Small molecule carboxyl-terminated gelling agents and their preparation methods and applications

Abstract

This invention provides a small-molecule carboxyl-terminated gelling agent and a gel lubricant, along with their preparation method and applications, relating to the field of lubrication materials technology. The small-molecule carboxyl-terminated gelling agent provided by this invention has the structure shown in Formula I, where R is an alkyl group with 14-18 carbon atoms; X is hydrogen, methyl, isopropyl, isobutyl, or benzyl; and n is 2 or 3. The small-molecule carboxyl-terminated gelling agent provided by this invention exhibits uniform stability in various base oils and a very low gel concentration. It can self-assemble through multiple hydrogen bonds and other interactions to effectively bind the base oil, thus avoiding environmental pollution problems caused by base oil creep and leakage. Furthermore, this gelling agent has strong versatility, exhibiting excellent friction-reducing and anti-wear properties and superior thermal stability in different types of base oils. Moreover, thanks to the strong polarity and interfacial adsorption of the terminal carboxyl group, as well as the biocompatibility of natural amino acid derivatives, it becomes a green gelling agent. The gel lubricant formed by the small-molecule carboxyl-terminated gelling factor and base oil has advantages such as being green and environmentally friendly, economically efficient, and having excellent tribological properties, and has a bright application prospect in the field of lubrication of bearings or metal friction pairs.

Description

Technical Field

[0001] This invention relates to the field of lubricating materials technology, and in particular to small molecule end-carboxyl type gelling agents and gel lubricants, their preparation methods and applications. Background Technology

[0002] Various forms of friction and wear not only consume more than 20% of the world's energy, but also cause damage to many devices. Reducing or even eliminating friction and wear has become a top priority in many scientific and technological fields today. The use of lubricants is considered one of the most effective ways to reduce mechanical friction and wear and extend the service life of equipment (1. Li, R.; Yang, X.; Zhao, J.; Yue, C.; Wang, Y.; Li, J.; Meyer, E.; Zhang, J.; Shi, Y., Advanced Functional Materials 2022, 32(18), 2111365. 2. Holmberg, K.; Erdemir, A., Friction 2017, 5(3), 263-284. 3. Tabor, D., Nature 1957, 180(4600), 1448-1451.). However, traditional lubricants cause many serious environmental problems during use due to leakage, evaporation and creep of lubricating oil, which has quickly attracted people's attention. Therefore, developing high-performance, environmentally friendly green lubricants is of paramount importance. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide a small-molecule carboxyl-terminated gelling agent and a gel lubricant, as well as their preparation method and application. The small-molecule carboxyl-terminated gelling agent provided by this invention can form a gel lubricant with base oil, effectively binding the base oil to prevent creep and leakage problems. Furthermore, it exhibits excellent friction-reducing and anti-wear properties in different types of base oils, and is environmentally friendly.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a small-molecule carboxyl-terminated gelling factor having the structure shown in Formula I:

[0006]

[0007] In Formula I, R is an alkyl group with 14 to 18 carbon atoms; X is hydrogen, methyl, isopropyl, isobutyl or benzyl, and n is 2 or 3.

[0008] This invention provides a method for preparing the small molecule terminal carboxyl-terminated gel factor described in the above technical solution, comprising the following steps:

[0009] An esterification reaction is carried out by mixing an alkyl alcohol, an amino acid, p-toluenesulfonic acid, and an organic solvent to obtain an amino acid alkyl alcohol ester; wherein the alkyl alcohol is an alkyl monohydric alcohol with 14 to 18 carbon atoms, and the amino acid is glycine, alanine, valine, leucine, or phenylalanine.

[0010] The amino acid alkyl alcohol ester is mixed with an acid anhydride and an organic solvent to undergo an amidation reaction to obtain the small molecule terminal carboxyl-type gel factor; the acid anhydride is succinic anhydride or glutaric anhydride.

[0011] Preferably, the molar ratio of p-toluenesulfonic acid, alkyl alcohol and amino acid is 1.2:1.0:(1.0~1.2).

