KR102548443B1 - Aqueous colloidal suspension and cutting fluid comprising the same - Google Patents

Abstract

Disclosed is an aqueous suspension containing water, hexagonal boron nitride (hBN) particles, and a dispersant, and a cutting oil diluted with water.

Description

Aqueous colloidal suspension and cutting fluid comprising the same {Aqueous colloidal suspension and cutting fluid comprising the same}

The present invention relates to an aqueous suspension and a cutting oil containing the same, and more particularly, to a cutting oil containing water, hexagonal boron nitride (hBN) particles, and a dispersant, wherein the hexagonal boron nitride (hBN) particles are uniformly dispersed for a certain period of time. By maintaining a colloidal state, it exhibits superior cutting performance (processing precision of workpieces, wear of tools) compared to existing water-soluble cutting oils of O/W emulsion type, and provides cooling and lubrication functions necessary for machining in various fields. Hexagonal boron nitride particle-based It relates to an aqueous suspension and a cutting oil used by further diluting it with water.

Cutting fluid is used for the purpose of increasing the precision of surface machining of a workpiece and extending tool life by giving cooling and lubricating functions by acting on the machined surface between the tool and the workpiece during the machining process.

These cutting oils are largely divided into oil-based non-water-soluble cutting oils and water-soluble cutting oils diluted in water. Among them, non-aqueous cutting oil has excellent lubrication performance and is used for precise machining, but it is difficult to apply to hard metals (Ti, Ni, SUS, etc.) due to its low boiling point, high fire risk and poor cooling performance. On the other hand, water-soluble cutting oil has excellent cooling performance, but has poor lubrication performance compared to non-aqueous cutting oil, making it difficult to apply it to precision machining of non-ferrous metals.

In addition, conventional oil-based non-aqueous cutting oil as well as water-soluble cutting oil are mainly prepared using petroleum-based and ester-based vegetable oils and diluted with water, and there is a problem of rotting due to microbial growth in the process of recycling cutting oil. In the case of water-soluble cutting oil, it is difficult to treat wastewater due to the oil contained in water-soluble cutting oil. There are disadvantages, such as the generation of carbon dioxide.

On the other hand, Patent Document 1 discloses a technique of using vegetable oil as a base oil while emphasizing eco-friendliness in consideration of the impact on the environment, but this problem remains as an oil-based water-soluble cutting oil. In addition, Patent Documents 2 and 3 disclose eco-friendly water-soluble cutting oil technology using alkaline electrolytic ionized water without using oil, but the grounds for harmfulness are specified, but metal workability is significantly lower than that of conventional O/W emulsion-type water-soluble cutting oil There seems to be a limit to the application of water-soluble cutting oil.

Therefore, it satisfies the lubricating performance of non-water-soluble cutting oil and the cooling performance of water-soluble cutting oil at the same time, carbon-neutral without oil, clean processing that minimizes the amount of cutting oil, and resource circulation method that does not or dramatically reduces waste water and waste oil. Cutting fluid is required.

Korean Patent Registration No. 10-0665790 Korean Registered Patent No. 10-2053046 Korean Patent Registration No. 10-2146032

Accordingly, the present invention has been devised to solve the above problems, and includes water, hexagonal boron nitride (hBN) particles, and a dispersing agent, wherein the hexagonal boron nitride (hBN) particles are uniformly dispersed and maintains a colloidal state for a certain period of time. Its object is to provide an aqueous suspension and a cutting oil containing the same that exhibit superior cutting performance (processing precision of a workpiece, wear of a tool) compared to conventional water-soluble cutting oil of an O/W emulsion type.

In addition, the present invention further dilutes the aqueous suspension with water and uses it as a cutting oil for metal processing, etc., but further adds one or more of alkaline electrolytic water, metal rust inhibitor, antifreezing agent, antifoaming agent, and preservative to improve the processing precision of the workpiece metal workpiece, tool It provides cutting oil based on hexagonal boron nitride particles that not only extends life, but also has anti-rust, anti-freezing, anti-foaming and sterilizing effects. It does not contain oil and is eco-friendly, especially suitable for ultra-trace lubrication processing. The purpose.

The problem to be solved by the present invention is not limited to the technical problem mentioned above, and other technical problems not mentioned can be clearly understood by those skilled in the art from the description below. will be.

An aqueous suspension according to an embodiment of the present invention for achieving the above object includes water, hexagonal boron nitride (hBN) particles, and a dispersant.

In the above embodiment, the hexagonal boron nitride (hBN) particles are preferably hydrophilic particles having wettability in water.

In the above embodiment, the hexagonal boron nitride (hBN) particles are preferably particles synthesized at a temperature of 1600° C. or less in an air heat treatment furnace in which a gas atmosphere is not controlled.

