Fatty alcohol-based eutectic solvent as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of tribology, and particularly relates to a fatty alcohol-based eutectic solvent as well as a preparation method and application thereof. The fatty alcohol-based eutectic solvent provided by the invention comprises the following component materials: fatty alcohol and quaternary ammonium salt; the number of carbon atoms in the fatty alcohol is 8-16, and the molar percentage of the fatty alcohol in the fatty alcohol and the quaternary ammonium salt is 20-80%. According to the fatty alcohol-based eutectic solvent provided by the invention, long-carbon-chain fatty alcohol is taken as a hydrogen bond donor, quaternary ammonium salt is taken as a hydrogen bond acceptor, and the proportion of the fatty alcohol to the quaternary ammonium salt is controlled, so that the prepared fatty alcohol-based eutectic solvent has good hydrophobicity, low viscosity, low freezing point and excellent wettability to a steel substrate; when used as a lubricant, the lubricating oil can reduce the friction coefficient under complex working conditions and reduce the wear to the surface of a friction pair, and shows excellent friction reduction and wear resistance. The fatty alcohol-based eutecticevaporate solvent disclosed by the invention can keep a low friction coefficient and a low wear volume in high load and long-time friction.

Description

Technical Field

[0001] The present invention belongs to the technical field of tribology, and particularly relates to a fatty alcohol-based deep eutectic solvent, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of industrial production and advanced manufacturing, the requirements for mechanical equipment by advanced technologies have been significantly improved. However, frequent and long-term continuous use will inevitably lead to friction and wear of mechanical components, which is not conducive to their normal operation, and may even have a certain impact on the surface structure and service life of mechanical equipment. Therefore, tribological problems such as friction and wear have become key factors directly affecting the performance and life of mechanical systems, and also the main causes of mechanical failures. In recent years, with in-depth scientific research, lubricating oils applied to mechanical surfaces can greatly reduce friction and wear, reduce or eliminate heat, transmit stress, and disperse wear, thereby improving the operating efficiency of mechanical equipment and extending the service life of mechanical equipment. Traditional lubricating oils mainly come from petroleum fractionation and animal and vegetable oil refining, and their production processes are relatively complex. At the same time, these lubricating oils will inevitably produce some pollutants or volatile substances during use, resulting in environmental pollution and reduced lubrication effects.

[0003] In order to reduce the impact on the environment, researchers have developed a green ionic liquid-like solvent called deep eutectic solvent (DES); DES is a stable solvent formed by a hydrogen bond acceptor (HBA) and a hydrogen bond donor (HBD) through hydrogen bonding, and the melting point is lower than that of each component. The decrease in the melting point mainly comes from the charge delocalization of the hydrogen bond formed between HBD and HBA.

[0004] Compared with the traditional synthetic lubricating oil, which has a complex preparation process, high cost, easy oxidation and deterioration, toxicity, and low biocompatibility, DES has the characteristics of simple preparation, low price, low toxicity or non-toxicity, good biocompatibility, degradability, and sustainability, and is widely used in metal material processing, nanomaterial synthesis, electrochemistry, catalysis, and material purification. In addition, DES has excellent physical and chemical properties, such as low volatility, low freezing point, high thermal stability, rheological properties, good affinity and wettability for metal substrates, and excellent corrosion resistance, and is widely used in lubricating materials.

[0005] In the field of tribology, DES mainly acts as a lubricant, lubrication additive, and gel lubrication material to exert its good lubrication performance. The reported DES lubricants are mainly based on choline chloride as HBA and amides, alcohols, and carboxylic acid compounds as HBD. The prepared choline chloride-based DES lubricants have excellent tribological properties. However, its inherent water absorption property makes it vulnerable to environmental moisture, so its application performance and service life in complex environments with high humidity are affected and limited to a certain extent. Summary of the Invention

[0006] In view of this, the present invention provides a fatty alcohol-based deep eutectic solvent, its preparation method and application. The fatty alcohol-based deep eutectic solvent provided by the present invention has good hydrophobicity and can exhibit excellent tribological properties for different friction pairs and working conditions when used as a lubricant.

