Wear-resistant graphene lubricating oil additive, preparation method thereof and synthetic ester lubricating oil

Abstract

The invention belongs to the technical field of lubricating oil, and particularly relates to an anti-wear graphene lubricating oil additive, a preparation method thereof and synthetic ester lubricating oil. The preparation method comprises the following steps: dropwise adding an acrylic acid-2-hydroxyethyl ester solution into a 1, 6-hexamethylene diisocyanate solution, and carrying out addition esterification reaction to obtain a semi-terminated compound; and mixing the semi-terminated compound with a graphene dispersion liquid, and carrying out a grafting reaction to obtain the anti-wear graphene lubricating oil additive. According to the invention, chemical grafting is carried out on graphene and a semi-terminated compound, so that the problem of poor compatibility between graphene and synthetic ester base oil due to the fact that the surface of graphene is rich in hydrophilic groups is solved, and the problems of non-uniform dispersion and particle aggregation when graphene is added into the synthetic ester base oil are effectively avoided; therefore, the graphene is ensured to fully exert excellent performance in synthetic ester base oil.

Description

Technical Field

[0001] The invention relates to the technical field of lubricating oils, and in particular to an anti-wear graphene lubricating oil additive and a preparation method thereof, and a synthetic ester lubricating oil. Background Art

[0002] As a synthetic ester base oil, trimethylolpropane oleate has excellent low-temperature fluidity, viscosity-temperature performance, lubrication performance and biodegradability. It also has the characteristics of high viscosity index, good flame retardancy, hydrolysis stability, high flash point and low volatility. As the base oil of No. 46 synthetic ester type flame-resistant hydraulic oil, trimethylolpropane oleate is also widely used in environmentally friendly hydraulic oils, chain saw oils, water yacht engine oils, metalworking fluids and textile leather auxiliaries. However, despite the outstanding lubrication performance of trimethylolpropane oleate, under harsh working conditions, the anti-wear performance of lubricants is extremely high, and it is usually necessary to add phosphorus-containing anti-wear agents such as ammonium phosphate salts to enhance its performance. These additives are not only complex in preparation process and costly, but also put pressure on the environment.

[0003] The emergence of nanocarbon materials has provided many possibilities in the field of lubricant additives. The application of nanocarbon materials in lubricants can significantly reduce friction, resist wear and achieve excellent compression performance. Among them, graphene, as a new type of nanocarbon material, perfectly matches the basic properties of solid lubricant additives with its light weight, high strength, and excellent electrical and thermal conductivity. However, compared with graphene oxide prepared by the "top-down" method, graphene oxide (GO) contains more hydrophilic groups, such as hydroxyl (-OH) and carboxyl (-COOH), which makes graphene oxide less compatible with synthetic ester base oils. When graphene oxide is added to synthetic ester base oils, there are often problems with poor dispersion stability and easy agglomeration of graphene oxide particles, which limits the full performance of graphene oxide in synthetic ester base oils. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides an anti-wear graphene lubricant additive, a preparation method thereof, and a synthetic ester lubricant. The present invention uses 1,6-hexamethylene diisocyanate and 2-hydroxyethyl acrylate as raw materials, and synthesizes a semi-capped compound through an addition esterification reaction; the semi-capped compound is mixed with a dispersion of graphene and then subjected to a grafting reaction to obtain an anti-wear graphene lubricant additive. The anti-wear graphene lubricant additive obtained by the preparation method of the present invention realizes the chemical grafting of the semi-capped compound generated by 1,6-hexamethylene diisocyanate and 2-hydroxyethyl acrylate with graphene, overcoming the problem that graphene has poor compatibility with synthetic ester base oils due to the rich hydrophilic groups on its surface, and is unevenly dispersed and easily agglomerated, so that the anti-wear graphene lubricant additive can give full play to its excellent performance in synthetic ester base oils.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] The first object of the present invention is to provide a method for preparing an anti-wear graphene lubricant additive, comprising the following steps:

[0007] A 2-hydroxyethyl acrylate solution is added dropwise to a 1,6-hexamethylene diisocyanate solution to carry out an addition esterification reaction to obtain a semi-blocked compound. Semi-blocking means that 2-hydroxyethyl acrylate acts as a blocking agent to react with -NCO at one end of 1,6-hexamethylene diisocyanate to form a stable amide group as the terminal group; the isocyanate group at the other end can still undergo a grafting reaction; if 2-hydroxyethyl acrylate blocks both ends of 1,6-hexamethylene diisocyanate at the same time to obtain a fully blocked solid product, the next grafting reaction cannot be carried out.

[0008] The semi-capped compound is mixed with a dispersion of graphene and then subjected to a grafting reaction. In the grafting reaction, -NCO on the semi-capped compound reacts with -OH on the graphene to form carbamate, and reacts with -COOH on the graphene to form amide, thereby obtaining an anti-wear graphene lubricant additive.

[0009] Among them, in the anti-wear graphene lubricant additive, the mass ratio of graphene, 2-hydroxyethyl acrylate, and 1,6-hexamethylene diisocyanate is 1:10~150:10~150.

[0010] Preferably, the conditions for the addition esterification reaction are: slowly adding dropwise at -5°C to 5°C and reacting for 8h to 12h.

