Ionic liquid for titanium alloy surface lubricating additive and preparation method of ionic liquid

Abstract

The invention discloses ionic liquid for a titanium alloy surface lubricating additive and a preparation method of the ionic liquid, and belongs to the technical field of metal lubricants. The general formula of the ionic liquid compound is A < + > B <->, A < + > represents organic cations, and B <-> represents organic anions. The ionic liquid disclosed by the invention has more stable and smaller friction coefficient and more excellent lubricity, can simultaneously have antibacterial, corrosion-resistant and extreme pressure properties, and is particularly applied to a titanium alloy friction pair. Besides, compared with the traditional ionic liquid, the ionic liquid provided by the invention does not need complex steps of ion exchange, separation, purification and the like in the synthesis process, the preparation process is simple, the required raw materials are wide in source, and the cost is low.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal lubricants and biological lubricants, and particularly relates to an ionic liquid applied to a titanium alloy surface and used as a lubricating oil additive and a preparation method thereof. BACKGROUND

[0002] Titanium alloy has unique biocompatibility, corrosion resistance, high temperature resistance, high specific strength and surface modification, and is widely used in special fields such as aviation, aerospace, ocean and automobile. In addition, titanium alloy also has important application value in medical treatment, industry and daily production and life. However, titanium alloy itself has poor tribological performance and low plastic shear resistance, which leads to serious friction and wear problems in the processing and application process. As a high-performance lubricating material, ionic liquid has the properties of low melting point, low volatility, high thermal stability, wide liquid temperature range, non-flammability and non-explosiveness, biodegradability, non-toxicity or low toxicity, and is expected to become a high-performance, multi-purpose and environment-friendly lubricant, which is applied to special mechanical lubrication under harsh conditions, so the research on the tribological performance of ionic liquid has attracted great attention.

[0003] Ionic liquid is called "designable" liquid due to the high controllability of the molecular structure of anion and cation. It has high polarity and strong reactivity, can preferentially adsorb on the titanium alloy interface and generate a composite lubricating film containing fluorine, phosphorus or boron in situ, and significantly reduce the friction coefficient and wear amount. At the same time, by introducing functional groups such as hydroxyl, carboxyl and phosphate into the cation or selecting functional anions in the molecular design, the viscosity, thermal stability and shear response can be further controlled, so that the lubricant still has the characteristics of low volatility, self-repairing and strong adsorption under extreme conditions such as 200 ℃ and high load, thereby providing a precise matching high-efficiency lubrication solution for the complex service conditions of titanium alloy.

[0004] Studies have shown that due to the active nature of titanium element, a dense oxide film is easily formed on the surface of titanium alloy material in air, which makes it difficult for many liquid lubricants to interact with the titanium alloy surface, especially the untreated alloy surface, which is difficult to form a stable lubricating film. For example, traditional lubricants such as mineral oil and poly-alpha olefin cannot provide good lubrication effect on titanium alloy. Therefore, people try to apply high-polarity ionic liquid to titanium alloy in the hope of improving the poor tribological performance of titanium alloy. Jimenez et al. reported the use of imidazole ionic liquid as a lubricant for steel / titanium friction pair, and the results showed that compared with traditional mineral oil, the use of Cl - , BF4 - or PF6 - , TFSI -Imidazolium-based ionic liquids can effectively reduce the friction and wear of titanium alloy (Tribol Lett, 2009, 33(2): 111−126). Li et al. reported the effect of different molecular structure of fluorine-containing ionic liquid lubricants such as tetrafluoroborate and perfluorosulfonate on the tribological properties of TC21 titanium alloy, and the results showed that perfluorosulfonate ionic liquid was an excellent lubricant for TC21 titanium / Si3N4 friction pair (J. Alloys Compd. 2018, 743:576-585).

[0005] However, the above-mentioned ionic liquid lubricants are halogen-containing compounds, and their use cannot meet the current environmental protection requirements. At the same time, the cost of ionic liquid itself is relatively high, and there are certain limitations in practical application. However, as an additive, it can not only improve the tribological properties of titanium alloy surface, but also meet the application requirements of economy and environmental protection. Therefore, with the continuous enhancement of human environmental protection consciousness, the development of halogen-free green environmental protection ionic liquid lubricant additives to improve the tribological properties of titanium alloy has become one of the important contents of current lubrication field research. SUMMARY

[0006] In view of the deficiencies of the prior art, the first purpose of the present application is to provide an ionic liquid used as a titanium alloy surface lubricating additive. The ionic liquid has a simple preparation process and good antibacterial, corrosion-resistant, load-bearing and friction-reducing and wear-resistant properties, and is an excellent lubricating additive.

