A proton-type polyionic liquid, a preparation method thereof, and its application as a water-based viscosity-increasing lubricating additive

Abstract

The present invention provides a proton-type polyionic liquid, a preparation method thereof, and an application as a water-based thickening lubricant additive, belonging to the technical field of lubricants. The cation of the proton-type polyionic liquid of the present invention is a copolymer of N-vinyl pyrrolidone and dimethylaminoethyl methacrylate, and the anion is an alkyl carboxylate anion or a dibutyl phosphate anion. The active nitrogen element in its molecular structure can undergo a tribochemical reaction with the interface of the friction pair sliding against each other to form a tribochemical protective film, which can not only improve the friction reduction and anti-wear performance of the water-based lubricant, but also improve its extreme pressure bearing performance. The alkyl carboxylate anion or the dibutyl phosphate anion can be adsorbed onto the interface of the metal friction pair to form a physical adsorption film, which significantly improves the lubrication performance of the lubricant. The proton-type polyionic liquid aqueous solution has a high viscosity and has good film-forming ability on the surface of the friction pair. The physical adsorption film, the viscous liquid film, and the tribochemical reaction film work synergistically to effectively improve the friction reduction and anti-wear performance and bearing performance of the water-based lubricant.

Description

Technical Field

[0001] The present invention relates to the technical field of lubricants, and in particular to a proton-type polyionic liquid, a preparation method thereof, and an application thereof as a water-based viscosity-increasing lubricating additive. Background Art

[0002] According to statistics, friction accounts for approximately one-half to one-third of global energy consumption. Furthermore, approximately 80% of damaged parts are caused by various forms of wear. Therefore, controlling friction and wear is a crucial measure for conserving energy and protecting mechanical components. Compared to oil-based lubricants, which are prone to environmental pollution, water-based lubrication technology has attracted widespread attention due to its advantages such as widespread availability, flame retardancy, high specific heat capacity and thermal conductivity, environmental friendliness, and excellent cleaning performance. However, current water-based lubricants still have drawbacks, such as poor lubrication, low viscosity, and poor film-forming and corrosion resistance. The addition of water-based lubricant additives can significantly improve their physical and chemical properties and lubrication performance. Therefore, the development of water-based lubricant additives with high viscosity, excellent corrosion resistance, and superior friction and anti-wear properties is of great significance.

[0003] Ionic liquids are organic molten salts with a melting point below 100°C composed of organic cations and organic or inorganic anions. They have the advantages of low vapor pressure, high thermal and chemical stability, and flame retardancy. However, when ionic liquids are used as water-based lubricant additives, they cannot significantly increase the viscosity and film-forming properties of water-based lubricants. Polyionic liquids are a type of ionic polymer formed by the polymerization of monomers containing ionic liquid structures as repeating units. Polyionic liquids not only have the excellent lubrication properties of ionic liquids, but also have the high viscosity characteristics of polymers. However, the viscosity of water-based lubricants prepared with polyionic liquids in the prior art is still relatively low, the friction coefficient and wear volume are still relatively high, and the corrosion resistance needs to be further improved. Summary of the Invention

[0004] In light of this, the present invention aims to provide a proton-type polyionic liquid, its preparation method, and its use as a water-based viscosity-enhancing lubricant additive. When used as a water-based lubricant additive, the proton-type polyionic liquid provided by the present invention can significantly increase the kinematic viscosity of the water-based lubricant, reduce the friction coefficient and wear volume of the water-based lubricant, and exhibit excellent corrosion resistance.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a proton-type polyionic liquid comprising a cation and an anion, wherein the cation is a copolymer of N-vinyl pyrrolidone and dimethylaminoethyl methacrylate, and the anion is an alkyl carboxylate anion and / or a dibutyl phosphate anion;

[0007] The cation has a structure shown in Formula I:

[0008]

[0009] In formula I, m:n = 5:1 to 1:5.

[0010] Preferably, the alkyl carboxylate anion has a structure shown in Formula II:

[0011]

[0012] In Formula II, x is any integer from 1 to 11.

[0013] Preferably, the alkyl carboxylate anion includes one or more of acetate anion, butyrate anion, hexanoate anion, octanoate anion and laurate anion.

[0014] Preferably, the dibutyl phosphate anion has a structure shown in Formula III:

[0015]

[0016] The present invention provides a method for preparing the above-mentioned proton-type polyionic liquid, comprising the following steps:

[0017] Dimethylaminoethyl methacrylate, an anion raw material and a solvent are mixed to perform a proton exchange reaction to obtain a proton exchange reaction solution; the anion raw material is an alkyl carboxylic acid and / or dibutyl phosphate;

[0018] The proton exchange reaction liquid, N-vinyl pyrrolidone and an initiator are mixed and polymerized to obtain a proton-type polyionic liquid.