[0012] Preferably, the esterification reaction is a reflux reaction, and the esterification reaction time is 8-10 hours.

[0013] Preferably, the molar ratio of the acid anhydride to the amino acid alkyl alcohol ester is (1.2-1.5):1.0.

[0014] Preferably, the amidation reaction is a reflux reaction, and the amidation reaction time is 5-8 hours.

[0015] This invention provides a gel lubricant comprising the following components by mass percentage: 1-10% gelling agent and 90-99% base oil, wherein the gelling agent is the small molecule carboxyl-terminated gelling agent described in the above technical solution or the small molecule carboxyl-terminated gelling agent prepared by the preparation method described in the above technical solution.

[0016] Preferably, the base oil includes one or more of Group IV base oils, Group I base oils, and Group II base oils.

[0017] This invention provides a method for preparing the gel lubricant described in the above technical solution, comprising the following steps:

[0018] The gelling agent is added to the base oil and heated to 80-120°C. After cooling, the gel lubricant is obtained.

[0019] This invention provides the application of the gel lubricant described in the above technical solutions or the gel lubricant prepared by the above technical solutions in the field of bearing or metal friction pair lubrication.

[0020] This invention provides a small-molecule terminal carboxyl-terminated gelling agent with the structure shown in Formula I, where R is an alkyl group with 14-18 carbon atoms; X is hydrogen, methyl, isopropyl, isobutyl, or benzyl; and n is 2 or 3. The small-molecule terminal carboxyl-terminated gelling agent provided by this invention exhibits uniform stability in various base oils with a very low gel concentration. It also possesses a certain degree of thermal reversibility and can self-assemble through multiple hydrogen bonds and other interactions to effectively bind the base oil (forming a supramolecular gel), thereby preventing problems such as base oil creep and leakage, and thus mitigating environmental pollution. Furthermore, this gelling agent with different alkyl chain lengths has strong universality, exhibiting excellent friction-reducing and anti-wear properties and superior thermal stability in various types of base oils. Moreover, thanks to the strong polarity and interfacial adsorption of the terminal carboxyl group, as well as the biocompatibility of natural amino acid derivatives, it becomes a strong candidate for a green lubricant. Therefore, compared with existing lubricants, the gel lubricant formed by the small molecule end-carboxyl type gel factor and base oil provided by this invention has advantages such as being green and environmentally friendly, economically efficient, and having excellent tribological properties. It has a bright application prospect in the field of lubrication of bearings or metal friction pairs. As a new type of green lubricant, it can play a good protective role for mechanical parts. Attached Figure Description

[0021] Figure 1 The gelling factor TCAG-nd-2 (n = 14, 16, or 18) prepared in Examples 1-3 1 H-NMR spectrum. Detailed Implementation

[0022] This invention provides a small-molecule carboxyl-terminated gelling factor having the structure shown in Formula I:

[0023]

[0024] In Formula I, R is an alkyl group with 14 to 18 carbon atoms; X is hydrogen, methyl, isopropyl, isobutyl or benzyl, and n is 2 or 3.

[0025] In this invention, R is preferably a straight-chain alkyl group having 14, 16, or 18 carbon atoms.

[0026] The carboxyl-terminated gelling agent provided by this invention is an environmentally friendly gelling agent based on natural amino acids, containing only four elements: C, H, O, and N. This makes it more environmentally competitive than traditional lubricants containing phosphorus, halogens, and sulfur. Simultaneously, lubricants containing carboxyl groups exhibit excellent lubrication performance and strong boundary adsorption film-forming ability for various metal friction pairs (e.g., steel / steel, steel / Cu, and steel / Al). Furthermore, this carboxyl-terminated gelling agent shows promise as an oil-soluble rust and corrosion inhibitor. This is because the polar terminal carboxyl groups can be tightly adsorbed onto the metal surface through charge interaction, while the non-polar long-chain hydrocarbon groups face outwards from the metal surface and are miscible with oils. This allows the rust inhibitor molecules to oriented onto the metal surface, forming an adsorbent protective film that protects the metal from water and oxygen corrosion. In addition, the presence of carboxyl and amide bonds promotes hydrogen bond formation, facilitating supramolecular self-assembly to form a three-dimensional network that effectively binds the base oil. These characteristics make the carboxyl-terminated gelling agent a strong candidate for high-performance green lubricants, capable of replacing traditional lubricants under certain special operating conditions.

