl alcohol and tridecyl alcohol are frequently preferred.

Preferably, the complex alcohol ester component is comprised of, and is more preferably only comprised of, triol complex alcohol ester (s) represented by Formula I, Formula II, higher homologues thereof, partial esters thereof, or combinations thereof.

R'represents a Cl-C5 straight or branched chain alkyl group; R2-R4 each independently represent a C2-CI8 straight or branched chain alkyl group; and n, m, and p each independently represent a number from 2 to 38. Generally R2-R4 are the same and represent a Cs-Cis straight or branched chain alkyl group. Formula I is a triol complex alcohol ester monomer and Formula II is a dimer thereof. Trimer and higher oligomeric forms of Formula I correspond to the"higher homologues thereof"The partial esters include partial esters of the monomer, dimer and higher homologues. An example of a partial ester, namely one class of partial esters of the monomer, is set forth below as Formula III.

R'-R3, n, and m each have the same meaning as set forth above in Formulas I and II. It should be understood that the partial esters are not limited to the particular structure of Formula III as other partial esters of the monomer as well as partial esters of the dimer or higher homologues are all included within the term"partial esters thereof." One embodiment of the invention uses a triol complex alcohol ester of the following Formula IV in the complex alcohol ester component.

The complex alcohol ester component preferably comprises about 40 to 60 wt % of the monomer of Formula IV and about 10 to 35 wt % of the corresponding dimer of the compound of Formula IV. The ester of Formula IV can be obtained by reacting together trimethylol propane, adipic acid and tridecyl alcohol. As is described in more detail hereinafter, the esterification reaction can be conducted to provide a composition containing about 80 wt % ditridecyladipate, about 10 wt % of the complex alcohol ester of Formula IV, about 5 wt % of the dimer thereof, about 2 wt % of the various partial esters thereof, and about 3 wt % of trimer and higher homologues. This composition, having about 400 parts by weight of a co-solvent (ditridecyladipate) and 100 parts by weight of a complex alcohol ester component, is continuously soluble in mineral oil up to 15 wt % and thus corresponds to a soluble composition of the present invention. Further, a portion of the adipate co-solvent present in the reaction product can be stripped off, such as 20 wt % thereof, without significantly affecting the solubility of the composition. If desired, the complex alcohol ester component can be isolated and used by itself as the soluble composition; i. e., zero parts of a co-solvent. The complex alcohol ester component can also be

combined with a different or additional co-solvent. Similarly, a fraction of the complex alcohol ester component, especially the monomer and, optionally, the dimer, can be isolated and used as a complex alcohol ester component, with or without a co- solvent.

The co-solvent that is optionally present in the soluble composition is not particularly limited and is generally any organic solvent, or a combination thereof, that is compatible with the complex alcohol ester component. Although referred to as a "co-solvent"it is not necessary that the co-solvent provide any meaningful or additional mineral oil solubility to the composition. In some instances, however, the co-solvent does serve as a solubility aide for the complex alcohol ester component.

The co-solvent can be added to the complex alcohol ester component or it may be formed in situ during the esterification of the complex alcohol ester component as described above with regard to the formation of the ester of Formula IV. Frequently, the co-solvent is simply the non-complex ester formed concurrently with the intended triol or higher polyhydric complex alcohol ester.

Typically the co-solvent is a hydrocarbon solvent, such as toluene, benzene, xylene, a solvent neutral oil, or an ester, especially a polyol ester or a diacid ester.

Preferably the co-solvent is an ester selected from the group of phthalates, adipates, and polyol esters. For phthalates, the carbon chain corresponding to the monoalcohol residue in the co-solvent ester typically has a carbon number in the range between about C6 to C13. A preferred phthalate is diisodecyl phthalate.