[0019] Preferably, the molar ratio of dimethylaminoethyl methacrylate to anion raw material is 1 to 2:1;

[0020] The molar ratio of N-vinyl pyrrolidone to dimethylaminoethyl methacrylate is 5:1 to 1:5.

[0021] Preferably, the initiator comprises one or more of ammonium persulfate, potassium persulfate and sodium persulfate;

[0022] The mass of the initiator is 0.003-1% of the total mass of dimethylaminoethyl methacrylate and the anion raw material.

[0023] Preferably, the polymerization reaction temperature is 50-90° C., and the time is 1-36 hours.

[0024] The present invention provides the use of the proton-type polyionic liquid as a water-based viscosity-increasing lubricating additive.

[0025] The present invention provides a water-based lubricant product, comprising a water-based base lubricating fluid and the above-mentioned proton-type polyionic liquid;

[0026] The water-based lubricating fluid includes one or more of water, water-ethylene glycol mixture, water-glycerin mixture, and water-ethylene glycol-glycerin mixture;

[0027] The mass concentration of the proton-type polyionic liquid in the water-based lubricant product is 0.1-40 wt %.

[0028] The present invention provides a protic polyionic liquid comprising a cation and an anion. The cation is a copolymer of N-vinyl pyrrolidone and dimethylaminoethyl methacrylate, and the anion is an alkyl carboxylate anion and / or a dibutyl phosphate anion. The cation has the structure shown in Formula I. The present invention uses the copolymer of N-vinyl pyrrolidone and dimethylaminoethyl methacrylate as the cation. The molecule contains a tertiary amine, which has a certain alkalinity. The carboxyl functional group in the alkyl carboxylic acid or the hydroxyl functional group in the dibutyl phosphate molecular structure has a certain acidity. The two can be reacted through a simple proton exchange reaction to produce an ionic monomer [dimethylaminoethyl methacrylate][alkyl carboxylic acid] or [dimethylaminoethyl methacrylate][dibutyl phosphate salt]. This ionic monomer is copolymerized with N-vinyl pyrrolidone to produce a protic polyionic liquid. This protic polyionic liquid has good solubility in water-based lubricants. The alkyl carboxylate anion or dibutyl phosphate anion can be effectively adsorbed to the interface of the metal friction pair, forming a physical adsorption film, which can significantly improve the lubrication performance of the water-based lubricant. In addition, the physical adsorption film can effectively isolate the metal surface from the water-based lubricant, greatly improving the metal's corrosion resistance. At the same time, the proton-type polyionic liquid aqueous solution provided by the present invention has a high viscosity and good film-forming ability on the friction pair surface.

[0029] Furthermore, the active nitrogen in the polymer's molecular structure undergoes a tribochemical reaction with the sliding friction pair, forming a tribochemical protective film. The synergistic effect of the physical adsorption film, the viscous liquid film, and the tribochemical reaction film effectively enhances the water-based lubricant's anti-friction and anti-wear properties, as well as its load-bearing performance.

[0030] The present invention provides a method for preparing the above-mentioned proton-type polyionic liquid. The proton-type polyionic liquid of the present invention can be obtained by one-step polymerization. The preparation method is simple, does not require complex steps such as ion exchange, and is easy to produce on a large scale. DETAILED DESCRIPTION

[0031] The present invention provides a proton-type polyionic liquid comprising a cation and an anion, wherein the cation is a copolymer of N-vinyl pyrrolidone and dimethylaminoethyl methacrylate, and the anion is an alkyl carboxylate anion and / or a dibutyl phosphate anion;

[0032] The cation has a structure shown in Formula I:

[0033]

[0034] In Formula I, m:n=5:1 to 1:5, and specifically preferably 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4 or 1:5.

[0035] In the present invention, the alkyl carboxylate anion has a structure shown in Formula II:

[0036]

[0037] In Formula II, x is any integer from 1 to 11, preferably from 3 to 10, more preferably from 5 to 8, and specifically preferably 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11.

[0038] In the present invention, the alkyl carboxylate anion preferably includes one or more of acetate anion, butyrate anion, hexanoate anion, octanoate anion and laurate anion.