[0007] To solve the above technical problems, the present invention provides a fatty alcohol-based deep eutectic solvent, which comprises a fatty alcohol and a quaternary ammonium salt;

[0008] The number of carbon atoms in the fatty alcohol is 8-16, and the molar percentage of the fatty alcohol in the fatty alcohol and the quaternary ammonium salt is 20-80%.

[0009] Preferably, the molar percentage of the fatty alcohol in the fatty alcohol and the quaternary ammonium salt is 25-70%.

[0010] Preferably, the fatty alcohol includes n-octanol, n-decanol, dodecanol or hexadecanol;

[0011] The quaternary ammonium salt includes tetrabutylammonium chloride, tetrabutylammonium bromide, methyltrioctylammonium chloride or tetraoctylammonium bromide.

[0012] Preferably, the viscosity of the fatty alcohol-based deep eutectic solvent at 25 °C is 0.4-0.5 Pa·s, and the contact angle on the steel substrate surface is 5-8°.

[0013] The present invention also provides a preparation method of the fatty alcohol-based deep eutectic solvent described in the above technical solution, which includes the following steps:

[0014] Mix the fatty alcohol and the quaternary ammonium salt according to the material dosage ratio to obtain the fatty alcohol-based deep eutectic solvent.

[0015] Preferably, the mixing is carried out under stirring.

[0016] Preferably, the temperature of the stirring is 40-70 °C.

[0017] Preferably, the rotation speed of the stirring is 400-600 rpm.

[0018] Preferably, the stirring time is 0.5-2 h.

[0019] The present invention also provides the application of the fatty alcohol-based deep eutectic solvent described in the above technical solution or the fatty alcohol-based deep eutectic solvent prepared by the preparation method described in the above technical solution as a lubricant in the field of friction lubrication.

[0020] The present invention provides a fatty alcohol-based deep eutectic solvent, comprising a fatty alcohol and a quaternary ammonium salt; the number of carbon atoms in the fatty alcohol is 8-16, and the molar percentage of the fatty alcohol in the fatty alcohol and the quaternary ammonium salt is 20-80%. In the present invention, the quaternary ammonium salt is used as a hydrogen bond acceptor (HBA), and the long-chain (with 8-16 carbon atoms) fatty alcohol is used as a hydrogen bond donor (HBD). Meanwhile, by controlling the ratio of the fatty alcohol and the quaternary ammonium salt, a complex hydrogen bond network is formed between the hydrogen bond acceptor and the hydrogen bond donor, obtaining a deep eutectic solvent with a freezing point lower than that of the component materials. Since the fatty alcohol and the quaternary ammonium salt adopted in the present invention have a long carbon chain structure, they can endow it with certain hydrophobic properties and lipophilic characteristics. Compared with the existing deep eutectic solvent (DES) lubricants, the fatty alcohol-based deep eutectic solvent provided by the present invention has characteristics such as good hydrophobicity, excellent wettability to the steel substrate, low freezing point, high thermal stability, low viscosity coefficient, and high wettability. When used as a lubricant, it can reduce the friction coefficient and significantly reduce the wear of the friction pair surface under complex working conditions (such as high load, high humidity application environment, and different friction pair materials), showing excellent friction reduction and anti-wear performance. In addition, the fatty alcohol-based deep eutectic solvent provided by the present invention has excellent load-bearing performance and can maintain a low friction coefficient and low wear volume during high-load (100-300 N) and long-time friction experiments. The fatty alcohol-based deep eutectic solvent provided by the present invention can be used as a new type of green lubricating material with low viscosity and high performance, playing a great role in the field of tribology, and further expanding the simple preparation of new deep eutectic solvents and their applications in friction or related fields.

[0021] The present invention provides a preparation method of the fatty alcohol-based deep eutectic solvent described in the above technical solution, comprising the following steps: mixing the fatty alcohol and the quaternary ammonium salt according to the material dosage ratio to obtain the fatty alcohol-based deep eutectic solvent. The present invention uses common green and inexpensive fatty alcohol and quaternary ammonium salt as raw materials, and mixes them by a simple stirring and heating method. By forming a complex hydrogen bond network structure between the hydrogen bond donor and the hydrogen bond acceptor, a green high-performance deep eutectic solvent with a low freezing point, low viscosity, high thermal stability, and high wettability is obtained. The raw materials adopted in the present invention are green and pollution-free, the preparation process is fast and simple, the synthesis conditions are mild, and it is easy to operate. Moreover, the environmental pollution is avoided to the greatest extent during the preparation process, which is an environmentally friendly and economical preparation method. Description of the Drawings

