A graphene composite rolling oil, its preparation method and application

Abstract

This invention relates to the field of lubricating oil technology, specifically to a graphene composite rolling oil and its preparation method and application. The rolling oil comprises a base oil, quaternary ammonium salt-modified oleic acid graphene, extreme pressure anti-wear agent, antioxidant, rust inhibitor, and defoamer. The quaternary ammonium salt-modified oleic acid is prepared through a mercapto-ene click reaction and a quaternization reaction, which can significantly improve the dispersibility, interfacial adsorption strength, and high-temperature stability of graphene in the lubricating oil system. The product of this invention is suitable for rolling lubrication under harsh conditions such as high temperature and high load, and has broad industrial application prospects.

Description

Technical Field

[0001] This invention relates to the field of rolling oil technology, and in particular to a graphene composite rolling oil, its preparation method, and its application. Background Technology

[0002] Graphene, due to its unique layered structure and excellent tribological properties, shows broad application prospects in the field of lubrication materials. As an additive, it can not only form a protective film on the contact surface, effectively reducing wear and friction between metals, but also exhibits good chemical stability. However, graphene itself is prone to agglomeration and is difficult to disperse stably in organic base oils or mineral oils, which greatly weakens its lubricating and protective effects. To address this, researchers commonly employ surface modification methods to enhance the dispersibility of graphene in oily systems, with physical adsorption or chemical modification using fatty acids (such as oleic acid) being a common technical approach.

[0003] Oleic acid, a common fatty acid modifier, can improve the dispersibility and compatibility of graphene in oil to some extent due to its hydrophobic long chains and certain polarity. However, the stability and lubrication performance of oleic acid-modified graphene still have many limitations. First, oleic acid molecules have a linear structure, which limits their spatial barrier effect on graphene sheets. Under long-term use or harsh conditions such as high temperature and high shear, secondary aggregation is prone to occur, ultimately leading to the precipitation of graphene in the lubricant. Second, oleic acid contains unsaturated double bonds, which are prone to oxidation, breakage, or polymerization reactions in actual high-temperature processes, causing material property deterioration and making it difficult to maintain the density and integrity of the lubricating film structure over a long period. In addition, oleic acid has limited adsorption capacity on metal surfaces as a dispersant, making it difficult to support the long-term anti-wear and extreme pressure performance of the lubrication system under extreme pressure or continuous rolling processes. Therefore, although traditional oleic acid-modified graphene performs well under short-term room temperature conditions, its dispersion stability, interfacial adsorption strength, and protective capabilities are insufficient to meet the actual needs of high-end lubrication fields under extreme conditions such as high temperature and high load, becoming a major bottleneck in industrial applications. Summary of the Invention

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

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

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

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

[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℃, and the time is 1.5-2.5h.

[0010] Preferably, the branched oleic acid containing quaternary ammonium salt is prepared by oleic acid and 3-(dimethylamino)-1-propanethiol via a mercapto-olefin click reaction to obtain terminal tertiary amine oleic acid, which is then quaternized with bromododecane.

[0011] Preferably, the molar ratio of oleic acid, 3-(dimethylamino)-1-propanethiol and bromododecane 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 a nitrogen atmosphere, oleic acid, 3-(dimethylamino)-1-propanethiol and benzoin dimethyl ether were added to methanol, stirred for 30 min, and then reacted under ultraviolet light for 12 h. After purification and vacuum drying, tertiary amine oleic acid was obtained.

[0014] (2) Under a nitrogen atmosphere, terminal tertiary amine oleic acid and bromododecane were added to N,N-dimethylformamide and stirred at room temperature for 48 h. After purification and vacuum drying, branched oleic acid containing quaternary ammonium salt was obtained.

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

[0016] Preferably, the antioxidant is one or a mixture of several of the following: octyl diphenylamine, nonyl diphenylamine, phenyl-α-naphthylamine, and dilauryl thiodipropionate.

[0017] Preferably, the rust inhibitor is one or a mixture of several of dodecenyl succinic acid, hexadecenyl succinic acid half ester, and sorbitol monooleate.

[0018] Preferably, the defoamer is one or a mixture of several of the following: silicone defoamers, polyether defoamers, and acrylate defoamers.