In addition, in the above embodiment, the hexagonal boron nitride (hBN) particles are preferably primary and secondary particles having a particle size of 30 to 250 nm based on D50 and 1 μm or less based on D90 through application of ultrasonic waves for 24 hours. do. On the other hand, when looking at the above particle size from the aspect ratio (3 to 10), it is preferable that the specific surface area has a range of 10 to 90 m 2 /g.

In addition, in the above embodiment, it is preferable to mix the hexagonal boron nitride (hBN) particles in a weight ratio of 10 or less to the water, and the dispersant to the water in a weight ratio of 10 or less (solid weight of the dispersant). .

Further, in the above embodiment, the water preferably includes alkaline ionized water having a pH of 10 or higher.

In addition, in the above embodiment, the dispersant is preferably used alone or in combination with one or more selected from the group consisting of anionic, cationic, zwitterionic, and nonionic dispersants.

In addition, in the above embodiment, it is preferable to further include at least one selected from the group consisting of a rust inhibitor, an antifoaming agent, an antifreezing agent, and a preservative.

In addition, in the above embodiment, it is preferable to further include at least one selected from the group consisting of Al2O3, MoS2, SiO2, ZrO2, CuO, SiC, TiO2, and diamond powder having a size of 1 μm or less based on secondary particle D50. In addition, in the above embodiment, it is preferable to further include at least one selected from the group consisting of CNT and graphene.

A cutting oil according to another embodiment of the present invention is prepared by diluting each of the above-described aqueous suspensions with water.

In addition, the cutting fluid is characterized in that it is used in the MQL injection method.

In addition, the cutting oil preferably further includes at least one selected from the group consisting of alkaline ionized water, a rust inhibitor, an antifoaming agent, an antifreezing agent, and a preservative.

An aqueous suspension based on hexagonal boron nitride (hBN) particles and a cutting oil containing the suspension according to an embodiment of the present invention can simultaneously satisfy the lubricating performance of non-aqueous cutting oil and the cooling performance of water-soluble cutting oil.

In addition, carbon neutrality without using oil at all, clean processing that minimizes the amount of cutting oil used, eco-friendly that builds a pleasant working environment such as no waste oil and minimal odor, collects and recycles hexagonal boron nitride (hBN) particles It can function as a cutting fluid in a resource circulation method that

In addition, the aqueous suspension according to an embodiment of the present invention is not limited to the application of cutting oil for metal processing, but can also be applied for the purpose of processing workpieces made of other materials such as plastic.

In addition, the aqueous suspension according to an embodiment of the present invention can be applied to machinery where various types of friction and wear occur through the excellent lubrication function inherent in hexagonal boron nitride (hBN) particles, high thermal conductivity, and release property. It can also be applied as a lubricant.

1 is an electron micrograph showing the size of hexagonal boron nitride (hBN) primary particles,
Figure 2 is the size distribution of hexagonal boron nitride (hBN) secondary particles, which is the result of measuring the powder after synthesis after applying ultrasonic waves and measuring the aqueous suspension processed with a high-pressure homogenizer,
3 is a photograph showing a workpiece processing method for measuring tool wear and surface roughness as a SUS304 workpiece,
Figure 4 is a picture of the cutting process used in Comparative Examples and Examples, showing MQL aerosol atomization spray (left) and Flooding liquid spray (right),
5 is a photograph showing a method for measuring the amount of wear on the clearance surface of an end mill tool;
6 is a surface roughness measurement photograph,
7 is a graph showing the measurement results of tool wear on the end mill spare surface;
8 is a graph showing the results of measuring the surface roughness of a SUS304 workpiece.

Hereinafter, specific embodiments in which the present invention may be practiced will be described in detail by way of example. These embodiments are described in sufficient detail to enable one skilled in the art to practice the present invention. It should be understood that the various embodiments of the present invention are different from each other but are not necessarily mutually exclusive. For example, specific shapes, structures, and characteristics described herein may be implemented in one embodiment in another embodiment without departing from the spirit and scope of the present invention. Accordingly, the detailed description set forth below is not to be taken in a limiting sense, and the scope of the present invention, if properly described, is limited only by the appended claims, along with all equivalents as claimed by those claims.

An aqueous suspension according to an embodiment of the present invention includes water, hexagonal boron nitride (hBN) particles, and a dispersant. It is important to maintain the dispersed state of the hexagonal boron nitride (hBN) particles at a uniform concentration for a long time (more than one day) in such a suspension.