[0007] In order to achieve the above technical purpose, the present inventors have carried out a large number of experimental researches and have finally obtained the following technical scheme: an ionic liquid compound, the general formula of the ionic liquid compound is A + B - , wherein A + represents an organic cation, B - represents an organic anion.

[0008] The organic cation is selected from any one of the following: , , , ; wherein the substituent R is a straight-chain alkyl group with 4-8 carbon atoms;

[0009] The organic anion is selected from one of the following:

[0010] ; .

[0011] It should be noted that the technical principle of the present application is that the organic anion is bulky and has highly delocalized charge, and has extremely weak coordination ability and low lattice energy; the organic cation is also bulky and has dispersed charge. When two raw materials of the organic anion and the organic cation are mixed in a solution, although there is electrostatic attraction between the organic anion and the organic cation, the organic anion and the organic cation cannot form a stable three-dimensional lattice due to large steric hindrance and low charge density. On the contrary, the multiple interactions such as van der Waals force, hydrophobic interaction and hydrogen bond between the anion and the cation are sufficient to maintain the ion pair, but are insufficient to crystallize, thereby destroying the lattice structure of the original salt, and the system can be melted into a liquid state at room temperature or slightly higher than room temperature, so that the ionic liquid is synthesized.

[0012] Further preferably, the ionic liquid compound as described above, wherein the substituent R is n-butyl or n-octyl.

[0013] Further preferably, the ionic liquid compound as described above, wherein the organic cation is selected from any one of the following:

[0014] ; ; ;

[0015] ; ; ; .

[0016] In addition, a second object of the present application is to provide a preparation method of the above-mentioned ionic liquid compound, which comprises the following steps: dissolving a compound A providing the organic cation and a compound B providing the organic anion in deionized water respectively, then mixing the two solutions, stirring and reacting at room temperature, extracting the obtained reaction solution with an organic solvent, washing with deionized water, and finally removing the solvent by rotary evaporation to obtain the target product.

[0017] The ionic liquid compound prepared by the present application, wherein the organic anion is mainly provided by rigid rings (potassium acetylsulfanate and sodium o-benzoylsulfonamide), and the organic cation is mainly provided by tetrabutylphosphonium bromide, tetraoctylphosphonium bromide, tetrabutylammonium bromide, tetraoctylammonium bromide, methyltrioctylammonium bromide, n-octyltrimethylammonium bromide, and methyltributylammonium bromide; the structural formula of the above-mentioned compounds is shown in Figure 1 .

[0018] Further preferably, the preparation method of the ionic liquid compound as described above, when the two reaction raw materials are mixed, the molar ratio of the organic cation in the compound A to the organic anion in the compound B is 1: (1-3).

[0019] Further preferably, the reaction time after mixing the two reaction materials is 6-18 hours.

[0020] Further preferably, the method for preparing the ionic liquid compound is as described above, wherein the organic solvent used for extraction is dichloromethane.

[0021] Further preferably, the method for preparing the ionic liquid compound is as described above, wherein after removing the solvent by rotary evaporation, a drying treatment is further performed, specifically, drying in a vacuum drying oven at 60-80 ℃ for 12-24 hours.

[0022] The inventors evaluated the lubricating performance of the ionic liquid as a lubricant by using a SRV5 micro-vibration friction and wear tester produced by the German optimol oil company. Polyethylene glycol was selected as the base lubricant system, and different concentrations of ionic liquid were added as additives, and a comparative experiment on tribological performance was performed. The test conditions selected in the tribological experiment are: load 50 N-200 N, temperature 25 ℃, frequency 25 Hz, amplitude 1 mm, and experimental time 30 min; in the steel / titanium friction pair, the upper test ball is an ASI 5200 steel ball with a hardness of 59-61 HRC and a diameter of 10 mm, and the lower test disc is a Ti6Al4V alloy disc with a hardness of 30-35 HRC, a diameter of 24 mm and a thickness of 7.9 mm (the surface is treated with 800 mesh, 1000 mesh and 1500 mesh sandpaper respectively). The wear volume of the lower sample was measured by a BRUKER-NPFLEX three-dimensional optical profiler. The experimental results show that the ionic liquid as a polyethylene glycol-based lubricating additive significantly improves the load-carrying performance of the base oil, and the friction coefficient is very small and stable. Therefore, the third object of the present application is to provide the use of the ionic liquid compound as a lubricating additive for titanium alloy. Further preferably, when the ionic liquid compound is used as a lubricating additive for titanium alloy, it needs to be added to polyethylene glycol to prepare a solution with a concentration of 0.5wt%-5wt%.

