A milling tool fluid for copper strip face milling and a method of using the same

Abstract

The application discloses a milling cutter liquid for copper strip face milling and a use method thereof, and each component of the milling cutter liquid comprises, in percentage by weight, polyether cooling lubricant 22-38%, composite surfactant 5-15%, medium processing agent 2-10%, and deionized water in balance; wherein the composite surfactant is composed of lauryl alcohol polyether-4 (LA-4), cocamide propyl betaine (6501) and nonyl phenol polyoxyethylene ether (NP-10). The milling cutter liquid can reduce wear, protect the cutter, reduce copper powder agglomeration, sedimentation or re-adhesion on the copper strip or cutter surface, reduce black spots on the copper strip surface, and inhibit oil fume.

Description

Technical Field

[0001] This invention belongs to the field of organic solvent chemistry, specifically relating to a milling fluid for milling copper strips and its application method. Background Technology

[0002] With advancements in production technology and rising product quality requirements, the entire industrial system is moving towards green, efficient, and precise manufacturing. Processing companies are constantly pursuing the ultimate in machining performance, pushing the development of milling fluids to the forefront. This is most evident in copper machining. In copper milling, milling fluid is the core process medium, undertaking crucial functions such as cooling, lubrication, cleaning, corrosion resistance, and extending tool life. The quality of its component ratio directly affects the surface quality of the copper material, machining accuracy, tool wear, and overall production efficiency.

[0003] Existing production lines generally use two types of milling fluid components: 1. All-oil system – mainly mineral oil or synthetic ester, which has good lubrication but insufficient cooling, making copper shavings separation difficult, and causing severe smoke generation during the drying process; 2. Emulsion system – mainly mineral oil + emulsifier + water, which is inexpensive but lacks antioxidant components, making the copper strip surface prone to black spots and yellow stains. The emulsion system is prone to demulsification under high-speed shearing at 700-900 rpm, producing grease particles that stick to the cutter and form secondary scratches. In addition, the recovered copper shavings need to be centrifuged and dehydrated, and then dried with hot air at around 600 ℃. Milling copper shavings lubricated with traditional oils produce severe smoke at high temperatures, which can easily lead to environmental complaints.

[0004] Patent application CN106635267A discloses a microemulsion rolled from copper strip and its preparation method. The composition involves dissolving a surfactant (a compound of oleic acid, triethanolamine, sorbitan laurate, nonylphenol polyoxyethylene ether, polyethylene glycol 200, and sodium petroleum sulfonate) in a hydrogenated base oil, and then adding a specific co-surfactant, 1,2,3-benzotriazole corrosion inhibitor, and sodium sulfate electrolyte solution to form the rolled microemulsion. This microemulsion, used to replace traditional emulsified oil, offers advantages such as readily available and inexpensive raw materials, long-term stability without separation, and excellent lubricity, corrosion resistance, and storage stability when diluted with water. However, the microemulsion disclosed in this patent application cannot quickly separate and carry away copper powder, posing a risk of secondary scratches, and the surface quality of the rolled copper alloy needs improvement.

[0005] Patent application CN109694770A discloses a copper alloy cutting fluid composition comprising the following components by weight: white oil: 45-60 parts; sulfonated castor oil: 10-25 parts; sodium petroleum sulfonate: 10-20 parts; Mannich base: 1-3 parts; liquid rosin: 1-7 parts; special amine: 1-5 parts; nonylphenol polyoxyethylene ether: 0.5-5 parts; branched fatty alcohol: 1-6 parts; Span-80: 0.2-1.4 parts; defoamer: 0.1-0.7 parts. This invention has the following beneficial effects: By adding Mannich base as a corrosion inhibitor, the corrosion is inhibited by the adsorption of the benzotriazole ring in the molecule onto the copper surface. Simultaneously, the nitrogen atom on the amine group provides lone pair electrons for adsorption onto the copper surface, further enhancing the binding force between the corrosion inhibitor molecule and the metal. Furthermore, the alkyl portion on the amine group effectively prevents the attack of corrosive ions in the medium. However, the cutting fluid disclosed in the patent application has insufficient antioxidant properties, and spots are prone to appear on the copper strip after milling. Summary of the Invention

[0006] This invention provides a milling fluid for milling copper strips. This milling fluid can reduce wear, protect the cutting tool, reduce copper powder agglomeration, sedimentation or re-adhesion on the surface of the copper strip or the cutting tool, reduce black spots on the surface of the copper strip, and suppress oil fumes.

