EP4097197B1 - Tcd-esters for low temperature liquid applications - Google Patents

Description

The present invention relates to the use of esters of octahydro-4,7-methano-1H-indene-5-methanol (TCD-M) or dimethanol (TCD-DM) with aliphatic C5 to C9 monocarboxylic acids with an odd C number Lubricant in low temperature applications. Furthermore, the present invention relates to low-temperature lubricant compositions comprising these esters. The scope of the invention is determined by the claims.

Modern refrigeration is largely based on the use of mechanical refrigerant compressors, in which a wide variety of refrigerants are condensed or compressed in a first process step. Compression usually induces a phase transition of the refrigerant from gaseous to liquid and the resulting heat is dissipated into the environment. In a second step, the liquid refrigerant is transferred to the cooling location and evaporated here, with the energy required for the evaporation then being withdrawn from this location. Depending on the device environment and the desired cooling performance, substances with high specific enthalpies of vaporization such as diethyl ether, ammonia, carbon dioxide, lower alkanes or halogenated hydrocarbons can be used as refrigerants, with the latter in particular justifiably becoming more and more in the background due to their climate-damaging effects.

To protect mechanical parts in low-temperature applications, such as refrigeration systems, lubricants must be used that can guarantee "smooth" and low-maintenance operation. A wide variety of substances are used as lubricants. For example, lubricants based on mineral oil or esters, such as dicarboxylic acid diesters and pentaerythritol tetraesters.

Alternatives can be found in the class of natural esters, such as rapeseed oil esters. Esters are characterized by good lubricating properties and, in contrast to mineral oil-based products, are generally more biodegradable. Ester oils which, in addition to sufficient lubricating properties as such, also have improved secondary properties, such as a large temperature working range, uniform rheological properties, sufficiently high viscosities and improved chemical stabilities, are not yet available.

A wide variety of approaches for lubricating oils in low-temperature applications such as refrigeration systems are discussed in the patent literature.

For example, this reveals DE 44 37 007 A1 biodegradable oligoesters, among other things, for use as lubricants with a kinematic viscosity of 50 to 50,000 mm ² /s at 40 ° C, the esters consisting of a tricyclic diol with 8 to 20 carbon atoms, a saturated, straight-chain or branched dicarboxylic acid with 4 to 20 carbon atoms and an aliphatic alcohol with 1 to 30 carbon atoms.

In another patent document, the EP 2 342 312 B1 , the use of a lubricant base mixture comprising at least one ester obtained by esterifying 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 2,2-substituted 1,3-propanediol or the dimer, trimer or polymer thereof, the lubricant being suitable for internal combustion engines and turbine engines.

Furthermore, the reveals EP 0 406 479 B1 the use of a lubricant for compressors using a chlorine-free fluorocarbon refrigerant which contains as a main component an ester or esters obtained by combining (a) neopentyl glycol with (b) a mixture of at least one straight-chain monovalent saturated fatty acid , which contains 5 to 10 carbon atoms, and at least one branched-chain saturated fatty acid which contains 7 to 9 carbon atoms, the proportion of branched, monovalent, saturated fatty acid being not less than 50 mol% of the total amount of monovalent, saturated fatty acid used fatty acid.

Other lubricant compositions based on TEC esters are available, for example, in EP0445611A1 disclosed. General ester compounds, also based on TCD esters, are used in the EP3098216A1 and the DE2917152A1 described. Despite the already known uses of substances as lubricants at low temperatures, there is still increased interest in other classes of substances that are able to function as lubricants in low-temperature applications. Furthermore, there is interest in low-temperature lubricant compositions which, in addition to a sufficient lubricant effect, also have a broader temperature operating range with consistent rheological properties. It is therefore the object of the present invention to provide a new use for esters which overcomes the disadvantages of the previously known substances, at least in part, and allows reliable use over a wide temperature range with consistent lubricant properties.