[0027] This invention provides a method for preparing the small molecule terminal carboxyl-terminated gel factor described in the above technical solution, comprising the following steps:

[0028] An esterification reaction is carried out by mixing an alkyl alcohol, an amino acid, p-toluenesulfonic acid, and an organic solvent to obtain an amino acid alkyl alcohol ester; wherein the alkyl alcohol is an alkyl monohydric alcohol with 14 to 18 carbon atoms, and the amino acid is glycine, alanine, valine, leucine, or phenylalanine.

[0029] The amino acid alkyl alcohol ester is mixed with an acid anhydride and an organic solvent to undergo an amidation reaction to obtain the small molecule terminal carboxyl-type gel factor; the acid anhydride is succinic anhydride or glutaric anhydride.

[0030] Unless otherwise specified, all raw materials involved in this invention are commercially available products well known in the art.

[0031] The reaction formula involved in the preparation of the small molecule terminal carboxyl-type gel factor of the present invention is shown in formula a, and will be described in detail below.

[0032]

[0033] In this invention, an esterification reaction is carried out by mixing an alkyl alcohol (compound 1), an amino acid (compound 2), p-toluenesulfonic acid (p-TSA), and an organic solvent (denoted as the first organic solvent) to obtain an amino acid alkyl alcohol ester (compound 3).

[0034] In this invention, the alkyl alcohol is an alkyl monohydric alcohol with 14 to 18 carbon atoms, preferably tetradecyl alcohol, hexadecyl alcohol, or octadecyl alcohol; the amino acid is glycine, alanine, valine, leucine, or phenylalanine, with leucine preferably L-leucine. In this invention, the p-toluenesulfonic acid is preferably p-toluenesulfonic acid monohydrate. As a catalyst for esterification, p-toluenesulfonic acid, compared to catalysts such as sulfuric acid, can avoid coking and other side reactions caused by sulfuric acid. In this invention, the first organic solvent is preferably toluene, tetrahydrofuran, or dichloromethane.

[0035] In this invention, the preferred molar ratio of p-toluenesulfonic acid, alkyl alcohol, and amino acid is 1.2:1.0:(1.0~1.2); this invention does not have any special requirements on the amount of the first organic solvent, as long as it can ensure the dissolution of the raw materials and the smooth progress of the reaction.

[0036] In this invention, the esterification reaction is preferably a reflux reaction, and the esterification reaction time is preferably 8 to 10 hours. In the embodiments of this invention, the esterification reaction is specifically carried out in a Dean-Stark apparatus under stirring conditions.

[0037] After the esterification reaction is completed, the present invention preferably performs post-treatment on the obtained esterification reaction solution, and the preferred method for post-treatment is as follows:

[0038] The solvent in the esterification reaction solution was evaporated under reduced pressure to obtain an oily substance.

[0039] The oily substance was dissolved in a second organic solvent, and the pH of the solution was adjusted to neutral with a saturated sodium bicarbonate solution. The organic phase was then collected.

[0040] The organic phase was dried overnight with anhydrous magnesium sulfate and then separated. The solvent was evaporated off the separated organic phase again, and the residue was dissolved in a concentrated hydrochloric acid-acetone solution and frozen to obtain a white amino acid alkyl alcohol ester hydrochloride.

[0041] The amino acid alkyl alcohol ester hydrochloride was dissolved in a third organic solvent, and the pH of the solution was adjusted to neutral with saturated sodium bicarbonate solution. The organic phase was collected and dried overnight with anhydrous magnesium sulfate. The solvent was then evaporated under reduced pressure to obtain the amino acid alkyl alcohol ester.

