JP2012139624A - Crystalline polymer microporous film, method of manufacturing the same, and filtration filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crystalline polymer microporous film in which a layer with a different function can be provided by using only a material with a molecular structure of a single variety, a minute pore diameter is possessed, a fine particle of tens of nanometer size can be efficiently caught, and which is high flux, and also to provide a method of manufacturing the same, and a filtration filter.SOLUTION: The method of manufacturing a crystalline polymer microporous film includes: a first paste preparation process which prepares a first paste including a crystallizable polymer of unheating; a second paste preparation process which prepares a second paste including a heated crystallizable polymer in a condition that a ratio (M/M) of a maximum value (M) of a heat absorption peak in a DSC chart of the crystallizable polymer of unheating to a maximum value (M) of the heat absorption peak in the DSC chart of a heat treated crystallizable polymer becomes 0.5-0.95; a preliminary laminate formation process; a laminate formation process; a symmetry heating process; and a stretch process in this order.

Description

  The present invention relates to a crystalline polymer microporous membrane, a method for producing the same, and a filter for filtration.

Microporous membranes have been known for a long time and are widely used in filtration filters and the like. Examples of such a microporous membrane include those using cellulose ester as a raw material (for example, see Patent Document 1), those using aliphatic polyamide as a raw material (for example, see Patent Document 2), and polyfluorocarbon as a raw material. (For example, refer to Patent Document 3), and those using polypropylene as a raw material (for example, refer to Patent Document 4).
These microporous membranes are used for filtration and sterilization of electronic industrial cleaning water, pharmaceutical water, pharmaceutical manufacturing process water, food water, and the like. Therefore, highly reliable microporous membranes are attracting attention. Among these, the microporous film made of a crystalline polymer has excellent chemical resistance, and in particular, the crystalline polymer microporosity using polytetrafluoroethylene (hereinafter sometimes referred to as “PTFE”) as a raw material. Since the film is excellent in heat resistance and chemical resistance, the growth of the demand is remarkable.

In such a crystalline polymer microporous membrane, a preform formed by laminating homopolytetrafluoroethylene polymer and modified polytetrafluoroethylene copolymer layers is rolled, heated at a temperature equal to or higher than the melting point of the fired body, and then stretched. Thus, it has been proposed that a multilayer film composed of a filtration layer having a small average pore diameter and a support layer having a large average pore diameter can be produced (see, for example, Patent Documents 5 and 6). According to the above proposal, it is disclosed that even a very thin filtration layer can be formed and a multilayer film in which layer interfaces are completely integrated is disclosed.
However, in the above proposal, there is no description of detailed heat treatment conditions, and it is difficult to produce a film with a minute pore diameter, and it utilizes the fact that the degree of alteration changes due to slight differences in the thermal properties of each layer. Therefore, it is necessary to combine different types of materials, and there is a problem that it is difficult to produce a filter that exhibits desired performance (high flow rate).

In addition, a polytetrafluoroethylene molded body has been proposed in which a polytetrafluoroethylene powder and a low-melting-point material (resin powder) to be connected are mixed to eliminate collapse of a molded product at the time of molding due to brittleness (for example, And Patent Document 7).
However, in the above proposal, since the porosity (porosity) is lowered by the heat treatment after molding, there is a problem that it is difficult to achieve both a high flow rate and a high capture rate even if a thin film is produced. is there.

  Therefore, layers having different functions can be provided using only a material having a single type of molecular structure, fine particles having a minute pore size and several tens of nanometers can be captured efficiently, and at a high flow rate. There is a strong demand for rapid development of a crystalline polymer microporous membrane, a method for producing the same, and a filter for filtration.

US Pat. No. 1,421,341 US Pat. No. 2,783,894 US Pat. No. 4,196,070 West German Patent No. 3,003,400 JP-A-3-179038 JP-A-3-179039 JP-A-5-093086

  An object of the present invention is to solve the above-described problems and achieve the following objects. That is, according to the present invention, layers having different functions can be provided using only a material having a single type of molecular structure, and fine particles having a minute pore size and a size of several tens of nm can be efficiently captured. An object of the present invention is to provide a crystalline polymer microporous membrane having a high flow rate, a method for producing the same, and a filter for filtration.

