JP2002326008A - Foamed body-used filter and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filter for efficiently collecting the substance to be collected by deciding so that the particle size of a bubble forming material or the like to be used when the filter is manufactured by using a foamed body obtained by an extraction method is matched to the size or the like of the substance to be collected by the filter to be manufactured finally, and to provide a method for manufacturing the filter. SOLUTION: This filter is manufactured by preparing a compact by mixing at least one thermoplastic resin 12, a water-soluble bubble forming material consisting of a granular material whose particle size is set in the prescribed range by classification and which is stable thermally at the hot melting temperature of the resin 12 to keep its shape and a water-soluble macromolecular compound consisting of a granular material whose particle size is set to be almost similar to that of the water-soluble bubble forming material by classification and which functions as a lubricant when heated and by extracting/removing the water-soluble bubble forming material and the water-soluble macromolecular compound from the prepared compact by using water, so that bubbles 16 of the size similar to the particle size of the water-soluble bubble forming material and the water-soluble macromolecular compound are formed in the filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter, and more particularly, to controlling a particle size of a cell forming material used in producing a filter using a foam obtained by an extraction method within a predetermined range. Accordingly, the present invention relates to a filter capable of reducing the amount of impurities and shrinkage when obtaining the filter and improving the strength, and a method capable of suitably manufacturing the filter.

[0002]

2. Description of the Related Art Generally, a filter for collecting various substances according to the purpose has a filter effective diameter corresponding to the size of the substance to be collected, and in ordinary use, passes through the filter. There is a demand for physical properties that achieve low pressure loss so as not to obstruct the flow of fluid such as air.

However, if the effective diameter of the filter does not match the size of the object to be collected, it becomes difficult to efficiently collect the object to be collected or the pressure loss becomes too high. In either case, a suitable effect cannot be exhibited over a long period of time.

[0004] The pressure loss is also one of the important factors in use, and if the pressure loss is large,
While the collection efficiency of the collected matter such as dust increases, clogging is likely to occur, that is, frequent maintenance or the like needs to be performed, which poses a serious problem in actual use. This pressure loss has a large effect on the effective diameter of the filter, but on the other hand, if the internal structure of the filter used is not in a communicating state, the pressure loss is high regardless of the size of the effective diameter of the filter. It is not suitable for filter applications. That is, when considering the physical properties of the filter, it can be seen that the filter effective diameter and the pressure loss are contradictory and are important physical property values.

In view of these points, it is necessary to manufacture a filter using a substance having a structure that can control the effective diameter of the filter arbitrarily and does not increase the pressure loss due to physical properties other than the effective diameter of the filter. desirable. As one of such substances, there is a foam having so-called three-dimensionally connected bubbles, and the diameter of the bubbles formed inside the foam is the filter effective diameter. Generally, as a method for producing the foam, a foaming method is used in which a foaming material is mixed into a main material and bubbles are formed by a gas such as nitrogen generated from the foaming material, or a foaming material is previously mixed in the main material. -An extraction method is known in which the foam-forming material is removed after dispersion to form bubbles.

However, the foaming method has an advantage that various main materials can be used, but it is difficult to control the uniformity of the generated bubble diameter, and it is difficult to form bubbles having a small diameter of several tens μm. . On the other hand, in the case of the extraction method, the diameter and the like of the formed bubble depend on the type of the bubble material to be used. Therefore, there is an advantage that the uniformity and size described above can be arbitrarily controlled.

[0007]

However, when a foam is obtained by the above-mentioned extraction method, it is important to obtain a three-dimensional open-cell structure, in which the degree of mixing and the ease of extraction, ie, the three-dimensional open-cell structure, are generally obtained for the foam-forming material to be mixed. No attention has been paid to the size distribution of the cell forming material.

In the above-mentioned extraction method, if the size of the foam forming material used is not within a certain range, it is considered that extraction is impossible. It is conceivable that the pore-forming material remains without being sufficiently extracted and removed from the main material forming the foam, and as a result, it greatly affects the formation of the skeleton and the like. Specifically, the uniform skeleton is not formed, the strength is reduced, the residual foam forming material affects the physical properties and chemical properties of the foam obtained, and the open cell rate is reduced,
Problems such as an increase in shrinkage are pointed out.