[0011] Preferably, the grafting reaction conditions are: first react at -5°C to 5°C for 0.5h to 1h, then react at room temperature for 0.5h to 1h, and finally continue to react at 100°C to 120°C for 12h to 24h.

[0012] Preferably, the solvents in the 2-hydroxyethyl acrylate solution, the 1,6-hexamethylene diisocyanate solution and the graphene dispersion are all anhydrous N,N-dimethylformamide.

[0013] Preferably, the mass volume ratio of 2-hydroxyethyl acrylate to anhydrous N,N-dimethylformamide is 1 g to 2.5 g: 10 mL. Excessive 2-hydroxyethyl acrylate tends to generate a viscous solid, while a small amount has a poor modification effect on graphene.

[0014] Preferably, the mass volume ratio of 1,6-hexamethylene diisocyanate to anhydrous N,N-dimethylformamide is 3g-7.5g:40mL; excessive 1,6-hexamethylene diisocyanate tends to generate viscous solids, while a small amount has a poor modification effect on graphene.

[0015] Preferably, the dispersion of graphene is prepared according to the following method: under the protection of inert gas, graphene is ultrasonically dispersed in anhydrous N,N-dimethylformamide; and the mass volume ratio of graphene to anhydrous N,N-dimethylformamide is 3mg-5mg:1mL; graphene has the best diffusion performance in anhydrous N,N-dimethylformamide, and other diffusion solvents such as ethanol are easy to deteriorate 1,6-hexamethylene diisocyanate. In addition, the reaction solvent must be an anhydrous solvent, otherwise the water in the solvent will react with 2-hydroxyethyl acrylate and 1,6-hexamethylene diisocyanate for esterification.

[0016] Preferably, the graphene is selected from single-layer graphene or graphene oxide; graphene oxide contains a large number of hydroxyl groups and carboxyl groups; single-layer graphene is obtained by applying a traditional reduction method, that is, graphene oxide is reduced to obtain single-layer graphene, but the reduction method cannot completely remove the functional groups on the surface of graphene oxide, and a small number of oxygen-containing groups still remain.

[0017] Preferably, the particle size of the single-layer graphene is 5 μm to 20 μm, and the specific surface area of ​​the graphene is 50 cm 2 / g~300cm 2 / g.

[0018] The second object of the present invention is to provide an anti-wear graphene lubricating oil additive prepared by the above preparation method.

[0019] The third object of the present invention is to provide a synthetic ester lubricating oil.

[0020] Preferably, the synthetic ester lubricant is prepared by adding an anti-wear graphene lubricant additive to a synthetic ester base oil; wherein the mass ratio of the anti-wear graphene lubricant additive to the synthetic ester base oil is 1:10000-20000.

[0021] Preferably, the synthetic ester base oil is selected from trimethylolpropane oleate base oil, pentaerythritol oleate base oil or poly-alpha-olefin base oil.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention provides a method for preparing an anti-wear graphene lubricant additive. A 2-hydroxyethyl acrylate solution is added dropwise to a 1,6-hexamethylene diisocyanate solution to perform an addition esterification reaction to obtain a semi-blocked compound; the mass ratio of 1,6-hexamethylene diisocyanate to 2-hydroxyethyl acrylate is 1:0.8-1; after the semi-blocked compound is mixed with a dispersion of graphene, a grafting reaction is performed, in which -NCO on the semi-blocked compound reacts with -OH on the graphene to form carbamate, and reacts with -COOH on the graphene to form amide, to obtain an anti-wear graphene lubricant additive; the mass ratio of the semi-blocked compound to the dispersion of graphene is 40-50:1.

[0024] The traditional reaction between hydroxyethyl ester compounds and diisocyanate compounds is carried out under the catalysis of dibutyltin dilaurate, which will produce a large amount of fully blocked diamide products, resulting in increased costs and reduced yields. In addition, the grafting rate of fully blocked diamide products with the hydroxyl and carboxyl groups on the graphene surface is low, and the modification effect is poor. Figure 2 and Figure 3 As shown. Compared with the prior art, the present invention successfully generates a semi-blocked compound using 1,6-hexamethylene diisocyanate and 2-hydroxyethyl acrylate through an addition esterification reaction under low temperature conditions without using a catalyst. This method not only retains another isocyanate group, which provides the possibility for the subsequent grafting reaction with graphene, but also effectively avoids the problem of increased friction performance of the anti-wear graphene lubricant additive due to the generation of fully blocked by-products in the traditional method. Then, by grafting the semi-blocked compound onto the graphene surface, an anti-wear graphene lubricant additive was successfully prepared, overcoming the problem that graphene has poor compatibility with synthetic ester base oils due to the rich hydrophilic groups on the surface, uneven dispersion and easy agglomeration, so that the anti-wear graphene lubricant additive has excellent lubrication properties.

[0025] 2. The wear-resistant graphene lubricant additive prepared by the present invention has a molecule chain consisting of more than 18 atoms, and the molecular chain contains abundant amide groups and carbamate structures. This characteristic significantly improves the lubrication performance of the wear-resistant graphene lubricant additive. Among them, the amide group can effectively combine with the metal surface due to its polar interaction mechanism, forming a stable hydrogen bond or tightly adsorbing on the metal surface, thereby constructing a protective molecular film. The presence of this molecular film greatly reduces the direct contact between metal surfaces, thereby effectively reducing the friction coefficient and the degree of wear. At the same time, the NH group in the amide molecule can weaken the interaction force of the ionic bond on the friction interface containing hydrogen bonds, further reducing friction and wear.

