JP7334108B2 - Water-soluble functional fluid, stock solution of water-soluble functional fluid, apparatus for sterilizing water-soluble functional fluid, and method for sterilizing water-soluble functional fluid - Google Patents

Description

TECHNICAL FIELD The present invention relates to a water-soluble functional fluid, an undiluted solution of the water-soluble functional fluid, an apparatus for sterilizing the water-soluble functional fluid, and a method for sterilizing the water-soluble functional fluid.

2. Description of the Related Art When performing metal working such as cutting, grinding, plastic working, etc., a working fluid is used to lubricate and cool between a working tool and a workpiece. There are oil-based processing fluids and water-soluble processing fluids, but water-soluble processing fluids are mainly used because they can cool efficiently and prevent fires during processing even in unmanned machines. It is During metal working, a large amount of working oil is used while being circulated by a pump.

Water-soluble processing oils used in metal processing generally include mineral oils, fats, fatty acids, fatty acid esters, extreme pressure additives, surfactants, antifoaming agents, anticorrosive agents for metals, antioxidants, preservatives and antifungal agents. It is produced by appropriately mixing them according to the purpose, diluted with water, and used as a so-called coolant. A coolant is required to have primary performance such as machinability and grindability, and secondary performance such as workability. Primary performance includes, for example, improved surface finish precision and extended tool life. It should be harmless and cause little foaming.

Since the water-soluble processing oil contains many substances that serve as nutrients for microorganisms such as bacteria, yeast, and molds as described above, there is a problem that the diluted coolant tends to spoil. As the decay of the coolant progresses, both primary performance and secondary performance deteriorate, and bad odors due to decay also become a problem. Moreover, if the frequency of oil replacement increases due to putrefaction, it is disadvantageous in terms of cost. Furthermore, if mold grows in the coolant, it may cause clogging of pipes in circulation systems such as pumps. In order to prevent this, an antiseptic/antifungal agent is added to the processing oil, or antiseptic/antifungal treatment is performed with other ingredients.

However, in general, preservatives and antifungal agents have the problem that their effects are remarkably reduced in a short period of time due to decomposition or inactivation. Also, widely known preservatives and fungicides include formaldehyde-releasing agents and phenolic agents, which are irritants. That is, when the processing oil is added in a large amount to the extent that antiseptic and antifungal performance can be exhibited, the processing oil itself becomes severely irritating to the skin, which may adversely affect the human body.

In addition, there is a processing oil that uses an amine soap obtained by reacting a fatty acid with various amines as a surfactant (emulsifier) (Patent Document 1). In this case, an alkaline amine is present in a free state in the processing oil, and by containing a large amount of the free amine, the processing oil can be imparted with a certain degree of antiseptic and antifungal properties. There is also a technique of incorporating an antibacterial amine in a processing oil (Patent Document 2). Alternatively, there is also known a technique of ensuring antiseptic properties by making the processing oil high pH (alkali of pH 9 or higher).

Techniques that do not use preservatives or amines include methods for sterilizing oils or coolants from the physico-chemical/apparatus aspects, such as irradiation with electromagnetic waves (Patent Documents 3 and 4), irradiation with ultrasonic waves (Patent Document 5), Sterilization by ozone (Patent Document 6), sterilization by ultraviolet rays (Patent Document 7), and the like are known.

Japanese Patent Publication No. 61-40720 JP 2009-161585 A JP-A-2-212597 JP-A-2-29496 JP-A-63-245494 JP 2006-087563 A JP-A-4-264199

However, for example, when adding a free amine to a processing oil to exhibit antiseptic effect, a large amount of free amine is required to exhibit a sufficient antiseptic effect. Therefore, a technique with a higher antiseptic effect has been demanded. Moreover, when an antiseptic effect is exhibited by adding an antibacterial amine, the antibacterial amine may have biotoxicity, and there is concern about adverse effects on the global environment and the human body. Furthermore, when antiseptic properties are secured by raising the pH, there is concern about the occurrence of significant skin damage to the human body, and in addition, when non-ferrous metals are processed, metal corrosion is also a concern.

Moreover, methods using electromagnetic waves or ultrasonic waves may alter the oil component in the coolant or destroy the emulsion.
In addition, in the ozone method, the generated ozone has a strong oxidizing power and destroys the coolant components, so there is a risk that the function as a metalworking fluid will decrease. Therefore, it is necessary to take measures such as measures against corrosion of equipment, installation and management of abatement equipment according to work environment standards, etc.

