WO2015071942A1

WO2015071942A1 - Filtration device, filtration method, acetate fiber manufacturing method

Info

Publication number: WO2015071942A1
Application number: PCT/JP2013/006756
Authority: WO
Inventors: 伊藤　圭介; 小島　昭男
Original assignee: 株式会社ダイセル
Priority date: 2013-11-18
Filing date: 2013-11-18
Publication date: 2015-05-21
Also published as: CN105745000A

Abstract

This filtration device (1) repeatedly alternates between filtration, in which a filtration solution is pressurized and passed through a filtration surface (10), and cleaning, in which the filtration surface, which is cut off from the outside, is cleaned. This filtration device (1) is provided with a filtration material (12) having the filtration surface (10), and with a container (13) which houses the filtration material (12) in a state cut off from the outside. The container (13) comprises a container main body (21) and a transparent unit (40) which is provided partially in the container main body (21) and which makes the state of the filtration surface (10) visible from the outside.

Description

Filtration apparatus, filtration method, and production method of acetate fiber

The present invention relates to a filtration apparatus and a filtration method for intermittently performing filtration while periodically recovering the filtration ability by repeating filtration and washing of the filtration surface alternately and washing the filtration surface. The present invention relates to a method for producing an acetate fiber by filtering a spinning dope using such a filtration apparatus.

In the production of acetate fiber, a raw material cellulose acetate flake is dissolved in an organic solvent such as acetone to prepare a spinning stock solution, and the spinning stock solution is extruded from a spinneret to dry-spin cellulose acetate. Using a spinneret having a large number of pores, acetate tow is produced by bundling a large number of acetate single fibers spun from each of the pores so as to form a fiber assembly called tow yarn. A single fiber thin acetate tow is suitably used for a tobacco filter. In particular, acetate tow used for cigarette filters has a single fiber diameter as thin as, for example, 3.5 denier (note that even the most common fiber has the smallest single fiber diameter of about 20 denier).

In order to make a single filament of acetate tow thin, it is effective to make the spinning dope high in concentration, but the concentration is restricted by solubility. In order to increase the concentration to some extent and make the single fiber thin, it is necessary to make the pores of the spinneret smaller. When this happens, the pores are blocked by minute foreign substances and thread breakage is induced, so that the yield rate decreases. Therefore, the spinning dope is filtered with high accuracy by a filtration device before being sent to the spinneret, and foreign matters such as mixed foreign matters and gel-like insoluble matter are removed (see, for example, Patent Document 1).

In other techniques for shaping polymer compounds, it is important to filter the raw material solution before shaping (see, for example, Patent Documents 2 to 4). U.S. Patent No. 6,057,032 teaches filtering the dope prior to wet spinning. U.S. Patent Nos. 5,098,036 and 5,496 teach the filtration of cellulose ester solutions prior to solution casting.

The raw material solution of acetate tow and other polymer products is required to have a high concentration without impurities, and the viscosity increases if the concentration is high. Therefore, in addition to the filter press taught in Patent Document 1, a leaf filter may be applied to the filtering device (see, for example, Patent Document 5). Since the filter press and the leaf filter can perform cake filtration under pressure, they are suitable for handling the raw material solution that receives the above request. In the acetate tow used for the cigarette filter, since the single fiber degree is small as described above, the concentration becomes high. And precise filtration of such a high concentration and high viscosity raw material solution is required.

In the filter press and leaf filter, clogging of the filter medium proceeds as the filtration time elapses. In order to keep the filtration rate, the filtration pressure must be increased during the filtration. On the other hand, in view of the specifications of the pump for pumping the raw material solution or the pressure resistance performance of the filtration device for receiving the pumped raw material solution, there is a limit to the increase in filtration pressure. Therefore, when the filtration pressure reaches a certain upper limit, the filtration surface is cleaned by temporarily interrupting the filtration in order to recover the filtration capacity. After washing the filtration surface, filtration resumes at the initialized filtration pressure.

The so-called precoat method can be used for the filter press and the leaf filter. In the precoat method, a slurry of the filter aid previously suspended is filtered to form a filter aid cake (precoat layer) on the original filter surface of the filter medium. Thereafter, the raw material solution is pumped and the raw material solution is filtered using the precoat layer as a filter medium. The presence of the precoat layer can prevent the original filter medium from opening, so that the precoat method is particularly useful for pressure filtration of a high-viscosity fluid such as a spinning dope. When the precoat method is used, the precoat layer is discarded when the filtration surface is washed, and the precoat layer is renewed on the filtration surface before the filtration is resumed.

In Patent Document 5, in order to automatically peel the cake from the filtration surface, the filter leaf portion in the pressure vessel is rotated and the cake is shaken down by centrifugal force. The dropped cake is discharged from the discharge port at the bottom of the container. As described above, the leaf filter is advantageous in that the work at the time of filtration interruption can be easily saved as compared with the filter press. Moreover, in patent document 5, in order to form a cake uniformly on each filtration surface, the one or more stock solution inlet parts are provided in the center part of the pressure vessel.

JP-A-5-117302 Japanese National Patent Publication No. 8-510681 JP 2008-63403 A Japanese Patent Laid-Open No. 11-254594 JP-A-11-128620

In order to maintain a high filtration capacity, it is important to completely remove the cake (including the precoat layer) from the filtration surface when washing the filtration surface. If the cake remains partially, the renewed precoat layer is deposited thereon, resulting in uneven thickness of the precoat layer.

完全 Complete removal of the cake is essential to maintain high productivity of acetate tow and other polymer products. If cake remains, the initial filtration pressure of the resumed filtration will increase. In addition, clogging progresses rapidly during the resumed filtration, and the rate of increase in filtration pressure increases. Then, the filtration must be interrupted frequently for cleaning, and product productivity is reduced. In particular, if the raw material solution has a high viscosity like a spinning stock solution, the raw material solution tends to remain on the filtration surface when the filtration surface is washed, and if the raw material solution remains, the rate of increase in the filtration pressure is further increased. .

In order to maintain a high filtration capacity, it is important that the precoat layer on the entire filtration surface has a uniform and appropriate thickness and that there is no thickness unevenness in each precoat layer. For example, when the precoat layer is thinner than an appropriate thickness, the foreign matter in the raw material solution cannot be sufficiently filtered.

Thus, in producing acetate tow and other polymer products using the filtered raw material solution, in order to maintain high filtration capacity and product productivity, the state of the filtration surface during the washing of the filtration surface or the formation of the precoat layer. It is desirable to manage.