[0009]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-mentioned problem that appears when a filter is obtained from a foam, and has been proposed to suitably solve the problem. When producing a filter, the particle size of the bubble forming material or the like to be used is determined by the size of the collected object, which can be achieved by the finally obtained filter, so that the collected object can be efficiently used. It is an object of the present invention to provide a filter that can be trapped selectively and a method for manufacturing the filter. Further, by setting the range of the particle size of the bubble forming material or the like within a predetermined range, extraction and removal of the bubble forming material is facilitated, and the amount of impurities and shrinkage when a filter is obtained are reduced, and the strength is improved. An object of the present invention is to provide a filter that can be made to work and a method for manufacturing the filter.

[0010]

In order to overcome the above-mentioned problems and achieve the intended object, a filter according to the present invention has at least one kind of thermoplastic resin and a particle size of the thermoplastic resin set within a predetermined range by classification. A water-soluble bubble-forming material made of a granular material that is thermally stable and can maintain its shape at the heat melting temperature of the thermoplastic resin, and the particle size of which is approximately the same as the particle size of the water-soluble bubble-forming material by classification. The water-soluble bubble-forming material and the polymer compound are extracted and removed with water from a molded product obtained by heating and mixing with a water-soluble polymer compound, which is set in the same range and also functions as a lubricant, also consisting of a granular material. so,
It has a three-dimensional communication bubble structure, and the range of the particle size is set to a value that can improve the extraction and removal rate of the water-soluble substance, the communication rate and the strength of the obtained filter.

[0011] In order to overcome the above problems and achieve the intended object, a filter according to another invention of the present application has at least one kind of thermoplastic resin and the particle size thereof is set within a predetermined range by classification. From a molded body obtained by heating and mixing a water-soluble bubble-forming material made of a granular material capable of maintaining a shape that is thermally stable at the heat melting temperature of a plastic resin and a water-soluble polymer compound that acts as a lubricant, The water-soluble bubble-forming material and the polymer compound are extracted and removed with water to form a three-dimensional open-cell structure. The range of the particle size is the extraction / removal rate of the water-soluble bubble-forming material and the filter obtained. Are set to values that can improve the communication rate and strength of

[0012] In order to overcome the above-mentioned problems and achieve the intended object, a method for producing a foam according to yet another aspect of the present invention comprises a method for producing at least one type of thermoplastic resin, the particle size of which is determined by classification. A water-soluble bubble-forming material consisting of a granular material which is set in a range and is thermally stable and can maintain its shape at the heat-melting temperature of the thermoplastic resin, and particles of the water-soluble bubble-forming material whose particle size is classified by classification. After being mixed with a water-soluble polymer compound, which is set in substantially the same range as the dimensions and also functions as a lubricating material, and is formed of a granular material, and the resulting mixture is formed into a predetermined shape, the molded body is formed. By contacting with water to extract and remove the water-soluble bubble-forming material and the polymer compound, a three-dimensional communication bubble structure is formed, and the extraction and removal rate of the water-soluble substance, the communication rate and strength of the obtained filter are reduced. Improved Characterized in that so as to produce the filter.

[0013] In order to overcome the above-mentioned problems and achieve the intended object, a method for producing a foam according to yet another aspect of the present invention comprises a method for producing at least one type of thermoplastic resin and the particle size of the thermoplastic resin by classification. A range is set, and a water-soluble bubble-forming material composed of a granular material that is thermally stable and can maintain a shape at a heat melting temperature of the thermoplastic resin and a water-soluble polymer compound that acts as a lubricant are heated. After mixing under the condition, the obtained mixture is molded into a predetermined shape, and the molded body is brought into contact with water to extract and remove the water-soluble cell-forming material and the polymer compound, thereby forming a three-dimensional communication cell structure. And a filter in which the extraction and removal rate of the water-soluble bubble-forming material, the communication rate and the strength of the obtained filter are improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a filter according to the present invention will be described below with reference to the accompanying drawings by way of preferred embodiments. The inventor of the present application controls the particle size range of a cell forming material or the like that forms cells when producing a foam by an extraction method, thereby efficiently collecting trapped objects and reducing pressure loss. It has been found that a filter capable of improving the degree of communication and the strength can be obtained by suppressing as much as possible and improving the rate of extraction and removal of the bubble forming material at the time of extraction.

As shown in FIG. 1, the filter 10 is made of a thermoplastic resin 12 as a main component, and fine bubbles 16 formed by extracting and removing a bubble forming material and a polymer compound are three-dimensionally formed. , A so-called three-dimensional communication bubble structure.

