The present invention relates generally to blends of natural oils and/or hydrocarbon-based lubricant basestocks and/or synthetic lubricant basestocks with high viscosity complex alcohol esters for use as a unique hydraulic fluid that exhibits the following properties: biodegradable, good lubricity, good thermal and oxidative stability, high viscosity and very little or low toxicity. In particular, it relates to enhanced lubricant basestocks formed by blending: (i) complex alcohol esters; and (ii) at least one other basestock selected from the group consisting of: synthetic oils (e.g., poly alpha olefins (PAO), polyalkylene glycols (PAG), phosphate esters, silicone oils, diesters and polyol esters), hydrocarbon-based oils (e.g., mineral oils and highly refined mineral oils) and natural oils (e.g., rapeseed, canola, and sunflower oils). These blended basestocks, when additized with different adpacks, can achieve the specified properties required of a hydraulic fluid

The interest in developing biodegradable lubricants for use in applications which result in the dispersion of such lubricants into waterways, such as rivers, oceans and lakes, has generated substantial interest by both the environmental community and lubricant manufacturers. The synthesis of a lubricant which maintains its cold-flow properties and additive solubility without loss of biodegradation or lubrication would be highly desirable..

The Organization for Economic Cooperation and Development (OECD) issued draft test guidelines for degradation and accumulation testing in December 1979. The Expert Group recommended that the following tests should be used to determine the "ready biodegradability" of organic chemicals: Modified OECD

Screening Test, Modified MITI Test (I), Closed Bottle Test, Modified Sturm Test and the Modified AFNOR Test. The Group also recommended that the following "pass levels" of biodegradation, obtained within 28 days, may be regarded as good

evidence of "ready biodegradability": (Dissolved Organic Carbon (DOC)) 70%; (Biological Oxygen Demand (BOD)) 60%; (Total Organic Carbon (TOD)) 60%; (CO ₂ ) 60%; and (DOC) 70%, respectively, for the tests listed above. Therefore, the "pass level" of biodegradation, obtained within 28 days, using the Modified Sturm Test is at least (CO ₂ ) 60%.

Since the main purpose in setting the test duration at 28 days was to allow sufficient time for adaptation of the micro-organisms to the chemical (lag phase), this should not allow compounds which degrade slowly, after a relatively short adaptation period, to pass the test. A check on the rate of biodegradation therefore should be made. The "pass level" of biodegradation (60%) must be reached within

10 days of the start of biodegradation. Biodegradation is considered to have begun when 10% of the theoretical CO ₂ has evolved. That is, a readily biodegradable fluid should have at least a 60% yield of CO ₂ within 28 days, and this level must be reached within 10 days of biodegradation exceeding 10%. This is known as the "10-Day Window."

The OECD guideline for testing the "ready biodegradability" of chemicals under the Modified Sturm test (OECD 30 IB, adopted May 12, 1981, and which is incorporated herein by reference) involves the measurement of the amount of CO ₂ produced by the test compound which is measured and expressed as a percent of the theoretical CO ₂ (ThCO ₂ ) it should have produced calculated from the carbon content of the test compound. Biodegradability is therefore expressed as a percentage of ThCO ₂ . The Modified Sturm test is run by spiking a chemically defined liquid medium, essentially free of other organic carbon sources, with the test material and inoculated with sewage micro-organisms. The CO ₂ released is trapped as BaCO ₃ . After reference to suitable blank controls, the total amount of

CO ₂ produced by the test compound is determined for the test period and calculated as the percentage of total CO ₂ that the test material could have theoretically produced based on carbon composition See G. van der Waal and D. Kenbeek, "Testing, Application, and Future Development of Environmentally

Friendly Ester Based Fluids", Journal of Synthetic Lubrication, Nol. 10, Issue No. 1, April 1993, pp. 67-83, which is incorporated herein by reference.

One basestock in current use today is rapeseed oil (i.e., a triglyceride of fatty acids, e.g., 7 % saturated Cι ₂ to Cι ₈ acids, 50% oleic acid, 36% linoleic acid and 7% linolenic acid, having the following properties: a viscosity at 40°C of 47.8 cSt, a pour point of 0°C, a flash point of 162°C and a biodegradability of 85% by the Modified Sturm test. Although it has very good biodegradability, its use in biodegradable lubricant applications is limited due to its poor low temperature properties and poor stability. Unless they are sufficiently low in molecular weight, esters synthesized from both linear acids and linear alcohols tend to have poor low temperature properties. Even when synthesized from linear acids and highly branched alcohols, such as polyol esters of linear acids, high viscosity esters with good low temperature properties can be difficult to achieve. In addition, pentaerythritol esters of linear acids exhibit poor solubility with dispersants such as polyamides, and trimethylolpropane esters of low molecular weight (i.e., having a carbon number less than 14) linear acids do not provide sufficient lubricity. This lower quality of lubricity is also seen with adipate esters of branched alcohols. Since low molecular weight linear esters also have low viscosities, some degree of branching is required to build viscosity while maintaining good cold flow properties. When both the alcohol and acid portions of the ester are highly branched, however, such as with the case of polyol esters of highly branched oxo acids, the resulting molecule tends to exhibit poor biodegradation as measured by the Modified Sturm test (OECD Test No. 30 IB). In an article by Randies and Wright, "Environmentally Considerate Ester

Lubricants for the Automotive and Engineering Industries", Journal of Synthetic Lubrication. Vol. 9-2, pp. 145-161, it was stated that the main features which slow or reduce microbial breakdown are the extent of branching, which reduces β- oxidation, and the degree to which ester hydrolysis is inhibited. The negative effect on biodegradability due to branching along the carbon chain is further discussed in

a book by R.D. Swisher, "Surfactant Biodegradation", Marcel Dekker. Inc.. Second Edition, 1987, pp. 415-417. In his book, Swisher stated that "The results clearly showed increased resistance to biodegradation with increased branching... Although the effect of a single methyl branch in an otherwise linear molecule is barely noticeable, increased resistance [to biodegradation] with increased branching is generally observed, and resistance becomes exceptionally great when quaternary branching occurs at all chain ends in the molecule." The negative effect of alkyl branching on biodegradability was also discussed in an article by N.S. Battersby, S E. Pack , and R.J. Watkinson, "A Correlation Between the Biodefzτadability of Oil Products in the CEC-L-33-T-82 and Modified Sturm Tests". Chemosphere,

24(12), pp. 1989-2000 (1992).

