Water-soluble functional fluid, undiluted solution of water-soluble functional fluid, water-soluble functional fluid sterilization device, and water-soluble functional fluid sterilization method

Abstract

A water-soluble functional fluid that: contains an antioxidant and a neutral photosensitizer including an isoalloxazine skeleton; and is characterized by the antioxidant being a radical scavenger or a peroxide decomposer.

Description

[Technical Field]

[0001] The present disclosure relates to an aqueous functional fluid, a concentrate of the aqueous functional fluid, a sterilization device for the aqueous functional fluid, and a sterilization method for the aqueous functional fluid. [Background technology]

[0002] When performing metal processing such as cutting, grinding, plastic processing, etc., processing oils are used to lubricate and cool the area between the processing tool and the workpiece. There are oil-based processing oils and water-soluble processing oils, but water-soluble processing oils are mainly used because they provide efficient cooling and can prevent fires during processing even with unmanned machines. When processing metals, large amounts of processing oil are used and circulated using a pump.

[0003] Water-soluble processing fluids used in metalworking are generally produced by appropriately mixing mineral oils, greases, fatty acids, fatty acid esters, extreme-pressure additives, surfactants, antifoaming agents, metal corrosion inhibitors, antioxidants, antiseptic and antifungal agents, etc., depending on the purpose, and then diluted with water to form what is known as coolant. Coolants are required to have primary performance related to machinability and grindability, and secondary performance related to workability, etc. Primary performance includes, for example, improved finished surface accuracy and extended tool life, while secondary performance includes, for example, excellent rust prevention, resistance to deterioration and easy management, non-toxicity to the human body, and low foaming.

[0004] Water-soluble processing oils contain many substances that serve as nutrient sources for microorganisms such as bacteria, yeast, and mold, as mentioned above, which makes the coolant prone to spoilage after dilution. As the spoilage of coolant progresses, both its primary and secondary performance declines, and the foul odor caused by spoilage also becomes a problem. Furthermore, if spoilage increases the frequency of oil changes, this becomes a cost disadvantage. Furthermore, if mold grows in the coolant, it can cause pipe blockages in the circulation system, such as pumps. To prevent this, preservatives and antifungal agents are added to processing oils, or other ingredients are used to treat them with preservatives and antifungal agents.

[0005] However, preservatives and antifungal agents generally suffer from the problem that their effectiveness decreases significantly over a short period of time due to decomposition or inactivation. Furthermore, widely known preservatives and antifungal agents include formaldehyde-releasing and phenolic types, but these are irritants. In other words, if they are added in large quantities to processing oils to achieve antifungal and antifungal properties, the processing oil itself can become highly irritating to the skin and have adverse effects on the human body.

[0006] Furthermore, some processing oils use amine soaps, which are surfactants (emulsifiers) made by reacting fatty acids with various amines (Patent Document 1). In this case, alkaline amines exist in a free state in the processing oil, and by incorporating a large amount of these free amines, it is possible to impart a certain degree of antiseptic and antifungal properties to the processing oil. There is also a technology for incorporating antibacterial amines into processing oils (Patent Document 2). Alternatively, a technology is known in which antiseptic properties are ensured by increasing the pH of the processing oil (alkaline, pH 9 or higher).

[0007] Known techniques that do not use preservatives or amines include methods for sterilizing oils or coolants from a physicochemical / equipment perspective, such as electromagnetic wave irradiation (Patent Documents 3 and 4), ultrasonic irradiation (Patent Document 5), sterilization using ozone (Patent Document 6), and sterilization using ultraviolet light (Patent Document 7). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Special Publication No. 61-40720 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-161585 [Patent Document 3] Japanese Patent Application Publication No. 2-212597 [Patent Document 4] Japanese Patent Application Publication No. 2-29496 [Patent Document 5] Japanese Patent Application Publication No. 63-245494 [Patent Document 6] Japanese Patent Application Laid-Open No. 2006-087563 [Patent Document 7] Japanese Patent Application Publication No. 4-264199 [Patent Document 8] Japanese Patent Application Laid-Open No. 2004-018444 Summary of the Invention [Problem to be solved by the invention]

[0009] However, for example, when a preservative effect is achieved by adding a free amine to a processing oil, a large amount of free amine is required to achieve a sufficient preservative effect. Therefore, a technology with a higher preservative effect is desired. Furthermore, when a preservative effect is achieved by adding an antibacterial amine, the antibacterial amine may be biotoxic, raising concerns about adverse effects on the global environment and the human body. Furthermore, when preservative effect is achieved by increasing the pH, there is a concern about the occurrence of significant skin damage to the human body, and in addition, there is a concern about metal corrosion when processing non-ferrous metals.