[0022] Figure 1 The DES structure and optical photograph of the fatty alcohol-based deep eutectic solvent prepared in Example 1;

[0023] Figure 2 The friction coefficient curve of the fatty alcohol-based deep eutectic solvent in Example 1 under a load of 100 N;

[0024] Figure 3Friction coefficient curves of the eutectic solvents obtained in Comparative Examples 1-3 under a 100 N load;

[0025] Figure 4 Friction coefficient curve of the fatty alcohol-based eutectic solvent of Example 1 under a 200 N load;

[0026] Figure 5 Friction coefficient curve of the fatty alcohol-based eutectic solvent of Example 1 under a 300 N load;

[0027] Figure 6 Friction coefficient curves of the fatty alcohol-based eutectic solvent of Example 1 under different friction pairs;

[0028] Figure 7 Physical process flow chart during the mixing, shaking and standing of the fatty alcohol-based eutectic solvent prepared in Example 1 and water in equal volume ratio;

[0029] Figure 8 Physical diagram of the eutectic solvent prepared in Comparative Example 1 after mixing with water in equal volume ratio. Detailed implementation manners

[0030] The present invention provides a fatty alcohol-based eutectic solvent, and the component materials include fatty alcohol and quaternary ammonium salt.

[0031] As a specific implementation manner of the present invention, the number of carbon atoms in the fatty alcohol is 8-16, and can be specifically 8, 10, 12 or 16; the fatty alcohol may include n-octanol (C8OH), n-decanol (C 10 OH), dodecanol (C 12 OH) or hexadecanol (C 16 OH), and can be specifically n-octanol, n-decanol, dodecanol and / or hexadecanol. In the present invention, the fatty alcohol is a hydrogen bond donor, the quaternary ammonium salt is a hydrogen bond acceptor, and the hydrogen bond donor and the hydrogen bond acceptor are mixed in a certain proportion and the fatty alcohol-based eutectic solvent is obtained by forming a hydrogen bond network.

[0032] As a specific implementation manner of the present invention, the quaternary ammonium salt may include tetrabutylammonium chloride, tetrabutylammonium bromide, methyltrioctylammonium chloride or tetraoctylammonium bromide. As a specific implementation manner of the present invention, the molar percentage of fatty alcohol in the fatty alcohol and quaternary ammonium salt is 20-80%, can be 25-70%, can also be 40-60%, and can further be 50-55%, and can be specifically 28.6%, 33%, 40%, 50%, 60% or 66.7%.

[0033] As a specific embodiment of the present invention, the viscosity of the fatty alcohol-based deep eutectic solvent at 25 °C can be 0.4 to 0.5 Pa·s, specifically 0.489 Pa·s, and the contact angle on the steel substrate surface can be 5 to 8°, specifically 6.6°.

[0034] In the present invention, quaternary ammonium salt is used as the hydrogen bond acceptor (HBA), and fatty alcohol containing a long alkyl chain is used as the hydrogen bond donor (HBD). At the same time, by reasonably controlling the ratio between the hydrogen bond acceptor and the hydrogen bond donor, a complex hydrogen bond network system is formed between the hydrogen bond acceptor and the hydrogen bond donor to obtain a deep eutectic solvent with good hydrophobicity. In the present invention, due to the presence of the long alkyl chain, the hydrogen bond network density is reduced, and to a certain extent, the hydrogen bond strength is reduced, so that the hydrophobic fatty alcohol-based deep eutectic solvent has a low viscosity coefficient while maintaining a low freezing point; in addition, since the fatty alcohol and quaternary ammonium salt used in the present invention have a long alkyl chain structure, it can endow them with certain hydrophobic properties and lipophilic characteristics. The fatty alcohol-based deep eutectic solvent provided by the present invention is a colorless and transparent liquid, with a low freezing point, high thermal stability, good fluidity and a small viscosity coefficient at room temperature and lower temperatures, and at the same time has good wettability on the steel substrate surface, can effectively reduce the internal friction of molecules during the friction and shear process, better reduce the friction coefficient, and exert its lubricating performance, and can achieve the effects of low friction coefficient and ultra-low wear on the steel surface and under high load conditions.