The polyol esters may be fully esterified or they may be partially esterified. In one embodiment, a high hydroxyl polyol ester having a hydroxyl number of at least 5, preferably 5-150, more preferably 5-100, is used as the co-solvent. Preferred high hydroxyl esters are described in U. S Patents 5,665,686 and 5,692,502, the entire contents of which are incorporated herein by reference. These synthetic esters exhibit thermal and oxidative stability and comprise the reaction product of: a branched or linear alcohol having the general formula R (OH) n, wherein R is an aliphatic or cyclo- aliphatic group having from about 2 to 20 carbon atoms and n is at least 2; and at least one branched and/or linear acid which has a carbon number in the range between about C4 to C20; wherein the synthetic ester composition has a hydroxyl number between about greater than 5 to 150 depending upon the acid and polyol used (e. g., 1 to 25% unconverted hydroxyl groups, based on the total amount of hydroxyl groups in the branched or linear alcohol), preferably between about greater than 5 to 100 (e. g., 1 to 15% unconverted hydroxyl groups), and more preferably between about 10-80 (e. g., 2 to 10% unconverted hydroxyl groups).

The use of high hydroxyl esters can serve to solubilize the complex alcohol ester component and to increase the lubricity of the soluble composition or any lubricant containing the same. Specifically, under high load and low shear conditions, the complex alcohol ester component generally provides a reduced coefficient of friction while under low load and high shear the high hydroxyl ester provides a reduced coefficient of friction. The combination of these two esters thus provides for good lubricity under a wide variety of conditions.

A preferred complex alcohol ester component for use with the high hydroxyl ester co-solvents contains the triol complex alcohol ester of Formula V, higher homologues thereof, and partial esters thereof.

An example of a complex alcohol ester component containing the triol complex alcohol ester of Formula V is set forth in Example 1 of U. S. Patent 5,750,750. These complex alcohol ester components are advantageous in that they are biodegradable.

The added presence of a high hydroxyl ester as a co-solvent renders a soluble composition with mineral oil.

The most common co-solvent is the diacid ester, especially adipates. These esters can be readily formed simultaneously with the complex alcohol ester component. Adipic acid is commonly used as the polybasic acid in forming the triol or higher polyhydric complex alcohol esters. The adipic acid will also esterify with the monohydric alcohol present in the reaction medium to form adipates. The amount of adipates depends on the molar feed ratios of the various esterification reactants.

Adipates can also be added to the esterification reaction product (s) to provide a higher concentration and/or different adipate species.

The amount of co-solvent ranges from 0 to 2000 parts by weight per 100 parts of complex alcohol ester component. Typically, the amount of co-solvent ranges from 0 to 800, more preferably from 0 to 400 parts by weight per 100 parts by weight of complex alcohol ester component. When present, the co-solvent is typically present in amounts from 80 to 1000 parts by weight. In some embodiments, it is preferable to have 300 to 500 parts by weight of tridecyl adipate.

The triol or higher polyhydric complex alcohol esters can be produced by techniques known in the art in either a single step or two step method. Catalysts are typically used to achieve greater than 99% conversion of the acid functionality present.

Metal catalysts are preferred for several reasons, but have a disadvantage in that metallic residues are left in the final product after conventional removal techniques are used. This drawback is largely alleviated by either (1) adding the catalyst to the reaction when between about 88 to 92% conversion of the polybasic acid is achieved rather than at the start of the reaction or, preferably, (2) treating the crude esterification product with water in an amount of between about 0.5 to 4 wt %, based on crude esterification product, more preferably between about 2 to 3 wt %, at elevated temperatures of between 100 to 200°C, more preferably between about 110 to 175°C, and most preferably between about 125 to 160°C, and pressures greater than one atmosphere.

When it is desirable to use esterification catalysts, titanium, zirconium and tin- based catalysts such as titanium, zirconium and tin alcoholates, carboxylates and chelates are preferred. See U. S. Patent 3,056,818 and U. S. Patent 5,324,853 which

disclose various specific catalysts which may be used in the esterification process of the present invention and which are incorporated herein by reference. It is also possible to use sulfuric acid, phosphorus acid, sulfonic acid and para-toluene sulfonic acid as the esterification catalyst.