[0007] This invention provides a milling fluid for milling copper strip surfaces. The components of the milling fluid, by weight percentage, include: Polyether-based cooling lubricant 22%-38%; 5%-15% of compound surfactants; Media treatment agent 2%-10%; Deionized water balance; The composite surfactant is composed of lauryl alcohol polyether-4 (LA-4), cocamidopropyl betaine (6501), and nonylphenol polyoxyethylene ether (NP-10). The medium treatment agent includes sodium bicarbonate.

[0008] The composite surfactant consists only of lauryl alcohol polyether-4, cocamidopropyl betaine, and nonylphenol polyoxyethylene ether (NP-10), and no other components can be added. The three components work synergistically to achieve a suitable dynamic surface tension, which is the core of rapid copper powder peeling, dispersion, and prevention of black spots. Adding other surfactants will disrupt the balance and increase the risk of oil spots and demulsification.

[0009] Preferably, by weight percentage, the composite surfactant comprises: The content of lauryl alcohol polyether-4 is 5% to 10%; The content of cocamidopropyl betaine is 1%–5%; The content of nonylphenol polyoxyethylene ether is 1% to 5%, and the nonylphenol polyoxyethylene ether is NP-10.

[0010] The nonylphenol polyoxyethylene ether provided by this invention comprises 10 ethylene oxide (EO) molecules, resulting in a higher hydrophilic-lipophilic balance (HLB) value. This makes the hydrophilicity and lipophilicity of the milling fluid more balanced. At the same time, controlling the content of NP-10 can better disperse copper powder and synergistically reduce surface tension. With the help of the higher HLB, the stripped copper powder is stably dispersed in the milling fluid, preventing copper powder agglomeration and sedimentation, while also assisting in the spread of the liquid film. Due to the synergistic effect of appropriate amounts of 6501 and LA-4, only a low content of NP-10 is needed to achieve the above-mentioned surface-active functions. At the same time, the low content of NP-10 keeps the oil content of the system at a reasonable level, reducing problems such as oil spots on the copper strip surface and drying smoke.

[0011] The advanced compound of 6501, LA-4, and NP-10 in this invention achieves precise control of surface tension at 28-32 mN / m through dynamic surface tension, which is far lower than that of traditional milling fluids, resulting in only 0-1 black spots per m on the copper strip surface. 2 It is far superior to commercially available emulsions (3 units / m³). 2 ).

[0012] Preferably, the sodium bicarbonate content is 1%-3% by weight. This invention controls the sodium bicarbonate content to ensure sufficient CO2 production during the high-temperature drying of copper strips, effectively suppressing oil fumes. Simultaneously, it avoids increasing the alkalinity of the system and prevents excessive sodium bicarbonate from existing as particulate matter, which could clog nozzles, increase system impurities, and negatively impact the surface quality of the copper strip.

[0013] Preferably, the polyether-type cooling lubricant includes polyether synthetic oil (PAG) and fatty acid methyl ester ethoxylate.

[0014] This invention utilizes the polar ether groups of polyether synthetic oil to rapidly adhere to the metal surface through physical adsorption, forming a basic lubricating film. The molecular weight and viscosity of this film are well-suited for milling processes, resulting in a tough film capable of resisting high-speed shear damage. Furthermore, by utilizing the appropriate amount of ester groups from fatty acid methyl ester ethoxylates, a slight chemical adsorption occurs on the metal surface under high pressure and temperature, forming a chemical adsorption film. This film is superimposed on the physical adsorption film of PAG, forming a double-layer extreme pressure film. The film's friction coefficient is as low as μ < 0.08, significantly reducing frictional wear between the tool and the copper strip. The formation of this double-layer extreme pressure film reduces frictional heat generation at its source, achieving an instantaneous temperature reduction of over 60°C, while simultaneously protecting the tool and reducing wear.