[0035] The fatty alcohol deep eutectic solvent lubricant provided by the present invention has excellent tribological properties when applied to the surface of a steel friction pair, has good load-carrying capacity and excellent friction reduction performance, and has broad application prospects.

[0036] The present invention also provides a preparation method of the fatty alcohol-based deep eutectic solvent described in the above technical solution, including the following steps:

[0037] Mix the fatty alcohol and the quaternary ammonium salt according to the material dosage ratio to obtain the fatty alcohol-based deep eutectic solvent.

[0038] As a specific embodiment of the present invention, the mixing can be carried out under stirring; the temperature of the stirring can be 40 to 70 °C, or 50 to 60 °C; the rotation speed of the stirring can be 400 to 600 rpm, or 450 to 500 rpm; the time of the stirring can be 0.5 to 2 h, or 1 to 1.5 h. As a specific embodiment of the present invention, a water bath heating method can be used to provide the temperature required for stirring; the stirring can be magnetic stirring.

[0039] As a specific embodiment of the present invention, after the mixing, it can also include: cooling the mixed system to room temperature and storing it in a glass container for later use; the temperature of the room temperature can be 20 to 35 °C, or 25 to 30 °C.

[0040] By selecting an appropriate heating temperature and with the assistance of stirring, the present invention can prepare a hydrophobic deep eutectic solvent based on fatty alcohol. The raw materials are economical and green, the preparation process is simple, easy to operate, and the atom utilization rate is 100%. Moreover, the preparation process minimizes or avoids the waste of raw materials and environmental pollution, meeting the development concept of high efficiency, green environmental protection.

[0041] The present invention also provides the application of the fatty alcohol-based deep eutectic solvent described in the above technical solution or the fatty alcohol-based deep eutectic solvent prepared by the preparation method described in the above technical solution as a lubricant in the field of friction lubrication. The present invention has no special requirements for the application method of the fatty alcohol-based deep eutectic solvent as a lubricant, and the methods well-known to those skilled in the art can be adopted. The fatty alcohol-based deep eutectic solvent provided by the present invention has good hydrophobicity, low viscosity coefficient and freezing point, high thermal stability and excellent wetting performance on the steel substrate; the tribological test results of the examples show that the fatty alcohol-based deep eutectic solvent exhibits excellent anti-friction and anti-wear performance under higher load conditions (100 - 300 N); therefore, the fatty alcohol-based deep eutectic solvent lubricant provided by the present invention has broad application prospects in the field of friction lubrication.

[0042] The fatty alcohol-based deep eutectic solvent provided by the present invention has excellent anti-friction and anti-wear performance and is a green, environmentally friendly and economical high-performance liquid lubricant.

[0043] In order to further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below in conjunction with examples, but they should not be construed as limiting the protection scope of the present invention.

[0044] Example 1

[0045] (1) 1.8633 g (0.01 mol) of dodecanol (C 12 OH) and 2.7792 g (0.01 mol) of tetrabutylammonium chloride (TBAC) were mixed by shaking and placed in a 20 mL glass container with a small magnetic stirrer, and then sealed with a sealing film.

[0046] (2) The glass container containing the mixture of dodecanol and tetrabutylammonium chloride in step (1) was placed in a water bath and heated and stirred at 50 °C for 1.0 h (stirring speed: 500 rpm) to obtain a transparent and colorless liquid solvent.

[0047] (3) The liquid solvent obtained in step (2) was naturally cooled to room temperature (25 °C), and the obtained fatty alcohol-based deep eutectic solvent was stored in a small glass bottle, denoted as TBAC-C 12 OH DES, and its DES structure and optical photograph are as Figure 1 shown.

[0048] From Figure 1 it can be seen that the prepared TBAC-C 12 OH DES is a colorless and transparent liquid at room temperature and has good fluidity.

[0049] Examples 2 to 6

[0050] The fatty alcohol-based deep eutectic solvent was prepared according to the method of Example 1, except that the dosage ratio of dodecanol and tetrabutylammonium chloride was specifically referred to Table 1.