[0042] In this invention, the second organic solvent is preferably chloroform, tetrahydrofuran, or dichloromethane; the volume ratio of concentrated hydrochloric acid to acetone in the concentrated hydrochloric acid-acetone solution is preferably 1:20, and the concentrated hydrochloric acid is preferably hydrochloric acid with a mass fraction of 36-38%; the third organic solvent is preferably chloroform. In this invention, the freezing temperature is preferably 0-4°C.

[0043] After obtaining the amino acid alkyl alcohol ester, the present invention mixes the amino acid alkyl alcohol ester with an acid anhydride and an organic solvent (denoted as the fourth organic solvent) to carry out an amidation reaction to obtain the small molecule terminal carboxyl type gel factor.

[0044] In this invention, the acid anhydride is succinic anhydride or glutaric anhydride; the molar ratio of the acid anhydride to the amino acid alkyl alcohol ester is preferably (1.2-1.5):1.0. In this invention, the fourth organic solvent is preferably tetrahydrofuran. This invention does not have specific requirements on the amount of the fourth organic solvent used, as long as the amino acid alkyl alcohol ester is fully dissolved.

[0045] In this invention, the amino acid alkyl alcohol ester is preferably dissolved in a fourth organic solvent, and then an acid anhydride is added thereto.

[0046] In this invention, the amidation reaction is preferably a reflux reaction, the reflux reaction temperature is preferably 60°C, and the amidation reaction time is preferably 5 to 8 hours.

[0047] After the amidation reaction is completed, the present invention preferably performs post-treatment on the obtained amidation reaction solution, and the preferred method for post-treatment is as follows:

[0048] The solvent of the amidation reaction solution was evaporated under reduced pressure, and the residual acid anhydride was removed with saturated sodium bicarbonate solution. Then, the pH of the resulting solution was adjusted to 1 with hydrochloric acid to precipitate the solid.

[0049] The obtained solid was recrystallized in hexane and then dried under vacuum to obtain the small molecule terminal carboxyl type gel factor.

[0050] In this invention, the concentration of the hydrochloric acid is preferably 1 mol / L. In this invention, the recrystallization temperature is preferably 60°C; the vacuum drying temperature is preferably 45–50°C, and the time is preferably 12–24 h.

[0051] This invention provides a gel lubricant comprising the following components by mass percentage: 1-10% gelling agent and 90-99% base oil, wherein the gelling agent is the small molecule carboxyl-terminated gelling agent described in the above technical solution or the small molecule carboxyl-terminated gelling agent prepared by the preparation method described in the above technical solution.

[0052] In this invention, the mass percentage of the gelling factor in the gel lubricant is preferably 2-7%, more preferably 4-5%, and the mass percentage of the base oil in the gel lubricant is correspondingly preferably 93-98%, more preferably 95-96%.

[0053] In this invention, the base oil preferably includes one or more of Group IV base oils (i.e., polyalphaolefins), Group I base oils, and Group II base oils. Specifically, the Group IV base oil hydrocarbon is preferably one or more of PAO4, PAO10, and PAO40; the Group I base oil is preferably MVI300; and the Group II base oil is preferably Formosa Plastics 500N. PAO4, PAO10, and PAO40 represent base oils of the same series but different viscosities, while PAO10, Formosa Plastics 500N, and MVI300 represent base oils of different series but similar viscosities. In this invention, the gelling agent exhibits strong universality, is uniformly stable in various base oils with a very low gel concentration, and demonstrates excellent friction-reducing and anti-wear properties in all types of base oils.

[0054] The gel lubricant provided by this invention has high thermal stability and a stable and complete structure at room temperature. This gel lubricant not only exhibits excellent friction reduction and anti-wear properties, but also effectively binds the base oil through multiple hydrogen bonds and other interactions, thereby improving the environmental pollution problems caused by base oil creep and leakage. Furthermore, thanks to the presence of natural amino acids and terminal carboxylic acid groups, it becomes a green lubricant.

