Ester mixture, and lubricating base oil and lubricant composition comprising the same

Abstract

Proposed is an ester mixture comprising a diester and a monoester, in which the diester comprises a first ester having the chemical structure represented by (A-C-A), a second ester having the chemical structure represented by (B—C—B), a third ester having the chemical structure represented by (A-C—B), or a combination thereof, in which A is derived from a first alcohol, which is an alcohol containing at least one alkoxy group, B is derived from a second alcohol, which is a hydrocarbyl alcohol, and C is derived from a dicarboxylic acid. Also, a lubricating base oil and a lubricant composition comprising the ester mixture are proposed.

Description

CROSS REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to Korean Patent Application No. 10-2025-0001621, filed Jan. 6, 2025, the entire contents of which are incorporated herein for all purposes by this reference.BACKGROUNDTechnical Field

[0002] The embodiments of the present disclosure relate to a novel ester mixture, a lubricating base oil, and a lubricant composition including the same.Description of the Related Art

[0003] A lubricating base oil refers to the raw material used for producing a lubricating oil product. In general, high-quality lubricating base oil has a high viscosity index, excellent stability (resistance to oxidation, heat, UV, etc.), and low volatility. The American Petroleum Institute (API) classifies lubricating base oils by quality, as shown in Table 1 below.TABLE 1ClassificationSulfur (%)Saturate (%)Viscosity Index (VI)Group I>0.03<9080 ≤ VI < 120Group II≤0.03≥9080 ≤ VI < 120Group III≤0.03≥90120 ≤ VIGroup IVAll polyalphaolefins (PAOs)Group VAll other lubricating base oils notin Group I, II, III, or IV

[0004] In industry, the use of lubricating oils is essential to reduce friction and wear on various machinery and equipment. In particular, in automobiles, reducing friction-induced energy losses in engines or motors can improve fuel or energy efficiency. Lubricants contribute to reducing such energy losses.

[0005] The foregoing is intended merely to aid in the understanding of the background of the present disclosure, and is not intended to mean that the present disclosure falls within the purview of the related art that is already known to those skilled in the art.SUMMARY

[0006] According to an embodiment of the present disclosure, there is provided a novel ester mixture. According to another embodiment of the present disclosure, there is provided a lubricating base oil and a lubricant composition which include the ester mixture.

[0007] The ester mixture of the present disclosure exhibits excellent biodegradability and low human toxicity, thereby contributing to enhanced environmental friendliness of products when used in the field of lubricant technology.

[0008] An embodiment of the present disclosure is an ester mixture including a diester and a monoester, wherein the diester may include a first ester having the chemical structure represented by (A-C-A); or a second ester having the chemical structure represented by (B—C—B); or a third ester having the chemical structure represented by (A-C—B); or any combination thereof, wherein A may be derived from a first alcohol containing at least one alkoxy group, B may be derived from a second alcohol, which is a hydrocarbyl alcohol, and C may be derived from a dicarboxylic acid.

[0009] In an embodiment, the first alcohol may be represented by Formula 1,

[0010] wherein R1 may be an alkylene group, an alkenylene group, or an alkynylene group, n may be an integer equal to or greater than 1, and R2 may be an alkyl group, an alkenyl group, or an alkynyl group.

[0011] In an embodiment, the R1 may be a C1-C30 alkylene group, the n may be an integer from 1 to 20, and the R2 may be a C1-C30 alkyl group, a C2-C30 alkenyl group, or a C2-C30 alkynyl group.

[0012] In an embodiment, the R1 may be a C1-C8 alkylene group, the n may be an integer from 1 to 5, and the R2 may be a C1-C12 alkyl group, a C2-C12 alkenyl group, or a C2-C12 alkynyl group.

[0013] In an embodiment, the second alcohol may be represented by Formula 2,

[0014] wherein R3 may be a hydrocarbyl group.

[0015] In an embodiment, the R3 may be a C1-C30 alkyl group, a C2-C30 alkenyl group, or a C2-C30 alkynyl group.

[0016] In an embodiment, the R3 may be a C1-C24 alkyl group, a C2-C24 alkenyl group, or a C2-C24 alkynyl group.

[0017] In an embodiment, the dicarboxylic acid may be oxalic acid or may be represented by Formula 3,

[0018] wherein, R4 may be an alkylene group, an alkenylene group, or an alkynylene group.

[0019] In an embodiment, the R4 may be a C1-C30 alkylene group.

[0020] In an embodiment, the R4 may be a C1-C12 alkylene group.

[0021] In an embodiment, the monoester may be a fourth ester having the chemical structure represented by (D-E), wherein D may be derived from a monocarboxylic acid and E may be derived from a hydrocarbyl alcohol.

[0022] In an embodiment, the monocarboxylic acid may be represented by Formula 4,

[0023] wherein R5 may be a substituted or unsubstituted hydrocarbyl group.

[0024] In an embodiment, the R5 may be a C1-C30 alkyl group, a C2-C30 alkenyl group, or a C2-C30 alkynyl group.

[0025] In an embodiment, the R5 may be a C1-C24 alkyl group, a C2-C24 alkenyl group, or a C2-C24 alkynyl group.

[0026] In an embodiment, the hydrocarbyl alcohol may be represented by Formula 5,

[0027] wherein R6 may be a substituted or unsubstituted hydrocarbyl group.

[0028] In an embodiment, the diester may include: a first ester, a second ester, and a third ester.

