JP2014198326A - Method of manufacturing precise metal filter for polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a precise metal filter for a molten polymer which has been cleaned more precisely, especially including impurity particles which remains, by sticking, on a filtering secondary side positioned on an inner peripheral side, relating to a filter product.SOLUTION: There is prepared a metal filter which separates and filters a processed fluid between an inner peripheral side filtering surface which comprises a metal sintering porous filtering material to form an internal filtering chamber and an outer side filtering surface on its outer surface. A method of manufacturing a precise metal filter for a molten polymer includes a first cleaning stage in which ultrasonic wave vibration is radiated from an outer surface side to a filter in a first cleaning liquid so that foreign impurities sticking to a sintered filter material is released and floated, a second cleaning stage in which foreign impurities remaining in the filter are discharged and removed to the outside of the system by repeated pressure flow caused by a plurality of times of discharge processes in which, through a drain mechanism arranged in a second cleaning liquid, the filter after the first cleaning is depressurized in the filtering process direction at a sucking pressure 80KPa or less for exposing, and a drying stage in which the purified filter is further dry-processed.

Description

  The present invention relates to a method for producing a precision metal filter for a polymer, and in particular, it is purified to suppress the generation of impure foreign matters generated in a filtration process of a fluid to be processed (molten polymer) and to enable a high-quality processed product. The present invention relates to a method for manufacturing a clean filter.

  For example, various resin materials such as polyester and polyvinyl alcohol (PVA), in particular, fiber materials and film-like sheet materials made of thermoplastic resins are widely used as industrial materials and living materials for recent high-tech tips. The required characteristics are that the required quality of the raw material polymer has become more stringent due to higher functionality and higher performance according to the application and purpose of the target product, and how high accuracy is required at the polymer processing stage. However, as one of the measures, there is a demand for a filtration technique that completely removes the fine impurity particles in the raw polymer to the limit state.

  The level of cleanliness is that even for very fine levels of impurities such as 10 μm or less in the use of film materials for high-purity thin films where the polymer is used, for example, for electronic recording and optical communication, and its complete removal For this purpose, attempts have been made to improve and improve filtration technology and processing equipment.

  In addition, since such a molten polymer is produced in a state where the resin material is heated and melted to a temperature of, for example, 200 ° C. or higher, the metal used in the filtration device used, in particular, the constituent filter medium, can be made of metal or ceramic. Those made of heat-resistant materials such as manufactured products are used. In particular, filtration materials using sintered nonwoven fabrics of stainless steel fibers have many advantages such as the fineness of the pores formed, high porosity, low pressure loss, and high strength and machining. Have been used a lot.

  These filter media are used in filter products of various shapes, structures, and sizes that are compatible with the manufacturing equipment, but particularly in metal filters, problems such as stagnation, segregation, and clogging due to friction with the polymer, In the manufacturing stage, complicated multi-step processes such as sintering, welding, and heat treatment are required. Along with these processes, various impurities are formed on the filter medium, both inside and outside. It has been removed by cleaning with sonic waves.

  Similarly, as a treatment method in the case of clogging with use, discharge removal that flushes the adhering foreign matter accumulated on the surface by backwash pressure from the direction opposite to the filtration treatment direction is also performed, and the treatment is more completely performed. For this purpose, it is also known to perform treatment while applying ultrasonic cleaning. (For example, Patent Documents 1, 2, and 3)

  JP 2001-198422 A   JP 2009-189999 A   JP 2010-274238 A

    However, these conventional cleaning treatments mainly target relatively light foreign matter deposited on the surface of the filter as it is used, and the cleaning treatment also removes and removes by backwashing from the opposite direction of filtration. , Generated in the manufacturing process of the metal filter targeted by the present invention, for example, various auxiliary materials for sintering (for example, mold release agent) used during the filtering medium sintering process, and small pieces generated in the machining stage such as cutting No special foreign matter that remains deep inside the filter medium, such as an oxide film accompanying welding or pickling treatment, is considered.

