A modified rapeseed oil-based cutting fluid and a preparation method thereof

Abstract

The application relates to the technical field of cutting fluids, and discloses a modified rapeseed oil-based cutting fluid and a preparation method thereof. The components of the modified rapeseed oil-based cutting fluid include modified rapeseed oil, an antioxidant, extreme pressure and wear-resistant agent, an emulsifier, a rust inhibitor, a pour point depressant, a defoaming agent and water; the modified rapeseed oil is obtained by compounding modification of rapeseed oil, a zinc-based zeolite imidazolate skeleton calcined derivative and dodecylboronic pinacol ester. The zinc-based zeolite imidazolate skeleton calcined derivative is used as a heterogeneous catalyst, and the dodecylboronic pinacol ester is introduced as a multifunctional modifier. The two can realize directional epoxidation and closed-loop modification of stable epoxy structure, thereby improving the oxidation stability, simultaneously optimizing the low-temperature fluidity, and solving the technical contradiction that traditional modification is stable in oxidation but poor in low-temperature performance.

Description

Technical Field

[0001] This invention relates to the field of cutting fluid technology, and in particular to a modified rapeseed oil-based cutting fluid and its preparation method. Background Technology

[0002] Currently, most cutting fluids widely used in the metalworking industry are based on mineral oil. While they possess certain lubricating and cooling properties, they suffer from the following serious problems: mineral oil is difficult to degrade, and its discharge easily causes soil and water pollution; the oil mist generated during processing irritates the respiratory tract and skin of operators, and long-term exposure may cause dermatitis or even cancer. When traditional vegetable oils (such as rapeseed oil and soybean oil) are used as base oils for cutting fluids, their unsaturated fatty acid content makes them prone to oxidation and rancidity, leading to increased viscosity and acid value, affecting cutting performance and service life. Vegetable oils are also prone to solidification at low temperatures, affecting the fluidity and spray uniformity of the cutting fluid. Although some synthetic ester-based cutting fluids are biodegradable, they are expensive, and their antioxidant properties are still not ideal.

[0003] Therefore, developing a modified rapeseed oil-based cutting fluid with improved antioxidant properties and low-temperature fluidity has significant industrial application value. Summary of the Invention

[0004] In view of this, the present invention proposes a modified rapeseed oil-based cutting fluid and its preparation method, which has strong antioxidant properties and low-temperature fluidity.

[0005] The technical solution of the present invention is implemented as follows: On the one hand, the present invention provides a modified rapeseed oil-based cutting fluid, wherein the components of the cutting fluid include: modified rapeseed oil, antioxidant, extreme pressure anti-wear agent, emulsifier, rust inhibitor, pour point depressant, defoamer and water; The modified rapeseed oil is obtained by compound modification of rapeseed oil with zinc-based zeolite imidazole ester skeleton calcination derivative and dodecyl borate pinacol ester, and the preparation method includes the following steps: Rapeseed oil, zinc-based zeolite imidazole ester skeleton calcined derivative, and dodecyl borate pinacol ester were added to a reaction vessel, mixed well, and heated to 70-75℃. Hydrogen peroxide (30wt%) was added dropwise. After the addition was complete, the reaction was kept at the temperature for 4-6 hours. After the reaction was completed, the mixture was cooled, and the zinc-based zeolite imidazole ester skeleton calcined derivative was recovered by filtration. The filtrate was washed with water and dehydrated under vacuum to obtain modified rapeseed oil.

[0006] During the heat preservation reaction stage, a preset time window and thin-layer chromatography combined with Fourier transform infrared spectroscopy (FTIR) are used to jointly determine the reaction endpoint. The reaction start time T=0 is recorded when hydrogen peroxide is completely added. The preset effective reaction range is 4 to 6 hours, and under normal operating conditions, the endpoint is preferably determined around T=5 hours.

[0007] Samples were taken at 3h, 4h, and 5h of reaction for TLC analysis. The samples were spotted onto silica gel GF.254 Thin-layer chromatography was performed using petroleum ether and ethyl acetate (8:2 volume ratio) as the developing solvent, with color development in an iodine bath. The retention factor (Rf) of the raw rapeseed oil was higher than that of the epoxidized product. When the spots corresponding to the raw material in the sample significantly faded to almost disappear (residue less than 5%), and the spot intensity no longer changed, it was preliminarily determined that the raw material was basically completely consumed.

[0008] Simultaneous FTIR infrared monitoring was employed, and a trace amount of the reaction solution was applied to the surface of an ATR diamond crystal for testing. At 3008 cm⁻¹... -1 The peak height of the carbon-carbon double bond absorption peak tends to stabilize and no longer decreases continuously, while the characteristic peak of epoxy (823–840 cm⁻¹) is also stable. -1 ) and the internal reference peak of ester carbonyl (1745 cm) -1 Once the ratio of absorption intensity reaches a stable range, and combined with the results of thin-layer chromatography, it is determined that the reaction has reached its endpoint. Heating is then stopped immediately, and the material is cooled and discharged.