On the other hand, sterilization by ultraviolet irradiation kills bacteria by damaging the DNA of microorganisms, so it is effective against all types of bacteria, has no risk of destroying coolant components, does not create resistant bacteria, etc. It is a sterilization method with many advantages. However, since ultraviolet light has a short peak wavelength of 400 nm or less and poor transparency, it is necessary to provide a shallow portion in the circulation path of the coolant so that it can be sufficiently irradiated with ultraviolet light, as shown in Patent Document 7. was there. In addition, it is essential to take measures such as equipment and protective equipment to limit the exposure of workers during irradiation.
Moreover, as described above, ultraviolet sterilization is a sterilization method that utilizes damage to the DNA of living organisms by ultraviolet rays, but most organisms have some repair functions for DNA damage caused by ultraviolet rays. One of them is called "photoreactivation", and when microorganisms that have been inactivated by ultraviolet irradiation are exposed to light in the near-ultraviolet to visible range, their own photoreactivation enzyme works to repair and reactivate their DNA. This phenomenon is described in "Photorecovery of DNA Damage by Ultraviolet Rays", Yamamoto, Biophysics, Vol. 25 No. 3 (1985)", etc., introduces the mechanism. As described above, sterilization by ultraviolet light is not preferable for the purpose of permanently sterilizing the fluid circulating in the apparatus.

In addition, in the various sterilization methods described above, it is necessary to introduce large-scale equipment such as an electromagnetic wave generator, an ozone generator, and an ultraviolet generator. It is difficult to say that a commensurate antiseptic effect is obtained.

Here, as a physicochemical sterilization method, the "singlet oxygen generation photo sterilization method", which has hardly been considered in the conventional field of metalworking fluids, will be described.
This is a sterilization method that uses dyes (photosensitizers) such as rose bengal and methylene blue.
Since the triplet state of these dye molecules has an excitation energy almost equal to the energy difference between singlet oxygen and triplet oxygen, these dyes are photoexcited by visible light, and intersystem crossing results in an excited triplet state. When the dye in this state collides with triplet oxygen, electrons and energy are exchanged, and at the same time the dye returns to the ground state, the triplet oxygen transitions to singlet oxygen. In this method, singlet oxygen is generated by irradiation, and its strong oxidizing action is used for sterilization. This method was discovered as photodynamic therapy (PDT) at the beginning of the twentieth century and is still widely used in the medical and hygiene fields. According to this sterilization method, since a photosensitizer is used, it is possible to cause a reaction by irradiation with visible light, so unlike the sterilization method that uses ultraviolet irradiation, risks to workers due to exposure can be avoided. In addition, since it is a method of adding a photosensitizer to a metal working fluid and irradiating it with visible light, it is possible to solve the problems of the above-mentioned physicochemical/apparatus sterilization methods.

However, until now, even if the above dyes that can be photosterilized are added to ordinary metal working fluids, separation and precipitation occur, photobleaching occurs, and the photosensitizer cannot generate singlet oxygen. It has been difficult to obtain practical bactericidal properties due to problems such as loss of bactericidal properties.

Therefore, the present invention has antibacterial and antiseptic properties, can maintain antibacterial properties for a long period of time, reduces odor and skin irritation, further reduces separation, etc., and utilizes photosterilization with excellent liquid stability. An object of the present invention is to provide a water-soluble functional fluid.

As a result of intensive studies to solve the above problems, the present inventors have obtained the following knowledge.
The antiseptic properties of conventional water-soluble functional fluids depend on preservatives or amines, and there has been no water-soluble functional fluid with practical anti-septic properties that does not contain these agents. As a method for sterilizing a water-soluble functional fluid without relying on preservatives or amines and without incurring significant costs such as installation and management of new machines, a photosensitizer (pigment) is added and light is applied. A sterilization method is effective, and it is particularly effective to use a basic photosensitizer. However, when a basic photosensitizer is added to a conventional cutting oil, the fatty acid anion contained in the water-soluble functional fluid forms a complex with the basic photosensitizer, causing problems such as separation and precipitation. There is a problem that a fading reaction occurs and the photosensitizer loses ability to generate singlet oxygen.

The present invention has been made based on the above findings, and is as follows.
<1>
Based on the total amount of water-soluble functional fluid,
(a) 5 ppm by weight to 100 ppm by weight of a basic photosensitizer containing a diaminophenothiazinium skeleton or a diaminophenoxazinium skeleton represented by the following formula (1); (b) 0.05 of a dibasic acid salt; A water-soluble functional fluid characterized by containing up to 0.75 parts by weight.

（式（１）中、Ｙは、ＳまたはＯである。Ｒはそれぞれ同一であっても異なっていてもよく、水素原子、メチル基、エチル基のいずれかである。）
＜２＞
水溶性切削油、水溶性研削油、水溶性洗浄剤、水溶性プレス油、水溶性鍛造油、水溶性圧延油、水溶性離型剤、水溶性切断油、水溶性研磨油又は水溶性作動油として使用される、＜１＞に記載の水溶性機能流体。
＜３＞
＜１＞または＜２＞に記載の水溶性機能流体の原液であって、原液全量基準で、
（ａ）下記式（１）で示すジアミノフェノチアジニウム骨格あるいはジアミノフェノキサジニウム骨格を含む塩基性光増感剤を１００重量ｐｐｍ～２０００重量ｐｐｍ、（ｂ）二塩基酸塩を１～１５重量部含有することを特徴とする水溶性機能流体の原液。

