JP7003986B2 - Grinding fluid regeneration device and grinding fluid regeneration method - Google Patents

Description

The present invention relates to a grinding fluid regenerating device and a grinding fluid regeneration method.
This application claims priority based on Japanese Application No. 2017-057082 filed on March 23, 2017, and incorporates all the contents described in the Japanese application.

Grinding machines such as wire saws are widely used to cut objects to be processed such as metal bodies. Further, when cutting an object to be processed by this grinding machine, a dispersion liquid in which abrasive grains are dispersed in the grinding liquid is often used. This dispersion enhances the lubricity between the grinding machine and the object to be machined, suppresses the generation of frictional heat at the contact portion of the grinding machine, and suppresses damage, thermal deformation, etc. of the grinding machine.

On the other hand, since the grinding fluid after use contains grinding debris such as floating oil, lubricating oil, chips, friction powder, and microorganisms, the used grinding fluid cannot be reused as it is. Therefore, the grinding fluid after conventional use is disposed of as industrial waste after removing impurities until it meets the wastewater standard.

However, if the used grinding fluid is discarded, the burden on the environment is large and the disposal cost is also high. Therefore, it is now considered to remove the grinding debris from the used grinding fluid and reuse the grinding debris after removing the grinding debris. Further, as such a reuse method, a method of removing grinding debris by centrifugation and membrane separation has been proposed (see JP-A-2010-221337).

Japanese Unexamined Patent Publication No. 2010-221337

The grinding fluid regenerating device according to one aspect of the present invention is a used grinding fluid regenerating device containing grinding debris, and is a storage tank for storing the used grinding fluid and a used storage tank stored in the storage tank. A membrane separation module having a filtration film for separating the grinding debris from the grinding fluid is provided, and the average pore size of the filtration film is 1.0 μm or more and 10.0 μm or less.

The method for regenerating the grinding fluid according to one aspect of the present invention is a method for regenerating the used grinding fluid containing the grinding debris, and includes a membrane separation step for separating the grinding debris from the used grinding fluid by a filtration membrane. The average pore size of the filtration membrane is 1.0 μm or more and 10.0 μm or less.

It is a schematic diagram which shows the regeneration apparatus of the grinding fluid which concerns on one Embodiment of this invention. FIG. 3 is a flow chart showing a method of regenerating the grinding fluid using the grinding fluid regeneration device of FIG. 1. It is a schematic diagram which shows the regenerating apparatus of the grinding fluid which concerns on the form different from the regenerating apparatus of the grinding fluid of FIG. FIG. 3 is a flow chart showing a method of regenerating the grinding fluid using the grinding fluid regeneration device of FIG. 3.

[Problems to be solved by this disclosure]
The method for reusing the used grinding fluid described in the above publication is to first collect the abrasive grains by centrifuging the used grinding fluid containing the abrasive grains, the dispersion liquid, and the chips, and then recover the abrasive grains. Chips are separated by high-speed centrifugation of the used grinding fluid, and the grinding fluid is recovered by membrane separation of the used grinding fluid from which the chips have been separated.

However, this method of reusing the grinding fluid requires a three-step separation step in order to regenerate the grinding fluid, which is complicated and takes time and effort to regenerate the grinding fluid. Further, the method for reusing the grinding fluid is to perform membrane separation after centrifugation in two steps, and the pore size of the membrane used for this membrane separation is 0.01 μm or more and 1 μm or less. Therefore, according to this method of reusing the grinding fluid, the permeation flux of the grinding fluid becomes low, and the regeneration efficiency of the grinding fluid cannot be sufficiently improved.

The present invention has been made based on such circumstances, and an object of the present invention is to provide a grinding fluid regenerating device and a grinding fluid regeneration method capable of easily and efficiently regenerating used grinding fluid. ..
[Effect of this disclosure]

The grinding fluid regeneration device and the grinding fluid regeneration method of the present invention can easily and efficiently regenerate the used grinding fluid.

[Explanation of Embodiment of the present invention]
First, embodiments of the present invention will be listed and described.

