Production method of environment-friendly long-acting cleaning line cutting fluid

Abstract

The present application belongs to the technical field of metal processing fluid, and discloses a production method of an environmentally-friendly long-acting clean line cutting fluid. The method uses waste edible oil as raw material, and after pretreatment, branched fatty acids are prepared through a deoxygenation-cracking-isomerization coupling reaction and a carbonylation step, and then high-stability bio-ester base oil is generated by directional esterification of the branched fatty acids with neopentyl polyol without beta-hydrogen; intelligent slow-release antioxidant microcapsules, compounded surfactants and functional additives are compounded to form a water-based microemulsion. Through molecular structure reconstruction, intelligent material integration and green process coupling, the present application solves the industry pain points of poor long-term stability, insufficient cleaning performance and high environmental risk of plant oil-based cutting fluid, and the obtained cutting fluid has excellent oxidation stability, strong hard water resistance, good cleaning performance, long-term stable pH, high biodegradation rate, can be continuously used for 180 days without replacement, and has environmental friendliness and high performance.

Description

Technical Field

[0001] This invention belongs to the field of metalworking fluid technology and relates to a production method of an environmentally friendly, long-lasting, clean cutting fluid. Background Technology

[0002] In the context of the coordinated development of modern precision manufacturing and green manufacturing, metalworking fluids, as key process media for ensuring machining accuracy, extending tool life, and improving workpiece surface quality, are receiving increasing attention for their performance and environmental friendliness. Cutting fluids, as an important branch of metalworking fluids, not only need to possess excellent lubrication, cooling, rust prevention, and cleaning functions, but also need to meet increasingly stringent requirements for ecological safety and sustainable development.

[0003] Vegetable oil-based cutting fluids made from renewable resources are gradually becoming a research hotspot to replace traditional mineral oil-based products due to their advantages such as good biodegradability, low toxicity, and wide availability. The preparation of high-performance bio-ester base oils using low-value biomass resources such as waste cooking oil further expands their application prospects and environmental value.

[0004] Several existing technologies attempt to convert waste cooking oil into bio-lubricating base oils such as fatty acid methyl esters or polyol esters through transesterification, hydrogenation, or catalytic cracking, and then use these to formulate vegetable oil-based cutting fluids. These methods achieve resource recycling to a certain extent and initially demonstrate good lubrication performance and environmental compatibility. This technological approach not only addresses the environmental pollution problem of waste cooking oils but also provides a feasible path for the cutting fluid industry's low-carbon transformation, embodying a typical paradigm of the cross-integration of catalytic chemistry and the circular economy.

[0005] However, vegetable oil molecules generally contain unsaturated fatty acid chains. Their carbon-carbon double bonds are highly susceptible to free radical chain oxidation reactions under the influence of multiple factors, including heat, oxygen, metal ions, and microorganisms, generating degradation products such as peroxides, small molecules like aldehydes and ketones, and short-chain carboxylic acids. This process not only leads to an abnormally high viscosity and darkened color, but more importantly, the resulting organic acids significantly lower the pH value, causing rancidity. This, in turn, corrodes machine tool components, disrupts emulsion stability, and promotes the growth of microorganisms to form slime, severely impacting processing cleanliness and equipment operational reliability. Summary of the Invention

[0006] To achieve the aforementioned objectives, this invention provides a method for producing an environmentally friendly, long-lasting, cleaning-grade cutting fluid. This method uses waste cooking oil as the initial raw material and employs a multi-stage catalytic reforming process to directionally construct a branched polyol ester molecular structure with high oxidation stability, excellent lubrication performance, and strong resistance to microbial degradation. Combined with a functionalized surfactant system and intelligent slow-release antioxidant microcapsule technology, this results in a water-based cutting fluid formulation that is environmentally friendly, has long-lasting stability, and excellent cleaning capabilities. This invention addresses the core defects of vegetable oil-based cutting fluids, such as easy oxidation and rancidity, emulsification instability, and microbial growth, from the molecular structure design perspective, while simultaneously achieving high-value recycling of waste oil resources.