  These foreign substances have been overlooked without much importance in conventional general applications (low-viscosity fluids), but are ignored especially for those molten polymer applications where high viscosity and high functionality are required. Until now, in the running-in operation prior to its use, it has been dealt with by operating in full operation after removing foreign substances that may be spilled in advance, and the polymer used in the running-in process is It is considered to be a factor of yield reduction such as being discarded as it is.

  Further, as a problem in the filter structure to be used, for example, as shown in FIG. 2, members such as a retainer mesh for supporting inner and outer edges obtained by superposing two annular upper and lower annular filter media are joined to each other. In the leaf-shaped filter having the interior, the outflow of the impure foreign matter is easily blocked by the complexity of the structure, and there is the same problem as described above.

  The present invention has been completed by researching these problems, and its purpose is to provide a precision metal for molten polymer that has been cleaned with higher precision including impure foreign matters remaining inside the filter medium, particularly the filter medium on the secondary side of the filter. It is in providing the manufacturing method of a filter.

That is, the invention according to claim 1 of the present invention is
1) A metal filter that is composed of a sintered sintered filter material made of metal and that separates and filters the fluid to be processed between an inner peripheral filtration surface forming an internal filtration chamber and an outer peripheral filtration surface of the outer surface is prepared. Preparation stage to do,
2) A first cleaning step of irradiating ultrasonic vibration from the outer surface side of the filter in the first cleaning liquid to float off impure foreign matters adhering to the sintered filter medium;
3) A plurality of times when the filter after the first cleaning is exposed to the second cleaning liquid by reducing the suction pressure to -80 KPa or less in the filtration direction through a drainage mechanism disposed in a predetermined amount of the second cleaning liquid. A second washing step for discharging and removing impure foreign matters remaining in the filter out of the system by repeated pressure flow due to the waste water treatment of 4), and a drying step for further drying the cleaned filter;
A method for producing a precision metal filter for a molten polymer.

Moreover, the invention which concerns on Claim 2 adjusts the said 2nd washing | cleaning liquid to the capacity | capacitance of the liquid level height of 30 mm or less from the uppermost filtration surface position of the said filter, The invention which concerns on Claim 3 The vacuum suction process is performed in a number of repetitions of 5 to 15 times, and the invention according to claim 4 is characterized in that the second washing step has a processing coefficient (Y) of 4 to 20 according to the following formula: It is the manufacturing method of the said precision metal filter which is what is performed by the range respectively.
Y = aspiration amount (L) × aspiration flow rate (L / min) × repetition processing times (times) / 1000

  Further, the invention according to claim 5 is the filter, wherein the two annular sintered filter media are joined to each other at either the inner edge or the outer edge to form an annular leaf shape. In the invention according to claim 6, the filter-molded product is formed as a cylindrical molded product in which the sintered filter medium extends in a cylindrical shape along the longitudinal axis direction, and the invention according to claim 7 further includes: The sintered filter medium is made of a metal fiber material and / or a metal powder material, and has a filtration guarantee layer having fine pores and a coarser air than the guarantee layer laminated on at least one side of the guarantee layer. It is a manufacturing method of the said precision metal filter characterized by each using the laminated structure of the filtration accuracy of 100 micrometers or less formed by integrally sintering the support layer of a hole.

  According to the invention of claim 1 relating to the method for producing a precision metal filter of the present invention, the molded filter product is subjected to a primary and secondary two-stage cleaning process, and the primary cleaning is performed on the outer surface side. Impurity particles adhering to the surface are suspended by irradiation of ultrasonic vibrations from the filter, and in the secondary cleaning process, the filter chamber of the filter is forced through a predetermined high-pressure flow and at least a part of the filter is exposed from the cleaning liquid. By the pressure flow in which the vacuum suction is repeatedly performed at a predetermined pressure and along the filtration direction, the impure foreign matters existing therein can be surely and effectively discharged, and can be effectively used as a filter product for high cleanliness.