However, in the leaf filter taught in Patent Document 5, since the filter medium is accommodated in the pressure vessel, the filtration surface cannot be visually confirmed. For this reason, although the cleaning of the filtration surface is automated, the user of the filtration device cannot easily confirm from the outside whether the cake has actually been completely removed from the filtration surface.

Also, according to Patent Document 5, it may be possible to form a cake uniformly under specific operating conditions. However, when the operating conditions such as the properties, pressure, and flow rate of the raw material solution or the slurry containing the filter aid are changed, the cake may not be formed uniformly. And the user of a filtration apparatus cannot confirm easily from the exterior whether the cake was actually formed uniformly.

After all, even in the leaf filter, in order to check the condition of the filtration surface and determine its quality, thereby properly managing the condition of the filtration surface, as with the filter press, the filtration device is stopped and the filter medium is taken out. There is nothing else. If such a method is adopted, cost and time are required for the confirmation work, and product productivity is reduced. In particular, when the filtration device is large, a large work machine such as a crane is required, and the cost and time required for the confirmation work become enormous. When an organic solvent is used like a raw material solution of acetate tow, it is necessary to ensure safety against the organic solvent. Since the filtration device must be stopped, it is impossible to check the state of the filtration surface during filtration.

Therefore, an object of the present invention is to make it possible to easily and appropriately manage the state of the filtration surface, thereby maintaining a high filtration capacity and product productivity.

The filtration device according to the present invention is a filtration device in which filtration for pressurizing a filtrate solution to permeate the filtration surface and cleaning of the filtration surface blocked from the outside are repeated alternately, and the filtration medium having the filtration surface And a container that accommodates the filter medium in a state of being blocked from the outside, and the container is partially provided on the container main body and the container main body so that the state of the filtration surface can be visually recognized from the outside. And a transparent portion.

According to the said structure, even if the filtration surface is interrupted from the outside, the state of the filtration surface during filtration, after filtration (that is, before the start of washing), during washing and after washing (ie, before resumption of filtration) is transparent. It can be visually confirmed from the outside using the section. For example, after washing the filtration surface, it is easy to visually determine whether the cake has been completely discarded from the filtration surface and whether any cake remains on the filtration surface without removing the filter medium from the container. Can be confirmed. And based on the state of the confirmed filtration surface, it is possible to take appropriate measures such as re-washing before resuming the next filtration. Thus, the state of the filtration surface can be managed easily and appropriately without complicated confirmation work.

A photographing device for photographing the state of the filtration surface from the outside of the container through the transparent part may be further provided.

According to the above configuration, the user of the filtration device can visually confirm the state of the filtration surface using an image or a moving image photographed by the photographing device. Therefore, the size of the transparent part can be reduced. Therefore, even when filtration is performed under pressure, it is easy to ensure the pressure resistance of the transparent portion and its peripheral portion of the container. In addition, since the photographing apparatus is disposed outside the container, the photographing apparatus does not need to have pressure resistance and solvent resistance, and the photographing apparatus is selected with emphasis on other design requirements (size, resolution, field of view, etc.). be able to.

Before starting the filtration, a precoat layer is formed by depositing fine particles on the filtration surface. When the filtration surface is washed, the precoat layer is peeled off from the filtration surface, and the next filtration is resumed. A new precoat layer is formed before the imaging, and the imaging device is configured to image at least the formation state of the precoat layer or the state of the filtration surface after the precoat layer is peeled off and washed May be.

According to the above configuration, when the precoat method is used, the thickness of the precoat layer and the separation of the precoat layer can be easily managed. Therefore, it is possible to maintain high filtration capacity and product productivity.

A rotation mechanism for rotating the filter medium may be provided, and when the rotation mechanism is operated, the precoat layer on the filtration surface may move in the outer peripheral direction by centrifugal force, whereby the precoat layer may be peeled off from the filtration surface. .

According to the above configuration, when peeling of the precoat layer is automated, it can be easily confirmed whether or not the precoat layer has actually been completely peeled off. For this reason, the state of a filtration surface can be managed appropriately. Therefore, it becomes possible to appropriately form the renewed precoat layer, and it is possible to suppress an increase in the filtration pressure in the filtration that is resumed next.

A plurality of the filter media may be provided, each of the plurality of filter media may be provided with a plurality of the filtration surfaces, and the transparent portion may be configured so that a part or all of the plurality of filtration surfaces can be visually recognized from the outside.

According to the above configuration, when there are a plurality of filtration surfaces, it can be easily confirmed whether or not there is a variation in the state of each filtration surface. Therefore, the state of the filtration surface can be managed more highly.

An illumination device that irradiates light to the filtration surface may be further provided.

According to the above configuration, the state of the filtration surface can be more easily confirmed.

The container may have a pressure resistance sufficient to filter a filtrate stock solution having a viscosity of 100 poise or more.

According to the above configuration, even if the shielding property in the container main body is increased by increasing the pressure resistance, the state of the filtration surface can be easily confirmed through the transparent portion.

The waste pipe is further provided with a waste pipe that is connected to the container and forms a waste passage through which a precoat layer peeled off from the filtration surface flows as waste, and the waste pipe is partially provided on the pipe body and the pipe body. And a transparent portion that enables the waste material flowing through the waste material passage to be visually recognized from the outside.

According to the above configuration, the waste material can be visually recognized through the transparent portion of the waste material pipe. By using together with the transparent part of the container, the state of the filtration surface can be managed more highly. The internal pressure of the waste material passage is lower than the internal pressure of the container in which the filtration surface is arranged. For this reason, even when it is used for filtration of a high-concentration filtrate stock solution, it is possible to install a relatively large transparent portion without particularly worrying about pressure resistance if it is a waste pipe.

The filtration surface may be oriented horizontally, and the filtrate stock solution may flow vertically with respect to the filtration surface.

According to the above configuration, the precoat layer formed on the filtration surface can be easily held uniformly.

The filtration method according to the present invention is a filtration method of filtering a stock solution using the above-described filtration device, wherein a precoat layer forming step of forming a precoat layer by depositing fine particles on the filtration surface, and the precoat After the layer formation step, pressurize the filtrate stock solution and filter through the precoat layer and the filtration surface, and when the filtration capacity decreases due to the filtration surface being blocked in the filtration step, the filtration step is stopped, A cleaning step of peeling off the precoat layer from the filtration surface and washing the filtration surface, and restarting the filtration step after performing the precoat layer forming step after the washing step, and at least from the washing step In the stage during the transition to the precoat layer forming process or the stage during the transition from the precoat layer forming process to the filtration process, It further includes a determination step for determining the quality of the state of the filtration surface confirmed through the transparent portion. When the determination step determines good, the process proceeds to the next step, and when the determination step determines negative, the previous step Redo the process.

