Phosphorus-free environment-friendly water-based cutting fluid and preparation method thereof

Abstract

The invention belongs to the technical field of cutting fluid, and particularly relates to phosphorus-free environment-friendly water-based cutting fluid and a preparation method thereof. Comprising the following preparation raw materials in percentage by mass: 12-20% of a plant-based ester lubricant, 8-15% of synthetic ester, 5-10% of polyether polyol with the molecular weight of 1000-2000, 8-15% of a composite corrosion inhibitor, 4-8% of an antirust agent, 10-18% of a surfactant, 3-7% of a nano lubrication enhancer, 2-3% of a pH regulator, 1-2% of a bactericide, 1-2% of a defoaming agent and the balance of deionized water. The water eutrophication risk of phosphorus-containing compounds is thoroughly avoided in the formula, the environmental protection requirements of European Union and China are met, meanwhile, no heavy metal or nitrite exists, and environmental protection is achieved; the modified silicon dioxide nanoparticles and the synthetic ester have a synergistic effect, the extreme pressure lubricity is outstanding, the composite corrosion inhibitor is matched with the antirust agent, the antirust effect even exceeds that of a phosphorus-containing formula through the synergistic effect, the core lubricant is a plant-based ester lubricant, the biodegradation rate is larger than 90%, and the stability is high by modifying the silicon dioxide nanoparticles. Agglomeration and failure are not easily caused.

Description

Technical Field

[0001] The invention belongs to the technical field of cutting fluids, and in particular relates to a phosphorus-free and environmentally friendly water-based cutting fluid and a preparation method thereof. Background Art

[0002] During the metal cutting process, cutting fluid plays a key role in lubrication, cooling, rust prevention and cleaning. Traditional cutting fluids usually contain ingredients such as phosphates, nitrites, and chlorine-based extreme pressure agents. Although they can provide good processing performance, they have the following problems. 1. Environmental pollution: Phosphorus-containing compounds can easily lead to eutrophication of water bodies, and nitrites are carcinogenic, endangering the health of workers and difficult to degrade. 2. High cost of waste liquid treatment: Cutting fluids containing phosphorus, sulfur, and chlorine are classified as hazardous wastes, and the treatment costs are high. 3. Performance limitations: Traditional phosphorus-free cutting fluids, such as borate type, have insufficient rust prevention, especially in the processing of cast iron and aluminum alloys, which can easily cause rust. The lubricity of water-based cutting fluids is usually not as good as oil-based products, which leads to increased tool wear.

[0003] Environmentally friendly water-based cutting fluids are currently gaining popularity in the market. However, existing environmentally friendly cutting fluids still have the following issues: Relying on a single corrosion inhibitor (e.g., molybdate alone), resulting in rust prevention failure when machining high-hardness materials. Adding sulfur- or chlorine-containing extreme pressure agents to enhance lubricity defeats the primary environmental protection objective. Nano-additives (e.g., graphene and MoS) have poor dispersion stability and are prone to aggregation and failure. Summary of the Invention

[0004] The present invention aims to provide a phosphorus-free and environmentally friendly aqueous cutting fluid and a preparation method thereof, aiming to solve the technical problems in the background technology.

[0005] To achieve the above-mentioned objectives, the present invention provides a phosphorus-free and environmentally friendly water-based cutting fluid and a preparation method thereof, comprising the following raw materials in parts by mass: the following raw materials in percentage by mass: 12-20% of a plant-based ester lubricant, 8-15% of a synthetic ester, 5-10% of a polyether polyol with a molecular weight of 1000-2000, 8-15% of a composite corrosion inhibitor, 4-8% of a rust inhibitor, 10-18% of a surfactant, 3-7% of a nano-lubrication enhancer, 2-3% of a pH regulator, 1-2% of a bactericide, 1-2% of a defoamer, and the balance being deionized water; the nano-lubrication enhancer is silica nanoparticles surface-treated with an organic silane coupling agent, and the composite corrosion inhibitor is a mixture of 5-8% of an organic carboxylate and 3-7% of a molybdate complex.