As the thermoplastic resin 12, TPE is used.
(Polyester type, polyether type, polyether polyester type, styrene type, polyamide type, etc.), olefin resin (PE (LD-PE, HD-PE, LL-PE, α
Any resin that can be melted by heating can be used, such as olefinated PE), PP and TPO), TPU, polyamide, polyimide or polyacetal. The use of a plurality of thermoplastic resins having similar melting points can also be used in consideration of physical properties and the like.

As the foam-forming material, any substance can be used as long as it is water-soluble and is thermally stable and can maintain its shape even when the thermoplastic resin 12 is thermally melted. For example, as inorganic substances, NaCl, KCl, CaC
l ₂ , NH ₄ Cl, NaNO ₃ , NaNO _{2 and the} like. As organic substances, TME (trimethylolethane),
Examples include trimethylolpropane, trimethylolbutane, sucrose, soluble starch, sorbitol, glycine or the sodium salt of each organic acid (malic acid, citric acid, glutamic acid or succinic acid). At the time of use, a large number of granular materials that can be subjected to a predetermined classification are used.

Examples of the high molecular compound include polyethylene glycol, polyethylene glycol diacrylate,
Polyethylene glycol dioleate, polyethylene glycol derivatives such as polyethylene glycol diacetate, and other stable substances that dissolve in water and do not thermally decompose when the thermoplastic resin 12 is thermally melted. Any compound that functions to lower the viscosity can be used. Particularly, polyethylene glycol can be suitably used because it has a high melt flow and high water solubility. Further, when an organic substance is selected as the bubble-forming material, an effect of promoting the extraction and removal of the bubble-forming material has been confirmed. Further, when the molding is carried out by an extrusion molding method, the molecular weight of the polyethylene glycol is 2,000 to 30,000, preferably 5.0 to 5,000.
00 to 25,000, more preferably 15,000 to 2
It has been found that a range of 5,000 is suitable. At the time of use, a large number of granules that can be classified as required are used in the same manner as in the case of the bubble forming material.

The above-mentioned polymer compound acts as a lubricating material, and when heated and mixed, becomes amorphous and becomes in a fluid state, thereby exhibiting its effect effectively. Therefore, depending on the type of the polymer compound, there may be a case where the control of the particle size itself is not necessary. In such a case, the production cost can be reduced by eliminating the trouble of controlling the particle size.
However, even in the case of the irregular shape as described above, a certain effect can be expected to reduce the total amount of the bubble forming material which has a floating island structure and is difficult to extract and remove for the reason described later (see [0030]). In addition, when a substance that does not cause a large change in state due to large melting at a temperature at which the thermoplastic resin 12 is melted by heat and uses a substance that exhibits a sufficient lubricating effect is used as the polymer compound, the bubble-forming material In this case, the same control of the particle size as described above is required, which has a great significance.

The particle size of the bubble-forming material and the high molecular compound is the size of the bubbles 16 formed in the filter 10, and the size of the bubbles 16 is determined by the size of the material to be collected. It is determined depending on the pressure and the pressure loss. Specifically, the upper limit of the bubbles 16, that is, the upper limit of the particle size is determined by the size of the trapped object to be collected, and the pressure loss determines the lower limit of the bubbles 16, that is, the lower limit of the particle size. If the value is too small, the pressure loss becomes excessive and the filter becomes unsuitable for use in a filter.

The mixing ratio of the thermoplastic resin 12 with the cell forming material and the polymer compound (water-soluble substance) is vol.
% Is preferably in the range of 10:90 to 40:60. If the ratio of the thermoplastic resin 12 is less than 10 vol%, the filter cannot maintain its shape when extracting and removing the water-soluble substance, and will collapse. On the other hand, the thermoplastic resin 12
When the proportion of the water-soluble substance is less than 60 vol%, a sufficient number of bubbles are not formed, and as a result, a sufficient three-dimensional communicating cell structure is not formed, and the The pressure loss worsens as the temperature decreases. In particular, the mixing ratio of the thermoplastic resin 12 is preferably in the range of 12 to 35 vol%.

The mixing ratio of the cell forming material and the polymer compound is set in the range of 45:55 to 95: 5 by vol. When the amount of the cell forming material is less than 45 vol%, a three-dimensionally connected foamed structure cannot be obtained, and 9
If it exceeds 5% by volume, the extraction ratio of the water-soluble substance is reduced, and a sufficient air bubble rate, that is, communication cannot be obtained. In particular, the mixing ratio of the cell forming material and the polymer compound is preferably in the range of 65:35 to 88:12 in vol%.