According to the above method, the state of the filtration surface can be easily and appropriately managed, so that the filtration ability can be maintained high.

The method for producing acetate fiber according to the present invention is a method for producing acetate fiber, in which the spinning dope is filtered using the filtration device described above, and the filtered spinning dope is extruded from the spinneret to dry-spin cellulose acetate. The filtration method described above is used in the filtration process.

According to the above method, the state of the filtration surface can be easily and appropriately managed, so that the filtration capacity is maintained high and the productivity of acetate fibers is maintained high.

According to the present invention, it is possible to easily and appropriately manage the state of the filtration surface, thereby maintaining high filtration capacity and product productivity.

It is a conceptual diagram which shows the manufacturing method of the acetate fiber which concerns on this embodiment. It is a fragmentary sectional view showing an important section of a filtration device concerning this embodiment. FIG. 3 is a cross-sectional view taken along line III-III in FIG. It is a flowchart which shows the filtration method which concerns on this embodiment. It is a flowchart which shows the washing | cleaning process shown in FIG. 4, and the subsequent determination process. It is a flowchart which shows the precoat layer formation process shown in FIG. 4, and a subsequent determination process.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Throughout the drawings, the same or corresponding elements are denoted by the same reference numerals, and redundant description thereof is omitted.

FIG. 1 is a conceptual diagram showing a method for producing acetate fibers according to this embodiment. As shown in FIG. 1, in the production of acetate fibers, first, a spinning dope is prepared by dissolving cellulose acetate flakes as raw materials with acetone. The spinning dope has a high concentration, for example, a high viscosity of 300 to 900 poise, preferably 400 to 700 poise at 50 degrees Celsius. By making such a numerical range, it is possible to achieve both spinning easily and maintaining the cleaning efficiency of the filtration surface. The spinning dope may contain coloring additives such as titanium (IV) oxide.

The spinning dope is filtered using the filtration device 1, thereby removing impurities in the spinning dope. The filtered spinning solution is sent to the dry spinning machine 2 and pushed out from the spinneret 2a into the spinning cylinder 2b. Cellulose acetate is dry-spun in the spinning cylinder 2b. That is, acetone evaporates in the spinning cylinder 2b, and the cellulose acetate is solidified to form a yarn. The yarn is discharged out of the spinning cylinder 2b and scraped off. Thereafter, the yarn is subjected to post-treatment such as crimping and drying, and then packed.

The spinneret 2a may have a large number of pores. In that case, a tow yarn is formed by the dry spinning machine 2 by bundling a large number of acetate single fibers discharged from each of the pores, and an acetate tow product is obtained by post-processing and packing the tow yarn in the same manner as described above. Manufactured.

The method for producing acetate fibers (including acetate tow) according to the present embodiment is characterized by at least a filtration treatment, whereby the filtration capacity and the productivity of acetate fibers can be maintained high. Hereinafter, the filtration apparatus 1 and the filtration method using this filtration apparatus 1 are demonstrated. In the method for producing acetate fibers according to the present embodiment, the filtration method described later is used for the filtration treatment of the spinning dope.

The filtration device 1 and the filtration method described later can be applied to the production of other fibers that are dry-spun, such as acrylic or vinylon. Furthermore, it can be applied to the production of wet-spun fibers and the production of polymer products other than fibers such as cellulose films.

[Filtering equipment]
FIG. 1 includes a cross-sectional view of a filtration device 1 according to the present embodiment. A filtration device 1 shown in FIG. 1 is a pressurized cake filter. The filtration device 1 alternately repeats filtration that pressurizes a filtration stock solution (for example, a spinning stock solution of acetate fiber) and permeates the filtration surface 10 and washing of the filtration surface 10. When the filtration capacity decreases due to the blocking of the filtration surface 10, the filtration is stopped and the washing is started. In this cleaning, the cake is peeled off from the filtration surface 10. Filtration is intermittently performed while periodically recovering the filtration capacity by washing the filtration surface 10.

The filtration device 1 performs cake filtration using a precoat method. Before the filtration is started, the precoat layer 15 is formed by depositing fine particles on the filtration surface 10. The fine particles are filter aids such as diatomaceous earth or perlite. By passing the slurry in which the fine particles are suspended through the filtration surface 10, the fine particles are deposited on the filtration surface 10 to form the precoat layer 15. In the subsequent filtration, the filtered stock solution is pressurized so as to pass through the precoat layer 15 and the filtration surface 10, and the precoat layer 15 functions as a filter medium. In the subsequent cleaning, the precoat layer 15 is peeled off from the filtration surface 10. After this washing, a new precoat layer 15 is formed on the filtration surface 10, and then filtration of the stock solution is resumed.

The filtration device 1 according to this embodiment is a leaf filter as an example of a filter capable of realizing the above operation. The filtration device 1 includes a stem 11, one or more filter media 12 having a filtration surface 10, and a container 13 that accommodates the stem 11 and the filter media 12 while being blocked from the outside. In the production of acetate fiber, the filtration device 1 is relatively large. FIG. 1 shows only a few filter media 12 for convenience of illustration, but in the large-sized filter device 1, the number of filter media 12 ranges from several tens (for example, 40 to 90).

The plurality of filter media 12 are arranged at intervals in the axial direction of the stem 11 and are detachably coupled to the stem 11. Each filter medium 12 is formed in a leaf shape or a plate shape, and extends from the stem 11 in the radial direction. One surface of the filter medium 12 forms a filtration surface 10, and the filtration surface 10 is substantially perpendicular to the axis A of the stem 11. For example, the filter medium 12 is disk-shaped and the filter surface 10 is circular. At this time, each filter medium 12 is arranged substantially coaxially with the stem 11.

The container 13 has a container body 21 that forms a sealed inner space 20, and the stem 11 and the filter medium 12 are disposed in the inner space 20. The container main body 21 is formed in a substantially cylindrical shape. The container body 21 has a peripheral wall 22 that defines the inner space 20 on its inner peripheral surface and surrounds the filter medium 12, a first end wall 23 that is provided at one end of the peripheral wall 22 and closes the inner space 20, And a second end wall 24 that is provided at the other end of the peripheral wall 22 and closes the inner space 20.