[0009] The preparation method of the zinc-based zeolite imidazole ester skeleton calcined derivative is as follows: Zn(NO3)2·6H2O and 2-methylimidazolium are subjected to a hydrothermal reaction in methanol solution to obtain Zn-ZIF-8, and then Zn-ZIF-8 is calcined in an inert atmosphere at 800℃-900℃ to obtain porous carbon material ZDPC.

[0010] The mass ratio of rapeseed oil, zinc-based zeolite imidazole ester skeleton calcined derivative, and pinacol dodecyl borate ester is 100:1-3:2-5.

[0011] Specifically, the reaction principle of composite modification is as follows: Main modification / catalysis: A zinc-based zeolite imidazole ester skeleton calcined derivative (Zn-ZIF-Derived PorousCarbon, ZDPC) was used as a heterogeneous catalyst. Its high specific surface area and uniformly distributed Zn-Nx active sites can efficiently and selectively catalyze the epoxidation reaction of hydrogen peroxide with rapeseed oil double bonds, and the reaction conditions are mild, avoiding side reactions and equipment corrosion caused by strong acid catalysts.

[0012] Assisted Modification / Structural Stabilization: Pinaryl dodecyl borate (DBP) is introduced as a multifunctional modifier. Under reaction conditions, the borate ester group of DBP can undergo a ring-opening reaction with the epoxy group generated by ZDPC catalysis. Simultaneously, its long-chain dodecyl group is introduced into the oil molecule skeleton, achieving the following functions: significantly reducing the pour point of the modified oil and improving low-temperature fluidity; stabilizing the newly formed ester group by forming BOC bonds, inhibiting the ring-opening rancidity of the epoxy group at high temperatures; and the long alkyl chain itself possesses excellent lubricity, providing initial lubricity for the cutting fluid. The synergistic effect of both achieves directional epoxidation and closed-ring modification with epoxy structure stabilization, simultaneously optimizing low-temperature fluidity while improving oxidation stability, thus resolving the technical contradiction of traditional modification where "stable oxidation leads to deterioration of low-temperature performance."

[0013] Based on the above technical solutions, preferably, the components of the cutting fluid, calculated by weight, include: 70-85 parts modified rapeseed oil, 0.5-2.0 parts antioxidant, 3.7-6.2 parts extreme pressure anti-wear agent, 3.0-8.0 parts emulsifier, 1.0-3.0 parts rust inhibitor, 0.5-2.0 parts pour point depressant, 0.1-0.5 parts defoamer, and 50-70 parts water.

[0014] Based on the above technical solutions, preferably, during the preparation of the modified rapeseed oil, phosphoric acid functionalized choline ionic liquid is also added to the reaction vessel. The preparation method of the phosphoric acid functionalized choline ionic liquid is as follows: choline chloride and potassium dihydrogen phosphate are dissolved in deionized water in an equimolar ratio, reacted at 80°C for 6 hours, water is removed by rotary evaporation after the reaction, the product is washed with anhydrous ethanol and vacuum dried to obtain a colorless, transparent, viscous phosphoric acid functionalized choline ionic liquid.

[0015] Synergistic Modification and Performance Enhancement Effects of Phosphoric Acid-Functionalized Choline Ionic Liquid: The addition of phosphoric acid-functionalized choline ionic liquid ([Choline][H2PO4]) serves as both a reaction medium and a synergist. Its functions include: acting as a green reaction medium, promoting mass transfer between the heterogeneous catalyst (ZDPC) and the oil phase, and improving reaction efficiency; its phosphate groups can form an adsorption film on the metal surface, providing additional extreme pressure anti-wear and rust prevention protection during the reaction process and in the final product. It also exhibits a catalytic synergistic effect with ZDPC, which can lower the activation energy.

[0016] Based on the above technical solutions, preferably, the mass ratio of rapeseed oil to phosphoric acid functionalized choline ionic liquid is 100:3-6.

[0017] Based on the above technical solutions, preferably, the antioxidant includes one or more combinations of Irganox L135, butylated hydroxytoluene, and α-tocopherol. More preferably, the antioxidant is obtained by compounding Irganox L135 or butylated hydroxytoluene and α-tocopherol in a mass ratio of 60-70:20-30.

[0018] Irganox L135 or butylated hydroxytoluene (BHT) are primary antioxidants; they are free radical scavengers that effectively terminate oxidation chain reactions, especially at high temperatures. α-Tocopherol (vitamin E) is a hydrogen donor-type antioxidant and a secondary antioxidant; it exhibits excellent performance at medium and low temperatures and is environmentally friendly.