[0026] In addition, since the graphene layers have good sliding properties, and the long-chain molecules of the anti-wear graphene lubricant additive can further expand the interlayer spacing between the graphene layers, thereby effectively reducing friction, the anti-wear graphene lubricant additive can be better dispersed in trimethylolpropane oleate, thereby significantly enhancing the compatibility of the anti-wear graphene lubricant additive and trimethylolpropane oleate.

[0027] 3. The preparation process of the anti-wear graphene lubricant additive provided by the present invention is simple and low-cost; at the same time, the present invention not only limits the grafted substrate to single-layer graphene, but also expands it to graphene oxide, all of which have achieved good results. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The present invention provides a technical roadmap for preparing the anti-wear graphene lubricant additive.

[0029] Figure 2 A technical roadmap for preparing anti-wear graphene lubricant additives using existing technologies.

[0030] Figure 3 This is a structural diagram of the byproducts produced by the prior art in preparing anti-wear graphene lubricant additives.

[0031] Figure 4 This is a diagram showing the diffusion effect of the anti-wear graphene lubricant additive prepared in Example 1 of the present invention in different solvents; wherein a is DMF, b is xylene, and c is methanol.

[0032] Figure 5 This is a diffusion diagram of the anti-wear graphene lubricant additive prepared in Example 1 of the present invention in petroleum ether.

[0033] Figure 6 3 is a diffusion diagram of a single-layer graphene and the anti-wear graphene lubricant additive prepared in Example 1 in trimethylolpropane oleate, wherein a is a diffusion diagram of graphene in trimethylolpropane oleate, a1 is standing still for 24 hours, and a2 is standing still for 48 hours; b is a diffusion diagram of the anti-wear graphene lubricant additive prepared in Example 1 of the present invention in trimethylolpropane oleate, wherein b1 is standing still for 24 hours, and b2 is standing still for 48 hours.

[0034] Figure 7] are infrared spectra of graphene oxide and the wear-resistant graphene lubricant additives prepared in Examples 2 to 20, wherein a is an infrared spectra of graphene oxide and the wear-resistant graphene lubricant additives prepared in Examples 2 to 4, b is an infrared spectra of graphene oxide and the wear-resistant graphene lubricant additives prepared in Examples 5 to 10, c is an infrared spectra of the wear-resistant graphene lubricant additives prepared in Examples 11 to 13, d is an infrared spectra of the wear-resistant graphene lubricant additives prepared in Examples 14 to 17, and e is an infrared spectra of the wear-resistant graphene lubricant additives prepared in Examples 18 to 20.

[0035] Figure 8 It is the X-ray diffraction pattern of graphene oxide and the anti-wear graphene lubricant additive prepared by Example 5 to Example 10.

[0036] Fig. 9 TEM images of graphene oxide and the anti-wear graphene lubricant additive prepared in Example 6, wherein a is the TEM image of graphene oxide, b is the TEM image of graphene oxide, c is the TEM image of the anti-wear graphene lubricant additive prepared in Example 6, and d is the TEM image of the anti-wear graphene lubricant additive prepared in Example 6.

[0037] Fig.10 It is an infrared spectrum of single-layer graphene and the anti-wear graphene lubricant additive prepared in Example 1 and Example 21 to Example 26.

[0038] Fig.11 It is the X-ray diffraction pattern of the single-layer graphene and the anti-wear graphene lubricant additive prepared in Example 1 and Example 21 to Example 26.

[0039] Fig.12 TEM images of single-layer graphene, embodiment 1, embodiment 23 and embodiment 26, wherein, Figure a and Figure b are TEM images of single-layer graphene, Figure c and Figure d are TEM images of single-layer graphene added with PVP, Figure e and Figure f are TEM images of the anti-wear graphene lubricant additive prepared in embodiment 1, Figure g and Figure h are TEM images of the anti-wear graphene lubricant additive prepared in embodiment 1 with PVP added, Figure i and Figure j are TEM images of the anti-wear graphene lubricant additive prepared in embodiment 23, and Figure k and Figure l are TEM images of the anti-wear graphene lubricant additive prepared in embodiment 26. DETAILED DESCRIPTION

[0040] The technical solution of the present invention will be clearly and completely described below in combination with the data in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods. Among them, 1,6-hexamethylene diisocyanate, i.e. HDI, was purchased from Shanghai Titan Technology Exploration Platform; 2-hydroxyethyl acrylate, i.e. HEA, was purchased from Shanghai Titan Technology Exploration Platform; single-layer graphene was purchased from Hunan Fengen New Materials Technology Co., Ltd.; graphene oxide, i.e. GO powder, was purchased from Hunan Fengen New Materials Technology Co., Ltd.

[0042] In the prior art, graphene, as a new type of carbon nanomaterial, has light weight, high strength, and excellent electrical and thermal conductivity, which perfectly matches the basic properties of solid lubricant additives. However, there are a large number of hydrophilic groups on the surface of graphene oxide, such as hydroxyl and carboxyl groups, which makes the compatibility of graphene oxide with synthetic ester base oils poor. When graphene oxide is added to synthetic ester base oils, problems such as uneven dispersion and particle agglomeration are prone to occur, which limits the full performance of graphene oxide in synthetic ester base oils.