Initially, the poor biodegradation of branched polyol esters was believed to be a consequence of the branching and, to a lesser extent, to the insolubility of the molecule in water. However, recent work by the present inventors has shown that the non-biodegradability of these branched esters is more a function of steric hindrance than of the micro-organism's inability to breakdown the tertiary and quaternary carbons. Thus, by relieving the steric hindrance around the ester linkage(s), biodegradation can more readily occur with branched esters.

Branched synthetic polyol esters have been used extensively in non- biodegradable applications, such as refrigeration lubricant applications, and have proven to be quite effective if 3,5,5 -trimethylhexanoic acid is incorporated into the molecule at 25 molar percent or greater. However, trimethylhexanoic acid is not biodegradable as determined by the Modified Sturm test (OECD 301B), and the incorporation of 3, 5, 5 -trimethylhexanoic acid, even at 25 molar percent, would drastically lower the biodegradation of the polyol ester due to the quaternary carbons contained therein.

Likewise, incorporation of trialkyl acetic acids (i.e., neo acids) into a polyol ester produces very useful refrigeration lubricants. These acids do not, however, biodegrade as determined by the Modified Sturm test (OECD 301B) and cannot be used to produce polyol esters for biodegradable applications. Polyol esters of all

branched acids can be used as refrigeration oils as well. However, they do not rapidly biodegrade as determined by the Modified Sturm Test (OECD 301B) and, therefore, are not desirable for use in biodegradable applications.

Although polyol esters made from purely linear C ₅ and Cio acids for refrigeration applications would be biodegradable under the Modified Sturm test, they would not work as a lubricant in hydraulic fluid applications because the viscosities would be too low and wear additives would be needed. It is extremely difficult to develop a lubricant basestock which is capable of exhibiting all of the various properties required for biodegradable lubricant applications, i.e., good lubricity, low toxicity, high viscosity, low pour point, good oxidative and thermal stability and 60% biodegradability in 28 days as measured by the Modified Sturm test

The present inventors have discovered that blends of natural, hydrocarbon- based and/or synthetic lubricant basestocks with high viscosity complex alcohol esters unexpectedly provide a lubricating basestock having the following desirable properties biodegradability, high viscosity, good pour point, good thermal and oxidative stability, low toxicity, excellent lubricity, and seal compatibility

With the right ratios of polyol to polybasic acid to monohydric alcohol, complex alcohol esters can be produced which have: reduced cost (approximately half the cost of complex acid esters), high viscosity (greater than 100 cSt at 40°C), good thermal and oxidative stability, good biodegradability, low toxicity, good low temperature properties, and excellent lubricity When blended with lower viscosity oils, a wide range of iso grade products can be produced which meet stringent end- use specifications. The present inventors have discovered that when the amount of linear monohydric alcohol exceeds 20% of the total alcohol used, then the pour point is too high, e.g., above -30°C. Furthermore, the present inventors have discovered that the ratio of polybasic acid to polyol is critical in the formation of a complex alcohol ester. That is, if this ratio is too low then a complex alcohol ester contains undesirable amounts of heavies which reduces biodegradability and increases the hydroxyl number of the ester which increases the corrosive nature of

the resultant ester which is also undesirable. If, however, the ratio is too high then the resultant complex alcohol ester will have an undesirably low viscosity (reducing its applicability in certain iso grade applications) and poor seal swell characteristics. Other conventional natural, hydrocarbon-based and/or synthetic basestocks may each provide one or more of the desired attributes, e.g., high viscosity, good low temperature properties, biodegradability, lubricity, seal compatibility, low toxicity, and good thermal and oxidative stability, but none appears to be able to meet all of the product attributes by themselves. For example, some synthetic esters are capable of meeting the high viscosity property, but fail the biodegradability, low temperature requirements, or low toxicity requirements.

Similarly, the natural basestocks such as rapeseed oil are capable of meeting the biodegradability and toxicity properties, but fail to meet the required high viscosity, lubricity, and thermal and oxidative stability properties.

The present inventors have demonstrated that an unexpected, synergistic effect occurs when these complex alcohol esters of the present invention are blended with a natural, hydrocarbon-based and/or synthetic ester basestock, i.e., the blended basestock unexpectedly exhibits enhanced product attributes versus either the complex alcohol ester or other basestock by itself Thus, the blended basestocks according to the present invention exhibit the following attributes: excellent lubricity, seal compatibility, biodegradability, no or little toxicity, good low temperature properties, a wide viscosity range to meet various iso grade needs, and/or good thermal and oxidative stability.