When the mixing ratio of the thermoplastic resin, the foam-forming material and the high molecular compound is set in the above-mentioned range, a molded article obtained by molding the mixture is immersed in water.
The cell forming material and the polymer compound can be easily and sufficiently extracted and removed. That is, it is possible to obtain a filter having the three-dimensional communicating cell structure with the thermoplastic resin as a main material, capable of efficiently collecting trapped substances, having uniformity and strength.

In order to produce the filter according to the present invention, as shown in FIG. 2, first, a cell forming material for forming cells, or the cell forming material and the polymer compound are classified to a particle size in a required range. The classified foam-forming material or the foam-forming material and the high-molecular compound, and the thermoplastic resin forming the skeleton are mixed and kneaded using a predetermined device to form a heated mixture, which is used as it is or is subjected to extrusion molding. The foamed material and the polymer compound are extracted and removed by immersing the molded body formed into a predetermined shape by performing injection molding or the like into water or warm water at a predetermined temperature, and fine bubbles are three-dimensionally communicated. This is to obtain a filter having a structure. When the viscosity at the time of mixing is high and mixing is difficult, pre-mixing may be performed prior to the above-described mixing.

The classification of the cell forming material or the cell forming material and the high molecular compound depends on the particle size to be classified, but it is generally sieved and classified by a sieve having an upper limit of the required particle size. And then perform air classification with the lower limit of the required particle size,
This is to obtain a particle size product within a set range. Basically, sieving classification has higher classification efficiency per hour than air classification, and there is concern about clogging with fine particle size, so sieving the upper limit of particle size by sieving in a short time and efficiency without clogging Since efficient classification can be performed, it is more efficient to perform the classification before the lower limit of the air classification.

The mixing and kneading of the above-mentioned thermoplastic resin, bubble-forming material and polymer compound may be carried out by a single-screw or twin-screw extruder, kneader, co-kneader, Banbury mixer, Henschel mixer or rotor mixer or other kneading. Those capable of uniformly dispersing a functional substance such as a machine are suitably used.
For this kneading, no special device is required, and the kneading speed and the like are not limited. The temperature at the time of kneading is appropriately set depending on the thermal melting point of the thermoplastic resin or the like to be used.In the present invention, the bubble forming material and the polymer compound are melted or sublimated at the thermal melting point of the thermoplastic resin. Because there is no, any temperature can be set.

The kneading time for mixing and kneading the thermoplastic resin, the foam-forming material and the high molecular compound depends on the physical properties of the various mixtures. The mixture only needs to be sufficiently mixed and kneaded. About 40 minutes is enough.
At this time, care must be taken because excessively long kneading causes deterioration of the physical properties of the thermoplastic resin forming the skeleton of the foam. The kneaded raw material can be physically formed into a desired shape by extrusion, injection, pressing, a roller, or the like, but particularly, extrusion by high mass productivity or injection molding capable of forming a complicated shape is preferable.

The molded article formed into a required shape by mixing the respective components is prepared by mixing the foam-forming material and the polymer compound in water as a solvent for a predetermined time (for example, 12 to 24 hours, the shape and thickness of the molded article). It is extracted and removed by immersion. The immersion time is shortened compared to an uncontrolled filter by controlling the particle size of the cell forming material and the polymer compound to be extracted (the reason is described in [0030]). .

The immersion at this time may be any method, but extraction and removal by immersion in water in which the whole molded body is brought into contact with water is preferred. The temperature of the water used at this time is not particularly limited and may be about room temperature. For efficient removal of the water-soluble substances, hot water of 15 to 60 ° C. is used. May be.

As for the extraction and removal of the bubble forming material and the like by the extraction, the structure becomes hexagonal close-packed when the thermoplastic resin and the bubble forming material and the like are mixed. The numerical range of particle size is 0.16
As shown in FIG. 3, the crystal structure (see FIG. 3 (a)) cannot be extracted, that is, the floating island structure can be obtained by setting the size within a range of × n to 6.45 × n (where n is a natural number). It is considered that the bubble forming material 14 and the like no longer exist in the thermoplastic resin 12 (see FIG. 3B). Therefore, when setting the bubble diameter of the filter, it is desirable that the range of the bubble diameter falls within the range of the numerical value described above. This makes it possible to quantitatively and temporally efficiently extract.