[0043] In view of the defects of the prior art, the present invention provides a method for preparing an anti-wear graphene lubricant additive, comprising the following steps: dripping a 2-hydroxyethyl acrylate solution into a 1,6-hexamethylene diisocyanate solution to perform an addition esterification reaction to obtain a semi-capped compound; mixing the semi-capped compound with a dispersion of graphene and then performing a grafting reaction, wherein -NCO on the semi-capped compound reacts with -OH on the graphene to form carbamate, and reacts with -COOH on the graphene to form amide to obtain an anti-wear graphene lubricant additive; in the anti-wear graphene lubricant additive, the mass ratio of graphene, 2-hydroxyethyl acrylate and 1,6-hexamethylene diisocyanate is 1:10-150:10-150.

[0044] The present invention successfully generates a semi-capped compound by using 1,6-hexamethylene diisocyanate and 2-hydroxyethyl acrylate through addition polymerization reaction under low temperature conditions without using a catalyst; the other isocyanate group retained reacts with the hydroxyl group and carboxyl group on the surface of graphene to generate carbamate and amide groups, and the obtained anti-wear graphene lubricant additive overcomes the problem that graphene has poor compatibility with synthetic ester base oils and is unevenly dispersed and easy to agglomerate due to the rich hydrophilic groups on the surface. At the same time, the problem of increased friction performance of the anti-wear graphene lubricant additive due to the generation of fully capped by-products in the traditional method is effectively avoided.

[0045] In addition, the molecular chain of the anti-wear graphene lubricant additive obtained by the present invention contains abundant amide groups and carbamate structures, which significantly improves the lubrication performance of the anti-wear graphene lubricant additive.

[0046] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0047] Example 1

[0048] A method for preparing an anti-wear graphene lubricant additive, wherein the mass ratio of single-layer graphene: HDI: HEA is 1:50:50, and the technical roadmap is as follows Figure 1 As shown, the following steps are included:

[0049] S1. Under argon protection, 1.5 g of 1,6-hexamethylene diisocyanate was dissolved in 20 mL of anhydrous DMF, and the mixture was stirred thoroughly in an ice bath to obtain a 1,6-hexamethylene diisocyanate solution.

[0050] 1.5 g of 2-hydroxyethyl acrylate was dissolved in 10 mL of anhydrous DMF to obtain a 2-hydroxyethyl acrylate solution.

[0051] The 2-hydroxyethyl acrylic acid solution was slowly added dropwise to the 1,6-hexamethylene diisocyanate solution within 30 minutes, and the reaction was carried out at 0°C for 8 hours to obtain a semi-blocked compound.

[0052] S2. Under argon protection, 300 mg of single-layer graphene was added into 100 mL of anhydrous DMF and ultrasonically dispersed for 1 h to obtain a graphene dispersion.

[0053] The semi-capped compound was added to the graphene dispersion, first reacted at 0°C for 0.5h, then fully stirred at room temperature for 1h, and finally reacted at 100°C for 12h. After the reaction was completed, it was cooled to room temperature and washed repeatedly with anhydrous ethanol for 3 times; then the black solid was ground into powder and washed with ethyl acetate, then washed with anhydrous ethanol for 3 times, and finally vacuum dried at 50°C for 12h to obtain an anti-wear graphene lubricant additive, recorded as G-HDI-HEA.

[0054] On the basis of Example 1, the present invention replaces the single-layer graphene in Example 1 with graphene oxide powder, and uses GO powder, HDI, and HEA as substrates to prepare an anti-wear graphene lubricant additive. The specific scheme is shown in Table 1, Table 2, and Table 3.

[0055] Example 2

[0056] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method in Example 1, except that the single-layer graphene in Example 1 is replaced by graphene oxide, and the mass ratio of GO powder:HDI:HEA is replaced from 1:50:50 to 1:100:150 to obtain an anti-wear graphene lubricant additive, which is recorded as GO-HDI-HEA.

[0057] Example 3

[0058] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method of Example 2, except that the mass ratio of GO powder:HDI:HEA is replaced from 1:100:150 to 1:150:100 to obtain an anti-wear graphene lubricant additive, which is recorded as GO-HDI-HEA.

[0059] Example 4

[0060] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method of Example 2, except that the mass ratio of GO powder:HDI:HEA is replaced from 1:100:150 to 1:100:100 to obtain an anti-wear graphene lubricant additive, which is recorded as GO-HDI-HEA.

[0061] Example 5

[0062] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method of Example 2, except that the mass ratio of GO powder:HDI:HEA is replaced from 1:100:150 to 1:70:70 to obtain an anti-wear graphene lubricant additive, which is recorded as GO-HDI-HEA.

[0063] Example 6

[0064] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method in Example 1, except that the single-layer graphene in Example 1 is replaced with GO powder to obtain an anti-wear graphene lubricant additive, which is recorded as GO-HDI-HEA.

[0065] Example 7

[0066] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method of Example 2, except that the mass ratio of GO powder:HDI:HEA is replaced from 1:100:150 to 1:30:30 to obtain an anti-wear graphene lubricant additive, which is recorded as GO-HDI-HEA.