(In Formula (1), Y is S or O. Each R may be the same or different and is a hydrogen atom, a methyl group, or an ethyl group.)
<2>
Water-soluble cutting oil, water-soluble grinding oil, water-soluble detergent, water-soluble press oil, water-soluble forging oil, water-soluble rolling oil, water-soluble release agent, water-soluble cutting oil, water-soluble polishing oil, or water-soluble hydraulic oil The water-soluble functional fluid according to <1>, which is used as
<3>
A stock solution of the water-soluble functional fluid according to <1> or <2>, which is based on the total amount of the stock solution,
(a) 100 ppm to 2000 ppm by weight of a basic photosensitizer containing a diaminophenothiazinium skeleton or diaminophenoxazinium skeleton represented by the following formula (1); (b) 1 to 15 ppm of a dibasic acid salt; A stock solution of a water-soluble functional fluid characterized by containing parts by weight.

（式（１）中、Ｙは、ＳまたはＯである。Ｒはそれぞれ同一であっても異なっていてもよく、水素原子、メチル基、エチル基のいずれかである。）
＜４＞
水溶性切削油、水溶性研削油、水溶性洗浄剤、水溶性プレス油、水溶性鍛造油、水溶性圧延油、水溶性離型剤、水溶性切断油、水溶性研磨油又は水溶性作動油の原液として使用される、＜３＞に記載の水溶性機能流体の原液。
＜５＞
＜１＞または＜２＞に記載の水溶性機能流体を殺菌する殺菌装置であって、
少なくとも前記水溶性機能流体を貯留する貯留部と、
前記水溶性機能流体に光を照射する光照射部と、
前記水溶性機能流体を使用しながら金属加工を行う金属工作機械と、
前記貯留部、および金属工作機械との間で前記水溶性機能流体を循環させる循環部と、を備え、
前記光照射部により殺菌された状態の水溶性機能流体を循環部により金属工作機械へ供給する、水溶性機能流体の殺菌装置。
＜６＞
前記光照射部が貯留部内に設置されていることを特徴とする＜５＞に記載の水溶性機能流体の殺菌装置。
＜７＞
前記光照射部が貯留部外に設置されていることを特徴とする＜５＞に記載の水溶性機能流体の殺菌装置。
＜８＞
＜１＞または＜２＞に記載の水溶性機能流体に波長範囲が６００～８００ｎｍの可視光を１００ｍＷ／ｃｍ^２以上の放射照度で照射することを特徴とする、水溶性機能流体の殺菌方法。

(In formula ( 1 ), Y is S or O. Each R may be the same or different and is a hydrogen atom, a methyl group, or an ethyl group.)
<4>
Water-soluble cutting oil, water-soluble grinding oil, water-soluble detergent, water-soluble press oil, water-soluble forging oil, water-soluble rolling oil, water-soluble release agent, water-soluble cutting oil, water-soluble polishing oil, or water-soluble hydraulic oil The stock solution of the water-soluble functional fluid according to <3>, which is used as the stock solution of
<5>
A sterilization device for sterilizing the water-soluble functional fluid according to <1> or <2>,
a storage part that stores at least the water-soluble functional fluid;
a light irradiation unit that irradiates the water-soluble functional fluid with light;
a metal machine tool that performs metal processing while using the water-soluble functional fluid;
a circulation unit that circulates the water-soluble functional fluid between the storage unit and the metal machine tool,
An apparatus for sterilizing water-soluble functional fluid, wherein the water-soluble functional fluid sterilized by the light irradiation unit is supplied to a metal machine tool by a circulation unit.
<6>
The apparatus for sterilizing water-soluble functional fluid according to <5>, wherein the light irradiation section is installed in a storage section.
<7>
The apparatus for sterilizing a water-soluble functional fluid according to <5>, wherein the light irradiation section is installed outside the storage section.
<8>
A method for sterilizing a water-soluble functional fluid, comprising irradiating the water-soluble functional fluid according to <1> or <2> with visible light having a wavelength range of 600 to 800 nm at an irradiance of 100 mW/cm ² or more.

According to the present invention, a water-soluble functional fluid that has antibacterial and antiseptic properties, can maintain antibacterial properties for a long period of time, reduces odor and skin irritation, reduces separation, etc., and has excellent liquid stability. can provide.

FIG. 2 is a diagram schematically showing an apparatus for conducting photo-sterilization experiments in Examples.

<Water-soluble functional fluid>
The water-soluble functional fluid of the present invention comprises (a) a basic fluid containing a diaminophenothiazinium skeleton or a diaminophenoxazinium skeleton represented by the following formula (1), when the total amount of the water-soluble functional fluid is 100 parts by weight. It is characterized by containing 5 ppm to 100 ppm of a photosensitizer and 0.05 to 0.75 parts by weight of (b) a dibasic salt.

(In Formula (1), Y is S or O. Each R may be the same or different and is a hydrogen atom, a methyl group, or an ethyl group.)