As a result of intensive studies to achieve the above object, the inventor has a layer made of an unheated crystalline polymer excellent in moldability and specific conditions (heating temperature and heating time) that are inferior in moldability. It was found that coexistence with a layer composed of a heat-treated crystalline polymer obtained by heating with a material is important for both the moldability of the material and the reduction of the pore size in producing a dense layer. . That is, the endothermic peak in the DSC chart obtained by the first paste preparation step for preparing the first paste containing the unheated crystalline polymer and the measurement using the differential scanning calorimeter of the unheated crystalline polymer. The ratio (M _X / M ₀ ) between the maximum value (M ₀ ) and the maximum value (M _X ) of the endothermic peak in the DSC chart obtained by measurement using a differential scanning calorimeter of the heat-treated crystalline polymer A second paste preparation step of preparing a second paste containing a crystalline polymer heated under a heating condition of 0.5 to 0.95, the first paste, and the second paste as a mold A laminated preform for producing a laminated preform, a laminated body forming step for extruding and rolling the laminated preform to form a laminated body, and symmetrically heating the laminated body. Symmetric heating And the stretching step of stretching the laminated body in this order, it is possible to provide layers having different functions using only a material having a single type of molecular structure, having a minute pore diameter, and several The inventors have found a crystalline polymer microporous membrane having a high flow rate capable of capturing fine particles having a size of 10 nm, a method for producing the same, and a filter for filtration, and completed the present invention.

This invention is based on the said knowledge by this inventor, and as a means for solving the said subject, it is as follows. That is,
<1> An endothermic peak in a DSC chart obtained by a first paste preparation step of preparing a first paste containing an unheated crystalline polymer and a measurement using a differential scanning calorimeter of the unheated crystalline polymer (M _X / M ₀ ) between the maximum value (M ₀ ) and the maximum value (M _X ) of the endothermic peak in the DSC chart obtained by measurement using a differential scanning calorimeter of the heat-treated crystalline polymer A second paste preparation step of preparing a second paste containing a crystalline polymer heated under a heating condition of 0.5 to 0.95, and the first paste and the second paste are made of gold Laminating preform in which a laminated preform is manufactured by laminating in a mold, a laminate forming process in which the laminated preform is extruded and rolled to form a laminate, and the laminate is heated symmetrically Symmetric heating Degree and a method for producing a crystalline polymer microporous membrane and the stretching step, a characterized in that it comprises in this order of stretching the laminate.
<2> The method for producing a crystalline polymer microporous film according to <1>, wherein the heating temperature under the heating condition in the second paste preparation step is higher than 320 ° C. and 350 ° C. or lower.
<3> The crystalline polymer fine particle according to any one of <1> to <2>, wherein an average particle diameter of the heat-treated crystalline polymer in the second paste preparation step is 0.1 μm to 0.6 μm. It is a manufacturing method of a porous membrane.
<4> The method for producing a crystalline polymer microporous film according to any one of <1> to <3>, wherein the crystalline polymer is at least one of polytetrafluoroethylene and a polytetrafluoroethylene copolymer. It is.
<5> The crystalline polymer fine particle according to <4>, wherein the polytetrafluoroethylene copolymer contains at least two selected from tetrafluoroethylene, perfluoroalkyl vinyl ether, hexafluoropropylene, and chlorotrifluoroethylene. It is a manufacturing method of a porous membrane.
<6> A crystalline polymer microporous membrane produced by the method for producing a crystalline polymer microporous membrane according to any one of <1> to <5>.
<7> A filtering filter using the crystalline polymer microporous membrane according to <6>.

  According to the present invention, various problems in the prior art can be solved, layers having different functions can be provided using only a material having a single type of molecular structure, fine particles having a minute pore size and a size of several tens of nanometers Can be efficiently captured, and a high flow rate crystalline polymer microporous membrane, a method for producing a crystalline polymer microporous membrane, and a filter for filtration can be provided.

FIG. 1 is a diagram showing an example of steps of a method for producing a crystalline polymer microporous membrane of the present invention. FIG. 2 is a diagram showing an example of another process of the method for producing a crystalline polymer microporous membrane of the present invention. FIG. 3 is a diagram showing an example of a laminated preform. FIG. 4 is a diagram showing an example of another process of the method for producing a crystalline polymer microporous membrane of the present invention. FIG. 5 is a schematic view showing an example of a crystalline polymer microporous film having a two-layer structure according to the present invention. FIG. 6 is a schematic view showing an example of a crystalline polymer microporous film having a three-layer structure according to the present invention. FIG. 7 is a diagram illustrating an example of a structure of a general pleated filter element before being assembled in the housing. FIG. 8 is a diagram illustrating an example of a structure of a general filter element before being assembled into the housing of the capsule filter cartridge. FIG. 9 is a diagram illustrating an example of a structure of a general capsule filter cartridge integrated with a housing. FIG. 10 is a DSC chart showing an example of an unheated crystalline polymer. FIG. 11 is a DSC chart showing an example of a heat-treated crystalline polymer. FIG. 12 is a DSC chart showing an example of a completely fired crystalline polymer.