The grinding fluid regenerating device according to one aspect of the present invention is a used grinding fluid regenerating device containing grinding debris, and is a storage tank for storing the used grinding fluid and a used storage tank stored in the storage tank. A membrane separation module having a filtration film for separating the grinding debris from the grinding fluid is provided, and the average pore size of the filtration film is 1.0 μm or more and 10.0 μm or less.

Since the average pore diameter of the filtration membrane provided in the membrane separation module is 1.0 μm or more and 10.0 μm or less in the grinding fluid regenerating device, it is possible to selectively and efficiently separate grinding debris from the used grinding fluid. can. Therefore, the grinding fluid regenerating device can easily and efficiently regenerate the used grinding fluid.

It is preferable to further provide a coagulant addition mechanism for adding a coagulant to the used grinding fluid stored in the storage tank. As described above, by further providing the coagulant addition mechanism for adding the coagulant to the used grinding fluid stored in the storage tank, the grinding debris can be agglomerated by the coagulant, and the filtration membrane of the grinding debris can be coagulated. Permeation can be suppressed more reliably. Therefore, the used grinding fluid can be regenerated more easily and reliably.

The main component of the filtration membrane is preferably polytetrafluoroethylene (PTFE). Since the main component of the filtration membrane is PTFE, the filtration membrane has a three-dimensional network structure, so that the grinding debris can be effectively separated, and the holes are not easily closed by the grinding debris. Further, since the filtration membrane has a three-dimensional network structure, even if the filtration membrane is slightly worn, the separation function of the grinding debris is unlikely to deteriorate. Furthermore, since the main component of the filtration membrane is PTFE, the resistance to sodium hydroxide and the like is increased as compared with other organic membranes, so that a relatively inexpensive and highly durable filtration membrane can be formed.

Further, the method for regenerating the grinding fluid according to another aspect of the present invention is a method for regenerating the used grinding fluid containing grinding debris, and is a membrane separation method for separating the grinding debris from the used grinding fluid by a filtration membrane. The step is provided, and the average pore diameter of the filtration membrane is 1.0 μm or more and 10.0 μm or less.

In the method for regenerating the grinding fluid, since the average pore diameter of the filtration membrane used in the membrane separation step is 1.0 μm or more and 10.0 μm or less, it is possible to selectively and efficiently separate grinding debris from the used grinding fluid. can. Therefore, the method for regenerating the grinding fluid can easily and efficiently regenerate the used grinding fluid.

In the present invention, the "grinding waste" refers to impurities mixed in during the grinding process. The "average hole diameter" means the average value of the hole diameter when converted into a perfect circle with an equal area. The "main component" refers to a component having the highest content, for example, a component having a content of 50% by mass or more.

[Details of Embodiments of the present invention]
Hereinafter, the grinding fluid regenerating device and the grinding fluid recycling method according to each embodiment of the present invention will be described with reference to the drawings as appropriate.

[First Embodiment]
<Grinding liquid regeneration device>
The grinding fluid recycling device 1 (hereinafter, also simply referred to as “regenerating device 1”) of FIG. 1 is a recycling device for used grinding fluid X containing grinding debris. The regeneration device 1 has a storage tank (grinding liquid storage tank 2) for storing the used grinding liquid X and a membrane having a filtration film for separating grinding debris from the used grinding liquid X stored in the grinding liquid storage tank 2. It is provided with a separation module 3. In the regenerating device 1, the average pore diameter of the filtration membrane is 1.0 μm or more and 10.0 μm or less. Further, the regenerating device 1 uses a membrane separation module 3 to discharge the grinding scrap A discharged from the membrane separation module 3 and the used grinding fluid X discharged from the grinding fluid storage tank 2. Further includes a pump 5 for pumping to.

Since the average pore diameter of the filtration membrane provided in the membrane separation module 3 is 1.0 μm or more and 10.0 μm or less in the regenerator 1, it is possible to selectively and efficiently separate grinding debris from the used grinding fluid X. can. Further, in the regenerating device 1, the abrasive grains can be separated from the used grinding fluid X at the same time as the grinding chips. In the conventional regenerator, the abrasive grains and chips are first separated from the used grinding fluid by a centrifuge, and then the grinding fluid is permeated through a ceramic film having a pore size of 0.01 μm or more and 1 μm or less. It is being collected. On the other hand, according to the findings of the present inventors, the grinding debris and the abrasive grains are separated from the used grinding fluid X by a filtration membrane having an average pore diameter of 1.0 μm or more and 10.0 μm or less, thereby grinding with a centrifuge. Even if the grains and relatively large grinding debris are not separated in advance, the content of valuable components contained in the grinding fluid after membrane separation can be maintained at almost the same level as the grinding fluid before use. Therefore, the grinding fluid regenerating device can easily and efficiently regenerate the used grinding fluid.