[0010] Furthermore, methods using electromagnetic waves or ultrasonic waves may alter the oil components in the coolant or destroy the emulsion. Furthermore, with ozone-based methods, the ozone generated has a strong oxidizing power that destroys the coolant components, potentially reducing its functionality as a metalworking oil. In addition, the ozone is highly corrosive and toxic, which can worsen the working environment. Therefore, measures such as measures to prevent corrosion of equipment and the installation and management of abatement equipment in accordance with working environment standards are required.

[0011] On the other hand, sterilization by ultraviolet irradiation kills microorganisms by damaging their DNA, so it is effective against all bacterial species, does not destroy coolant components, does not create resistant bacteria, and is a sterilization method with many advantages. However, ultraviolet light has a short peak wavelength of 400 nm or less and is poorly transparent, so as shown in Patent Document 7, it was necessary to provide a shallow section in the coolant circulation path so that ultraviolet light could be sufficiently irradiated. In addition, it is essential to take measures such as providing equipment and protective gear to limit worker exposure during irradiation. As mentioned above, UV sterilization is a sterilization method that takes advantage of the damage that UV rays cause to the DNA of living organisms. However, most living organisms have several mechanisms for repairing DNA damage caused by UV rays. One of these mechanisms is called "photoreactivation," in which microorganisms inactivated by UV irradiation, when exposed to light in the near-ultraviolet to visible range, repair their DNA and reactivate it through the action of their own photoreactivating enzymes. This mechanism is explained in "Photoreactivation of UV-Induced DNA Damage," Yamamoto, Biophysics, Vol. 25 No. 3 (1985). Thus, UV sterilization is not suitable for permanently sterilizing fluids circulating within equipment.

[0012] Furthermore, the above-mentioned various sterilization methods require the introduction of large-scale equipment such as an electromagnetic wave generator, an ozone generator, and an ultraviolet light generator, which results in high equipment and operating costs, and it is difficult to say that the antiseptic effect obtained is worth the cost.

[0013] Here, we will explain the "singlet oxygen generating photosterilization method," which has been largely ignored in the field of conventional metalworking fluids, as a physicochemical sterilization method. This sterilization method uses photosensitizers. The triplet state of photosensitizers has excitation energy roughly equal to the energy difference between singlet oxygen and triplet oxygen. Therefore, photosensitizers are excited by visible light and transition to the excited triplet state through intersystem crossing. When this state of photosensitizers collides with triplet oxygen, electrons and energy are exchanged, causing the photosensitizer to return to its ground state while simultaneously transitioning from triplet oxygen to singlet oxygen. This mechanism utilizes the generation of singlet oxygen by light irradiation, and its strong oxidizing properties are utilized for sterilization. This method, known as photodynamic therapy (PDT), was discovered in the early twentieth century and is still widely used in the medical and hygienic fields. Because this sterilization method uses photosensitizers, it can be induced by visible light irradiation. Unlike UV-based sterilization methods, this method avoids the risk of worker exposure. Furthermore, because the photosensitizer is added to metalworking fluids and then irradiated with visible light, it can address the challenges of physicochemical and equipment-based sterilization methods, as described above.

[0014] There are various known compounds that have photosensitizing properties, including synthetic dyes such as rose bengal and methylene blue, and riboflavin compounds, which are biological components that are harmless to the human body. Patent Document 8 discloses a method for sterilizing blood for transfusion, in which a riboflavin compound, a biological component harmless to the human body, is used as a photosensitizer and is irradiated with visible light. However, when a riboflavin compound is added to a conventional metalworking fluid, various problems associated with component oxidation, such as a decrease in pH, which can cause rust, occur, making it difficult to achieve practical sterilizing properties.