[0007] The production method of this invention includes the following steps: First, waste edible oil is pretreated to remove moisture, free fatty acids, solid impurities, and metal ions; then, under the action of a specific catalyst, triglyceride macromolecules are converted into a mixture of C8-C18 medium- and short-chain fatty acids containing branched chains through a deoxygenation-cracking-isomerization coupled reaction pathway; subsequently, the obtained fatty acids are subjected to a directed esterification reaction with a selected polyol in the presence of an esterification catalyst to generate a bio-ester base oil whose main components are 2-ethylhexyl-2-methyl-1,3-propanediol monoester or neopentyl polyol ester; then, the bio-ester base oil is mixed with a compound surfactant, intelligent slow-release antioxidant microcapsules, rust inhibitor, defoamer, and deionized water in a specific ratio, and the mixture is homogenized and emulsified to obtain the final product.

[0008] The pretreatment steps specifically include: heating the waste cooking oil to 60°C, adding a mixture of 0.5% activated carbon and 1.0% diatomaceous earth adsorbent at a stirring rate of 300 rpm, stirring at a constant temperature for 30 minutes, and then filtering; the filtrate enters a molecular distillation apparatus and is dehydrated and deacidified under conditions of an absolute pressure of 5 Pa, an evaporation surface temperature of 180°C, and a condensation surface temperature of 40°C, so that the moisture content is lower than 0.05% and the acid value is reduced to below 1.0 mg KOH / g.

[0009] In a preferred embodiment of the present invention, the deoxygenation-cracking-isomerization coupled reaction is carried out in a fixed-bed continuous reactor at a reaction temperature of 320°C, a hydrogen partial pressure of 3.0 MPa, and a liquid hourly space velocity of 1.5 h⁻¹. -1 The catalyst used is a supported bifunctional catalyst, with a mesoporous ZSM-5 molecular sieve as the support and a specific surface area of ​​350 m². 2The catalyst has a pore size distribution concentrated in the range of 2.5-3.5 nm. The active components are nickel and molybdenum in a mass ratio of 3:1, with a total loading of 8.0%. Nickel is dispersed as NiO, and molybdenum exists as MoO3. After reduction with hydrogen at 500℃, a Ni-Mo alloy active phase is formed. This catalyst promotes selective CO bond cleavage in triglycerides, releasing the glycerol backbone and simultaneously decarboxylating and deoxygenating long-chain fatty acids to generate primary products mainly composed of n-alkanes. Simultaneously, the Bronsted acid centers of the molecular sieve induce carbocation rearrangement, causing methyl migration in some n-chains to form isoalkanes with α- or β-branchs. These isoalkanes are then converted into branched fatty acids in subsequent oxidation steps.

[0010] The preparation of the branched fatty acids also includes a carbon monoxide-assisted carbonylation step: the above-mentioned pyrolysis products are passed into a second reactor and reacted for 2 hours at 180°C and 2.0 MPa in the presence of a palladium-tin bimetallic catalyst (Pd:Sn molar ratio of 4:1, support of γ-Al2O3), so that the terminal olefins or alkanes undergo carbonyl insertion to generate carboxylic acids with branched structures. The degree of branching (i.e., the number of branched carbon atoms per 100 carbon atoms) is controlled between 8 and 12, and the iodine value is less than 5 gI2 / 100 g, which is significantly better than that of traditional hydrogenated saturated vegetable oils (iodine value is usually higher than 80).

[0011] As one of the core innovations of this invention, the directional esterification reaction uses neopentyl polyol as the alcohol component, specifically 2-methyl-2-propyl-1,3-propanediol or trimethylolpropane, whose molecular structure does not contain β-hydrogen atoms, fundamentally blocking the pathway of reverse alcoholysis or thermal decomposition of ester molecules under high temperature or alkaline conditions. The esterification reaction is carried out under nitrogen protection at a reaction temperature of 190°C, with p-toluenesulfonic acid as the catalyst at 0.8% of the fatty acid mass, for a reaction time of 4 hours, achieving an esterification conversion rate higher than 98%. The resulting bio-ester base oil has a pour point below -25°C and a kinematic viscosity of 25-35 mmHg at 40°C. 2 / s, the oxidation induction period (PDSC method, 220℃) exceeds 60min, which is much longer than that of unmodified rapeseed oil methyl ester (usually less than 10min).