((a) basic photosensitizer)
The (a) basic photosensitizer used in the present invention has a diaminophenothiazinium skeleton or diaminophenoxazinium skeleton represented by the above formula (1).
The (a) basic photosensitizer has a counterion selected from the group consisting of Cl ⁻ , Br ⁻ , I ⁻ and SO ₄ ²⁻ . In addition, the diaminophenothiazinium skeleton or diaminophenoxazinium skeleton may further have a methyl group or a nitro group as a substituent, and may further have an aromatic ring condensed to a part of the aromatic ring. may

The (a) basic photosensitizer in the present invention generates singlet oxygen upon irradiation with light, which enables sterilization.
A dye (photosensitizer) such as methylene blue is used to generate singlet oxygen ( ¹ O ₂ ). The triplet states of these dye molecules have excitation energies approximately equal to the energy difference between ¹ O ₂ and triplet oxygen ( ³ O ₂ ). Therefore, these dyes are photoexcited by visible light, and they are transferred to an excited triplet state by intersystem crossing. When the dye in the excited triplet state collides with ³ O ₂ , electrons and energy are exchanged, and the dye returns to the ground state, and at the same time, ³ O ₂ transitions to ¹ O ₂ .

Specific examples of (a) the basic photosensitizer in the present invention include the following compounds.

(1) toronium chloride (toluidine blue)

(2) methylene blue

(3) Azure B

(4) Basic Green 5

(5) Basic Blue3

(6) Basic Blue 12

As noted above, the present invention employs a cationic basic photosensitizer. Since bacteria are generally negatively charged, the (a) basic photosensitizer of the present invention is cationic, so it exists in the vicinity of the bacteria, and the generated singlet oxygen effectively affects the bacteria. It is considered to work.

In the water-soluble functional fluid of the present invention, the amount of the basic photosensitizer (a) added is 5 ppm or more and 100 ppm or less when the entire water-soluble functional fluid is taken as 100 parts by weight. Here, ppm represents weight ratio. By making it 5 ppm or more, it is possible to effectively exhibit the photo-sterilizing ability, and by making it 100 ppm or less, it is possible to prevent facility contamination while maintaining sufficient photo-sterilizing ability, which is preferable in terms of economy.

((b) dibasic acid salt)
The water-soluble functional fluid of the present invention contains (b) a dibasic acid salt to provide antirust properties.
(b) Dibasic acid salts include, for example, sodium octenylsuccinate, sodium linoleic acid acrylic acid adduct, sodium dodecanedioate, potassium octenylsuccinate, potassium linoleic acid acrylic acid adduct, potassium dodecanedioate, lithium octenylsuccinate, Lithium linoleic acid acrylic acid adduct, lithium dodecanedioate, ricinoleic acid condensate, sebacic acid, undecanedioic acid, adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, citric acid, itaconic acid, maleated rosin, Acrylated rosin, maleopimaric acid and the like can be mentioned.

(b) The dibasic acid salt may be added as a salt, or a dibasic acid and an inorganic salt or an amine may be added. As for the amine, it is preferable to use an amine having no α-hydrogen as will be described later.
Amines having no α hydrogen include, for example, tert-butylamine, tert-amylamine, 2,3-dimethyl-2,3-butanediamine, tert-butylhydrazine, 1,1,3,3-tetramethylbutylamine, 2-amino-2-methyl-1-propanol, 2-amino-2-methyl-1,3-propanediol, tris(hydroxymethyl)aminomethane, 2-(dimethylamino)-2-methyl-1-propanol, 2-aminoisobutyric acid, 2-amino-2-ethyl-1,3-propanediol, 3,5-dimethyl-1-adamantanamine, 1-adamantanamine, adamantane-1,3-diamine, cumylamine, 2,2, 6,6-tetramethylpiperidine and the like can be mentioned.

Many conventional water-soluble functional fluids contain monobasic acids such as primary carboxylic acids and primary sulfonic acids as rust preventives. According to experiments conducted by the present inventors, when the cationic basic photosensitizer is added to the conventional water-soluble functional fluid, a complex is formed between the monobasic acid and the basic photosensitizer. , it was found that the water-soluble functional fluid separated over time and precipitated. However, we have found that no precipitation occurs when the above dibasic acid salt is added instead.

(b) The dibasic acid has two anions, and (b) one anion of the dibasic acid salt and (a) the basic photosensitizer form a complex, but due to reasons such as steric hindrance, The present inventors believe that the other anion of the dibasic salt does not form a complex, exists free, and can maintain the emulsion or solubility, thus preventing the occurrence of precipitation. thinking.

(b) The amount of the dibasic acid salt to be added is 0.05 to 0.75 parts by weight based on 100 parts by weight of the entire functional fluid. By setting the addition amount to 0.05 parts by weight or more, it is possible to ensure rust prevention, and by setting the addition amount to 0.75 parts by weight or less, it is possible to prevent equipment contamination while ensuring sufficient rust prevention, It can be preferable from the point of view of economy.