[0015] Therefore, the objective of the present disclosure is to provide a water-soluble functional fluid that utilizes photosterilization, has antibacterial and antiseptic properties, can maintain its antibacterial properties for a long period of time, has reduced odor and skin irritation, is safe, and has excellent liquid stability. [Means for solving the problem]

[0016] As a result of extensive research aimed at solving the above problems, the present inventors have come to the following findings. The putrefaction resistance of conventional water-soluble functional fluids has depended on preservatives or large amounts of free amines with antibacterial properties, and no water-soluble functional fluids with practical putrefaction resistance have existed without these. Adding a photosensitizer and performing photosterilization is an effective method for sterilizing water-soluble functional fluids without relying on preservatives or amines and without incurring significant costs for installing and maintaining new machinery. Therefore, when we tried adding a riboflavin compound as a photosensitizer, no separation, precipitation, or photoinactivation occurred, and the bactericidal power was maintained, but we found that there was a problem of a significant drop in pH, which can cause rust and other problems in water-soluble functional fluids.

[0017] The present invention has been made based on the above findings and is as follows.

[0018] <1> An aqueous functional fluid comprising a neutral photosensitizer having an isoalloxazine skeleton and an antioxidant, wherein the antioxidant is a radical scavenger or a peroxide decomposer.

[0019] <2> It is used as a water-soluble cutting oil, water-soluble grinding oil, water-soluble cleaning agent, water-soluble press oil, water-soluble forging oil, water-soluble rolling oil, water-soluble mold release agent, water-soluble cutting oil, water-soluble polishing oil or water-soluble hydraulic oil. <1> The water-soluble functional fluid according to claim 1.

[0020] <3> <1> or <2> 1. A stock solution of the water-soluble functional fluid according to claim 1, which contains a neutral photosensitizer having an isoalloxazine skeleton and an antioxidant, and the antioxidant is a radical scavenger or a peroxide decomposer.

[0021] <4> It is used as a stock solution for water-soluble cutting oil, water-soluble grinding oil, water-soluble cleaning agent, water-soluble press oil, water-soluble forging oil, water-soluble rolling oil, water-soluble mold release agent, water-soluble cutting oil, water-soluble polishing oil or water-soluble hydraulic oil. <3> A concentrate of the water-soluble functional fluid described in 1.

[0022] <5> <1> or <2> a sterilization device for sterilizing the water-soluble functional fluid described in the above, the sterilization device comprising at least a storage section for storing the water-soluble functional fluid, a light irradiation section for irradiating the water-soluble functional fluid with light, a metal working machine that performs metal processing while using the water-soluble functional fluid, and a circulation section for circulating the water-soluble functional fluid between the storage section and the metal working machine, and the water-soluble functional fluid that has been sterilized by the light irradiation section is supplied to the metal working machine by the circulation section.

[0023] <6> The light irradiating unit is installed in the storage unit. <5> A sterilization device for the water-soluble functional fluid described in 1.

[0024] <7> The light irradiating unit is installed outside the storage unit. <5> A sterilization device for the water-soluble functional fluid described in 1.

[0025] <8> <1> or <2> A method for sterilizing an aqueous functional fluid, comprising irradiating the aqueous functional fluid described in the above with visible light having a wavelength range of 380 nm or more and 500 nm or less. [Effects of the Invention]

[0026] According to the present disclosure, it is possible to provide a water-soluble functional fluid that utilizes light sterilization, which has antibacterial and antiseptic properties, can maintain its antibacterial properties for a long period of time, has reduced odor and skin irritation, is safe, and has excellent liquid stability. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a conceptual diagram illustrating the configuration of a sterilization device 1. [Figure 2] FIG. 1 is a schematic representation of an apparatus for testing photodisinfection. [Figure 3] FIG. 1 is a schematic diagram of an apparatus for testing photodisinfection and inhibition of pH decrease. DETAILED DESCRIPTION OF THE INVENTION

[0028] 1.Water-soluble functional fluid The aqueous functional fluid of the present disclosure is characterized by containing a neutral photosensitizer containing an isoalloxazine skeleton and an antioxidant.

[0029] 1.1. Neutral photosensitizers The neutral photosensitizer used in the present disclosure has an isoalloxazine skeleton represented by the following formula (1).

[0030] [ka]

[0031] R in formula (1) 1 ~R 5 is a hydrocarbon group having 1 to 3 carbon atoms, such as a methyl group. 1 ~R 5 may be the same or different. R in Equation (1) 6 is a hydrocarbon group having 1 to 10 H or C, and examples of the substituent in the hydrocarbon group include a hydroxyl group, an ester, and a phosphate ester. 6 may be derived from a sugar alcohol.