[0055] This invention provides a method for preparing the gel lubricant described in the above technical solution, comprising the following steps:

[0056] The gelling agent is added to the base oil and heated to 80-120°C. After cooling, the gel lubricant is obtained.

[0057] In this invention, the heating temperature is preferably 90-100°C, and the cooling is preferably natural cooling to room temperature.

[0058] This invention provides the application of the gel lubricant described in the above technical solutions or the gel lubricant prepared by the above preparation methods in the field of bearing or metal friction pair lubrication. In this invention, the metal friction pair is preferably a steel / steel friction pair, a steel / Cu friction pair, or a steel / Al friction pair. This invention does not impose any special requirements on the application method; any application method well known to those skilled in the art can be used.

[0059] To further illustrate the present invention, the small molecule terminal carboxyl-type gelling factor and gel lubricant, their preparation methods and applications provided by the present invention are described in detail below with reference to examples, but these should not be construed as limiting the scope of protection of the present invention.

[0060] Example 1

[0061] The preparation process of L-leucine small molecule carboxyl-terminated gelling factor (denoted as TCAG-14-d-2) is as follows:

[0062] (1) Toluenesulfonic acid monohydrate (0.12 mol), tetradecanol (0.1 mol), and L-leucine (0.1 mol) were dissolved in 150 mL of toluene and stirred under reflux in a Dean-Stark apparatus for 10 h. After the reaction was complete, the solvent was evaporated under reduced pressure, and the resulting oily substance was dissolved in 100 mL of chloroform. The pH was adjusted to neutral with saturated sodium bicarbonate solution, and the organic phase was collected and dried overnight with anhydrous magnesium sulfate. After separating the organic phase, the solvent was evaporated again, and the residue was dissolved in 200 mL of acetone containing 10 mL of concentrated hydrochloric acid and frozen at 4 °C to obtain the corresponding white amino acid alkyl alcohol ester hydrochloride. Subsequently, it was dissolved in 100 mL of chloroform, and the pH was adjusted to neutral with saturated sodium bicarbonate solution. The organic phase was collected and dried overnight with anhydrous magnesium sulfate, and the solvent was evaporated under reduced pressure to obtain the amino acid alkyl alcohol ester.

[0063] (2) The obtained amino acid alkyl alcohol ester (0.03 mol) was dissolved in 100 mL of tetrahydrofuran, and then succinic anhydride (0.045 mol) was added to it. The mixture was refluxed at 60 °C for 8 h. After the reaction was completed, the solvent was evaporated under reduced pressure, the residual anhydride was removed with saturated sodium bicarbonate solution, and the pH was adjusted with 1 M hydrochloric acid to precipitate the solid (pH value was 1). The obtained solid was recrystallized in 50 mL of n-hexane at 60 °C and dried under vacuum at 45 °C for 24 h to obtain the final product TCAG-14-d-2.

[0064] The structural formula of L-leucine small molecule terminal carboxyl-terminated gelling factor (TCAG-14-d-2) is as follows:

[0065]

[0066] Example 2

[0067] The preparation process of L-leucine small molecule carboxyl-terminated gelling factor (denoted as TCAG-16-d-2) is as follows:

[0068] (1) Toluenesulfonic acid monohydrate (0.12 mol), hexadecyl alcohol (0.1 mol), and L-leucine (0.1 mol) were dissolved in 150 mL of toluene and stirred under reflux for 10 h in a Dean-Stark apparatus. After the reaction was complete, the solvent was distilled off under reduced pressure, and the resulting oily substance was dissolved in 100 mL of chloroform. The pH was adjusted to neutral with saturated sodium bicarbonate solution, and the organic phase was collected and dried overnight with anhydrous magnesium sulfate. After separating the organic phase, the solvent was distilled off again, and the residue was dissolved in 200 mL of acetone containing 10 mL of concentrated hydrochloric acid and frozen at 4 °C to obtain the corresponding white amino acid alkyl alcohol ester hydrochloride. Subsequently, it was dissolved in 100 mL of chloroform, and the pH was adjusted to neutral with saturated sodium bicarbonate solution. The organic phase was collected and dried overnight with anhydrous magnesium sulfate, and the solvent was distilled off under reduced pressure to obtain the amino acid alkyl alcohol ester.