[0019] Based on the above technical solutions, preferably, the extreme pressure anti-wear agent includes one or more combinations of isobutylene sulfide, phosphate ester, molybdenum disulfide nanosheets, and graphene nanosheets. More preferably, the extreme pressure anti-wear agent is obtained by compounding isobutylene sulfide, phosphate ester, molybdenum disulfide nanosheets, and graphene nanosheets in a mass ratio of 40-60:30-50:3-8:2-7.

[0020] To meet processing requirements ranging from light to heavy loads, a layered lubrication protection system is designed. The reactive film layer (extreme pressure protection) uses isobutylene sulfide (SIB). Under high temperature and pressure, its active sulfur reacts with the metal surface to generate a low-shear-strength solid lubricating film such as FeS, preventing sintering. The adsorption / permeation film layer (anti-wear) uses phosphate esters. These esters are strongly adsorbed onto the metal surface through their polar groups, forming a physical barrier, and undergo a tribochemical reaction at moderate temperatures to generate a phosphate protective film. The nano-reinforcement layer (superlubricity effect) uses molybdenum disulfide nanosheets and graphene nanosheets. These layered nanomaterials act as "micro-bearings" and "sliding surfaces" in the contact area, significantly reducing the coefficient of friction.

[0021] Based on the above technical solutions, preferably, the emulsifier includes one or a combination of Tween 80 and Span 80. More preferably, the emulsifier is obtained by compounding Tween 80 and Span 80 at a mass ratio of 7-8:2-3. The advantage of using nonionic surfactants Tween 80 (hydrophilic, HLB~15) and Span 80 (lipophilic, HLB~4.3) in a compound is that there is no charge interference, it is not sensitive to hard water, and it has good compatibility.

[0022] Based on the above technical solutions, preferably, the rust inhibitor includes one or more combinations of triethanolamine, benzotriazole, and oleic acid, wherein the rust inhibitor is prepared by compounding triethanolamine, benzotriazole, and oleic acid in a mass ratio of 50-70:20-30:10-20. Triethanolamine provides an alkaline reserve and neutralizes acidic substances, benzotriazole (BTA) provides corrosion protection for copper alloys, and oleic acid forms a hydrophobic adsorption film on the metal surface; simultaneously, BTA can also chelate Cu dissolved from the workpiece or tool during processing. 2+ Fe 2+ The presence of metal ions eliminates their catalytic effect on oil oxidation, and the three work together to form a comprehensive anti-rust network.

[0023] The pour point depressant is a polymethyl methacrylate type, used to improve the pumpability and spray performance of cutting fluid at low temperatures. It changes the growth habit of wax crystals by adsorbing on the surface of wax crystals, preventing the formation of a three-dimensional network structure, thereby effectively inhibiting the tendency of CSM-RSO to form wax crystals at low temperatures and ensuring low-temperature fluidity.

[0024] Based on the above technical solutions, preferably, the defoamer is a polysiloxane-polyether block copolymer (Wenzhou Longtai Chemical Co., Ltd., LT8545), used to suppress foam generated during recycling due to stirring and spraying. This type of defoamer has high foam suppression and defoaming efficiency, and good compatibility with the components in the formulation, without affecting the stability of the emulsion.

[0025] Based on the above technical solutions, preferably, it also includes auxiliary base oil, the amount of which is 5%-15% of the mass of modified rapeseed oil, and the auxiliary base oil includes one or more combinations of palm oil trimethylolpropane ester, pentaerythritol ester, and high oleic sunflower seed oil with oleic acid content ≥85%.

[0026] Specifically, high-oleic sunflower oil, as a molecular structure stabilizer, is rich in oleic acid (a monounsaturated fatty acid), and its oxidative stability is inherently superior to that of ordinary vegetable oils. When compounded with modified rapeseed oil (CSM-RSO), its stable triglyceride structure can "dilute" residual trace unstable components in the system, thus consolidating the overall oxidative stability of the formulation. Palm oil trimethylolpropane ester (TMP ester) significantly improves the low-temperature fluidity of the formulation, making it suitable for cold environments. Pentaerythritol esters, as high-performance enhancers, provide additional protection under extreme processing conditions.