[0032] The triplet state of the molecules of the neutral photosensitizers in this disclosure is oxidized to singlet oxygen ( 1 O2) and triplet oxygen ( 3 The neutral photosensitizer has an excitation energy approximately equal to the energy difference with O2. Therefore, the neutral photosensitizer is excited by visible light and transitions to an excited triplet state by intersystem crossing. 3 Upon collision with O2, an electron and energy exchange occurs, and the neutral photosensitizer returns to the ground state. 3 O2 1 This is the mechanism by which singlet oxygen ( 1 Sterilization is carried out by the strong bactericidal properties of O2).

[0033] In the present disclosure, specific examples of the neutral photosensitizer include the following compounds:

[0034] [Lumichrome] (formula (2) below)

[0035] [ka]

[0036] [Riboflavin] (formula (3) below)

[0037] [ka]

[0038] [Riboflavin butyrate] (formula (4) below)

[0039] [ka]

[0040] [Riboflavin phosphate sodium ester] (formula (5) below)

[0041] [ka]

[0042] In the aqueous functional fluid of the present disclosure, the amount of the neutral photosensitizer added is preferably 20 ppm or more and 1000 ppm or less, based on 100 parts by weight of the entire aqueous functional fluid. Here, ppm represents a weight ratio. By setting the amount to 20 ppm or more, the photosterilization ability can be effectively exerted, and by setting the amount to 1000 ppm or less, the photosterilization ability can be sufficient while preventing equipment contamination, which is preferable from an economical standpoint.

[0043] 1.2.Antioxidants The aqueous functional fluid of the present disclosure contains an antioxidant to prevent a decrease in pH. This is because neutral photosensitizers with an isoalloxazine skeleton undergo photosensitization reactions in which, as described above, the photoexcited neutral photosensitizer reacts with oxygen molecules to generate singlet oxygen. Furthermore, the photoexcited neutral photosensitizer also undergoes a homolytic hydrogen abstraction reaction from the oil components, generating radicals that react with oxygen to generate peroxide radicals and peroxides. Furthermore, peroxides produce hydroxyl radicals, a powerful oxidizing agent, which oxidize the oil components. This chain reaction oxidizes the oil components, producing acidic compounds such as carboxylic acids, which lower the pH. A decrease in pH in water-soluble functional fluids must be prevented because it can cause metal corrosion in processing equipment and workpieces.

[0044] The antioxidant to be added includes a radical scavenger and a peroxide decomposer. Examples of phenol-based radical scavengers include D-α-tocopherol, butylated hydroxytoluene (BHT), Irganox 1010 (BASF Japan, registered trademark), Irganox 1076 (BASF Japan, registered trademark), Irganox 1330 (BASF Japan, registered trademark), Irganox 3114 (BASF Japan, registered trademark), Irganox 3125 (Ciba Specialty Chemicals, registered trademark), Irganox 3790 (Ciba Specialty Chemicals, registered trademark), Cyanox 1790 (Cyanamid, registered trademark), and Sumilizer GA-80 (Sumitomo Chemical, registered trademark), and examples of ascorbic acid-based radical scavengers include sodium alcorbate.

[0045] Examples of phosphorus-based peroxide decomposers include tris(1,1,1,3,3,3-hexafluoro-2-propyl) phosphite, triphenyl phosphite, triisodecyl phosphite, tributyl phosphite, tris(2,4-di-tert-butylphenyl) phosphite, tris(2-methylphenyl) phosphite, tris(4-methylphenyl) phosphite, tris(2-ethylhexyl) phosphite, and pentaerythritol bis(2,4-di-tert-butylphenyl phosphite). Examples of sulfur-based peroxide decomposers include 2-mercaptobenzimidazole, and examples of organic sulfur compounds include commercially available products such as DSTP (Yoshitomi) (Yoshitomi Co., Ltd., registered trademark), DLTP (Yoshitomi) (Yoshitomi Co., Ltd., registered trademark), DLTOIB (Yoshitomi Co., Ltd., registered trademark), DMTP (Yoshitomi) (Yoshitomi Co., Ltd., registered trademark), Seenox 412S (Shipro Chemical Co., Ltd., registered trademark), and Cyanox 1212 (Cyanamid Co., Ltd., trademark). The peroxide decomposer may be an amine-based agent such as monoethanolamine, monoisopropanolamine, diethanolamine, diisopropanolamine, triethanolamine, triisopropanolamine, 1,3-B-bis(aminomethyl)cyclohexane, and N,N'-di-sec-butyl-1,4-phenylenediamine, disodium edetate, Irgastab FS042 (Ciba Specialty Chemicals, registered trademark), GENOX EP (Crompton, registered trademark, chemical name: dialkyl-N-methylamine oxide), or a hindered amine-based agent such as ADK STAB manufactured by Asahi Denka. Examples of such surfactants include LA-52, LA-57, LA-62, LA-63, LA-67, LA-68, LA-77, LA-82, LA-87, and LA-94; Tinuvin 123, 144, 440, and 662 manufactured by CSC; Chimassorb 2020, 119, and 944 manufactured by Hoechst; Hostavin N30 manufactured by Cytec; Cyasorb UV-3346 and UV-3526 manufactured by Cytec; Uval 299 manufactured by GLC; and Sanduvor PR-31 manufactured by Clariant.