[0051] Table 1 Dosage of dodecanol and tetrabutylammonium chloride in the preparation of fatty alcohol-based deep eutectic solvents in Examples 1 to 6

[0052]

[0053] Example 7

[0054] The fatty alcohol-based deep eutectic solvent was prepared according to the method of Example 1, except that the type of fatty alcohol was specifically referred to Table 2.

[0055] Table 2 Types and dosages of hydrogen bond donors and hydrogen bond acceptors in Example 7

[0056]

[0057]

[0058] The experimental results show that when fatty alcohols with different carbon chain lengths are used as hydrogen bond donors and tetrabutylammonium chloride is used as the hydrogen bond acceptor, the fatty alcohol-based deep eutectic solvent can be obtained under heating and stirring conditions. The prepared fatty alcohol-based deep eutectic solvents are all colorless and transparent liquids at room temperature and have good fluidity.

[0059] Comparative Example 1

[0060] (1) 1.3962 g (0.01 mol) of choline chloride (ChCl) and 1.2414 g (0.02 mol) of ethylene glycol (EG) were mixed by shaking and placed in a 20 mL glass container with a small magnetic stirrer, and then sealed with a sealing film.

[0061] (2) The glass container containing the mixture of choline chloride and ethylene glycol in step (1) was placed in a water bath and heated and stirred at 50 °C for 1.0 h (stirring speed: 500 rpm) to obtain a transparent and colorless liquid solvent.

[0062] (3) The liquid solvent obtained in step (2) was naturally cooled to room temperature (25 °C), and the obtained deep eutectic solvent was stored in a small glass vial, denoted as ChCl-EG DES.

[0063] Comparative Example 2

[0064] (1) 1.8633 g (0.01 mol) of dodecanol and 0.7511 g (0.005 mol) of Thymol were mixed by shaking and placed in a 20 mL glass container with a small magnetic stir bar, and then sealed with a sealing film.

[0065] (2) The glass container containing the mixture of choline chloride and ethylene glycol in step (1) was placed in a water bath and heated and stirred at 50 °C for 1.0 h (stirring speed: 500 rpm) to obtain a transparent and colorless liquid solvent.

[0066] (3) The liquid solvent obtained in step (2) was naturally cooled to room temperature (25 °C), and the obtained deep eutectic solvent was stored in a small glass vial, denoted as Thymol-C 12 OH DES.

[0067] Comparative Example 3

[0068] (1) 1.8633 g (0.01 mol) of dodecanol and 0.7814 g (0.005 mol) of L-Menthol were mixed by shaking and placed in a 20 mL glass container with a small magnetic stir bar, and then sealed with a sealing film.

[0069] (2) The glass container containing the mixture of choline chloride and ethylene glycol in step (1) was placed in a water bath and heated and stirred at 50 °C for 1.0 h (stirring speed: 500 rpm) to obtain a transparent and colorless liquid solvent.

[0070] (3) The liquid solvent obtained in step (2) was naturally cooled to room temperature (25 °C), and the obtained deep eutectic solvent was stored in a small glass vial, denoted as Menthol-C 12 OH DES.

[0071] In this invention, a SRV-V friction tester was used to conduct tribological tests on the fatty alcohol-based deep eutectic solvents prepared in the examples and the deep eutectic solvents prepared in the comparative examples. The ball-on-disk reciprocating mode was adopted during the test process; and a differential scanning calorimeter, a thermogravimetric analyzer, a rheometer and a contact angle tester were used to test their freezing points, thermal stabilities, viscosities and contact angle properties.

[0072] Test Example 1: Tribological Property Test of Fatty Alcohol-based Deep Eutectic Solvent

[0073] The tribological properties of the deep eutectic solvents prepared in Examples 1-7 and Comparative Examples 1-3 were tested using an SRV-V friction and wear testing machine. The upper friction pair used a steel ball (AISI 52100, HRC = 60 ± 2, D = 10 mm), and the lower friction pair used a cylindrical steel disc (AISI 52100, HRC = 60 ± 2, 24 mm × 7.9 mm); before and after the test, the upper and lower friction pairs were wiped clean with anhydrous ethanol, and after drying, they were installed on the friction testing machine; a dropper was used to separately suck the deep eutectic solvent and drop it onto the lower friction pair cylindrical steel disc for tribological testing; the test conditions were: load 100 N, stroke 1 mm, frequency 25 Hz, time 30 min; the friction coefficient curve and the corresponding wear volume of the wear scar were recorded.