The filtration device 1 includes a liquid supply port 26, a filtrate recovery port 27, a gas supply port 28, and a waste material discharge port 29. The liquid supply port 26 communicates with the inner space 20 and is connected to a stock solution source 31, a slurry source 32, and a cleaning solution source (not shown) outside the container 13, respectively. The filtered stock solution from the stock solution source 31, the slurry containing the filter aid from the slurry source 32, and the cleaning solution from the cleaning solution source pass through the liquid supply port 26 to the inner space 20 based on the operation of the liquid supply pump 34 and valves 35a to 35c. And selectively supplied. The slurry is used for forming the precoat layer 15, and the cleaning liquid is used for cleaning the filtration surface 10. The stock solution source 31 is, for example, a dissolving machine for preparing a filtered stock solution. The slurry source 32 is a stirrer for preparing, for example, a slurry in which a filter aid is suspended. The cleaning liquid source is, for example, a tank that stores the cleaning liquid. The cleaning liquid may be the same as the solvent of the filtrate stock solution. In this case, the cleaning liquid source may also serve as a tank that stores the solvent of the filter stock solution.

The stem 11 is formed hollow. The filtrate obtained by allowing the filtrate stock solution to pass through the filtration surface 10 flows toward the center of the filter medium 12 and flows into the hollow stem 11. The filtrate collection port 27 communicates with the inside of the stem 11, and the filtrate in the stem 11 is collected outside the container 13 through the filtrate collection port 27. The gas supply port 28 communicates with the inner space 20 and is connected to a gas source (not shown) outside the container 13. The gas from the gas source is supplied to the inner space 20 through the gas supply port 28. Preferably, this gas is an inert gas such as nitrogen or argon.

The waste material discharge port 29 communicates with the inner space 20. The waste material is generated by washing the filtration surface 10, and the waste material includes the precoat layer 15 peeled off from the filtration surface 10. The waste material is discharged out of the container 13 through the waste material discharge port 29 before starting the formation of the next precoat layer 15. The filtration device 1 includes a waste material pipe 36 that forms a waste material passage 37 through which the separated precoat layer 15 flows as waste material. The waste material pipe 36 is connected to the container 13 and disposed outside the container 13. The waste material passage 37 communicates with the inner space 20 through the waste material discharge port 29 and extends from the waste material discharge port 29 to the outside of the container 13.

The filtration device 1 includes a rotation mechanism 25 that rotates the filter medium 12. The rotation mechanism 25 according to the present embodiment is configured by an electric motor that rotationally drives the stem 11 around its own axis A. When the rotating mechanism 25 operates, the stem 11 rotates, and the plurality of filter media 12 attached to the stem 11 rotate at the same time. Thereby, when the precoat layer 15 is formed on the filtration surface 10, the precoat layer 15 is moved in the outer peripheral direction by a centrifugal force and peeled off from the filtration surface 10. In this way, when the filtration surface 10 is cleaned, the peeling of the precoat layer 15 is automated.

This filtration device 1 is a vertical type. That is, the stem 11 is directed vertically, the filtration surface 10 and the filter medium 12 are directed horizontally, and the filtrate stock solution flows vertically with respect to the filtration surface 10 during filtration. The upper surface of the filter medium 12 forms a filtration surface 10, and the filtrate stock solution permeates the filtration surface 10 from top to bottom. The peripheral wall 22 is vertically oriented and arranged coaxially with the stem 11. The first end wall 23 forms the ceiling of the container 13, and the second end wall 24 forms the bottom of the container 13. A liquid supply port 26 and a gas supply port 28 are provided in the ceiling portion (the upper end portion of the peripheral wall 22 or the first end wall 23) of the container 13, a filtrate recovery port 27 is provided in the lower portion of the stem 11, and a waste material discharge port 29. Is provided at the bottom of the container 13 (the lower end of the peripheral wall 22 or the second end wall 24). However, these arrangements are examples and can be changed as appropriate.

The filtration device 1 includes a single liquid supply port 26, but may include a plurality of liquid supply ports 26. The filtrate stock solution, the slurry containing the filter aid, and the cleaning liquid are supplied to the inner space 20 through the common liquid supply port 26, but at least one of them may be supplied to the inner space 20 through the dedicated supply port.

The container body 21 of the container 13 is made of a metal such as stainless steel and has pressure resistance required for pressure filtration. In particular, in this embodiment, the container main body 21 has a pressure resistance that can sufficiently withstand the filtration pressure required for the filtration of the filtrate stock having a viscosity of 100 poise or more. The filtration device 1 can also be suitably used for the filtration treatment of the spinning dope having a high viscosity as described above. While the pressure resistance is ensured, the container body 21 does not have optical transparency. Therefore, the worker cannot visually recognize the inner space 20 and the filter medium 12 accommodated therein from the outside of the container 13 through the container main body 21. Thus, the filtration surface 10 is shut off from the outside.

Therefore, the container 13 includes a container transparent portion 40 that is partially provided in the container main body portion 21 so that the state of the filter surface 10 can be visually recognized from the outside. The container transparent part 40 is formed of a transparent pressure-resistant glass material such as quartz glass or acrylic glass. The container 13 is required to have a pressure resistance that can sufficiently withstand the pressure filtration of the filtration stock solution having a high viscosity as described above. The container transparent portion 40 according to the present embodiment is provided in the container main body portion 21 so as to suppress the processing of the container main body portion 21 as much as possible and suppress the decrease in pressure resistance performance as much as possible.

FIG. 2 is a partial cross-sectional view showing the main part of the filtration device 1 shown in FIG. As shown in FIG. 2, the container transparent part 40 cuts off a part of the peripheral wall 22 of the container main body part 21, and a lump made of the above-described glass material so as to close the cut-off area is applied to the peripheral wall 22. By bonding, the container body 21 is provided. The peripheral wall 22 is partially cut off by drilling a substantially circular small hole (for example, a diameter of 10 to 30 mm) using a tool such as a drill. The container transparent part 40 is as small as such a small hole 22a, so that the pressure resistance of the container 13 can be maintained high.