[0029] In an embodiment, the diester may include: 10 to 40 mol % of a first ester, 10 to 40 mol % of a second ester, and 30 to 70 mol % of a third ester.

[0030] In an embodiment, a weight ratio of the diester to the monoester in the mixture may be 1:8 to 8:1.

[0031] In an embodiment, the ester mixture may exhibit at least one of the following characteristics: a traction coefficient equal to or less than 0.04, measured under conditions: a load of 38 N, a temperature of 100° C., a speed of 1,000 mm / s, and a slide-to-roll ratio (SRR) of 100%; a flash point of equal to or greater than 200° C.; a kinematic viscosity at 100° C. of 2 to 10 cSt; a viscosity index of equal to or greater than 90; and a pour point of less than 0° C.

[0032] Another embodiment of the present disclosure is directed to a lubricating base oil including the aforementioned ester mixture.

[0033] Still another embodiment of the present disclosure is directed to a lubricant composition including the aforementioned ester mixture.

[0034] In an embodiment, the ester mixture can exhibit excellent friction-reducing performance. In an embodiment, the ester mixture can be used in a lubricant composition for automobiles, including electric vehicles. In an embodiment, the use of the ester mixture can improve fuel efficiency and mileage of vehicles. In an embodiment, the ester mixture can exhibit excellent low-temperature flowability. In an embodiment, the ester mixture can be utilized as a low viscosity base oil. In an embodiment, the ester mixture can exhibit excellent viscosity index. In an embodiment, the ester mixture can exhibit excellent miscibility. In an embodiment, the ester mixture can exhibit high biodegradability and low human toxicity, thereby contributing to enhanced environmental friendliness of products.DETAILED DESCRIPTION

[0035] Hereinbelow, the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, disclosed herein are specific embodiments that illustrate the principles of the present disclosure, and it should be emphasized that the embodiments of the present disclosure are not limited to the specific embodiments illustrated.Ester Mixture

[0036] One embodiment of the present disclosure provides an ester mixture. The ester mixture refers to a mixture of ester compounds. In an embodiment, the ester compound may be a product of an esterification reaction between an alcohol and a carboxylic acid.

[0037] The ester mixture includes a diester and a monoester. The diester contains two ester bonds. In the present disclosure, the diester includes a first ester having the chemical structure represented by (A-C-A); a second ester having the chemical structure represented by (B—C—B); a third ester having the chemical structure represented by (A-C—B); or a combination thereof. The monoester contains one ester bond.

[0038] Here, A is a group derived from a first alcohol, and the first alcohol is an alcohol containing at least one alkoxy group. Specifically, the A may be an alkoxy group derived from a first alcohol.

[0039] B is a group derived from a second alcohol, and the second alcohol is a hydrocarbyl alcohol. Specifically, the B may be an alkoxy group derived from a second alcohol.

[0040] C is a group derived from a dicarboxylic acid. Specifically, the C may be a diacyl group derived from a dicarboxylic acid.

[0041] Again, the first alcohol is an alcohol containing at least one alkoxy group. In an embodiment, the first alcohol may be represented by Formula 1 below. Specifically, the first alcohol may be one or more alcohols represented by Formula 1 below. More specifically, the first alcohol may be any combination of one to three types of alcohols included in the alcohols represented by Formula 1 below.

[0042] Here, R1 may be an alkylene group, an alkenylene group, or an alkynylene group. Specifically, the R1 may be a C1-C30 alkylene group, a C2-C30 alkenylene group, or a C2-C30 alkynylene group. From the perspective of oxidation stability, the R1 may be an alkylene group. More specifically, the R1 may be a C1-C30 alkylene group, more specifically a C1-C20 alkylene group, and even more specifically a C1-C8 alkylene group.

[0043] Additionally, n may be an integer equal to or greater than 1. The n may be specifically an integer from 1 to 20, more specifically an integer from 1 to 10, and even more specifically an integer from 1 to 5.

[0044] Additionally, R2 may be an alkyl group, an alkenyl group, or an alkynyl group. The R2 may be specifically a C1-C30 alkyl group, a C2-C30 alkenyl group, or a C2-C30 alkynyl group, more specifically a C1-C20 alkyl group, a C2-C20 alkenyl group, or a C2-C20 alkynyl group, and even more specifically a C1-C12 alkyl group, a C2-C12 alkenyl group, or a C2-C12 alkynyl group. From the perspective of oxidation stability, the R2 may be an alkyl group. Specifically, the first alcohol may be a polyalkoxylated alkyl alcohol.

[0045] When the numerical ranges of R1, n, and R2 in Formula 1 above exceed the ranges specified above, a problem may arise in that the pour point of the ester mixture increases, making application at low temperatures difficult. Also, the kinematic viscosity of the ester mixture increases significantly.

[0046] Furthermore, in the present disclosure, it should be understood that unless otherwise specified, the alkyl group, the alkenyl group, and the alkynyl group provided herein include a branched-chain or straight-chain alkyl group, alkenyl group, or alkynyl group.

[0047] In the present disclosure, it should be understood that unless otherwise specified, the alkyl group, the alkenyl group, and the alkynyl group provided herein include a substituted or unsubstituted alkyl group, alkenyl group, or alkynyl group. In the present disclosure, the term “substituted” refers to replacing at least one carbon or hydrogen atom constituting each group with another substance. In an embodiment, the alkyl group, the alkenyl group, or the alkynyl group may be an unsubstituted alkyl group, alkenyl group, or alkynyl group, respectively.