[0039] In the present invention, the dibutyl phosphate anion has a structure shown in Formula III:

[0040]

[0041] Polyvinyl pyrrolidone (PVP) has good water solubility. The present invention uses polyvinyl pyrrolidone as a repeating unit of a polyionic liquid to significantly improve the solubility and viscosity of the polymer. In addition, PVP has very low toxicity, good physiological compatibility, and is inexpensive. At the same time, it contains active nitrogen elements, making it easier to generate a tribochemical reaction film. Dimethylaminoethyl methacrylate in the cation is used to provide a basic tertiary amine functional group for the preparation of a proton-type polyionic liquid. In addition, the structure of dimethylaminoethyl methacrylate also contains active nitrogen elements. The present invention uses a copolymer of N-vinyl pyrrolidone and dimethylaminoethyl methacrylate as a cation, and an alkyl carboxylate anion and / or dibutyl phosphate anion as an anion. The active nitrogen element in its molecular structure can undergo a tribochemical reaction with the interface of the friction pair that slides against each other to generate a tribochemical protective film, which can not only improve the friction reduction and anti-wear properties of the water-based lubricant, but also greatly improve its extreme pressure bearing performance. Alkyl carboxylate anions or dibutyl phosphate anions can be effectively adsorbed onto the interface of the metal friction pair to form a physical adsorption film, which can significantly improve the lubrication performance of the lubricant. Proton-type polyionic liquid aqueous solutions have high viscosity and excellent film-forming ability on the friction surface. The synergistic effect of physical adsorption film, viscoelastic liquid film, and tribochemical reaction film effectively improves the friction reduction, anti-wear and load-bearing properties of water-based lubricants.

[0042] The present invention provides a method for preparing the above-mentioned proton-type polyionic liquid, comprising the following steps:

[0043] Dimethylaminoethyl methacrylate, an anion raw material and a solvent are mixed to perform a proton exchange reaction to obtain a proton exchange reaction solution; the anion raw material is an alkyl carboxylic acid and / or dibutyl phosphate;

[0044] The proton exchange reaction liquid, N-vinyl pyrrolidone and an initiator are mixed and polymerized to obtain a proton-type polyionic liquid.

[0045] Unless otherwise specified, the raw materials used in the present invention are all commercially available.

[0046] The present invention comprises mixing dimethylaminoethyl methacrylate, an anion source, and a solvent to perform a proton exchange reaction to obtain a proton exchange reaction solution. In the present invention, the anion source is an alkyl carboxylic acid and / or dibutyl phosphate. In the present invention, the alkyl carboxylic acid is preferably one or more of acetic acid, butyric acid, hexanoic acid, octanoic acid, and lauric acid.

[0047] In the present invention, the molar ratio of dimethylaminoethyl methacrylate to the anion raw material is preferably 1 to 2:1, more preferably 1.5:1.

[0048] In the present invention, the solvent is preferably water, a water-ethylene glycol mixture or ethylene glycol. The present invention has no special requirements for the volume ratio of water to ethylene glycol in the water-ethylene glycol mixture. In the present invention, the volume ratio of the amount of dimethylaminoethyl methacrylate to the solvent is preferably 0.05 mol:30 to 150 g, preferably 0.05 mol:60 g, specifically preferably 0.05 mol:30 g, 0.05 mol:40 g, 0.05 mol:50 g, 0.05 mol:60 g, 0.05 mol:70 g, 0.05 mol:80 g, 0.05 mol:90 g, 0.05 mol:100 g, 0.05 mol:110 g, 0.05 mol:120 g, 0.05 mol:130 g, 0.05 mol:140 g or 0.05 mol:150 g.

[0049] In the present invention, the temperature of the proton exchange reaction is preferably room temperature, and the time is 10 to 180 min, preferably 20 to 120 min, and more preferably 30 min.

[0050] After obtaining the proton exchange reaction solution, the present invention mixes the proton exchange reaction solution, N-vinyl pyrrolidone, and an initiator to carry out a polymerization reaction to obtain a protic polyionic liquid. In the present invention, the molar ratio of N-vinyl pyrrolidone to dimethylaminoethyl methacrylate is preferably 5:1 to 1:5, more preferably 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, or 1:5.

[0051] In the present invention, the initiator preferably includes one or more of ammonium persulfate, potassium persulfate and sodium persulfate; the mass of the initiator is preferably 0.003-1% of the total mass of dimethylaminoethyl methacrylate and the anion raw material, more preferably 0.01-0.1%, specifically preferably 0.003%, 0.005%, 0.008%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95% or 1%.

[0052] After the proton exchange reaction solution, N-vinyl pyrrolidone and initiator are mixed, the mixture is preferably deoxygenated. In the present invention, the deoxygenation is preferably performed by bubbling deoxygenation, and the deoxygenation time is preferably 20 to 120 minutes, more preferably 30 minutes.