(Grinding liquid)
The grinding fluid (grinding fluid before use) is used to improve the lubricity of the grinding machine and the object to be machined when cutting the object to be machined such as a metal body by a grinding machine such as a wire saw.
The type of the grinding fluid is not particularly limited, and is, for example, an emulsion-based oil containing mineral oil, animal and vegetable oil, a surfactant (anionic, cationic, nonionic) and the like in water and exhibiting a milky white appearance, and underwater. Contains surfactants, water-soluble components, mineral oils, animal and vegetable oils, etc., and contains oils such as solubles and kerosene that have a transparent or translucent appearance alone, or extreme pressure additives such as sulfur and chlorine in this oil. An oil-based system in which the above is mixed can be mentioned. Above all, an emulsion type is preferable as the grinding liquid to be regenerated by the regenerating device 1. When the used emulsion-based grinding fluid is treated, the regenerating device 1 can easily maintain the content ratio of the valuable component of the grinding fluid to the same level as before use. The content ratio of oil to 100 parts by mass of water in the emulsion-based grinding fluid can be, for example, 5 parts by mass or more and 15 parts by mass or less. This grinding fluid is usually used in a state where the abrasive grains are dispersed. The average particle size of the abrasive grains is generally about 10 μm or more and about 50 μm.

(Grinding liquid storage tank)
The grinding fluid storage tank 2 stores the used grinding fluid X. The used grinding fluid X is supplied to the contact portion between the grinding machine and the object to be processed during grinding, and is mixed with grinding debris such as floating oil, lubricating oil, chips, friction powder, and microorganisms. .. The grinding fluid storage tank 2 is configured so that, for example, the used grinding fluid X used at the time of grinding is stored through the discharge pipe 6 at any time.

(Membrane separation module)
The membrane separation module 3 is supplied with the used grinding fluid X stored in the grinding fluid storage tank 2 and pumped by the pump 5. In the present embodiment, the membrane separation module 3 is an external pressure type dead-end type membrane separation module having a filtration membrane. Specifically, the membrane separation module 3 has a plurality of hollow fiber membranes, and is configured to supply the used grinding fluid X to the outer peripheral surface side of these hollow fiber membranes. The membrane separation module 3 prevents the permeation of grinding debris and abrasive grains having a certain particle size or larger contained in the used grinding fluid X by increasing the pressure on the outer peripheral surface side of these hollow fiber membranes, and also contains a plurality of other components. Permeate inside the hollow fiber membrane of the book. The filtered liquid that has permeated inside the plurality of hollow fiber membranes is discharged to the outside of the system as the regenerated grinding liquid Y, and is reused during the grinding process. That is, it is preferable that the regenerating device 1 separates the grinding debris from the grinding fluid X only by the membrane separation module 3 and does not have other separation means such as a centrifuge.

As described above, the lower limit of the average pore size of the filtration membrane is 1.0 μm, more preferably 1.5 μm. On the other hand, the upper limit of the average pore size of the filtration membrane is 10.0 μm as described above, more preferably 5.0 μm, still more preferably 2.5 μm. If the average pore diameter is smaller than the above lower limit, the valuable components may not be sufficiently permeated into the filtration membrane, or the permeation flux of the filtrate may be low and the regeneration efficiency of the regenerated grinding fluid Y may be insufficient. There is. On the contrary, if the average pore diameter exceeds the upper limit, it may be difficult to sufficiently membrane-separate grinding debris such as mineral oil, animal and vegetable oil, and BOD (biochemical oxygen demand).

