ES2659370T3 - Lubricating base oil with low pour point - Google Patents

Abstract

Use of a lubricating base oil, comprising at least one ester obtained by esterifying 2-propylheptanoic acid with at least 2,2-substituted 1,3-propanediol and / or at least one dimer, trimer or polymer thereof and / or at least one alkoxylated species of said 2,2-substituted 1,3-propanediol or said dimer, trimer or polymer thereof, in the production of a lubricant for internal combustion engines and turbine engines.

Description

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DESCRIPTION

Lubricating base oil with low pour point

The present invention relates to a lubricating base oil for turbine or automobile, aviation, ship or stationary engine comprising at least one ester between 2-propylheptanoic acid and at least one 1,3-propanediol 2,2- substituted and / or at least one dimer, trimer or polymer thereof and / or at least one alkoxylated species of a said 2,2-substituted 1,3-propanediol or said dimer, trimer or polymer thereof, and to the use of said lubricating base oil for internal combustion engines and turbine engines.

To be suitable for a specific application, a lubricant, which comprises a lubricating base oil formulated with appropriate performance additives, must exhaustively meet the requirements of a specific application and it is usually not enough to just meet a specific parameter, such as viscosity, but compliance with the entire set of application properties is required, which often includes specific requirements for parameters such as viscosity, viscosity stability, flash point, pour point, volatility etc.

Lubricating base oils are classified according to the API (American Petroleum Institute, Publication API 1509) into five categories according to their chemical composition: groups I to Ill consisting of different grades of mineral oil base oils, group IV being defined for poly (a-olefins) and the group V being reserved for all other base oils, which include ester base oils. It is known in the art that base oils of different groups contribute to certain typical lubricant yields, such as low temperature properties, oxidation stability and / or compatibility properties. It is also known in the art, when a final lubricant product is formulated for a specific application, that two or more base oils of one or more groups can be combined. It is known that synthetic esters are combined with base oils of other groups, such as poly (a-olefin) of API group IV, as disclosed in US 5,151,205 or with mineral oils, API groups 1 to 3 as disclosed in US 5,665,683.

Normally, a lubricant is formulated by combining a lubricating base oil, or a mixture of lubricating base oils, of suitable inherent properties, with additives and other optional formulation aids. The esters of diols, triols, tetroles and polyols are lubricating base oils frequently used in a series of high performance lubricant applications. Said esters are obtained from an alcohol having two or more hydroxyl groups, alcohol which is esterified with a carboxylic acid or mixture of acids. During the esterification process, the hydroxyl groups of said alcohol are partially or totally converted into ester groups, by means of having an acid component attached thereto.

The formulation of a lubricant that satisfies the specific final properties normally involves the step of selecting a base oil that inherently shows properties that are close to those required. It is known in the art that the final precise adjustment of the desired properties can be made by mixing the base oil with other components capable of modifying the properties according to the specifications and other requirements. However, mixing is not always preferred, since it introduces a complexity in the system, at least in the form of an increase in the number of components included in the lubricant.

It is also known in the art that certain properties of the ester can be strongly influenced by the selection of mixtures of starting materials instead of individual reactants. For example, the ester product may be composed of a mixture of said alcohols esterified with a carboxylic acid or said alcohol may be esterified with a mixture of carboxylic acids in order to obtain, for example, improved compatibility and cold flow properties. . In even more general terms, this can be applied when a mixture of said alcohols is combined with a mixture of carboxylic acids in order to obtain a statistical mixture of ester final products. However, esters based on such mixtures of raw materials are not desired in all cases. They induce a degree of uncertainty in the system with respect to the composition and one or more of the statistically formed ester compounds may contribute to an undesired and / or adverse performance. Therefore, there are needs and requirements of a range of different reactant esters, essentially individual, that show inherent advantageous properties.

The pour point is a property of lubricants, which characterizes the cold flow properties of a lubricant. The pour point is reported as the reading of the lowest temperature at which a test lubricant shows a defined degree of fluidity. A more detailed description is provided in ASTM D5950. A low point of fluidity is desirable in lubricants that are intended for use in low temperature conditions, which occur, for example, when starting engines in cold and / or winter weather conditions. Examples of applications that require good cold properties include, but are not limited to, automotive and aviation lubricants, automotive, stationary and two-stroke engine lubricants, hydraulic fluids, cooling lubricants, grease and dielectric fluids.

It is known that esters of branched carboxylic acids contribute to reducing the pour point, as disclosed for example in US 4,514,314. However, so far branched carboxylic acids

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used and notified are branched either neo or iso. 2-Ethylhexanoic acid is the only 2-branched carboxylic acid used that has more than four carbons and the carboxylic acids disclosed in the literature that have 10 or more carbon atoms are either linear acids, either iso acids or neo acids .