Examples of applications where the filter according to the present invention is used include an ordinary collection filter for efficiently collecting an object to be collected. The fluid flowing through the filter may be any of various gases and various liquids. It is suitable for use in applications for collecting particularly fine objects such as a filter for a clean room used at room temperature and an ink strainer for an ink jet.

[0032]

[Experimental Example] An experimental example of the filter according to the present invention will be described below. This filter is prepared by mixing a thermoplastic resin, a foam-forming material, and a polymer compound, which will be described later, and subjecting the obtained mixture to a temperature of 100 ° C. for 60 seconds using a general-purpose hot press.
Under the conditions of ec, width 150 mm, length 150 mm, thickness 2 m
After obtaining a test piece of m, it is obtained by subjecting it to an extraction treatment with water for 24 hours and a drying treatment with a hot air drier. In the experimental example, the particle size of the cell forming material and the polymer compound was controlled to 100 to 250 μm by air classification, and in the comparative example, the particle size was not controlled. And about the obtained two test pieces, each physical property required for a foam by visual observation or using various measuring instruments, an extraction rate (%), a shrinkage rate (%), and a tensile strength (kg /
cm ² ), C hardness (C), liquid permeation liquid velocity (sec / 10 cc (details will be described later)) and physical properties corresponding to the pressure loss before collecting the collected matter (carbon beads). ) Collection rate (%)
Was observed and measured respectively.

With respect to the pressure loss, the liquid permeation speed (sec / 10 cc) was measured using a test apparatus 50 shown in FIG. The test apparatus 50 basically includes a cylindrical tube 52 having an inner diameter of 5 mm and a φ5 ×
It consists of a filter 54 processed into a 3 mm cylindrical shape, and 10 cc of ethanol is passed through it from above,
It measures the time required for passage. In this case, the higher the pressure loss, the longer the passage time.

[0034]

[Table 1]

The components and equipment used in the experimental examples and comparative examples are as follows. -Substances and mixing ratios used in Experimental Examples and Comparative Examples Thermoplastic resin: General-purpose polyolefin resin; 15 vol% Bubble-forming material: General-purpose salt; 60 vol% Polymer compound: General-purpose polyethylene glycol; 25 vol%-Equipment used Extrusion Kibo Lab Plast Mill (Toyo Seiki)

(Results) As shown in Table 1, the contraction rate of the obtained filter was about 7% by volume in the comparative example.
In the experimental example, the tensile strength was improved to 3%, and the tensile strength was improved by about 30% to 1.3 when the comparative example was set to 1, and it was confirmed that the C hardness was 15 and 7 and became more flexible. As for the extraction ratio, a large improvement of 95% in the comparative example was confirmed to 99%. Furthermore, the collection rate of collected objects (50% → 70%)
Regarding the immersion liquid speed (6 sec.fwdarw.3.5 sec.), The filter according to the experimental example was better in all numerical values.

[0037]

As described above, according to the filter and the method of manufacturing the same according to the present invention, air bubbles determined by the pressure loss to be achieved by the finally obtained filter, the size of the trapped object, etc. By classifying and controlling the diameter of the bubble-forming material or the like, it is possible to obtain a filter capable of achieving good flowability and a high collection rate of the trapped material. In addition, by controlling the bubble forming material or the like so as to be in an extractable state without taking a floating island structure, by reducing the amount of the bubble forming material or the like remaining as impurities in the obtained filter, A filter that suppresses shrinkage and improves communication and strength can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a filter according to a preferred embodiment of the present invention.

FIG. 2 is a process chart showing a method for manufacturing a filter according to an example.

FIG. 3 shows the crystal structure of the foam of the filter
FIG. 3 (a) and a schematic diagram showing an actual internal structure (FIG. 3 (b)).

FIG. 4 is a schematic diagram of a test apparatus for measuring a liquid permeation liquid velocity according to an experimental example.