If the container transparent portion 40 is small, it may be difficult for an operator to visually recognize the state of the filtration surface 10 with the naked eye. Therefore, the filtration device 1 includes a photographing device 41 that photographs the state of the filtration surface 10 from the outside of the container 13 through the transparent container portion 40. The photographing device 41 may be a still camera capable of photographing only a still image, but it is more preferable that the photographing device 41 is configured to be capable of photographing a moving image. Although detailed illustration is omitted, the imaging device 41 is disposed so that the objective lens is brought close to the container transparent portion 40. As will be described in detail in the description of the subsequent filtration method, the photographing device 41 is configured to photograph the formation state of the precoat layer 15, the washing state of the precoat layer 15, and the state of the filtration surface 10 after washing.

If the imaging device 41 is used, even if the container transparent part 40 is small, the worker can visually recognize the state of the filtration surface 10 by referring to the imaging result of the imaging device 41. Further, when the filtration device 1 is large and vertical and the container transparent portion 40 is disposed at a high place, the worker does not have to perform an operation of checking the filtration surface 10 at the high place.

The filtration device 1 includes a camera holder 42 that holds the photographing device 41 outside the container 13. For example, the camera holder 42 has a cylindrical shape opened at both ends. One end of the camera holder 42 is inserted into a small hole 22a formed in the peripheral wall 22, and is joined to the outer surface of the peripheral wall 22 in an air-tight and liquid-tight manner. The container transparent part 40 is closely fitted to one end of the camera holder 42, and the inside of the camera holder 42 is isolated from the inner space 20 of the container 13 through the container transparent part 40. The photographing device 41 is preferably a small CCD camera having a cylindrical appearance. In that case, the imaging device 41 is fitted into the camera holder 42 through the opening on the other end side of the camera holder 42, whereby the imaging device 41 is placed in the container 13 with the objective lens being close to the container transparent part 40 outside the container 13. Positioned against.

When the photographing apparatus 41 is disposed outside the container 13, the photographing apparatus 41 may not have pressure resistance and solvent resistance. Therefore, the imaging device 41 can be selected with emphasis on other design requirements (size, resolution, field of view, etc.).

The imaging surface of the imaging device 41 is composed of, for example, a photoelectric conversion element such as a CCD, and the imaging result of the imaging device 41 is transferred to the computer 45 as electronic data (hereinafter referred to as imaging data). The worker can refer to the photographing result by displaying the photographing data on the display of the computer 45, and can visually confirm the state of the filtration surface 10.

The filtration device 1 includes an illumination device 44 that irradiates the filtration surface 10 with light. The illumination device 44 may be accommodated in the container 13 or may be disposed outside the container 13. When arranged outside the container 13, the illumination device 44 may be held by the camera holder 42 or may be built in the photographing device 41. By illuminating the filtration surface 10, a clear photographing result can be obtained.

The central axis B of the camera holder 42 extends away from the filtration surface 10 to be photographed from the peripheral wall 22 while being inclined with respect to the axis A of the stem 11. By providing the camera holder 42 in this way, the filtering surface 10 can be photographed by the photographing device 41 held by the camera holder 42.

FIG. 3 is a cross-sectional view of the filtration device 1 cut along the line III-III in FIG. As shown in FIG. 3, the photographing device 41 is capable of photographing a region 43 that is a part in the circumferential direction of the filtration surface 10 and includes a part of the inner peripheral edge and a part of the outer peripheral edge of the filtration surface 10. That's fine. Even if the field of view of the imaging device 41 is so small that only the limited region 43 can be imaged, the moving mechanism 25 (see FIG. 1) continues to shoot moving images while rotating the filtration surface 10 or still images. Can be obtained as a result of continuous shooting.

Returning to FIG. 1, the filtering device 1 has a plurality of filter media 12, and the container transparent part 40 is in a state of a part or all of the filter surfaces 10 among the plurality of filter surfaces 10 individually corresponding to the plurality of filter media 12. Is configured to be visible from the outside. Here, the plurality of filter media 12 have the same shape. Further, in order to increase the ratio of the filtration area to the volume of the container 13 as much as possible, the interval between the filter media 12 is set as small as possible. Therefore, in reality, it is possible to visually recognize the state of only one filtration surface 10 through one container transparent portion 40. Therefore, the container body 21 is provided with a plurality of container transparent portions 40.

As described above, if the filtration device 1 is large, the number of filter media 12 reaches several tens. If the same number of container transparent parts 40 as the filter medium 12 are provided in the container main body 21 so that the state of all the filtration surfaces 10 can be visually recognized, the manufacture of the filtration device 1 becomes complicated. In this embodiment, the container transparent part 40 is comprised so that the state of only some filtration surfaces 10 can be visually recognized from the outside. Thereby, coexistence with confirming the state of the filtration surface 10 highly and manufacturing the filtration apparatus 1 simply is achieved.

For example, the container 13 includes three container transparent portions 40 (40a to 40c). The container transparent part 40a makes the state of the filtration surface 10a located near the liquid supply port 26, preferably closest to the liquid supply port 26 visible. The container transparent part 40b makes the state of the filtration surface 10b located near the waste material discharge port 29, preferably closest to the waste material discharge port 29 visible. Thereby, even if a drift occurs near the liquid supply port 26 or the waste material discharge port 29 and the state of the filtration surfaces 10a and 10b becomes unstable, this can be visually recognized through the container

transparent portions

40a and 40b. The container transparent part 40c enables visual recognition of the state of the filtration surface 10c located in the middle (not necessarily the center) between the filtration surfaces 10a and 10b. By confirming the state of the filtration surfaces 10a and 10b while referring to the state of the filtration surface 10c, it becomes easy to determine the quality of the state of the filtration surfaces 10a and 10b.

Further, the waste material pipe 36 has a pipe body portion 38 that forms a waste material passage 37. The internal pressure of the waste material passage 37 during the distribution of the waste material is lower than the internal pressure of the container 13 during filtration. For this reason, the piping main body portion 38 is not required to have a pressure resistance performance as high as that of the container main body portion 21. The waste material pipe 36 is, for example, a steel pipe or a synthetic resin pipe. The pipe main body 38 does not have light transmittance. Therefore, the worker cannot visually recognize the waste material passage 37 and the waste material flowing through the pipe main body portion 38 from the outside of the waste material pipe 36.