[0074] The results measured under the condition of 100 N for the deep eutectic solvents of Examples 1-6 and Comparative Examples 1-3 applied on the surface of the steel-steel friction pair are listed in Table 3, and the results measured under the condition of 100 N for the fatty alcohol-based deep eutectic solvents prepared in Example 1 and Example 7 applied on the surface of the steel-steel friction pair are listed in Table 4. The friction coefficient curve of the fatty alcohol-based deep eutectic solvent prepared in Example 1 is as Figure 2 shown; the friction coefficient curves of the deep eutectic solvents obtained in Comparative Examples 1-3 on the steel surface are as Figure 3 shown.

[0075] Table 3 Tribological properties of the deep eutectic solvents prepared in Examples 1-6 and Comparative Examples 1-3 on the steel surface

[0076]

[0077] As can be seen from Table 3, when the ratios of fatty alcohol to quaternary ammonium salt are different, the corresponding changes in the friction coefficient are not obvious, and all show excellent tribological properties. Combining Figure 2 with Table 3, it can be seen that when the fatty alcohol-based deep eutectic solvent prepared in Example 1 is used as a lubricant on the steel surface, it shows excellent tribological properties under high load conditions, with an average friction coefficient of 0.090, and the average wear volume at the wear scar on the surface of the lower friction pair steel disc is 4.42×10 4 μm 3 ;

[0078] Combining Figure 3 with the friction coefficient curves and wear volumes in the comparative examples shown in Table 3, it shows that for the three DESs prepared in the comparative examples, including ChCl-EG DES, Thymol-C 12 OH DES and Menthol-C 12 OH DES lubricants, their average friction coefficients on the steel surface are 0.149, 0.143, and 0.145 respectively, and their average wear volumes are 348.04×10 4 μm3 and 53.84×10 4 μm 3 and 41.70×10 4 μm 3 . By comparison, due to the good rheological properties and excellent wettability to the steel substrate, the fatty alcohol-based deep eutectic solvent provided by the present invention has more excellent tribological properties on the steel surface, achieving a low friction coefficient and an ultra-low wear volume.

[0079] Table 4 Friction coefficient and wear volume of the deep eutectic solvents prepared in Example 1 and Example 7 on the steel surface

[0080]

[0081] It can be seen from the results in Table 4 that the fatty alcohol-based deep eutectic solvents with different carbon chain structures all show good tribological properties on the steel surface, and with the increase of the carbon chain, the measured friction coefficient and wear volume are basically the same. The experimental results show that when tetrabutylammonium chloride is used as the hydrogen bond acceptor, monohydric fatty alcohols with different carbon chain structures can all be used as hydrogen bond donors to construct the fatty alcohol-based deep eutectic solvents described in this patent, and the prepared fatty alcohol-based deep eutectic solvents show excellent tribological properties and can be used as a high-performance green lubricant in tribology and related fields.

[0082] Test Example 2: Tribological property test under high load conditions

[0083] The tribological properties of the deep eutectic solvent lubricants prepared in Example 1 and Comparative Examples 1-3 were tested using an SRV-V friction and wear testing machine. The upper friction pair used a steel ball (AISI52100, HRC = 60 ± 2, D = 10 mm), and the lower friction pair used a cylindrical steel disc (AISI52100, HRC = 60 ± 2, 24 mm × 7.9 mm); before and after the test, the upper and lower friction pairs were wiped clean with absolute ethanol, and after drying, they were installed on the friction testing machine; the deep eutectic solvents prepared in Example 1 and Comparative Examples 1-3 were respectively dipped with a dropper and applied to the cylindrical steel disc of the lower friction pair for tribological testing; the test conditions were: load 200 / 300 N, stroke 1 mm, frequency 25 Hz, time 30 min; record its friction coefficient curve, wear scar width and corresponding wear volume. The friction coefficient curve of Example 1 is as Figures 4 - 5 shown, where Figure 4 is the friction coefficient curve of the fatty alcohol-based deep eutectic solvent of Example 1 under a load of 200 N, Figure 5 is the friction coefficient curve of the fatty alcohol-based deep eutectic solvent of Example 1 under a load of 300 N; the obtained friction coefficient and corresponding wear volume results are listed in Table 5.

