JP7580211B2 - Metalworking oil composition and metalworking method - Google Patents

Description

The present invention relates to a metalworking oil composition and a metalworking method. More specifically, the present invention relates to a metalworking oil composition that suppresses the elution of metals, particularly copper-based or zinc-based metals, and has excellent corrosion prevention properties, and to a metalworking method using this metalworking oil composition.

Water-soluble metalworking oil compositions are used in the field of metalworking, such as cutting and grinding. Water-soluble metalworking oil compositions are generally made by blending base oil, surfactant, antioxidant, water, etc. according to the purpose, and are often further diluted with water before use, for example as a coolant liquid. This causes the problem that the material to be worked is easily corroded.

Therefore, in order to suppress corrosion of the workpiece, a corrosion inhibitor has been conventionally blended into metalworking oil compositions. The corrosion inhibitor has the effect of preventing the metal of the workpiece from dissolving as ions into the water contained in the metalworking oil composition. Patent Document 1 discloses a rust inhibitor composition containing an oil-soluble organometallic salt, benzotriazole, and an organic amine as corrosion inhibitor components. According to Patent Document 1, the rust inhibitor composition uses an oil-soluble organometallic salt in combination with benzotriazole, which allows the formation of a multiple rust inhibitor layer of the oil-soluble organometallic salt while maintaining a strong bond due to the complex formation between benzotriazole and the metal, and exhibits excellent corrosion inhibitor performance even when the content of the rust inhibitor in the water dilution is very small. It is also described that the rust inhibitor composition of Patent Document 1 can exhibit extremely stable corrosion inhibitor performance not only for aluminum alloys with high aluminum purity, but also for aluminum alloys such as aluminum die castings containing a large amount of copper.

Furthermore, when disposing of water-soluble metalworking oil compositions, treatment is required to remove organic matter, metals, etc. from the coolant liquid and to discharge clean water below the wastewater standard values set by the ordinances of each river, which places a heavy burden on wastewater treatment. From this perspective, Patent Document 2 discloses a water-soluble cutting oil that contains a mineral oil or synthetic oil with an aniline point of 85 to 110°C, an amine, an organic acid, and a nonionic surfactant. According to Patent Document 2, the water-soluble cutting oil has good wastewater treatability and can reduce equipment attack.

Patent No. 6286642 Patent No. 5916589

As mentioned above, benzotriazole is used as a corrosion inhibitor, but the corrosion inhibitor effect is limited to certain metal materials, and there is a problem that the corrosion inhibitor effect is not sufficient especially for brass. In addition, metalworking oil compositions containing mineral oils or synthetic oils with aniline points of 85°C or higher have problems with poor emulsification and stability.

The present invention was made in consideration of the current state of the prior art described above, and its main objective is to provide a metalworking oil composition that suppresses metal elution and has excellent corrosion prevention properties, and a metalworking method that uses this metalworking oil composition.

The present inventors have conducted extensive research to solve the above problems. As a result, they have found that a metalworking oil composition containing a mineral oil having an aniline point within a specific range can suppress the elution of copper into the metalworking oil composition or into a dilution of the metalworking oil composition. The present invention was completed based on these findings.

That is, the metalworking oil composition according to one embodiment of the present invention includes an oil-in-water emulsion containing a mineral oil having an aniline point of 60°C or more and 84°C or less, and water. Here, the aniline point is the minimum temperature at which equal volumes of aniline and a hydrocarbon or a mixture of hydrocarbons exist as a homogeneous solution, and is a value measured according to JIS K2256.

In the above-mentioned metalworking oil composition, the mineral oil may include a paraffinic mineral oil having a sulfur content of 0.2% by weight or less.

The metalworking oil composition may contain naphthenic mineral oil with a sulfur content of 0.07% by weight or less.

A metalworking method according to one aspect of the present invention uses any of the metalworking oil compositions described above to process a metal material.

In the above-mentioned metal processing method, the metal material may be a copper-based metal material or a zinc-based metal material.

The present invention provides a metalworking oil composition that suppresses metal elution and has excellent corrosion prevention properties, and a metalworking method that uses this metalworking oil composition.

1 is a graph showing the relationship between the amount of copper eluted and the average oil droplet diameter. 1 is a graph showing the relationship between the amount of zinc dissolved and the average oil droplet diameter.