[0046] The amount of antioxidant added is preferably 0.0001 part by weight or more and 0.03 part by weight or less, when the total amount of the water-soluble functional fluid is 100 parts by weight.

[0047] 1.3.Other [Rust inhibitor] The water-soluble functional fluid of the present disclosure may also contain a rust inhibitor contained in conventional water-soluble functional fluids, such as alkanolamines, potassium hydroxide, sodium hydroxide, carboxylates, phosphates, polyphosphates, tungstates, molybdates, and sulfonates.

[0048] [Emulsified body] The water-soluble functional fluids of the present disclosure may include mineral oil or esters, or both, as emulsifiable materials. Examples of mineral oils include paraffinic mineral oils or naphthenic mineral oils obtained by refining lubricating oil fractions obtained by atmospheric distillation and vacuum distillation of crude oil through an appropriate combination of refining processes such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, and clay treatment. Examples of the ester include condensates of alcohols and carboxylic acids such as 2-ethylhexanol, trimethylolpropane, pentaerythritol, neopentyl glycol erythritol, glycerin, and sorbitol.

[0049] The content of the emulsified material is not particularly limited, but is preferably 0.25 to 6.0 parts by weight, based on 100 parts by weight of the entire functional fluid. By adding an amount of 0.25 parts by weight or more, lubricity can be ensured, and by adding an amount of 6.0 parts by weight or less, poor emulsion stability can be prevented while sufficient lubricity is maintained, making it economically preferable.

[0050] [Surfactants] The emulsion-based water-soluble functional fluid preferably further contains a surfactant, which can be selected from anionic, nonionic, and other surfactants that have been conventionally used in water-soluble metalworking fluids. Examples of anionic surfactants include fatty acid amine salts and fatty acid metal salts (potassium, sodium, etc.). Examples of nonionic surfactants include polyoxyalkylene alkyl ethers such as polyoxyethylene alkyl ethers and polyoxyethylene polyoxypropylene alkyl ethers, polyethylene glycol polypropylene glycol block polymers, coconut oil fatty acid diethanolamide, oleic acid diethanolamide, and fatty acid monoesters or diesters of polyalkylene glycols.

[0051] The content of the surfactant is not particularly limited, but is preferably 0.5 to 3.5 parts by weight, based on 100 parts by weight of the entire functional fluid. By adding an amount of 0.5 parts by weight or more, a good emulsion can be formed, and by adding an amount of 3.5 parts by weight or less, problems caused by foaming can be prevented, making it economically preferable.

[0052] 2. Applications of water-soluble functional fluids The water-soluble functional fluid of the present disclosure can be used as a water-soluble cutting oil, a water-soluble grinding oil, a water-soluble cleaning agent, a water-soluble press oil, a water-soluble forging oil, a water-soluble rolling oil, a water-soluble cutting oil, a water-soluble polishing oil or a water-soluble hydraulic oil, or a water-soluble mold release agent.

[0053] 3. Water-soluble functional fluid concentrate The concentrate of the water-soluble functional fluid of the present disclosure contains each of the components contained in the water-soluble functional fluid described above at a concentration of 5 to 100 times. The water-soluble functional fluids described above are distributed as concentrated stock solutions for ease of transport, handling, etc. Therefore, users who purchase the concentrated products dilute the stock solutions with water at a ratio of 5 to 100 times so that the concentration of the basic photosensitizer is 5 ppm or more, and then use the diluted solutions as water-soluble functional fluids. From the viewpoint of lubricity (concentration of the emulsified material) at the processing point, the concentration is preferably 5 to 50 times, more preferably 10 to 30 times, and most preferably 20 times. The aqueous functional fluid concentrate may contain a neutral photosensitizer containing an isoalloxazine skeleton in the range of 100 ppm to 10,000 ppm, and an antioxidant in the range of 0.1 parts by weight to 5 parts by weight, based on 100 parts by weight of the entire concentrate.