In general, the polyhydric and monohydric alcohols and the polybasic acid are charged to a reactor and heated. The esterification reaction produces water as steam and vaporized monohydric alcohol, both of which are taken overhead. The steam is stripped off from the reactor while the monohydric alcohol is generally condensed and returned to the reactor (refluxed), although in some embodiments the alcohol is not returned. The reaction is normally run until the acid number, determined by sampling the reaction product shows that the reaction is at or near completion in that nearly all of the acid moieties are esterified.

One preferred manufacturing process using a batch process is as follows: (1) charge a polyol, polybasic acid and monohydric alcohol into an esterification reactor: (2) raise the temperature of the reacting mass to around 220°C, while reducing vacuum to cause the alcohol present to boil and then separating water from the overhead vapor stream and returning alcohol to the reactor; (3) add tetraisopropyl titanate catalyst to the reacting mixture when 88 to 92% of the acid functionalities present in polybasic acid have been esterified; (4) continue reaction to about 95-99% conversion or other desired level of conversion of the acid functionalities present in polybasic acid; (5) stop the reaction by removing vacuum and heat; (6) carbon treat the product, if necessary to reduce its color; (7) hydrolyze the titanium catalyst in the

crude reactor product with about 0.5 to 4 wt. % water at a temperature in the range 100 to 200°C and a pressure of above 1 atmosphere; (8) filter the titanium catalyst residue and carbon, if present; and (9) strip unreacted excess monohydric alcohol from the crude product.

By using the above process, the amount of titanium in the product can be reduced to a level below 100 ppm. It is desirable that the titanium catalyst have as small a residence time as possible at reactor temperatures (ca. 220°C), that the minimum amount of titanium catalyst required to assure the required conversion levels be used, and that very effective contacting and mixing with the hydrolysis water solution employed to convert the organo titanium species into insoluble titanium dioxide is carried out.

Alternatively, if a product completely free of metals is desired, the process can be terminated prior to 99% conversion without the use of a metal catalyst. Generally the reaction can proceed to around 88% conversion or more, based on the acid groups, in a reasonable time period.

Making a complex alcohol ester component having a triol complex alcohol ester of Formula IV can be achieved using the above process by combining in a reactor trimethylol propane, adipic acid, and tridecyl alcohol. By adjusting the molar excess (es) of these reactants, the distribution of monomers, dimers and higher homologues can be shifted toward monomers or toward higher homologues.

Similarly, the amount of non-complex ester adipates formed in the reaction can also be controlled. Preferably, the monomers are formed and not higher homologues thereof.

To achieve this, the ratio of trimethylol propane to adipic acid is preferably 1: 6-12 and the ratio of adipic acid to tridecyi alcohol is 1: 1.7-2.2. Specifically preferred is the molar ratio of trimethylol propane: adipic acid: tridecyl alcohol of about 1: 8: 14.3. This ratio can produce a product having about 80 wt % ditridecyladipate and 20 wt % of a complex alcohol ester component comprised of about 10 wt % of the complex alcohol ester of Formula IV, about 5 wt % of the dimer thereof, about 2 wt % of the various partial esters thereof, and about 3 wt % of trimer and higher homologues, based on the total weight of the composition. This esterification reaction product can be used directly as the soluble composition of the present invention without the need to add any additional co-solvent. While the compound of Formula IV can be formed using other molar feed ratios of trimethylol propane, adipic acid and tridecyl alcohol, the presence of high amounts of higher homologues may render the reaction product insoluble. Further, while the monomer may be recoverable for use as a complex alcohol ester component, such involves an extra step that can be avoided by selecting more appropriate molar feed ratios.