[0067] Example 8

[0068] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method of Example 2, except that the mass ratio of GO powder:HDI:HEA is replaced from 1:100:150 to 1:20:20 to obtain an anti-wear graphene lubricant additive, which is recorded as GO-HDI-HEA.

[0069] Example 9

[0070] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method of Example 2, except that the mass ratio of GO powder:HDI:HEA is replaced from 1:100:150 to 1:15:10 to obtain an anti-wear graphene lubricant additive, which is recorded as GO-HDI-HEA.

[0071] Example 10

[0072] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method of Example 2, except that the mass ratio of GO powder:HDI:HEA is replaced from 1:100:150 to 1:10:15 to obtain an anti-wear graphene lubricant additive, which is recorded as GO-HDI-HEA.

[0073] Embodiment 11

[0074] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method of Example 2, except that the mass ratio of GO powder:HDI:HEA is replaced from 1:100:150 to 1:70:60 to obtain an anti-wear graphene lubricant additive, which is recorded as GO-HDI-HEA.

[0075] Example 12

[0076] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method of Example 2, except that the mass ratio of GO powder:HDI:HEA is replaced from 1:100:150 to 1:70:50 to obtain an anti-wear graphene lubricant additive, which is recorded as GO-HDI-HEA.

[0077] Example 13

[0078] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method of Example 2, except that the mass ratio of GO powder:HDI:HEA is replaced from 1:100:150 to 1:70:40 to obtain an anti-wear graphene lubricant additive, which is recorded as GO-HDI-HEA.

[0079] Embodiment 14

[0080] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method of Example 2, except that the mass ratio of GO powder:HDI:HEA is replaced from 1:100:150 to 1:50:40 to obtain an anti-wear graphene lubricant additive, which is recorded as GO-HDI-HEA.

[0081] Embodiment 15

[0082] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method of Example 2, except that the mass ratio of GO powder:HDI:HEA is replaced from 1:100:150 to 1:50:30 to obtain an anti-wear graphene lubricant additive, which is recorded as GO-HDI-HEA.

[0083] Example 16

[0084] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method of Example 2, except that the mass ratio of GO powder:HDI:HEA is replaced from 1:100:150 to 1:40:30 to obtain an anti-wear graphene lubricant additive, which is recorded as GO-HDI-HEA.

[0085] Embodiment 17

[0086] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method of Example 2, except that the mass ratio of GO powder:HDI:HEA is replaced from 1:100:150 to 1:40:20 to obtain an anti-wear graphene lubricant additive, which is recorded as GO-HDI-HEA.

[0087] Embodiment 18

[0088] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method of Example 2, except that the mass ratio of GO powder:HDI:HEA is replaced from 1:100:150 to 1:30:20 to obtain an anti-wear graphene lubricant additive, which is recorded as GO-HDI-HEA.

[0089] Embodiment 19

[0090] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method of Example 2, except that the mass ratio of GO powder:HDI:HEA is replaced from 1:100:150 to 1:30:10 to obtain an anti-wear graphene lubricant additive, which is recorded as GO-HDI-HEA.

[0091] Embodiment 20

[0092] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method of Example 2, except that the mass ratio of GO powder:HDI:HEA is replaced from 1:100:150 to 1:20:10 to obtain an anti-wear graphene lubricant additive, which is recorded as GO-HDI-HEA.

[0093] Embodiment 21

[0094] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method of Example 1, except that the mass ratio of single-layer graphene:HDI:HEA in Example 1 is replaced from 1:50:50 to 1:100:100 to obtain an anti-wear graphene lubricant additive, which is recorded as G-HDI-HEA.

[0095] Embodiment 22

[0096] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method in Example 1, except that the mass ratio of single-layer graphene:HDI:HEA in Example 1 is replaced from 1:50:50 to 1:70:70 to obtain an anti-wear graphene lubricant additive, which is recorded as G-HDI-HEA.

[0097] Embodiment 23

[0098] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method in Example 1, except that the mass ratio of single-layer graphene:HDI:HEA in Example 1 is replaced from 1:50:50 to 1:30:30 to obtain an anti-wear graphene lubricant additive, which is recorded as G-HDI-HEA.

[0099] Embodiment 24

[0100] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method in Example 1, except that the mass ratio of single-layer graphene:HDI:HEA in Example 1 is replaced from 1:50:50 to 1:20:20 to obtain an anti-wear graphene lubricant additive, which is recorded as G-HDI-HEA.

[0101] Embodiment 25

[0102] A method for preparing an anti-wear graphene lubricant additive is the same as the preparation method of Example 1, except that the mass ratio of single-layer graphene:HDI:HEA in Example 1 is replaced from 1:50:50 to 1:15:10 to obtain an anti-wear graphene lubricant additive, which is recorded as G-HDI-HEA.