[0053] In the present invention, the polymerization reaction temperature is preferably 50-90°C, more preferably 60-80°C; the polymerization time is preferably 1-36 hours, more preferably 5-30 hours, further preferably 10-25 hours, and further preferably 15-20 hours. In the present invention, the polymerization reaction is preferably carried out under stirring.

[0054] In the present invention, after the polymerization reaction, the solvent is preferably removed to obtain a protic polyionic liquid. Alternatively, the present invention uses a water-based lubricating liquid as the solvent. After the polymerization reaction, the solvent is not removed, and the protic polyionic liquid is obtained in situ in the water-based lubricating liquid.

[0055] The present invention provides the use of the above-mentioned protic polyionic liquid as a water-based viscosity-enhancing lubricant additive. In the present invention, the water-based lubricant preferably comprises one or more of water, a water-ethylene glycol mixture, a water-glycerol mixture, or a water-ethylene glycol-glycerol mixture. In the present invention, the mass ratio of water to the other components in the water-ethylene glycol mixture, the water-glycerol mixture, and the water-ethylene glycol-glycerol mixture is independently preferably 0.5:1 to 2:1, more preferably 0.8:1 to 1.5:1, and even more preferably 1:1.

[0056] In the present invention, the amount of the protic polyionic liquid added to the water-based lubricating fluid is preferably 0.1-40 wt%, more preferably 0.5-30 wt%, more preferably 1-20 wt%, and even more preferably 5-15 wt%.

[0057] The present invention provides a water-based lubricant product comprising a water-based base lubricating fluid and the aforementioned protic polyionic liquid. In the present invention, the water-based base lubricating fluid preferably comprises one or more of water, a water-ethylene glycol mixture, a water-glycerol mixture, or a water-ethylene glycol-glycerol mixture. In the present invention, the mass ratio of water to the other components in the water-ethylene glycol mixture, the water-glycerol mixture, and the water-ethylene glycol-glycerol mixture is independently preferably 0.5:1 to 2:1, more preferably 1:1.

[0058] In the present invention, the mass concentration of the protic polyionic liquid in the water-based lubricant product is preferably 0.1-40 wt%, more preferably 0.5-30 wt%, more preferably 1-20 wt%, and further preferably 5-15 wt%.

[0059] The proton-type polyionic liquid provided by the present invention, its preparation method and its application as a water-based viscosity-increasing lubricating additive are described in detail below with reference to the examples, but they should not be construed as limiting the scope of protection of the present invention.

[0060] Example 1

[0061] Synthesis of protic polyionic liquids:

[0062] 7.8695 g (0.05 mol) of dimethylaminoethyl methacrylate and 7.2105 g (0.05 mol) of n-octanoic acid were dissolved in a 250 mL three-necked flask containing 60 g of deionized water and proton exchange was performed. After 0.5 h, 2.7785 g (0.025 mol) of N-vinyl pyrrolidone and 0.04 g of initiator ammonium persulfate were added to the reaction flask and dissolved. Deoxygenation was bubbling for 30 min, and the system was placed in a 70°C oil bath with continuous mechanical stirring and heated for 8 h. After the reaction, the solvent was removed and the mixture was dried under vacuum to obtain the additive PNM-CA1.

[0063] The lubricating performance of the synthesized polyionic liquid as a water lubricant additive was evaluated using an SRV-V vibratory tribometer manufactured by Optimol, Germany. Water or water-ethylene glycol (1:1 mass ratio) was used as a control, and the polyionic liquid additive concentration was 5 wt%. The tribological tests were conducted under the following conditions: a load of 100 N, a temperature of 25°C, a frequency of 25 Hz, an amplitude of 1 mm, and a test time of 30 min. The upper test ball was a 10 mm Φ AISI 52100 steel ball. In the steel / steel friction pair, the lower test specimen was a 24 mm Φ, 7.9 mm thick AISI 52100 steel block with a hardness of 700-750 HV. The wear volume of the lower test specimen was measured using a MicroXAM-800 non-contact three-dimensional surface profilometer. The average friction coefficient and average wear volume of the different base lubricants and the base lubricant containing the polyionic liquid lubricant additive are shown in Table 1.