  In the present invention, since the secondary cleaning is exposed from the cleaning liquid by a predetermined forced pressure reduction, the cleaning liquid that tends to remain in the filter can be sucked out at the same time, and the drying process after cleaning can be reduced. is there. Therefore, according to the inventions of claims 2 to 4, the effect is further promoted, and can be widely applied to the filter products of various shapes of claims 5 to 7, and can be widely used.

  It is process drawing explaining the manufacturing process of this invention.   It is a perspective view which shows the cross section about the annular leaf-shaped filter in cross section.   It is a top view which shows an example of the washing | cleaning apparatus explaining a secondary washing | cleaning step.   FIG. 4A is an example of a test result based on an embodiment of the present invention, and FIG. 4A is a diagram showing the relationship between the removal performance of impure foreign matters caused by the number of repeated cleaning processes in the secondary cleaning stage, and FIG. Similarly, the relationship of the removal performance by the relationship of the processing coefficient (Y) is shown respectively.   FIG. 5A is a micrograph showing the distribution state of the discharged and removed impurity particles according to the test results of the examples. FIG. 5A is a state photograph of the discharged impurity particles when the secondary cleaning is repeated 10 times, and FIG. 5B is a reference. As for the filter of only said 1st washing process, the state of the impure foreign matter discharged | emitted is shown.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. The present invention is not necessarily limited to the description thereof, but should be understood based on the scope of the claims and includes the scope of the claims.

FIG. 1 shows an embodiment of the manufacturing process of the present invention.
1) Preparation stage A for preparing the metal filter constituted by a metal porous sintered filter medium;
2) First cleaning in which the filter-molded product is immersed in a first cleaning liquid and irradiated with ultrasonic vibration from the outer surface side, and impure foreign matters adhering to the sintered filter medium of the filter molded product are floated. Stage B,
3) A plurality of times when the filter after the first cleaning is exposed to the second cleaning liquid by reducing the suction pressure to -80 KPa or less in the filtration direction through a drainage mechanism disposed in a predetermined amount of the second cleaning liquid. A second cleaning stage C that discharges and removes impure foreign matters remaining in the filter by repeated pressure flow due to the waste water treatment of 4) and 4) a filter that includes each stage of the drying stage D for further drying the cleaned filter It is a manufacturing method.

  As an embodiment of the metal filter, FIG. 2 shows a perspective view of the leaf-shaped filter molded article 1 with a part thereof cut away. The filter 1 is disposed between porous sintered filter media 2A and 2B made of metal, for example, stainless steel fibers, previously punched into a donut ring shape, and the filtration pressure applied to the filter media is appropriately set. Retaining retainer mesh 2C for supporting, and welding 2D without leakage along the outer edges (or inner edges) of the filter media 2A, 2B, thereby providing a filtration chamber 2E isolated by the filter media in the interior, and an integral leaf A filter product 1 is formed. A hub member 2F having a through hole 2G for discharging the filtration liquid to the outside of the system while supporting the filter medium on the contact surface on the inner edge side (or outer edge side) of the filter medium 2A, 2B. Prepare. A filter using such a fiber-sintered filter medium is widely known, for example, in Japanese Utility Model Publication Nos. 1-23530 and 4-70112.

  In this form, the polymer to be filtered, that is, the fluid to be treated, is filtered by the filter media 2A and 2B along the direction of the arrow A from the outer surface 2a side, as shown in FIG. It flows through the 2F through-hole 2G so as to be supplied outside the system, that is, to the next process. Here, the outer surface 2a side of the filter medium 2 is the upstream primary side, and the filtration chamber 2E side of the back surface is the downstream secondary side.