[0048] The second alcohol is a hydrocarbyl alcohol. In an embodiment, the second alcohol may be represented by Formula 2 below. Specifically, the second alcohol may be one or more alcohols represented by Formula 2 below. More specifically, the second alcohol may be any combination of one to three types of alcohols included in the alcohols represented by Formula 2 below.

[0049] Here, R3 is a hydrocarbyl group. The hydrocarbyl group may include an alkyl group, an alkenyl group, an alkynyl group, a phenyl group, or a benzyl group. Specifically, the R3 may be an alkyl group, an alkenyl group, or an alkynyl group. More specifically, the R3 may be a C1-C30 alkyl group, a C2-C30 alkenyl group, or a C2-C30 alkynyl group. Even more specifically, the R3 may be a C1-C24 alkyl group, a C2-C24 alkenyl group, or a C2-C24 alkynyl group. From the perspective of oxidation stability, the R3 may be an alkyl group. That is, the second alcohol may be an alkyl alcohol.

[0050] When the number of carbon atoms in R3 in Formula 2 above exceeds the above given range, a problem may arise in that the pour point of the ester mixture increases, making application at low temperatures difficult. Also, the kinematic viscosity of the ester mixture increases significantly.

[0051] As described above, the ester mixture includes a diester. The diester includes a product of an esterification reaction between the aforementioned first alcohol and / or second alcohol with a dicarboxylic acid. The dicarboxylic acid contains two carboxyl groups. The two carboxyl groups may each independently form an ester bond with the first alcohol or the second alcohol.

[0052] In an embodiment, the dicarboxylic acid may be oxalic acid or may be represented by Formula 3 below.

[0053] Here, R4 may be an alkylene group, an alkenylene group, or an alkynylene group. Specifically, the R4 may be a C1-C30 alkylene group, a C2-C30 alkenylene group, or a C2-C30 alkynylene group. From the perspective of oxidation stability, the R4 may be an alkylene group. Specifically, the R4 may be a C1-C30 alkylene group, more specifically a C1-C18 alkylene group. From the perspective of enhanced low-temperature performance, it may be a C1-C12 alkylene group.

[0054] When the number of carbon atoms in R4 in Formula 3 above exceeds the above given range, a problem may arise in that the pour point and kinematic viscosity of the ester mixture become excessively high, making it unsuitable for application as a lubricating oil product.

[0055] As a result of the esterification reaction of the first alcohol and / or the second alcohol with the dicarboxylic acid, not only a first ester and a second ester but also a third ester may be produced. That is, through the esterification reaction, an asymmetric ester may be formed, in which one carboxyl group of one dicarboxylic acid forms an ester bond with the first alcohol, while the other carboxyl group of the dicarboxylic acid forms an ester bond with the second alcohol. The presence of such an asymmetric ester in the mixture of the present disclosure simultaneously improves the friction-reducing performance and low-temperature performance that the embodiments of the present disclosure aim to achieve. Friction-reducing performance and low-temperature performance are generally known to have a trade-off relationship. For example, a longer carbon chain length in a compound improves its friction-reducing performance, but this raises its pour point and degrades its low-temperature performance. Without wishing to be bound by a particular theory, it is believed that the presence of the aforementioned asymmetric ester interferes with closed-packing of esters, thereby achieving excellent friction-reducing performance while also further lowering the pour point. In the present disclosure, the esterification reaction conditions are not particularly limited, and the esterification reaction may be carried out under known reaction conditions. Furthermore, the presence of the diester, unlike monoesters or polyol esters, enables the viscosity of the ester mixture to be controlled in a manner particularly suitable for application as a lubricating oil.

[0056] The diester includes a first ester, a second ester, a third ester, or a combination thereof. In an embodiment, the diester may include a first ester, a second ester, and a third ester. A diester mixture containing all the first to third esters may exhibit superior physical properties such as traction coefficient, kinematic viscosity, low-temperature flowability, viscosity index, and miscibility, compared to each of the first to third ester compounds alone. For example, the ester mixture may exhibit a lower pour point, a lower kinematic viscosity, and a better miscibility compared to the first ester alone. Additionally, the ester mixture may exhibit a lower traction coefficient, a lower pour point, and a better viscosity index compared to the second ester alone.

[0057] In an embodiment, the diester may include at least 30 mol % of a third ester. Specifically, the content of the third ester may be 30 to 70 mol %, more specifically 40 to 60 mol %, and even more specifically 45 to 55 mol %.

[0058] In another embodiment, the diester may include 10 to 40 mol % of a first ester, 10 to 40 mol % of a second ester, and 30 to 70 mol % of a third ester. Specifically, the content of the first ester may be 15 to 35 mol %, more specifically 20 to 30 mol %. Additionally, the content of the second ester may be specifically 15 to 35 mol %, more specifically 20 to 30 mol %. Additionally, the content of the third ester may be specifically 40 to 60 mol %, more specifically 45 to 55 mol %. By satisfying the composition of the above given numerical range, the diester may simultaneously achieve superior low-temperature performance and friction-reducing performance.