[0064] Table 1 Average friction coefficient and average wear volume of PNM-CA1 at a concentration of 5 wt% in different base lubricants

[0065] Base lubricant Average friction coefficient <![CDATA[Average wear volume (×10 -5 / mm 3 )]]> water 0.328 322.5 Water+5%PNM-CA1 0.075 28.5 Water-ethylene glycol 0.191 63.3 Water-ethylene glycol + 5% PNM-CA1 0.072 19.7

[0066] Example 2

[0067] Synthesis of protic polyionic liquids:

[0068] 7.8695 g (0.05 mol) of dimethylaminoethyl methacrylate and 7.2105 g (0.05 mol) of n-octanoic acid were dissolved in a 250 mL three-necked flask containing 60 g of deionized water and proton exchange was performed. After 0.5 h, 5.557 g (0.05 mol) of N-vinyl pyrrolidone and 0.04 g of potassium persulfate (initiator) were added to the reaction flask and dissolved. The mixture was deoxygenated by bubbling for 30 min. The system was then placed in a 70°C oil bath with continuous mechanical stirring and heated for 8 h. After the reaction, the solvent was removed and the mixture was dried under vacuum to obtain the additive PNM-CA2.

[0069] PNM-CA2 was dissolved in water or a water-ethylene glycol (mass ratio 1:1) solution to prepare a solution with a concentration of 5 wt%. The tribological properties of the obtained PNM-CA2 in the base lubricating fluid were evaluated according to the method in Example 1. The test conditions were the same as in Example 1. The test results are shown in Table 2.

[0070] Table 2 Average friction coefficient and average wear volume of PNM-CA2 at a concentration of 5 wt% in different base lubricants

[0071] Base lubricant Average friction coefficient <![CDATA[Average wear volume (×10 -5 / mm 3 )]]> water 0.328 322.5 Water + 5% PNM-CA2 0.082 38.5 Water-ethylene glycol 0.191 63.3 Water-ethylene glycol + 5% PNM-CA2 0.079 23.7

[0072] Example 3

[0073] Synthesis of protic polyionic liquids:

[0074] 7.8695 g (0.05 mol) of dimethylaminoethyl methacrylate and 5.8079 g (0.05 mol) of n-hexanoic acid were dissolved in a 250 mL three-necked flask containing 60 g of deionized water and proton exchange was performed. After 0.5 h, 2.7785 g (0.025 mol) of N-vinyl pyrrolidone and 0.04 g of initiator ammonium persulfate were added to the reaction flask and dissolved. Deoxygenation was bubbling for 30 min, and the system was placed in a 70°C oil bath with continuous mechanical stirring and heated for 8 h. After the reaction, the solvent was removed and the mixture was dried under vacuum to obtain the additive PNM-HA.

[0075] PNM-HA was dissolved in water or a water-ethylene glycol (mass ratio 1:1) solution to prepare a solution with a concentration of 5 wt%. The tribological properties of the obtained PNM-HA in the base lubricating fluid were evaluated according to the method in Example 1. The test conditions were the same as in Example 1. The test results are shown in Table 3.

[0076] Table 3 Average friction coefficient and average wear volume of PNM-HA at a concentration of 5 wt% in different base lubricants

[0077] Base lubricant Average friction coefficient <![CDATA[Average wear volume (×10 -5 / mm 3 )]]> water 0.328 322.5 Water + 5% PNM-HA 0.088 43.1 Water-ethylene glycol 0.191 63.3 Water-ethylene glycol + 5% PNM-HA 0.082 26.9

[0078] Example 4

[0079] Synthesis of protic polyionic liquids:

[0080] 7.8695 g (0.05 mol) of dimethylaminoethyl methacrylate and 4.4055 g (0.05 mol) of n-butyric acid were dissolved in a 250 mL three-necked flask containing 60 g of deionized water and proton exchange was performed. After 0.5 h, 2.7785 g (0.025 mol) of N-vinyl pyrrolidone and 0.04 g of the initiator sodium persulfate were added to the reaction flask and dissolved. Deoxygenation was bubbling for 30 min, and the system was placed in a 70°C oil bath with continuous mechanical stirring and heated for 8 h. After the reaction, the solvent was removed and the mixture was dried under vacuum to obtain the additive PNM-BA.

[0081] PNM-BA was dissolved in water or a water-ethylene glycol (mass ratio 1:1) solution to prepare a solution with a concentration of 5 wt%. The tribological properties of the obtained PNM-BA in the base lubricating fluid were evaluated according to the method in Example 1. The test conditions were the same as in Example 1. The test results are shown in Table 4.