[0006] The steps of surface treating silica nanoparticles with an organosilane coupling agent are as follows: first, drying the nanosilica at high temperature to remove physically adsorbed water and prevent subsequent hydrolysis and inactivation of the organosilane coupling agent; second, dissolving the organosilane coupling agent in an anhydrous ethanol solution, with the ratio of the organosilane coupling agent to the anhydrous ethanol solution being 1:7-9; then adding the nanosilica to the mixed solution, stirring the mixture in a planetary mixer at a speed of 200-500 rpm for 1-2 hours, and then baking until the anhydrous ethanol solution is completely volatilized, collecting the remaining solid matter, and obtaining modified nanosilica treated with the organosilane coupling agent. Silazane is preferably used as the organosilane coupling agent.

[0007] Optionally, the organic carboxylate is one or a mixture of several of triethanolamine sebacate, triethanolamine adipate and diethanolamine maleate.

[0008] Optionally, the molybdate complex is composed of sodium molybdate and thiomolybdate in a mass ratio of 2:1 to 4:1. Specifically, the triple corrosion inhibition system of organic carboxylate + molybdate + borate and rust inhibitor achieves or even exceeds the rust prevention effect of phosphorus-containing formulations through synergistic effects.

[0009] Optionally, the plant-based ester lubricant is epoxy soybean oil modified ester or epoxy palmitoleate octyl ester.

[0010] Optionally, the synthetic ester is one or a mixture of pentaerythritol oleate, trimethylolpropane oleate and neopentyl glycol dioleate. The core lubricant is a plant-based ester lubricant with a biodegradability of >90%.

[0011] Optionally, the rust inhibitor is one or a mixture of lauric borate, oleic borate and dodecyl borate.

[0012] Optionally, the pH regulator is monoethanolamine; the bactericide is an isothiazolinone derivative; and the defoamer is polyether-modified silicone oil. The monoethanolamine regulating system combined with the bactericide effectively inhibits bacterial growth (bacteriostasis rate > 99%).

[0013] Optionally, the surfactant is a mixture of fatty alcohol polyoxyethylene ether and sodium salt of dioctyl sulfosuccinate.

[0014] Optionally, a method for preparing a phosphorus-free environmentally friendly aqueous cutting fluid comprises the following steps:

[0015] S1: Add plant-based ester lubricant, synthetic ester and polyether polyol to a reactor and stir at 60-80°C and 300-500 rpm for 10-15 minutes until completely homogenized and a transparent oil phase is formed; add surfactant and continue stirring for 10 minutes until dissolved to obtain a pre-emulsified oil phase;

[0016] S2: In another reaction kettle, deionized water is added, and then an organic carboxylate, a molybdate complex, and a rust inhibitor are added in sequence. The mixture is stirred at a temperature of 50-60° C. and a stirring speed of 400-600 rpm for 10-15 minutes until it is completely transparent. Finally, part of a pH regulator is added to adjust the pH to 8.5-9.0 to obtain an aqueous phase.

[0017] S3 disperses the nano-silica particles and deionized water under ultrasonic conditions of 40kHz for 30 minutes to obtain a nanosuspension; the main purpose is to break the agglomeration of nanoparticles and improve the dispersibility and stability of the system.

[0018] In step S4, the pre-emulsified oil phase is slowly added dropwise to the aqueous phase, with continuous stirring at 55-60°C and 500-700 rpm. After homogenization, the nano-lubricant enhancer is added and stirring is maintained for 10 minutes. The remaining pH adjuster, fungicide, and defoamer are then added in sequence. Stir for 30 minutes until completely homogenized, and then filtered to obtain a phosphorus-free, environmentally friendly aqueous cutting fluid. In step S3, the pH is adjusted to 9-9.5 and the viscosity is controlled to 20-30 cSt at 25°C.