[0059] The ester mixture includes a monoester in addition to the diester. The monoester may be a fourth ester having the chemical structure represented by (D-E). Here, D is derived from a monocarboxylic acid and E is derived from a hydrocarbyl alcohol. The monocarboxylic acid contains one carboxyl group. Specifically, the D may be an acyl group derived from a monocarboxylic acid. Also, specifically, the E may be an alkoxy group derived from a hydrocarbyl alcohol.

[0060] In an embodiment, the monocarboxylic acid may be represented by Formula 4 below.

[0061] Here, R5 may be a substituted or unsubstituted hydrocarbyl group. The hydrocarbyl group may include an alkyl group, an alkenyl group, an alkynyl group, a phenyl group, or a benzyl group. Specifically, the R5 may be an alkyl group, an alkenyl group, or an alkynyl group. More specifically, the R5 may be a C1-C30 alkyl group, a C2-C30 alkenyl group, or a C2-C30 alkynyl group. Even more specifically, the R5 may be a C1-C24 alkyl group, a C2-C24 alkenyl group, or a C2-C24 alkynyl group. From the perspective of oxidation stability, the R5 may be an alkyl group.

[0062] When the number of carbon atoms in R5 in Formula 4 above exceeds the above given range, a problem may arise in that the low viscosity and pour point levels desired to be achieved by the embodiments of the present disclosure are not satisfied. This may make it difficult to manufacture a lubricating oil product containing a high content of the ester mixture.

[0063] In an embodiment, in the fourth ester having the chemical structure represented by (D-E), E may be derived from a third alcohol referred to as a hydrocarbyl alcohol, and the third alcohol may be represented by Formula 5 below.

[0064] Here, R6 may be a substituted or unsubstituted hydrocarbyl group.

[0065] The hydrocarbyl group may include an alkyl group, an alkenyl group, an alkynyl group, a phenyl group, or a benzyl group. Specifically, the R6 may be an alkyl group, an alkenyl group, or an alkynyl group. More specifically, the R may be a C1-C30 alkyl group, a C2-C30 alkenyl group, or a C2-C30 alkynyl group. Even more specifically, the R6 may be a C1-C24 alkyl group, a C2-C24 alkenyl group, or a C2-C24 alkynyl group. From the perspective of oxidation stability, the R6 may be an alkyl group. That is, the third alcohol may be an alkyl alcohol.

[0066] When the number of carbon atoms in R6 in Formula 5 above exceeds the above given range, a problem may arise in that the low viscosity and pour point levels desired to be achieved by the embodiments of the present disclosure are not satisfied. This may make it difficult to manufacture a lubricating oil product containing a high content of the ester mixture.

[0067] The combined use of the aforementioned diester and monoester improves the miscibility of the mixture and lowers the kinematic viscosity, thereby enhancing low viscosity, without compromising performance, which is advantageous over the use of the diester alone. Specifically, this combination does not increase the polarity of the ester mixture, enabling smooth blending with additives other than base oil when used in lubricant compositions. Such excellent miscibility also enables an increased content of the ester mixture in lubricating oil products. Furthermore, the combined use of the diester and monoester improves the flash point of the mixture without degrading its pour point, which is advantageous over the use of the monoester alone.

[0068] In an embodiment, the weight ratio of the diester to the monoester in the mixture may be 1:8 to 8:1. Specifically, the weight ratio may be 1:4 to 4:1. When the weight ratio exceeds the above given numerical range, a problem may arise in that it is difficult to achieve a synergistic effect expected from the combined use of the diester and monoester.

[0069] The ester mixture of the present disclosure may have a low traction coefficient. In the relevant technical field, a lower traction coefficient in lubricating products generally indicates superior performance in reducing friction in mechanical equipment, thereby potentially increasing the energy efficiency of the equipment.

[0070] In an embodiment, the ester mixture may have a traction coefficient equal to or less than 0.04, measured under the following conditions: a load of 38 N, a temperature of 100° C., a speed of 1,000 mm / s, and a slide-to-roll ratio (SRR) of 100%. Specifically, the traction coefficient may be equal to or less than 0.03, more specifically equal to or less than 0.025, and even more specifically equal to or less than 0.02. When the traction coefficient exceeds 0.04, a problem may arise in that the excellent friction-reducing performance desired to be achieved by the embodiments of the present disclosure is unrealizable.

[0071] The ester mixture may also have an excellent flash point. In an embodiment, the ester mixture may have a flash point equal to or greater than 200° C. The flash point in this disclosure may be measured according to ASTM D 93. Specifically, the ester mixture may have a flash point in a range of 200° C. to 300° C. For example, the flash point may be 200° C. to 210° C., 200° C. to 220° C., 200° C. to 230° C., 200° C. to 240° C., 200° C. to 250° C., 200° C. to 260° C., 200° C. to 270° C., 200° C. to 280° C., 200° C. to 290° C., or any subrange therebetween. When the flash point is less than 200° C., a problem may arise in that the ester mixture is highly likely to ignite at a lower temperature in the presence of an ignition source when used as a lubricating oil product.

[0072] The ester mixture may have a kinematic viscosity within a predetermined range. In an embodiment, the ester mixture may have a kinematic viscosity at 100° C. in a range of 2 to 10 cSt. Specifically, the kinematic viscosity may be 2 to 8 cSt, more specifically 2 to 7 cSt, and even more specifically 2 to 6 cSt.