[0015] More preferably, the viscosity of the polyether synthetic oil is 46-68 cSt, the carbon chain length of the fatty acid methyl ester ethoxylate is C12-C18, and each fatty acid methyl ester molecule is attached with 8-12 ethylene oxide units. This invention controls the viscosity of the polyether synthetic oil to enable better adhesion to metal surfaces, and controls the degree of ethoxylation (EO) to give the fatty acid methyl ester ethoxylate good water solubility, achieving good chemisorption using an appropriate amount of ester groups.

[0016] More preferably, by weight percentage, the content of polyether synthetic oil is 10%-20%, and the content of fatty acid methyl ester ethoxylate is 5-10%. This invention, by controlling the content of polyether synthetic oil, enables the formation of a continuous physical adsorption film on the metal surface, minimizing the risk of film damage from high-speed shearing. It also achieves a more suitable oil composition, reducing oil stains on copper strips and lowering the likelihood of drying smoke. Furthermore, by controlling the content of fatty acid methyl ester ethoxylate, this invention makes the chemical adsorption film more compact, thereby achieving better extreme pressure performance, while minimizing repulsion with PAG, which could damage the film structure and affect lubrication.

[0017] More preferably, the polyether-type coolant further includes triethanolamine, with the content of triethanolamine being 5%-10% by weight. This invention utilizes triethanolamine as an organic amine with strong buffering capacity. By controlling the content of triethanolamine (TEA), the pH of the milling fluid can be precisely controlled at 8.5-9.5, mitigating the slight acidity changes that occur in the system due to long-term use.

[0018] Preferably, the media treatment agent further includes polydimethylsiloxane, benzotriazole and methylbenzotriazole (TTA), wherein the content of polydimethylsiloxane is 2%-5% by weight, the content of benzotriazole is 0.1%-0.3% and the content of methylbenzotriazole is 0%-0.1%.

[0019] This invention provides an appropriate amount of benzotriazole (BAT) to form a Cu-BTA complex protective film with copper atoms to prevent oxidation and blackening. This invention also provides an appropriate amount of polydimethylsiloxane (PDMS, 1000cSt) to reduce the surface energy of bubbles and eliminate sticky oil droplets.

[0020] Preferably, it further includes: Sodium benzoate 0.2%–1%; Isothiazolinone 0.05%–0.2%; Polyether-modified silicone oil defoamer 0.1%–0.5%; Disodium ethylenediaminetetraacetate (EDTA-2Na) 0.1%~0.3%.

[0021] This invention provides an appropriate amount of sodium benzoate to achieve long-lasting rust prevention, an appropriate amount of isothiazolinone to inhibit bacterial growth and extend the life of the liquid tank, and an appropriate amount of EDTA-2Na to chelate Ca2+ / Mg2+ in the water to prevent soap scum from clogging the nozzles.

[0022] On the other hand, the present invention also provides a method for using the milling fluid for milling copper strips, including: The milling fluid for milling the copper strip is added to the aqueous phase and stirred to emulsify to obtain a microemulsion. The stirring speed is 300–8000 rpm and the stirring time is 15–30 min. The volume ratio of the milling fluid for milling the copper strip to the aqueous phase is 1:95–1:98. Microemulsions are added to a milling machine for continuous processing of copper strips.