It is preferable that the pore diameters of the plurality of pores of the filtration membrane are uniform. The upper limit of the coefficient of variation of the pore diameters of the plurality of holes is preferably 0.20, more preferably 0.10, and even more preferably 0.05. If the coefficient of variation exceeds the upper limit, valuable components may be unintentionally removed or grinding debris having a relatively large particle size may be mixed into the regenerated grinding fluid Y, and the quality of the regenerated grinding fluid Y may be improved. It may be difficult to keep. On the other hand, the lower limit of the coefficient of variation of the hole diameters of the plurality of holes is not particularly limited and may be, for example, 0.01. The "coefficient of variation of the hole diameters of a plurality of holes" means a value obtained by dividing the standard deviation of the hole diameters of 10 arbitrarily extracted holes by the average diameter.

The material of the filtration membrane is not particularly limited, and for example, synthetic resin, ceramic, or the like can be used. Examples of the synthetic resin include polyethylene, polypropylene, polyvinylidene fluoride, ethylene-vinyl alcohol copolymer, polyamide, polyimide, polyetherimide, polystyrene, polysulfone, polyvinyl alcohol, polyphenylene ether, polyphenylene sulfide, cellulose acetate, and poly. Examples thereof include thermoplastic resins such as acrylonitrile and polyimide. Among them, as the main component of the filtration membrane, PTFE having excellent mechanical strength, chemical resistance, heat resistance, weather resistance, nonflammability and the like and being porous is preferable, and uniaxially or biaxially stretched PTFE is more preferable. preferable. Since the main component of the filtration membrane is PTFE, the filtration membrane has a three-dimensional network structure, so that the grinding debris can be effectively separated, and the holes are not easily closed by the grinding debris. Further, since the filtration membrane has a three-dimensional network structure, the separation function of grinding debris is unlikely to deteriorate even if the filtration membrane is slightly worn. Further, when the filtration membrane is formed of ceramic, the cost required for forming the filtration membrane is high, and the filtration membrane may be cracked. On the other hand, since the main component of the filtration membrane is PTFE, it is possible to form a relatively inexpensive and highly durable filtration membrane.
In addition, in the recycling apparatus 1, while the used grinding fluid X is being regenerated, grinding debris such as oil gradually adheres to the surface of the filtration membrane. These grinding debris can be easily removed by washing with a strong alkaline aqueous solution such as an aqueous solution of sodium hydroxide. In this regard, since the main component of the filtration membrane is PTFE, the resistance to sodium hydroxide and the like can be enhanced as compared with other organic membranes, and the life of the filtration membrane and the regeneration device 1 can be extended. Can be promoted.

When the filtration membrane is a hollow fiber membrane containing PTFE as a main component, the filtration membrane can be formed, for example, by using a tube obtained by extrusion-molding PTFE. By forming the filtration membrane using an extrusion-molded tube in this way, the mechanical strength of the filtration membrane can be easily improved and pores can be easily formed. It is preferable that this tube is stretched at a stretching ratio of about 50% or more and 700% or less in the axial direction and 5% or more and 100% or less in the circumferential direction. As the lower limit of the ratio of the elongation ratio in the axial direction to the elongation ratio in the circumferential direction of this tube, 2 is preferable, and 5 is more preferable. On the other hand, as the upper limit of the above ratio, 15 is preferable, and 10 is more preferable. By setting the ratio within the above range, the pores of the filtration membrane can be formed into an elongated shape having the axial direction of the hollow fiber membrane as a major axis, typically an ellipse. As described above, when the pores of the filtration membrane are elongated, it is easy to accurately prevent the permeation of grinding debris even if the average pore diameter of the filtration membrane is relatively large. Therefore, according to this configuration, it is easy to increase the permeation flux of the filtered liquid and sufficiently improve the production efficiency of the regenerated grinding liquid Y.

The tube can be obtained by blending, for example, PTFE fine powder with a liquid lubricant such as naphtha, forming a tube by extrusion molding or the like, and then stretching the tube. Further, dimensional stability can be improved by holding the tube in a heating furnace kept at a temperature equal to or higher than the melting point of PTFE fine powder, for example, about 350 to 550 ° C., for about several tens of seconds to several minutes and sintering it. ..