[0084] Table 5 Friction Coefficient and Wear Volume of DES in Example 1 and Comparative Examples 1-3 under High Load Conditions

[0085]

[0086]

[0087] Combined with Table 5 and Figures 4 - 5 it can be seen that TBAC-C 12 OH DES has good friction-reducing and anti-wear properties on the steel surface under high load conditions. Under the conditions of 200 N and 300 N, the average friction coefficients are 0.082 and 0.081 respectively, and the average wear volumes are 6.48×10 4 μm 3 and 8.72×10 4 μm 3 respectively; it shows that TBAC-C 12 OH DES has excellent force-bearing performance. While achieving a low friction coefficient, it can significantly reduce the friction and wear on the surface of the friction pair, especially achieving low friction and wear under high load conditions, which is of great significance for protecting the surface morphology, normal operation, and service life of mechanical devices.

[0088] The test results of the friction coefficients and wear volumes of the fatty alcohol-based deep eutectic solvents in Examples 2-6 under the high load conditions of 200 / 300 N are similar to those in Example 1.

[0089] Test Example 3: Tribological Performance Test under Different Friction Pair Conditions

[0090] The tribological performance of the TBAC-C 12 OH DES lubricant prepared in Example 1 was tested using an SRV-V friction and wear testing machine. The upper friction pair used a steel ball (AISI52100, HRC = 60±2, D = 10 mm), and the lower friction pair used a cylindrical copper disc / zirconia disc (24 mm×7.9 mm); before and after the test, the upper and lower friction pairs were wiped clean with anhydrous ethanol, and after drying, they were installed on the friction testing machine; the TBAC-C 12 OH DES lubricant in Example 1 was dipped with a dropper and applied to the lower friction pair cylindrical copper disc / zirconia disc for tribological testing; the test conditions were: load 100 N, stroke 1 mm, frequency 25 Hz, time 30 min; the friction coefficient curve, wear scar width, and corresponding wear volume were recorded.

[0091] The friction coefficient curves of the TBAC-C 12 OH DES prepared in Example 1 under different friction pair conditions are as Figure 6 shown. As can be seen from the figure, the TBAC-C12 OH DES on the surface of the steel - copper (Fe - Cu) friction pair, although the friction coefficient shows an upward trend during the test, the reason for the increase is mainly that the relatively soft copper block will deform to a certain extent as the friction test progresses under high load conditions, increasing the contact area, so the friction coefficient slightly increases. However, as the friction process further proceeds, its friction coefficient gradually decreases and stabilizes within a relatively small range, indicating that the TBAC - C 12 OH DES as a whole exhibits good lubrication performance, and its average friction coefficient during the whole process is 0.096; the friction coefficient on the surface of the steel - zirconia (Fe - ZrO2) friction pair is 0.089. The above results show that the TBAC - C prepared in the present invention 12 OH DES not only exhibits excellent tribological performance on the surface of the steel - steel friction pair, but also can be applied to different substrate surfaces, thereby reducing the friction and wear of the used substrate, which has far - reaching and important significance for its wide - range application.

[0092] The tribological performance test results of the fatty alcohol - based deep eutectic solvents in Examples 2 - 6 under different friction pair conditions are similar to those in Example 1.

[0093] Test Example 4: Hydrophobic property test of deep eutectic solvent lubricants

[0094] Hydrophobic DES is usually applicable to high - humidity environments, overcoming the drawback that the performance of traditional hydrophilic lubricants deteriorates due to water absorption. The deep eutectic solvents prepared in Example 1 and Comparative Example 1 were mixed with water in an equal - volume ratio, and after shaking and standing, the miscibility of DES and water was observed.