(amine with α hydrogen)
Conventional water-soluble functional fluids contain amines with alpha hydrogens. However, the present inventors found that when (b) a basic photosensitizer is added to the water-soluble functional fluid, the amine having α hydrogen acts as a reducing agent, and (b) the basic photosensitizer is reduced. It was found that a photobleaching reaction occurs. Therefore, in the present invention, the water-soluble functional fluid preferably does not contain an amine having α-hydrogen in order to prevent the photobleaching reaction.

Here, the expression "not containing an amine having an α-hydrogen" does not mean excluding an amine having an α-hydrogen as an unavoidable component contained as an impurity. Therefore, the water-soluble functional fluid of the present invention may contain an amine having an α-hydrogen to an extent that does not impair the effects of the present application. may contain.

Note that α-hydrogen derived from an aniline amino group does not correspond to the α-hydrogen described above. This is because, in an aniline compound, the aromatic ring delocalizes the lone pair of electrons on the nitrogen atom, so the lone pair of electrons cannot push out α-hydrogen as a hydride. Therefore, although the (a) basic photosensitizer has an amino group, since it is an aniline compound, it does not correspond to the above-mentioned "amine having an α-hydrogen".

(monobasic acid salt)
In addition, as described above, monobasic salts (primary sulfonates and primary carboxylates that are anionic surfactants) contained in conventional water-soluble functional fluids are (a) basic photosensitizers and It forms a complex and causes precipitation. Therefore, it is preferable that the water-soluble functional fluid of the present invention does not contain a monobasic acid salt. However, it is not intended to exclude the case where the monobasic acid salt is contained as an inevitable impurity, and the monobasic acid salt may be contained to the extent that the effect of the present application is not impaired. It may contain less than monobasic acid salt as an inevitable ingredient.

(Emulsified body)
The water-soluble functional fluids of the present invention may contain mineral oils or esters, or both, as emulsifiers. As the mineral oil, for example, the lubricating oil fraction obtained by atmospheric distillation and vacuum distillation of crude oil is subjected to solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, and sulfuric acid washing. , paraffinic mineral oil or naphthenic mineral oil refined by appropriately combining refining treatments such as clay treatment.

The content of the substance to be emulsified is not particularly limited, but is 0.25 to 4 parts by weight based on 100 parts by weight of the functional fluid as a whole. By setting the amount to 1 part by weight or more, it is possible to ensure lubricity, and by setting the amount to 3.5 parts by weight or less, sufficient lubricity can be obtained while preventing poor emulsification stability, resulting in economic efficiency. It can be preferable in terms of

(Surfactant)
The emulsion-based water-soluble functional fluid preferably further contains a surfactant. The surfactant can be arbitrarily selected from anionic and nonionic surfactants conventionally used in water-soluble metal working fluids.
The content of the surfactant is not particularly limited, but is 0.5 to 3.5 parts by weight based on 100 parts by weight of the entire functional fluid. When the amount is 0.75 parts by weight or more, a good emulsion can be formed, and when the amount is 2.5 parts by weight or less, problems due to foaming can be prevented, which is preferable in terms of economy. can be done.

(Use of water-soluble functional fluid)
The water-soluble functional fluid of the present invention includes water-soluble cutting oil, water-soluble grinding oil, water-soluble detergent, water-soluble press oil, water-soluble forging oil, water-soluble rolling oil, water-soluble cutting oil, water-soluble polishing oil, or water-soluble It can be used as a soluble hydraulic fluid and a water-soluble release agent.

<Undiluted solution of water-soluble functional fluid>
The undiluted solution of the water-soluble functional fluid of the present invention contains each component of the above-described water-soluble functional fluid at a concentration of 5 to 100 times.
The above-mentioned water-soluble functional fluid is distributed as a concentrate, which is a concentrated product, from the viewpoint of transportability, handleability, and the like. Therefore, a user who purchases the concentrated product dilutes the stock solution with water by 5 to 100 times so that the concentration of the basic photosensitizer is 5 ppm or more, and uses it as a water-soluble functional fluid.
From the viewpoint of lubricity (concentration of the material to be emulsified) at the point of processing, it is preferably 5-fold to 50-fold, more preferably 10-fold to 30-fold, and most preferably 20-fold.
The stock solution of the water-soluble functional fluid contains (a) 100 to 2000 ppm of the basic photosensitizer of formula (1) and (b) 1 to 15 parts by weight of the dibasic acid salt, based on 100 parts by weight of the whole stock solution. include.

Further, the stock solution of the water-soluble functional fluid may contain 50 to 80 parts by weight of the substance to be emulsified and 10 to 70 parts by weight of the surfactant, based on the total amount of the stock solution.