  In addition to the leaf-shaped filter, the filter 1 is, for example, a cylindrical filter in which the filter medium 2 is simply butt-formed so as to have a cylindrical shape with a predetermined outer diameter, or a pleated shape extending in the axial direction on the filter surface. Various forms such as a pleated tubular pleated filter can be adopted, and the size of the filter can be arbitrarily set according to the filtration device used and its processing capacity. For example, a leaf-shaped filter having an outer diameter of about 50 to 500 mm is often used.

  Further, the configuration of the filter medium 2 can be designed freely and in an optimum range depending on the type, characteristics, and processing conditions of the polymer used. For example, in the case of a highly viscous fluid such as a polyester resin material, the filtering process is performed. In order to suppress the pressure loss at that time as much as possible, a multi-layered filter medium having a multi-layer structure made of various types of filter media is often used.

  As an example, for example, a fine layer 21 that guarantees filtration accuracy made of a sintered nonwoven fabric of fine stainless steel fibers having a fiber diameter of about several to several tens of μm, and a prefilter layer in which coarse pores are formed on both sides thereof In this case, the pores of the filter medium are constructed in the order of coarse pores → fine pores → large pores. Further, if necessary, the filter medium 1 may be made of a known metal filter medium, such as the one composed entirely of the metal fibers or the metal powder (stainless steel powder).

  Therefore, in the case of the filter 1 with the laminated filter medium or the filter medium having an increased filter medium thickness, the fine foreign matters remaining in the filter medium are blocked by, for example, the central fine layer 21 and can be sufficiently removed by a cleaning process from only one direction. I can't expect it. Therefore, in the present invention, the first cleaning treatment on the outer surface side is performed by suspending the impurities particles remaining on the filter medium surface by ultrasonic waves and washing the outer surface side to wash away. By adding a secondary cleaning process that discharges and removes the inner surface, which is the back surface, out of the system by repeated pressure flow accompanying forced vacuum suction of the cleaning fluid, the filter product is made highly clean throughout.

  The primary cleaning process is to clean the entire outer peripheral surface of a predetermined filter product, for example, toward an ultrasonic vibration surface set to oscillate in water, and the vibration cycle is, for example, about 5 to 20 KHz. Done in The fine vibration causes minute friction with the surrounding water over the details of the filter, floats and separates minute impurity particles remaining in the pores, and facilitates discharge thereof. For this reason, the impure foreign matters on the outer surface side of the filter 1 are first removed by running water, for example.

  The filter 1 is attached and set without leakage to the discharge mechanism 11 of the cleaning tank 10 illustrated in FIG. 3 for the next secondary cleaning process. The discharge mechanism 11 further includes a pipe 12 and a flow rate adjusting valve. 13 is connected to a vacuum pump 14 via storage tanks T1 and T2 provided outside the cleaning tank 10. The cleaning liquid S in the cleaning tank 10 can be forcibly discharged by vacuum vacuum suction of the pump 14.

  The filter 1 is attached to the discharge mechanism 11 by, for example, screwing the inner peripheral hub portion 2F of the filter from both sides thereof to prevent leakage, and the cleaning liquid S is set so that it can be drained all at once. The decompression condition is adjusted, for example, so that the filtration chamber 2E of the filter 1 is -80 KPa or less from the atmospheric pressure state. Accordingly, the second cleaning liquid S is sucked from the filtration chamber 2E of the filter 1 under conditions adjusted by a hydraulic pressure gauge (not shown) attached to the valve 13, and passes through the pipe 12 to the tank T1, The filter 1 is stored in the buffer tank T2, and finally, the filter 1 is drained under reduced pressure until it is completely exposed. In the present invention, the waste water treatment is repeated a plurality of times, and such treatment can be automated by computer control.

  The supply processing amount of the second cleaning liquid S is adjusted so that, for example, the set height H to the uppermost filtration surface position of the filter 1 is 30 mm or less. When the depth set height H exceeds 30 mm, the flow of the cleaning liquid is biased, for example, it is easy to concentrate near the central hub of the filter, and it is difficult to obtain a strong discharge on the outer edge side. The result is confirmed. The observation was made by dropping droplets of different color liquid such as ink picking into the suction drain of the cleaning liquid and confirming the outflow state.