[0073] Additionally, the ester mixture of the present disclosure may have a viscosity index (VI) within a predetermined range. In an embodiment, the ester mixture may have a viscosity index of equal to or greater than 90. Specifically, the viscosity index may be in a range of 90 to 250. More specifically, the viscosity index may be 150 to 250, or 150 to 230, and even more specifically 150 to 200.

[0074] Additionally, the ester mixture of the present disclosure may have a pour point within a predetermined range. In an embodiment, the ester mixture may have a pour point of less than 0° C. Specifically, the pour point may be in a range of −60° C. to less than 0° C. More specifically, the pour point may be −60° C. to −3° C., and even more specifically −60° C. to −6° C. From the perspective of enhancing low-temperature performance, the pour point may be −60° C. to −15° C.

[0075] The ester mixture may satisfy at least one of the traction coefficient, flash point, kinematic viscosity, viscosity index, and pour point within the above given numerical ranges. Specifically, the ester mixture may satisfy at least two of the properties listed above. In an embodiment, the ester mixture may satisfy the traction coefficient and kinematic viscosity within the above given numerical ranges. Specifically, the ester mixture may satisfy at least three of the properties listed above. In an embodiment, the ester mixture may satisfy the traction coefficient, kinematic viscosity, and pour point within the above given numerical ranges. More specifically, the ester mixture may satisfy all the properties listed above.

[0076] The ester mixture may constitute at least a portion of a lubricant composition, as will be described later. The mixture is expected to enhance the friction-reducing performance of the lubricant composition. Furthermore, the ester mixture is biodegradable due to the ester bond present in the compounds contained in the mixture. The use of the dicarboxylic acid increases the number of ester bonds within the compounds, further enhancing this biodegradability. Moreover, the use of the dicarboxylic acid further improves the pour point of the resulting ester mixture.Lubricating Base Oil and Lubricant Composition

[0077] Another embodiment of the present disclosure provides a lubricating base oil which includes the inventive ester mixture. The lubricating base oil may include the aforementioned ester mixture in various amounts, however, for maximizing the performance and the advantages obtained by the including of the ester compounds, the lubricating base oil may contain a high content of the ester mixture.

[0078] For example, the lubricating base oil may include the ester mixture in a content of at least 30 wt %, or at least 40 wt %, or at least 50 wt %, or at least 60 wt %, or at least 70 wt %, or at least 80 wt % based on the total weight of the lubricating base oil.

[0079] In a particular embodiment, the lubricating base oil may include the ester mixture in a content of at least 90 wt % based on the total weight of the lubricating base oil. The remaining lubricating base oil may include any known lubricating base oil without any particular limitation. For example, mineral lubricating base oils and / or synthetic lubricating base oils such as polyalphaolefin (PAO) may be used as the remaining lubricating base oil.

[0080] In another embodiment, the lubricating base oil may consist or consist essentially of the inventive ester mixture.

[0081] Still another embodiment of the present disclosure provides a lubricating oil product including the aforementioned ester mixture. The lubricating oil product refers to the finished lubricant that can be used in engines, machinery, industrial applications and the like. Hence, the ester mixture of the present disclosure may be included to serve as a lubricating base oil of a lubricant composition. The ester mixture may also be included to serve as an additive in a lubricating oil product (also referred to as finished lubricant, lubricant composition, or simply lubricant). Additionally, known additives used in the lubricant composition may be included as needed. Examples of the known additives may include, but are not limited to, antioxidants, corrosion inhibitors, dispersants, metal detergents, anti-wear agents, extreme pressure additives, anti-foaming agents, pour point depressants, viscosity index improvers, friction modifiers, emulsifiers, viscosity modifiers, and the like.

[0082] In its broadest aspects, the lubricant composition may include the ester mixture in a content of greater than 0 to 100 wt % based on the total weight of the lubricant composition. In an embodiment, for example, the lubricant composition may include the ester mixture in a content of about 0.1 to less than about 100 wt %, about 1 to less than about 100 wt %, about 2 to less than about 100 wt %, about 3 to less than about 100 wt %, about 4 to less than about 100 wt %, about 5 to less than about 100 wt %, about 6 to 15 less than about 100 wt %, about 7 to less than about 100 wt %, about 8 to less than about 100 wt %, about 9 to less than about 100 wt %, about 10 to less than about 100 wt %, about 0.1 to about 90 wt %, about 1 to about 90 wt %, about 2 to about 90 wt %, about 3 to about 90 wt %, about 4 to about 90 wt %, about 5 to about 90 wt %, about 6 to about 90 wt %, about 7 to about 90 wt %, about 8 to about 90 wt %, about 9 to about 90 wt %, or about 10 to about 90 wt %.

[0083] The lubricant composition of the present disclosure may exhibit excellent traction coefficient, flash point, kinematic viscosity, viscosity index, and / or pour point by including the ester mixture. Specifically, for each of the properties listed above, the lubricant composition may exhibit values equivalent to, or superior to, the numerical ranges described above for the ester mixture.

[0084] The ester mixture of the present disclosure may exhibit excellent miscibility.

[0085] The lubricant composition employing the ester mixture demonstrates excellent physical stability over time, making it suitable for extended storage without degradation. In an embodiment, the lubricant composition including the ester mixture may remain free of layer separation or coagulation even after 8 weeks from the date of mixing. The 8-week observation may be carried out at a temperature of about equal to or less than 25° C. Since the lubricant composition of the present disclosure does not undergo such layer separation or coagulation, it also offers advantages in terms of long-term storage stability.