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Claims (20)

[Claims] 1. A water comprising at least one kind of thermoplastic resin and a particle whose particle size is set within a predetermined range by classification, and which is thermally stable and can maintain its shape at the heat melting temperature of the thermoplastic resin. Heat-mixing of the soluble bubble-forming material and a water-soluble polymer compound having the same particle size as that of the water-soluble bubble-forming material whose particle size is set to be substantially the same as the particle size of the water-soluble bubble-forming material by classification. The water-soluble cell-forming material and the polymer compound are extracted and removed with water from the molded article according to the above, to form a three-dimensional communicating cell structure, and the particle size range is the extraction and removal rate of the water-soluble substance. A filter that is set to a value that can improve the communication rate and strength of the obtained filter. 2. The filter according to claim 1, wherein the upper limit of the particle size of the water-soluble bubble-forming material and the polymer compound depends on the size of an object to be collected by the obtained filter. 3. The filter according to claim 1, wherein the lower limit of the particle size of the water-soluble bubble-forming material and the polymer compound depends on the pressure loss generated by the obtained filter. 4. The filter according to claim 1, wherein the water-soluble bubble forming material is an inorganic substance. 5. The filter according to claim 1, wherein the water-soluble bubble forming material is trimethylolethane. 6. The filter according to claim 1, wherein the water-soluble polymer compound is polyethylene glycol. 7. Water comprising at least one kind of thermoplastic resin, and a granular material whose particle size is set within a predetermined range by classification, and which is thermally stable and can maintain its shape at the heat melting temperature of the thermoplastic resin. The water-soluble bubble-forming material and the polymer compound are extracted and removed with water from the molded body obtained by heating and mixing the soluble bubble-forming material and the water-soluble polymer compound acting as a lubricant, thereby providing a three-dimensional structure. A filter having an open-cell structure, wherein the range of the particle size is set to a value that can improve the extraction and removal rate of the water-soluble bubble-forming material, the open rate and the strength of the obtained filter. 8. The filter according to claim 7, wherein the upper limit of the particle size of the water-soluble bubble-forming material and the polymer compound depends on the size of an object to be collected by the obtained filter. 9. The filter according to claim 7, wherein the lower limit of the particle size of the water-soluble bubble-forming material and the polymer compound depends on the pressure loss developed by the obtained filter. 10. The filter according to claim 7, wherein the water-soluble bubble-forming material is an inorganic substance. 11. The filter according to claim 7, wherein the water-soluble bubble forming material is trimethylolethane. 12. The filter according to claim 7, wherein the water-soluble polymer compound is polyethylene glycol. 13. At least one thermoplastic resin,
The particle size is set to a predetermined range by classification, a water-soluble bubble-forming material composed of a granular material that is thermally stable and can maintain its shape at the heat melting temperature of the thermoplastic resin, and the particle size is determined by classification. The particle size of the water-soluble bubble-forming material is set to be substantially the same as that of the water-soluble bubble-forming material. After that, the molded body is brought into contact with water to extract and remove the water-soluble bubble-forming material and the high molecular compound, thereby forming a three-dimensional communicating cell structure and obtaining an extraction and removal rate of a water-soluble substance. A method of manufacturing a filter, characterized in that a filter having an improved communication rate and strength is manufactured. 14. When the classification diameter of the water-soluble bubble-forming material and the polymer compound is 40 μm or more, the sieving classification is performed,
14. The method for producing a filter according to claim 13, wherein air classification is used when the diameter is less than 40 µm. 15. The method according to claim 13, wherein the classification is performed by air classification. 16. The temperature of water used for extraction and removal of the water-soluble bubble-forming material and the polymer compound is 15 to 6.
The method for producing a filter according to claim 13, wherein the temperature is 0 ° C. 17. 17. At least one thermoplastic resin,
The particle size is set to a predetermined range by classification, and a water-soluble bubble-forming material composed of a granular material that is thermally stable and can maintain a shape at the heat melting temperature of the thermoplastic resin, and a water-soluble material that acts as a lubricant. The resultant mixture is molded into a predetermined shape, and the molded body is brought into contact with water to extract and remove the water-soluble bubble-forming material and the polymeric compound. This makes it possible to form a three-dimensional communicating cell structure and extract and remove water-soluble cell forming material,
A method for manufacturing a filter, characterized in that a filter having an improved communication rate and strength is obtained. 18. The classifying diameter of the water-soluble bubble forming material is 4
18. The method for producing a filter according to claim 17, wherein a sieve classification is used when it is 0 µm or more, and an air classification is used when it is less than 40 µm. 19. The method according to claim 17, wherein the classification is performed by air classification. 20. The temperature of water used for extraction and removal of the water-soluble bubble-forming material and the polymer compound is 15 to 6;
The method for producing a filter according to any one of claims 17 to 19, wherein the temperature is 0 ° C.