[0019] The above one or more technical solutions in the phosphorus-free environmentally friendly water-based cutting fluid and preparation method thereof provided by the embodiment of the present invention have at least one of the following technical effects: the formula of the present invention completely avoids the risk of eutrophication of water bodies caused by phosphorus compounds, complies with the environmental protection requirements of the European Union and China, and at the same time does not contain heavy metals or nitrites, and is environmentally friendly; modified silica nanoparticles have a synergistic effect with synthetic esters, and have outstanding extreme pressure lubricity. The use of composite corrosion inhibitors in combination with rust inhibitors can even surpass the anti-rust effect of phosphorus-containing formulas through synergistic effects. The core lubricant is a plant-based ester lubricant with a biodegradation rate of >90%. By modifying the silica nanoparticles, the fluid has high stability and is not easy to agglomerate and fail. DETAILED DESCRIPTION

[0020] The present invention will be further described below with reference to the examples, but the embodiments of the present invention are not limited thereto.

[0021] Example 1

[0022] A phosphorus-free, environmentally friendly water-based cutting fluid comprises the following raw materials in percentage by mass: 12% of a plant-based ester lubricant, 15% of a synthetic ester, 8% of a polyether polyol with a molecular weight of 1000-2000, 10% of a composite corrosion inhibitor, 6% of a rust inhibitor, 14% of a surfactant, 4% of a nano-lubrication enhancer, 2% of a pH regulator, 2% of a bactericide, 2% of a defoamer, and 25% of deionized water; the nano-lubrication enhancer is silicon dioxide nanoparticles surface-treated with an organic silane coupling agent, and the composite corrosion inhibitor is a mixture of 5% of an organic carboxylate and 5% of a molybdate complex.

[0023] The organic carboxylate is triethanolamine sebacate; the molybdate complex is composed of a mixture of sodium molybdate and thiomolybdate in a mass ratio of 2:1; the plant-based ester lubricant is an epoxy soybean oil-modified ester; the synthetic ester is pentaerythritol oleate; the rust inhibitor is lauric acid borate; the pH adjuster is monoethanolamine; the fungicide is an isothiazolinone derivative; the defoamer is a polyether-modified silicone oil; and the surfactant is a mixture of fatty alcohol polyoxyethylene ether and sodium dioctyl sulfosuccinate.

[0024] Phosphorus-free and environmentally friendly water-based cutting fluid and its preparation method, comprising the following steps:

[0025] S1: Add plant-based ester lubricant, synthetic ester and polyether polyol to a reactor and stir at 60°C and 300 rpm for 10 minutes until completely homogenized to form a transparent oil phase; add surfactant and continue stirring for 10 minutes until dissolved to obtain a pre-emulsified oil phase;

[0026] S2: In another reaction kettle, deionized water is added, and then organic carboxylate, molybdate complex, and rust inhibitor are added in sequence. The mixture is stirred at 400 rpm for 10 min at a temperature of 50°C until it is completely transparent. Finally, part of the pH regulator is added to adjust the pH to 8.5 to obtain an aqueous phase.

[0027] S3 disperses the nano-silica particles and deionized water under ultrasonic conditions at 40 kHz for 30 min to obtain a nano-suspension;

[0028] S4 slowly adds the pre-emulsified oil phase dropwise to the water phase, continuously stirs at 500 rpm at a temperature of 55°C, adds the nanosuspension after homogenization, maintains stirring for 10 minutes, then adds the remaining pH adjuster, bactericide and defoamer in sequence, stirs for 30 minutes until completely uniform, adjusts the pH to 9, and controls the viscosity to 20 cSt at 25°C, and then filters to obtain a phosphorus-free and environmentally friendly water-based cutting fluid.

[0029] Example 2

[0030] A phosphorus-free, environmentally friendly water-based cutting fluid comprises the following raw materials in percentage by mass: 16% of a plant-based ester lubricant, 8% of a synthetic ester, 5% of a polyether polyol with a molecular weight of 1000-2000, 15% of a composite corrosion inhibitor, 4% of a rust inhibitor, 18% of a surfactant, 3% of a nano-lubrication enhancer, 3% of a pH regulator, 1% of a bactericide, 2% of a defoamer, and 25% of deionized water; the nano-lubrication enhancer is silicon dioxide nanoparticles surface-treated with an organic silane coupling agent, and the composite corrosion inhibitor is a mixture of 8% of an organic carboxylate and 7% of a molybdate complex.