According to the invention, the use of the esters according to the invention as lubricants in low-temperature applications is therefore proposed according to claim 1. Furthermore, a low-temperature lubricant composition according to claim 9 is proposed. Advantageous developments of the use and the composition are specified in the respective dependent claims. They can be combined in any way, unless the context clearly indicates otherwise. According to the invention, the use of esters of octahydro-4,7-methano-1H-indene-5-methanol or of octahydro-4,7-methano-1H-indene-5-dimethanol with aliphatic, straight-chain, C5 to C9 monocarboxylic acids with odd C number as a lubricant in low temperature applications. Surprisingly, it has been shown that the above-mentioned group of TCD mono- and di-esters are particularly suitable for use as lubricants in applications which are also operated at lower temperatures. In particular, the esters have particularly suitable rheological and thermal properties over a wide temperature range, and in particular even at very low temperatures. The esters have a particularly low solidification point and only a slight change in viscosity as a function of temperature. Furthermore, the esters that can be used according to the invention can have a sufficiently high overall viscosity so that the lubricant film is not expected to break off, even in difficult environmental conditions in high and low temperature ranges. These viscosity properties can help reduce the maintenance requirements of refrigeration compressors or generally mechanical engines or gearboxes to increase the longevity of the mechanical components. Another advantage that can be mentioned is that the lubricants according to the invention are chemically very stable.

The group of esters according to the invention can be used as lubricants in low temperature applications. Lubricants, also known as lubricants, are used for lubrication and are used to reduce friction and wear between mechanically moving parts. In the present case, the moving parts are mechanical components of a motor or transmission or similar moving mechanical structures. Low-temperature applications include, for example, refrigeration systems or refrigeration machines, which use a compressor to transport heat energy from a colder location that requires further cooling to a warmer environment. The purpose of a refrigeration system is to cool a specific area of the system to a temperature below the ambient temperature. The applications are low-temperature applications in those cases in which the lubricated mechanical parts required for the application are designed, at least temporarily, at a temperature of less than or equal to 0 ° C, preferably less than -20 ° C and further preferably to be operated at -40°C.

oder aber dessen entsprechendes Dialkohol-Derivat Octahydro-4,7-methano-1H-indendimethanol (TCD DM)

eingesetzt werden. Die Abkürzung TCD steht für TriCycloDecan. Entsprechend des zur Veresterung eingesetzten TCD-Grundgerüstes können sich demzufolge Mono-Ester im Falle des TCD M oder aber auch die Di-Ester im Falle des Einsatzes von TCD DM ausbilden. Durch die fehlende spezifische Angabe der Position der Alkoholgruppen im TCD DM ist zudem verdeutlicht, dass für das TCD DM Grundgerüst unterschiedliche Strukturisomere existieren können.The use of esters according to the invention is based on esters of octahydro-4,7-methano-1H-indene-5-methanol or of octahydro-4,7-methano-1H-indene-dimethanol with aliphatic C5 to C9 monocarboxylic acids with odd C Number Octahydro-4,7-methano-1H-indene-5-methanol (TCD M) according to the following structural formula can be used as alcohol components of the esters according to the invention

or its corresponding dialcohol derivative octahydro-4,7-methano-1H-indenedimethanol (TCD DM)

be used. The abbreviation TCD stands for TriCycloDecane. Depending on the TCD basic structure used for esterification, mono-esters can be formed in the case of TCD M or di-esters in the case of TCD DM. The lack of specific information about the position of the alcohol groups in the TCD DM also makes it clear that different structural isomers can exist for the TCD DM skeleton.

oder

The esters according to the invention result from the above-mentioned alcohols as the basic structure and aliphatic C2 to C18 monocarboxylic acids, which have formed an ester compound (R`-CO-OR) with one or, if present, with both alcohol groups of the basic structure. The following basic ester structures may therefore be suitable for use according to the invention:

or

The aliphatic radicals R and R' of the monocarboxylic acids can and can have 5 to 9 carbon atoms in the alkyl chain, including the carbon atom of the carboxylic acid group for example, be selected from the group of pentane and heptane.