Therefore, the waste material pipe 36 includes a pipe transparent portion 50 that is partially provided in the pipe main body portion 38 so that the waste material flowing through the waste material passage 37 can be visually recognized from the outside. The pipe transparent part 50 is formed of a transparent pressure-resistant glass material such as quartz glass or acrylic glass, similarly to the container transparent part 40. For example, the pipe transparent part 50 cuts off a part of the pipe main body part 38, and joins a plate material made of the above-mentioned transparent glass material to the pipe main body part 38 so as to block the cut-off area. Provided in the main body 38. The pipe transparent part 50 (that is, the region cut off from the pipe main body part 38) has a sufficiently large size so that an operator can visually recognize the waste material passage 37 through the pipe transparent part 50 with the naked eye. Is also big. Since the internal pressure of the waste material passage 37 is relatively low, high pressure resistance is not required when installing the transparent pipe portion 50. Therefore, even if a part of the pipe main body portion 36 is cut off with a large size that allows the operator to visually check, there is no practical problem. In the present embodiment, the single transparent pipe portion 50 is provided in the waste material pipe, but a plurality of transparent pipe portions 50 may be provided in the waste material pipe 36 as necessary.

[Filtration method]
FIG. 4 is a flowchart showing the filtration method according to the present embodiment. In the following description, the reference numerals shown in FIGS. 1 to 3 are appropriately attached to the components of the filtration device 1. As shown in FIG. 4, as a basic procedure of the filtration method according to the present embodiment, first, the precoat layer 15 is formed by depositing fine particles on the filtration surface 10 (precoat layer forming step S1). After the precoat layer forming step S1, the filtered stock solution is supplied to the inner space 20 of the container 13 through the liquid supply port 26 while being pressurized by the liquid supply pump 34, and the filtered stock solution is filtered through the precoat layer 15 and the filtration surface 10 ( Filtration step S2). If the filtration capacity is sufficient (S3: NO), the filtration step S2 is continued. When the filtration capacity decreases due to the blocking of the filtration surface 10 (S3: YES), the filtration step S2 is stopped, the precoat layer 15 is peeled off from the filtration surface 10 and the filtration surface 10 is washed (washing step S4). When the cleaning step S4 is completed, the precoat layer forming step S1 is performed to form a new precoat layer 15 on the filtration surface 10, and then the filtration step S2 is restarted.

In the filtration step S2, the discharge pressure of the liquid supply pump 34 and thus the filtration pressure are adjusted so that the filtration rate (filtrate flow rate) is kept constant. In the filtration step S2, since the clogging of the filter medium 12 progresses and the filtration capacity gradually decreases, the discharge pressure and the filtration pressure are gradually increased to make the filtration speed constant. In step S3, as a specific example, the filtration capacity is determined based on whether or not the discharge pressure or the filtration pressure has increased to a predetermined maximum pressure. If the pressure is less than the maximum pressure, the filtration step S2 is continued assuming that the filtration capability remains, and if the maximum pressure is reached, the filtration step S2 is terminated because the filtration capability is reduced.

The filtration method according to the present embodiment includes a determination step S5 that determines whether the state of the filtration surface 10 confirmed through the container transparent part 40 is good or not during the transition from the cleaning step S4 to the precoat layer formation step S1. In this determination step S5, it is determined whether or not the state of the filter surface 10 after cleaning is good, typically whether or not the precoat layer 15 has actually been completely peeled from the filter surface 10 in the cleaning step S4. When a good determination is made in this determination step S5 (S5: OK), the process proceeds to the next step, that is, the precoat layer formation step S1. When a negative determination is made in this determination step S5 (S5: NG), the previous step, that is, the cleaning step S4 is performed again.

Further, the filtration method according to the present embodiment includes a determination step S6 for determining whether the state of the filtration surface 10 confirmed through the container transparent portion 40 is good or not during the transition from the precoat layer forming step S1 to the filtration step S2. Including. In this determination step S6, it is determined whether or not the precoat layer 15 is formed properly, that is, whether or not the precoat layer 15 is appropriately formed on the filtration surface 10 in the precoat layer formation step S1. When a good determination is made in this determination step S6 (S6: OK), the process proceeds to the next step, that is, the filtration step S2. If a negative determination is made in this determination step S12 (S6: NG), the previous step, that is, the precoat layer formation step S1 is performed again. In this embodiment, in order to form an appropriate precoat layer 15 after the defective precoat layer 15 is peeled off from the filtration surface 10, the precoat layer forming step S1 is performed again after returning to the cleaning step S4.

FIG. 5 is a flowchart showing the cleaning step S4 shown in FIG. 4 and the subsequent determination step S5. As shown in FIG. 5, in the cleaning step S4, first, the filtrate stock solution in the container 13 is discharged from the waste material discharge port 29 (step S41). Next, the cleaning liquid is injected into the container 13 from the liquid supply port 26, and the injected cleaning liquid is discharged from the waste material discharge port 29 (step S42). The washing solution can dissolve the solute dissolved in the filtration stock solution (if the filtration stock solution is a spinning stock solution of acetate fiber), and the solvent of the filtration stock solution (if the filtration stock solution is a spinning stock solution of acetate fiber, For example, acetone) can be suitably applied. The washing liquid can dissolve the gel-like insoluble matter remaining on the filtration surface 10a, and the insoluble matter can be removed from the filtration surface 10a by the washing liquid.

During execution of steps S41 and S42, the worker visually recognizes the waste liquid flowing through the waste material passage 36 through the pipe transparent portion 50, and confirms the viscosity of the waste liquid. If it is recognized that the viscosity of the waste liquid is high (S43: NO), the injection and discharge of the cleaning liquid are continued assuming that the filtering stock solution and its impurities remain in the container 13 (S42). If it is recognized that the viscosity of the waste liquid has decreased (S43: YES), the injection of the cleaning liquid is stopped. Since the continuation or stop of the injection of the cleaning liquid is determined while checking the viscosity of the waste liquid, it is possible to prevent the stock filtrate and its contaminants from remaining in the container 13. For this reason, in the next filtration process S2, the rate of decrease in filtration capacity (rate of increase in filtration pressure) can be suitably suppressed, and the period for carrying out the next filtration process S2 can be increased.

Next, an inert gas is injected into the container 13 from the gas supply port 28, and the inert gas is filled into the container 13 (step S44). When the replacement with the inert gas is completed, the rotation mechanism 25 is operated, and the precoat layer 15 is peeled off from the filtration surface 10 (step S45). The cleaning liquid is again injected, and the precoat layer 15 shaken off from the filtration surface 10 is discharged together with the cleaning liquid from the waste material discharge port 29 (step S46). Thereby, cleaning process S4 is complete | finished.