(Method for producing crystalline polymer microporous membrane)
The method for producing a crystalline polymer microporous membrane of the present invention includes a first paste preparation step, a second paste preparation step, a laminate forming step, a symmetrical heating step, and a stretching step, and if necessary, Including other processes.

<First paste preparation step>
The first paste preparation step is a step of preparing a first paste formed by mixing an unheated crystalline polymer and, if necessary, other components.

-Crystalline polymer-
The crystalline polymer means a polymer in which a crystalline region in which long chain molecules are regularly arranged in a molecular structure and an amorphous region that is not regularly arranged are mixed. Such polymers exhibit crystallinity by physical treatment. For example, when a polyethylene film is stretched by an external force, a phenomenon occurs in which a transparent film becomes cloudy at first. The above phenomenon originates from the fact that the molecular arrangement in the polymer is aligned in one direction by an external force, and crystallinity is developed.

The crystalline polymer is not particularly limited and may be appropriately selected depending on the intended purpose.For example, polyethylene, polypropylene, nylon, polyacetal, polybutylene terephthalate, polyethylene terephthalate, syndiotactic polystyrene, polyphenylene sulfide, poly Examples include ether ether ketone, wholly aromatic polyamide, wholly aromatic polyester, polyether nitrile, polytetrafluoroethylene, and polytetrafluoroethylene copolymer. These may be used individually by 1 type and may use 2 or more types together.
Among these, polytetrafluoroethylene and polytetrafluoroethylene copolymer are easy to obtain powdery products with high crystallinity, and have high solvent resistance and heat resistance. It is preferable in that it can be performed.

  The polytetrafluoroethylene is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the finely divided polytetrafluoroethylene obtained by coagulating an aqueous dispersion obtained by emulsion polymerization Ethylene is mentioned.

  The polytetrafluoroethylene copolymer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the polytetrafluoroethylene copolymer is selected from tetrafluoroethylene, perfluoroalkyl vinyl ether, hexafluoropropylene, and chlorotrifluoroethylene. A copolymer containing at least two types is exemplified.

There is no restriction | limiting in particular as a form of the said crystalline polymer, According to the objective, it can select suitably, For example, a powder form, a particulate form, etc. are mentioned.
There is no restriction | limiting in particular as an average particle diameter at the time of setting it as the powder form of the said crystalline polymer, and a particulate form, Although it can select suitably according to the objective, 0.2 micrometer-0.4 micrometer are preferable. .

  There is no restriction | limiting in particular as a glass transition temperature of the said crystalline polymer, Although it can select suitably according to the objective, 40 to 400 degreeC is preferable and 50 to 350 degreeC is more preferable.

There is no restriction | limiting in particular as a weight average molecular weight of the said crystalline polymer, Although it can select suitably according to the objective, 1,000-100,000,000 are preferable.
The number average molecular weight of the crystalline polymer is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 500 to 50,000,000, more preferably 1,000 to 25,000,000. .
There is no restriction | limiting in particular as a measuring method of the number average molecular weight of the said crystalline polymer, According to the objective, it can select suitably, For example, it can measure by gel permeation chromatography (GPC). However, since PTFE is insoluble in a solvent, crystallization heat (ΔHc: cal / g) measurement by DSC measurement is performed, and the relational expression: Mn = 2.1 × 10 ¹⁰ × ΔHc ^−5.16 is used. It is preferable to calculate.

There is no restriction | limiting in particular as said crystalline polymer, What was synthesize | combined suitably may be used and a commercial item may be used. Examples of the commercially available products include polytetrafluoroethylene (manufactured by Daikin Industries, Ltd., trade names “Polyflon PTFE”, product names “F-104”, “F-106”, “F-201”, “F-205”). ”,“ F-208 ”,“ F-301 ”,“ F-302 ”, trade names“ Lublon ”, product numbers“ L-2 ”,“ L-5 ”), polytetrafluoroethylene (Asahi Glass Co., Ltd.) , Product name “Fluon (registered trademark) PTFE”, product type “CD1”, “CD141”, “CD145”, “CD123”, “CD076”, “CD090”, “CD126”), polytetrafluoroethylene (Mitsui DuPont) Fluorochemical Co., Ltd., trade name “Teflon (registered trademark) PTFE”, brand names “6-J”, “6C-J”, “62XT”, “640-J”) The
Among these, polytetrafluoroethylene (manufactured by Daikin Industries, Ltd., trade name “Polyflon PTFE”, product number “F-106”) is easy to obtain a molded product with excellent strength at a relatively low molding pressure. preferable.