[0082] Table 4 Average friction coefficient and average wear volume of PNM-BA at a concentration of 5 wt% in different base lubricants

[0083] Base lubricant Average friction coefficient <![CDATA[Average wear volume (×10 -5 / mm 3 )]]> water 0.328 322.5 Water+5%PNM-BA 0.128 80.1 Water-ethylene glycol 0.191 63.3 Water-ethylene glycol + 5% PNM-BA 0.115 31.9

[0084] Example 5

[0085] Synthesis of a protic polyionic liquid: 7.8695 g (0.05 mol) of dimethylaminoethyl methacrylate and 10.5105 g (0.05 mol) of dibutyl phosphate were dissolved in a 250 mL three-necked flask containing 60 g of deionized water and proton exchange was performed. After 0.5 h, 2.7785 g (0.025 mol) of N-vinylpyrrolidone and 0.04 g of ammonium persulfate (initiator) were added to the reaction flask and dissolved. Deoxygenation was bubbling for 30 min, and the system was heated in a 70°C oil bath with continuous mechanical stirring for 8 h. After the reaction, the solvent was removed and the system was dried under vacuum to obtain the additive PNM-DBP.

[0086] PNM-DBP was dissolved in water or a water-ethylene glycol (mass ratio 1:1) solution to prepare a solution with a concentration of 5 wt%. The tribological properties of the obtained PNM-DBP in the base lubricating fluid were evaluated according to the method in Example 1. The test conditions were the same as in Example 1. The test results are shown in Table 5.

[0087] Table 5 Average friction coefficient and average wear volume of PNM-DBP at a concentration of 5 wt% in different water-ethylene glycol based lubricants

[0088] Base lubricant Average friction coefficient <![CDATA[Average wear volume (×10 -5 / mm 3 )]]> water 0.328 322.5 Water + 5% PNM-DBP 0.120 70.2 Water-ethylene glycol 0.191 63.3 Water-ethylene glycol + 5% PNM-DBP 0.112 28.9

[0089] Example 6

[0090] Synthesis of a protic polyionic liquid: 7.8695 g (0.05 mol) of dimethylaminoethyl methacrylate, 5.7685 g (0.04 mol) of n-octanoic acid, and 2.1021 g (0.01 mol) of dibutyl phosphate were dissolved in a 250 mL three-necked flask containing 60 g of deionized water and proton exchange was performed. After 0.5 h, 2.7785 g (0.025 mol) of N-vinyl pyrrolidone and 0.04 g of ammonium persulfate (initiator) were added to the reaction flask and dissolved. Deoxygenation was bubbling for 30 min, and the system was heated in a 70°C oil bath with continuous mechanical stirring for 8 h. After the reaction, the solvent was removed and the system was dried under vacuum to obtain the additive PNM-CP.

[0091] PNM-CP was dissolved in water or a water-ethylene glycol (mass ratio 1:1) solution to prepare a solution with a concentration of 5 wt%. The tribological properties of the obtained PNM-CP in the base lubricating fluid were evaluated according to the method in Example 1. The test conditions were the same as in Example 1. The test results are shown in Table 6.

[0092] Table 6 Average friction coefficient and average wear volume of PNM-CP at a concentration of 5 wt% in different base lubricants

[0093] Base lubricant Average friction coefficient <![CDATA[Average wear volume (×10 -5 / mm 3 )]]> water 0.328 322.5 Water + 5% PNM-CP 0.077 40.5 Water-ethylene glycol 0.191 63.3 Water-ethylene glycol + 5% PNM-CP 0.075 24.6

[0094] Example 7

[0095] Synthesis of protic polyionic liquids:

[0096] 7.8695 g (0.05 mol) of dimethylaminoethyl methacrylate and 10.0159 g (0.05 mol) of lauric acid were added to a 250 mL three-necked flask containing 60 g of a water-ethylene glycol mixed solution (mass ratio 1:1) to dissolve and perform proton exchange. After 0.5 h, 2.7785 g (0.025 mol) of N-vinyl pyrrolidone and 0.04 g of initiator ammonium persulfate were added to the reaction flask to dissolve, and bubbling deoxygenation was performed for 30 min. The system was placed in an 80 ° C oil bath with continuous mechanical stirring and heating for 6 h to obtain the lubricating liquid water-ethylene glycol + PNM-LA by in situ reaction.

