Graphene composite rolling oil as well as preparation method and application thereof

Abstract

The invention relates to the technical field of lubricating oil, in particular to graphene composite rolling oil and a preparation method and application thereof. The rolling oil comprises base oil, branched oleic acid modified graphene containing quaternary ammonium salt, an anti-wear reagent at extreme pressure, an antioxidant, an anti-rust agent and a defoaming agent. Wherein the quaternary ammonium salt branched oleic acid is prepared through a thiol-ene click reaction and a quaternization reaction, and the dispersity, the interface adsorption strength and the high-temperature stability of graphene in a lubricating oil system can be remarkably improved. The product provided by the invention is suitable for rolling lubrication under severe working conditions such as high temperature and high load, and has a wide industrial application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of rolling oils, and in particular to a graphene composite rolling oil and a preparation method and application thereof. Background Art

[0002] Graphene, due to its unique layered structure and excellent tribological properties, holds great promise for application in lubricating materials. As an additive, it not only forms a protective film on contact surfaces, effectively reducing wear and friction between metals, but also exhibits excellent chemical stability. However, graphene itself easily aggregates, making it difficult to stably disperse in organic base oils or mineral oils, significantly weakening its lubricating and protective properties. To this end, researchers commonly employ surface modification methods to enhance graphene's dispersibility in oily systems, with physical adsorption or chemical modification using fatty acids (such as oleic acid) becoming common approaches.

[0003] Oleic acid is a common fatty acid modifier. Due to its long hydrophobic chain and certain polarity, it can improve the dispersibility of graphene in oil and its compatibility with the oil system to a certain extent. However, the stability and lubrication performance of oleic acid-modified graphene are still subject to many limitations. First, the oleic acid molecule has a linear structure, which has limited spatial barrier between graphene sheets. It is prone to secondary agglomeration under long-term use or harsh working conditions such as high temperature and high shear, which eventually leads to the precipitation of graphene in the lubricant. Secondly, oleic acid contains unsaturated double bonds. In actual high-temperature process, it is prone to oxidation, fracture or polymerization reaction, resulting in deterioration of material properties and difficulty in maintaining the dense and intact lubricating film structure for a long time. In addition, oleic acid as a dispersant has limited adsorption capacity on metal surfaces, making it difficult to support the long-term anti-wear and extreme pressure performance of the lubrication system under extreme pressure or continuous rolling. Therefore, although traditional oleic acid-modified graphene performs well under short-term room temperature conditions, its dispersion stability, interface adsorption strength and protection capabilities are difficult to meet the actual needs of the high-end lubrication field under extreme working conditions such as high temperature and high load, becoming an important bottleneck in industrial applications. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to propose a graphene composite rolling oil and its preparation method and application, so as to solve the problem of poor dispersibility of oleic acid-modified graphene and high-temperature instability leading to decreased lubrication performance.

[0005] Based on the above objectives, the present invention provides a graphene composite rolling oil, which includes the following components, by weight: 70-100 parts of base oil, 0.5-1.5 parts of branched oleic acid-modified graphene containing quaternary ammonium salt, 2.5-7.5 parts of extreme pressure anti-wear agent, 1.5-2.8 parts of antioxidant, 0.3-1 part of rust inhibitor and 0.05-0.2 part of defoaming agent.

[0006] Preferably, the base oil is one or a mixture of 150SN mineral oil, 200SN mineral oil, PAO 6 synthetic oil, and PAO 10 synthetic oil.

[0007] Preferably, the branched oleic acid-modified graphene containing quaternary ammonium salt is obtained by reacting the carboxyl groups in the branched oleic acid containing quaternary ammonium salt with the hydroxyl groups on the surface of the hydroxylated graphene, followed by thermal reduction.

[0008] Preferably, the weight ratio of the branched oleic acid containing quaternary ammonium salt to the hydroxylated graphene is 1:3-8.

[0009] Preferably, the thermal reduction atmosphere is argon, the temperature is 240-260° C., and the time is 1.5-2.5 h.

[0010] Preferably, the branched oleic acid containing quaternary ammonium salt is prepared by reacting oleic acid and 3-(dimethylamino)-1-propanethiol through a thiol-ene click reaction to prepare terminal tertiary amine oleic acid, which is then reacted with dodecane bromide through a quaternization reaction to obtain the branched oleic acid.