[0012] The compound surfactant is composed of nonionic and anionic surfactants in a mass ratio of 3:1. The nonionic component is polyoxyethylene (10) lauryl ether with an HLB value of 13.5; the anionic component is sodium dodecylbenzene sulfonate. The two components work synergistically to form a stable microemulsion system with uniform particle size, an absolute Zeta potential greater than 40 mV, and an average particle size of 80-120 nm. It shows no demulsification or stratification after standing in hard water (total calcium and magnesium ion concentration of 500 mg / L) for 30 days.

[0013] As a key technical feature of this invention, the intelligent sustained-release antioxidant microcapsules are composed of a core material and a wall material. The core material is a complex of the hindered phenolic antioxidant Irganox 1076 and dilauryl thiodipropionate in a mass ratio of 2:1; the wall material is PLGA, with a lactic acid to glycolic acid molar ratio of 75:25 and a molecular weight of 45,000. The microcapsules are prepared by a double emulsification-solvent evaporation method, with an average particle size of 2-5 μm and an encapsulation efficiency of over 90%. During the use of the cutting fluid, when the pH of the system drops below 6.5 due to the generation of trace organic acids, the PLGA wall material undergoes accelerated hydrolysis, triggering a pulsed release of the antioxidant, thereby inhibiting free radical chain growth in the early stages of rancidity and achieving on-demand responsive protection.

[0014] The rust inhibitor is a benzotriazole derivative, specifically 1-hydroxybenzotriazole, added at 0.3% of the total mass of the cutting fluid; the defoamer is polyether-modified silicone oil with a kinematic viscosity of 1000 mmHg at 25°C. 2 / s, with an addition amount of 0.1%. All components were emulsified in a high-speed shear emulsifier at 60°C and 10,000 rpm for 30 min to obtain a semi-transparent microemulsion with a solid content of 8%.

[0015] In another preferred embodiment of the present invention, the polyol can be replaced with pentaerythritol, resulting in a tetraester product with higher thermal stability and lubricating film strength, suitable for heavy-duty cutting scenarios. In this case, the esterification reaction temperature is adjusted to 210°C, the catalyst is replaced with tetrabutyl titanate at a dosage of 0.5%, and the reaction time is extended to 5 hours. The resulting base oil has a kinematic viscosity of 40-50 mmHg at 40°C. 2 / s, the PB value of the four-ball machine test reached 850N, which meets the requirements of ISO12922 standard for heavy-duty processing fluid.

[0016] The hydrogen in the catalytic reforming step can be partially obtained from the reforming of light hydrocarbons generated by the cracking of waste edible oil, achieving self-sufficiency of hydrogen within the reaction system, reducing dependence on external high-pressure hydrogen, and improving process safety and economy. After purification by pressure swing adsorption, the hydrogen purity of the cracked gas can reach 99.5%, which can be directly recycled to the first reactor.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. By catalytic reforming of waste cooking oil and esterification of branched polyols, an ester molecular structure without β-hydrogen and containing sterically hindered branches is constructed, eliminating oxidation-sensitive sites from a chemical perspective, thereby improving the oxidation stability of base oil by more than 6 times. This effectively avoids problems such as sudden drop in pH, sudden increase in viscosity and increased corrosivity caused by rancidity in traditional vegetable oil-based cutting fluids during use. 2. The intelligent sustained-release antioxidant microcapsule technology enables precise spatial and temporal release of antioxidants, overcoming the shortcomings of traditional additives that are rapidly consumed after a single addition and easily lost under high-temperature shear. 3. The microemulsion formed by the compound surfactant system has excellent hard water resistance and long-term storage stability. Even in environments with high calcium and magnesium ion concentrations, it can maintain an interfacial tension of less than 30 mN / m, ensuring effective separation and suspension of chips and abrasive particles, preventing deposits from accumulating in machine tool guideways and cooling pipes, and ensuring continuous cleanliness of the processing area. 4. The entire process route is based entirely on renewable waste resources, does not rely on fossil raw materials, has a high biodegradability rate (OECD 301B standard), and has an acute aquatic toxicity (for Daphnia macrocarpa) EC50 greater than 100 mg / L, meeting the requirements for green product certification and possessing significant environmental and economic benefits. 5. By reconstructing molecular structures, integrating smart materials, and coupling green processes, the system systematically solves the industry pain points of vegetable oil-based cutting fluids, such as poor long-term stability, insufficient cleanliness, and high environmental risks, providing a truly sustainable, high-performance, and environmentally friendly processing fluid solution for the high-end manufacturing sector. Detailed Implementation