The carboxylic acids that can be used according to the invention are unbranched. Carboxylic acids not according to the invention are, in particular, the polycarboxylic acids with more than one carboxylic acid group, the cyclic and aromatic or unsaturated alkene or alkyne carboxylic acids.

For use, the monocarboxylic acids are selected from the group consisting of straight-chain C5 to C9 monocarboxylic acids with an odd number of C or mixtures thereof. In particular, the TCD esters with shorter aliphatic chains of the corresponding shorter-chain monocarboxylic acids can be particularly suitable for lubricant applications. The esters from these carboxylic acids can in particular have a low solidification point and a sufficient viscosity over a wide temperature range. To describe the solidification point, the pour point is also used in this application, which indicates the temperature at which the lubricants are just still able to flow, i.e. shortly before the esters solidify. The solidification point of these esters can be in particular lower than -35 ° C, preferably lower than -50 ° C and further preferably lower than -70 ° C. The particularly preferred viscosity properties can, for example, consist in the fact that this group of esters has a preferred viscosity index. The viscosity index of this group of esters can preferably be greater than 40, further preferably greater than 50 and further preferably greater than 70. This group of esters is also characterized by the fact that the good lubricating properties are retained at both high and very low temperatures.

The monocarboxylic acids from the are suitable for use Group of straight-chain monocarboxylic acids selected. Surprisingly, it has been found that the esters according to the invention made from straight-chain monocarboxylic acids can have particularly lower solidification points. The solidification points of these esters can be significantly lower than that Solidification points of esters obtained from branched monocarboxylic acids.

Furthermore, these esters can also have improved viscosity properties. For example, the viscosity index of esters of these monocarboxylic acids can be significantly higher than the viscosity index of esters obtained from branched monocarboxylic acids.

For use, the monocarboxylic acids are selected from the group of monocarboxylic acids with an odd number of carbons. In particular, the solidification points of esters with monocarboxylic acids, which have an odd C number in the aliphatic chain, can have particularly suitable lubricant properties. For example, the solidification point of these esters can be significantly lower than the solidification point of esters made from monocarboxylic acids with an aliphatic chain with an even C number.

The monocarboxylic acids from the group of C5 to C9 monocarboxylic acids are selected for use. The group of esters consisting of TCD and monocarboxylic acids with a medium carbon number can help ensure that the lubricant only solidifies at particularly low temperatures. In addition, these esters can have a particularly suitable viscosity index, the viscosity index of these compounds preferably being greater than 70. These physical and rheological properties can contribute to obtaining improved lubricating properties at lower temperatures.

For use, the monocarboxylic acids are selected from the group of straight-chain, C5 to C9 monocarboxylic acids with an odd number of C. Especially the aliphatic monocarboxylic acids with a carbon chain with 5, 7 or 9 carbon atoms can lead to particularly suitable lubricants as the ester component of TCD. These monocarboxylic acids can lead to esters with particularly low solidification points either with the TCD mono-alcohol or with the diol. These esters can also have a suitable density with values of above 1 g/cm ³ . Furthermore, these esters of monocarboxylic acids with an average C number can have a particularly suitable, high viscosity index.

In a preferred embodiment of the use, the esters can be esters of octahydro-4,7-methano-1H-indene-5-methanol. The esters of TCDs with only one alcohol group have proven to be particularly suitable in the area of lubricants for refrigeration systems or other low-temperature applications. These esters can have particularly low solidification points of less than -70 °C. Furthermore, these esters can show a particularly suitable viscosity profile, the viscosity index of these esters being in the range of greater than or equal to 100. These properties can mean that refrigeration systems, engines, gearboxes or turbines can be operated with particularly low maintenance and a long service life, even at sub-zero temperatures.

For use, the esters are esters of straight-chain C5 to C9 monocarboxylic acids with an odd number of C.