Now, it has been found quite surprisingly that the introduction of 2-propylheptanoic acid as the acid component in an ester, which is intended to be a lubricating base oil, significantly reduces the melting point of the ester. The combination obtained, according to the present invention, of high flash point, low evaporation loss, high viscosity and the unexpected and exceptionally low pour point and the high value of the viscosity index imply new technological opportunities in the adjustment of the properties of the lubricants currently known. No 2-branched carboxylic acids, other than 2-ethylhexanoic acid well known in the art, have been reported to date as starting material, nor any correlation between the molecular weight of the ester and the pour point of the lubricant, for lubricants of ester and / or lubricating base oils.

Accordingly, the present invention relates to a turbine or automotive, aviation, ship or stationary lubricating base oil comprising at least one ester obtained by esterification of 2-propylheptanoic acid with (i) at least a 2,2-substituted 1,3-propanediol and / or at least one dimer, trimer or polymer thereof, wherein said 2,2-substituted 1,3-propanediol is neopentyl glycol, 2-butyl-2-ethyl- 1,3-propanediol, trimethylolethane or trimethylolbutane, and / or (ii) at least one alkoxylated species of a 2,2-substituted 1,3-propanediol or said dimer, trimer or polymer thereof.

Further, the present invention relates to the use of a lubricating base oil comprising at least one ester between 2-propylheptanoic acid and at least one 2,2-substituted 1,3-propanediol and / or at least one dimer, trimer or polymer thereof and / or at least one alkoxylated species of a said 2,2-substituted 1,3-propanediol or a said dimer, trimer or polymer thereof in the production of a lubricant for internal combustion engines and turbine engines such as car engines, aviation engines, boat engines and stationary engines. Such engines can be adequately exemplified, for example, by Otto, diesel, Wanckel and jet engines, including two-stroke engines. The most preferred lubricating base oil herein comprises a trimethylolpropane triester or a pentaerythritol and / or di-trimethylolpropane tetraester.

In preferred embodiments of the present invention, said 2,2-substituted 1,3-propanediol is a 2,2-dialkyl-1,3-propanediol, a 2-alkyl-2-hydroxyalkyl-1,3-propanediol or a 2 , 2-dihydroxyalkyl-1,3-propanediol, wherein said alkyl is preferably a C1-C8 alkyl. More preferred embodiments of said 2,2-substituted 1,3-propanediol and said dimer, trimer and polymer thereof include neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, trimethylolethane, trimethylolbutane, trimethylolpropane, pentaerythritol, di-trimethylolpropane and di-pentaerythritol. Said alkoxylated species are preferably selected from the group consisting of trimethylolethane, trimethylolpropane, trimethylolbutane, pentaerythritol, di-trimethylolpropane and ethoxylated and / or propoxylated di-pentaerythritol.

In especially preferred embodiments of the present invention, said ester is a tri-ester or tetraester of a said 2-alkyl-2-hydroxyalkyl-1,3-propanediol or a said 2,2-dihydroxyalkyl-1,3-propanediol or a said dimer , polymer trimer thereof, such as an esterification product, between 2-propylheptanoic acid and pentaerythritol, trimethylolpropane or di-trimethylolpropane, having a trimester or tetraester content of at least 95%, such as at least 97% , in weigh.

Without further elaboration, it is believed that one skilled in the art can use, using the foregoing description, the present invention to its full extent. Therefore, the following specific preferred embodiments should be interpreted as merely illustrative and not limiting the rest of the disclosure in any way. The following examples 1 and 2 refer to the preparation of ester oils according to embodiments of the present invention and example 3 to a comparative ester oil outside the scope of said invention. Examples 4 and 5 and Table 1 present evaluations of prepared esters.

Example 1

120.9 g of pentaerythritol, 733.8 g of 2-propylheptanoic acid, 2.5 g of p-toluenesulfonic acid were charged as catalyst and 43.0 g of n-octane as azeotropic solvent in a reaction vessel equipped with a mechanical stirrer , nitrogen purge, heating device, condensers and a Dean-Stark water trap. The reaction mixture was heated rapidly to 170 ° C and heating was subsequently continued at a gradient of 20 ° C / min until an esterification temperature of 235 ° C was reached. It was then allowed to continue the esterification until the analysis by GC showed less than 1% of triester (ester having an unreacted hydroxyl group) in the reaction mixture. 15.6 g of active carbon were then added to control the color alteration and vacuum was applied for evaporation of the azeotropic solvent and excess carboxylic acid. The mixture was cooled to 50 ° C, when a reaction product having an acid number of less than 3 mg of KOH / g was obtained and then 14.6 g of a 10% NaOH solution were added to the reaction mixture. % (ac.). Vacuum was applied once more and the reaction mixture was reheated to 100 ° C for dehydration. The resulting reaction product was finally filtered to provide a pale yellow ester product having the following properties.

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144 APHA 0.04 mg KOH / g 0.23 mg KOH / g 97% by weight.

Example 2

Color:

Acidity index:

Hydroxyl index:

Tentaester content of pentaerythritol:

Example 1 was repeated with the difference that pentaerythritol was replaced by the same amount of trimethylolpropane and that 561.5 g of 2-propylheptanoic acid was charged instead of 733.8 g, providing a yellow ester product pale that had the following properties.

Color: 44 APHA

Acidity index: 0.02 mg of KOH / g

Hydroxyl Index: 0.52 mg KOH / g

Tetraester content of pentaerythritol: 97% by weight.