[0023] Compared with the prior art, the ionic liquid and the preparation method thereof provided by the present application have the following advantages and significant progress:

[0024] (1) The ionic liquid provided by the present application has a more stable and smaller friction coefficient and more excellent lubricating performance, and also has corrosion resistance, extreme pressure performance and antibacterial performance, and is particularly suitable for titanium alloy friction pairs.

[0025] (2) Compared with traditional ionic liquids, the ionic liquid provided by the present application does not need to perform ion exchange, separation, purification and other complex steps in the synthesis process, the preparation process is simple, the source of the required raw materials is green, the anion belongs to a food saccharin additive, and meets the application requirements of sustainability and environmental protection. Attached Figure Description

[0026] Figure 1 : Compounds that provide organic cations and organic anions for the preparation of ionic liquids;

[0027] Figure 2 : 1H NMR spectrum (a) and 1C NMR spectrum (b) of sample AK-N4444;

[0028] Figure 3 : 1H NMR spectrum (a) and 1C NMR spectrum (b) of sample AK-P4444;

[0029] Figure 4 : 1H NMR spectrum (a) and 1C NMR spectrum (b) of sample AK-N8881;

[0030] Figure 5 : 1H NMR spectrum (a) and 1C NMR spectrum (b) of sample SA-P4444;

[0031] Figure 6 : NMR spectrum of sample SA-P8888 (H1N and C1N) (b);

[0032] Figure 7 : 1H NMR spectrum (a) and 1C NMR spectrum (b) of sample SA-N4444;

[0033] Figure 8 : 1H NMR spectrum (a) and 1C NMR spectrum (b) of sample SA-N8888;

[0034] Figure 9 : 1H NMR spectrum (a) and 1C NMR spectrum (b) of sample SA-NN8881;

[0035] Figure 10 : 1H NMR spectrum (a) and 1C NMR spectrum (b) of sample SA-N8111;

[0036] Figure 11 : 1H NMR spectrum (a) and 1C NMR spectrum (b) of sample SA-N4441;

[0037] Figure 12 Infrared spectra of different ionic liquids;

[0038] Figure 13 : Diagram showing the antibacterial effect of ionic liquids. Detailed Implementation

[0039] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments, but the embodiments are not intended to limit the scope of protection of the present invention.

[0040] Example 1: Preparation of AK-N4444 ionic liquid

[0041] Into a 100 mL round bottom flask, 3.223 g (10 mmol) of tetrabutylammonium bromide and 2.012 g (10 mmol) of potassium acetylsulfonate were added with 20 mL of deionized water for each, to obtain two solutions. After mixing the two solutions, the reaction was completed after stirring for 12 h. Then, the reaction solution was extracted with dichloromethane as the extractant, and washed with deionized water for more than three times to remove inorganic salt impurities. After water washing, the organic phase was removed by rotary evaporation to remove the solvent, and then dried in a vacuum drying oven at 60 °C for 12 h to obtain the ionic liquid (denoted as AK-N4444), the carbon and hydrogen nuclear magnetic resonance spectra of which are shown in Figure 2 Figure 3 Figure 4

[0042] Example 2: Preparation of SA-P4444 ionic liquid

[0043] Into a 100 mL round bottom flask, 3.393 g (10 mmol) of tetrabutylphosphonium bromide and 2.052 g (10 mmol) of sodium o-benzoylsulfonamide were added with 20 mL of deionized water for each, to obtain two solutions. After mixing the two solutions, the reaction was completed after stirring for 12 h. Then, the reaction solution was extracted with dichloromethane as the extractant, and washed with deionized water for more than three times to remove inorganic salt impurities. After water washing, the organic phase was removed by rotary evaporation to remove the solvent, and then dried in a vacuum drying oven at 60 °C for 12 h to obtain the ionic liquid (denoted as SA-P4444), the carbon and hydrogen nuclear magnetic resonance spectra of which are shown in Figure 5 Figure 6 Figure 7 Figure 8