[0023] The present invention also provides a method for daily maintenance of microemulsions, including: using a refractometer to detect the concentration of microemulsions before and during each shift of production, and controlling the refractive index to be 4% to 6%.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention utilizes a polyether-based cooling lubricant to form a low-friction extreme pressure film at the interface between the cutting tool and the copper strip, thereby reducing instantaneous temperature and tool wear. It leverages the low dynamic surface tension of LA-4, allowing the milling fluid to instantly spread and form a continuous liquid film on both the cutting tool and the copper strip during high-speed shearing milling, breaking the adhesion between copper powder and the metal surface. Furthermore, it utilizes the amphoteric surfactant 6501, exhibiting strong wetting properties to enhance the adhesion between the liquid film and the metal surface, improving the copper powder removal effect of LA-4 and simultaneously increasing the system's hard water resistance, making it suitable for industrial tap water dilution processes. Finally, it utilizes NP-10, leveraging its strong dispersing properties to rapidly encapsulate the copper powder removed by LA-4 and 6501, forming a stable dispersion system that prevents copper powder agglomeration, sedimentation, or re-adhesion to the copper strip / cutting tool surface, achieving a "rapid powder removal" effect. The synergistic effect of LA-4, 6501, and NP-10 provided by this invention achieves rapid copper powder removal and dispersion with low residue, significantly reducing black spots on the copper strip surface.

[0025] This invention utilizes the decomposition of sodium bicarbonate under high-temperature conditions during copper powder drying to generate CO2 gas. This CO2 gas can dilute the contact concentration of oil on the surface of the copper powder with air, disrupt the combustion / decomposition conditions of the oil, and suppress the generation of oil fumes from the source. Attached Figure Description

[0026] Figure 1 This is a physical image of the cutting tool provided in Embodiment 2 of the present invention.

[0027] Figure 2This is a physical image of the copper strip provided in Embodiment 3 of the present invention.

[0028] Figure 3 This is a physical image of the copper strip provided in Comparative Example 1 of the present invention. Detailed Implementation

[0029] The present invention and its beneficial effects are further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0030] Example 1 The milling fluid for milling copper strips provided in this embodiment comprises the following components by weight percentage. These components are all commercially available industrial-grade raw materials, and are listed by weight percentage as follows: Polyether synthetic oil (PAG 46 cSt) 15% Fatty acid methyl ester ethoxylate 8% Triethanolamine (TEA) 7% Laureth-4 (LA-4) 6% Cocamidopropyl betaine (6501) 3% Nonylphenol polyoxyethylene ether (NP-10) 2% Polydimethylsiloxane (PDMS, 1000 cSt) 3% Benzotriazole (BTA) 0.2% Sodium bicarbonate 2% Sodium benzoate 0.5% Isothiazolinone 0.1% Polyether-modified silicone oil defoamer 0.2% Disodium ethylenediaminetetraacetate (EDTA-2Na) 0.1% Deionized water balance.

[0031] Method for preparing the milling fluid for milling the surface of this copper strip: 1. Add polyether synthetic oil, fatty acid methyl ester ethoxylate, and triethanolamine in the above proportions in sequence, and stir until homogeneous.

[0032] 2. Add the composite surfactant, media treatment agent, and auxiliary functional agent in sequence, and continue stirring until completely dissolved and transparent.

[0033] 3. Finally, add deionized water to make up the volume and stir well to obtain the milling cutter fluid.

[0034] How to use: The milling fluid and tap water were mixed at a volume ratio of 1:95 and stirred at 2000 rpm for 30 minutes to obtain a microemulsion.

[0035] No secondary dilution is required; the microemulsion can be directly applied to a milling machine to continuously process C19210 copper strip for 8 hours.

[0036] Before and during each shift, the concentration of the microemulsion is measured using a refractometer, and the refractive index is controlled at 4% to 6%.

[0037] Results: Copper strip surface: 1 black spot observed with the naked eye; Copper dust dried at 600 ℃ for 30 min showed no smoke; Tool wear: slight wear, i.e., measured using the national standard method.

[0038] The degree of tool wear was determined according to GB / T 16458-2021 "Test Method for Wear of Cutting Tools". The wear width VB on the flank face of the tool was measured using a tool microscope, and the quantitative judgment was as follows: Slight wear: Wear width VB on the back face ≤ 0.10 mm.

[0039] Example 2 PAG was increased to 18%, fatty acid methyl ester ethoxylate was reduced to 6%, and the rest were the same as in Example 1. Results: One black spot was observed on the copper strip surface; no smoke was observed; tool wear was not obvious, i.e., tool wear was not obvious (VB ≤ 0.05 mm). Figure 1 As shown.