The following describes an embodiment of the present invention in detail.

In this specification, unless otherwise specified, the unit "%" for content or blend ratio means "% by weight."

1. Metal Working Oil Composition The metal working oil composition according to the embodiment of the present invention comprises an oil-in-water emulsion containing a mineral oil having an aniline point of 60° C. or more and 84° C. or less, and water.
The composition of the metal working oil composition according to the embodiment will be specifically described below.

The metalworking oil composition according to the embodiment contains a mineral oil having an aniline point of 60°C or more and 84°C or less as a base oil. Mineral oils are mixtures of hydrocarbons having various chemical structures, and are classified into paraffinic mineral oils, naphthenic mineral oils, and aromatic mineral oils depending on the main component hydrocarbon. In the present invention, it is preferable to use paraffinic mineral oils and naphthenic mineral oils, and it is more preferable to use paraffinic mineral oils. The mineral oils may be used alone or in combination of two or more types.

The content of the base oil in the metal working oil composition according to the embodiment is preferably, for example, 40% or more and 85% or less of the total amount of the base oil based on the total amount of the metal working oil composition. In this case, the elution of metal is more effectively suppressed, the corrosion prevention properties are improved, and the stability of the metal working oil composition is improved. The lower limit of the total amount of the base oil is more preferably 45%, and even more preferably 50%. The upper limit of the total amount of the base oil is more preferably 80%, and even more preferably 75%.

The metalworking oil composition according to the embodiment may contain other base oils as appropriate, provided that the object of the present invention is not impaired. The other base oils may be either natural or synthetic, and examples of such base oils include vegetable oils and fatty acid esters. In addition to the base oil, the metalworking oil composition may further contain, as an oil component, for example, fatty acids, fatty acid condensation products, and the like.

When the metalworking oil composition contains oily components other than the base oil, from the viewpoint of further enhancing the effect of the present invention, the content of the base oil is preferably 0.6 parts by mass or more in total per 1 part by mass of the total amount of the oily components, more preferably 0.7 parts by mass or more, and even more preferably 0.8 parts by mass or more.

The mineral oil contained in the metalworking oil composition according to the embodiment satisfies the condition that the aniline point is 60°C or more and 84°C or less as described above. When the aniline point of the mineral oil is within the above range, the effect of suppressing the elution of metal (workpiece) into the metalworking oil composition or a dilution solution of the metalworking oil composition is significantly exhibited, and an excellent anticorrosion effect can be exhibited. Furthermore, discoloration of the metalworking oil composition can be prevented, and the emulsification and stability of the metalworking oil composition can be improved. The lower limit of the aniline point is preferably 65°C, 70°C, and 80°C, in that order. From the viewpoint of the emulsification and stability of the metalworking oil composition, when the mineral oil is a naphthenic mineral oil, the upper limit of the aniline point is preferably 70°C.

In an embodiment, it is preferable that the amount of impurities contained in the mineral oil is small, that is, the purity of the mineral oil is high. The amount of impurities contained in the mineral oil can be set appropriately depending on the type of mineral oil, but for example, when the mineral oil is a paraffin-based mineral oil, the content of sulfur element, which is the main impurity, is preferably 0.2% or less of sulfur element based on the total amount of paraffin-based mineral oil. In this case, the amount of impurities such as sulfur element can be reduced, and the elution of metals can be effectively suppressed. The content of sulfur element in paraffin-based mineral oil is more preferably 0.18% or less, and even more preferably 0.16% or less.

For example, when the mineral oil is naphthenic mineral oil, the content of the sulfur element, which is the main impurity, is preferably 0.07% or less of the sulfur element based on the total amount of naphthenic mineral oil. In this case, the amount of impurities such as sulfur element can be reduced, and the elution of metals can be effectively suppressed. The content of sulfur element in paraffinic mineral oil is more preferably 0.05% or less, and even more preferably 0%.

In this specification, impurities such as elemental sulfur in mineral oils can be measured by X-ray fluorescence analysis (XRF), inductively coupled plasma (ICP) emission spectrometry, etc.

The metalworking oil composition according to the embodiment contains water. The water used may be tap water, industrial water, ion-exchanged water, distilled water, or the like, and the water may be hard water or soft water. The water content in the metalworking oil composition of the present invention may generally be 1% or more and 5% or less of the total amount of water based on the total amount of the metalworking oil composition.