[0011] Preferably, the molar ratio of oleic acid, 3-(dimethylamino)-1-propanethiol and brominated dodecane is 1:1-1.2:1-1.2.

[0012] Preferably, the specific preparation steps of the branched oleic acid containing quaternary ammonium salt are as follows:

[0013] (1) Under nitrogen atmosphere, oleic acid, 3-(dimethylamino)-1-propanethiol and benzoin dimethyl ether were added to methanol, stirred for 30 minutes, and then reacted under ultraviolet light for 12 hours. After purification, vacuum drying was performed to obtain tertiary amine-terminated oleic acid.

[0014] (2) Under nitrogen atmosphere, tertiary amine-terminated oleic acid and bromododecane were added to N,N-dimethylformamide, stirred and reacted at room temperature for 48 hours, purified, and vacuum-dried to obtain branched oleic acid containing quaternary ammonium salt.

[0015] Preferably, the extreme pressure anti-wear agent is one or a mixture of tritolyl phosphate, tributyl phosphate, phosphite, and zinc dialkyl dithiophosphate.

[0016] Preferably, the antioxidant is one or a mixture of octyldiphenylamine, nonyldiphenylamine, phenyl-α-naphthylamine, and dilauryl thiodipropionate.

[0017] Preferably, the rust inhibitor is one or a mixture of dodecenylsuccinic acid, hexadecenylsuccinic acid half ester, and sorbitol monooleate.

[0018] Preferably, the defoaming agent is one or a mixture of silicone defoaming agent, polyether defoaming agent, and acrylate defoaming agent.

[0019] Furthermore, the present invention also provides a method for preparing graphene composite rolling oil, comprising the following steps: adding branched oleic acid-modified graphene containing quaternary ammonium salt to base oil, heating to 45-55°C, high-speed shearing for 20-40 minutes, and then sequentially adding extreme pressure anti-wear agent, antioxidant, rust inhibitor and defoaming agent, heating to 65-75°C, stirring for 70-120 minutes to obtain graphene composite rolling oil.

[0020] Furthermore, the present invention also provides an application of graphene composite rolling oil for metal rolling, wherein the metal is steel, aluminum alloy, copper, etc.

[0021] Beneficial effects of the present invention:

[0022] The present invention addresses the technical drawbacks of conventional oleic acid-modified graphene in lubrication applications, such as poor stability and easy failure of the lubricating film. By creatively introducing branched quaternary ammonium salt molecules onto the graphene surface, this method achieves a significant performance upgrade. While oleic acid-modified graphene can impart a certain degree of dispersibility, its molecules are only linear and have limited steric hindrance, so graphene still tends to agglomerate in the lubrication system, resulting in insufficient dispersion stability. Furthermore, the double bonds in the oleic acid molecules are susceptible to cleavage reactions at high temperatures, causing the lubricant to exhibit a decrease in lubrication protection under harsh operating conditions, making it impossible to maintain long-lasting extreme pressure and friction-reducing properties. This makes it difficult to meet the demanding service requirements in actual heavy-duty rolling and high-temperature operations.

[0023] The present invention not only significantly improves the dispersibility and interfacial adsorption capacity of the material in base oil by introducing long-chain branched quaternary ammonium salts on the graphene surface, but also effectively overcomes the shortcomings of traditional oleic acid-modified materials such as insufficient thermal stability and discontinuous lubricating film. The introduction of branched long-chain structures enhances the spatial barrier effect, suppresses the secondary agglomeration of nanosheets, and ensures that the graphene sheets are highly dispersed. The special interfacial activity of the quaternary ammonium salt cations strengthens adsorption with the metal substrate, making the lubricating film more dense, uniform, and stable. The synergistic effect of the bifunctional groups enhances the self-repairing ability of the lubricating film under high temperature and high load, provides a lasting friction reduction and protective effect for the lubrication system, and broadens the practical application scenarios of the material.