[0040] Example 3 The PDMS content was increased to 5%, sodium bicarbonate was reduced to 1%, and the rest remained the same as in Example 1. No black spots were observed on the copper strip surface with the naked eye. Figure 2 As shown; no smoke was observed. Tool wear condition: slight wear, i.e., slight wear: back face wear width VB ≤ 0.10mm.

[0041] Example 4 The BTA concentration was increased to 0.3%, and an additional 0.1% methylbenzotriazole (TTA) was added, specifically for copper strip. The rest of the process was the same as in Example 1. No black spots were observed on the copper strip surface; no smoke was detected. Tool wear was slight: the wear width VB on the flank face ≤ 0.10 mm. Example 5 The difference compared to Example 1 is that the surfactant content was adjusted: Lauryl alcohol polyether-4 (LA-4): 8% Cocamidopropyl betaine (6501): 4% Nonylphenol polyoxyethylene ether (NP-10): 3% The remaining components and processes are the same as in Example 1.

[0042] Results: Black spots: 0 per square meter; Drying smoke: None; Tool wear: Slight wear, back face wear width VB ≤ 0.10 mm.

[0043] Example 6 Compared to Example 2, the difference was that the fatty acid methyl ester ethoxylate content was set at 12%, while the rest remained the same as in Example 2. Results: Black spots: 1 / m²; Drying smoke: Slight; Tool wear: Moderate wear (VB≈0.15mm). Note: Compared to Example 2, the higher content of fatty acid methyl ester ethoxylate repels PAG, resulting in decreased lubrication and higher oil content, but the effect is still acceptable.

[0044] Example 7 Compared with Example 3, NP-10 was set to 6% (>5%), and the rest was the same as in Example 3.

[0045] Results: Black spots: 1 / m²; Drying smoke: slight; Tool wear: slight to moderate wear (VB≈0.12 mm). Note: Compared with Example 3, the high NP-10 content affected the powder carrying speed, increased oil content, and affected the extreme pressure film, but the effect was still acceptable.

[0046] Comparative Example 1 Commercially available mineral oil emulsion (containing 60% mineral oil, 5% fatty acid soap, and 2% emulsifier) ​​was diluted with water at a ratio of 1:95 and tested on the same machine.

[0047] Result: 3 black spots per m on the copper strip surface 2 ,like Figure 3 As shown; white smoke is visible at the drying site; tool wear: obvious wear (VB > 0.20 mm). Due to the lack of the polyether-type cooling lubricant provided in this embodiment to form a physical and chemical protective film, the tool wear is severe. Due to the lack of sodium bicarbonate to suppress smoke, white smoke is visible at the drying site. The copper powder in Comparative Example 1 is carried away more slowly, and there are more black spots on the surface.

[0048] Comparative Example 2 Unlike Example 1, sodium bicarbonate, benzotriazole, and polydimethylsiloxane were not added; otherwise, the results were the same as in Example 1. The copper strip surface showed 2 black spots per m. 2 Severe white smoke was observed during drying; tool wear: significant wear (VB > 0.20 mm). Slight white smoke was present during drying due to the absence of sodium bicarbonate.

[0049] Comparative Example 3 Unlike Example 1, lauryl ether-4 (LA-4) was replaced with lauryl alcohol (C12H26O, EO-free), while the other components and processes were the same as in Example 1.

[0050] Results: 3 black spots per square meter on the copper strip surface; no smoke during drying; tool wear: obvious wear (VB > 0.20 mm).

[0051] Note: Lauryl alcohol lacks an EO structure, has high dynamic surface tension, poor spreadability, and cannot quickly peel off and remove copper powder, resulting in a significant increase in surface defects on the copper strip.

[0052] Comparative Example 4 Unlike Example 1, no fatty acid methyl ester ethoxylate was added; the other components and processes were the same as in Example 1.

[0053] Results: 2 black spots per square meter on the copper strip surface; no smoke during drying; tool wear: significant wear (VB > 0.20 mm).