The compounds of Formula V can be made by combining trimethylol propane, adipic acid and isodecyl alcohol at a molar feed ratio of 1: 2.5-5: 3-5.5. The amount of isodecyl alcohol should preferably bring the total excess of hydroxyl groups (trimethylol propane and isodecyl alcohol) to not more than 20 mol %, more preferably 5 mol % to 15 mol % excess hydroxyl groups based on the number of acid groups. A preferred molar ratio is about 1: 2.75: 3.03 to produce a composition having about 40 wt % diisodecyladipate as the co-solvent and 60 wt % complex alcohol ester

component. Unfortunately, this composition is not soluble. A soluble composition according to the present invention can be formed by adding an additional co-solvent such as a high hydroxyl ester. Alternatively, the triol complex alcohol esters can be modified by replacing part of the adipic acid with a dimer acid such a dimer of oleic acid, as discussed above.

The soluble composition of the present invention can be used in the formulation of crankcase lubricating oils (i. e., passenger car motor oils, heavy duty diesel motor oils, and passenger car diesel oils) for spark-ignited and compression- ignited engines. The preferred crankcase lubricating oil is typically formulated using the soluble composition containing the complex alcohol ester component and optionally a co-solvent blended with other conventional basestock oils, together with any conventional crankcase additive package. The soluble composition is usually used at a treat rate of from 1 to 25 wt %, commonly 5 to 25 wt %, more commonly from 5 to 15 wt % such as 5 to 10 wt %, based on the basestock as being 100%.

The additives listed below are typically used in such amounts so as to provide their normal attendant functions. Typical amounts for individual components are also set forth below. All the values listed are stated as mass percent active ingredient. ADDITIVE MASS % MASS % (Broad) (Preferred) AshlessDispersant 0. 1-20 1-8 Metaldetergents0. 1-150. 2-9 CorrosionInhibitor 0-5 0-1.5 Metaldihydrocarbyl dithiophosphate 0. 1-6 0.1-4 Supplemental anti-oxidant 0-5 0.01-1.5 Pour Point Depressant 0. 01-5 0.01-1.5 Anti-FoamingAgent 0-5 0.001-0.15 Supplemental Anti-wear Agents 0-0. 5 0-0.2 FrictionModifier 0-5 0-1.5 ViscosityModifier 0. 01-6 0-4 Synthetic Basestock Balance Balance

The individual additives may be incorporated into a basestock in any convenient way. Thus, each of the components can be added directly to the basestock by dispersing or dissolving it in the basestock at the desired level of concentration.

Such blending may occur at ambient temperature or at an elevated temperature.

Preferably, all the additives except for the viscosity modifier and the pour point depressant are blended into a concentrate or additive package described herein as the additive package, that is subsequently blended into basestock to make finished lubricant. Use of such concentrates is conventional. The concentrate will typically be formulated to contain the additive (s) in proper amounts to provide the desired concentration in the final formulation when the concentrate is combined with a predetermined amount of basestock.

The final crankcase lubricating oil formulation may employ from 2 to 15 mass % and preferably 5 to 10 mass %, typically about 7 to 8 mass % of the concentrate or additive package with the remainder being basestock.

One preferred method of forming the concentrate is the method described in U. S. Patent 4,938,880. That patent describes making a pre-mix of ashless dispersant and metal detergents that is pre-blended at a temperature of at least about 100°C.

Thereafter, the pre-mix is cooled to at least 85°C and the additional components are added.

The ashless dispersant comprises an oil soluble polymeric hydrocarbon backbone having functional groups that are capable of associating with particles to be dispersed. Typically, the dispersants comprise amine, alcohol, amide, or ester polar moieties attached to the polymer backbone often via a bridging group. The ashless dispersant may be, for example, selected from oil soluble salts, esters, amino-esters, amides, imides, and oxazolines of long chain hydrocarbon substituted mono and dicarboxylic acids or their anhydrides; thiocarboxylate derivatives of long chain hydrocarbons; long chain aliphatic hydrocarbons having a polyamine attached directly thereto; and Mannich condensation products formed by condensing a long chain substituted phenol with formaldehyde and polyalkylene polyamine.