In the determination step S5, the photographing device 41 and the illumination device 44 are activated (step S51). Next, the rotation mechanism 25 is operated to rotate the filter medium 12 (step S52). The rotation speed of the filter medium 12 in the determination step S5 is slower than the rotation speed of the filter medium 12 in the cleaning process S4. While the filter medium 12 is rotating, the photographing device 41 continues to photograph the state of the filtered surface 10 after washing through the container transparent part 40. When the filter medium 12 rotates once, the rotation mechanism 25 is stopped and the photographing is finished. Next, the photographic data is transferred to the computer 45 (step S53), and the photographic data is displayed on the display of the computer 45. The worker confirms the state of the filtration surface 10 through the container transparent part 40 by referring to the displayed photographing data (step S54).

At this time, the worker checks whether the precoat layer 15 is completely peeled off or remains on the filtration surface 10, and thereby determines whether the state of the filtration surface 10 after washing is good or bad. If it is determined that the precoat layer 15 remains on the filtration surface 10 and the state of the filtration surface 10 is defective (S55: NG), the process returns to the cleaning step S4. At this time, as a specific example, the process can return to step S45 in which the precoat layer 15 is peeled off. In the cleaning step S4 to be performed again, the operation parameters of the rotation mechanism 25 such as the rotation speed and rotation time of the filter medium 12 are appropriately changed so that the precoat layer 15 is completely peeled off from the filtration surface 10. If it is determined that the precoat layer is completely separated from the filtration surface 10 and the state of the filtration surface 10 is good (S55: OK), the process proceeds to the precoat layer formation step S1.

FIG. 6 is a flowchart showing the precoat layer forming step S1 shown in FIG. 4 and the subsequent determination step S6. As shown in FIG. 6, in the precoat layer forming step S1, first, a slurry in which a filter aid is suspended is poured into the container 13 from the liquid supply port 26, and the container 13 is filled with the slurry (step S11). . Next, the slurry is filtered under pressure (step S12), and the filtrate is discharged (step S13). Thereby, the filter aid is deposited on the filtration surface 10, and the precoat layer 15 is formed on the filtration surface 10. Thereafter, an inert gas is injected into the container 13 from the gas supply port 28, and the inert gas is filled into the container 13 (step S14). Thereby, precoat layer formation process S1 is complete | finished.

In the determination step S6, as in the determination step S5, the photographing device 41 and the illumination device 44 are activated (step S61), the filter medium 12 is rotated (step S62), and the image pickup apparatus 41 is rotated while the filter medium 12 is rotating. The formation state of the precoat layer 15 is continuously photographed through the container transparent part 40. When the filter medium 12 rotates once, the rotation mechanism 25 is stopped and the photographing is finished. Next, the photographing data is transferred to the computer 45 (step S63), and the photographing data is displayed on the display of the computer 45. The worker confirms the state of the filtration surface 10 through the container transparent part 40 by referring to the displayed photographing data (step S64).

At this time, the worker refers to the photographing data, whether the thickness of the precoat layer 15 is within a desired range, and whether the thickness of the precoat layer 15 is uniform over the entire filtration surface 10. Confirm. Thereby, the worker can determine whether the precoat layer 15 is formed properly.

Here, both the filter aid and the filtration surface 10 are non-transparent, and both colors are different from each other. When diatomaceous earth is used as the filter aid, the color is, for example, white or amber color, and when pearlite is used as the filter aid, the color is, for example, white. When the filter medium 12 has a filter cloth made of chemical fiber and the surface of the filter cloth forms the filter surface 10, the filter cloth is preferably selected to have a color different from the filter aid, for example, gray or black. . The worker refers to the photographing data and confirms how much the color of the precoat layer 15 is mixed with the color component of the filter aid and the color component of the filter surface 10 to thereby determine the thickness of the precoat layer 15. It is possible to grasp this. If the color component of the filter aid is too strong, it can be determined that the thickness of the precoat layer 15 exceeds the desired range. If the color component of the filtration surface 10 is too strong, it can be determined that the thickness of the precoat layer 15 is smaller than the desired range. Whether or not thickness unevenness has occurred can be determined according to whether or not color unevenness is recognized. In particular, in the present embodiment, since shooting is performed using the illumination device 44, a clear shooting result can be obtained, thereby improving the determination accuracy.

If the thickness of the precoat layer 15 is not within the desired range, or the thickness of the precoat layer 15 is uneven, and the formation state of the precoat layer 15 is determined to be defective (S65: NG), cleaning is performed. Returning to the step S4 or the precoat layer forming step S1. As a specific example of returning to the cleaning step S4, the process can return to step S45 where the precoat layer 15 is peeled off. In the precoat layer forming step S1 to be performed again, for example, the filtration operation parameters such as the supply rate of the slurry 11, the discharge pressure of the liquid supply pump 34, and the filtration rate of the slurry 11 are appropriately changed. By performing trial and error of the filtration operation parameters, the optimum filtration operation parameters for appropriately forming the precoat layer 15 in the filtration device 1 can be obtained empirically. Therefore, it is possible to reduce the redo of the precoat layer forming step S1 by continuously performing the filtration method, thereby increasing productivity in the long run. If it is determined that the thickness of the precoat layer 15 is within the desired range, the thickness unevenness is not generated in the precoat layer 15, and the precoat layer 15 is formed well (S65: OK), filtration is performed. Proceed to step S2.

According to the filtration method according to the present embodiment implemented using the filtration device 1 having the above-described configuration, the filtration surface 10 is cleaned and precoated with the cleaning liquid in the container 13 having high pressure resistance and no light transmission. Even when the separation of the layer 15 from the filtration surface 10 is automatically performed, the state of the filtration surface 10 after washing can be visually confirmed through the container transparent portion 40. For this reason, the quality of the state of the filtration surface 10 after washing | cleaning can be determined. By repeating the cleaning step S4 until a good determination is obtained, it is easy to appropriately form the precoat layer in the next precoat layer forming step S1. As a result, it is possible to suppress the rate of decrease in filtration capacity (increase in filtration pressure) in the subsequent filtration step S2.

Further, even when the precoat layer 15 is automatically formed in the container 13 having high pressure resistance and no light transmittance, the formation state of the precoat layer 15 is visually confirmed through the container transparent portion 40. Can be confirmed. For this reason, the quality of the formation state of the precoat layer 15 can be determined. By repeating the precoat layer forming step S1 until a good determination is obtained, the rate of decrease in filtration capacity (increase in filtration pressure) can be suppressed in the subsequent filtration step S2.