The hydraulic fluids formed from the blended basestocks of the present invention are capable of being used in environmentally sensitive areas. They are typically boidegradable (>60%) and non-toxic. Most hydraulic fluids used today are comprised of mineral oils and additives. They are not biodegradable and in many cases, because of the additives, are considered toxic. Because of the unique properties of the blended basestocks of the present invention (i.e., very stable, biodegradable, non-toxic, wide iso grade range, excellent lubricating properties), the additives needed to meet the physical demands made on these hydraulic fluids

are minimal. In addition to requiring less additives, the requirements of the additives needed is less stringent. Therefore, less toxic additives can replace the more toxic additives and still meet the requirements. The blended basestocks of the present invention, for instance, have a high level of oxidative stability and anti- oxidants can be eliminated or significantly reduced. These blended basestocks of the present invention have good low temperature properties and additives such as pour point suppressors are not required. Moreover, these blended basestocks lubricate, therefore extreme pressure wear additives can be minimized. ZDDP, for example, is not required to meet lubricity requirements such as four-ball wear and FZG. The blended basestocks according to the present invention do not contain

ZDDP, whereas conventional rapeseed oil formulations do. Since ZDDP is toxic to most aquatic life it is undesirable in hydraulic fluid applications.

A hydraulic fluid which comprises: (1) a complex alcohol ester having the reaction product of: a polyhydroxyl compound represented by the general formula: R(OH) _n wherein R is any aliphatic or cyclo-aliphatic hydrocarbyl group and n is at least 2, provided that the hydrocarbyl group contains from about 2 to 20 carbon atoms; a polybasic acid or an anhydride of a polybasic acid; and a branched and/or linear monohydric alcohol, provided that the alcohol is added in an amount which is less than 20% excess; (2) at least one additional basestock selected from the group consisting of: natural oils, hydrocarbon-based oils and synthetic oils; and (3) an appropriate hydraulic fluid additive package, wherein the hydraulic fluid exhibits the following properties: excellent lubricity as determined by the FZG pump wear test (DIN 51354); good stability as evidenced by the results of such tests as RBOT (Rotary Bomb Oxidation Test (ASTM No. D-2272); good low temperature performance, complete iso grade viscosity range for most end-uses, unexpected environmental performance as evidenced by tests such as the Modified Sturm Biodegradation test, no VOC's and low toxicity. Because the basestock components make up 80 to 90+% of the total formulations, the present inventors have found that the above tests' results are either completely controlled or

significantly influenced by the right choices of basestock components In addition, the present inventors have found that with varying ratios of two primary components, namely, the polyol ester of technical grade pentaerythritol and 50 50 wt % ratio of iso-Cg, n-Cg and n-Cio acids and complex alcohol esters, most of the current specifications can be met without the aid of any additive and that the remaining specifications are so closely approached that only minimal additives are required to meet specifications

According to one preferred embodiment the biodegradable lubricating oil according to the present invention comprises an add mixture of the following components (A) 10-60 wt % of a complex alcohol ester basestock which comprises the reaction product of an add mixture of the following (1) a polyhydroxyl compound represented by the general formula

R(OH) _n wherein R is any aliphatic or cyclo-aliphatic hydrocarbyl group and n is at least 2, provided that said hydrocarbyl group contains from about 2 to 20 carbon atoms,

(2) a polybasic acid or an anhydride of a polybasic acid, provided that the ratio of equivalents of said polybasic acid to equivalents of alcohol from said polyhydroxyl compound is in the range between about 1 6 1 to 2 1 , and (3) a monohydric alcohol, provided that the ratio of equivalents of said monohydric alcohol to equivalents of said polybasic acid is in the range between about 0 84- 1 to 1 2 1 , wherein said complex alcohol ester exhibits a viscosity in the range between about 100-700 cSt at 40° C, preferably 100-200 cSt, and has a polybasic acid ester concentration of less than or equal to 70 wt %, based on said complex alcohol ester, and (B) 40-90 wt.% of at least one additional biodegradable basestock, wherein said biodegradable lubricating oil exhibits biodegradability of greater than

60% as measured by the Sturm test and a lubricity, as measured by the coefficient of friction, of less than or equal to 0 15 This biodegradable lubricating oil also passes the Yamaha Tightening Test, exhibits a FZG of greater than about 12, and/or exhibits a wear scar diameter of less than or equal to 0 45 millimeters

The unique complex alcohol ester according to the present invention exhibits the following properties: lubricity, as measured by the coefficient of friction, of less than or equal to 0.1; a pour point of less than or equal to -30°C, preferably -40°C; no volatile organic components; and thermal/oxidative stability as measured by HPDSC at 220°C and 3.445 MPa air of greater than 10 minutes with

0.5 wt.% of an antioxidant.

The complex alcohol ester also exhibits at least one of the properties selected from the group consisting of: (a) a total acid number of less than or equal to about 1.0 mgKOH/gram, (b) a hydroxyl number in the range between about 0 to 50 mgKOH/gram, (c) a metal catalyst content of less than about 25 ppm, (d) a molecular weight in the range between about 275 to 250,000 Daltons, (e) a seal swell equal to about diisotridecyladipate, (f) a viscosity at -25°C of less than or equal to about 100,000 cps, (g) a flash point of greater than about 200°C, (h) aquatic toxicity of greater than about 1,000 ppm, (I) a specific gravity of less than about 1.0, and (j) a viscosity index equal to or greater than about 150.

Preferably, the additional biodegradable basestock is at least one oil selected from the group consisting of: natural oil and biodegradable synthetic oils. The preferred biodegradable synthetic oil comprises 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 mixed acids comprising about 30 to 80 molar % of a linear acid having a carbon number in the range between about C ₅ to Cn, and about 20 to 70 molar % of at least one branched acid having a carbon number in the range between about C5 to C, . According to another embodiment of the present invention, these hydraulic fluids exhibit excellent lubricity and typically comprise an add mixture of the following components: (A) 2-30 wt.% of a complex alcohol ester basestock which comprises the reaction product of an add mixture of the following: (1) a polyhydroxyl compound represented by the general formula: R(OH) _n