[0027] On the other hand, the present invention also provides a method for preparing a modified rapeseed oil-based cutting fluid, comprising the following steps: S1, Preparation of oil phase premix: Modified rapeseed oil and auxiliary base oil are added to the premix, heated to 65-70℃, and antioxidant, extreme pressure anti-wear agent, pour point depressant, benzotriazole and oleic acid are added in sequence. The mixture is stirred until the system is homogeneous to obtain the oil phase premix. S2, Preparation of aqueous premix: Heat water to 55-60℃, add emulsifier to water at 300-600 rpm, stir until dissolved, and add triethanolamine to adjust the pH of the system to 8.5-9.0; S3, Emulsification and Homogenization: Under conditions of 600-1000 rpm, the oil phase premix is ​​added to the aqueous phase premix at a flow rate of 1-1.5 L / min to form an O / W type primary emulsion; after the oil phase premix is ​​added, it is sheared at 10000-15000 rpm for 15-20 min, and then homogenized 1-2 times under a pressure of 25-35 MPa; S4, Post-treatment: Cool the emulsified emulsion to 35-40℃, add defoamer, stir at 100-200 rpm for 10-15 min to obtain modified rapeseed oil-based cutting fluid.

[0028] Based on the above technical solution, preferably, in step S3, before mixing the oil phase premix and the water phase premix, the temperature of the oil phase premix is ​​maintained at 60±2℃, and the temperature of the water phase premix is ​​maintained at 55±2℃, with a temperature difference of less than 5℃. Excessive temperature difference will cause the viscosity of the oil to increase instantaneously upon contact with the cold water phase, making emulsification difficult.

[0029] The modified rapeseed oil-based cutting fluid and its preparation method of the present invention have the following advantages over the prior art: This invention uses metal-organic framework derivatives (MOF-Derived Catalyst) as the main catalyst and structure directing agent, organoboroesters with long-chain alkyl groups as auxiliary structure stabilizers and low-temperature flow promoters, and introduces ionic liquid synergists to achieve selective epoxidation of unsaturated double bonds, in-situ ring-opening esterification and molecular branching of rapeseed oil in a one-step reaction.

[0030] The modified rapeseed oil-based cutting fluid prepared by this invention has the following advantages: (1) High oxidation stability: Rapeseed oil was chemically modified with ZDPC, DBP and phosphoric acid functionalized choline ionic liquid, which significantly extended the service life of the cutting fluid.

[0031] (2) Excellent low temperature performance: The modified rapeseed oil has a lower pour point, and the pour point of the cutting fluid prepared from it is reduced to below -15℃, which can adapt to a wider range of processing environments, especially suitable for use in northern winters.

[0032] (3) Excellent lubrication performance. Modified rapeseed oil has better oil film strength and lubrication effect. The cutting fluid prepared from it can reduce tool wear and improve the surface quality of the machined surface.

[0033] (4) Environmentally friendly: Based on renewable rapeseed oil, it has a high biodegradability rate and is safe for the environment and operators. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0035] The zinc-based zeolite imidazole ester skeleton calcined derivative (ZDPC) used in this invention is a self-made material. The preparation method is as follows: 2.97g Zn(NO3)2·6H2O and 3.28g 2-methylimidazole (molar ratio 1:4) are hydrothermally reacted in methanol solution (120℃, 24h) to prepare Zn-ZIF-8, and then calcined at high temperature in an inert atmosphere (850℃, 5h) to obtain porous carbon material ZDPC.

[0036] The phosphorylated choline-based ionic liquid ([Choline][H2PO4]) was prepared in-house. The preparation method was as follows: Choline chloride (Sinopharm Group) and potassium dihydrogen phosphate were dissolved in deionized water at an equimolar ratio of 1:1 (7.05 g choline chloride and 6.80 g potassium dihydrogen phosphate). The mixture was reacted at 80 °C for 6 h. After the reaction, the water was removed by rotary evaporation. The product was washed with anhydrous ethanol and dried under vacuum to obtain a colorless, transparent, viscous liquid.

[0037] Pinaryl dodecyl borate (DBP) was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., product number: D808098. The rapeseed oil is refined rapeseed oil, conforming to the first grade rapeseed oil standard of GB 1536, with an acid value (KOH) ≤0.2 mg / g, a peroxide value ≤5.0 meq / kg, and a moisture content ≤0.05%.

[0038] Example 1 This embodiment provides a method for preparing a modified rapeseed oil-based cutting fluid, including the following steps: 1. Preparation of modified rapeseed oil 1.1 Add 100.0g refined rapeseed oil, 2g ZDPC and 3.5g DBP to the reactor. Stir at 300rpm and heat to 72℃. At this temperature, slowly add 20g 30wt% hydrogen peroxide (no need to add formic acid or other carboxylic acids, simplifying the process and reducing acidic wastewater).

[0039] 1.2 After the addition is complete, keep the reaction at 72℃ for 5 hours.