<Sterilization device for water-soluble functional fluid>
The apparatus for sterilizing a water-soluble functional fluid of the present invention comprises at least a reservoir (tank) for storing the water-soluble functional fluid, and a metal tank installed at one or a plurality of locations for performing metal processing while using the water-soluble functional fluid. a machine tool, a circulation section that is a pipe that supplies the water-soluble functional fluid to a metal machine tool, collects the water-soluble functional fluid used there, and returns it to the reservoir again; and a light irradiation unit which is a light irradiation device for irradiating and photosterilizing the water-soluble functional fluid. The water-soluble functional fluid sterilized by the light irradiation section is circulated between the storage section and the metal machine tool by the circulation section and supplied to the metal machine tool. Furthermore, a filter may be provided for removing chips and the like generated during processing contained in the recovered water-soluble functional fluid.
The water-soluble functional fluid stored in the reservoir (tank) is circulated (circulation part) between the reservoir (tank) and the metal machine tool by a pump, and is irradiated with light in the visible region at the light irradiation part. Microorganisms such as bacteria, yeast, and mold generated during storage, circulation, or use in metal machine tools are sterilized. As a result, the water-soluble functional fluid with a small number of bacteria is stored in the reservoir.
As long as it has at least the above configuration, the sterilization apparatus of the present invention can be appropriately modified according to the scale, form, etc. of the facility. For example, the light irradiator may be provided inside the reservoir that stores the water-soluble functional fluid, or it may be provided outside the reservoir, such as inside the pipe that is the circulation part or inside a purifying device installed in a part of the pipe. In addition, since this sterilization device is installed for the purpose of sterilizing the water-soluble functional fluid used in metal machine tools, its configuration conforms to "JIS B 6016-2 Machine tools - lubrication system". preferably.

<Method for sterilizing water-soluble functional fluid>
The water-soluble functional fluid of the present invention can be sterilized by irradiating light in the visible region in the light irradiation section.
Specifically, there is a method of irradiating light using an LED as a light source, and as a light source, an LED with a peak of 450 nm, an LED with a peak of 500 nm, an LED with a peak of 530 nm, an LED with a peak of 550 nm, and an LED with a peak of 600 nm. An LED with a peak of 620 nm, an LED with a peak of 645 nm, an LED with a peak of 660 nm, an LED with a peak of 700 nm, etc., but an LED with a dominant wavelength of 600 nm to 800 nm is preferable. .

Discharge lamps such as metal halide lamps, high-pressure mercury lamps, xenon lamps, halogen lamps, and pulse xenon lamps may also be used. Furthermore, these lights may be adjusted to light of the above preferred wavelengths by passing them through an optical filter.

The irradiation method is not particularly limited. For example, light with an illuminance of 1 to 1500 mW/cm ² can be irradiated. An illuminance of 100 mW/cm ² or more is preferable, and 1200 mW/cm ² or more may be used. Irradiation can be performed so that the integrated amount of light is 10 to 500 J/cm ² . The integrated amount of light is preferably 30 to 400 J/cm ² , more preferably 100 to 400 J/cm ² .

<Selection of photosensitizer effective for sterilization>
(Examples 1 to 6, Comparative Examples 1 to 12, Reference Examples 1 to 3)
As a bacterial solution for inoculum, a water-soluble functional fluid (Yushiron Former (registered trademark) ER53, manufactured by Yushiro Chemical Industry Co., Ltd.) that has been putrefied and deteriorated at the actual facility was prepared to a predetermined concentration and then autoclaved to sterilize normal bouillon medium (fermentation medium). Eiken (registered trademark) manufactured by Kenkagaku Co., Ltd.) and cultured with a shaking incubator at 30°C and 120 rpm for 24 hours so that the number of bacteria is equivalent to 10 ⁹ CFU/ml. The inoculum solution was diluted with autoclave-sterilized physiological saline to prepare a viable cell count of 1.4×10 ⁷ CFU/ml to prepare a test solution.
The number of bacteria was measured by a serial dilution method, and was calculated by counting the number of colonies that appeared after static culture on a nutrient agar medium at 30°C for 4 hours.
To the above test solution, a basic photosensitizer shown in Table 1 was added in an amount shown in Table 1 to prepare a test solution for selecting a photosensitizer, and the test solution for selecting a photosensitizer As shown in FIG. 1, from a position 300 mm away, an incandescent lamp (eye lamp PRF 100 V, 5000 W, manufactured by Iwasaki Electric Co., Ltd.) was placed through a petri dish containing water with a width of 20 mm (used to block heat rays). After 30 minutes, the number of bacteria was confirmed according to the following criteria.

++: the number of bacteria is 1.0×10 ⁶ CFU/ml or more and 1.4×10 ⁷ CFU/ml or less,
+: bacteria count of 1.0×10 ² CFU/ml or more and less than 1.0×10 ⁶ CFU/ml,
-: Bacterial count 0 to less than 10 ² CFU/ml,

The structures of the photosensitizers used in the comparative examples are shown below for reference.
Comparative Example 1: Neutral Red