In particular, the monoesters of TCD with straight-chain monocarboxylic acids with a medium carbon number can lead to particularly suitable lubricants. This group of esters can in particular have very low solidification points and a high viscosity index. Furthermore, these esters have a particularly suitable, low basic viscosity, which in particular means that the absolute viscosity of the esters does not become too high even at very low temperatures. Even at very cold temperatures, a sufficiently low-viscosity lubricant film is formed, which can protect mechanical parts very well from wear.

Also according to the invention are low-temperature lubricant compositions comprising greater than or equal to 70% by weight and less than or equal to 100% by weight of esters of octahydro-4,7-methano-1H-indene-5-methanol with aliphatic, straight-chain C7 to C9 monocarboxylic acids with an odd number of C or the octahydro-4,7-methano-1H-indene-5-dimethanol with aliphatic, straight-chain C5 to C9 monocarboxylic acids with an odd number of C or mixtures of these monocarboxylic acids. Also according to the invention are low-temperature lubricant compositions which contain a high proportion by weight of the esters which can be used according to the invention. These lubricant compositions can be used over a wide temperature range, have a suitable viscosity and solidify only at very low temperatures. In addition to this wide temperature range of application, these lubricants are particularly effective at low temperatures suitable viscous properties so that the mechanical parts of refrigeration systems can be very efficiently protected against wear even during long-term use at very low temperatures. The lubricant compositions are also chemically extremely stable, so that only a small amount of chemical degradation of the lubricant occurs even under unfavorable operating conditions. For the further advantages of the lubricant compositions according to the invention, reference is explicitly made to the advantages of the use of the lubricant esters according to the invention. In addition to the esters that can be used according to the invention, the lubricant compositions can also contain other additives known to those skilled in the art.

In a preferred embodiment of the lubricant composition, the esters can be esters of octahydro-4,7-methano-1H-indene-5-methanol with aliphatic, straight-chain C5 to C9 monocarboxylic acids with an odd C number or mixtures of these. Lubricant compositions made from monoesters of TCDs with the above-mentioned group of monocarboxylic acids can have particularly suitable lubricant properties for cold applications. Lubricants with these esters can have particularly suitable viscous and chemical properties, such as a very low solidification point and a suitable viscosity even at low temperatures. These lubricant compositions can therefore be operated in a wide temperature range and lead to improved service life of refrigeration machines. The lubricant compositions can preferably consist of greater than or equal to 85 percent by weight, and further greater than or equal to 95 percent by weight of the esters that can be used according to the invention.

• Fig. 1 ein Diagramm zur Abhängigkeit des Erstarrungspunktes von TCD M-Estern als Funktion der C-Anzahl in den Alkylketten der Monocarbonsäuren;
• Fig. 2 ein Diagramm zur Abhängigkeit des Viskositätsindex von TCD M-Estern als Funktion der C-Anzahl in den Alkylketten der Monocarbonsäuren;
• Fig. 3 ein Diagramm zur Abhängigkeit der kinematischen Viskosität von TCD M-Estern als Funktion der C-Anzahl in den Alkylketten der Monocarbonsäuren;
• Fig. 4 ein Diagramm zur Abhängigkeit des Erstarrungspunktes von TCD DM-Estern als Funktion der C-Anzahl in den Alkylketten der Monocarbonsäuren;
• Fig. 5 ein Diagramm zur Abhängigkeit des Viskositätsindex von TCD DM-Estern als Funktion der C-Anzahl in den Alkylketten der Monocarbonsäuren;
• Fig. 6 ein Diagramm zur Abhängigkeit der kinematischen Viskosität von TCD DM-Estern als Funktion der C-Anzahl in den Alkylketten der Monocarbonsäuren.