Synthesis of hexagonal boron nitride (hBN) particles

In general, hexagonal boron nitride (hBN) particles have a hydrophobic surface, so they are not well dispersed in water and have poor dispersibility in water, such as floating on the surface of water or sinking to the bottom of the water surface. can't

Therefore, in the present invention, it is not synthesized in a heat treatment furnace in an inert atmosphere such as nitrogen or argon, which is a method commonly prepared using solid boron precursors and nitrogen precursors, and synthesized in an air heat treatment furnace in which the gas atmosphere is not controlled Hexagonal system obtained by synthesizing As boron nitride (hBN) particles, it is preferable to use hydrophilic hBN particles having high dispersibility in water. At this time, it is judged that hydrophilicity is expressed by atomic unit defects on the surface of the particle, dangling bonds, decomposition of water molecules, and resulting hydroxyl groups.

In more detail, boron precursor and nitrogen precursor are mixed in a molar ratio of boron:nitrogen of 1:1, and then synthesized at a temperature of 1600 ° C or less, for example, at 1500 ° C for 3 hours in air in which the gas atmosphere is not controlled. proceed A powder obtained by washing and purifying it is prepared.

1 is an electron micrograph showing the size of hexagonal boron nitride (hBN) primary particles, and the size of the primary particles means the size of single crystal particles observed with a scanning electron microscope.

Figure 2 is the size distribution of hexagonal boron nitride (hBN) secondary particles, measured after synthesizing the powder after applying ultrasonic waves (600W, 35kHz output), and measuring the aqueous suspension processed with a high-pressure homogenizer described below. am. Here, the size of secondary particles is measured by a laser diffraction-based particle size analyzer, and is the size of primary particles (single crystal particles) or aggregated particles in which two or more of them are aggregated. D10, D50, and D90 are factors representing the size distribution of secondary particles as a result of particle size analysis.

In the hexagonal boron nitride (hBN) particles, the primary particles and the secondary particles have a particle range of 30 to 1000 nm, preferably 30 to 500 nm, and more preferably 30 to 250 nm based on D50, and 1 μm or less based on D90 has a particle size. The specific surface area ranges from 10 to 90 m2/g considering the aspect ratio (3 to 10).

If hBN powder of 30 nm or less is used based on D50, the shape of the particle is close to spherical, and the shear direction of the processing surface and the sp2 bonding surface are not parallel, making it difficult to expect excellent lubrication performance during metal processing. This is because the dispersibility of hexagonal boron nitride (hBN) particles in aqueous suspensions and metalworking cutting fluids including them is poor due to the precipitation generated by HBN, and it is difficult to control the concentration of hBN particles during processing, making it difficult to use them as cutting fluids.

The specific surface area of the hBN particles was measured by a general gas adsorption method, and the reason for limiting the range as above is that it is related to the aspect ratio (flatness, 3 to 10) that is out of the sphere. It is desirable to have a relationship.

Preparation of aqueous suspensions

When the hexagonal boron nitride (hBN) powder prepared by the above process is added to water without a dispersant, even if a high shear stirrer is used for a long time of 6 hours or more, precipitation occurs within 24 hours, resulting in uniform hexagonal boron nitride (hBN) powder. ) concentration management is difficult. Accordingly, an aqueous suspension in which more than 90% of hexagonal boron nitride (hBN) particles do not precipitate and exist in a suspended colloidal state even when stored for one day or more using an appropriate dispersant at a weight ratio of 10 or less to the water (solid weight of the dispersant) needs to be manufactured.

The dispersant is preferably an anionic dispersant, but anionic as well as cationic, zwitterionic, nonionic or low molecular weight or polymeric dispersants may be used alone or in combination, but are not limited thereto.

Anionic dispersants include higher fatty acid salts, alkyl sulfonates, α-olefin sulfonates, alkane sulfonates, alkylbenzene sulfonates, sulfosuccinic acid ester salts, alkyl sulfuric acid ester salts, alkyl ether sulfuric acid ester salts, alkyl phosphoric acid ester salts, alkyl There are ether phosphoric acid ester salts, alkyl ether carboxylate salts, α-sulfonated fatty acid methyl ester salts, and methyl taurate salts. These anionic dispersants can be used individually or in combination of 2 or more types.

The cationic dispersant contains quaternary ammonium salts, alkoxylated polyamines, aliphatic amine polyglycol ethers, fatty amines, diamines and polyamines derived from fatty amines and fatty alcohols, imidazolines derived from fatty acids, and salts of these cationic substances. do. These cationic dispersants can be used individually or in combination of 2 or more types.

The zwitterionic dispersant is a dispersant having both an anionic group part in the molecule of the anionic dispersant and a zwitterionic group part in the molecule of the cationic dispersant.

Examples of the nonionic dispersant include polyoxyethylene alkyl ethers, polyoxyethylene alkyl aryl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkylamines, and glycerin fatty acid esters. . These nonionic dispersants can be used individually or in combination of 2 or more types.