Metal-containing or ash-forming detergents function both as detergents to reduce or remove deposits and as acid neutralizers or rust inhibitors, thereby reducing wear and corrosion and extending engine life. Detergents generally comprise a polar head with a long hydrophobic tail, with the polar head comprising a metal salt of an

acidic organic compound. The salts may contain a substantially stoichiometric amount of the metal in which case they are usually described as normal or neutral salts, and would typically have a total base number or TBN (as may be measured by ASTM D2896) of from 0 to 80. It is possible to include large amounts of a metal base by reacting an excess of a metal compound such as an oxide or hydroxide with an acidic gas such as carbon dioxide. The resulting overbased detergent comprises neutralized detergent as the outer layer of a metal base (e. g., carbonate) micelle. Such overbased detergents may have a TBN of 150 or greater, and typically of from 250 to 450 or more.

Detergents that may be used include oil-soluble neutral and overbased sulfonates, phenates, sulfurized phenates, thiophosphonates, salicylates, and naphthenates and other oil-soluble carboxylates of a metal, particularly the alkali or alkaline earth metals, e. g., sodium, potassium, lithium, calcium, and magnesium. The most commonly used metals are calcium and magnesium, which may both the present in detergents used in a lubricant, and mixtures of calcium and/or magnesium with sodium. Particularly convenient metal detergents are neutral and overbased calcium sulfonates having TBN of from 20 to 450 TBN, and neutral and overbased calcium phenates and sulfurized phenates having TBN of from 50 to 450.

The viscosity modifier (VM) functions to impact high and low temperature operability to a lubricating oil. The VM used may have that sole function, or may be multifunctional.

Multifunctional viscosity modifiers that also function as dispersants are also known. Suitable viscosity modifiers are polyisobutylene, copolymers of ethylene and propylene and higher alpha-olefins, polymethacrylates, polyalkylmethacrylates, methacrylate copolymers, copolymers of an unsaturated dicarboxylic acid and a vinyl compound, inter polymers of stryrene and acrylic esters, and partially hydrogenated copolymers of styrene/isoprene, styrene/butadiene, and isoprene/butadienc, as well as the partially hydrogenated homopolymers of butadiene and isoprene and isoprene/divinylbenzene.

Dihydrocarbyl dithiophosphate metal salts are frequently used as anti-wear and antioxidant agents. The metal may be an alkali or alkaline earth metal, or aluminum, lead, tin, molybdenum, manganese, nickel or copper. The zinc salts are most commonly used in lubricating oil in amounts of 0.1 to 10, preferably 0.2 to 2 wt. %, based upon the total weight of the lubricating oil composition. They may be prepared in accordance with known techniques by first forming a dihydrocarbyl dithiophosphoric acid (DDPA), usually by reaction of one or more alcohol or a phenol with P2S5, and then neutralizing the formed DDPA with a zinc compound. For example, a dithiophospohoric acid may be made by reacting mixtures of primary and secondary alcohols. Alternatively, multiple dithiophosphoric acids can be prepared where the hydrocarbyl groups on one sulfur are entirely secondary in character and the hydrocarbyl groups on the other sulfur are entirely primary in character. To make the zinc salt any basic or neutral zinc compound could be used but the oxides, hydroxides and carbonates are most generally employed. Commercial additives frequently contain

an excess of zinc due to use of an excess of the basic zinc compound in the neutralization reaction.

Oxidation inhibitors or antioxidants reduce the tendency of basestocks to deteriorate in service which deterioration can be evidence by the products of oxidation such as sludge and varnish-like deposits on the metal surfaces and by viscosity growth.

Such oxidation inhibitors include hindered phenols, alkaline earth metal salts of alkylphenolthioesters having preferably C5 to dz alkyi side chains, calcium nonylphenol sulfide, ashless oil soluble phenates and sulfurized phenates, phosphosulfurized or sulfurized hydrocarbons, phosphorous esters, metal thiocarbamates, oil soluble copper compounds, and molybdenum containing compounds.