[0031] The organic carboxylate is triethanolamine adipate; the molybdate complex is a mixture of sodium molybdate and thiomolybdate in a mass ratio of 3:1; the plant-based ester lubricant is epoxidized octyl palmitoleate; the synthetic ester is trimethylolpropane oleate; the rust inhibitor is oleic acid borate; the pH adjuster is monoethanolamine; the fungicide is an isothiazolinone derivative; the defoamer is polyether-modified silicone oil; and the surfactant is a mixture of fatty alcohol polyoxyethylene ether and sodium dioctyl sulfosuccinate.

[0032] Phosphorus-free and environmentally friendly water-based cutting fluid and its preparation method, comprising the following steps:

[0033] S1: Add plant-based ester lubricant, synthetic ester and polyether polyol to a reactor and stir at 70°C and 400 rpm for 12 minutes until completely homogenized to form a transparent oil phase; add surfactant and continue stirring for 10 minutes until dissolved to obtain a pre-emulsified oil phase;

[0034] S2: In another reaction kettle, deionized water was added, and then organic carboxylate, molybdate complex, and rust inhibitor were added in sequence. The mixture was stirred at 500 rpm for 12 minutes at a temperature of 55°C until it was completely transparent. Finally, part of the pH regulator was added to adjust the pH to 5.8 to obtain an aqueous phase.

[0035] S3 disperses the nano-silica particles and deionized water under ultrasonic conditions at 40 kHz for 30 min to obtain a nano-suspension;

[0036] S4 slowly adds the pre-emulsified oil phase dropwise to the water phase, continuously stirs at 600 rpm at a temperature of 55°C, adds the nanosuspension after homogenization, maintains stirring for 10 minutes, then adds the remaining pH adjuster, bactericide and defoamer in sequence, stirs for 30 minutes until completely uniform, adjusts the pH to 9.2, and controls the viscosity to 25 cSt at 25°C, and then filters to obtain a phosphorus-free and environmentally friendly water-based cutting fluid.

[0037] Example 3

[0038] A phosphorus-free, environmentally friendly water-based cutting fluid comprises the following raw materials in percentage by mass: 20% of a plant-based ester lubricant, 12% of a synthetic ester, 10% of a polyether polyol with a molecular weight of 1000-2000, 8% of a composite corrosion inhibitor, 8% of a rust inhibitor, 10% of a surfactant, 5% of a nano-lubrication enhancer, 2% of a pH regulator, 2% of a bactericide, 1% of a defoamer, and 22% of deionized water; the nano-lubrication enhancer is silicon dioxide nanoparticles surface-treated with an organic silane coupling agent, and the composite corrosion inhibitor is a mixture of 5% of an organic carboxylate and 3% of a molybdate complex.

[0039] The organic carboxylate is one or a mixture of several maleic acid diethanolamine salts; the molybdate complex is composed of a mixture of sodium molybdate and thiomolybdate in a mass ratio of 4:1; the plant-based ester lubricant is an epoxy soybean oil-modified ester; the synthetic ester is neopentyl glycol dioleate; the rust inhibitor is dodecyl borate; the pH adjuster is monoethanolamine; the bactericide is an isothiazolinone derivative; the defoamer is a polyether-modified silicone oil; and the surfactant is a mixture of fatty alcohol polyoxyethylene ether and sodium dioctyl sulfosuccinate.

[0040] Phosphorus-free and environmentally friendly water-based cutting fluid and its preparation method, comprising the following steps:

[0041] S1: Add plant-based ester lubricant, synthetic ester and polyether polyol to a reactor and stir at 80°C and 500 rpm for 15 minutes until completely homogenized to form a transparent oil phase; add surfactant and continue stirring for 10 minutes until dissolved to obtain a pre-emulsified oil phase;

[0042] S2: In another reaction kettle, deionized water was added, and then organic carboxylate, molybdate complex, and rust inhibitor were added in sequence. The mixture was stirred at 60°C and 600 rpm for 15 minutes until it was completely transparent. Finally, part of the pH regulator was added to adjust the pH to 9.0 to obtain an aqueous phase.