The molecular weight of the polymer dispersant can be used without limitation when dissolved in water, but is preferably in the range of 1,000 to 2,000,000, more preferably in the range of 5000 to 1,000,000, more preferably in the range of 10,000 to 500,000, and particularly preferably in the range of 10,000 to 100,000. Unless otherwise indicated herein, molecular weight means weight average molecular weight. Specifically as the polymer dispersant, polyvinylpyrrolidone, polyvinyl alcohol, polyvinyl methyl ether, polyethylene oxide, polyethylene glycol, polypropylene glycol, polyacrylamide, vinyl alcohol-vinyl acetate copolymer, polyvinyl alcohol-partial formalized product , polyvinyl alcohol-partial butyralide, vinylpyrrolidone-vinyl acetate copolymer, polyethylene oxide/propylene oxide block copolymer, polyacrylate, polyvinyl sulfate, poly(4-vinylpyridine) salt, polyamide , polyallylamine salts, condensed naphthalene sulfonates, cellulose derivatives, and starch derivatives. In addition, natural polymers of alginate, gelatin, albumin, casein, gum arabic, gum tragacanth, and ligninsulfonate may be used. In addition, a polymer type dispersing agent having a skeleton of a carboxyl group, an amino group, a hydroxyl group, an ester bond, an amide bond, an aromatic ring, or a heterocyclic ring may be used.

An aqueous suspension according to an embodiment of the present invention includes an anionic dispersant, hexagonal boron nitride (hBN) powder is included in a weight ratio of 10 or less based on 100 water, and the dispersant is usually 10 (dispersant agent) based on 100 water Weight of solid content) weight ratio or less (100 g / L or less compared to the volume of water) can be added. The content of the dispersant may be appropriately selected in consideration of the dilution ratio in water and the content of hBN particles.

In addition, an aqueous suspension according to another embodiment of the present invention includes a first dispersing agent that is an anionic surfactant; and a second dispersing agent which is a nonionic surfactant. Two or more dispersing agents may be used in combination. Hexagonal boron nitride (hBN) powder is included in a weight ratio of 10 or less based on 100 water, and the weight ratio of the first dispersing agent and the second dispersing agent (first dispersing agent / second dispersing agent) may be 1 to 9, preferably It may be 1 to 5, more preferably 1 to 3. The dispersant may be used by adding a weight ratio of 10 (solid weight of the dispersant) or less (100 g/L or less by volume of water) to 100 water. The content of the dispersant may be appropriately selected in consideration of the dilution ratio in water and the content of hBN particles.

In addition, the aqueous suspension according to another embodiment of the present invention includes a first dispersing agent of a polymer; and a second dispersing agent which is an anionic surfactant. Two or more dispersing agents may be used in combination. The hexagonal boron nitride (hBN) powder is included in a weight ratio of 10 or less based on 100 water, the weight ratio of the first dispersing agent and the second dispersing agent (first dispersing agent / second dispersing agent) is 1 to 9, and the suspension An aqueous suspension having an initial viscosity of 500 cP or less is provided. The first dispersing agent used is to ensure that the hBN particles are evenly dispersed in the suspension without aggregation. In addition, the second dispersant prevents aggregation between the main chains of the first dispersant, which is a polymer-based dispersant, and has a crowning effect. When used in combination, the first dispersant and the second dispersant exhibit a synergistic effect on dispersibility, Even after elapsed time, the dispersibility of the suspension is maintained, and improvement in storage stability can be expected. The dispersant may be used by adding a weight ratio of 10 (solid weight of the dispersant) or less (100 g/L or less by volume of water) to 100 water. The content of the dispersant may be appropriately selected in consideration of the dilution ratio in water and the content of hBN particles.

As such, in the aqueous suspension according to an embodiment of the present invention, the content of the hexagonal boron nitride (hBN) powder may be 10 weight ratio or less, preferably 1 weight ratio or less based on 100 water, and usually 10 (dispersant agent) with respect to 100 water It is preferable to use an appropriate dispersant in a weight ratio of less than (100 g/L or less based on the volume of water). Here, the content of the hexagonal boron nitride (hBN) powder may vary depending on the processing environment such as tool material, tool shape, workpiece material, processing method, supply method, and application field, and the aqueous suspension has a low concentration of 0.1 weight ratio or less. may be

If the content of hexagonal boron nitride (hBN) particles exceeds 10 weight ratio, it is not preferable because it does not maintain dispersibility for a long time and accelerates precipitation, and the amount of dispersant added is usually 10 per 100 water (solid content weight of dispersant). If the weight ratio (100 g / L compared to the volume of water) is exceeded, there is a problem of acting as a foreign substance on the workpiece after processing.