wherein R is any aliphatic or cyclo-aliphatic hydrocarbyl group and n is at least 2, provided that said hydrocarbyl group contains from about 2 to 20 carbon atoms; (2) a polybasic acid or an anhydride of a polybasic acid, provided that the ratio of equivalents of said polybasic acid to equivalents of alcohol from said polyhydroxyl compound is in the range between about 1.6: 1 to 2: 1 ; and (3) a monohydric alcohol, provided that the ratio of equivalents of said monohydric alcohol to equivalents of said polybasic acid is in the range between about 0.84: 1 to 1.2: 1; wherein said complex alcohol ester exhibits a viscosity in the range between about 100-700 cSt at 40°C and has a polybasic acid ester concentration of less than or equal to 70 wt.%, based on said complex alcohol ester; and (B) 70-98 wt.% of at least one additional basestock, wherein said biodegradable lubricating oil exhibits biodegradability of greater than 60% as measured by the Sturm test; wherein said complex alcohol ester basestock is added in an amount such that said lubricating oil exhibits a lubricity, as measured by the coefficient of friction, of less than or equal to 0.15.

The complex alcohol ester is added primarily for biodegradability, good lubricity, low toxicity and high viscosity, and usually replaces or significantly reduces a metal extreme pressure (EP) wear additive such as one of the ZDDP family. In hydraulic fluid applications, the complex alcohol ester is added primarily for its high viscosity (greater than 100 cSt at 40°C) and biodegradability (greater than 60% after 28 days as measured by the Modified Sturm test). By using these two classes of components in varying concentrations, all desirable iso grades can be obtained, all of which are non-toxic and biodegradable. In addition, the over-all additive package can be formulated to minimize environmental impact due to the performance of the basestock blends. This unique blend of complex alcohol ester and biodegradable branched synthetic ester basestocks preferably exhibits at least one of the properties selected from the group consisting of: (a) excellent lubricity as evidenced by the elimination or reduction of toxic extreme pressure wear additives; (b) good stability as evidenced by tests such as RBOT test; (c) good low temperature properties as evidenced by pour points less than

-30°C and -25°C Brookfield viscosities of less than 8500 cps; (d) biodegradability of greater than 60% in 28 days as measured by the Modified Sturm test; (e) low toxicity (greater than 1,000 ppm); (f) good seal compatibility; (g) high flash point (greater than 200°C) to reduce volatile organic components (NOC's), and (h) low toxicity.

When the lubricating oil is comprised of a complex alcohol ester with a viscosity greater than 100 cSt at 40°C and either a hydrocarbon-based oil or synthetic oil, then the basestock blend preferably exhibits sufficient lubricity to eliminate or significantly reduce the need for toxic extreme pressure wear additives such as ZDDP and other metal containing materials. In this instance the complex alcohol ester is preferably added in an amount between about 2 to 30 wt.% and the hydrocarbon-based oil and/or synthetic oils are added in an amount between 70 to 98 wt.%.

When the lubricating basestock oil is comprised of a complex alcohol ester with a viscosity greater than 100 cSt at 40°C and a biodegradable natural, hydrocarbon-based and/or synthetic ester, then the basestock blend preferably exhibits at least one of the properties selected from the group consisting of: (a) excellent lubricity as evidenced by the elimination or reduction of toxic extreme pressure wear additives; (b) good stability as evidenced by tests such as RBOT test; (c) good low temperature properties as evidenced by pour points less than -

30°C and -25°C Brookfield viscosities of less than 8500 cps; and (d) biodegradability of greater than 60% as measured by the Modified Sturm test. In this instance, it is desirable that the complex alcohol ester be added in an amount between about 10-60 wt.% and the other biodegradable basestock ester be added in an amount between about 40-90 wt.%

The additive package preferably comprises at least one additive selected from the group consisting of: viscosity index improvers, corrosion inhibitors, boundary lubrication agents, demulsifiers, pour point depressants, and antifoaming agents.

High viscosity complex alcohol esters provide a unique level of biodegradability in conjunction with effective lubricating properties even at low concentrations (i.e., less than 5 wt.%), especially designed for hydraulic fluid applications. If the total acid number (TAN) and the di-ester content are low (i.e., less than 0.7 mgKOH/gram and less than 45 wt.%, respectively), and the esterification catalyst is effectively removed to a level of less than 25 ppm, high viscosity complex alcohol esters also provided excellent stability, good seal compatibility, and low toxicity. The present inventors have discovered that these unique high viscosity, low metals/low acid complex alcohol esters, when blended with other natural, hydrocarbon-based and/or synthetic basestocks, result in lubricant basestocks which exhibit biodegradability, excellent lubricity, high viscosity and low toxicity depending upon which additional basestock the complex alcohol ester is blended with and concentration of the complex alcohol ester in the blend. The preferred lubricant according to the present invention is a blend of the described complex alcohol ester composition and at least one additional basestock selected from the group consisting of: natural oils (e.g., rapeseed oil, canola oil and sunflower oil) and/or hydrocarbon-based oils (e.g., mineral oils and highly refined mineral oils and/or synthetic oils (e.g., poly alpha olefins (PAO), polyalkylene glycols (PAG), polyisobutylene (PIB), phosphate esters, silicone oils, diesters, and polyol esters); and a lubricant additive package. Blended hydraulic fluids according to the present invention preferably include 2 to 30 wt.% complex alcohol ester and 70 to 98 wt.% of a second basestock selected from natural oils, hydrocarbon-based oils, and/or synthetic oils. When the complex alcohol ester according to the present invention is blend with a biodegradable synthetic or natural ester basestock, it is preferably added in an amount between about 10 to 60 wt.% and the biodegradable branched synthetic ester basestock is added in an amount between about 40 to 90 wt.%.