  As a result, it has been confirmed that, particularly when the H height is 5 to 20 mm, more preferably 15 mm or less, the filter medium is sucked almost uniformly from the entire surface. How this outflow phenomenon relates to the water depth H has not been fully elucidated, but it is based on hydrodynamic phenomenology caused by the difference in water pressure depending on the water depth and the direction of the liquid flow. Guessed.

  Therefore, the area ratio between the width of the cleaning layer 10 and the projected area seen in the thickness direction of the filter 1 to be processed is 3 times or more, preferably 4 so as to accommodate the supply amount necessary for cleaning in the depth range. It is preferable to use a relatively large bathtub so as to be twice or more. By doing so, even when the cleaning liquid S is sucked under reduced pressure at a high pressure of −80 KPa or less, there is no sudden drop in the level of the cleaning liquid, and the entire surface of the filter can be effectively discharged, and the remaining impure foreign matter Can be effectively discharged.

  The forced suction accompanying the pressure reduction simultaneously discharges a considerable amount of the cleaning liquid remaining in the filter 1, so that the subsequent drying process can be shortened and problems such as filter medium fraying can be reduced. As the first cleaning liquid, for example, a clean non-corrosive fluid such as filtered pure water or alcohol is used for the cleaning liquid.

  In this way, when the filter-1 in the cleaning tank 10 is exposed and the discharge of the cleaning liquid S is completed, the valve 13 is closed, and this is set as one cycle, and the cleaning process is repeated a plurality of times. Basically, it should be discharged so that it is clean. The preferred number of repetitions is 5 to 15 times. As an example, the results obtained in Examples described later can be seen in FIGS. 4A and 4B.

  FIG. 4A shows the number of times of cleaning in the second cleaning stage and the change in the residual amount of discharged foreign matter, and the suction pressure is -90 KPa (test A) and -80 KPa (test B) under two conditions. , Each shows a change in the state of discharged foreign matter with the number of repetitions. In any situation, it can be seen that the effect is almost halved by repeating about 5 times, and that the change is relatively unchanged after repeating about 15 times or more.

    The effect can be shown by setting the treatment coefficient (Y) according to the following formula in the second cleaning stage to be in the range of 4-20. The coefficient (Y) is based on experiments, and when the value is less than 4, it is difficult to obtain sufficient outflow of impurity particles. It is adjusted to 5-18.

    Y = aspiration amount (L) × aspiration flow rate (L / min) × repetition processing times (times) / 1000

  FIG. 4B shows the relationship with the outflow effect of the foreign matter accompanying the change in the processing coefficient (Y). In test C, the Y value is changed by changing only the suction amount of the cleaning liquid, and test D is the suction flow rate. The same tendency as in FIG. 4A is observed.

  The filter 1 which has finished such a cleaning process is removed from the holding mechanism 11 and the next drying process is performed. The drying treatment can be easily adopted, for example, by heating and heating at a temperature of, for example, about 100 to 300 ° C. for a predetermined time in the same manner as a normal metal product. Finally, for example, dust checks, bubble points, and other quality items are measured and inspected and commercialized as a filter product.

  The invention is further illustrated by the following examples.

In this embodiment, the filter is a 12-inch outer diameter leaf filter so that the polymer fluid is heated to a temperature of about 220 to 260 ° C. as a fluid to be treated and is suitable for a filtration apparatus for a polymer in a molten state. Will be explained.
<< Process Stage A >>

    The filter uses a stainless steel fiber web having an average fiber diameter of 5 μm, pressurized to a thickness of 0.8 mm, and a fine sintered layer having a pore diameter of 5 μm and a porosity of 72% is used as an accuracy guarantee layer, Furthermore, it is composed of a laminated filter medium in which a total of two layers of structures with a total thickness of 3 mm are placed on the downstream side of the support layer made of stainless steel atomized particles with a particle size of less than 300 μm and sintered together. The pores formed in the thickness direction of the filter medium are fine and coarse.