[0086] The lubricant composition may be applicable across a wide range of machinery in which lubricating oil products are conventionally used. In an embodiment, the lubricant composition may be a lubricant composition for transportation vehicles. Specifically, the lubricant composition may be a lubricant composition for electric vehicles. The ester mixture of the present disclosure reduces friction-induced energy losses in electric vehicles by achieving a low traction coefficient and pour point. This contributes to improved energy efficiency.

[0087] It has been found that incorporating the ester mixture into the lubricant composition improves the friction-reducing performance of the entire composition. It also improves the overall its biodegradability.

[0088] Additional description of the embodiments of the present disclosure and comparative examples are provided below with reference to specific experimental examples. However, the following embodiments and comparative examples included in the experimental examples are only provided for illustrating the embodiments and do not limit the appended claims. It will be apparent to those skilled in the art that various modifications and alterations of the embodiments may be made without departing from the scope and technical concepts of the present disclosure. These modifications and alterations will fall within the scope of the present disclosure and appended claims.Examples1. Preparation of Ester Compound / Mixture(1) Diester A

[0089] Into a reaction vessel 130 g of sebacic acid, 84 g of 2-ethyl-1-hexanol, 122 g of diethylene glycol monohexyl ether, 2.4 g of p-toluenesulfonic acid monohydrate, and 362 mL of toluene were sequentially charged. The mixture was heated to 140° C. with stirring for 12 hours. After completion of the esterification reaction, 650 mL of a saturated aqueous sodium bicarbonate solution was added at room temperature to wash the reaction mixture, followed by extracting an organic solvent layer. Magnesium sulfate was then added to the organic solvent layer and stirred, followed by filtration and concentration to yield 306 g of a yellow ester mixture (diester A). The ester mixture had the following NMR fingerprint.

[0090] 1H NMR (500 MHz, CDCl3) δ 4.21 (t, 2H), 3.96 (q, 2H), 3.69 (t, 2H), 3.63 (q, 2H), 3.57 (q, 2H), 3.44 (t, 2H), 2.32-2.26 (m, 4H), 1.61-1.54 (m, 7H), 1.35-1.25 (m, 22H), 0.89-0.85 (m, 9H).(2) Diester B

[0091] Into a reaction vessel were charged 120 g of sebacic acid, 144 g of 2-hexyl-1-decanol, 113 g of diethylene glycol monohexyl ether, 2.3 g of p-toluenesulfonic acid monohydrate, and 415 mL of toluene. Except for these changes, the same procedure as in Example 1 was followed to yield 333 g of a yellow ester mixture (diester B) with the following NMR fingerprint.

[0092] 1H NMR (500 MHz, CDCl3) δ 4.23 (t, 2H), 3.96 (t, 2H), 3.70 (t, 2H), 3.64 (t, 2H), 3.58 (t, 2H), 3.45 (t, 2H), 2.35-2.27 (m, 4H), 1.62-1.56 (m, 8H), 1.34-1.26 (m, 37H), 0.91-0.85 (m, 9H).(3) Diester C

[0093] Into a reaction vessel were charged 201.0 g of dodecanedioic acid, 211.6 g of 2-hexyl-1-decanol, 166.1 g of diethylene glycol monohexyl ether, 3.3 g of p-toluenesulfonic acid monohydrate, and 634 mL of toluene. Except for these changes, the same procedure as in Example 1 was followed to yield 540 g of a yellow ester mixture (diester C).

[0094] 1H NMR (500 MHz, CDCl3) δ 4.23 (t, 2H), 3.96 (t, 2H), 3.70 (t, 2H), 3.64 (t, 2H), 3.58 (t, 2H), 3.45 (t, 2H), 2.33-2.27 (m, 4H), 1.62-1.56 (m, 9H), 1.32-1.26 (m, 42H), 0.89-0.86 (m, 9H).(4) Diester D

[0095] Into a reaction vessel were charged 175.0 g of sebacic acid, 258.3 g of 2-octyl-1-dodecanol, 164.6 g of diethylene glycol monohexyl ether, 3.3 g of p-toluenesulfonic acid monohydrate, and 660 mL of toluene. Except for these changes, the same procedure as in Example 1 was followed to yield 560 g of a yellow ester mixture (diester D).

[0096] 1H NMR (500 MHz, CDCl3) δ 4.23 (t, 2H), 3.96 (t, 2H), 3.70 (t, 2H), 3.64 (t, 2H), 3.58 (t, 2H), 3.45 (t, 2H), 2.33-2.27 (m, 4H), 1.62-1.56 (m, 9H), 1.32-1.26 (m, 44H), 0.89-0.86 (m, 9H).(5) Diester E

[0097] Into a reaction vessel were charged 203.4 g of dodecanedioic acid, 263.7 g of 2-octyl-1-dodecanol, 168.1 g of diethylene glycol monohexyl ether, 3.4 g of p-toluenesulfonic acid monohydrate, and 700 mL of toluene. Except for these changes, the same procedure as in Example 1 was followed to yield 573 g of a yellow ester mixture (diester E).