The lower limit of the porosity of the plurality of hollow fiber membranes is preferably 50%, more preferably 55%. On the other hand, the upper limit of the porosity of the plurality of hollow fiber membranes is preferably 90%, more preferably 85%. If the porosity does not reach the lower limit, the permeation flux of the filtrate may become low and the regeneration efficiency of the used grinding fluid X may become insufficient. On the contrary, if the porosity exceeds the upper limit, the mechanical strength of the plurality of hollow fiber membranes may be insufficient. The pore ratio refers to the ratio of the total volume of pores to the volume of the plurality of hollow fiber membranes, and is measured by measuring the density of the plurality of hollow fiber membranes in accordance with ASTM-D-792. Can be asked.

(Grinding waste discharge tank)
The grinding debris discharge tank 4 communicates with the space on the outer peripheral surface side of the plurality of hollow fiber membranes of the membrane separation module 3. Grinding debris that has not penetrated into the plurality of hollow fiber membranes of the membrane separation module 3 is discharged to the grinding debris discharge tank 4. Further, the abrasive grains contained in the used grinding fluid X are discharged to the grinding debris discharge tank 4. The grinding debris discharged to the grinding debris discharge tank 4 is disposed of as industrial waste at any time, for example.

<Regeneration method of grinding fluid>
Next, with reference to FIG. 2, a method for regenerating the grinding fluid using the regenerating device 1 of FIG. 1 (hereinafter, also simply referred to as “regenerating method”) will be described. The regeneration method is a method for regenerating the used grinding fluid X containing grinding debris. The regeneration method includes a membrane separation step (S1) for separating the grinding debris from the used grinding fluid X by a filtration membrane. In the regeneration method, the average pore diameter of the filtration membrane is 1.0 μm or more and 10.0 μm or less.

In this regeneration method, since the average pore diameter of the filtration membrane used in the membrane separation step is 1.0 μm or more and 10.0 μm or less, grinding debris can be selectively and efficiently separated from the used grinding fluid. Therefore, the method for regenerating the grinding fluid can easily and efficiently regenerate the used grinding fluid X.

(Membrane separation process)
S1 is performed by the membrane separation module 3 of FIG. Specifically, in S1, of the grinding fluid X stored in the grinding fluid storage tank 2 and pumped by the pump 5, grinding debris and abrasive grains having a certain particle size or larger are membrane-separated by the filtration film. In S1, the filtrate that has passed through the filtration membrane is discharged to the outside of the system as the regeneration grinding fluid Y. On the other hand, in S1, the grinding debris A that has not penetrated the filtration membrane is discharged to the grinding debris discharge tank 4.

The upper limit of the average permeation flux of the filtrate in S1 is preferably 7.0 m / D, preferably 5.0 m / D, from the viewpoint of sufficiently capturing the grinding debris contained in the used grinding fluid X by the filtration membrane. More preferred. On the other hand, as the lower limit of the average permeation flux, for example, 0.1 m / D is preferable, and 0.4 m / D is more preferable from the viewpoint of preventing the regeneration efficiency of the regenerated grinding fluid Y from becoming insufficient. The "average permeation flux" refers to the average value of the permeation flux when the grinding debris is separated from the used grinding fluid for 5 hours in a state where the grinding debris is not attached to the filtration membrane.

It should be noted that the regeneration method separates the grinding debris from the used grinding fluid X only by S1 and preferably does not have another separation step such as a centrifugation step. On the other hand, in the regeneration method, while the membrane separation treatment is continued by S1, grinding debris such as oil gradually adheres to the surface of the filtration membrane and the like. Therefore, the regeneration method may include a cleaning step of cleaning the filtration membrane when S1 is stopped. Hereinafter, this cleaning process will be described.

(Washing process)
The specific cleaning method in the cleaning step is not particularly limited as long as it can remove the grinding debris adhering to the filter membrane, but the cleaning step is a rubbing step of scrubbing the filter membrane. It is preferable to have an alkaline cleaning step of alkaline cleaning the filter membrane after the rubbing step. In the rubbing step, for example, the filtration membrane is scrubbed by hand. Further, in the alkaline cleaning step, for example, the filter membrane is alkaline-cleaned with a strong alkaline aqueous solution such as a sodium hydroxide aqueous solution. In the regeneration method, when the filtration membrane contains PTFE as a main component as described above, the filtration membrane can be easily washed. Further, since the main component of the filtration membrane is PTFE, deterioration of the filtration membrane can be suppressed even when alkaline washing is performed with a strong alkaline aqueous solution such as an aqueous sodium hydroxide solution, so that the filtration membrane and eventually the filtration membrane can be suppressed. It is possible to promote the extension of the life of the reproduction device 1.