COMPLEX ALCOHOL ESTERS

One preferred complex alcohol ester according to the present invention the reaction product of an add mixture of the following: a polyhydroxyl compound represented by the general formula: R(OH) _n wherein R is any aliphatic or cyclo-aliphatic hydrocarbyl group and n is at least 2, provided that the hydrocarbyl group contains from about 2 to 20 carbon atoms; a polybasic acid or an anhydride of a polybasic acid, provided that the ratio of equivalents of the polybasic acid to equivalents of alcohol from the polyhydroxyl compound is in the range between about 1.6: 1 to 2: 1 ; and a monohydric alcohol, provided that the ratio of equivalents of the monohydric alcohol to equivalents of the polybasic acid is in the range between about 0.84: 1 to 1.2: 1 ; wherein the complex alcohol ester exhibits a pour point of less than or equal to -30°C, a viscosity in the range between about 100-700 cSt at 40°C, preferably 100-200 cSt, and having a polybasic acid ester concentration of less than or equal to 70 wt.%, based on the complex alcohol ester.

The present inventors have unexpectedly discovered that if the ratio of polybasic acid to polyol (i.e., polyhydroxyl compound) is too low, then an unacceptable amount of cross-linking occurs which results in very high viscosities, poor low temperature properties, poor biodegradability, and poor compatibility with other basestocks and with additives. If, however, the ratio of polybasic acid to polyol is too high, then an unacceptable amount of polybasic acid ester (e.g., adipate di-ester) is formed resulting in poor seal compatibility and low viscosity which limits the complex alcohol ester's applicability. The present inventors have also discovered that if the ratio of monohydric alcohol to polybasic acid is too low, i.e., less than 0.96 to 1 , then an unacceptably high acid number, sludge concentration, deposits, and corrosion occur. If, however, the ratio of monohydric alcohol to polybasic acid is too high (i.e., 1.2 to 1), then an unacceptable amount of polybasic acid ester is formed resulting in poor

seal compatibility and low viscosity which limits the complex alcohol ester's applicability

Moreover, the complex alcohol ester according to the present invention exhibits the following properties lubricity, as measured by the coefficient of friction, of less than or equal to 0 1 , a pour point of less than or equal to -30°C, preferably -40°C, biodegradability of greater than 60%, as measured by the Sturm test (e g , Modified Sturm test), an aquatic toxicity of greater than 1,000 ppm, no volatile organic components, and thermal/oxidative stability as measured by HPDSC at 220°C and 3 445 MPa air of greater than 10 minutes with 0 5 wt % of an antioxidant

When the polyhydroxyl compound is at least one compound selected from the group consisting of technical grade pentaerythπtol and mono-pentaerythπtol, then the ratio of equivalents of the polybasic acid to equivalents of alcohol from the polyhydroxyl compound is in the range between about 1 75 1 to 2 1 When the polyhydroxyl compound is at least one compound selected from the group consisting of tπmethylolpropane, trimethylolethane and tπmethylolbutane, then the ratio of equivalents of the polybasic acid to equivalents of alcohol from the polyhydroxyl compound is in the range between about 1 6 1 to 2 1 When the polyhydroxyl compound is di-pentaerythπtol, then the ratio of equivalents of the polybasic acid to equivalents of alcohol from the polyhydroxyl compound is in the range between about 1 83 1 to 2 1

The monohydric alcohol may be at least one alcohol selected from the group consisting of branched and linear C5 to Cn alcohol The linear monohydric alcohol is preferably present in an amount between about 0 to 30 mole%, more preferably between about 5 to 20 mole%

In a preferred embodiment, the monohydnc alcohol is at least one alcohol selected from the group consisting of C ₈ to C10 iso-oxo alcohols Accordingly, one highly preferred complex alcohol ester is formed from the reaction product of

the admixture of trimethylolpropane, adipic acid and either isodecyl alcohol or 2- ethylhexanol.

The unique complex alcohol esters according to the present invention preferably exhibit at least one of the properties selected from the group consisting of: (a) a total acid number of less than or equal to about 1.0 mgKOH/gram, (b) a hydroxyl number in the range between about 0 to 50 mgKOH/gram, (c) a metal catalyst content of less than about 25 ppm, (d) a molecular weight in the range between about 275 to 250,000 Daltons, (e) a seal swell equal to about diisotridecyladipate, (f) a viscosity at -25°C of less than or equal to about 100,000 cps, (g) a flash point of greater than about 200°C, (h) aquatic toxicity of greater than about 1,000 ppm, (i) a specific gravity of less than about 1.0, and (j) viscosity index equal to or greater than about 150.

It is particularly desirable to be able to control the stoichiometry in such a way so as to be able to manufacture the same product each time. Further, one wants to obtain acceptable reaction rates and to obtain high conversion with low final acidity and low final metals content. The present inventors have synthesized a composition and a method of production of that composition which provides a high viscosity oil having good low temperature properties, low metals, low acidity, high viscosity index, and acceptable rates of biodegradability as measured by the Modified Sturm test

Of particular interest is the use of certain oxo-alcohols as finishing alcohols in the process of production of the desired materials. Oxo alcohols are manufactured via a process, whereby propylene and other olefins are oligomerized over a catalyst (e.g., a phosphoric acid on Kieselguhr clay) and then distilled to achieve various unsaturated (olefinic) streams largely comprising a single carbon number. These streams are then reacted under hydroformylation conditions using a cobalt carbonyl catalyst with synthesis gas (carbon monoxide and hydrogen) so as to produce a multi-isomer mix of aldehydes/alcohols. The mix of aldehydes/alcohols is then introduced to a hydrogenation reactor and hydrogenated

to a mixture of branched alcohols comprising mostly alcohols of one carbon greater than the number of carbons in the feed olefin stream.