[0098] 1H NMR (500 MHz, CDCl3) δ 4.22 (t, 2H), 3.95 (d, 2H), 3.69 (t, 2H), 3.65-3.63 (m, 2H), 3.58-3.56 (m, 2H), 3.44 (t, 2H), 2.33-2.27 (m, 4H), 1.62-1.54 (m, 7H), 1.35-1.25 (m, 50H), 0.88-0.86 (m, 9H).(6) Monoester A

[0099] Into a reaction vessel were charged 318.0 g of 2-ethylhexanoic acid, 450.2 g of 1-tetradecanol, 4.0 g of p-toluenesulfonic acid monohydrate, and 880 mL of toluene. Except for these changes, the same procedure as in Example 1 was followed to yield 715 g of a yellow ester compound (monoester A).

[0100] 1H NMR (500 MHz, CDCl3) δ 4.06 (t, 2H), 2.27-2.21 (m, 1H), 1.65-1.55 (m, 4H), 1.54-1.40 (m, 2H), 1.35-1.25 (m, 26H), 0.89-0.86 (m, 9H)(7) Monoester B

[0101] Into a reaction vessel were charged 137.6 g of 2-hexyldecanoic acid, 116.4 g of 1-tetradecanol, 3.1 g of p-toluenesulfonic acid monohydrate, and 380 mL of toluene. Except for these changes, the same procedure as in Example 1 was followed to yield 245 g of a yellow ester compound (monoester B).

[0102] 1H NMR (500 MHz, CDCl3) δ 4.06 (t, 2H), 2.33-2.28 (m, 1H), 1.64-1.56 (m, 4H), 1.45-1.26 (m, 44H), 0.89-0.86 (m, 9H)(8) Polyol Ester A

[0103] Priolube 2720 from Cargill was prepared as polyol ester A.

[0104] The compositions of the aforementioned ester mixtures / compounds are specified in Table 2 below, and the structural formulas of sample esters listed in Table 2 are presented in Tables 3 to 8 below.TABLE 2EsterSampleComposition (mol %)Diester ADA-125DA-225DA-350Diester BDB-125DB-225DB-350Diester CDC-125DC-225DC-350Diester DDD-125DD-225DD-350Diester EDE-125DE-225DE-350Monoester AMA-1100Monoester BMB-1100Polyol ester APA-1100TABLE 3SampleStructural formulaDA-1DA-2DA-3TABLE 4SampleStructural formulaDB-1DB-2DB-3TABLE 5SampleStructural formulaDC-1DC-2DC-3TABLE 6SampleStructural formulaDD-1DD-2DD-3TABLE 7SampleStructural formulaDE-1DE-2DE-3TABLE 8SampleStructural formulaMA-1MB-1PA-1R = C8-based hydrocarbyl group2. Confirmation of the Physical Properties of the Ester Mixture and of the Lubricant Composition(i) Confirmation of the Physical Properties of the Ester MixtureThe physical properties of Examples 1 to 6 and Comparative Examples 1 to 6 were measured as described below. The compositions of the Examples and Comparative Examples and the measurement results are shown in Table 9 and 10.The traction coefficient measurement was carried out using a Mini Traction Machine (MTM) from PCS Instruments Ltd. The traction coefficient values were measured with a slide-to-roll ratio (SRR) varied from 0% to 100% under conditions: a load of 38 N, a temperature of 100° C., and a speed of 1,000 mm / s. Then, the traction coefficient values at the SRR of 100% were specified.The kinematic viscosity measurement was carried out using Kinematic Viscometer from CANNON, and evaluated according to ASTM D445 test method.The viscosity index calculation was carried out based on ASTM D 2270 test method using the kinematic viscosities measured at 40° C. and 100° C. measured with Kinematic Viscometer from CANNON.The pour point measurement was carried out using Automatic Pour / Cloud Point Tester from TANAKA, and evaluated according to ASTM D 6749 test method.(2) Confirmation of the Miscibility of the Lubricant CompositionFor each of the Examples and Comparative Examples, an equal amount of additives (additive PKG: HiTEC 3491K, from Afton) was added and mixed by stirring under heat for 1 hour to prepare a lubricant composition, after which miscibility was evaluated. The evaluation involved storing the lubricant composition at room temperature (25° C.) and low temperature (0° C.) for 8 weeks, followed by visual inspection for layer separation or coagulation. A case showing no layer separation and no coagulation was represented by “Pass”. The results are shown in Table 9 and 10.TABLE 9Composition (wt %)ExampleEster base oilAdditivesExample 1DiesterMonoesterAdditiveA (40%)A (50%)PKG (10%)Example 2DiesterMonoesterAdditiveB (50%)A (40%)PKG (10%)Example 3DiesterMonoesterAdditiveB (60%)B (30%)PKG (10%)Example 4DiesterMonoesterAdditiveC (50%)A (40%)PKG (10%)Example 5DiesterMonoesterAdditiveD (50%)A (40%)PKG (10%)Example 6DiesterMonoesterAdditiveE (50%)A (40%)PKG (10%)ComparativeMonoester—AdditiveExample 1A (90%)PKG (10%)ComparativeMonoester—AdditiveExample 2B (90%)PKG (10%)ComparativeDiester—AdditiveExample 3A (90%)PKG (10%)ComparativeDiester—AdditiveExample 4B (90%)(PKG 10%)ComparativeDiester—AdditiveExample 5C (90%)PKG (10%)ComparativePolyol ester—AdditiveExample 6A (90%)PKG (10%)TABLE 10100° C.PourMiscibilityViscosityKinematicPointTractionwithExampleIndexViscosity(° C.)Coefficientadditives*Example 11562.70−300.0157PassExample 21693.30−330.0159PassExample 31734.65−390.0179PassExample 41733.81−330.0180PassExample 51763.84−300.0175PassExample 61803.98−240.0178PassComparative1382.18−120.0201PassExample 1Comparative1433.50−240.0189PassExample 2Comparative1753.90−240.0170FailExample 3(Haze)Comparative1875.40−390.0167FailExample 4(Haze)Comparative1896.11−450.0165FailExample 5(Haze)Comparative1364.46−570.0238FailExample 6(Haze)*Except for “miscibility with additives,” all other properties were evaluated in pure ester base oil state without any additives added.An arbitrary combination of multiple esters to enhance the properties of ester base oil is likely to be accompanied by adverse effects, such as deterioration of the properties of the base oil or reduced miscibility with additives. Referring to Table 9 above, it can be seen that the ester mixture including the diester and monoester of the present disclosure achieves excellent kinematic viscosity, pour point, traction coefficient, and viscosity index, while also exhibiting superior miscibility with additives. Namely, the embodiments of the present disclosure provide an ester base oil having improved properties without any deterioration in miscibility with additives.A lubricant product including the ester mixture of the present disclosure is expected to be applicable as a replacement for conventional lubricant products and is also anticipated to be applicable to electric vehicles to contribute to improving the energy efficiency of the vehicles.