Example 3 (comparative)

Example 1 was repeated with the difference that 2-propylheptanoic acid was replaced by 613.4 g of 2-ethylhexanoic acid, providing a pale yellow ester product having following properties.

Color: 5 APHA

Acidity index: 0.03 mg of KOH / g

Hydroxyl Index: 0.52 mg KOH / g

Tetraester content of pentaerythritol: 98.7% by weight.

Example 4

The ester products obtained (lubricating base oils) in Examples 1,2 and 3 (comparative) were evaluated for important properties in lubricants. The ester products according to embodiments of the present invention exhibited substantially improved properties. The result is provided in table 1 below.

Example 5

The ester products obtained in example 1 and example 3 (comparative) were placed overnight in a freezer at -18-20 ° C. After that time, the product of example 1 was a highly viscous transparent liquid, while the product of example 3 was an opaque waxy solid.

Table 1

 Property

 Viscosity Viscosity Value Pour point Evaporation point

 at 40 ° C, cSt at 100 ° C, of the index of ° C inflammation in NOACK

 cSt closed cup viscosity% w / w

 Standard ° C

 Standard EN Standard EN Standard ASTM D 5950 Standard Standard

 IS03104 ISO 3104 ASTM D 2270 EN IS0 2492 CEC L40-93-B

 Ex. 1

 57.2 7.83 110 <-56 270 1.7

 Ex 2

 34.4 5.44 89 <-52 244 5.0

 j_____

 46.2 6.39 82 -6 178 3.4

Claims (14)

2. 10 3. 15 Four. 20 5. 6. 25 7. 30 8. 9. 35 10. 40 eleven. 12. 45 13. fifty 14. fifteen. Use of a lubricating base oil, comprising at least one ester obtained by esterification of 2-propylheptanoic acid with at least one 2,2-substituted 1,3-propanediol and / or at least one dimer, trimer or polymer thereof and / or at least one alkoxylated species of said 2,2-substituted 1,3-propanediol or said dimer, trimer or polymer thereof, in the production of a lubricant for internal combustion engines and turbine engines. Use of a lubricating base oil according to claim 1, characterized in that said 1,3-propanediol 2.2-substituted is a 2,2-dialkyl-1,3-propanediol, a 2-alkyl-2-hydroxyalkyl-1,3-propanediol or a 2,2-dihydroxyalkyl-1,3-propanediol. Use of a lubricating base oil according to claim 2, characterized in that said alkyl is a C-i-Ca alkyl. Use of a lubricating base oil according to any one of claims 1-3, characterized in that said 2,2-substituted 1,3-propanediol is neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, trimethylolethane, trimethylolbutane, trimethylolpropane or pentaerythritol. Use of a lubricating base oil according to claim 1, characterized in that said dimer is di-trimethylolpropane or di-pentaerythritol. Use of a lubricating base oil according to claim 1, characterized in that said alkoxylated species is a trimethylolethane, trimethylolpropane, trimethylolbutane, pentaerythritol, di-trimethylolpropane or ethoxylated and / or propoxylated dipentaerythritol. Use of a lubricating base oil according to any of claims 2-6, characterized in that said lubricating base oil comprises a 2-alkyl-2-hydroxyalkyl-1,3-propanediol triester or a tetraester of a dimer thereof. Use of a lubricating base oil according to any of claims 2-6, characterized in that said lubricating base oil comprises a tetraester of 2,2-dihydroxyalkyl-1,3-propanediol. Use of a lubricating base oil according to any of claims 1-8, characterized in that said lubricating base oil comprises a trimethylolpropane triester or a pentaerythritol or di-trimethylolpropane tetraester. Use of a lubricating base oil according to any of claims 1-9, said engine being a car engine, an aviation engine, a ship engine or a stationary engine. Use according to claim 10, said engine being an Otto engine, a diesel engine, a Wanckel or a jet engine. Use according to claim 10, said motor being a two-stroke engine. Lubricating base oil characterized in that it is a lubricating base oil of a turbine or automobile, aviation, ship or stationary engine, comprising at least one ester obtained by esterification of 2-propylheptanoic acid with (i) at least one 1,3-substituted 1,3-propanediol and / or at least one dimer, trimer or polymer thereof, wherein said 2,2-substituted 1,3-propanediol is neopentyl glycol, 2-butyl-2-ethyl-1 , 3-propanediol, trimethylolethane or trimethylolbutane, and / or (ii) at least one alkoxylated species of a 1.3-2,2-substituted propanediol or a dimer, trimer or polymer thereof. Lubricating base oil according to claim 13, characterized in that said alkoxylated species of a 2,2-substituted 1,3-propanediol is an alkoxylated 2,2-dialkyl-1,3-propanediol, an alkoxylated 2-alkyl-2-hydroxyalkyl-1,3-propanediol or a 2,2-dihydroxyalkyl-1,3- alkoxylated propanediol. Lubricating base oil according to claim 14, characterized in that said alkyl is a C-i-Ca alkyl.