One particularly preferred oxo-alcohol is isodecyl alcohol, prepared from the corresponding C ₉ olefin. When the alcohol is isodecyl alcohol, the polyol is trimethylolpropane and the acid is the C ₆ diacid, e.g. adipic acid, a preferred complex alcohol ester is attained. The present inventors have surprisingly discovered that this complex alcohol ester, wherein the alcohol is a branched oxo- alcohol has a surprisingly high viscosity index of ca. 150 and is surprisingly biodegradable as defined by the Modified Sturm test. This complex alcohol ester can be prepared with a final acidity (TAN) of less than 0.7 mg KOH/gram and with a conversion of the adipic acid of greater than 99%. In order to achieve such a high conversion of adipic acid, a catalyst is required, and further, it is preferable to add the catalyst within a relatively narrow conversion window. Alternatively, the present inventors have discovered that the catalyst can also be added at anytime during the reaction product and removed to an amount of less than 25 ppm and still obtain a final acidity (TAN) of less than 0.7 mg KOH/gram, so long as the esterification reaction is followed by a hydrolysis step wherein water is added 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 about 100 to 200°C, more preferably between about 125 to 175°C, and most preferably between about 140 to 160°C, and pressures greater than one atmosphere. Such high temperature hydrolysis can successfully remove the catalyst metals to less than 25 ppm without increasing the TAN to greater than 0.7 mgKOH/gram. The low metals and low acid levels achieved by use of this novel high temperature hydrolysis step is completely unexpected.

The present inventors have discovered that the actual product is a broad mix of molecular weights of esters and that, if so desired, an amount of diisodecyl adipate can be removed from the higher molecular weight ester via wipefilm evaporation or other separation techniques if desired.

The present inventors have also discovered that highly stable complex alcohol esters can be produced that are resistant to viscosity increases during heating. This is accomplished by synthesizing complex alcohol esters with a low hydroxyl number by limiting the ratio of polybasic acid, polyol and monohydric alcohol. These highly stable complex alcohol esters exhibit no increase in viscosity when heated to temperatures above 200°C, while similar esters with high hydroxyl numbers increase in viscosity from 5 to 10% under similar conditions.

MONOHYDRIC ALCOHOLS Among the alcohols which can be reacted with the diacid and polyol are, by way of example, any C$ to Cι ₃ branched and/or linear monohydric alcohol selected from the group consisting of: isopentyl alcohol, n-pentyl alcohol, isohexyl alcohol, n-hexyl alcohol, isoheptyl alcohol, n-heptyl alcohol, iso-octyl alcohol (e.g., 2-ethyl hexanol or iso-octyl alcohol), n-octyl alcohol, iso-nonyl alcohol, n-nonyl alcohol, isodecyl alcohol, and n-decyl alcohol; provided that the amount of linear monohydric alcohol is present in the range between about 0-20 mole %, based on the total amount of monohydric alcohol.

One preferred class of monohydric alcohol is oxo alcohol. Oxo alcohols are manufactured via a process, whereby propyiene and other olefin s are oligomerized over a catalyst (e.g., a phosphoric acid on Kieselguhr clay) and then distilled to achieve various unsaturated (olefinic) streams largely comprising a single carbon number. These streams are then reacted under hydroformylation conditions using a cobalt carbonyl catalyst with synthesis gas (carbon monoxide and hydrogen) so as to produce a multi-isomer mix of aldehydes/alcohols. The mix of aldehydes/alcohols is then introduced to a hydrogenation reactor and hydrogenated to a mixture of branched alcohols comprising mostly alcohols of one carbon greater than the number of carbons in the feed olefin stream.

The branched oxo alcohols are preferably monohydric oxo alcohols which have a carbon number in the range between about C5 to Cι ₃ . The most preferred monohydric oxo alcohols according to the present invention include iso-octyl

alcohol, e.g., Exxal™ 8 alcohol, formed from the cobalt oxo process and 2- ethylhexanol which is formed from the rhodium oxo process.

The term "iso" is meant to convey a multiple isomer product made by the oxo process. It is desirable to have a branched oxo alcohol comprising multiple isomers, preferably more than 3 isomers, most preferably more than 5 isomers.

Branched oxo alcohols may be produced in the so-called "oxo" process by hydroformylation of commercial branched C ₄ to Cι ₂ olefin fractions to a corresponding branched C5 to Cι ₃ alcohol/aldehyde-containing oxonation product. In the process for forming oxo alcohols it is desirable to form an alcohol/aldehyde intermediate from the oxonation product followed by conversion of the crude oxo alcohol/aldehyde product to an all oxo alcohol product.

The production of branched oxo alcohols from the cobalt catalyzed hydroformylation of an olefinic feedstream preferably comprises the following steps: (a) hydroformylating an olefinic feedstream by reaction with carbon monoxide and hydrogen (i.e., synthesis gas) in the presence of a hydroformylation catalyst under reaction conditions that promote the formation of an alcohol/aldehyde-rich crude reaction product;

(b) demetalling the alcohol/aldehyde-rich crude reaction product to recover therefrom the hydroformylation catalyst and a substantially catalyst-free, alcohol/aldehyde-rich crude reaction product; and

(c) hydrogenating the alcohol/aldehyde-rich crude reaction product in the presence of a hydrogenation catalyst (e.g., massive nickel catalyst) to produce an alcohol-rich reaction product. The olefinic feedstream is preferably any C ₄ to Cι ₂ olefin, more preferably branched C to C9 olefins. Moreover, the olefinic feedstream is preferably a branched olefin, although a linear olefin which is capable of producing all branched oxo alcohols is also contemplated herein. The hydroformylation and subsequent hydrogenation in the presence of an alcohol-forming catalyst, is capable of producing branched C5 to Cι ₃ alcohols, more preferably branched C« alcohol (i.e.,

Exxal™ 8), branched C ₉ alcohol (i.e., Exxal™ 9), and isodecyl alcohol. Each of the branched oxo C5 to Cι ₃ alcohols formed by the oxo process typically comprises, for example, a mixture of branched oxo alcohol isomers, e.g., Exxal™ 8 alcohol comprises a mixture of 3,5-dimethyl hexanol, 4,5-dimethyl hexanol, 3,4-dimethyl hexanol, 5 -methyl heptanol, 4-methyl heptanol and a mixture of other methyl heptanols and dimethyl hexanols.