[0097] The water-ethylene glycol + PNM-LA obtained by the reaction was diluted with a water-ethylene glycol solution to an additive solution with a solid content of 5 wt%. The tribological properties of the obtained water-ethylene glycol + PNM-LA in a base lubricating fluid were evaluated according to the method in Example 1. The test conditions were the same as in Example 1. The test results are shown in Table 7:

[0098] Table 7 Average friction coefficient and average wear volume of PNM-LA water-ethylene glycol solution with a concentration of 5 wt%

[0099] Base lubricant Average friction coefficient <![CDATA[Average wear volume (×10 -5 / mm 3 )]]> Water-ethylene glycol 0.191 63.3 Water-ethylene glycol + 5% PNM-LA 0.068 17.9

[0100] Example 8

[0101] Synthesis of proton-type polyionic liquid: 7.8695g (0.05mol) of dimethylaminoethyl methacrylate and 7.2105g (0.05mol) of n-octanoic acid were added to a 250mL three-necked flask containing 60g of a water-ethylene glycol (mass ratio 1:1) mixed solution to dissolve and perform proton exchange. After 0.5h, 2.7785g (0.025mol) of N-vinylpyrrolidone and 0.04g of initiator ammonium persulfate were added to the reaction flask to dissolve, and bubbling deoxygenation was performed for 30min. The system was placed in an 80℃ oil bath with continuous mechanical stirring and heating for 6h to obtain the lubricating liquid water-ethylene glycol + PNM-CA3 by in-situ reaction.

[0102] The water-ethylene glycol + PNM-CA3 obtained by the reaction was diluted with a water-ethylene glycol solution to an additive solution with a solid content of 5 wt%. The tribological properties of the obtained water-ethylene glycol + PNM-CA3 in a base lubricating fluid were evaluated according to the method in Example 1. The test conditions were the same as in Example 1. The test results are shown in Table 8.

[0103] Table 8 Average friction coefficient and average wear volume of PNM-CA3 water-ethylene glycol solution with a concentration of 5wt%

[0104] Base lubricant Average friction coefficient <![CDATA[Average wear volume (×10 -5 / mm 3 )]]> Water-ethylene glycol 0.191 63.3 Water-ethylene glycol + 5% PNM-CA3 0.071 19.9

[0105] Example 9

[0106] Synthesis of protic polyionic liquids:

[0107] 7.8695 g (0.05 mol) of dimethylaminoethyl methacrylate and 7.2105 g (0.05 mol) of n-octanoic acid were added to a 250 mL three-necked flask containing 60 g of ethylene glycol to dissolve and perform proton exchange. After 0.5 h, 2.7785 g (0.025 mol) of N-vinyl pyrrolidone and 0.04 g of initiator sodium persulfate were added to the reaction flask to dissolve, and bubbling deoxygenation was performed for 30 min. The system was placed in an 80 ° C oil bath with continuous mechanical stirring and heating for 6 h to obtain an ethylene glycol solution of the additive PNM-CA4 by in situ reaction.

[0108] The ethylene glycol solution of PNM-CA4 obtained by the reaction was diluted with water to a water-ethylene glycol (mass ratio 1:1) solution with a solid content of 5 wt%. The tribological properties of the resulting water-ethylene glycol + PNM-CA4 in the base lubricating fluid were evaluated according to the method in Example 1. The test conditions were the same as in Example 1, and the test results are shown in Table 9.

[0109] Table 9 Average friction coefficient and average wear volume of PNM-CA4 water-ethylene glycol solution with a concentration of 5wt%

[0110] Base lubricant Average friction coefficient <![CDATA[Average wear volume (×10 -5 / mm 3 )]]> Water-ethylene glycol 0.191 63.3 Water-ethylene glycol + 5% PNM-CA4 0.072 20.1

[0111] Test Example 1 Anti-corrosion Performance Test

[0112] The polyionic liquids prepared in Examples 1-9 were formulated into base lubricant solutions with a concentration of 1 wt%. Corrosion resistance was tested according to GB6144-85, with water and water-ethylene glycol (mass ratio 1:1) serving as controls. Cast iron sheets of the same specifications were immersed in water, water-ethylene glycol, and the additive solutions prepared in Examples 1-9 at 55±2°C for 24 hours. After 24 hours, the sheets were ultrasonically cleaned in acetone and dried with high-velocity air. The surfaces of the sheets were observed under an optical microscope. The corrosion conditions of the sheets in the different aqueous solutions were analyzed and compared with a corrosion color chart to determine the corrosion grade. The results are shown in Table 10.

[0113] Table 10 Corrosion resistance test results of ionic liquids obtained in Examples 1 to 9

[0114] sample Corrosion level water D Water-ethylene glycol D Water+5%PNM-CA1 A Water-ethylene glycol + 5% PNM-CA1 A Water + 5% PNM-CA2 A Water-ethylene glycol + 5% PNM-CA2 A Water + 5% PNM-HA B Water-ethylene glycol + 5% PNM-HA B Water+5%PNM-BA B Water-ethylene glycol + 5% PNM-BA B Water + 5% PNM-DBP B Water-ethylene glycol + 5% PNM-DBP B Water + 5% PNM-CP A Water-ethylene glycol + 5% PNM-CP A Water-ethylene glycol + 5% PNM-LA A Water-ethylene glycol + 5% PNM-CA3 A Water-ethylene glycol + 5% PNM-CA4 A

[0115] In Table 10, A means no rust and bright as new; B means no rust but slightly tarnished; C means light rust and slightly tarnished; D means heavy rust or serious tarnishing.