[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℃, high-speed shearing for 20-40 minutes, then sequentially adding extreme pressure anti-wear agent, antioxidant, rust inhibitor and defoamer, heating to 65-75℃, 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] The beneficial effects of this invention are:

[0022] This invention addresses the technical shortcomings of traditional oleic acid-modified graphene in lubrication applications, such as poor stability and easy failure of the lubricating film. It creatively introduces branched quaternary ammonium salt molecules into the graphene surface, achieving a significant performance upgrade. While oleic acid-modified graphene can impart a certain degree of dispersibility, its linear molecular structure and limited steric hindrance still make it prone to aggregation in lubrication systems, resulting in insufficient dispersion stability. Furthermore, the double bonds in oleic acid molecules are prone to cracking at high temperatures, causing the lubricant to exhibit reduced lubrication protection under harsh operating conditions and failing to maintain long-term extreme pressure friction-reducing performance. Consequently, it struggles to meet the stringent service requirements of actual heavy-load rolling and high-temperature operations.

[0023] This invention introduces long-chain branched quaternary ammonium salts onto the surface of graphene, significantly improving the material's dispersibility and interfacial adsorption capacity in base oils while effectively overcoming the shortcomings of traditional oleic acid-modified materials, such as insufficient thermal stability and discontinuous lubricating films. The introduction of the branched long-chain structure enhances the steric barrier effect, inhibits secondary agglomeration of nanosheets, and ensures high dispersion of the graphene sheets. The unique interfacial activity of the quaternary ammonium salt cations strengthens adsorption to the metal substrate, resulting in a denser, more uniform, and stable lubricating film. The synergistic effect of the bifunctional groups enhances the self-healing ability of the lubricating film under high temperature and high load conditions, providing a lasting friction-reducing and protective effect for the lubrication system and broadening the material's practical application scenarios.

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

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

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

[0027] Example 1:

[0028] (1) Under a 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 was completed, the solvent was removed by rotary evaporation and purified by ethyl acetate / water (3:1, v / v) extraction and silica gel column chromatography (developing solvent: petroleum ether / ethyl acetate=8:1). The mixture was then dried under vacuum at 60 °C for 6 h to obtain terminal tertiary amine oleic acid.

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

[0030] (3) Add 1g of hydroxylated graphene to 50mL of ethanol, sonicate (power 800W, frequency 40kHz) for 60min, then add 3g of branched oleic acid containing quaternary ammonium salt and 0.03g of p-toluenesulfonic acid, heat to 70℃, reflux and stir for 8h, then transfer to a reaction vessel, purge air with argon three times, heat to 240℃ at 5℃ / min and hold for 1.5h to complete high-temperature reduction, centrifuge, wash the precipitate three times with n-hexane, and vacuum dry at 60℃ for 6h 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 trimethylbenzene phosphate (extreme pressure anti-wear agent), 1.5g of octyl diphenylamine (antioxidant), 0.3g of dodecenyl succinic acid (rust inhibitor) and 0.05g of dimethyl silicone oil (defoamer). Heat it to 65℃ and stir (800rpm) for 70-120min to obtain graphene composite rolling oil.

[0032] Example 2:

[0033] (1) Under a 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 was completed, the solvent was removed by rotary evaporation and purified by ethyl acetate / water (3:1, v / v) extraction and silica gel column chromatography (developing solvent: petroleum ether / ethyl acetate=8:1). The mixture was then dried under vacuum at 60 °C for 6 h to obtain terminal tertiary amine oleic acid.

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

[0035] (3) Add 1g of hydroxylated graphene to 50mL of ethanol, sonicate (power 800W, frequency 40kHz) for 60min, then add 5g of branched oleic acid containing quaternary ammonium salt and 0.05g of p-toluenesulfonic acid, heat to 75℃, reflux and stir for 12h, then transfer to a reaction vessel, purge air with argon three times, heat to 250℃ at 5℃ / min and hold for 2h to complete high-temperature reduction, centrifuge, wash the precipitate three times with n-hexane, and vacuum dry at 60℃ for 6h to obtain branched oleic acid modified graphene containing quaternary ammonium salt;

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

[0037] Example 3:

[0038] (1) Under a 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 was completed, the solvent was removed by rotary evaporation and purified by ethyl acetate / water (3:1, v / v) extraction and silica gel column chromatography (developing solvent: petroleum ether / ethyl acetate=8:1). The mixture was then dried under vacuum at 60 °C for 6 h to obtain terminal tertiary amine oleic acid.