Any type of catalyst known to one of ordinary skill in the art which is capable of converting oxo aldehydes to oxo alcohols is contemplated by the present invention. It is preferable that the linear monohydric alcohol be present in an amount between about 0 to 30 mole%, preferably between about 5 to 20 mole%.

POLYOLS Among the polyols (i.e., polyhydroxyl compounds) which can be reacted with the diacid and monohydric alcohol are those represented by the general formula:

R(OH) _n wherein R is any aliphatic or cyclo-aliphatic hydrocarbyl group (preferably an alkyl) and n is at least 2. The hydrocarbyl group may contain from about 2 to about 20 or more carbon atoms, and the hydrocarbyl group may also contain substituents such as chlorine, nitrogen and/or oxygen atoms. The polyhydroxyl compounds generally may contain one or more oxya'lkylene groups and, thus, the polyhydroxyl compounds include compounds such as polyetherpolyols. The number of carbon atoms (i.e., carbon number, wherein the term carbon number as used throughout this application refers to the total number of carbon atoms in either the acid or alcohol as the case may be) and number of hydroxy groups (i.e., hydroxyl number) contained in the polyhydroxyl compound used to form the carboxylic esters may vary over a wide range.

The following alcohols are particularly useful as polyols: neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, mono-pentaerythritol, technical grade pentaerythritol, and di-pentaerythritol. The most preferred alcohols

are technical grade (e.g., approximately 88% mono-, 10% di- and 1-2% tri- pentaerythritol) pentaerythritol, monopentaerythritol, di-pentaerythritol, and trimethylolpropane.

POLYBASIC ACIDS Selected polybasic or polycarboxylic acids include any C ₂ to Cι ₂ diacids, e.g., adipic, azelaic, sebacic and dodecanedioic acids.

ANHYDRIDES Anhydrides of polybasic acids can be used in place of the polybasic acids, when esters are being formed. These include succinic anhydride, glutaric anhydride^ adipic anhydride, maleic anhydride, phthalic anhydride, nadic anhydride, methyl nadic anhydride, hexahydrophthalic anhydride, and mixed anhydrides of polybasic acids.

The lubricating oils contemplated for use with the complex alcohol ester compositions of the present invention include natural oils, synthetic oils and hydrocarbon-based oils of lubricating viscosity and mixtures thereof. The synthetic oils include long chain alkanes such as cetanes and olefin polymers such as oligomers of hexene, octene, decene, and dodecene, etc The other synthetic oils include (1) fully esterified ester oils, with no free hydroxyls, such as pentaerythritol esters of monocarboxylic acids having 2 to 20 carbon atoms, trimethylol propane esters of monocarboxylic acids having 2 to 20 carbon atoms, (2) polyacetals and

(3) siloxane fluids. Especially useful among the synthetic esters are those made from polycarboxylic acids and monohydric alcohols.

HYDRAULIC FLUIDS The basestock blend can be used in the formulation of hydraulic fluids together with selected lubricant additives. The preferred hydraulic fluids are typically formulated using the basestock blend formed according to the present invention together with any conventional hydraulic fluid additive package. The additives listed below are typically used in such amounts so as to provide their normal attendant functions. The additive package may include, but is not limited

to, viscosity index improvers, corrosion inhibitors, boundary lubrication agents, demulsifiers, pour point depressants, and antifoaming agents.

The hydraulic fluid according to the present invention can employ typically about 90 to 99% basestock blend, with the remainder comprising an additive package.

Other additives are disclosed in US-4783274 (Jokinen et al.), which issued on November 8, 1988, and which is incorporated herein by reference.

Examples of the above additives for use in lubricants are set forth in the following documents which are incorporated herein by reference: US-A-4663063 (Davis), which issued on May 5, 1987; US-A-5330667 (Tiffany, III et al.), which issued on July 19, 1994; US-A-4740321 (Davis et al.), which issued on April 26, 1988; US-A-5321 172 (Alexander et al.), which issued on June 14, 1994; and US-A-5049291 (Miyaji et al.), which issued on September 17, 1991.

One preferred additional basestock is a biodegradable synthetic ester basestock which comprises 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 mixed acids comprising about 30 to 80 molar %, preferably 35 to 55 molar %, of a linear acid having a carbon number in the range between about C ₅ to d ₂ , preferably between about C ₇ to Cio, and about 20 to 70 molar %, preferably 35 to 55 molar %, of at least one branched acid having a carbon number in the range between about C ₅ to C _[3 ; wherein the ester basestock exhibits the following properties; at least 60% biodegradation in 28 days as measured by the Modified Sturm test; a pour point of less than -25°C; a viscosity of less than 7500 cps at -25°C; and oxidative stability of up to 10 minutes as measured by HPDSC with 0.5 wt.% of an antioxidant such as Nanelube™ 81.

The biodegradable synthetic ester basestock preferably comprises multiple isomers, i.e., at least 3 isomer or more, preferably greater than 3 to 5 isomers. The branched acid is predominantly a doubly branched or an alpha branched acid having an average branching per molecule in the range between about 0.3 to 1.9.

Moreover, the branched acid is at least one acid selected from the group consisting of 2-ethylhexanoic acids, isoheptanoic acids, isooctanoic acids, isononanoic acids, and isodecanoic acids.