[0069] (2) The obtained amino acid alkyl alcohol ester (0.03 mol) was dissolved in 100 mL of tetrahydrofuran, and then succinic anhydride (0.045 mol) was added to it. The mixture was refluxed at 60 °C for 8 h. After the reaction was completed, the solvent was evaporated under reduced pressure, the residual anhydride was removed with saturated sodium bicarbonate solution, and the pH was adjusted with 1 M hydrochloric acid to precipitate the solid (pH value was 1). The obtained solid was recrystallized in 50 mL of n-hexane at 60 °C and dried under vacuum at 45 °C for 24 h to obtain the final product TCAG-16-d-2.

[0070] The structural formula of L-leucine small molecule carboxyl-terminated gelling factor (TCAG-16-d-2) is as follows:

[0071]

[0072] Example 3

[0073] The preparation process of L-leucine small molecule carboxyl-terminated gelling factor (denoted as TCAG-18-d-2) is as follows:

[0074] (1) Toluenesulfonic acid monohydrate (0.12 mol), octadecyl alcohol (0.1 mol), and L-leucine (0.1 mol) were dissolved in 150 mL of toluene and stirred under reflux for 10 h in a Dean-Stark apparatus. After the reaction was complete, the solvent was distilled off under reduced pressure, and the resulting oily substance was dissolved in 100 mL of chloroform. The pH was adjusted to neutral with saturated sodium bicarbonate solution, and the organic phase was collected and dried overnight with anhydrous magnesium sulfate. After separating the organic phase, the solvent was distilled off again, and the residue was dissolved in 200 mL of acetone containing 10 mL of concentrated hydrochloric acid and frozen at 4 °C to obtain the corresponding white amino acid alkyl alcohol ester hydrochloride. Subsequently, it was dissolved in 100 mL of chloroform, and the pH was adjusted to neutral with saturated sodium bicarbonate solution. The organic phase was collected and dried overnight with anhydrous magnesium sulfate, and the solvent was distilled off under reduced pressure to obtain the amino acid alkyl alcohol ester.

[0075] (2) The obtained amino acid alkyl alcohol ester (0.03 mol) was dissolved in 100 mL of tetrahydrofuran, and then succinic anhydride (0.045 mol) was added to it. The mixture was refluxed at 60 °C for 8 h. After the reaction was completed, the solvent was evaporated under reduced pressure, the residual anhydride was removed with saturated sodium bicarbonate solution, and the pH was adjusted with 1 M hydrochloric acid to precipitate the solid (pH value was 1). The obtained solid was recrystallized in 50 mL of n-hexane at 60 °C and dried under vacuum at 45 °C for 24 h to obtain the final product TCAG-18-d-2.

[0076] The structural formula of L-leucine small molecule carboxyl-terminated gelling factor (TCAG-18-d-2) is as follows:

[0077]

[0078] Figure 1The gelling factor TCAG-nd-2 (n = 14, 16, or 18) prepared in Examples 1-3 1 H-NMR spectrum (solvent: DMSO-d6) and the corresponding H peak positions are marked.

[0079] Example 4

[0080] The preparation process of the gel lubricant (denoted as 14@PAO10) is as follows:

[0081] In a 20 mL glass vial, 50 mg of TCAG-14-d-2 was added to 1.200 g of PAO10 and heated to 90 °C to completely dissolve the gelling agent. The solution was then allowed to cool naturally to room temperature to obtain 4 wt% of 14@PAO10 gel lubricant.