[0040] 1.3 After the reaction was complete, ZDPC was recovered by filtration through a Buchner funnel (reusable). The filtrate was transferred to a separatory funnel and washed twice with 60 mL of deionized water (wash endpoint: aqueous phase pH = 7.0 ± 0.2, no H2O2 residue detected by potassium iodide-starch test paper). Each wash was shaken for 5 min, and the mixture was allowed to stand for separation. The oil phase was dehydrated under vacuum at 80℃ and -0.095 MPa for 2 h until the moisture content was <0.05% (Karl Fischer method); the composite synergistic modified rapeseed oil (CSM-RSO) was obtained: net weight approximately 98.5 g, yield approximately 98.5%.

[0041] 2. Preparation of oil phase premix Add 75.0g CSM-RSO to a premixing vessel and heat to 65℃; then add 0.8g Irganox L135, 0.3g α-tocopherol (antioxidant), 2.5g isobutylene sulfide, 2.0g phosphate ester, 0.3g nano molybdenum disulfide, 0.2g graphene nanosheets (extreme pressure anti-wear agent), 1.0g polymethyl methacrylate (pour point depressant), 0.75g benzotriazole (dissolved in 5mL isopropanol for solubilization), and 0.3g oleic acid (rust inhibitor); stir at 350rpm for 45min until the system is homogeneous and transparent.

[0042] 3. Preparation of Aqueous Premixed Solution Procedure: Heat 60.0 mL of deionized water to 58 °C; add 4.0 g Tween 80 and 1.0 g Span 80 (emulsifier), and stir at 400 rpm for 15 min until completely dissolved; add 1.8 g triethanolamine and adjust the pH to 8.8 ± 0.1.

[0043] 4. Emulsification and Homogenization Oil phase temperature: 60℃; Water phase temperature: 55℃.

[0044] Emulsification method: At 800 rpm, the oil phase was added to the aqueous phase at a flow rate of 1.2 L / min to form an O / W type primary emulsion. Then, a high-shear emulsifier was turned on and the speed was increased to 12,000 rpm for shearing for 18 min. Subsequently, it was homogenized twice by a high-pressure homogenizer (30 MPa).

[0045] 5. Post-processing and quality inspection The emulsion was slowly cooled to 40°C (cooling rate: 1.5°C / min); 0.3g of polysiloxane-polyether block copolymer defoamer was added, and the mixture was stirred at 150 rpm for 12 min.

[0046] Example 2 The difference between Example 2 and Example 1 is that in the preparation of modified rapeseed oil, 4.5g of phosphoric acid-functionalized choline ionic liquid was added in step 1.1, specifically: Preparation of modified rapeseed oil: Add 100.0g refined rapeseed oil, 2g ZDPC, 3.5g DBP, and 4.5g phosphoric acid functionalized choline ionic liquid to the reactor. Stir at 300rpm and heat to 72℃. At this temperature, slowly add 20g of 30wt% hydrogen peroxide (no need to add formic acid or other carboxylic acids, simplifying the process and reducing acidic wastewater).

[0047] The remaining steps are the same as in Example 1.

[0048] Example 3 The difference between Example 3 and Example 2 is that in step 2, when preparing the oil phase premix, 5.0g of high oleic sunflower seed oil (auxiliary base oil) was added. The high oleic sunflower seed oil and CSM-RSO were added together to the premixing vessel, and the remaining steps were the same as in Example 2.

[0049] Example 4 This embodiment provides a method for preparing a modified rapeseed oil-based cutting fluid, including the following steps: 1. Preparation of modified rapeseed oil Add 100.0g of refined rapeseed oil, 1g of ZDPC, 2g of DBP, and 3g of phosphoric acid-functionalized choline ionic liquid to the reactor. Stir at 300rpm and heat to 70℃. At this temperature, slowly add 15g of 30wt% hydrogen peroxide (no need to add formic acid or other carboxylic acids, simplifying the process and reducing acidic wastewater).

[0050] After the addition was complete, the mixture was kept at 70°C for 6 hours.

[0051] After the reaction was complete, ZDPC was recovered by filtration through a Buchner funnel (reusable). The filtrate was transferred to a separatory funnel and washed twice with 60 mL of deionized water (wash endpoint: aqueous phase pH = 7.0 ± 0.2, no H2O2 residue detected by potassium iodide-starch test paper). Each wash was shaken for 5 min, and the mixture was allowed to stand for separation. The oil phase was dehydrated under vacuum at 80℃ and -0.095 MPa for 2 h until the moisture content was <0.05% (Karl Fischer process); the composite synergistic modified rapeseed oil (CSM-RSO) was obtained: net weight approximately 98 g, yield approximately 98%.