The metalworking oil composition according to the embodiment preferably further contains a surfactant. The surfactant may be a nonionic surfactant, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, or the like. Among them, it is preferable to use a nonionic surfactant from the viewpoint of dispersibility. The surfactant may be used alone or in any combination of two or more kinds.

Examples of nonionic surfactants include glycerin fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxysorbitol fatty acid esters, polyoxyalkylene ethers, polyoxyalkylene alkyl ethers, etc. Among these, polyoxyalkylene alkyl ethers are preferred. Examples of polyoxyalkylene alkyl ethers include polyoxyalkylene oleyl ethers, polyoxyalkylene oleyl cetyl ethers, polyoxyalkylene lauryl ethers, etc. Examples of polyoxyalkylene oleyl ethers include polyoxyethylene oleyl ethers. Examples of polyoxyalkylene lauryl ethers include polyoxyethylene lauryl ethers.

The content of the surfactant in the metalworking oil composition can be set appropriately depending on the type of surfactant, the type and content of other blended components, etc. For example, the content of the surfactant is preferably set to 0.01% or more and 9.0% or less of the total amount of the surfactant based on the total amount of the metalworking oil composition. In this case, the oil droplet size can be adjusted within an appropriate range, the emulsion stability of the metalworking oil composition can be improved, and the elution of metal can be effectively suppressed.

The metalworking oil composition according to the embodiment can be obtained by mixing and stirring the base oil containing the mineral oil, water, and a surfactant to prepare an oil-in-water emulsion.

The metalworking oil composition according to the embodiment may contain various additives such as antioxidants, rust inhibitors, anticorrosive agents, preservatives, antifoaming agents, and extreme pressure additives, as necessary.

Examples of antioxidants include amine-based antioxidants, phenol-based antioxidants, zinc dialkyldithiophosphate, zinc diallyldithiophosphate, organic sulfides, etc. One type of antioxidant may be used alone, or two or more types may be mixed and used. When an antioxidant is included, the content thereof can be generally 1% or more and 10% or less of the total amount of the antioxidant based on the total amount of the metalworking oil composition.

Examples of rust inhibitors include organic amines, aliphatic monocarboxylic and dicarboxylic acids having 6 to 36 carbon atoms and their amides, alkenylsuccinic acids having 6 to 36 carbon atoms and their amides, aromatic carboxylic acids, benzotriazoles, etc. Rust inhibitors may be used alone or in combination of two or more. When a rust inhibitor is included, its content can usually be 0.01% or more and 3% or less of the total amount of rust inhibitor based on the total amount of the metalworking oil composition.

Examples of corrosion inhibitors include phosphate esters, alkylphosphonic acids, sodium metasilicate, etc. One type of corrosion inhibitor may be used alone, or two or more types may be mixed and used. When a corrosion inhibitor is included, the content thereof can usually be 1% or more and 5% or less of the total amount of the corrosion inhibitor based on the total amount of the metalworking oil composition.

Examples of preservatives include triazine compounds, thiazoline compounds, and phenol compounds. The preservatives may be used alone or in combination of two or more. When a preservative is included, the content of the preservative may be generally 0.001% or more and 3% or less of the total amount of the preservative based on the total amount of the metalworking oil composition.

Antifoaming agents include polyorganosiloxanes having a molecular weight of 100 to 1,000. Antifoaming agents may be used alone or in combination of two or more. When an antifoaming agent is included, its content may generally be 0.001% or more and 1% or less of the total amount of antifoaming agent based on the total amount of the metalworking oil composition.

Extreme pressure additives include sulfur compounds such as lead soap and sulfurized fatty acids, chlorine compounds such as chlorinated paraffins, and phosphorus compounds. Extreme pressure additives may be used alone or in combination of two or more types.

The metalworking oil composition according to the embodiment is water-soluble and can be used as is for processing metal materials. In addition, the metalworking oil composition according to the embodiment can be used as a stock solution and further diluted with a diluent such as water to obtain a coolant for processing metal materials.