[0082] Example 5

[0083] The preparation process of the gel lubricant (denoted as 16@PAO10) is as follows:

[0084] In a 20 mL glass vial, 50 mg of TCAG-16-d-2 was added to 1.200 g of PAO10 and heated to 90 °C to completely dissolve the gelling agent. The solution was then allowed to cool naturally to room temperature to obtain 4 wt% of 16@PAO10 gel lubricant.

[0085] Example 6

[0086] The preparation process of the gel lubricant (denoted as 18@PAO10) is as follows:

[0087] In a 20 mL glass vial, 50 mg of TCAG-18-d-2 was added to 1.200 g of PAO10 and heated to 90 °C to completely dissolve the gelling agent. The solution was then allowed to cool naturally to room temperature to obtain 4 wt% of 18@PAO10 gel lubricant.

[0088] Example 7

[0089] The preparation process of the gel lubricant (denoted as 18@PAO4) is as follows:

[0090] In a 20 mL glass vial, 50 mg of TCAG-18-d-2 was added to 1.200 g of PAO4 and heated to 90 °C to completely dissolve the gelling agent. The solution was then allowed to cool naturally to room temperature to obtain the corresponding 4 wt% 18@PAO4 gel lubricant.

[0091] Example 8

[0092] The preparation process of the gel lubricant (denoted as 18@PAO40) is as follows:

[0093] In a 20 mL glass vial, 50 mg of TCAG-18-d-2 was added to 1.200 g of PAO40 and heated to 90 °C to completely dissolve the gelling agent. The solution was then allowed to cool naturally to room temperature to obtain 4 wt% of 18@PAO40 gel lubricant.

[0094] Example 9

[0095] The preparation process of the gel lubricant (denoted as 18@MVI300) is as follows:

[0096] In a 20 mL glass vial, 50 mg of TCAG-18-d-2 was added to 1.200 g of MVI300 and heated to 90 °C to completely dissolve the gelling agent. The solution was then allowed to cool naturally to room temperature to obtain 4 wt% of 18@MVI300 gel lubricant.

[0097] Example 10

[0098] The preparation process of the gel lubricant (denoted as 18@Formosa Plastics 500N) is as follows:

[0099] In a 20 mL glass vial, 50 mg of TCAG-18-d-2 was added to 1.200 g of Formosa Plastics 500N and heated to 90 °C to completely dissolve the gelling agent. The solution was then allowed to cool naturally to room temperature to obtain 4 wt% of 18@Formosa Plastics 500N gel lubricant.

[0100] Example 11

[0101] To demonstrate that the prepared gelling agent can form a stable gel lubricant in different base oils, the gelling properties of the gelling agents prepared in Examples 1-3 were studied, and the results are shown in Table 1.

[0102] Table 1. Gel-forming properties of gelling agents with different molecular chains in different base oils.

[0103]

[0104] Note: In Table 1, G represents gel and PG represents partial gel. The percentages after G and PG represent the critical gel concentration, which is the minimum mass percentage of gelling agent required to form a gel. For example, G (4%) means that a gel can only be formed when the mass fraction of gelling agent reaches 4%, and PG (7%) means that a partial gel can only be formed when the mass fraction of gelling agent reaches 7%.

[0105] As can be seen from Table 1, among different types of base oils, three gelators with different molecular chains can all self-assemble to form gels (except for partial gelation of 14@PAO40), and the required minimum gelation concentration is TCAG-18-d-2 < TCAG-16-d-2 < TCAG-14-d-2 (except that in MVI300, TCAG-18-d-2 and TCAG-16-d-2 are similar). This is due to the fact that the longer the alkyl chain of the gelator, the stronger the self-assembly gelation ability.

[0106] Example 12

[0107] Taking TCAG-18-d-2 prepared in Experimental Example 3 as an example, its thermal stability and phase transition temperature after forming gel lubricants (Examples 6 - 8) in different base oils were studied in detail. The results are shown in Table 2.

[0108] Table 2 Phase Transition Temperature and Thermal Properties of PAO Series Gel Lubricants

[0109]

[0110] As can be seen from Table 2, the gels formed by TCAG-18-d-2 (4wt%) in various base oils all exhibit excellent thermal stability, and have relatively high phase transition temperatures, simultaneously reflecting that this series of gel lubricants has a stable and complete structure at room temperature.