[0043] S3 disperses the nano-silica particles and deionized water under ultrasonic conditions at 40 kHz for 30 min to obtain a nano-suspension;

[0044] S4 slowly adds the pre-emulsified oil phase dropwise to the water phase, continuously stirs at 700 rpm at a temperature of 55-60°C, adds the nanosuspension after homogenization, maintains stirring for 10 minutes, then adds the remaining pH adjuster, bactericide and defoamer in sequence, stirs for 30 minutes until completely uniform, adjusts the pH to 9.5, and controls the viscosity to 30 cSt at 25°C, and then filters to obtain a phosphorus-free and environmentally friendly water-based cutting fluid.

[0045] Comparative Example 1

[0046] The method is the same as Example 1, except that the composite corrosion inhibitor is replaced by only organic carboxylate, and the organic carboxylate is triethanolamine sebacate.

[0047] Comparative Example 2

[0048] The method is the same as Example 1, except that the composite corrosion inhibitor is replaced by a molybdate complex, wherein the molybdate complex is composed of sodium molybdate and thiomolybdate mixed in a mass ratio of 2:1.

[0049] Comparative Example 3

[0050] The same as Example 1, except that the composite corrosion inhibitor is replaced by only phosphate ester.

[0051] Comparative Example 4

[0052] The method is the same as Example 1, except that the nano-lubricity enhancer, which is silica nanoparticles surface-treated with an organic silane coupling agent, is replaced with untreated silica nanoparticles of the same particle size.

[0053] Comparative Example 5

[0054] The same as Example 1, except that the nano-lubricating enhancer is replaced by sulfurized fatty acid ester. Sulfurized fatty acid ester is a sulfur-containing extreme pressure agent.

[0055] Comparative Example 6

[0056] Same as Example 1, except that the nano-lubricating enhancer is removed and the mass percentage is increased to the plant-based ester lubricant.

[0057] Comparative Example 7

[0058] The same as Example 1, except that the rust inhibitor lauric borate is replaced by sodium phosphate.

[0059] The cutting fluids prepared in Examples 1-3 and Comparative Examples 1-7 were subjected to the following tests:

[0060] The cast iron rust prevention test is conducted at a temperature of 35±2°C and a humidity of 90% for 48 hours. HT200 gray cast iron is used as the test piece. The test piece is immersed in diluted cutting fluid, removed, and tilted to drain. The test piece is placed in a damp heat chamber, ensuring that no condensation drips from the surface. After the test period, the test piece is removed and visually inspected for rust. The grade is assessed according to GB / T6144-2010.

[0061] Lubricity is tested according to the four-ball test, and the coefficient of friction and tool wear are tested in accordance with GB / T 3142-2019.

[0062] Nanoparticle dispersibility (precipitation rate) is tested as follows: Dilute the cutting fluid to a working concentration (e.g., 5%) and allow to stand for 7 days. Collect the supernatant and measure the particle size distribution using a laser particle size analyzer (e.g., Malvern Zetasizer). Calculate the precipitation rate: Precipitation rate = (initial nanoparticle concentration - concentration after 7 days) / initial concentration × 100%. A precipitation rate of ≤5% indicates effective coupling agent treatment.

[0063] Environmentally friendly test: Chemical oxygen demand (COD, GB / T 11914-1989) Method: Potassium dichromate method (CODcr). Add potassium dichromate and silver sulfate catalyst to the diluted cutting fluid and digest for 2 hours at 150°C. Titrate the remaining oxidant and calculate the COD value (unit: mg / L). Limit: Generally required to be ≤ 3000 mg / L (lower than the hazardous waste standard of 10,000 mg / L). 2. Total phosphorus (GB / T 11893-1989) Method: Ammonium molybdate spectrophotometry. After sample digestion, measure absorbance at a wavelength of 710 nm and compare to a standard curve. Limit: Phosphorus-free formulations require a total phosphorus ≤ 0.5 mg / L. The following data were obtained, as shown in Table 1.