And two sheets for this sintered filter medium are prepared, each of which is punched into an annular shape having the above outer diameter, and the outer periphery is welded over the entire length, and between the filter media, Further, by incorporating a 5 # coarse mesh for the retainer, a leaf filter having an outer diameter of 300 mm × thickness of 15 mm was obtained with the corresponding portion as a filtration chamber.
<< Process Stage B >>

    Next, the obtained filter molded article is immersed in a cleaning liquid obtained by filtering tap water, and an ultrasonic wave that oscillates at a fixed frequency of 1200 W and 15 kHz toward the outer surface of the filter upstream of the filter in the liquid. By applying vibration, the adhering and remaining impurity particles contained in the filter medium were floated and separated, and residual impurities on the outer surface (primary surface side) were washed away.

The ultrasonic transducer used at this time was a longitudinal shape having a plane of width 25 mm × length 165 mm, and the entire surface of the filter was adjusted while adjusting this surface and the filtration surface of the filter to be parallel and at a constant distance. Was carried out while rotating and rotating sequentially so as to be washed. The processing time required for this primary cleaning is 6 minutes / sheet.
<< Process stage C >>

  After the treatment, the filter is taken out and attached to a discharge mechanism in a cleaning tank having a predetermined volume of 700 × 500 mm and a height of 200 mm as shown in FIG. 3, and the entire filter is placed in the tank. The second cleaning liquid (filtered water) was filled until the liquid was completely immersed, and the flow rate was adjusted so that the amount was 10 mm from the upper surface of the filter. The ratio of the open area of the tank to the projected area of the filter is about 5 times.

  Thereafter, the filter chamber of the filter is forcibly depressurized from the atmospheric pressure state to -90 KPa and -80 KPa from the primary side to the secondary side through the discharge mechanism, and the entire filter is sucked by the suction. The valve was opened so that the second cleaning liquid was discharged until it was exposed.

The impurity particles inside the filter that have flowed out due to the outflow are provided with a bypass in the middle of the discharge pipe 12, and a particle distribution per unit time of the particles captured by the membrane sheet by setting a membrane sheet in the passage The amount was obtained by determining the area ratio. After the membrane sheet was taken out and dried, each of three visual fields arbitrarily selected by a microscope was observed under magnification, and the total area of foreign particles captured within the visual field area was measured. The area ratio divided by the visual field area is averaged.
The change in the area ratio is shown in FIG. 4A.

  As described above, this result can be greatly reduced to 90% or more by repeating the secondary cleaning 10 times or more, and especially the reduction rate between the repetitions of the secondary cleaning of about 5 times is large. A decrease is observed. FIG. 5 shows the impurity particles discharged and removed in this cleaning test, FIG. 5A is a photomicrograph when the secondary cleaning is repeated 10 times, and FIG. 5B is a case where only the primary cleaning is performed. It is the state of the trapped foreign matter. Also from this state, the effect of the secondary cleaning of the present application is confirmed.

Further, when these captured particles were examined by X-ray analysis, in particular, a larger amount of impurities such as cut pieces, chromium oxide, oxide scale, etc. were confirmed, and these particles were cut, heated, and washed at the production stage of the filter. It was confirmed that
<< Process Stage D >>

  The filter molded product thus sucked and reduced in pressure was less dry due to the overall dehydration and was almost in a dry state, but for further certainty, it was placed in a drying oven at a temperature of 200 ° C. for 30 minutes. A drying treatment was performed.

The filter was further examined for the influence of the processing coefficient (Y) based on the following formula.
The coefficient Y is determined by the following equation: Y = aspiration amount (L) × aspiration flow rate (L / min) according to the suction amount (L) of the cleaning liquid, the suction flow rate (L / min), and the number of repetitions (times) in the second cleaning stage. ) × number of times of repeated processing (times) / 1000, and the result is shown in FIG.