[0103] Embodiment 26

[0104] A method for preparing an anti-wear graphene lubricant additive is the same as the method for preparing Example 1, except that the mass ratio of the single-layer graphene:HDI:HEA in Example 1 is replaced from 1:50:50 to 1:10:15 to obtain an anti-wear graphene lubricant additive, which is denoted as G-HDI-HEA. Table 1 The morphology of the schemes of Examples 2 to 10 of the present invention and the anti-wear graphene lubricant additives obtained therefrom

[0105] Serial number GO powder HDI HEA Product form (after reaction - after filtration and drying) Example 2 1 100 150 Black block solid--Black colloidal solid Example 3 1 150 100 Black block solid--Black colloidal solid Example 4 1 100 100 Black block solid--Black colloidal solid Example 5 1 70 70 Black block solid--Black colloidal solid Example 6 1 50 50 Black jelly solid--black gelatinous solid Example 7 1 30 30 Black liquid--black powder Example 8 1 20 20 Black liquid--black powder Example 9 1 15 10 Black liquid--black powder Example 10 1 10 15 Black liquid--black powder

[0106] According to the results in Table 1, the anti-wear graphene lubricant additives prepared in Examples 2 to 6 are black block solids, which are black colloidal solids after washing and drying; the anti-wear graphene lubricant additives prepared in Examples 7 to 10 are black liquids, which are black powders after washing and drying; it is shown that as the amount of HDI and HEA decreases, Example 6 at the critical point is the best reaction ratio. If the ratio is higher than this range, a large amount of semi-capped compounds of HDI and HEA will be entangled together, causing the graphene oxide to agglomerate and be difficult to disperse; if the ratio is lower than this range, the modification amount is small.

[0107] Table 2 The design of the scheme of Examples 11 to 20 of the present invention and the morphology of the anti-wear graphene lubricant additives prepared therefrom

[0108]

[0109]

[0110] The results in Table 2 show that the change pattern of the morphology of the anti-wear graphene lubricant additives prepared in Examples 11 to 20 is basically consistent with the description of the morphology of the anti-wear graphene lubricant additives in Examples 2 to 10, indicating that as the amount of HDI and HEA decreases, Examples 6 and 14 at the critical point are the best reaction ratios. Above this ratio range, a large number of semi-capped compounds of HDI and HEA will be entangled together, causing the graphene oxide to agglomerate, making it difficult to disperse in the DMF solution later. Below this ratio, the modification amount is small and the effect is poor when used.

[0111] Table 3 The morphology of the schemes of Examples 21 to 26 of the present invention and the anti-wear graphene lubricant additives prepared therefrom

[0112] Serial number Single-layer graphene HDI HEA Product form (after reaction - after filtration and drying) Embodiment 21 1 100 100 Black block solid--Black colloidal solid Embodiment 22 1 70 70 Black block solid--Black colloidal solid Example 1 1 50 50 Black jelly solid--black gelatinous solid Embodiment 23 1 30 30 Black liquid--black powder Embodiment 24 1 20 20 Black liquid--black powder Embodiment 25 1 15 10 Black liquid--black powder Embodiment 26 1 10 15 Black liquid--black powder

[0113] The results in Table 3 show that the anti-wear graphene lubricant additives prepared in Examples 21 to 26 according to Examples 4 to 10 above have the same morphological rules, indicating that as the amount of HDI and HEA decreases, Examples 1 and 22 at the critical point are the best reaction ratios. Above this ratio range, a large number of semi-capped compounds of HDI and HEA will be entangled together, causing the monolayer graphene to agglomerate and be difficult to disperse in DMF; below this ratio, more hydroxyl and carboxyl groups remain on the surface of the monolayer graphene, resulting in poor results when used.

[0114] The monolayer graphene, graphene oxide, and the anti-wear graphene lubricant additives prepared in Examples 1 and 6 were respectively applied to trimethylolpropane oleate, and their tribological properties were tested. The application method was as follows: 20 mg of the anti-wear graphene lubricant additive was first diffused in 100 mL of dichloromethane, and the dichloromethane was removed after ultrasonic treatment for 1 hour, and then fully diffused with 20 mL of petroleum ether, and ultrasonic treatment was performed for 1 hour to obtain the anti-wear graphene lubricant additive-petroleum ether. Then, the fully diffused anti-wear graphene lubricant additive-petroleum ether was added to 200 g of trimethylolpropane oleate, and the petroleum ether was completely volatilized by ultrasonic treatment for 1 hour.

[0115] Tribological performance test method: According to the petrochemical industry standard NB / SH / T-0189, a four-ball friction test was conducted to detect the wear spot diameter and friction coefficient. The test was conducted by the Lubricating Material Testing Center of Jinxuechi Technology (Ma'anshan) Co., Ltd. The test results are shown in Table 4.

[0116] Table 4 Tribological performance test results of monolayer graphene, graphene oxide, and anti-wear graphene lubricant additives prepared in Example 1 and Example 6

[0117]

[0118] It can be seen from Table 3 that after adding 1 / 10,000 of a single-layer graphene, the wear spot diameter is reduced by about 25%, and the average friction coefficient remains unchanged. When the amount of single-layer graphene is increased or decreased, the wear spot diameter is significantly increased, so adding 1 / 10,000 of a single-layer graphene is the best; adding 1 / 10,000 of Example 1 to obtain G-HDI-HEA reduces the wear spot diameter by 2%, and the friction coefficient is reduced by 10% relative to the same amount of single-layer graphene. Adding 1 / 10,000 of graphene oxide powder has too large a friction coefficient; adding 1 / 10,000 of Example 6 to obtain GO-HDI-HEA greatly reduces the wear spot diameter, and the friction coefficient is reduced by 10% relative to the same amount of graphene.