Friction modifiers may be included to improve fuel economy. Oil-soluble alkoxylated mono-and diamines are well known to improve boundary layer lubrication. The amines may be used as such or in the form of an adduct or reaction product with a boron compound such as a boric oxide, boron halide, metaborate, boric acid or a mono-, di-or trialkyl borate.

Other friction modifiers are known. Among these are esters formed by reacting carboxylic acids and anhydrides with alkanols. Other conventional friction modifiers generally consist of a polar terminal group (e. g., carboxyl or hydroxyl) covalently bonded to an oleophilic hydrocarbon chain. Glycerol monooleate and the like are preferred for use. Esters of carboxylic acids and anhydrides with alkanols are described in U. S. Patent 4,702,850. Examples of other conventional friction modifiers

are described by M. Belzer in the"Journal of Tribology" (1992), Vol. 114, pp. 675- 682 and M. Belzer and S. Jahanmir in"Lubrication Science" (1988), Vol. 1, pp. 3-26.

Rust inhibitors selected from the group consisting of nonionic polyoxyalkylene polyols and esters thereof, polyoxyalkylene phenols, and anionic alkyl sulfonic acids may be used.

Copper and lead bearing corrosion inhibitors may be used, but are typically not required with the formulation of the present invention. Typically such compounds are the thiadiazole polysulfides containing from 5 to 50 carbon atoms, their derivaties and polymers thereof. Derivaties of 1,3,4 thiadiazoles such as those described in U. S.

Patents 2,719,125; 2,719,126; and 3,087,932; are typical. Other similar materials are described in U. S. Patents 3,821,236; 3,904,537; 4,097,387; 4,107,059; 4,136,043; and 4,193,882. Other additives are the thio and polythio sulfonamides of thiadiazoles such as those described in U. K. Patent Specification NO. 1,560,830.

Benzotriazoles derivatives also fall within this class of additives. When these compounds are included in the lubricating composition, they are preferably present in an amount not exceeding 0.2 wt % active ingredient.

A small amount of a demulsifying compound may be used. A preferred demulsifying components is described in EP 330,522. It is obtained by reacting an alkylene oxide with an adduct by reacting a bis-epoxide with a polyhydric alcohol.

The demulsifier should be used at a level not exceeding 0.1 mass % active ingredient.

A treat rate of 0.001 to 0.05 mass % active ingredient is convenient.

Pour point depressants, otherwise known as lube oil flow improvers, lower the minimum temperature at which the fluid will flow or can be poured. Such additives are well known. Typical of those additives which improve the low temperature fluidity of the fluid are Cs to Cls dialkyl fumarate/vinyl acetate copolymers and polyalkylmethacrylates.

Foam control can be provided by many compounds including an antifoamant of polysiloxane type, for example, silicone oil or polydimethyl siloxane.

Some of the above-mentioned additives can provide a multiplicity of effects; thus for example, a single additive may act as a dispersant-oxidation inhibitor. This approach is well known and does not require further elaboration.

The invention will be further illustrated by the following non-limiting examples.

Example 1 Into a vessel equipped with a condenser and accumulator having a refluxing capability is charged tridecyl alcohol and trimethylol propane in a molar ratio of 14.3 : 1. The vessel is heated and about 130°C adipic acid is charged to the vessel in a molar ratio to the trimethylol propane of 8: 1. The vessel is heated to a reaction temperature of about 210°C and the esterification reaction is run with removal of water overhead and refluxing of tridecyl alcohol. After about 90 % conversion of the carboxylic acid groups has occurred, tetraisopropyl titanate is added and the reaction continued until the acid number is below 0.5 (mg KOH/g sample). A small amount of water is then added to the vessel and mixed thoroughly with the contents to carry out hydrolysis of the titanate into titanium dioxide with minimal or essentially no change in

the acid number. The water is flashed off and the titanium dioxide is filtered out.