[0018] This invention provides a method for producing an environmentally friendly, long-lasting, cleaning-grade cutting fluid. The core of this method lies in using waste cooking oil as the initial raw material and employing a multi-stage catalytic reforming process to directionally construct a branched polyol ester molecular structure with high oxidation stability, excellent lubrication performance, and strong resistance to microbial degradation. This is combined with a functionalized surfactant system and intelligent slow-release antioxidant microcapsule technology to form a water-based cutting fluid formulation that is environmentally friendly, has long-lasting stability, and excellent cleaning capabilities. This method addresses the core defects of vegetable oil-based cutting fluids, such as easy oxidation and rancidity, emulsification instability, and microbial growth, from the molecular structure design perspective, while simultaneously achieving high-value recycling of waste oil resources.

[0019] The technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples, so as to ensure that those skilled in the art can fully understand and implement the present invention.

[0020] Example 1: Pretreatment of waste cooking oil (molecular distillation); deoxygenation-cracking-isomerization reaction (320℃ / 3.0MPa); carbonylation reaction (180℃ / 2.0MPa); neopentyl polyol is trimethylolpropane; bio-ester base oil + compound surfactant (3:1) + 1.0% intelligent sustained-release microcapsules + 0.3% rust inhibitor + 0.1% defoamer; homogenization emulsification at 60℃; Production process: Waste edible oil pretreatment → catalytic cracking-isomerization → carbonylation → directed esterification → compound emulsification → finished product.

[0021] Example 2: The polyol was pentaerythritol, the esterification temperature was 210°C, the catalyst was tetrabutyl titanate (0.5%), and the rest of the formulation and process were the same as in Example 1; Production process: Same as Example 1 (esterification parameters adjusted).

[0022] Example 3: Pretreatment only involves adsorption and filtration without molecular distillation; the remaining formulation and process are the same as in Example 1. Production process: Same as in Example 1 (molecular distillation step omitted).

[0023] Example 4: 0.5% intelligent sustained-release microcapsules, with the remaining formulation and process the same as in Example 1; Production process: Same as Example 1 (with adjustment of microcapsule addition amount).

[0024] Example 5: 1.5% intelligent sustained-release microcapsules, with the remaining formulation and process the same as in Example 1; Production process: Same as Example 1 (with adjustment of microcapsule addition amount).

[0025] Example 6: Deoxidation-pyrolysis-isomerization temperature 300℃, other formulations and processes are the same as in Example 1; Production process: Same as in Example 1 (catalytic temperature adjustment).

[0026] Example 7: Deoxidation-cracking-isomerization temperature 340℃, other formulations and processes are the same as in Example 1; Production process: Same as in Example 1 (catalytic temperature adjustment).

[0027] Example 8: The ratio of compound surfactants is 2:1, and the rest of the formulation and process are the same as in Example 1; Production process: Same as Example 1 (surfactant ratio adjusted).