[0054] Furthermore, the aqueous functional fluid concentrate may contain, based on the total volume of the concentrate, the emulsified substance in a range of 50 parts by weight to 80 parts by weight, and the surfactant in a range of 10 parts by weight to 70 parts by weight.

[0055] 4. Sterilization equipment for water-soluble functional fluids As shown in Figure 1, the sterilization device 1 for water-soluble functional fluids of the present disclosure includes at least a storage unit (tank) 10 for storing the water-soluble functional fluid; a metalworking machine 20 installed at one or more locations and performing metalworking using the water-soluble functional fluid; a circulation unit 30, which is a pipe that supplies the water-soluble functional fluid to the metalworking machine, recovers the water-soluble functional fluid used there, and returns it to the storage unit; and a light irradiation unit 40, which is a light irradiation device that irradiates the water-soluble functional fluid with light from an LED light source to photosterilize the water-soluble functional fluid. The water-soluble functional fluid sterilized by the light irradiation unit is circulated between the storage unit and the metalworking machine by the circulation unit and supplied to the metalworking machine. The device may also include a filter for removing chips and other debris generated during processing from the recovered water-soluble functional fluid. The water-soluble functional fluid stored in the storage unit (tank) 10 is circulated between the storage unit (tank) 10 and the metalworking machine 20 by the pump 31 (circulation unit 30), and is irradiated with visible light by the light irradiation unit 40 to sterilize microorganisms such as bacteria, yeast, and mold that may have developed during storage, circulation, or use in the metalworking machine. As a result, the water-soluble functional fluid stored in the storage unit 10 has a low bacterial count.

[0056] As long as it has at least the above configuration, the sterilization device 1 of the present disclosure can be modified as appropriate to suit the scale, shape, etc. of the facility. For example, the light irradiation unit 40 may be provided in the storage unit 10 that stores the water-soluble functional fluid, or it may be provided outside the storage unit, such as in the piping that is the circulation unit 30, or in a purification device installed in part of the piping. Furthermore, since this sterilization device 1 is installed for the purpose of sterilizing the water-soluble functional fluid used in metal machine tools 20, it is preferable that its configuration conform to "JIS B 6016-2 Machine Tools - Lubrication Systems."

[0057] 5. Sterilization method for water-soluble functional fluids The water-soluble functional fluid of the present disclosure can be sterilized by irradiating it with light in the visible region in the light irradiating section. Specifically, a method of irradiating light using an LED as a light source is exemplified, and an LED with a dominant wavelength (strongest wavelength) in the range of 380 nm to 500 nm is preferred.

[0058] Alternatively, discharge lamps such as metal halide lamps, high-pressure mercury lamps, xenon lamps, halogen lamps, and pulsed xenon lamps may be used. Furthermore, the light from these lamps may be adjusted to have the above-mentioned preferred wavelengths by passing through an optical filter.

[0059] The irradiation method is not particularly limited. For example, the illuminance is 1 μW / cm 2 More than 1500μW / cm 2 The following light can be irradiated: 100 μW / cm 2 An illumination intensity of 1200 μW / cm or more is preferable. 2 The cumulative light intensity is 10J / cm 2 More than 500J / cm 2 The cumulative light dose can be set to 30 J / cm. 2 More than 400J / cm 2 Less than or equal to 100 J / cm 2 More than 400J / cm 2 The following is the result. [Example]

[0060] [Bactericidal activity of neutral photosensitizers containing isoalloxazine skeleton] A water-soluble functional fluid (Yushiron Former (registered trademark) ER53, manufactured by Yushiro Chemical Industry Co., Ltd.) collected from an actual facility was added to a normal bouillon medium (Eiken Chemical Co., Ltd., Eiken (registered trademark)) that had been adjusted to a predetermined concentration and sterilized in an autoclave. The mixture was shaken in a shaker at 30°C and 120 rpm for 24 hours, and the bacterial count reached 1.0 x 10 9 The inoculation solution was diluted with autoclaved physiological saline to obtain a bacterial count of 1.4 × 10 7 The test solution was prepared so as to have a concentration of CFU / ml.