Finally, the unreacted tridecyl alcohol is removed by steam stripping. The resulting ester composition comprised of 80 wt % ditridecyladipate about 10 wt % of the complex alcohol ester of Formula IV, about 5 wt % of the dimer thereof, about 2 wt % of the various partial esters thereof, and about 3 wt % of trimer and higher homologues, is continuously soluble in mineral oil up to 15 wt %.

Example 2 A triol complex alcohol ester according to Formula I was made by esterifying the following reactants: 1 mole of trimethylolpropane, 1.375 moles adipic acid, 1.375 moles hydrogenated dimer of oleic acid, and 3.025 moles isodecyl alcohol. The resulting ester product was compared to the ester product produced by using 2.75 moles of adipic acid and no dimer acid, referred to hereinafter as"CALE."The results for viscosity, Total Acidity Number (TAN) and compatibility ratios in mineral oil (SN150) and PAO are set forth in Table 1.

Table 1 Compatibility Ratios Compound Viscosity (cSt) 40°C TAN SN150/CALE PAO/CALE CALE* 143.8 0.9 0.7/1 0.3/1 Substituted CALE** 855.9 6.4 >1 1.0/1 1.6/1 * Formed from 1 mole TMP, 2.75 moles AA, 3.027 moles IDA ** CALE in which 50% of adipic acid is substituted with Dimer Acid.

The data in this table demonstrate that by substituting a portion of the adipic acid with a hydrogenated dimer of oleic acid, a more than tenfold increase in the compatibility of substituted CALE with mineral oil (SN150) is achieved. A more than fivefold increase in the compatibility of poly alpha olefin with the substituted CALE is also demonstrated. The larger the compatibility ratios, the better the compatibility for engine oil formulations. The viscosity values shown in the table are consistent with the expectation that the molecular weight of the substituted CALE is significantly greater than the molecular weight of the unmodified CALE (Adipic acid, molecular weight 146 versus hydrogenated dimer of oleic acid, molecular weight 565). Surprisingly, the substitution of a relatively polar diacid with a less polar one has a significant positive effect on compatibility even though the substituted CALE has a higher molecular weight, and a much higher viscosity.

Example 3 The effect of incorporating different levels of the hydrogenated dimer of oleic acid in the CALE, as well as the effect of varying the diacid/trimethylolpropane ratio are summarized in Table 2.

Table 2 Compatibility Ratios Compound % Dimer Acid Diacid/TMP SN150/CALE PAO/CALE CALE 0 2.75 0.7/1 0.3/1 Substituted CALE #1 20 3.5 >11.3/1 1.3/1 Substituted CALE #2 39 4.5 >11.1/1 4.2/1 Substituted CALE #3 50 2.75 >11.0/1 1.6/1 The effect of increasing the ratio of a given diacid/TMP (trimethylolpropane) used in the synthesis is to produce a product having a lower molecular weight. The data shown in Table 2 in which the diacid/TMP ratio is 4.5, namely for substituted CALE #2, gave the best compatibility. This is consistent with the conclusion that lower molecular weight imparts improved compatibility.