  Next, instead of the leaf filter used in the first embodiment, an example using a cylindrical filter described in detail below will be described.

  The cylindrical filter uses a laminated filter medium in which stainless steel fibers and powder are laminated in the same manner as described above. The cylindrical filter is curved to an outer diameter of 60 mm and welded together to form a cylindrical shape. A sealing cap was disposed, and an annular cap metal fitting having an opening for circulation was brought into contact with the other lower end side, and a cylindrical filter having a filtration chamber therein was formed by welding. The filter has an outer diameter of 60 mm and a length of 150 mm.

  In the same manner as in Example 1, the molded filter was immersed in water and applied with ultrasonic waves from the outer surface side to clean the outer surface side, and the H in the separate cleaning tank. Is set at a water depth of 15 mm, and the secondary cleaning process of forcibly suctioning the cleaning liquid 10L from the outer surface side toward the inner surface side under the reduced pressure (condition -90 KPa) is repeated 8 times, and the repeated pressure flow is performed in the same manner as described above. The impure foreign matters that flowed out by the above were observed with a microscope, and a cleaned filter product of about 1% in total was obtained. The processing coefficient (Y) was in the range of 8-10.

    As described above, the present invention is based on a manufacturing method that removes impure foreign matter inherent to a metal filter remaining inside a filter, which has not been sufficiently handled by two types of cleaning methods, and is particularly highly viscous and highly functional. It is effective as a filter for molten polymer.

DESCRIPTION OF SYMBOLS 1 Metal filter 2A, 2B Sintered filter medium 2E Filtration chamber 10 Secondary washing tank 11 Discharge mechanism S Second washing liquid

Claims (7)

1) A metal filter that is composed of a sintered sintered filter material made of metal and that separates and filters the fluid to be processed between an inner peripheral filtration surface forming an internal filtration chamber and an outer peripheral filtration surface of the outer surface is prepared. Preparation stage to do,
2) A first cleaning step of irradiating ultrasonic vibration from the outer surface side of the filter in the first cleaning liquid to float off impure foreign matters adhering to the sintered filter medium;
3) A plurality of times when the filter after the first cleaning is exposed to the second cleaning liquid by reducing the suction pressure to -80 KPa or less in the filtration direction through a drainage mechanism disposed in a predetermined amount of the second cleaning liquid. A second washing step for discharging and removing impure foreign matters remaining in the filter out of the system by repeated pressure flow due to the waste water treatment of 4), and a drying step for further drying the cleaned filter;
A method for producing a precision metal filter for a molten polymer.   2. The method for producing the precision metal filter according to claim 1, wherein the second cleaning liquid is adjusted to a capacity having a liquid level height of 30 mm or less from an uppermost filtration surface position of the filter.   The method for producing the precision metal filter according to claim 1 or 2, wherein the vacuum suction treatment is repeatedly performed 5 to 15 times. The manufacturing method of the precision metal filter for molten polymers of Claim 4 whose said 2nd washing | cleaning step is performed in the range whose processing coefficient (Y) by the following formula is 4-20.
Y = aspiration amount (L) × aspiration flow rate (L / min) × repetition processing times (times) / 1000   5. The filter according to claim 1, wherein the two annular sintered filter media are joined to each other at either the inner edge or the outer edge to form an annular leaf shape. The manufacturing method of the said precision metal filter in any one.   The filter according to any one of claims 1 to 4, wherein the filter is formed as a cylindrical molded product in which the sintered filter medium extends in a cylindrical shape along a longitudinal axis direction thereof. Production method.   The sintered filter medium is made of a metal fiber material and / or a metal powder material, and has a filtration guarantee layer having fine pores, and pores coarser than the guarantee layer laminated on at least one side of the guarantee layer. The method for producing a precision metal filter according to any one of claims 1 to 6, which is a laminated structure having a filtration accuracy of 100 µm or less formed by integrally sintering the support layer.