[0044] Example 3: Preparation of SA-N8881 ionic liquid

[0045] ​​​​​​​Into a 100 mL round bottom flask, 4.486 g (10 mmol) of trioctylmethylammonium bromide and 2.052 g (10 mmol) of sodium o-benzoylsulfonamide were added, each with 20 mL of deionized water to obtain two solutions. The two solutions were mixed and stirred for 12 h after mixing to complete the reaction. After that, the reaction solution was extracted with dichloromethane as the extractant, and washed with deionized water three times or more to remove inorganic salt impurities. After water washing, the organic phase was removed by rotary evaporation to remove the solvent, and then dried in a vacuum drying oven at 60 ℃ for 12 h to obtain the ionic liquid (denoted as SA-N8881), the carbon and hydrogen nuclear magnetic resonance spectra of which are shown in Figure 9 The ionic liquids SA-N8111 and SA-N4441 were prepared by the method of Example 3, and the carbon and hydrogen nuclear magnetic resonance spectra thereof are shown in Figure 10 、 Figure 11 respectively.

[0046] Example 4: Characterization of the structure of ionic liquid compounds

[0047] The structures of the ionic liquid compounds prepared in Examples 1-3 were characterized by Fourier infrared spectroscopy, as shown in Figure 12 In (a) and (b), the absorption peaks near 2960 cm -1 , 2870 cm -1 and 2920 cm -1 , 2850 cm -1 belong to the absorption of methyl and methylene groups, respectively. Figure 12 The characteristic absorption peak at 1630 cm -1 in (b) is the stretching vibration of the cyclic imide carbonyl group, which corresponds to the carbonyl group in the anion. The characteristic absorption peaks of the skeleton stretching vibration of the benzene ring are at 1450 cm -1 and 1580 cm -1 , and the strong absorption peaks at 1140 cm -1 , 1260 cm -1 , 1320 cm -1 indicate the presence of sulfonyl groups in the ionic liquid, confirming the formation of the target product.

[0048] Example 5: Determination of the thermal stability of ionic liquids

[0049] The thermal stability of the ionic liquids was tested by a simultaneous thermal analyzer (STA449F3, TG, NETZSCH, Germany) (TGA) ). Thermal stability is conducive to the stability of ionic liquid lubricant additives during shearing process, and plays a long-term lubrication role. As can be seen from Table 1, the thermal decomposition temperatures of the 10 ionic liquids show the following trend: SA-P8888 (377.6 ℃) > SA-P4444 (374.0 ℃) > AK-P4444 (280.9 ℃) > SA-N8111 (260.4 ℃) > AK-N4444 (259.6 ℃) > AK-N8881 (258.7 ℃) > SA-N8881 (253.1 ℃) > SA-N4441 (252.5 ℃) > SA-N8888 (251.8 ℃) > SA-N4444 (240.1 ℃), and their high thermal decomposition temperatures enable the lubricant to maintain its original performance in a high-temperature environment.

[0050] Table Thermogravimetric curve inflection point of different ionic liquids

[0051]

[0052] Example 6: Determination of adsorption frequency and dissipation value of ionic liquid on chip

[0053] Titanium alloy exhibits high reactivity and surface passivation layer, forming a unique adsorption behavior. The adsorption performance was tested by dissipation quartz crystal microbalance (QCM-D, Biolin Scientific, Sweden), and AK-P4444, AK-N4444 and AK-N8881 were prepared into 5 wt% ethanol solution. The adsorption frequency (Δf) and dissipation value (ΔD) of the ionic liquid on the Ti chip (Ti6Al4V) were tested, and the results are shown in Table 2. As can be seen from Table 2, the adsorption of AK-P4444, AK-N4444 and AK-N8881 changes greatly, and after desorption, they all return to 0 Hz, indicating that the chemical adsorption of ionic liquid on the surface of titanium alloy is stronger.

[0054] Table Adsorption frequency and dissipation value of different ionic liquids on Ti chip

[0055]

[0056] SA-P4444, SA-P8888, SA-N4444, SA-N8888, SA-N8881, SA-N8111 and SA-N4441 were prepared into 2 wt% ethanol solution, and the adsorption frequency (Δf) and dissipation value (ΔD) of the lubricant on Au chip were tested, and the results are shown in Table 3. From Table 3, it can be seen that the adsorption of SA-P4444, SA-P8888, SA-N4444, SA-N8888, SA-N8881, SA-N8111 and SA-N4441 on Au chip is relatively small, and the adsorption frequency (Δf) and dissipation value (ΔD) of the lubricant on Au chip are relatively small. It can be seen that the synthesized ionic liquid desorption can not return to 0 Hz, indicating that the chemical adsorption of ionic liquid on the Au surface is stronger, and the symmetry of the cation also affects the adsorption behavior. The Δf value of the asymmetric structure is smaller than that of the symmetric structure. The length of the carbon chain of the cation also affects the adsorption behavior. The results show that the ionic liquid synthesized by the cation with short carbon chain is better adsorbed.