[Second Embodiment]
<Grinding liquid regeneration device>
The grinding fluid recycling device 21 (hereinafter, also simply referred to as “regenerating device 21”) of FIG. 3 is a recycling device for used grinding fluid X containing grinding debris. The regeneration device 21 includes a grinding fluid storage tank 2 for storing the used grinding fluid X, and a membrane separation module 3 having a filtration membrane for separating grinding debris from the used grinding fluid X stored in the grinding fluid storage tank 2. To prepare for. Further, the regenerating device 21 uses the grinding fluid discharge tank 4 from which the grinding dust A membrane separated by the membrane separation module 3 is discharged and the used grinding fluid X discharged from the grinding fluid storage tank 2 into the membrane separation module 3. It is provided with a pump 5 for pumping to. Further, the regenerating device 21 includes a coagulant adding mechanism 22 for adding the coagulant B to the used grinding liquid X stored in the grinding fluid storage tank 2. In the regenerating device 21, the average pore diameter of the filtration membrane is 1.0 μm or more and 10.0 μm or less. Since the grinding fluid storage tank 2, the membrane separation module 3, the grinding scrap discharge tank 4, and the pump 5 in the recycling device 21 are the same as those of the recycling device 1 of FIG. 1, the same reference numerals are given and the description thereof will be omitted.

(Coagulant addition mechanism)
The coagulant addition mechanism 22 includes a supply pipe 22a for supplying the coagulant B to the grinding fluid storage tank 2 and a stirrer 22b for mixing the coagulant B supplied to the grinding fluid storage tank 2 with the used grinding fluid X. Has. The coagulant addition mechanism 22 flocs the grinding debris, typically the oil, contained in the used grinding fluid X. Specifically, the flocculant addition mechanism 22 flocks the grinding debris contained in the used grinding fluid X so that the particle size is larger than the pore size of the filtration membrane.

The coagulant B is not particularly limited as long as it can agglomerate the grinding debris contained in the used grinding fluid X, and examples thereof include known coagulants such as inorganic flocculants and polymer flocculants. Examples of the inorganic flocculant include aluminum salts such as aluminum sulfate and polyaluminum chloride, ferric chloride, ferrous sulfide, polyferric sulfate, and iron salts such as iron-silica inorganic polymer. Examples of the polymer flocculant include cationic polymers, anionic polymers and nonionic polymers. Examples of the cationic polymer include polydimethylaminoethyl (meth) acrylate, polydiethylaminoethyl (meth) acrylate, polydimethylaminopropyl (meth) acrylamide, polydimethylaminopropyl (meth) acrylamide, polyallyldimethylamine, and the like. Examples thereof include neutralized salts and quaternary salts. Examples of the anionic polymer include poly (meth) acrylic acid, polymaleic acid, polyitaconic acid and salts thereof. Examples of the nonionic polymer include poly (meth) acrylamide, poly N-isopropylacrylamide, poly N, N-dimethyl (meth) acrylamide and the like.

Since the regenerating device 21 includes the coagulant addition mechanism 22, the grinding debris can be agglomerated by the coagulant B, and the permeation of the grinding debris through the filtration membrane can be more reliably suppressed. Therefore, the regenerating device 21 can more easily and surely regenerate the used grinding fluid X.

<Regeneration method of grinding fluid>
Next, with reference to FIG. 4, a method of regenerating the grinding fluid using the regenerating device 21 of FIG. 3 will be described. The regeneration method is a method for regenerating the used grinding fluid X containing grinding debris. The regeneration method includes a film separation step (S1) in which the grinding debris is separated from the used grinding fluid X by a filtration membrane, and agglomeration in which the coagulant B is added to the used grinding fluid X stored in the grinding fluid storage tank 2. The agent addition step (S2) is provided. In the regeneration method, the average pore diameter of the filtration membrane is 1.0 μm or more and 10.0 μm or less. Since the membrane separation step (S1) in the regeneration method is the same as the regeneration method of FIG. 2, the description thereof will be omitted. It should be noted that the regeneration method separates the grinding debris from the used grinding fluid X only by S1 and preferably does not have another separation step such as a centrifugation step. Further, the regeneration method may include a cleaning step of cleaning the filtration membrane, similar to the regeneration method of FIG.