[0116] According to the experimental results in Table 10, it can be seen that the proton-type polyionic liquid provided by the present invention can significantly improve the anti-corrosion performance of the water-based lubricating fluid when used as an additive for the water-based lubricating fluid.

[0117] Test Example 2 Viscosity Test

[0118] The polyionic liquids prepared in Examples 1 to 9 were formulated into aqueous solutions or water-ethylene glycol solutions (mass ratio 1:1) with a concentration of 5 wt%. The kinematic viscosities of deionized water, water-ethylene glycol, and the additive solutions prepared in Examples 1 to 9 at 25°C and 40°C were measured using a Pinault viscometer. The experimental results are shown in Table 11.

[0119] Table 11 Kinematic viscosity of deionized water and 5 wt% polyionic liquid solution at 25°C and 40°C

[0120]

[0121] According to the experimental results in Table 11, it can be seen that the proton-type polyionic liquid prepared in the present invention, when used as a water-based lubricant additive, can significantly increase the kinematic viscosity of the water-based lubricant and enhance the film-forming ability of the water-based lubricant at the friction interface.

[0122] The above examples and test cases demonstrate that the proton-containing polyionic liquid lubricant additive provided by the present invention can significantly improve the corrosion resistance, viscosity, and friction and anti-wear properties of water-based lubricants. Furthermore, the proton-containing polyionic liquid lubricant additive provided by the present invention has a simple, environmentally friendly, pollution-free synthesis process and low synthesis cost, and thus has broad application prospects as a water-based lubricant additive.

[0123] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A proton-type polyionic liquid comprising cations and anions, characterized in that: The cation is a copolymer of N-vinyl pyrrolidone and dimethylaminoethyl methacrylate, and the anion is an alkyl carboxylate anion and / or a dibutyl phosphate anion; The cation has a structure shown in Formula I: In formula I, m:n = 5:1 to 1:

5.

2. The proton-type polyionic liquid according to claim 1, characterized in that The alkyl carboxylate anion has a structure shown in Formula II: In Formula II, x is any integer from 1 to 11.

3. The proton-type polyionic liquid according to claim 1 or 2, characterized in that The alkyl carboxylate anion includes one or more of acetate anion, butyrate anion, hexanoate anion, octanoate anion and laurate anion.

4. The proton-type polyionic liquid according to claim 1, characterized in that The dibutyl phosphate anion has a structure shown in Formula III:

5. The method for preparing the protic polyionic liquid according to any one of claims 1 to 4, comprising the following steps: Dimethylaminoethyl methacrylate, an anion raw material and a solvent are mixed to perform a proton exchange reaction to obtain a proton exchange reaction solution; the anion raw material is an alkyl carboxylic acid and / or dibutyl phosphate; The proton exchange reaction liquid, N-vinyl pyrrolidone and an initiator are mixed and polymerized to obtain a proton-type polyionic liquid.

6. The preparation method according to claim 5, characterized in that The molar ratio of dimethylaminoethyl methacrylate to anion raw material is 1 to 2:1; The molar ratio of N-vinyl pyrrolidone to dimethylaminoethyl methacrylate is 5:1 to 1:

5.

7. The preparation method according to claim 5 or 6, characterized in that: The initiator includes one or more of ammonium persulfate, potassium persulfate and sodium persulfate; The mass of the initiator is 0.003-1% of the total mass of dimethylaminoethyl methacrylate and the anion raw material.

8. The preparation method according to claim 5, characterized in that The polymerization reaction temperature is 50-90° C., and the reaction time is 1-36 hours.

9. Use of the proton-type polyionic liquid according to any one of claims 1 to 4 or the proton-type polyionic liquid prepared by the preparation method according to any one of claims 5 to 8 as a water-based viscosity-increasing lubricating additive.

10. A water-based lubricant product comprising a water-based base lubricating fluid and the proton-type polyionic liquid according to any one of claims 1 to 4 or the proton-type polyionic liquid prepared by the preparation method according to any one of claims 5 to 8; The water-based lubricating fluid includes one or more of water, water-ethylene glycol mixture, water-glycerin mixture, and water-ethylene glycol-glycerin mixture; The mass concentration of the proton-type polyionic liquid in the water-based lubricant product is 0.1-40 wt %.

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