[0028] Comparative Example 1: The base oil was mineral oil; no catalytic reforming or smart microcapsules were used; the rest of the formulation and process were the same as in Example 1; Production process: Mineral oil + surfactant + additives → emulsification → finished product.

[0029] Comparative Example 2: Direct transesterification of waste edible oil without catalytic cracking-isomerization; no smart microcapsules; the rest of the formulation and process are the same as in Example 1; Production process: Waste edible oil transesterification → emulsification → finished product.

[0030] Test method: Long-term stability test: pH change is monitored during continuous use; oxidation induction period is determined by PDSC method; stratification is observed after standing in hard water (calcium and magnesium ions 500 mg / L); tool life and workpiece roughness are tested.

[0031] Environmental testing: Biodegradation rate was determined according to OECD 301B standards; aquatic toxicity EC50 value was tested.

[0032] Basic performance tests: kinematic viscosity at 40°C was measured; PB value was tested using a four-ball machine; and cleanliness and emulsion stability were evaluated.

[0033] The test data comparisons are shown in Table 1 and Table 2.

[0034] Table 1. Comparison of Biodegradation Rate, Continuous Use Days, Oxidation Induction Period, and Kinematic Viscosity at 40℃ Test Project Biodegradation rate (%) Number of consecutive days of use (days) Oxidation induction period (min) <![CDATA[40℃ kinematic viscosity (mm 2 / s)]]> Example 1 88 180 65 30 Example 2 86 180 70 45 Example 3 85 160 58 28 Example 4 87 150 55 29 Example 5 89 190 72 31 Example 6 86 165 60 27 Example 7 87 175 68 32 Example 8 88 170 63 29 Comparative Example 1 35 60 15 25 Comparative Example 2 75 90 22 35 Table 2 Comparison of Hard Water Stabilization Days, Tool Life Extension, and Workpiece Surface Roughness Ra Test Project Number of days with stable hard water (days) Tool life extended (%) Workpiece roughness Ra (μm) Example 1 30 35 0.7 Example 2 32 40 0.6 Example 3 25 30 0.8 Example 4 28 32 0.8 Example 5 32 38 0.7 Example 6 29 33 0.8 Example 7 31 36 0.7 Example 8 27 34 0.8 Comparative Example 1 10 0 1.2 Comparative Example 2 15 10 1 Examples 1-8 show a biodegradation rate of ≥85% and continuous use for ≥150 days, which is far superior to the comparative examples. Comparative example 1 shows that traditional mineral oil has poor environmental performance, and comparative example 2 shows that the lack of catalytic reforming leads to insufficient long-term effectiveness. This confirms that catalytic reforming + intelligent microcapsules are the key to long-term environmental protection.

[0035] Replacing polyols with pentaerythritol (Example 2) improves lubrication strength; increasing the amount of smart microcapsules (Examples 4→1→5) simultaneously optimizes oxidation stability and long-lasting effect; the catalytic temperature range of 300-340℃ ensures the formation of branched structures.

[0036] The embodiment uses waste cooking oil as raw material, which is a resource recycling process; it can be used continuously for 180 days without replacement, reducing production costs; it meets environmental protection standards and is compatible with green manufacturing; it has excellent cleanliness and ensures processing precision.

[0037] Compared to traditional mineral oil (Comparative Example 1), the biodegradability rate of the example was increased by 151%, and the continuous use time was increased by 200%. Compared to the uncatalyzed system (Comparative Example 2), the oxidation induction period was increased by 195%, and the tool life was extended by 240%, solving the industry problems of poor environmental performance and insufficient long-term effectiveness of traditional cutting fluids.

[0038] In summary, the method described in this invention, through the synergy of catalytic reforming and intelligent functions, can achieve the preparation of long-lasting, clean, and environmentally friendly cutting fluids with different parameter combinations, making it suitable for high-end precision manufacturing scenarios.