Further details, features and advantages of the subject matter of the invention result from the subclaims as well as from the following description, the figures and the associated examples. It shows the:

• Fig. 1 a diagram of the dependence of the solidification point of TCD M esters as a function of the number of carbons in the alkyl chains of the monocarboxylic acids;
• Fig. 2 a diagram of the dependence of the viscosity index of TCD M esters as a function of the number of carbons in the alkyl chains of the monocarboxylic acids;
• Fig. 3 a diagram of the dependence of the kinematic viscosity of TCD M esters as a function of the number of carbons in the alkyl chains of the monocarboxylic acids;
• Fig. 4 a diagram of the dependence of the solidification point of TCD DM esters as a function of the number of carbons in the alkyl chains of the monocarboxylic acids;
• Fig. 5 a diagram of the dependence of the viscosity index of TCD DM esters as a function of the number of carbons in the alkyl chains of the monocarboxylic acids;
• Fig. 6 a diagram of the dependence of the kinematic viscosity of TCD DM esters as a function of the number of carbons in the alkyl chains of the monocarboxylic acids.

The Figure 1 shows the dependence of the solidification point (pour point) in °C of TCD M esters as a function of the number of carbons in the alkyl chains of the monocarboxylic acids used for ester formation. The results for esters with branched (triangles) or straight-chain (circles) alkyl chains are presented differently. The solidification point was measured according to ASTM D 5950 / D 5985. It can be clearly seen that the solidification points of the mono-esters according to the invention can be achieved below -60 ° C. Furthermore, it can be seen that compared to the esters with a branched alkyl chain, esters from monocarboxylic acids with an unbranched alkyl chain with the same number of C in the alkyl chain provide lower solidification points. This is also confirmed by a comparison of the values for nC5-TCD M esters and 2 MB and 3 MB. In comparison to the esters from carboxylic acids with an even number of Cs, the esters with odd numbers of Cs in the alkyl chain have lower solidification points for the mono-esters.

The Figure 2 shows the dependence of the viscosity index of TCD M esters as a function of the number of carbons in the alkyl chains of the monocarboxylic acids used for ester formation. The results for esters with branched (triangles) or straight-chain (circles) alkyl chains are presented differently. The viscosity index results from ASTM D 2270. It can be clearly seen that the viscosity index of the mono-esters according to the invention is over 40. Furthermore, it can be seen that compared to the esters with an unbranched alkyl chain, esters from monocarboxylic acids with a branched alkyl chain with the same number of C in the alkyl chain provide lower viscosity indices. Compared to the esters Carboxylic acids with an even number of carbons have higher viscosity indices for the mono-esters than the esters with odd numbers of carbons in the alkyl chain.

The Figure 3 shows the dependence of the kinematic viscosity at 20°C of TCD DM esters as a function of the C number in the alkyl chains of the monocarboxylic acids used for ester formation. The results for esters with branched (triangles) or straight-chain (circles) alkyl chains are presented differently. The kinematic viscosity at different temperatures was obtained according to ASTM D 445. It can be clearly seen that the kinematic viscosity of the mono-esters according to the invention is over approximately 10 mm ² /s. Furthermore, it can be seen that compared to the esters with an unbranched alkyl chain, esters from monocarboxylic acids with a branched alkyl chain with the same number of C in the alkyl chain provide higher kinematic viscosities. The increase in kinematic viscosity is also greater than the increase in viscosity for the n-alkyl esters. For the data point with a C number of 5, 2 different stereoisomers were measured (TCD DM-2MB ester and TCD DM-3MB ester with MB methylbutyric acid).

The Figure 4 shows the dependence of the solidification point (pour point) in °C of TCD DM esters as a function of the number of carbons in the alkyl chains of the monocarboxylic acids used for ester formation. The results for esters with branched (triangles) or straight-chain (circles) alkyl chains are presented differently. It can be clearly seen that the solidification points of the di-esters according to the invention can be achieved below -40 ° C. Furthermore, it can be seen that, compared to the esters with a branched alkyl chain, esters from monocarboxylic acids with an unbranched alkyl chain with the same number of C in the alkyl chain provide lower solidification points (for example C4). In comparison to the esters from carboxylic acids with an even number of Cs, the esters with odd numbers of Cs in the alkyl chain have lower solidification points for the di-esters.