[0119] The anti-wear graphene lubricant additive prepared in Example 1 was fully ground in a mortar, placed in DMF, xylene and methanol for diffusion and then allowed to stand for 12 hours. The diffusion conditions were as follows: Figure 4 Observation Figure 4 a It is concluded that the anti-wear graphene lubricant additive prepared in Example 1 has good diffusion in the polar solvent DMF and a slow precipitation rate. Figure 4 b It is concluded that the anti-wear graphene lubricant additive prepared in Example 1 has relatively poor diffusion in the non-polar solvent xylene, but precipitates faster than in the polar solvent. Figure 4 c It is concluded that the anti-wear graphene lubricant additive prepared in Example 1 has good diffusivity in the polar solvent methanol and a slow precipitation rate.

[0120] 2 mg of the anti-wear graphene lubricant additive prepared in Example 1 was diffused in 10 mL of dichloromethane, and the dichloromethane was removed after ultrasonic treatment for 1 h. Then, 2 mL of petroleum ether was used for full diffusion, and ultrasonic treatment was continued for 1 h. The diffusion was as follows: Figure 5 As shown, observe Figure 5 It was concluded that the anti-wear graphene lubricant additive could fully diffuse in petroleum ether and only had obvious precipitation after 48 hours.

[0121] observe Figure 6 It is concluded that the anti-wear graphene lubricant additive can be well evenly diffused in trimethylolpropane oleate and maintain continuous diffusion for more than 48 hours in trimethylolpropane oleate.

[0122] observe Figure 7 It was concluded that GO powder contains epoxy and hydroxyl functional groups on both sides of its plane and carboxyl groups on the edge. The most characteristic infrared spectrum of the anti-wear graphene lubricant additive obtained is the 3330 cm-1 corresponding to the OH stretching vibration. -1 The disappearance of a strong broadband centered at 3400cm -1 The vibration absorption peak of NH appears around 2933cm -1 and 2861cm -1The peaks near 2280cm are the symmetric and asymmetric stretching vibration absorption peaks of methylene; -1 There is no peak of -NCO group near 1726cm -1 The left and right positions are the stretching vibration absorption peaks of C=O (carbonyl); 1620cm -1 The band at 1420 cm is attributed to the stretching of the C=C double bond; -1 and 1130cm -1 The left and right positions are the stretching vibration and tensile vibration absorption peaks of CO (epoxy group); 1052cm -1 The left and right positions are the stretching vibration peaks of CO (alkoxy). -1 The absence of a peak of -NCO group nearby indicates that there is no extra semi-capped residue in G-HDI-HEA. From the above infrared spectra, it can be concluded that when the mass ratio of GO powder: HDI: HEA is 1:70:70 and 1:50:50, the characteristic peak of the anti-wear graphene lubricant additive is stronger, and the semi-capped compound has a better affinity with graphene oxide.

[0123] like Figure 8 As shown in the figure, the characteristic peaks of GO powder are the characteristic diffraction peak of (001) crystal plane at 10.0° and the characteristic diffraction peak of (100) crystal plane at 43.4°, which indicates that a large number of oxygen-containing groups in GO powder are located in the lamellar structure, and the lamellar structure is complete. After the GO powder is grafted with semi-terminated compounds, the (001) crystal plane diffraction peak basically disappears, and the amorphous carbon (002) crystal plane diffraction peak appears at 21.1°, indicating that most of the oxygen-containing groups have reacted under this condition. When the mass ratio of GO powder: HDI: HEA is 1:70:70, 1:50:50 and 1:30:30, the (100) crystal plane diffraction peak completely disappears, and when the mass ratio of GO powder: HDI: HEA continues to decrease, there is still a characteristic diffraction peak of (100) crystal plane, which indicates that when the mass ratio of GO powder: HDI: HEA is less than 1:30:30, the semi-terminated compound generated is less and cannot fully react with graphene oxide.

[0124] observe Fig. 9 Figure a and Fig. 9 Figure b shows that wrinkles and lattices can be clearly observed in GO powder. Fig. 9 Figure c and Fig. 9 Figure d in the figure shows that the edge of the anti-wear graphene lubricant additive prepared in Example 6 has become blurred, and the lattice and boundary cannot be accurately observed. This is because during the grafting reaction, the semi-capped compound completely covers the surface of the graphene oxide, making the surface of the graphene oxide blurred and wrinkles and unit cells cannot be observed, further proving that the grafting is successful.

[0125] observe Fig.10 It is concluded that the most characteristic feature of the infrared spectrum of the anti-wear graphene lubricant additive obtained by the monolayer graphene containing only a very small amount of carboxyl groups at the edge is 3400cm -1 The vibration absorption peak of -NH appears around 2933cm -1 and 2861cm -1 The peak near is attributed to the sp generated by the defect sites in the monolayer graphene network. 2 CH stretching band, which is the absorption peak of symmetric and asymmetric stretching vibration of methylene; 2280cm -1 There is no peak of -NCO group near 1726cm -1 The left and right positions are the carbonyl stretching vibration absorption peaks; 162cm -1 The band at is attributed to the stretching of the carbon-carbon double bond. When the mass ratio of monolayer graphene: HDI: HEA is 1:100:100, 1:70:70 and 1:50:50, the peak of the infrared spectrum is strong, but when the mass ratio of monolayer graphene: HDI: HEA is reduced, the infrared spectrum shows basically no reaction.