[0024] In summary, the present invention not only solves the core bottleneck problem of oleic acid-modified graphene, but also achieves multiple optimizations of the interface functions of nanomaterials through molecular structure design guidance, providing a new idea and a solid foundation for the development and application of high-performance lubricants, and has important engineering application and promotion value. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0026] In a specific embodiment of the present invention, the hydroxylated graphene was purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd., with a serial number of XF307, a sheet diameter of 1-3 μm, and a thickness of 1-5 nm.

[0027] Example 1:

[0028] (1) Under nitrogen atmosphere, 5 g of oleic acid, 2.2 g of 3-(dimethylamino)-1-propanethiol, and 0.3 g of benzoin dimethyl ether were added to 50 mL of methanol and stirred for 30 min. The mixture was then reacted under ultraviolet light (λ = 365 nm) for 12 h. After the reaction, the solvent was removed by rotary evaporation, and the product was extracted with ethyl acetate / water (3:1, v / v) and purified by silica gel column chromatography (developing solvent: petroleum ether / ethyl acetate = 8:1). The product was dried under vacuum at 60 °C for 6 h to obtain terminal tertiary amine oleic acid.

[0029] (2) Under nitrogen atmosphere, 5 g of tertiary amine-terminated oleic acid and 3 g of bromododecane were added to 50 mL of N,N-dimethylformamide and stirred at room temperature for 48 h. After the reaction was completed, the mixture was added dropwise to 100 mL of icy ether for precipitation, and centrifuged (6000 rpm, 10 min). The precipitate was washed three times with ether and dried in vacuum at 40 °C for 8 h to obtain branched oleic acid containing quaternary ammonium salt;

[0030] (3) 1 g of hydroxylated graphene was added to 50 mL of ethanol and ultrasonically treated (power 800 W, frequency 40 kHz) for 60 min. Then, 3 g of branched oleic acid containing quaternary ammonium salt and 0.03 g of p-toluenesulfonic acid were added. The temperature was raised to 70 ° C. The reaction was stirred under reflux for 8 h. The mixture was then transferred to a reactor. Argon was introduced to replace the air three times. The temperature was raised to 240 ° C at 5 ° C / min and maintained for 1.5 h to complete high-temperature reduction. The mixture was centrifuged and washed with n-hexane three times. The precipitate was vacuum dried at 60 ° C for 6 h to obtain branched oleic acid-modified graphene containing quaternary ammonium salt.

[0031] (4) Take 0.5g of branched oleic acid-modified graphene containing quaternary ammonium salt and add it to 70g of 150SN mineral oil (base oil). Heat it to 45℃ and shear it at high speed (12000rpm) for 20min. Then add 2.5g of trimethylphenyl phosphate (extreme pressure anti-wear agent), 1.5g of octyldiphenylamine (antioxidant), 0.3g of dodecenylsuccinic acid (rust inhibitor) and 0.05g of dimethyl silicone oil (defoaming agent) in sequence. Heat it to 65℃ and stir it (800rpm) for 70-120min to obtain graphene composite rolling oil.

[0032] Example 2:

[0033] (1) Under nitrogen atmosphere, 5 g of oleic acid, 2.2 g of 3-(dimethylamino)-1-propanethiol, and 0.3 g of benzoin dimethyl ether were added to 50 mL of methanol and stirred for 30 min. The mixture was then reacted under ultraviolet light (λ = 365 nm) for 12 h. After the reaction, the solvent was removed by rotary evaporation, and the product was extracted with ethyl acetate / water (3:1, v / v) and purified by silica gel column chromatography (developing solvent: petroleum ether / ethyl acetate = 8:1). The product was dried under vacuum at 60 °C for 6 h to obtain terminal tertiary amine oleic acid.