The Figure 5 shows the dependence of the viscosity index of TCD DM esters as a function of the number of carbons in the alkyl chains of the monocarboxylic acids used for ester formation. The results for esters with branched (triangles) or straight-chain (circles) alkyl chains are presented differently. It can be clearly seen that the viscosity index of the di-esters according to the invention is over 20. Furthermore, it can be seen that in Compared to the esters with an unbranched alkyl chain, esters from monocarboxylic acids with a branched alkyl chain with the same number of carbons in the alkyl chain provide lower viscosity indices. In comparison to the esters from carboxylic acids with an even number of Cs, the esters with odd numbers of Cs in the alkyl chain have higher viscosity indices for the di-esters.

The Figure 6 shows the dependence of the kinematic viscosity at 20°C of TCD DM esters as a function of the C number in the alkyl chains of the monocarboxylic acids used for ester formation. The results for esters with branched (triangles) or straight-chain (circles) alkyl chains are presented differently. It can be clearly seen that the kinematic viscosity of the di-esters according to the invention is over approximately 50 mm ² /s. Furthermore, it can be seen that compared to the esters with an unbranched alkyl chain, esters from monocarboxylic acids with a branched alkyl chain with the same number of C in the alkyl chain provide lower kinematic viscosities. The increase in kinematic viscosity of the i-alkyl esters is greater than the increase in viscosity for the n-alkyl esters. For the data point with a C number of 5, 2 different stereoisomers were measured (TCD DM-2MB ester and TCD DM-3MB ester with MB methylbutyric acid).

Representation of the esters

1. 1. Veresterung von Alkohol und Säure mit einem 10%igen molaren Säureüberschuss bis zum Erreichen des theoretischen Wasserabzugs. Es wurde Titanisopropoxid als Katalysator (0,45 mmol auf 1 mol Diol) eingesetzt. In der Reaktion wurde Toluol (40 Gew.-% bezogen auf TCD Alkohol) als Wasserschlepper eingesetzt. Zum Erreichen höherer Temperaturen in der Veresterung kann auf die Zugabe von Toluol verzichtet werden.
2. 2. Main-Strip zum Entfernen überschüssiger Säure am Vakuum;
3. 3. Steam-Strip mit Aktivkohle zum Zersetzen des Katalysators und zur Entfärbung mit anschließender Trocknung;
4. 4. Ggf. Neutralisation mit NaOH zur Reduzierung der Säurezahl und anschließende Trocknung.

The esters were prepared as follows:

1. 1. Esterification of alcohol and acid with a 10% molar acid excess until the theoretical water removal is reached. Titanium isopropoxide was used as a catalyst (0.45 mmol per 1 mol of diol). Toluene (40% by weight based on TCD alcohol) was used as a water carrier in the reaction. To achieve higher temperatures in the esterification, the addition of toluene can be dispensed with.
2. 2. Main strip for removing excess acid on the vacuum;
3. 3. Steam strip with activated carbon to decompose the catalyst and decolorize with subsequent drying;
4. 4. If necessary, neutralize with NaOH to reduce the acid number and then dry.

Claims (4)

1. Use of esters of octahydro-4,7-methano-1H-indene-5-methanol or octahydro-4,7-methano-1H-indene-5-dimethanol and aliphatic, straight-chain C5 to C9 monocarboxylic acids comprising an odd C-number as lubricants in low temperature applications.
2. Use according any one of the preceding claims, wherein the esters are esters of octahydro-4,7-methano-1H-indene-5-methanol.
3. Low-temperature lubricant compositions comprising greater than or equal to 70% by weight and less than or equal to 100% by weight esters of octahydro-4,7-methano-1H-indene-5-methanol and aliphatic, straight-chain C7 to C9 monocarboxylic acids comprising an odd C-number or esters of octahydro-4,7-methano-1H-indene-5-dimethanol and aliphatic, straight-chain C5 to C9 monocarboxylic acids comprising an odd C-number or mixtures of these monocarboxylic acids.
4. Lubricant compositions according to claim 3, wherein the esters are esters of octahydro-4,7-methano-1H-indene-5-methanol and aliphatic, straight-chain C7 to C9 monocarboxylic acids comprising an odd C-number or mixtures thereof.

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