[0052] 2. Preparation of oil phase premix: Add 70g CSM-RSO and 3.5g pentaerythritol ester (auxiliary base oil) to a premixing vessel and heat to 68℃; then add 0.35g butylated hydroxytoluene, 0.15g α-tocopherol (antioxidant), 2g sulfurized isobutylene, 1.5g phosphate ester, 0.15g nano molybdenum disulfide, 0.1g graphene nanosheets (extreme pressure anti-wear agent), 0.5g polymethyl methacrylate (pour point depressant), 0.2g benzotriazole (dissolved in 2mL isopropanol for solubilization), and 0.1g oleic acid (rust inhibitor); stir at 350rpm for 45min until the system is homogeneous and transparent.

[0053] 3. Preparation of aqueous premix: Procedure: Heat 50 mL of deionized water to 55 °C; add 2.1 g Tween 80 and 0.9 g Span 80 (emulsifier), and stir at 300 rpm for 20 min until completely dissolved; add 0.7 g triethanolamine and adjust the pH to 8.7 ± 0.2.

[0054] 4. Emulsification and homogenization: Oil phase temperature: 58℃; Water phase temperature: 53℃.

[0055] Emulsification method: At 600 rpm, the oil phase was added to the aqueous phase at a flow rate of 1.2 L / min to form an O / W type primary emulsion. Then, a high-shear emulsifier was turned on and the speed was increased to 10,000 rpm for shearing for 20 min. Subsequently, it was homogenized twice by a high-pressure homogenizer (25 MPa).

[0056] 5. Post-processing and quality inspection: The emulsion was slowly cooled to 35°C (cooling rate: 1.5°C / min); 0.1g of polysiloxane-polyether block copolymer defoamer was added, and the mixture was stirred at 100 rpm for 15 min.

[0057] Example 5 This embodiment provides a method for preparing a modified rapeseed oil-based cutting fluid, including the following steps: 1. Preparation of modified rapeseed oil Add 100.0g refined rapeseed oil, 3g ZDPC, 5g DBP, and 6g phosphoric acid functionalized choline ionic liquid to the reactor. Stir at 300rpm and heat to 75℃. At this temperature, slowly add 25g of 30wt% hydrogen peroxide (no need to add formic acid or other carboxylic acids, simplifying the process and reducing acidic wastewater).

[0058] After the addition was complete, the mixture was kept at 75°C for 4 hours.

[0059] After the reaction was complete, ZDPC was recovered by filtration through a Buchner funnel (reusable). The filtrate was transferred to a separatory funnel and washed twice with 60 mL of deionized water (wash endpoint: aqueous phase pH = 7.0 ± 0.2, no H2O2 residue detected by potassium iodide-starch test paper). Each wash was shaken for 5 min, and the mixture was allowed to stand for separation. The oil phase was dehydrated under vacuum at 80℃ and -0.095 MPa for 2 h until the moisture content was <0.05% (Karl Fischer method); the composite synergistic modified rapeseed oil (CSM-RSO) was obtained: net weight approximately 98.8 g, yield approximately 98.8%.

[0060] 2. Preparation of oil phase premix: Add 85g CSM-RSO and 12.75g palm oil trimethylolpropane ester (auxiliary base oil) to a premixing vessel and heat to 70℃; then add 1.5g Irganox L135, 0.5g α-tocopherol (antioxidant), 3g isobutylene sulfide, 2.5g phosphate ester, 0.4g nano molybdenum disulfide, 0.35g graphene nanosheets (extreme pressure anti-wear agent), 2.0g polymethyl methacrylate (pour point depressant), 0.6g benzotriazole (dissolved in 3 mL isopropanol for solubilization), and 0.4g oleic acid (rust inhibitor); stir at 350rpm for 45min until the system is homogeneous and transparent.

[0061] 3. Preparation of aqueous premix: Procedure: Heat 70 mL of deionized water to 60 °C; add 6.0 g Tween 80 and 2.0 g Span 80 (emulsifier), and stir at 600 rpm for 10 min until completely dissolved; add 1.0 g triethanolamine and adjust the pH to 8.7 ± 0.2.

[0062] 4. Emulsification and homogenization: Oil phase temperature: 62℃; Water phase temperature: 57℃.

[0063] Emulsification method: At 1000 rpm, the oil phase is added to the aqueous phase at a flow rate of 1.2 L / min to form an O / W type primary emulsion. Then, the high-shear emulsifier is turned on and the speed is increased to 15000 rpm for shearing for 15 min. Then, it is homogenized once by circulation using a high-pressure homogenizer (35 MPa).

[0064] 5. Post-processing and quality inspection: The emulsion was slowly cooled to 38°C (cooling rate: 1.5°C / min); 0.5g of polysiloxane-polyether block copolymer defoamer was added, and the mixture was stirred at 200 rpm for 10 min.