As the water used in the aqueous suspension according to an embodiment of the present invention, one or more of distilled water, deionized water, tap water, ground water, and industrial water may be appropriately selected and used. In addition, the water may include electrolytic ionized water having a hydroxyl group, which is prepared by electrolysis of water as alkaline ionized water having a pH of 10 or higher. The alkaline electrolytic ionized water refers to alkaline ionized water generated through electrolysis of water, and is widely used as a substitute for chemicals such as sterilization disinfectants, detergents, detergents, waxes, and pesticides, as well as containing chemicals such as surfactants and alcohol components. Since it is an eco-friendly liquid that is harmless to living organisms, it is used in various fields to reduce or remove various contaminants and inhibit the proliferation of microorganisms.

Specifically, water, hexagonal boron nitride (hBN) particle powder, and dispersant described above are added in appropriate amounts and mixed, and then dispersed through homogenization in a high-pressure homogenizer, etc. It is preferable to prepare an aqueous suspension. .

In addition, the aqueous suspension according to an embodiment of the present invention may further include at least one selected from the group consisting of a rust inhibitor, an antifoaming agent, an antifreezing agent, and a preservative. The mixing ratio and input amount of each of the above components may be appropriately selected depending on the processing environment and field of application, and the dilution amount of water used in manufacturing cutting oil.

First of all, the rust inhibitor added to suppress corrosion such as rust of the workpiece metal workpiece is not particularly limited, and may be used alone or in combination of two or more. For example, an amine-based, organic-based, inorganic, or non-ferrous metal-based rust preventive may be mixed with distilled water, deionized water, or water to prepare a rust preventive solution for use. The rust inhibitor included in the anti-rust solution is at least one selected from the group consisting of diethylamine, triethylamine, cyclohexyl amine, ethanolamine, monoethanolamine, triethanolamine, propanolamine, monopropanolamine, and isopropanolamine as an amine type. It is preferable to use The addition amount is blended in an amount of 1 to 20 weight ratio, preferably 2 to 10 weight ratio, and more preferably 3 to 6 weight ratio, based on 100 deionized water of the rust inhibitor composition. If the amount used is less than 1 weight ratio, it is difficult to expect stable anti-corrosive performance, and if the weight ratio exceeds 20 weight ratio, it may present problems with safety to the skin, breathing and human body. The rust inhibitor included in the rust-preventive solution is an organic carboxylic acid, and the carboxylic acid is preferably one or more selected from the group consisting of sebacic acid, undecanedioic acid, and dodecanedioic acid. When the number of carbon atoms is less than 10, carboxylic acid has poor rust prevention performance, and when it exceeds 12 carbon atoms, it is difficult to dissolve in water. The addition amount is blended in an amount of 0.5 to 7 weight ratio, preferably 1.5 to 4 weight ratio, and more preferably 1 to 2 weight ratio, based on 100 deionized water of the antirust liquid composition. If the carboxylic acid is used in a weight ratio of less than 0.5, it is difficult to exhibit rust prevention performance, and if it is used in a weight ratio of more than 7, it is difficult to expect improvement in rust prevention performance compared to the amount used. Among the rust inhibitors contained in the anti-rust liquid, the inorganic type may be a sodium salt, potassium salt, chromium salt, or ammonium salt of an inorganic acid such as sulfuric acid or phosphoric acid. The amount added is 0.4 to 6 weight ratio, preferably 1.5 to 4 weight ratio, more preferably 2.5 to 3 weight ratio, based on 100 deionized water of the antirust liquid composition. If the above inorganic type is used in a weight ratio of less than 0.4, it is difficult to exhibit rust prevention performance, and if it is used in a weight ratio of more than 6, it is difficult to expect improvement in rust prevention performance compared to the amount used. Among the rust inhibitors included in the rust preventive solution, the non-ferrous metal rust preventive may be benzotriazole, tolytriazole, or mercaptobenzotriazole. The addition amount is blended in an amount of 0.2 to 3 weight ratio, preferably 0.3 to 2 weight ratio, and more preferably 0.5 to 1 weight ratio, based on 100 deionized water of the rust inhibitor composition. If the added amount is less than 0.2 weight ratio, it is difficult to exert an anti-corrosion effect, and if the weight ratio exceeds 3 weight ratio, it is harmful to the human body and safety problems for environmental pollution may appear. A rust preventive solution composed of a rust preventive agent using one or more of the above various rust preventive agents alone or in combination and water is preferably added in an amount of not more than 30 weight ratio with respect to 100 parts of the aqueous suspension. The amount of the anti-rust solution may further increase as the dilution ratio in water increases.