[0064] Table 1

[0065]

[0066] It can be seen from Example 1 and Comparative Examples 1-7 that Examples 1-3 use a composite corrosion inhibitor, such as an organic carboxylate + molybdate composite system, and the rust prevention performance of cast iron / aluminum alloy is better than that of a single corrosion inhibitor in all aspects. Comparing Example 1 and Comparative Example 4, the precipitation rate of silica nanoparticles treated with a silane coupling agent is significantly lower than that of untreated silica nanoparticles. It can be seen from Example 1 and Comparative Examples 3, 5, and 7 that the comparative example adds phosphorus / sulfur pollutants, which does not meet environmental protection requirements. At the same time, it can be seen from Example 1 and Comparative Example 6 that silica nanoparticles have an improving effect on tool wear. The above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A phosphorus-free environmentally friendly water-based cutting fluid, characterized in that: The preparation comprises the following raw materials in percentage by mass: 12-20% of plant-based ester lubricant, 8-15% of synthetic ester, 5-10% of polyether polyol with a molecular weight of 1000-2000, 8-15% of composite corrosion inhibitor, 4-8% of rust inhibitor, 10-18% of surfactant, 3-7% of nano-lubrication enhancer, 2-3% of pH regulator, 1-2% of bactericide, 1-2% of defoamer, and the balance is deionized water; the nano-lubrication enhancer is silicon dioxide nanoparticles surface-treated with an organic silane coupling agent, and the composite corrosion inhibitor is a mixture of 5-8% of organic carboxylate and 3-7% of molybdate complex.

2. The phosphorus-free environmentally friendly water-based cutting fluid according to claim 1, characterized in that: The organic carboxylate is one or a mixture of several of triethanolamine sebacate, triethanolamine adipate and diethanolamine maleate.

3. The phosphorus-free environmentally friendly water-based cutting fluid according to claim 1, characterized in that: The molybdate complex is composed of sodium molybdate and thiomolybdate mixed in a mass ratio of 2:1 to 4:

1.

4. The phosphorus-free environmentally friendly water-based cutting fluid according to claim 1, characterized in that: The plant-based ester lubricant is epoxy soybean oil modified ester or epoxy palmitoleate octyl ester.

5. The phosphorus-free environmentally friendly water-based cutting fluid according to claim 1, characterized in that: The synthetic ester is one or a mixture of pentaerythritol oleate, trimethylolpropane oleate and neopentyl glycol dioleate.

6. The phosphorus-free environmentally friendly water-based cutting fluid according to claim 1, characterized in that: The rust preventive agent is one or a mixture of lauric borate, oleic borate and dodecyl borate.

7. The phosphorus-free environmentally friendly water-based cutting fluid according to claim 1, characterized in that: The pH regulator is monoethanolamine; the bactericide is an isothiazolinone derivative; and the defoaming agent is polyether-modified silicone oil.

8. The phosphorus-free environmentally friendly water-based cutting fluid according to claim 1, characterized in that: The surfactant is a mixture of fatty alcohol polyoxyethylene ether and dioctyl sulfosuccinate sodium salt.

9. The method for preparing the phosphorus-free environmentally friendly aqueous cutting fluid according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1: Add plant-based ester lubricant, synthetic ester and polyether polyol to a reactor and stir at 60-80°C and 300-500 rpm for 10-15 minutes until completely homogenized and a transparent oil phase is formed; add surfactant and continue stirring for 10 minutes until dissolved to obtain a pre-emulsified oil phase; S2: In another reaction kettle, deionized water is added, and then an organic carboxylate, a molybdate complex, and a rust inhibitor are added in sequence. The mixture is stirred at a temperature of 50-60° C. and a stirring speed of 400-600 rpm for 10-15 minutes until it is completely transparent. Finally, part of a pH regulator is added to adjust the pH to 8.5-9.0 to obtain an aqueous phase. S3 disperses the nano-silica particles and deionized water under ultrasonic conditions at 40 kHz for 30 min to obtain a nano-suspension; S4 slowly adds the pre-emulsified oil phase to the water phase, continuously stirs at 500-700 rpm at a temperature of 55-60°C, adds the nanosuspension after homogenization, maintains stirring for 10 minutes, and then adds the remaining pH regulator, bactericide and defoamer in sequence, stirs for 30 minutes until completely uniform, and then filters to obtain a phosphorus-free and environmentally friendly water-based cutting fluid.

10. The method for preparing the phosphorus-free environmentally friendly water-based cutting fluid according to claim 9, characterized in that: In step S3, the pH is adjusted to 9-9.5 and the viscosity is controlled to 20-30 cSt at 25°C.

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