[0113] The foregoing embodiments illustrate applying the principles of the present disclosure, and other embodiments may be further included without departing from the scope of the present disclosure. Furthermore, the embodiments may be combined to form additional embodiments.

Claims

1. An ester mixture comprising a diester and a monoester,wherein the diester comprises:a first ester having the chemical structure represented by (A-C-A); ora second ester having the chemical structure represented by (B—C—B); ora third ester having the chemical structure represented by (A-C—B); orany combination thereof,wherein A is derived from a first alcohol containing at least one alkoxy group,B is derived from a second alcohol, which is a hydrocarbyl alcohol, andC is derived from a dicarboxylic acid.

2. The ester mixture of claim 1, wherein the first alcohol is represented by Formula 1,wherein R1 is an alkylene group, an alkenylene group, or an alkynylene group,n is an integer equal to or greater than 1, andR2 is an alkyl group, an alkenyl group, or an alkynyl group.

3. The ester mixture of claim 2, wherein the R1 is a C1-C30 alkylene group,the n is an integer from 1 to 20, andthe R2 is a C1-C30 alkyl group, a C2-C30 alkenyl group, or a C2-C30 alkynyl group.

4. The ester mixture of claim 2, wherein the R1 is a C1-C8 alkylene group,the n is an integer from 1 to 5, andthe R2 is a C1-C12 alkyl group, a C2-C12 alkenyl group, or a C2-C12 alkynyl group.

5. The ester mixture of claim 1, wherein the second alcohol is represented by Formula 2,wherein R3 is a hydrocarbyl group.

6. The ester mixture of claim 5, wherein the R3 is a C1-C30 alkyl group, a C2-C30 alkenyl group, or a C2-C30 alkynyl group.

7. The ester mixture of claim 5, wherein the R3 is a C1-C24 alkyl group, a C2-C24 alkenyl group, or a C2-C24 alkynyl group.

8. The ester mixture of claim 1, wherein the dicarboxylic acid is oxalic acid or is represented by Formula 3,wherein, R4 is an alkylene group, an alkenylene group, or an alkynylene group.

9. The ester mixture of claim 8, wherein the R4 is a C1-C30 alkylene group.

10. The ester mixture of claim 8, wherein the R4 is a C1-C12 alkylene group.

11. The ester mixture of claim 1, wherein the monoester is a fourth ester having the chemical structure represented by (D-E), wherein D is derived from a monocarboxylic acid and E is derived from a hydrocarbyl alcohol.

12. The ester mixture of claim 11, wherein the monocarboxylic acid is represented by Formula 4,wherein R5 is a substituted or unsubstituted hydrocarbyl group.

13. The ester mixture of claim 12, wherein the R5 is a C1-C30 alkyl group, a C2-C30 alkenyl group, or a C2-C30 alkynyl group.

14. The ester mixture of claim 12, wherein the R5 is a C1-C24 alkyl group, a C2-C24 alkenyl group, or a C2-C24 alkynyl group.

15. The ester mixture of claim 11, wherein the hydrocarbyl alcohol is represented by Formula 5,wherein R6 is a substituted or unsubstituted hydrocarbyl group.

16. The ester mixture of claim 1, wherein the diester comprises: a first ester; a second ester; anda third ester.

17. The ester mixture of claim 1, wherein the diester comprises:10 to 40 mol % of a first ester;10 to 40 mol % of a second ester; and30 to 70 mol % of a third ester.

18. The ester mixture of claim 1, wherein a weight ratio of the diester to the monoester in the mixture is 1:8 to 8:1.

19. The ester mixture of claim 1, wherein the ester mixture exhibits at least one of the following characteristics:a traction coefficient equal to or less than 0.04, measured under conditions: a load of 38 N, a temperature of 100° C., a speed of 1,000 mm / s, and a slide-to-roll ratio (SRR) of 100%;a flash point of equal to or greater than 200° C.;a kinematic viscosity at 100° C. of 2 to 10 cSt;a viscosity index of equal to or greater than 90; anda pour point of less than 0° C.

20. A lubricating base oil comprising the ester mixture of claim 1.

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