[0061] The bacterial count was measured by serial dilution, and the number of colonies that appeared after static culture on a nutrient agar medium at 30°C for 4 hours was counted to calculate the bacterial count. A test solution for selecting photosensitizers was prepared by adding the neutral photosensitizers shown in Table 1 to the above test solution in the amounts shown in Table 1. The test solution was placed in a 100 mL container and stirred with a stirrer. As shown in Figure 2, 30 blue LEDs (OSB56A5111A, manufactured by OptoSupply, 5 mm bullet-shaped LED, wavelength 475 nm) were positioned at positions away from the liquid surface so as to achieve an arbitrary illuminance, and the number of bacteria after 30 minutes was confirmed according to the following criteria.

[0062] ++: Bacterial count 1.0×10 6 CFU / ml or more 1.4×10 7 CFU / ml or less + :Number of bacteria 1.0×10 2 CFU / ml or more 1.0×10 6 Less than CFU / ml - : Bacteria count 0 or more 1.0 x 10 2 Less than CFU / ml

[0063] [Table 1]

[0064] In Comparative Example 1, where no photosensitizer was added, no change in the number of bacteria due to light irradiation was observed. On the other hand, in Comparative Example 2, a decrease in the number of bacteria was observed when the integrated light dose was increased. This is thought to be due to the fact that the wavelength of the irradiated light was short and it was ultraviolet light in the UVC region, which has high bactericidal power, and therefore the bactericidal properties of the light itself were apparent. In contrast, in Example 1, the wavelength of the irradiated light was 500 nm, which is longer than that of the comparative example. Although this wavelength range does not allow for sterilization by light irradiation alone, a decrease in the number of bacteria was observed at high light intensities. Therefore, according to the present disclosure, sterilization can be achieved even with light irradiation at a wavelength in the visible light range that is less dangerous. Furthermore, since the irradiated wavelength does not need to be short as in Comparative Example 2, it is also possible to increase the light transmittance.

[0065] Furthermore, in all of Examples 2 to 7, a reduction in the number of bacteria was observed, and it was confirmed that in all of these examples, the sterilization effect exceeded that achieved by ultraviolet light as shown in Comparative Example 2.

[0066] [Suppression of pH decrease] Next, a test on the suppression of pH decrease by antioxidants will be explained. The stock solution of each example containing the components shown in Table 2 was diluted with water to a 5% dilution to prepare 2000 g of water-soluble cutting fluid. This was then placed in a 5 L water tank as shown in Figure 3, and the diluted solution was adjusted with hydrochloric acid to an initial pH of 8.6 ± 0.1, after which it was circulated using a pump. Furthermore, 200 g of casting chips were added to the water-soluble cutting fluid, which was then circulated using a pump. Simultaneously, a blue LED (TRI-450, manufactured by NDT Advance Co., Ltd.) was continuously irradiated from a position 30 cm above the liquid surface. To confirm bactericidal properties, a test inoculum (1.0 × 10 bacteria) was prepared by culturing the water-soluble functional fluid Yushiroken (registered trademark) FX1000 collected from an actual facility. 7 CFU / ml, mold 1.0 x 10 3 CFU / ml, yeast 1.0×10 3 CFU / ml) was added in 100 ml portions on the first and third days of the test. The number of bacteria was measured using a "Sunny Check BF" (manufactured by BioSun Laboratories).

[0067] Table 2 shows the ingredients of the concentrate for each example and the test results (evaluation). The pH was adjusted to 8.6±0.1 as described above. The pH values ​​after one month of continuous circulation using a pump and irradiation with blue LED light were shown. The difference in pH before and after the test was expressed as the pH change. Regarding photosterilization, the number of bacteria, mold, and yeast was measured one week after the start of the test using "Sunny Check BF" (manufactured by BioSun Laboratories) and evaluated according to the following criteria. ≪Bacteria≫ ○: Bacteria count 0 or more 1.0 × 10 5 Less than CFU / ml ×: Number of bacteria 1.0×10 5 CFU / ml or more ≪Mold, yeast≫ ○: Bacteria count 0 or more 1.0 × 10 2 Less than CFU / ml ×: Number of bacteria 1.0×10 2 CFU / ml or more

[0068] When the water-soluble cutting fluid prepared using the stock solution components of the example components of Example 11 was not irradiated with light, the bacterial count was 1.0 × 10 7 CFU / ml, the number of mold bacteria is 1.0 × 10 2 CFU / ml, yeast count 1.0 x 10 2 CFU / ml.