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

[0040] (3) Add 1g of hydroxylated graphene to 50mL of ethanol, sonicate (power 800W, frequency 40kHz) for 60min, then add 8g of branched oleic acid containing quaternary ammonium salt and 0.08g of p-toluenesulfonic acid, heat to 80℃, reflux and stir for 16h, then transfer to a reaction vessel, purge air with argon three times, heat to 260℃ at 5℃ / min and hold for 2.5h to complete high-temperature reduction, centrifuge, wash the precipitate three times with n-hexane, and vacuum dry at 60℃ for 6h 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 shear it at high speed (12000rpm) for 40min. Then add 7.5g of trimethylbenzyl phosphate (extreme pressure anti-wear agent), 2.8g of octyl diphenylamine (antioxidant), 1g of dodecenyl succinic acid (rust inhibitor) and 0.2g of dimethyl silicone oil (defoamer). Heat it to 75℃ and stir (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 with 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 with terminal tertiary amine oleic acid;

[0046] Comparative Example 3:

[0047] The difference between Comparative Example 3 and Example 2 is that the 5g of branched oleic acid containing quaternary ammonium salt in step (3) is replaced with a mixture of 3g of terminal tertiary amine oleic acid and 2g of lauryl trimethylammonium bromide;

[0048] Comparative Example 4:

[0049] The difference between Comparative Example 4 and Example 2 is that bromododecane in step (2) is replaced with bromoethane.

[0050] Performance testing:

[0051] High-temperature four-ball friction test: Following GB / T 3142-2019 "Determination of Lubricant Load Capacity", an MXW-10 four-ball testing machine was used. After pre-running at room temperature for 10 minutes, the temperature was increased to 180℃ at a rate of 5℃ / min. The maximum non-seize load (PB value) and wear scar diameter (accurate to 0.01mm) were measured. The steel balls were made of GCr15 with 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 strip was tested, and the results are shown in Table 1.

[0053] Table 1 Performance Test Results

[0054] PB value / N Wear scar 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: Data from Table 1 suggests that the graphene modified with quaternary ammonium salt oleic acid using a specific branched structure can significantly improve lubrication performance. The chemical modification of branched oleic acid may enhance the dispersion stability of graphene in base oils through the steric hindrance effect of long-chain alkyl groups. This helps the nanosheets form a more complete lubricating film on the metal surface, thus exhibiting excellent load-bearing capacity and surface smoothness. Furthermore, it is speculated that the charge-stabilizing effect of the quaternary ammonium salt groups and the synergistic effect of the hydrophobic long chains may be key factors in achieving a stable coefficient of friction and reducing wear scar size.

[0057] Comparing the data from Example 2 and Comparative Example 1 in Table 1, it can be seen that the branched oleic acid-modified graphene containing quaternary ammonium salts has significant performance advantages over traditional oleic acid. The performance difference may stem from the weak steric hindrance effect formed by the pure oleic acid molecular chains in the base oil, and the tendency of the double bonds in oleic acid to break down at high temperatures, leading to dispersion failure under high-temperature conditions. In contrast, the long-chain quaternary ammonium salt modification in Example 2 enhances the compatibility of graphene with the base oil through its amphiphilic structure, and its cationic properties may form strong electrostatic adsorption with the metal surface. This is beneficial for constructing a continuous and stable lubrication-extreme pressure composite film, thereby improving extreme pressure anti-wear performance and surface finish.

[0058] Comparing the data from Example 2 and Comparative Example 2 in Table 1, it can be seen that the performance limitations of terminal tertiary amine oleic acid compared to the quaternary ammonium salt branched structure are evident. The tertiary amine group may lead to insufficient graphene adsorption, and it also lacks the steric stabilization effect of the branched long alkyl chain. During high-temperature rolling, the directional alignment stability of the terminal tertiary amine modifier at the metal interface is poor. In contrast, the quaternary ammonium structure of Example 2 provides continuous electrostatic repulsion through its cationic properties, and combined with the steric hindrance of the C12 alkyl chain, effectively suppresses the stacking and aggregation of nanosheets. This is the core mechanism for achieving a lower wear scar diameter.