[0065] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the rapeseed oil is not modified, and in step 2, when preparing the oil phase premix, unmodified refined rapeseed oil is used to replace CSM-RSO. The rest of the contents are the same as in Example 1.

[0066] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that DBP is missing in step 1.1 of the modified rapeseed oil preparation process, while the rest of the process is the same as in Example 1.

[0067] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that in step 1.1, the amount of DBP used exceeds the limit, specifically 10g, while the rest is the same as in Example 2.

[0068] Comparative Example 4 The difference between Comparative Example 4 and Example 2 is that in step 1.1, the amount of phosphorylated choline ionic liquid used exceeds the limit, specifically 10g. The rest of the content is the same as in Example 2.

[0069] Comparative Example 5 The difference between Comparative Example 5 and Example 3 is that the amount of high oleic sunflower seed oil used is 20% of the mass of modified rapeseed oil, which exceeds the limit range. The specific amount used is 15g. The rest of the contents are the same as in Example 2.

[0070] The cutting fluid prepared according to the examples and proportions was diluted to a concentration of 5% (i.e., concentrate:water = 1:19) to prepare a cutting fluid working fluid, and then the following tests were performed.

[0071] Iodine value was tested according to GB / T 5532-2022 "Determination of Iodine Value of Animal and Vegetable Oils" to assess the residual degree of unsaturated double bonds in modified rapeseed oil. The lower the iodine value, the fewer unsaturated bonds and the better the antioxidant base. Oxidation induction period was tested according to ASTM D6186-19 standard at 180℃ and 3.5 MPa. The time (min) for the sample to undergo vigorous exothermic oxidation was recorded; the longer the time, the better the oxidation stability of the oil. Epoxy value was tested according to the hydrochloric acid-acetone method in GB / T1677-2008 "Determination of Epoxy Value of Plasticizers" to characterize the content of epoxy groups in modified rapeseed oil. A moderate epoxy value indicates a moderate epoxidation reaction, which is beneficial to the balance between lubricity and stability. System stability was tested under the condition of standing at room temperature (25℃) for 30 days. The presence of stratification, precipitation, or floating oil in the emulsion was observed, and the recovery was recorded to assess the storage stability of the cutting fluid.

[0072] Table 1 Comparison of cutting fluid antioxidant and low-temperature flow properties

[0073] Table 1 shows that the iodine values ​​of Examples 1-5 were significantly lower than those of Comparative Example 1 (unmodified rapeseed oil), indicating that the modification effectively reduced unsaturated double bonds and improved the antioxidant capacity. Examples 3 and 5 had the lowest iodine values, indicating the best antioxidant potential. Examples 3 and 5 had the longest induction periods, significantly better than Comparative Example 1, indicating that the composite modification can significantly improve thermal oxidation stability. Comparative Example 1 had the shortest induction period, proving that unmodified rapeseed oil is extremely prone to oxidation.

[0074] The lower the pour point, the better the low-temperature fluidity. Examples 3 and 5 have the lowest pour points and the best low-temperature fluidity. Comparative Examples 1 and 2 have relatively high pour points, indicating that the lack of DBP or no modification significantly worsens low-temperature fluidity. Although Comparative Examples 3 and 4 have extremely low pour points, their system stability is poor, indicating that while excessive addition of DBP or ionic liquids can improve low-temperature performance, it will disrupt the emulsion balance.

[0075] The epoxy values ​​of Examples 1-5 were moderate and stable, while the epoxy values ​​of Comparative Examples 2, 3, and 4 were too high, indicating that excessive or inappropriate epoxidation modification would lead to an excessive number of epoxy groups, which would damage the stability of the system. Examples 1-5 all showed good stability, while Comparative Example 1 (unmodified) had poor stability; Comparative Examples 3 and 4 showed obvious precipitation and floating oil, which could not be recovered; although Comparative Example 5 had a uniform appearance, there was a small amount of precipitation at the bottom of the bottle.