[0111] Example 13

[0112] In order to evaluate the tribological properties of gelators with different chain lengths after gelation in different base oils (Examples 4 - 10), an SRV-IV micro-vibration type friction and wear tester produced by Optimol Oil Company of Germany was used, and a comparison was made with the blank base oil. The friction test conditions were: steel / steel friction pair, load 300N, temperature 25°C, amplitude 1mm, test time 30min, frequency 25Hz. The test results are shown in Table 3 and Table 4.

[0113] Table 3 Average Friction Coefficient and Wear Volume of Gel Lubricants after Gelation of Gelators with Different Chain Lengths (4wt%)

[0114]

[0115] Table 4 Average Friction Coefficient and Wear Volume of Different Base Oils and Gel Lubricants (4wt%)

[0116]

[0117]

[0118] As shown in Tables 3 and 4, compared with base oils, various gel lubricants exhibit lower coefficients of friction and smaller wear volumes. As shown in Table 3, at the same gel factor concentration (4 wt%), PAO10 gel lubricants all exhibited excellent and similar friction-reducing properties, while their anti-wear properties increased with increasing molecular chain length. Notably, in Table 4, TCAG-18-d-2 (4 wt%) demonstrated excellent friction-reducing and anti-wear properties in different types of base oils (PAO4, PAO10, PAO40, MVI300, and Formosa Plastics 500N).

[0119] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A small-molecule terminal carboxyl-terminated gelling factor, characterized in that, It has the structure shown in Equation I: Formula I, In Formula I, R is an alkyl group with 14 to 18 carbon atoms; X is hydrogen, methyl, isopropyl or isobutyl, and n is 2 or 3.

2. The method for preparing the small molecule terminal carboxyl-terminated gelling factor according to claim 1, characterized in that, Includes the following steps: An esterification reaction is carried out by mixing an alkyl alcohol, an amino acid, p-toluenesulfonic acid, and an organic solvent to obtain an amino acid alkyl alcohol ester; wherein the alkyl alcohol is an alkyl monohydric alcohol with 14 to 18 carbon atoms, and the amino acid is glycine, alanine, valine, or leucine. The amino acid alkyl alcohol ester is mixed with an acid anhydride and an organic solvent to undergo an amidation reaction to obtain the small molecule terminal carboxyl-type gel factor; the acid anhydride is succinic anhydride or glutaric anhydride.

3. The preparation method according to claim 2, characterized in that, The molar ratio of p-toluenesulfonic acid, alkyl alcohol and amino acid is 1.2:1.0:(1.0~1.2).

4. The preparation method according to claim 2 or 3, characterized in that, The esterification reaction is a reflux reaction, and the esterification reaction time is 8-10 hours.

5. The preparation method according to claim 2, characterized in that, The molar ratio of the acid anhydride to the amino acid alkyl alcohol ester is (1.2~1.5):1.

0.

6. The preparation method according to claim 2 or 5, characterized in that, The amidation reaction is a reflux reaction, and the amidation reaction time is 5-8 hours.

7. A gel lubricant, characterized in that, The product comprises the following components by mass percentage: gelling agent 1-10%, base oil 90-99%, wherein the gelling agent is the small molecule end-carboxyl gelling agent of claim 1 or the small molecule end-carboxyl gelling agent prepared by any one of claims 2-6.

8. The gel lubricant according to claim 7, characterized in that, The base oils include one or more of Group IV, Group I, and Group II base oils.

9. The method for preparing the gel lubricant according to claim 7 or 8, characterized in that, Includes the following steps: The gelling agent is added to the base oil and heated to 80-120°C. After cooling, the gel lubricant is obtained.

10. The application of the gel lubricant according to claim 7 or 8 or the gel lubricant prepared by the preparation method according to claim 9 in the field of bearing or metal friction pair lubrication.

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