When the metalworking oil composition according to the embodiment is used diluted with a diluent, the dilution ratio may be appropriately adjusted depending on the composition of the metalworking oil composition and the performance required during metalworking. When used diluted, it is usually used at a dilution ratio of 1.5 to 100 times. From the viewpoint of further enhancing the effects of the present invention and improving the processing characteristics, the dilution ratio is preferably 5 to 50 times, more preferably 10 to 30 times.

The pH of the metalworking oil composition of the present invention during use is preferably 8.0 to 9.0, more preferably 8.2 to 8.9. When the pH of the water-diluted solution of the metalworking oil composition is in the above range, the metal elution suppression effect is excellent, the corrosion prevention properties are improved, and the water-diluted solution is effectively prevented from spoiling.

The average oil droplet diameter of the metalworking oil composition according to the embodiment is preferably 90 nm or more and 350 nm or less. When the average oil droplet diameter of the metalworking oil composition is within the above range, the effect of suppressing the elution of metal (workpiece) into the metalworking oil composition or a dilution of the metalworking oil composition is exhibited, and the stability of the oily components is improved.

The metalworking oil composition according to the embodiment can be used for machining, such as cutting, grinding, polishing, and cutting of metal materials. Examples of the metals to be machined include non-ferrous metals and alloys thereof, such as Inconel, titanium, titanium alloys, aluminum, aluminum alloys, magnesium, magnesium alloys, copper, and copper alloys. In particular, when the metalworking oil composition of the present invention is applied to copper-based metals, zinc-based metals, and alloys thereof, such as brass, which are easily corroded and have low corrosion prevention effects from conventional corrosion inhibitors and rust inhibitors, the metal elution suppression effect is satisfactorily exhibited.

2. Metalworking method The metalworking method according to the embodiment of the present invention uses the metalworking oil composition according to the embodiment described above to process a metal material. Metal material processing includes cutting, grinding, polishing, and cutting. When the metalworking oil composition is supplied to a processing point in, for example, a liquid or mist form, it exhibits an effect of suppressing the elution of the metal material into the metalworking oil composition, and can improve corrosion resistance.

The types of metals to be processed include, for example, the metals mentioned above. In particular, when the metal processing method of the present invention is applied to copper-based metals, zinc-based metals, and alloys thereof, such as brass, which are easily corroded and have low corrosion prevention effects from conventional anticorrosives and rust inhibitors, it is preferable because it effectively suppresses the elution of metals.

The present invention will be described in more detail below with reference to examples and comparative examples, but it is not intended that the present invention be limited to these examples.

[Example 1]
<Preparation of metalworking oil composition>
As the mineral oil, mineral oil A (naphthenic mineral oil) whose physical properties are shown in Table 1 below was used. The composition of the mineral oil was analyzed using an X-ray fluorescence analyzer (EDX-8100, manufactured by Shimadzu Corporation). The analysis results are also shown in Table 1. Specifically, the contents of the main impurities S, Ag, and Hf were analyzed, and the contents of these impurities were subtracted to calculate the remainder as resin.

According to the composition shown in Table 2 below and the surfactant composition shown in Table 3 below, a metalworking oil composition of Example 1 was prepared.
The surfactants shown in Table 3 are as follows:
Surfactant A: polyoxyalkylene lauryl ether Surfactant B: polyoxyalkylene oleyl cetyl ether Surfactant C: polyoxyethylene oleyl ether Surfactant D: polyoxyalkylene lauryl ether There are no particular limitations on the method for preparing the metalworking oil composition, and the metalworking oil composition was prepared by sequentially adding each component at room temperature and appropriately stirring using a general stirring method.

[Examples 2 to 4]
Metalworking oil compositions of Examples 2 to 4 were prepared in the same manner as in Example 1, except that the blending ratios of the surfactants were as shown in Table 3.

[Examples 5 to 8]
The metalworking oil compositions of Examples 5 to 8 were prepared in the same manner as in Example 1, except that mineral oil B (paraffinic mineral oil) shown in Table 1 above was used as the mineral oil and the blending ratio of the surfactant was as shown in Table 3.

[Comparative Examples 1 to 4]
Metalworking oil compositions of Comparative Examples 1 to 4 were prepared in the same manner as in Example 1, except that mineral oil C (naphthenic mineral oil) shown in Table 1 above was used as the mineral oil and the blending ratio of the surfactant was as shown in Table 3.