[0095] The physical process flow diagram during the process of mixing, shaking, and standing the fatty alcohol - based deep eutectic solvent prepared in Example 1 with water is as shown in Figure 7 shown, and the physical diagram after mixing the deep eutectic solvent prepared in Comparative Example 1 with water in an equal - volume ratio is as shown in Figure 8 shown. From Figure 7 and Figure 8 it can be seen that ChCl - EG DES can be fully miscible with water to form a homogeneous dispersion; while after mixing the fatty alcohol - based deep eutectic solvent of Example 1 with water, obvious stratification occurred. Although an emulsion was formed after shaking, obvious stratification was still observed after standing for 30 min, indicating that the fatty alcohol - based deep eutectic solvent prepared in the present invention is immiscible with water and exhibits excellent hydrophobic properties.

[0096] The hydrophobic property test results of the fatty alcohol - based deep eutectic solvents in Examples 2 - 6 are similar to those in Example 1.

[0097] Test Example 5: Physicochemical property test of deep eutectic solvents

[0098] The freezing point, thermal stability, viscosity, and contact angle (contact angle on the steel substrate surface) of the fatty alcohol-based deep eutectic solvent prepared in Example 1 were tested using a differential scanning calorimeter, thermogravimetric analyzer, rheometer, and contact angle tester, and the results are listed in Table 6.

[0099] Table 6 Physical properties of the fatty alcohol-based deep eutectic solvent prepared in Example 1

[0100]

[0101] The fatty alcohol-based deep eutectic solvents of Examples 2 to 6 have physical properties similar to those of Example 1.

[0102] It can be seen from the results in Table 6 that the fatty alcohol-based deep eutectic solvent provided by the present invention has good physicochemical properties, including a low freezing point, high thermal stability (thermal decomposition temperature), and excellent wetting properties (contact angle) on the steel substrate. At the same time, the experimental data in Tables 3 to 6 show that the fatty alcohol-based deep eutectic solvent provided by the present invention exhibits a low viscosity coefficient, which is beneficial to its flow and wetting on the friction pair surface and the reduction of internal molecular friction. Therefore, under high load conditions, it shows a low friction coefficient while maintaining a low wear volume. Therefore, the fatty alcohol-based deep eutectic solvent described in the present invention can be used as a green high-performance low-viscosity lubricating material in tribology and related fields.

[0103] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, not all embodiments. People can also obtain other embodiments based on these embodiments without creative efforts, and these embodiments all belong to the protection scope of the present invention.

Claims

1. A fatty alcohol-based deep eutectic solvent, characterized in that: Includes fatty alcohols and quaternary ammonium salts; The carbon number of the fatty alcohol is 8 to 16, and the molar percentage of the fatty alcohol in the fatty alcohol and the quaternary ammonium salt is 20 to 80%.

2. The fatty alcohol-based deep eutectic solvent according to claim 1, characterized in that The molar percentage of the fatty alcohol in the fatty alcohol and the quaternary ammonium salt is 25-70%.

3. The fatty alcohol-based deep eutectic solvent according to claim 1, characterized in that: The fatty alcohol includes n-octanol, n-decanol, dodecanol or hexadecanol; The quaternary ammonium salt includes tetrabutylammonium chloride, tetrabutylammonium bromide, methyltrioctylammonium chloride or tetraoctylammonium bromide.

4. The fatty alcohol-based deep eutectic solvent according to any one of claims 1 to 3, characterized in that The viscosity of the fatty alcohol-based low eutectic solvent at 25° C. is 0.4-0.5 Pa·s, and the contact angle on the surface of the steel substrate is 5-8°.

5. The method for preparing the fatty alcohol-based deep eutectic solvent according to any one of claims 1 to 4, characterized in that: The following steps are involved: The fatty alcohol and the quaternary ammonium salt are mixed according to the material dosage ratio to obtain the fatty alcohol-based low eutectic solvent.

6. The preparation method according to claim 5, characterized in that: The mixing is performed under stirring conditions.

7. The preparation method according to claim 6, characterized in that: The stirring temperature is 40-70°C.

8. The preparation method according to claim 6 or 7, characterized in that: The stirring speed is 400-600 rpm.

9. The preparation method according to claim 8, characterized in that: The stirring time is 0.5 to 2 hours.

10. Use of the fatty alcohol based deep eutectic solvent according to any one of claims 1 to 4 or the fatty alcohol based deep eutectic solvent prepared by the preparation method according to any one of claims 5 to 9 as a lubricant in the field of friction lubrication.

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