[0126] observe Fig.11 It was found that in the XRD spectrum of single-layer graphene, the characteristic peaks located at 26.6° and 54.7° belong to the characteristic diffraction peaks of the (002) crystal plane and (004) crystal plane of single-layer graphene, respectively. Among them, the characteristic peak of the (002) crystal plane showed a strong sharp peak, indicating that the carbon atoms in the single-layer graphene are arranged regularly. After the monolayer graphene is grafted by Example 1, the (002) crystal plane diffraction peak basically disappears, and the diffraction peaks of the amorphous carbon (002) crystal plane and the (100) crystal plane appear at 23.4° and 43.4°, respectively. However, compared with the (002) crystal plane diffraction peak of the monolayer graphene, the amorphous carbon (002) crystal plane diffraction peak is wider and has lower intensity. When the mass ratio of monolayer graphene:HDI:HEA is 1:100:100, 1:70:70 and 1:50:50, the (002) crystal plane diffraction peak completely disappears, and when the mass ratio of monolayer graphene:HDI:HEA continues to decrease, there is still a characteristic diffraction peak of the (002) crystal plane, which indicates that when the mass ratio of monolayer graphene:HDI:HEA is less than 1:50:50, the reaction is not sufficient. According to the Bragg equation calculation, the interlayer spacing of G-HDI-HEA is significantly increased compared to single-layer graphene.

[0127] like Fig.12 a and Fig.12 As shown in Fig. 2a, the wrinkles and lattice of the single-layer graphene can be clearly observed. After adding polyvinyl pyrrolidone (PVP), it is found that the single-layer graphene is more difficult to polymerize. The role of polyvinyl pyrrolidone is to convert the graphene structure into a single-layer structure more fully. The addition of PVP in the present invention is to take a clearer TEM image with a clearer structure, such as Fig.12 c and Fig.12 d. Observation Fig.12 e. Fig.12 f. Fig.12 g and Fig.12 h concluded that the edges of the anti-wear graphene lubricant additive prepared in Example 1 and the anti-wear graphene lubricant additive prepared in Example 1 with PVP added were blurred, and the lattice and boundary could not be accurately observed, which indicated that the semi-capped compound and the monolayer graphene had been well compounded; Fig.12 i. Fig.12 j. Fig.12 k and Fig.12 It can be concluded that the anti-wear graphene lubricant additives prepared in Example 23 and Example 25 have obvious organic molecules, and the distribution is very uneven.

[0128] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0129] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing an anti-wear graphene lubricant additive, characterized in that: The following steps are involved: Adding 2-hydroxyethyl acrylate solution dropwise to the 1,6-hexamethylene diisocyanate solution to carry out an addition esterification reaction to obtain a semi-blocked compound; After mixing the semi-capped compound with the dispersion of graphene, a grafting reaction is performed, in which -NCO on the semi-capped compound reacts with -OH on the graphene to form carbamate, and reacts with -COOH on the graphene to form amide, thereby obtaining an anti-wear graphene lubricant additive; In the anti-wear graphene lubricant additive, the mass ratio of graphene, 2-hydroxyethyl acrylate and 1,6-hexamethylene diisocyanate is 1:10-150:10-150.

2. The method for preparing an anti-wear graphene lubricant additive according to claim 1, characterized in that: The conditions for the addition esterification reaction are: add dropwise at -5°C to 5°C for 20min to 30min and then continue the reaction for 8h to 12h.

3. The method for preparing an anti-wear graphene lubricant additive according to claim 1, characterized in that: The conditions of the grafting reaction are: first react at -5°C to 5°C for 0.5h to 1h, then react at room temperature for 0.5h to 1h, and finally react at 100°C to 120°C for 12h to 24h.

4. The method for preparing an anti-wear graphene lubricant additive according to claim 1, characterized in that: The solvents in the 2-hydroxyethyl acrylate solution, the 1,6-hexamethylene diisocyanate solution and the graphene dispersion are all anhydrous N,N-dimethylformamide.

5. The method for preparing an anti-wear graphene lubricant additive according to claim 1, characterized in that: The graphene is selected from single-layer graphene or graphene oxide.

6. The method for preparing an anti-wear graphene lubricant additive according to claim 1, characterized in that: The particle size of single-layer graphene is 5μm to 20μm, and the specific surface area of ​​graphene is 50cm 2 / g~300cm 2 / g.

7. An anti-wear graphene lubricant additive prepared by the preparation method according to any one of claims 1 to 6.

8. A synthetic ester lubricating oil.

9. The synthetic ester lubricating oil according to claim 8, characterized in that: The synthetic ester lubricant is prepared by adding an anti-wear graphene lubricant additive to a synthetic ester base oil; Among them, the mass ratio of the anti-wear graphene lubricant additive to the synthetic ester base oil is 1:10000-20000.

10. The synthetic ester lubricating oil according to claim 9, characterized in that: The synthetic ester base oil is selected from trimethylolpropane oleate base oil, pentaerythritol oleate base oil or poly-alpha-olefin base oil.

Images