<Oil droplet size measurement>
The average oil droplet size of each metalworking oil composition was measured after preparation. The average oil droplet size was measured using a particle size measuring device ("ELSZ-1000" (Otsuka Electronics Co., Ltd.)) that uses dynamic light scattering (photon correlation method). The measurement results of Examples 1 to 8 and Comparative Examples 1 to 4 are shown in Table 3 above.

<Metal elution inhibition test>
The test solution used was the sample stock solution in Table 2 diluted 5% with water and adjusted to a pH of about 8.85. 5 g of brass grinding powder was added to 20 g of each of the water-diluted solutions of the above Examples and Comparative Examples, and the solution was left to stand at 50°C for one week, filtered using filter paper, and the copper and zinc concentrations in the filtrate were measured using an atomic absorption spectrophotometer. The copper and zinc concentrations (mg/L) in the filtrate were taken as the amounts of copper and zinc eluted (mg/L), respectively. The amount of elution was measured using an atomic absorption spectrophotometer ("AA240FS" (manufactured by Agilent Technologies)) using the atomic absorption method. The test results of Examples 1 to 8 and Comparative Examples 1 to 4 are shown in Table 4 below.
Figures 1 and 2 are prepared based on Tables 3 and 4. Figure 1 is a graph showing the relationship between the amount of copper eluted and the average oil droplet diameter. The vertical axis of Figure 1 shows the amount of copper eluted (unit: mg/L), and the horizontal axis shows the average oil droplet diameter (unit: nm). Figure 2 is a graph showing the relationship between the amount of zinc eluted and the average oil droplet diameter. The vertical axis of Figure 2 shows the amount of zinc eluted (unit: mg/L), and the horizontal axis shows the average oil droplet diameter (unit: nm).

As is clear from Table 4 and Figures 1 and 2 above, in the test solutions of Examples 1 to 8, in which the aniline point of the mineral oil in the metalworking oil composition is in the range of 60°C to 84°C, the amount of copper and zinc eluted into the diluted solution of the metalworking oil composition is reduced. In contrast, in the test solutions of Comparative Examples 1 to 4, in which the aniline point of the mineral oil in the metalworking oil composition is outside the range of 60°C to 84°C, the effect of suppressing the elution of copper and zinc is not sufficient.

As is clear from Figures 1 and 2, as the average oil droplet size increases, the amount of copper and zinc eluted decreases. When comparing oils with similar average oil droplet sizes, the amount of copper and zinc eluted decreases in the order of mineral oil C, mineral oil A, and mineral oil B. This shows that paraffinic mineral oils are more effective at inhibiting metal elution than naphthenic mineral oils, and that for the same type of naphthenic mineral oil, oils with higher aniline points are more effective at inhibiting metal elution. The lower limits of the aniline points of mineral oils are preferably 65°C, 70°C, and 80°C, in that order. For naphthenic mineral oils, the aniline point is preferably 70°C or lower.

In addition, the amount of copper and zinc eluted was lower when mineral oil A was used than when mineral oil C was used, which shows that reducing impurities in the same type of naphthenic mineral oil effectively suppresses the elution of metals. The sulfur element content in naphthenic mineral oil is preferably 0.07% by weight or less. In addition, since the elution of metals is effectively suppressed in mineral oil B as well, the sulfur element content in paraffinic mineral oil is preferably 0.2% by weight or less.

The embodiments disclosed herein are illustrative in all respects and are not limiting. The scope of the present invention is defined by the claims, and includes all modifications within the meaning and scope of the claims.

Claims (4)

The present invention includes an oil-in-water emulsion comprising a mineral oil having an aniline point of 60° C. or more and 84° C. or less, and water,
The metal working oil composition , wherein the mineral oil comprises a paraffinic mineral oil having a sulfur content of 0.2 wt % or less . The present invention includes an oil-in-water emulsion comprising a mineral oil having an aniline point of 60° C. or more and 84° C. or less, and water,
The metalworking oil composition, wherein the mineral oil comprises a naphthenic mineral oil having a sulfur content of 0.07% by weight or less. A metalworking method comprising the step of working a metal material by using the metalworking oil composition according to claim 1 or 2 . 4. The method for processing metals according to claim 3 , wherein the metal material is a copper-based metal material or a zinc-based metal material.

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