[0069] [Table 2]

[0070] Table 3 shows a summary based on the above results, focusing on antioxidants and suppression of pH decrease. The pH changes in Table 3 are the same as those in Table 2. The pH change rate was calculated using the following formula. pH change rate = 100% × (pH at time of preparation - pH after continued use) / (pH at time of preparation) Based on this pH change rate, those with a pH change rate of 15% or less were classified as A, those with a pH change rate of more than 15% but not more than 20% were classified as B, those with a pH change rate of more than 20% but not more than 30% were classified as C, and those with a pH change rate of more than 30% were classified as D. As can be seen from Table 3, the pH change rate for the sample containing no antioxidant was 31.4%.

[0071] [Table 3]

[0072] As can be seen from Table 2, all of the stock solutions in the examples contain riboflavin, a neutral photosensitizer containing an isoalloxazine skeleton, and therefore have excellent photosterilization properties. On the other hand, in Comparative Example 11, which does not contain an antioxidant, the pH dropped to 2.6 after one month of continuous use, and the pH fell below 6.0. As can be seen from Tables 2 and 3, among antioxidants, radical scavengers and peroxide decomposers are effective in suppressing the pH drop, but the singlet oxygen decomposer (sodium azide) was not effective. 1 It can be seen that the bactericidal properties of O2 are effective.

[0073] Furthermore, it can be seen that among radical scavengers and peroxide decomposers, phenol-based, secondary amine, tertiary amine, and phosphorus-based radical scavengers have the highest pH decrease suppression effect, followed by primary amines. [Explanation of symbols]

[0074] 1 Sterilizer 10 Reservoir 20 Metal machine tools 30 Circulation section 31 Pump 40 Light irradiation unit

Claims

1. A water-soluble functional fluid used as a water-soluble cutting oil, water-soluble grinding oil, water-soluble cleaning agent, water-soluble press oil, water-soluble forging oil, water-soluble rolling oil, water-soluble mold release agent, water-soluble cutting oil, water-soluble polishing oil, or water-soluble hydraulic oil, The composition contains a neutral photosensitizer having an isoalloxazine skeleton, an antioxidant, a rust inhibitor, and a surfactant, The antioxidant is a radical scavenger or a peroxide decomposer. Water-soluble functional fluid.

2. 2. A stock solution of the water-soluble functional fluid according to claim 1, which is used as a stock solution for water-soluble cutting oil, water-soluble grinding oil, water-soluble cleaning agent, water-soluble press oil, water-soluble forging oil, water-soluble rolling oil, water-soluble mold release agent, water-soluble cutting oil, water-soluble polishing oil or water-soluble hydraulic oil, The composition contains a neutral photosensitizer having an isoalloxazine skeleton, an antioxidant, a rust inhibitor, and a surfactant, The concentrate of the water-soluble functional fluid is characterized in that the antioxidant is a radical scavenger or a peroxide decomposer.

3. A sterilization device for sterilizing a water-soluble functional fluid, the sterilization device comprising a neutral photosensitizer having an isoalloxazine skeleton and an antioxidant, the antioxidant being a radical scavenger or a peroxide decomposer, a reservoir for storing at least the water-soluble functional fluid; a light irradiation unit that irradiates the water-soluble functional fluid with light; a metalworking machine that performs metalworking while using the water-soluble functional fluid; a circulation unit that circulates the water-soluble functional fluid between the storage unit and the metal working machine, The sterilization device for a water-soluble functional fluid supplies the water-soluble functional fluid sterilized by the light irradiation unit to the metalworking machine by the circulation unit.

4. 4. The sterilizing device for water-soluble functional fluids according to claim 3, wherein the light irradiating unit is installed inside the reservoir.

5. 4. The sterilizing device for water-soluble functional fluids according to claim 3, wherein the light irradiating unit is installed in the circulation unit.

6. A method for sterilizing an aqueous functional fluid, comprising irradiating the aqueous functional fluid according to claim 1 with visible light having a wavelength in the range of 380 nm to 500 nm.

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