Thus, the state of the filtration surface 10 after washing and the state of the filtration surface 10 after forming the precoat layer 15 can be managed easily and appropriately. Thereby, the filtration capability can be kept high in the filtration step S2. Moreover, the implementation period of the said filtration process S2 can be taken long, and productivity of a filtrate can be improved. When the filtration stock solution is a spinning stock solution of acetate fiber, it leads to an increase in the productivity of acetate fiber.

In step S46 in which the precoat layer in the cleaning step S4 is discharged as waste material, the worker may check the waste material flowing in the waste material passage 37 through the transparent pipe portion 50. By taking this confirmation result into consideration in the pass / fail determination in step S55, the pass / fail determination accuracy can be improved.

Further, under the condition that the inert gas is filled in the container 13, the imaging of the filtration surface 10 after the cleaning by the imaging device 41 is performed. Therefore, a clear photographing result can be obtained, and the accuracy of determining whether or not the cleaning is good is improved. The same applies to the case where the formation state of the precoat layer 15 is photographed. Therefore, the quality determination accuracy of the formation state of the precoat layer 15 is improved.

Although the filtration device, the filtration method, and the acetate fiber manufacturing method according to the embodiments have been described so far, the above-described configuration and method can be appropriately changed within the scope of the present invention.

The leaf filter may be a horizontal type. The filter device 1 may be a filter different from the leaf filter as long as it can perform pressurized cake filtration using the precoat method and the filter surface cannot be easily visually recognized from the outside. .

In the above embodiment, the photographing device 41 is configured to photograph both the formation state of the precoat layer 15 and the state of the filtration surface 10 after the precoat layer 15 is peeled off and cleaned. Moreover, the quality of the state of the filtration surface 10 is determined in both the stage during the transition from the cleaning process S4 to the precoat layer formation process S1 and the stage during the transition from the precoat layer formation process S1 to the filtration process S2. Determination steps S5 and S6. However, the photographing apparatus 41 may be configured to photograph at least the formation state of the precoat layer 15 or the state of the filtration surface 10 after the precoat layer 15 is peeled off and washed. The filtration method determines the quality of the state of the filtration surface 10 at least during the transition from the cleaning step S4 to the precoat layer formation step S1 or during the transition from the precoat layer formation step S1 to the filtration step S2. What is necessary is just to provide determination process S5, S6 to perform.

The present invention can be used for the filtration of various filtrate stock solutions, and is useful when used for the filtration treatment of a raw material solution of a polymer compound product, for example, a spinning stock solution of acetate fiber.

DESCRIPTION OF SYMBOLS 1 Filtration apparatus 2 Dry-type spinning machine 2a Spinneret 10 Filtration surface 12 Filter medium 13 Container 15 Precoat layer 21 Container main body part 25 Rotating mechanism 36 Waste material pipe 37 Waste material passage 38 Pipe main body part 40 Container transparent part 41 Photographing apparatus 44 Illumination apparatus 50 Piping transparent Part S1 Precoat layer forming step S2 Filtration step S4 Cleaning step S5, S6 Determination step

Claims

A filtration device in which filtration for pressurizing a filtrate solution to permeate the filtration surface and washing of the filtration surface blocked from the outside are repeated alternately,
A filter medium having the filtration surface;
A container for containing the filter medium in a state of being cut off from the outside,
The said container is a filtration apparatus which has a container main-body part and the transparent part which is partially provided in the said container main-body part and can visually recognize the state of the said filtration surface from the outside.
The filtration device according to claim 1, further comprising a photographing device that photographs the state of the filtration surface from the outside of the container through the transparent portion.
Before starting the filtration, a precoat layer is formed by depositing fine particles on the filtration surface. When the filtration surface is washed, the precoat layer is peeled off from the filtration surface, and the next filtration is resumed. A new precoat layer is formed before
The filtration device according to claim 2, wherein the photographing device is configured to photograph at least a formation state of the precoat layer or a state of the filtration surface after the precoat layer is peeled off and washed. .
A rotation mechanism for rotating the filter medium;
4. The method according to claim 1, wherein when the rotating mechanism is operated, the precoat layer on the filtration surface is moved in an outer peripheral direction by a centrifugal force, whereby the precoat layer is peeled off from the filtration surface. The filtration apparatus as described.
A plurality of the filter media are provided, and a plurality of the filtration surfaces are provided for each of the plurality of filter media,
The said transparent part is a filtration apparatus of any one of Claims 1 thru | or 4 comprised so that the state of a part or all of these filtration surfaces can be visually recognized from the outside.
The filtration device according to any one of claims 1 to 5, further comprising an illumination device that irradiates the filtration surface with light.
The filtration device according to any one of claims 1 to 6, wherein the container has a pressure resistance sufficient to filter a filtrate stock solution having a viscosity of 100 poise or more.
A waste material pipe connected to the container and forming a waste material passage in which a precoat layer peeled off from the filtration surface flows as waste material;
The waste material pipe includes a pipe main body portion and a transparent portion that is partially provided in the pipe main body portion and allows the waste material flowing through the waste material passage to be visually recognized from the outside. The filtration device according to item.
The filtration device according to any one of claims 1 to 8, wherein the filtration surface is oriented horizontally, and the filtrate stock solution flows vertically with respect to the filtration surface.
A filtration method of filtering a filtrate stock solution using the filtration device according to any one of claims 1 to 9,
A precoat layer forming step of forming a precoat layer by depositing fine particles on the filtration surface;
After the precoat layer forming step, a filtration step of pressurizing the filtrate stock solution and filtering through the precoat layer and the filtration surface;
In the filtration step, when the filtration capacity is reduced due to the clogging of the filtration surface, the filtration step is stopped, and the washing step of separating the precoat layer from the filtration surface to wash the filtration surface,
After performing the precoat layer forming step after the washing step, the filtration step is resumed,
At least during the transition from the cleaning process to the precoat layer forming process, or during the transition from the precoat layer forming process to the filtration process, the state of the filtration surface confirmed through the transparent portion It further comprises a determination step for determining pass / fail,
A filtration method that proceeds to the next step when a good determination is made in the determination step and restarts the previous step when a negative determination is made in the determination step.
A method for producing an acetate fiber, wherein the spinning solution is filtered using the filtration device according to any one of claims 1 to 9, and the filtered spinning solution is extruded from a spinneret to dry-spin cellulose acetate. And
The manufacturing method of an acetate fiber which uses the filtration method of Claim 10 in the said filtration process.