[0034] (2) Under nitrogen atmosphere, 5 g of tertiary amine-terminated oleic acid and 3 g of bromododecane were added to 50 mL of N,N-dimethylformamide and stirred at room temperature for 48 h. After the reaction was completed, the mixture was added dropwise to 100 mL of icy ether for precipitation, and centrifuged (6000 rpm, 10 min). The precipitate was washed three times with ether and dried in vacuum at 40 °C for 8 h to obtain branched oleic acid containing quaternary ammonium salt;

[0035] (3) 1 g of hydroxylated graphene was added to 50 mL of ethanol and ultrasonically treated (power 800 W, frequency 40 kHz) for 60 min. Then, 5 g of branched oleic acid containing quaternary ammonium salt and 0.05 g of p-toluenesulfonic acid were added. The temperature was raised to 75 °C, and the mixture was stirred under reflux for 12 h. The mixture was then transferred to a reactor, argon was introduced to replace the air three times, and the temperature was raised to 250 °C at 5 °C / min and maintained for 2 h to complete high-temperature reduction. The mixture was centrifuged and washed with n-hexane three times. The precipitate was vacuum dried at 60 °C for 6 h to obtain branched oleic acid-modified graphene containing quaternary ammonium salt.

[0036] (4) Take 1 g of branched oleic acid-modified graphene containing quaternary ammonium salt and add it to 85 g of 150SN mineral oil (base oil). Heat it to 50 °C and high-speed shear (12000 rpm) for 30 min. Then add 5 g of trimethylphenyl phosphate (extreme pressure anti-wear agent), 2.2 g of octyldiphenylamine (antioxidant), 0.65 g of dodecenylsuccinic acid (rust inhibitor) and 0.1 g of dimethyl silicone oil (defoaming agent) in sequence. Heat it to 70 °C and stir (800 rpm) for 90 min to obtain graphene composite rolling oil.

[0037] Example 3:

[0038] (1) Under nitrogen atmosphere, 5 g of oleic acid, 2.2 g of 3-(dimethylamino)-1-propanethiol, and 0.3 g of benzoin dimethyl ether were added to 50 mL of methanol and stirred for 30 min. The mixture was then reacted under ultraviolet light (λ = 365 nm) for 12 h. After the reaction, the solvent was removed by rotary evaporation, and the product was extracted with ethyl acetate / water (3:1, v / v) and purified by silica gel column chromatography (developing solvent: petroleum ether / ethyl acetate = 8:1). The product was dried under vacuum at 60 °C for 6 h to obtain terminal tertiary amine oleic acid.

[0039] (2) Under nitrogen atmosphere, 5 g of tertiary amine-terminated oleic acid and 3 g of bromododecane were added to 50 mL of N,N-dimethylformamide and stirred at room temperature for 48 h. After the reaction was completed, the mixture was added dropwise to 100 mL of icy ether for precipitation, and centrifuged (6000 rpm, 10 min). The precipitate was washed three times with ether and dried in vacuum at 40 °C for 8 h to obtain branched oleic acid containing quaternary ammonium salt;

[0040] (3) 1 g of hydroxylated graphene was added to 50 mL of ethanol and ultrasonically treated (power 800 W, frequency 40 kHz) for 60 min. Then, 8 g of branched oleic acid containing quaternary ammonium salt and 0.08 g of p-toluenesulfonic acid were added. The temperature was raised to 80 ° C. The reaction was stirred under reflux for 16 h. The mixture was then transferred to a reactor. Argon was introduced to replace the air three times. The temperature was raised to 260 ° C at 5 ° C / min and maintained for 2.5 h to complete high-temperature reduction. The mixture was centrifuged and washed with n-hexane three times. The precipitate was vacuum dried at 60 ° C for 6 h to obtain branched oleic acid-modified graphene containing quaternary ammonium salt.

[0041] (4) Take 1.5g of branched oleic acid-modified graphene containing quaternary ammonium salt and add it to 100g of 150SN mineral oil (base oil). Heat it to 55℃ and high-speed shear (12000rpm) for 40min. Then add 7.5g of trimethylphenyl phosphate (extreme pressure anti-wear agent), 2.8g of octyldiphenylamine (antioxidant), 1g of dodecenylsuccinic acid (rust inhibitor) and 0.2g of dimethyl silicone oil (defoaming agent) in sequence. Heat it to 75℃ and stir it (800rpm) for 120min to obtain graphene composite rolling oil.