An antifoaming agent may be additionally added to suppress bubbles generated during the manufacturing process of the aqueous suspension and the cutting process using the cutting oil containing the same. The antifoaming agent may be used alone or in combination of two or more silicone-based antifoaming agents such as polydimethylsiloxane, modified polydimethylsiloxane, organic silicon derivatives, silicon-based ethoxides, and silica, and 0.1 to 1 weight ratio is added to 100 of the aqueous suspension. When it is added in a weight ratio of less than 0.1, it is difficult to expect antifoaming performance, and when it is added in a weight ratio exceeding 1 weight ratio, the disadvantage of remaining on the surface of the workpiece metal workpiece occurs. The amount of the antifoaming agent added to the aqueous suspension may further increase as the dilution ratio in water increases.

Since the aqueous suspension and the cutting oil containing the same are used in multiple cutting processes, microorganisms proliferate and cause odor, so preservatives that can be additionally added to prevent this, especially in summer, are sodium benzoate, BIT (Benzisothiazolinone)-based compounds, tree Azine compounds, benzotriazole compounds, tolyltriazole compounds, and the like can be used. The preservative is preferably added in an amount of 10% or less by weight based on 100% of the aqueous suspension, and when less than 1% by weight is added, it is difficult to expect antiseptic performance. These antiseptic|preservatives can be used individually or in combination of 2 or more types. In addition, the amount of the preservative added to the aqueous suspension may further increase as the dilution ratio in water increases.

An anti-freezing agent may be additionally added so that the aqueous suspension and the cutting oil containing the same can be used even at a temperature of 0 degrees or less in winter. The anti-freezing agent may include one or more components selected from propylene glycol or ethylene glycol. Based on 100% of the aqueous suspension containing the hexagonal boron nitride particles, propylene glycol (Propylene Glycol) may be appropriately selected according to the freezing point at a mixing ratio of 25 or less by weight. The amount of the cryoprotectant added to the aqueous suspension may further increase as the dilution ratio in water increases.

In addition, the aqueous suspension according to an embodiment of the present invention may further include one or more selected from the group consisting of Al2O3, MoS2, SiO2, ZrO2, CuO, SiC, TiO2, and diamond powder. It is preferable that the above components have a size of 1 μm or less based on secondary particle D50. In addition, one or more selected from the group consisting of CNT and graphene may be further included. The role of these additional components complements the lubrication mechanism due to the inherent characteristics of hBN particles.

Manufacturing of cutting oil

Cutting oil according to an embodiment of the present invention is prepared by diluting the above-described aqueous suspension with water in an appropriate ratio to meet the use environment or processing purpose. The amount of water to be diluted is usually 10 to 20 times that of the aqueous suspension, but it may be less or more depending on the processing environment such as tool material, tool shape, workpiece material, processing method, supply method, and application field.

In addition, the cutting oil may further include one or more selected from the group consisting of alkaline electrolyzed water, a rust inhibitor, an antifoaming agent, an antifreezing agent, and a preservative depending on conditions such as a use environment or region. Specifically, the cutting oil is prepared by adjusting and mixing the mixing ratio so that the content of water or alkaline electrolyzed water is 34% or more, the aqueous suspension is 10% or less, the anticorrosive solution is 20% or less, the antifreezing agent is 25% or less, the antifoaming agent is 1% or less, and the preservative is 10% or less by weight. can do.

Cutting performance test

In order to confirm the cutting performance of the cutting oil according to an embodiment of the present invention, the test was conducted by preparing examples and comparative examples as follows.

First, for use in Examples and Comparative Examples, a boron precursor and a nitrogen precursor were mixed in a molar ratio of boron:nitrogen of 1:1, and then synthesis was performed at a temperature of 1500 ° C. for 3 hours in air without controlling the gas atmosphere. A powder obtained by washing and purification was prepared.

(Example 1)

After preparing by mixing 10L of water, 200g of hexagonal boron nitride (hBN) powder prepared above, and 100g of dispersing agent Aerosol OT-100, proceed 5 times at a rate of 0.1L/min with a low pressure cycle of about 7000psi in a high pressure homogenizer and high pressure of about 15000psi A cutting oil was prepared by diluting 15 g of an aqueous suspension prepared by dispersing and processing twice in a cycle and diluting it with 3 L of tap water. This was put into the MQL feeder and sprayed on the processing area.

(Example 2)

After preparing by mixing 10L of water, 200g of hexagonal boron nitride (hBN) powder prepared above, and 100g of dispersing agent Aerosol OT-100, proceed 5 times at a rate of 0.1L/min with a low pressure cycle of about 7000psi in a high pressure homogenizer and high pressure of about 15000psi A cutting oil was prepared by diluting 45 g of an aqueous suspension prepared by dispersing and processing in a cycle twice and diluting it with 3 L of tap water. This was put into the MQL feeder and sprayed on the processing area.