[0076] Table 2 Comparison of overall cutting fluid performance

[0077] As can be clearly seen from the data in Table 2, Example 3, which was modified by ZDPC, DBP and phosphoric acid functionalized choline ionic liquid, is significantly better than the unmodified Comparative Example 1 in all dimensions, including oxidation stability, lubrication performance, physical properties, emulsion characteristics, rust prevention performance and processing performance. At the same time, it also surpasses the traditional ordinary mineral oil cutting fluid in many key indicators, demonstrating the significant advantages of composite modification technology.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A modified rapeseed oil-based cutting fluid, characterized in that, The cutting fluid comprises, by weight, 70-85 parts modified rapeseed oil, 0.5-2.0 parts antioxidant, 3.7-6.2 parts extreme pressure anti-wear agent, 3.0-8.0 parts emulsifier, 1.0-3.0 parts rust inhibitor, 0.5-2.0 parts pour point depressant, 0.1-0.5 parts defoamer, and 50-70 parts water; The modified rapeseed oil is obtained by compound modification of rapeseed oil with zinc-based zeolite imidazole ester skeleton calcination derivative and dodecyl borate pinacol ester, and the preparation method includes the following steps: Rapeseed oil, zinc-based zeolite imidazole ester skeleton calcined derivative and dodecyl borate pinacol ester were added to the reaction vessel, mixed well, and heated to 70-75℃. Hydrogen peroxide was added dropwise. After the addition was completed, the reaction was kept at the temperature for 4-6 hours. After the reaction was completed, the mixture was cooled, and the zinc-based zeolite imidazole ester skeleton calcined derivative was recovered by filtration. The filtrate was washed with water and dehydrated under vacuum to obtain modified rapeseed oil. The preparation method of the zinc-based zeolite imidazole ester skeleton calcined derivative is as follows: Zn(NO3)2·6H2O and 2-methylimidazolium are subjected to a hydrothermal reaction in methanol solution to obtain Zn-ZIF-8, and then Zn-ZIF-8 is calcined in an inert atmosphere at 800℃-900℃ to obtain porous carbon material ZDPC. The mass ratio of rapeseed oil, zinc-based zeolite imidazole ester skeleton calcined derivative, pinacol dodecyl borate ester and hydrogen peroxide is 100:1-3:2-5:15-25.

2. The modified rapeseed oil-based cutting fluid as described in claim 1, characterized in that, In the preparation of the modified rapeseed oil, phosphoric acid functionalized choline ionic liquid is also added to the reaction vessel. The preparation method of the phosphoric acid functionalized choline ionic liquid is as follows: choline chloride and potassium dihydrogen phosphate are dissolved in deionized water in an equimolar ratio, reacted at 80°C for 6 hours, water is removed by rotary evaporation after reaction, the product is washed with anhydrous ethanol and vacuum dried to obtain a colorless, transparent, viscous phosphoric acid functionalized choline ionic liquid. The mass ratio of rapeseed oil to phosphoric acid-functionalized choline ionic liquid is 100:3-6.

3. The modified rapeseed oil-based cutting fluid as described in claim 2, characterized in that, The antioxidant includes one or more combinations of Irganox L135, butylated hydroxytoluene, and α-tocopherol; the extreme pressure anti-wear agent includes one or more combinations of sulfurized isobutylene, phosphate ester, nano-molybdenum disulfide, and graphene nanosheets; the emulsifier includes one or more combinations of Tween 80 and Span 80; the rust inhibitor includes one or more combinations of triethanolamine, benzotriazole, and oleic acid; the pour point depressant is a polymethyl methacrylate type pour point depressant; and the defoamer is a polysiloxane-polyether block copolymer.

4. The modified rapeseed oil-based cutting fluid as described in claim 3, characterized in that, It also includes auxiliary base oils, the amount of which is 5%-15% of the mass of modified rapeseed oil. The auxiliary base oils include one or more combinations of palm oil trimethylolpropane ester, pentaerythritol ester, and high oleic sunflower oil with an oleic acid content of ≥85%.

5. The method for preparing a modified rapeseed oil-based cutting fluid as described in claim 4, characterized in that, Includes the following steps: S1, Preparation of oil phase premix: Modified rapeseed oil and auxiliary base oil are added to the premix, heated to 65-70℃, and antioxidant, extreme pressure anti-wear agent, pour point depressant, benzotriazole and oleic acid are added in sequence. The mixture is stirred until the system is homogeneous to obtain the oil phase premix. S2, Preparation of aqueous premix: Heat water to 55-60℃, add emulsifier to water at 300-600 rpm, stir until dissolved, and add triethanolamine to adjust the pH of the system to 8.5-9.0; S3, Emulsification and Homogenization: Under conditions of 600-1000 rpm, the oil phase premix is ​​added to the aqueous phase premix at a flow rate of 1-1.5 L / min to form an O / W type primary emulsion; After the oil phase premix is ​​added, shear at 10000-15000 rpm for 15-20 min, and then homogenize at 25-35 MPa for 1-2 times. S4, Post-treatment: Cool the emulsified emulsion to 35-40℃, add defoamer, stir at 100-200 rpm for 10-15 min to obtain modified rapeseed oil-based cutting fluid.

6. The method for preparing a modified rapeseed oil-based cutting fluid as described in claim 5, characterized in that, In step S3, before mixing the oil-phase premix and the aqueous-phase premix, the temperature of the oil-phase premix is ​​kept at 60±2℃ and the temperature of the aqueous-phase premix is ​​kept at 55±2℃, with a temperature difference of less than 5℃.

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