[0042] Comparative Example 1:

[0043] The difference between Comparative Example 1 and Example 2 is that the branched oleic acid containing quaternary ammonium salt in step (3) is replaced by oleic acid;

[0044] Comparative Example 2:

[0045] The difference between Comparative Example 2 and Example 2 is that the branched oleic acid containing quaternary ammonium salt in step (3) is replaced by tertiary amine-terminated oleic acid;

[0046] Comparative Example 3:

[0047] Comparative Example 3 differs from Example 2 in that: 5 g of branched oleic acid containing quaternary ammonium salt in step (3) is replaced by a mixture of 3 g of tertiary amine-terminated oleic acid and 2 g of lauryltrimethylammonium bromide;

[0048] Comparative Example 4:

[0049] The difference between Comparative Example 4 and Example 2 is that the brominated dodecane in step (2) is replaced by bromoethane.

[0050] Performance testing:

[0051] High-temperature four-ball friction test: Using an MXW-10 four-ball testing machine, following a 10-minute pre-run-in at room temperature, the test was heated at a rate of 5°C / min to 180°C. The maximum no-seizure load (PB value) and wear spot diameter (accurate to 0.01 mm) were measured. The steel balls were made of GCr15 and had a hardness of HRC 64-66. The results are shown in Table 1.

[0052] Rolling test: Using the rolling oil samples prepared in Examples 1-3 and Comparative Examples 1-4, 0.05 mm thick 304 stainless steel strips were rolled on a Φ350×450 mm four-roll cold rolling mill at a rolling speed of 15 m / s and a pass reduction of 35%. The surface roughness Ra of the rolled strips was tested. The results are shown in Table 1.

[0053] Table 1 Performance test results

[0054] PB value / N Wear spot diameter / mm Roughness Ra / μm Example 1 785 0.42 0.22 Example 2 825 0.38 0.18 Example 3 832 0.35 0.20 Comparative Example 1 510 0.63 0.46 Comparative Example 2 595 0.55 0.41 Comparative Example 3 675 0.49 0.33 Comparative Example 4 725 0.45 0.29

[0055] Data Analysis:

[0056] Overall Analysis of Examples 1-3: The data in Table 1 indicate that the present invention's use of graphene modified with a specific branched structure containing quaternary ammonium oleic acid can significantly enhance lubrication performance. Chemical modification with branched oleic acid may enhance the dispersion stability of graphene in the base oil through the steric hindrance of the long-chain alkyl group, which helps the nanosheets form a more complete lubricating film on the metal surface, thereby exhibiting excellent load-bearing capacity and surface smoothing. Furthermore, it is speculated that the charge stabilization of the quaternary ammonium salt groups and the synergistic effect of the long hydrophobic chains may be the key factor in achieving a stable friction coefficient and reducing wear spot size.

[0057] The data of embodiment 2 and comparative example 1 in comparison table 1 show that the branched oleic acid modified graphene containing quaternary ammonium salt has significant performance advantage compared with traditional oleic acid. The performance gap may be due to the steric hindrance effect that the pure oleic acid molecular chain forms in base oil, and the double bond in oleic acid is easily cracked at high temperature, causing dispersion failure under high temperature working condition. And the long-chain quaternary ammonium salt modification of embodiment 2 has enhanced the compatibility of graphene and base oil by amphiphilic structure, and its cationic characteristic may form strong electrostatic adsorption with metal surface. This is conducive to building continuous and stable lubrication-extreme pressure composite film, thereby promoting extreme pressure anti-wear performance and surface finish performance.

[0058] Comparing the data of Example 2 and Comparative Example 2 in Table 1, it can be seen that the performance of the terminal tertiary amine oleic acid is limited compared to the quaternary ammonium salt branched structure. The tertiary amine group may lead to insufficient adsorption of graphene and lack the spatial stabilization effect of the branched long alkyl chain. During the high-temperature rolling process, the tertiary amine modified body has poor directional arrangement stability at the metal interface. The quaternized structure of Example 2 provides continuous electrostatic repulsion through cationic properties, combined with the steric hindrance of the C12 alkyl chain, effectively suppressing the stacking aggregation of the nanosheets, which is the core mechanism for achieving a lower wear spot diameter.