(Example 3)

After preparing by mixing 10L of water, 200g of hexagonal boron nitride (hBN) powder prepared above, and 100g of dispersing agent Aerosol OT-100, proceed 5 times at a rate of 0.1L/min with a low pressure cycle of about 7000psi in a high pressure homogenizer and high pressure of about 15000psi A cutting oil was prepared by diluting 15 g of the aqueous suspension prepared by dispersing and processing in a cycle twice and diluting it with 300 g of alkaline electrolyzed water (pH11) and 3 L of tap water. Here, the reason why the alkaline electrolyzed water is added separately is to increase the pH to impart water-based sterilization and cleaning effects. This was put into the MQL feeder and sprayed on the processing area.

(Comparative Example 1) Alkaline Electrolyzed Water

A cutting oil was prepared by preparing 3 L of alkaline electrolytic water having a pH of 11 without any additives.

(Comparative Example 2) Aqueous solution consisting only of water and hexagonal boron nitride (hBN) particles

After adding 200 g of hexagonal boron nitride (hBN) prepared above to 10 L of distilled water, proceed 5 times at a rate of 0.1 L/min with a low pressure cycle of about 7000 psi in a high pressure homogenizer in the same manner as in the above examples, and about 15000 psi An aqueous suspension prepared by dispersion processing was prepared by performing two high-pressure cycles. However, after 24 hours, most of the hexagonal boron nitride (hBN) particles were precipitated by 50% or more, and the desired cutting oil could not be prepared.

(Comparative Example 3) O/W emulsion type water-soluble cutting oil atomized spraying by MQL supply method

Cutting oil was prepared by diluting 300 g of commercially available O/W emulsion type water-soluble cutting oil OLEX CUT 7500FE with 3 L of tap water, and it was injected into the MQL feeder and sprayed on the machined area.

(Comparative Example 4) Liquid spraying of O/W emulsion type water-soluble cutting oil by Flooding supply method

Cutting oil was prepared by diluting 5 liters of commercially available O/W emulsion type water-soluble cutting oil OLEX CUT 7500FE with tap water more than 10 times, and it was injected into the flooding low-pressure pump supply and sprayed on the processing part.

The particle size distribution of the hexagonal boron nitride (hBN) described above and the dispersibility of each Example and Comparative Example are shown in Table 1 below.

In each of the examples, the hBN particles maintained a colloidal state even after 1 day, but in the case of Comparative Example 2 in which no dispersant was used under the same conditions, after 24 hours, more than 50% of the hexagonal boron nitride (hBN) particles precipitated, Since it cannot be used as a cutting oil, the following cutting performance test was not conducted.

The cutting ability test was conducted as follows using the remaining cutting oils except for Comparative Example 2. The milling machine tool used for the cutting performance test was a Doosan NX6500II machining center, the workpiece metal workpiece was SUS304 100x100x70 (mm3), and the tool was a YG1 10 pi 4-blade end mill. The tool wear of the end mill was measured with Keyence VHX5000, and the surface roughness of the workpiece surface was measured with Mitutoyo SJ201. The cutting oil atomization MQL supplier sprayed the WINMIST equipment at a speed of 400cc/hr to the processing area, and the flooding supplier sprayed it to the processing area using a general low pressure pump. Milling cutting process conditions were set as shown in Table 2 below.

The workpiece was subjected to side milling, and the maximum value was recorded by measuring 3 points of wear on the free surface of the end mill in units of 1 pass (10 m). The end of the cutting process was set at the end mill free surface wear of 0.2 mm or more or when the processing distance reached 80 m (8 passes).

3 is a SUS304 workpiece, a photograph showing a workpiece processing method for measuring tool wear and surface roughness, and FIG. 4 is a cutting process photograph showing MQL aerosol atomization spray (left) and Flooding liquid spray (right), and FIG. 5 is an end It is a photograph showing the method of measuring the wear amount of the spare surface of the mill tool, and FIG. 6 is a photograph of measuring surface roughness (surface roughness).

In relation to the supply method of cutting oil during cutting, in the MQL (Minimal Quantity Lubrication) supply method used in Comparative Examples 1, 3, and Examples, each manufactured cutting oil is supplied to the same MQL equipment. It was injected into the aerosol and sprayed on the cutting part. In addition, in the flooding spraying method used in Comparative Example 4, the liquid was sprayed to the cutting area by the flooding supply method through a low pressure pump.

As a result of the above cutting performance test, when only alkaline electrolytic water was used as a cutting oil as in Comparative Example 1, it was difficult to cut the metal workpiece and the tool wear was severe, so the initial cutting process was stopped. It was judged that the cutting process was not performed smoothly only with the cooling function without the lubrication function.

In the case of Comparative Example 3 using commercially available O/W emulsion-type water-soluble cutting oil, smoke was generated during the processing and a smell like burning oil was generated. Therefore, it was confirmed that the oil-based cutting fluid is difficult to apply to the MQL spraying method.