Comparative Example 2: Acridine Orange

Comparative Example 3: Brilliant Blue R

Comparative Example 4: Acid Green 9

Comparative Example 5: EosinY

Comparative Example 6: Rose bengal

Comparative Example 7: Rhodamine B

Comparative Example 8: Acid Red 52

Comparative Example 9: New Coxin

Comparative Example 10: Allura Red AC

Comparative Example 11: Fluorescein

Comparative Example 12: Tetraphenylporphyrin

In the blank to which no photosensitizer was added, no change in the number of bacteria was observed even after light irradiation.
In Examples 1 to 6 in which the basic photosensitizer of formula (1) (a) used in the present invention was added, a decrease in the number of bacteria was observed even at an addition amount of 5 ppm, and at an addition amount of 20 ppm and 100 ppm, the bacteria were was dead.
On the other hand, in Comparative Examples 1 to 12 using photosensitizers outside the range of formula (1), no decrease in the number of bacteria was observed, or a decrease was observed at an addition amount of 100 ppm. (Comparative Example 2).
Moreover, in Reference Example 1, in which triethanolamine, which is an amine having no bactericidal activity, was added, no bactericidal activity was observed even when the added amount was 1000 ppm. In Reference Example 2 using 1,2-benzisothiazol-3(2H)-one, which is a conventional antiseptic, the number of bacteria was only reduced at 100 ppm. In Reference Example 3, in which the concentration of triethanolamine was 1% by weight and the amount of methylene blue added was varied from 5 to 1000 ppm, triethanolamine, which is an amine having α-hydrogen, reduces methylene blue to leucomethylene blue. Because of the change, it did not show photobactericidal activity.

<Confirmation of illumination intensity>
(Examples 7-15, Comparative Examples 13-16)

Add 50 ppm of toluidine blue or methylene blue to the test solution prepared in paragraph [0053], irradiate this test solution with an LED light source whose irradiation intensity is changed, and measure the number of bacteria when the determined light intensity is reached. , confirmed by the criteria defined in paragraph [0054]. The types and amounts of added photosensitizers, light irradiation conditions, and results are shown in [Table 2] below.

As shown in Table 2, when the LED light is irradiated at an illuminance of 100 mW/cm ² or more, the number of bacteria is reduced even at a light intensity of about 30 J/cm ² , and when the light intensity exceeds 400 J/cm ² , the number of bacteria is observed. Decrease from 0 to less than 10. It was also found that this effect was obtained when methylene blue was added instead of toluidine blue.

Moreover, it can be seen that the number of bacteria is reduced by irradiation with a wavelength of 620 nm or more. Also, if the irradiance is 100 mW/cm ² or less, the number of bacteria does not decrease. Furthermore, at an irradiance of 1200 mW/ ^cm2 , the number of bacteria can be reduced even at a wavelength of 450 nm, but with irradiation at a wavelength of 880 nm, which exceeds the visible light range, no reduction in the number of bacteria is observed even with the same irradiance. .

<Evaluation of maintenance of photobactericidal property and maintenance of oil agent performance>
(Examples 16-23, Comparative Examples 17-27, Reference Examples 4-7)
As cutting fluids, cutting fluids, mold release agents, and hot forging oils containing the components shown in Table 3 were prepared, and the following experiments were carried out to evaluate the maintenance of the photosterilization property and the maintenance of the oil performance.

(rust resistance)
Cast iron chips were placed in a glass petri dish, and the water-soluble metal working fluid of each example or comparative example diluted with water to a concentration of 5% was poured into the petri dish until the chips were completely soaked. After that, the petri dish was left to stand for 10 minutes with the lid on, and then the petri dish was slanted with the lid on to allow the diluted solution to flow out. Next, the petri dish was placed on a horizontal table and left to stand in this state for 6 hours to confirm the presence or absence of rust.
In the evaluation of rust resistance, "○" indicates that no rust was observed, and "x" indicates that rust occurred.

(color fastness of pigment)
The appearance of the water-soluble metal working fluid of each example or comparative example diluted with water to a concentration of 5% was observed after being left in a laboratory for one week. A case where fading of the dye was recognized was evaluated as "x", and a case where the color was maintained was evaluated as "good".

(Maintenance of liquid stability)
The appearance of the water-soluble metal working fluid of each example or comparative example diluted with water to a concentration of 5% was observed after being left in a laboratory for one week. A case where floating oil was generated or a sediment was generated was evaluated as "×", and a case where it was not generated was evaluated as "○".
In addition, 100 ppm of methylene blue was also prepared for each example, left for one week in the same manner, and the appearance was observed. The evaluation criteria are also the same.

(Maintenance of photobactericidal activity)
The water-soluble metalworking fluid of each example or comparative example diluted with water to a concentration of 5% was left in the laboratory for one week, and the bacterial solution was added to obtain 1.4×10 ⁷ CFU/ml. adjusted to As the bacterial solution, the same one as used in the above "Selection of a photosensitizer effective in sterilizing viable bacteria" was used, and evaluation was performed by the same method as shown in FIG.
In addition, 100 ppm of methylene blue was also prepared for each example, left for one week in the same manner, and the appearance was observed. The evaluation criteria are also the same.