[0059] The data of embodiment 2 and comparative example 3 in comparison table 1, it can be seen that physical mixing modifier is difficult to reach the effect of chemical bonding modification.In the mixed system, quaternary ammonium salt surfactant may only adhere to Graphene by physical adsorption, and desorption easily occurs in shear force field.And the branched oleic acid of embodiment 2 forms stable complex with Graphene by covalent bond, and the synergistic effect of its intramolecular quaternary ammonium salt-alkyl chain can maintain the structural integrity under high temperature.It is inferred that this intramolecular bifunctional design has stronger interface anchoring ability than physical mixture, can continue to provide boundary lubrication protection in dynamic rolling process.

[0060] The data of Example 2 and Comparative Example 4 in Comparative Table 1 show that although Comparative Example 4 maintains quaternary ammonium salt structure, the short-chain ethyl group replaces and causes performance degradation, confirming that the alkyl chain length has a key influence on the modification effect. Shorter carbon chain may weaken the steric effect, reduce graphene dispersion stability. And the dodecyl long chain of Example 2 can form a more dense molecular barrier layer, and its higher conformational freedom helps to maintain lubricating film continuity under high temperature. This phenomenon illustrates that the quaternary ammonium salt cationic center must be coordinated with the hydrophobic group of appropriate chain length to give full play to the structural advantage of modifier.

[0061] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Within the scope of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

Claims

1. A graphene composite rolling oil, characterized in that, The composition comprises the following components in parts by weight: 70-100 parts of base oil, 0.5-1.5 parts of branched oleic acid-modified graphene containing quaternary ammonium salt, 2.5-7.5 parts of extreme pressure anti-wear agent, 1.5-2.8 parts of antioxidant, 0.3-1 parts of rust inhibitor and 0.05-0.2 parts of defoaming agent; The branched oleic acid-modified graphene containing quaternary ammonium salt is obtained by reacting the carboxyl group in the branched oleic acid containing quaternary ammonium salt with the hydroxyl group on the surface of the hydroxylated graphene, followed by thermal reduction. The branched oleic acid containing quaternary ammonium salt is prepared by preparing terminal tertiary amine oleic acid through a thiol-ene click reaction between oleic acid and 3-(dimethylamino)-1-propanethiol, and then reacting with dodecane bromide to obtain the branched oleic acid.

2. The graphene composite rolling oil according to claim 1, characterized in that The base oil is one or a mixture of 150SN mineral oil, 200SN mineral oil, PAO 6 synthetic oil, and PAO 10 synthetic oil.

3. The graphene composite rolling oil according to claim 1, characterized in that The weight ratio of the branched oleic acid containing quaternary ammonium salt to the hydroxylated graphene is 1:3-8.

4. The graphene composite rolling oil according to claim 1, characterized in that The thermal reduction is performed in an atmosphere of argon, at a temperature of 240-260° C., for a time of 1.5-2.5 h.

5. The graphene composite rolling oil according to claim 1, characterized in that The molar ratio of oleic acid, 3-(dimethylamino)-1-propanethiol and brominated dodecane is 1:1-1.2:1-1.

2.

6. The graphene composite rolling oil according to claim 1, characterized in that The extreme pressure anti-wear agent is one of tritolyl phosphate, tributyl phosphate, phosphite, and zinc dialkyl dithiophosphate, or a mixture of several of them.

7. The graphene composite rolling oil according to claim 1, characterized in that The antioxidant is one or a mixture of octyldiphenylamine, nonyldiphenylamine, phenyl-α-naphthylamine, and dilauryl thiodipropionate.

8. The graphene composite rolling oil according to claim 1, characterized in that The rust preventive agent is one or a mixture of dodecenylsuccinic acid, hexadecenylsuccinic acid half ester, and sorbitol monooleate.

9. The graphene composite rolling oil according to claim 1, characterized in that The defoaming agent is one or a mixture of silicone defoaming agents, polyether defoaming agents and acrylate defoaming agents.

10. A method for preparing the graphene composite rolling oil according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: adding branched oleic acid-modified graphene containing quaternary ammonium salt into base oil, heating the oil to 45-55° C., high-speed shearing for 20-40 minutes, sequentially adding an extreme pressure anti-wear agent, an antioxidant, a rust inhibitor and a defoaming agent, heating the oil to 65-75° C., stirring the oil for 70-120 minutes, and obtaining graphene composite rolling oil.