Example 4 Various esters were made using different acid substitution rates and mono alcohol substitutions. The results are summarized in Table 3. <BR> <P> Table 3<BR> NBR Acid Mole Alcohol Mole Feed Feed OH* TAN KF Vis Vis Vl Pour MW MW Ratio Wt. 5-10%<BR> 19511 Substit-% Substit-% Mole Mole IR 1120 (cSt) (cSt) I'oint Wt. No. Wt. Ratio CALE in<BR> ution ution Ratio Ratio (ppm) 40 C 10UC deg F AVG AVG/No. C/O SN15<BR> Diacid ROH Compat-<BR> ibility<BR> 88 None 0 None 0 20 0.8 1675 157.8 20.64 153-36 1467 713 2.06 3.24 No<BR> 66* Phthalic 50 None 0 31 1. 1 452 327 24.43 95.8-27 1077 657 1.64 3.43 No<BR> 87 Phthalic 50 None 0 22 6.1 240 487.6 31.08 93.5-24 1062 669 1.59 3.43 No<BR> 85 Phthalic 50 None 0 50 1.5 248 209.6 17.09 85.4-30 737 569 1.3 3.43 No<BR> 72 Dimer Acid 50 None 0 16 6.3 375 855.9 73.11 162-30 2232 1100 2.03 6.05 Yes<BR> 76** Dimer Acid 39 None 0 8 2.9 264 139.8 18.53 149.3 <-44 1028 773 1.33 6.07 Yes<BR> 74** Dimer Acid 21 None 0 16 4.7 270 148.3 18.92 144.7 <-45 1099 751 1.46 4.77 Yes<BR> 89 Dimer Acid 21 None 0 3.5 4.7 13 3.7 360 188.5 23.01 148.9-42 1293 737 1.75 4.77 Yes<BR> 91 Dimer Acid 21 None 0 27 1.6 281 106.2 14.52 145.2 <-45 926 643 1.44 4.77 Yes<BR> 93 Dimer Acid 21 Exxal 13 100 23 2 257 170.7 19.46 130.7-42 956 676 1.54 5.41 Yes<BR> 97 Dimer Acid 10 Exxal 13 100 3.5 4. 7 14 2.9 239 172.6 19.68 131.4-36 1036 673 1.54 4.79 Yes<BR> 70 Dimer Acid 10 None 0 2. 75 3.0 26 7.2 367 366.4 37.12 148-33 1781 870 2.05 3.8 No<BR> 82 I) imerAcid 10 None 0 2 () 3.1 247 325.5 35.24 153.7-36 1765 892 1.98 3.8 No<BR> 99 Dimer Acid 5 Exxal 13 100 17 4.3 208 176.5 19.57 127.4 42 1042 661 1.58 4.51 Yes<BR> * 66 TME used in this run, product was not stripped to remove excess IDA<BR> ** 74 and 76 used CALE (1003-132), Dimer Acid, and isodecyl alcohol as feed

Accordingly, it has also been found that alcohol substitution, used in conjunction with the foregoing acid substitution, can achieve the desired results and raise the carbon-to- oxygen weight ratio to about 4.2 or higher. For example, in a feed of 2.75 moles adipic acid, 1 mole trimethylolpropane and 3.025 moles isodecyl alcohol, when a 100 mole percent substitution of a high carbon alcohol such as Exxal 0 13 (a tridecyl alcohol commercially available from Exxon Chemical Company) is made in the feed for the isodecyl alcohol, in conjunction with the acid substitution discussed above, the resulting complex alcohol ester is fully compatible with mineral oil. This is true at low acid substitution rates (e. g., 5 and 10 mole percent), as well as at higher acid substitution rates (e. g., 21 mole percent). In addition, changing the feed ratios using Exxal 13 can also achieve the desired compatibility results with poly alpha olefins.

Example 5 This example demonstrates the use of co-solvents in aiding solubility. Starting with the materials and parameters embodied in Table 1, above, the substituted CALE is diluted with diisodecyl adipate until the viscosity of the solution is comparable to the viscosity of the unsubstituted CALE. The resulting compatibility data is shown in Table 4.

Table 4 Compatibility Ratios Compound Viscosity (cSt) 40°C SN150/CALE PAO/CALE CALE* 143.8 0.7/1 0.3/1 Substituted CALE** 855.9 >11. 0/1 1.6/1 Diluted-140 Substituted CALE*** >11. 0/1 4.2/1 * Formed from 1 mole TMP, 2.75 moles AA, 3.027 moles IDA ** CALE in which 50% of adipic acid is substituted with Dimer Acid.

*** 60 Parts Substituted CALE, 40 parts diisodecyl adipate.

Thus, dilution of substituted CALE with diisodecyl adipate results in improved viscometrics and better compatibility with poly alpha olefin.

The invention having been thus described, it will be obvious that the same may be varied in many ways without departing from the scope and spirit of the invention as defined by the following claims.