Examples 16 to 23 containing a dibasic acid, an inorganic alkali salt and/or 2-amino-2-methyl-1-propanol as antirust components had good antirust performance, and methylene blue was added. Even in such a case, there was no precipitation of components and no discoloration of methylene blue, and the photosterilization property was maintained.
On the other hand, Comparative Examples 17 to 17 in which diethanolamine, triethanolamine, and 2,2′-(cyclohexylimino)bisethanol were added as amine components without using an inorganic alkali salt and/or 2-amino-2-methyl-1-propanol. In No. 21, a photobleaching reaction occurred after the addition of methylene blue and the dye faded. As a result, methylene blue lost its photo-sterilization ability and could not sterilize even with light irradiation.

Further, when a tribasic acid salt is formed by citric acid, which is a trivalent carboxylic acid, and an inorganic sodium salt (Comparative Example 22), citric acid, 1-amino-2-propanol, and triethanolamine (Comparative Example 23), In Comparative Example 22 containing an inorganic sodium salt, there was no fading of methylene blue and the photosterilization ability could be maintained. In Comparative Example 23 containing 1-amino-2-propanol and triethanolamine, discoloration of methylene blue occurred similarly to Comparative Examples 17 to 21, and photobactericidal properties were not exhibited.
Furthermore, citric acid, which does not have a non-polar group, has a weak action as a protective film, so rust occurred in both Comparative Examples 22 and 23.

Comparative Examples 24 to 27, in which monobasic acid salt and 2-amino-2-methyl-1-propanol are used as antirust components, suppress the formation of rust and maintain the photosterilization ability without fading of methylene blue, but precipitation occurs. However, the stability of the liquid was inferior.

As Reference Example 4, when a solution consisting of 1-amino-2-propanol and water alone was treated in the same manner as in the above Examples and Comparative Examples, methylene blue discoloration occurred due to the action of 1-amino-2-propanol. Ta. Moreover, since it did not contain a monobasic acid salt or a dibasic acid salt as a rust-preventing component, it had no rust-preventing properties. In addition, it showed bactericidal activity during the light irradiation experiment.
Furthermore, Reference Examples 6 and 7 show examples in which mineral oil and ester are added as lubricating components. Regardless of the addition of these components, the evaluation of each item was good.

Claims (8)

Based on the total amount of water-soluble functional fluid,
(a) 5 ppm to 100 ppm by weight of a basic photosensitizer containing a diaminophenothiazinium skeleton or a diaminophenoxazinium skeleton represented by the following formula (1);
(b) contains 0.05 to 0.75 parts by weight of a dibasic acid salt;
(c) no or less than 0.1 parts by weight of amines with alpha hydrogens;
(d) containing no or less than 0.2 parts by weight of a monobasic salt;
Water-soluble functional fluid.

(In Formula (1), Y is S or O. Each R may be the same or different and is a hydrogen atom, a methyl group, or an ethyl group.) Water-soluble cutting oil, water-soluble grinding oil, water-soluble detergent, water-soluble press oil, water-soluble forging oil, water-soluble rolling oil, water-soluble release agent, water-soluble cutting oil, water-soluble polishing oil, or water-soluble hydraulic oil The water-soluble functional fluid according to claim 1, which is used as a 3. The stock solution of the water-soluble functional fluid according to claim 1 or 2, which is based on the total amount of the stock solution,
(a) 100 ppm to 2000 ppm by weight of a basic photosensitizer containing a diaminophenothiazinium skeleton or a diaminophenoxazinium skeleton represented by the following formula (1);
(b) containing 1 to 15 parts by weight of a dibasic acid salt;
(c) no or less than 0.5 parts by weight of amines with alpha hydrogens;
(d) containing no or less than 1.0 parts by weight of a monobasic salt;
Stock solution of water-soluble functional fluid.

(In formula ( 1 ), Y is S or O. Each R may be the same or different and is a hydrogen atom, a methyl group, or an ethyl group.) Water-soluble cutting oil, water-soluble grinding oil, water-soluble detergent, water-soluble press oil, water-soluble forging oil, water-soluble rolling oil, water-soluble release agent, water-soluble cutting oil, water-soluble polishing oil, or water-soluble hydraulic oil The stock solution of the water-soluble functional fluid according to claim 3, which is used as a stock solution of A sterilization device for sterilizing the water-soluble functional fluid according to claim 1 or 2,
a storage part that stores at least the water-soluble functional fluid;
a light irradiation unit that irradiates the water-soluble functional fluid with light;
a metal machine tool that performs metal processing while using the water-soluble functional fluid;
a circulation unit that circulates the water-soluble functional fluid between the storage unit and the metal machine tool,
An apparatus for sterilizing water-soluble functional fluid, wherein the water-soluble functional fluid sterilized by the light irradiation unit is supplied to a metal machine tool by a circulation unit. 6. The apparatus for sterilizing water-soluble functional fluid according to claim 5, wherein the light irradiation section is installed in a storage section. 6. The apparatus for sterilizing water-soluble functional fluid according to claim 5, wherein the light irradiation unit is installed in the circulation unit. A method for sterilizing a water-soluble functional fluid, comprising irradiating the water-soluble functional fluid according to claim 1 or 2 with visible light having a wavelength range of 600 to 800 nm at an irradiance of 100 mW/cm ² or more.