(Coagulant addition process)
S2 is performed by the flocculant addition mechanism 22. The timing of performing S2 is not particularly limited, and for example, S2 may be performed each time the used grinding fluid X is supplied to the grinding fluid storage tank 2. In this case, in the reproduction method, S1 is performed after S2.
On the other hand, as shown in FIG. 4, in the regeneration method, S1 is continuously or intermittently performed, the concentration of the grinding debris in the filtrate obtained by S1 and the grinding debris stored in the grinding fluid storage tank 2. S2 may be performed when the concentration or the like becomes equal to or higher than a predetermined value.

In the regeneration method, the grinding debris contained in the used grinding fluid X can be agglomerated by the coagulant addition step, so that the permeation of the grinding debris through the filtration membrane can be more reliably suppressed.
Therefore, the recycling method can more easily and reliably regenerate the used grinding fluid X. Further, in the regeneration method, for example, when the concentration of the grinding debris in the filtrate obtained by the membrane separation step, the concentration of the grinding debris stored in the grinding fluid storage tank 2, and the like become equal to or higher than a predetermined value, S2 is performed. Thereby, the quality of the regenerated grinding fluid Y can be kept more stable.

[Other embodiments]
It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is not limited to the configuration of the above embodiment, but is indicated by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims. To.

For example, the regenerating device does not necessarily have to use a dead-end type membrane separation module, and for example, a cross-flow type membrane separation module can also be used. Further, the filtration membrane does not necessarily have to be a hollow fiber membrane, and may be, for example, a flat membrane. Further, the regenerating device can generate the regenerated grinding fluid only by the membrane separation module, but as a grinding debris separation mechanism other than the membrane separation module, for example, the floating oil in the grinding fluid storage tank is removed. It may be provided with a mechanism for performing.

The regenerating device can be configured as, for example, a batch type regenerating device that stores a certain amount of used grinding fluid in a grinding fluid storage tank and repeatedly regenerates the entire amount of the grinding fluid. Further, the regenerating device may be configured as a continuous regenerating device that continuously or intermittently supplies the used grinding fluid to the grinding fluid storage tank and separates the grinding debris by the filtration membrane in parallel with the supply. It is possible.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

[No. 1]
By the method of regenerating the grinding fluid using the recycling apparatus 1 of FIG. 1, a recycled grinding fluid was generated from a used emulsion-based grinding fluid containing grinding debris. When the components of the grinding fluid were measured before use, they were 5800 ppm of mineral oil, 7100 ppm of animal and vegetable oil, and 15000 ppm of BOD.
Further, when the components of the grinding fluid after use were measured, it was found to be 40,000 ppm of mineral oil, 42,000 ppm of animal and vegetable oil, and 62,000 ppm of BOD. The membrane separation module 3 of the regenerating device 1 has three hollow fiber membranes, the total membrane area of these hollow fiber membranes is 1.05 m ² , and the average pore diameter of the plurality of hollow fiber membranes is 2. The one having a thickness of 0.0 μm was used.

The above-mentioned used grinding fluid 20L was stored in the grinding fluid storage tank 2, and the entire amount of the used grinding fluid was pumped to the membrane separation module 3 by the pump 5 to separate the grinding debris. The filtration pressure in the membrane separation module 3 was 30 kPa. The average permeation flux of the filtrate that permeated the plurality of hollow fiber membranes was 5.0 m / D. No. When the components of the regenerated grinding fluid Y obtained in No. 1 were measured by the normal hexane extraction method, they were 9600 ppm of mineral oil, 12000 ppm of animal and vegetable oil, and 21000 ppm of BOD.

[No. 2]
The regenerated grinding fluid was generated from the used grinding fluid containing the grinding debris by the method of regenerating the grinding fluid using the apparatus imitating the regeneration device 21 of FIG. No. 1 used grinding fluid. The same as 1 was used. Further, as the membrane separation module 3, No. The same as 1 was used.