[0059] Comparing the data from Example 2 and Comparative Example 3 in Table 1, it can be seen that physically mixed modifiers are unlikely to achieve the effect of chemical bonding modification. In the mixed system, the quaternary ammonium salt surfactant may only adhere to graphene through physical adsorption, and is prone to desorption in a shear field. In contrast, the branched oleic acid in Example 2 forms a stable complex with graphene through covalent bonds, and the synergistic effect of its intramolecular quaternary ammonium salt-alkyl chain can maintain structural integrity at high temperatures. It is speculated that this intramolecular bifunctional design has a stronger interfacial anchoring ability than physical mixtures, and can continuously provide boundary lubrication protection during dynamic rolling.

[0060] Comparing the data from Example 2 and Comparative Example 4 in Table 1, it can be seen that although Comparative Example 4 maintains the quaternary ammonium salt structure, the short-chain ethyl substitution leads to a decrease in performance, confirming the crucial influence of alkyl chain length on the modification effect. Shorter carbon chains may weaken the steric hindrance effect and reduce the dispersion stability of graphene. In contrast, the long dodecyl chain of Example 2 can form a denser molecular barrier layer, and its higher degree of conformational freedom helps maintain the continuity of the lubricating film at high temperatures. This phenomenon indicates that the quaternary ammonium salt cation center must cooperate with hydrophobic groups of appropriate chain length to fully utilize the structural advantages of the modifier.

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

Claims

1. A graphene composite rolling oil, characterized in that, By weight, it comprises the following components: 70-100 parts base oil, 0.5-1.5 parts branched oleic acid modified graphene containing quaternary ammonium salt, 2.5-7.5 parts extreme pressure anti-wear agent, 1.5-2.8 parts antioxidant, 0.3-1 part rust inhibitor and 0.05-0.2 parts defoamer; The quaternary ammonium salt-containing branched oleic acid modified graphene is obtained by thermal reduction after the carboxyl group in the quaternary ammonium salt-containing branched oleic acid reacts with the hydroxyl group on the surface of hydroxylated graphene; the quaternary ammonium salt-containing branched oleic acid is obtained by preparing terminal tertiary amine oleic acid from oleic acid and 3-(dimethylamino)-1-propanethiol through a mercapto-olefin click reaction, and then obtaining it through a quaternization reaction with bromododecane.

2. The graphene composite rolling oil according to claim 1, characterized in that, The base oil is one or a mixture of several of the following: 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 branched oleic acid containing quaternary ammonium salt to hydroxylated graphene is 1:3-8.

4. The graphene composite rolling oil according to claim 1, characterized in that, The thermal reduction atmosphere is argon, the temperature is 240-260℃, and the time is 1.5-2.5h.

5. The graphene composite rolling oil according to claim 1, characterized in that, The molar ratio of oleic acid, 3-(dimethylamino)-1-propanethiol and bromododecane 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 or a mixture of several of the following: trimethylol phosphate, tributyl phosphate, phosphite, and zinc dialkyl dithiophosphate.

7. The graphene composite rolling oil according to claim 1, characterized in that, The antioxidant is one or a mixture of several of the following: octyl diphenylamine, nonyl diphenylamine, phenyl-α-naphthylamine, and dilauryl thiodipropionate.

8. The graphene composite rolling oil according to claim 1, characterized in that, The rust inhibitor is one or a mixture of several of the following: dodecenyl succinic acid, hexadecenyl succinic acid half ester, and sorbitol monooleate.

9. The graphene composite rolling oil according to claim 1, characterized in that, The defoamer is one or a mixture of several of the following: silicone defoamers, polyether defoamers, and acrylate defoamers.

10. A method for preparing graphene composite rolling oil according to any one of claims 1-9, characterized in that, The process includes the following steps: add branched oleic acid-modified graphene containing quaternary ammonium salt to base oil, heat to 45-55℃, perform high-speed shearing for 20-40 minutes, then add extreme pressure anti-wear agent, antioxidant, rust inhibitor and defoamer in sequence, heat to 65-75℃, stir for 70-120 minutes to obtain graphene composite rolling oil.