A preferred dispersant for hydraulic fluid formulations comprises a major amount of at least one oil of lubricating viscosity and a minor amount of a functionalized and derivatized hydrocarbon; wherein functionalization comprises at least one group of the formula -CO-Y-R ³ wherein Y is O or S, R ³ is aryl, substituted hydrocarbyl, and -Y-R ³ has a pKa of 12 or less, wherein at least 50 mole % of the functional groups are attached to a tertiary carbon atom; and wherein said functionalized hydrocarbon is derivatized by a nucleophilic reactaπt.

The nucleophilic reactant is selected from the group consisting of alcohols and amines.

EXAMPLE 1 Complex alcohol esters were made using both trimethylolpropane and technical grade pentaerythritol as the polyol, adipic acid as the polybasic acid and various C -Cι ₃ monohydric alcohols, both linear and branched During the reaction, the adipate di-ester was also formed Some of these materials were wipefilmed to remove the adipate di-ester and some were not The products were submitted for various tests One particularly surprising result was in regard to seal swell

Diisodecyladipate (DIDA) has been found to be particularly harsh on some seals. Samples containing as much as 40% DIDA demonstrated the same seal swell as samples of diisotridecyladipate (DTD A), which is used as a commercial lubricant today because of its low seal swell. EXAMPLE 2

Table 1 below compares a variety of complex alcohol esters versus a conventional branched ester to demonstrate the increased biodegradability and thermal and oxidative stability of the complex alcohol esters according to the present invention.

Table 1

Pour Viscosity at HPDSC

Point -25°C 40°C 100°C Viscosity Qry*** Biodegradability

Ester (° (cps) (cSt) (cSt) Index (mm ) (%)

TMP/AA/IDA - - 165 7 21 31 152 - 67 23

TMP/AA/n-C7* -33 43500 155 6 18.22 131 - 80 88

TPE/AA/IHA - - 160 8 24.35 184 58 83 84 83

TMP/ιso-Cι ₈ -20 358000 78.34 11 94 147 4 29 63.32

TMP/AA/n-C7**-14 solid 27.07 5 77 163 - 78 84 ** Complex alcohol ester made without stπpping of the adipate

** This is a partial ester of TMP, adipic acid and a n-C7 acid wherein the adipate diester has been stπpped out

*** OIT denotes oxidation induction time (minutes until decomposition)

HPDSC denotes high pressure differential caloπmetry TMP is tπmethylolpropane

AA is adipic acid

IDA is isodecyl alcohol

IHA IS isohexyl alcohol

TPE is technical grade pentaerythritol ιso-Ci8 is lsostearate

The branched acid ester and the complex alcohol ester formed without stπpping exhibited undesirable pour points, i e , -20 and -14°C, respectively, and undesirable viscosities at -25°C, i e , 358,000 cps and a solid product, respectively

EXAMPLE 3 The samples set forth below in Table 2 demonstrate that complex alcohol esters can exhibit good biodegradability, especially complex alcohol esters blended with other basestocks

Table 2

Ester/ Viscosity Percent Biodegradable Ester Blend @40°C (Modified Sturm)

TMP/AA/IDA 56 89 65 21

TMP/AA/IDA TMP/1770 25.26 77 40

TMP/AA/LDA TMP/ 1770 + DI 43 36 68 90

TMP/AA/n-C7 alcohol 27.07 78.84

TMP/AA/n-C7 alcohol (bottoms) 155.60 80.88

TMP/AA TNA 115.00 60.26

TMP/AA/TNA 137.30 57.81

1770 denotes a 70:30 mixture of n-C and α-branched C ₇ , respectively . DI denotes dispersant additive package. INA denotes isononylalcohol.

EXAMPLE 4 Set forth below in Tables 3 and 4 are various blends of hydraulic fluids and their respective percent biodegradation, the iso grade, hydrolytic stability as measured by RBOT (Rotary Bomb Oxidation test, ASTM D2272), FZG (i.e., pump wear test, DIN 51354), and wear scar diameter (4-Ball War Scar Diameter, (40 kg, 75°C, 1200 rpm, 60 minutes) mm.

Table 3

Wt.% Meets Viscosity

Blended Sample Ratio % Biodegradation for Iso Grade

TPE/C810/Ck8:DIDA 85: 15 78 32 cSt TMPE/C810/Ck8 :TMP/A A/ID A 88:12 69 46 cSl TPE/C810/Ck8:TMP/AA/IDA 60:40 65 68 cSt TPE/C810/Ck8:TMP/ A A/ID A 30:70 63 100 cSt Rapeseed Oil 85 32 cSt

C810 is a mixture of linear C ₈ and C] ₀ acids.

Ck8 is an iso-octyl alcohol form from the cobalt oxo process.

AA is adipic acid

IDA is isodecyl alcohol

DIDA is diisodecyl adipate

TPE is technical grade pentaerythritol

TMP is trimethylo.propane

Table 4

Wt.% Meets Viscosity RBOT Wear Scar

Blended Sample* Ratio for Iso Grade (Min) FZG Diameter (mm)

TPE/C810/Ck8:DIDA 85: 15 32 cSt 1300 >13 0.35

TMPE/C810/Ck8:TMP/AA IDA 88:12 46 cSt 750 >12 0.30

TPE/C810/Ck8:TMP/AA/TDA 60:40 68 cSt TPE/C810/Ck8:TMP/AA/IDA 30:70 100 cSt

Rapeseed Oil - 32 cSt 118 - 0.40

* Samples contain 0.9 to 5.0 wt.% Adpack. C810 is a mixture of linear Cg and Ci ₀ acids.

Ck8 is an iso-octyl alcohol form from the cobalt oxo process. AA is adipic acid IDA is isodecyl alcohol DIDA is diisodecyl adipate TPE is technical grade pentaerythritol

TMP is trimethylolpropane