Hydrochloric acid was used as a pH adjuster, and the pH of the above-mentioned used grinding fluid was adjusted to 6.8. Next, a total of 20 L of the used grinding fluid was transferred to a plurality of containers imitating the grinding fluid storage tank 2, and these containers were installed in a jar tester. Polyaluminum chloride was added to these containers as a flocculant at a concentration of 10 g / L. Subsequently, sodium hydroxide was used as a pH adjuster, and the pH of the used grinding fluid after the addition of the flocculant was adjusted to 6.8. Using the above-mentioned jar tester, the used grinding fluid after pH adjustment was stirred at a stirring speed of 150 rpm for 5 minutes, and further stirred at a stirring speed of 50 rpm for 10 minutes. Then, the entire amount of the used grinding fluid after stirring was pressure-fed to the membrane separation module 3 to separate grinding debris. The filtration pressure in the membrane separation module 3 was No. It was the same as 1. The average permeation flux of the filtrate that permeated the plurality of hollow fiber membranes was 2.0 m / D. No. When the components of the regenerated grinding fluid Y obtained in No. 2 were measured, they were 5600 ppm of mineral oil, 5100 ppm of animal and vegetable oil, and 14000 ppm of BOD.

[No. 3 and No. 4]
Except that the average pore diameters of the plurality of hollow fiber membranes are as shown in Table 1, No. The used grinding fluid was regenerated in the same manner as in 2.

[Evaluation results]
As shown in Table 1, the hollow fiber membrane has an average pore diameter of 2.0 μm, and the used grinding fluid is added with a flocculant. In No. 2, the mineral oil, animal and vegetable oil, and BOD are all about the same as the values before use, and the used grinding fluid can be regenerated with high accuracy. It is considered that this is because the grinding debris such as floating oil, lubricating oil, chips, friction powder, and microorganisms contained in the used grinding fluid could be removed with high accuracy. In addition, No. No. 2 in which no flocculant was added. Regarding No. 1, mineral oil, animal and vegetable oil, and BOD can all be suppressed to 0.34 times or less of the content after use, and grinding debris can be sufficiently separated from the used grinding fluid. ing. Further, No. 1 in which the average pore diameter of the hollow fiber membrane is 3.0 μm and 5.0 μm. 3 and No. As for 4, the contents of mineral oil, animal and vegetable oil and BOD are all reduced as compared with the contents after use. It is considered that this is because when the average pore diameter of the hollow fiber membrane is the above value, the floating oil contained in the used grinding fluid can be effectively separated.

1,21 Grinding liquid regeneration device 2 Grinding liquid storage tank 3 Membrane separation module 4 Grinding waste discharge tank 5 Pump 6 Discharge pipe 22 Coagulant addition mechanism 22a Supply pipe 22b Stirrer A Grinding waste B Coagulant X Used grinding liquid Y Regeneration Grinding fluid

Claims (4)

A device for regenerating used grinding fluid containing grinding debris.
A storage tank for storing the used grinding fluid and
A membrane separation module having a filtration membrane for separating the grinding debris from the used grinding fluid stored in the storage tank is provided.
The filtration membrane contains a plurality of hollow fiber membranes made of synthetic resin.
The pores of the hollow fiber membrane are elongated with the axial direction of the hollow fiber membrane as the long axis.
A grinding fluid regenerating device having an average pore diameter of 1.0 μm or more and 10.0 μm or less of the hollow fiber membrane . The regenerating device for a grinding fluid according to claim 1, further comprising a flocculant addition mechanism for adding a flocculant to the used grinding fluid stored in the storage tank. The regenerating device for a grinding fluid according to claim 1 or 2, wherein the main component of the hollow fiber membrane is polytetrafluoroethylene. It is a method of regenerating used grinding fluid containing grinding debris.
A membrane separation step for separating the grinding debris from the used grinding fluid by a filtration membrane is provided.
The filtration membrane contains a plurality of hollow fiber membranes made of synthetic resin.
The pores of the hollow fiber membrane are elongated with the axial direction of the hollow fiber membrane as the long axis.
A method for regenerating a grinding fluid having an average pore diameter of 1.0 μm or more and 10.0 μm or less.

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