7 is a graph showing the measurement results of tool wear on the free surface of the end mill, and FIG. 8 is a graph showing the measurement results of the surface roughness of the SUS304 workpiece.

As can be seen in FIG. 7, Examples 1, 2, and 3 showed stable performance without rapid tool wear up to 7 pass (70 m), whereas Comparative Examples 3 and 4 showed a rapid increase in tool wear at 6 pass (60 m) or less. . This seems to explain the excellent tool wear reduction effect of the hexagonal boron nitride (hBN)-based cutting fluid according to an embodiment of the present invention. Even at a low concentration of less than 0.1 weight ratio of hBN particles to 100 water, MQL atomization (Comparative Example 3) and Flooding liquid spray (Comparative Example 4) of the existing O/W emulsion-type water-soluble cutting oil show relatively excellent cutting performance regardless of the supply method. will be. That is, it shows that the water-based suspension composed of water, hBN, and dispersant works as a metalworking cutting fluid with better performance than the conventional O/W emulsion-type water-soluble cutting fluid.

Figure 8 shows the surface roughness (surface roughness) measurement results after completion of cutting for Comparative Examples 3 and 4 and Examples 1, 2 and 3. The examples show a surface roughness of less than 0.3um, whereas the comparative examples show a relatively high surface roughness of 0.4um or more by 30% or more. This explains the excellent processing precision improvement effect of the hBN aqueous suspension according to an embodiment of the present invention, even at a low concentration of 0.1 weight ratio of hBN particles to 100 water, MQL atomization of conventional O / W emulsion type water-soluble cutting oil (comparative example 3) and Flooding liquid spraying (Comparative Example 4) shows excellent processing precision regardless of the supply method. That is, it shows that the water-based suspension composed of water, hBN, and dispersant works as a metalworking cutting fluid with better performance than O/W emulsion-type water-soluble cutting fluid. In summary, the water-diluted aqueous suspension consisting of water, hBN particles, and dispersant showed superior cutting performance (processing precision of the workpiece, wear of the tool) compared to the existing water-soluble cutting oil of the O/W emulsion type.

In addition, through additional experiments, at least one of alkaline electrolyzed water, metal rust preventive, anti-freezing agent, antifoaming agent, and preservative was added to improve the surface roughness of the metal workpiece and tool wear, as well as to satisfy the anti-corrosion, anti-freeze, anti-foam, and sterilization effects. confirmed that This shows that it is eco-friendly because it does not contain oil components for metal processing and can be applied to ultra-trace lubrication processing. The aqueous suspension according to an embodiment of the present invention is not limited to the application of the metal processing cutting oil as described above, but can also be applied for the purpose of processing a workpiece made of other materials such as plastic. In addition, it can be applied as a lubricant that can be applied to machinery that generates various types of friction and wear through hBN's unique excellent lubrication function, high thermal conductivity, and releasability.

Claims (12)

Including water, hexagonal boron nitride (hBN) particles, and a dispersant,
The hexagonal boron nitride (hBN) particles are aqueous suspensions in which primary and secondary particles have a particle size in the range of 30 to 250 nm based on D50 and less than 1 μm based on D90 through application of ultrasonic waves for 24 hours.
The method of claim 1,
The hexagonal boron nitride (hBN) particles are water-wettable hydrophilic particles, an aqueous suspension
The method of claim 1,
The hexagonal boron nitride (hBN) particles are particles synthesized at a temperature of 1600 ° C. or less in an air heat treatment furnace that does not control the gas atmosphere, an aqueous suspension
delete The method of claim 1,
An aqueous suspension in which the hexagonal boron nitride (hBN) particles are mixed at a weight ratio of 10 or less to the water, and the dispersant is mixed at a weight ratio of 10 or less (solid weight of the dispersant) to the water.
The method of claim 1,
An aqueous suspension, wherein the water comprises alkaline ionized water of pH 10 or higher
The method of claim 1,
The dispersant is an aqueous suspension using one or more selected from the group consisting of anionic, cationic, zwitterionic, and nonionic dispersants alone or in combination.
The method of claim 1,
Aqueous suspension further comprising at least one selected from the group consisting of rust inhibitors, antifoaming agents, antifreezing agents, and preservatives
The method of claim 1,
An aqueous suspension further comprising at least one selected from the group consisting of Al2O3, MoS2, SiO2, ZrO2, CuO, SiC, TiO2, diamond powder, CNT, and graphene having a secondary particle size of 1 um or less based on D50
A cutting oil obtained by diluting an aqueous suspension according to any one of claims 1 to 3 and 5 to 9 with water.
The method of claim 10,
The cutting oil is a cutting oil used in the MQL injection method.
The method of claim 10,
A cutting oil further comprising at least one selected from the group consisting of alkaline ionized water, rust inhibitor, antifoaming agent, antifreezing agent, and preservative.

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