[0054] Note: Without fatty acid methyl ester ethoxylate, it cannot synergistically form a double-layer extreme pressure film with PAG. PAG alone is insufficient for lubrication, resulting in increased interfacial friction and significantly aggravated tool wear.

[0055] Comparison table of the effects of the milling fluids provided in Examples 1-7 and Comparative Examples 1-4 1. Black spot detection Method: Visual counting using a standard light source on a 1㎡ copper strip. Standard: GB / T4677-2002 Inspection of surface quality of copper and copper alloy plates, strips and foils.

[0056] 2. Drying smoke detection Method: Dry copper powder with hot air at 600℃ for 30 minutes, and observe visually. Grading: None / Mild / Significant / Severe.

[0057] 3. Tool wear detection Method: The wear width VB on the flank face was measured using a tool microscope. Standard: GB / T 16458-2021 Test method for wear of cutting tools.

[0058] Tool wear Non-obvious wear: VB≤0.05mm Minor wear: VB≤0.10mm Slightly uneven wear: VB≈0.12mm Moderate wear: VB≈0.15mm Significant wear: VB > 0.20 mm.

Claims

1. A milling fluid for milling copper strip surfaces, characterized in that, The components of the milling fluid, by weight percentage, include: Polyether-based cooling lubricant 22%-38%; 5%-15% of compound surfactants; Media treatment agent 2%-10%; Deionized water balance; The composite surfactant is composed of lauryl alcohol polyether-4, cocamidopropyl betaine and nonylphenol polyoxyethylene ether; The medium treatment agent includes sodium bicarbonate.

2. The milling fluid for milling copper strips according to claim 1, characterized in that, By weight percentage, the composite surfactant comprises: The content of lauryl alcohol polyether-4 is 5% to 10%; The content of cocamidopropyl betaine is 1%–5%; The content of nonylphenol polyoxyethylene ether is 1% to 5%, and the nonylphenol polyoxyethylene ether is NP-10.

3. The milling fluid for milling copper strips according to claim 1, characterized in that, The sodium bicarbonate content is 1%-3%.

4. The milling fluid for milling copper strips according to claim 1, characterized in that, The polyether-type cooling lubricant includes polyether synthetic oil and fatty acid methyl ester ethoxylate.

5. The milling fluid for milling copper strips according to claim 4, characterized in that, The viscosity of the polyether synthetic oil is 46-68 cSt, the carbon chain length of the fatty acid methyl ester ethoxylate is C12-C18, and each fatty acid methyl ester molecule is attached with 8-12 ethylene oxide units.

6. The milling fluid for milling copper strips according to claim 4, characterized in that, By weight percentage, the content of polyether synthetic oil is 10%-20%, and the content of fatty acid methyl ester ethoxylate is 5%-10%.

7. The milling fluid for milling copper strips according to claim 4, characterized in that, The polyether-type coolant and lubricant also includes triethanolamine, with the triethanolamine content being 5%-10% by weight.

8. The milling fluid for milling copper strips according to claim 1, characterized in that, The media treatment agent further includes polydimethylsiloxane, benzotriazole and methylbenzotriazole, wherein the content of polydimethylsiloxane is 2%-5% by weight, the content of benzotriazole is 0.1%-0.3% and the content of methylbenzotriazole is 0%-0.1%.

9. The milling fluid for milling copper strips according to claim 1, characterized in that, Also includes: Sodium benzoate 0.2%–1%; Isothiazolinone 0.05%–0.2%; Polyether-modified silicone oil defoamer 0.1%–0.5%; Disodium ethylenediaminetetraacetate 0.1%–0.3%.

10. A method of using the milling fluid for milling copper strip according to any one of claims 1-9, characterized in that, include: The milling fluid for milling the copper strip is added to the aqueous phase and stirred to emulsify to obtain a microemulsion. The stirring speed is 300–8000 rpm and the stirring time is 15–30 min. The volume ratio of the milling fluid for milling the copper strip to the aqueous phase is 1:95–1:

98. Microemulsions are added to a milling machine for continuous processing of copper strips.

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