[0057] Table Adsorption frequency and dissipation value of different ionic liquids on Au chip

[0058]

[0059] Example 7: Determination of the friction performance of 1wt% ionic liquid

[0060] Friction test conditions: load 50 N, frequency 25 Hz, amplitude 1 mm, experimental time 30 min, temperature 25℃, the diameter of the upper test ball is 10 mm, and the lower test sample is a titanium block with a hardness of 300 HV. The ionic liquid is prepared into a 1% mass fraction polyethylene glycol solution. The average friction coefficient and wear volume obtained by testing are shown in Table 4.

[0061] Table Average friction coefficient and wear volume of 1wt% ionic liquid

[0062]

[0063] Example 8: Determination of the friction performance of 5wt% ionic liquid

[0064] Friction test conditions: load 100 N, frequency 25 Hz, amplitude 1 mm, experimental time 30 min, temperature 25℃, the diameter of the upper test ball is 10 mm, and the lower test sample is a titanium block with a hardness of 300 HV. The ionic liquid is prepared into a 5% mass fraction polyethylene glycol solution. The average friction coefficient and wear volume obtained by testing are shown in Table 5.

[0065] Table Average friction coefficient and wear volume of 5wt% ionic liquid

[0066]

[0067] Example 9: Determination of the antibacterial performance of ionic liquid

[0068] Polyethylene glycol lubricant is widely used in medicine, cosmetics and industry because of its good water solubility, biocompatibility, lubricity and low irritation. The anion of the ionic liquid involved in the application is green, so that the ionic liquid polyethylene glycol lubricant constructed exhibits excellent environmental protection. On this basis, the antibacterial property of the ionic liquid is compared by experiment, and the strain is S. aureus. The test data is shown in Table 6, and the ionic liquid shows significant antibacterial activity to S. aureus, thereby showing certain antibacterial property, which meets the development requirement of sustainable lubrication technology.

[0069] Table 6 antibacterial property of ionic liquid

[0070]

Claims

1. An ionic liquid compound, characterized by, The general formula of the ionic liquid compound is A + B - , wherein A + represents an organic cation, B - represents an organic anion; The organic cation is selected from any one of: , , , ; wherein the substituent R is a straight-chain alkyl group of 4 to 8 carbon atoms; The organic anion is selected from one of the following: ； 。 2. The ionic liquid compound according to claim 1, characterized in that, The substituent R is n-butyl or n-octyl.

3. The ionic liquid compound according to claim 1 or 2, characterized in that, The organic cation is selected from any one of the following: ； ； ； ； ； ； 。 4. A process for the preparation of the ionic liquid compound according to claim 1, characterized by, The method comprises the following steps: dissolving the compound A providing the organic cation and the compound B providing the organic anion in deionized water respectively, then mixing the two solutions, stirring the reaction at room temperature, extracting the obtained reaction solution with an organic solvent, washing with deionized water, and finally removing the solvent by rotary evaporation to obtain the target product.

5. The method for preparing the ionic liquid compound according to claim 4, characterized in that, The molar ratio of the organic cation in the compound A to the organic anion in the compound B during mixing is 1: (1-3).

6. The method of claim 4, wherein the ionic liquid compound is prepared by the steps of: a) dissolving a compound of formula (I) in a solvent; b) adding a base to the solution; and c) removing the solvent from the solution. The reaction time of the reaction is 6-18 h.

7. The method for preparing the ionic liquid compound according to claim 4, characterized in that, The organic solvent is dichloromethane.

8. The method for preparing the ionic liquid compound according to claim 4, characterized in that, After removing the solvent by rotary evaporation, drying in a vacuum drying oven at 60-80 ℃ for 12-24 h.

9. Use of the ionic liquid compound of claim 1 as a lubricating additive for titanium alloy.

10. Use according to claim 9, characterized in that, The use concentration of the ionic liquid compound as a lubricating additive for titanium alloy is 0.5wt%-5wt%.

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