[0039] The above are merely preferred embodiments of the present invention and are 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 method for producing an environmentally friendly, long-lasting, cleaning production line cutting fluid, characterized in that, Includes the following steps: Waste cooking oil is pretreated to remove moisture, free fatty acids, solid impurities, and metal ions; Under the action of a supported bifunctional catalyst, triglycerides are converted into a mixture of C8-C18 medium-short chain fatty acids with branched structures in a fixed-bed continuous reactor via a deoxygenation-cracking-isomerization coupled reaction. The obtained pyrolysis products were carbonylated in the presence of a palladium-tin bimetallic catalyst in a carbon monoxide atmosphere to obtain branched fatty acids with a degree of branching of 8-12 and an iodine value of less than 5 g I2 / 100 g. The branched fatty acid was subjected to a directed esterification reaction with neopentyl polyol under nitrogen protection; The bio-ester base oil, compound surfactant, intelligent slow-release antioxidant microcapsules, rust inhibitor, defoamer, and deionized water are mixed and homogenized to emulsify, thereby obtaining a microemulsion with a solid content of 8%.

2. The production method of the environmentally friendly, long-lasting, cleaning production line cutting fluid according to claim 1, characterized in that, The compound surfactant is composed of polyoxyethylene (10) lauryl ether and sodium dodecylbenzene sulfonate in a mass ratio of 3:

1.

3. The production method of the environmentally friendly, long-lasting, cleaning production line cutting fluid according to claim 1, characterized in that, The intelligent sustained-release antioxidant microcapsules use Irganox 1076 and dilauryl thiodipropionate as core materials and PLGA as wall material.

4. The production method of the environmentally friendly, long-lasting, cleaning production line cutting fluid according to claim 1, characterized in that, The pretreatment steps include: heating the waste cooking oil to 60°C, adding a mixed adsorbent of 0.5% activated carbon and 1.0% diatomaceous earth while stirring at 300 rpm, stirring at a constant temperature for 30 minutes, and then filtering; the filtrate is treated by molecular distillation under the following operating conditions: absolute pressure 5 Pa, evaporation surface temperature 180°C, and condensation surface temperature 40°C, so that the moisture content is less than 0.05% and the acid value is less than 1.0 mg KOH / g.

5. The production method of the environmentally friendly, long-lasting, cleaning production line cutting fluid according to claim 1, characterized in that, The neopentyl polyol is 2-methyl-2-propyl-1,3-propanediol or trimethylolpropane, and its molecular structure does not contain β-hydrogen atoms. The resulting bio-ester base oil has a pour point below -25°C and a kinematic viscosity of 25-35 mmHg at 40°C. 2 / s, oxidation induction period exceeds 60min.

6. The production method of the environmentally friendly, long-lasting, cleaning production line cutting fluid according to claim 1, characterized in that, The intelligent slow-release antioxidant microcapsules trigger a pulsed release of antioxidants when the pH value of the cutting fluid system drops below 6.5, achieving on-demand response protection.

7. The production method of the environmentally friendly, long-lasting, cleaning production line cutting fluid according to claim 1, characterized in that, The microemulsion formed by the compound surfactant has an average particle size of 80-120 nm, an absolute value of Zeta potential greater than 40 mV, and shows no demulsification or stratification when left to stand for 30 days in hard water with a total calcium and magnesium ion concentration of 500 mg / L.

8. The production method of the environmentally friendly, long-lasting, cleaning production line cutting fluid according to claim 1, characterized in that, The rust inhibitor is 1-hydroxybenzotriazole, added at 0.3% of the total mass of the cutting fluid; the defoamer is polyether-modified silicone oil with a kinematic viscosity of 1000 mmHg at 25°C. 2 / s, with an addition amount of 0.1%.

9. The production method of the environmentally friendly, long-lasting, cleaning production line cutting fluid according to claim 1, characterized in that, The catalyst uses mesoporous ZSM-5 molecular sieve as a support, and the active components are nickel and molybdenum in a mass ratio of 3:1, with a total loading of 8.0%.

10. The production method of the environmentally friendly, long-lasting, cleaning production line cutting fluid according to claim 1, characterized in that, The catalyst is p-toluenesulfonic acid at 0.8% by mass of fatty acids.