  There is no restriction | limiting in particular as content in the 1st paste of the said crystalline polymer, Although it can select suitably according to the objective, 77 mass%-87 mass% are preferable.

-Other ingredients-
The other components are not particularly limited and can be appropriately selected depending on the purpose. For example, an extrusion aid can be preferably used, and further contains an additive such as a colorant, if necessary. May be. These may be used individually by 1 type and may use 2 or more types together.

There is no restriction | limiting in particular as said extrusion aid, Although it can select suitably according to the objective, A liquid lubricant is preferable, For example, hydrocarbon oils, such as solvent naphtha and white oil, are mentioned. These may be used individually by 1 type and may use 2 or more types together.
There is no restriction | limiting in particular as said extrusion adjuvant, What was synthesize | combined suitably may be used and a commercial item may be used. Examples of the commercially available products include hydrocarbon oils (trade name “Isopar H” manufactured by Esso Oil Co., Ltd.).

  The content of the other component in the first paste is not particularly limited, and the remaining amount obtained by removing the crystalline polymer from the first paste can be the content of the other component, for example, It is preferable to add 15 to 30 parts by mass of an extrusion aid with respect to 100 parts by mass of the crystalline polymer.

-Method of preparing the first paste-
The method for preparing the first paste is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the first polymer is prepared by kneading the crystalline polymer and the other components using a kneader. For example, a method for preparing by stirring with a stirrer, a method for preparing by dispersing with a disperser, and the like.

<Second paste preparation step>
The second paste preparation step includes a heat-treated crystalline polymer obtained by heating under specific conditions (heating temperature and heating time) and pulverized into granules, and other if necessary Is a step of preparing a second paste by mixing the above components.

-Crystalline polymer-
As the crystalline polymer, a crystalline polymer similar to the crystalline polymer used in the first paste preparation step is used. In the second paste preparation step, by heating the crystalline polymer powder under specific conditions (heating temperature and heating time), the crystallinity of the layer containing the heat-treated crystalline polymer is lowered, By passing through a symmetrical heating step, a layer having a minute pore size (dense layer) can be obtained.

The specific conditions for heating the crystalline polymer powder include a maximum value (M ₀ ) of an endothermic peak in a DSC chart obtained by measurement using a differential scanning calorimeter of the unheated crystalline polymer, Ratio with the maximum value (M _X ) of the endothermic peak existing closest to the position where M ₀ was present in the DSC chart obtained by measurement using a differential scanning calorimeter of the heat-treated crystalline polymer ( This refers to the heating conditions under which M _X / M ₀ ) is 0.5 to 0.95. When the ratio (M _X / M ₀ ) is 0.5 to 0.95, the pore diameter can be reduced without impairing moldability. FIG. 10 shows a DSC chart showing an example of an unheated crystalline polymer, FIG. 11 shows a DSC chart showing an example of a heat-treated crystalline polymer, and FIG. 12 shows an example of a fully baked crystalline polymer. The DSC chart shown is shown. The broken line parallel to the Y axis shown in FIGS. 10 to 12 indicates the temperature at the maximum value of the endothermic peak of the unheated crystalline polymer, and the endothermic peak existing in the vicinity is the broken line parallel to the Y axis. Is the endothermic peak that is closest to. As shown in FIGS. 10 to 12, the maximum value (M) of the endothermic peak in the crystalline polymer is a line (parallel to the X axis) connecting the value of 300 ° C. and the value of 380 ° C. in the DSC chart of the crystalline polymer. (The broken line) as a base line, the height (h) of the perpendicular line from the maximum point of the endothermic peak to the base line is calculated.

The heating temperature when heating the crystalline polymer powder is not particularly limited as long as the ratio (M _X / M ₀ ) is within a range of 0.5 to 0.95. It can be appropriately selected depending on the purpose. For example, the heating temperature when heating the polytetrafluoroethylene powder used in the examples of the present invention is preferably over 320 ° C and not more than 350 ° C, more preferably from 325 ° C to 345 ° C, 330 ° C. to 340 ° C. is particularly preferable. The polytetrafluoroethylene has an endothermic peak corresponding to the melting point generally in the range of over 320 ° C. and 350 ° C. or less.
When the heating temperature when heating the polytetrafluoroethylene powder is 320 ° C. or less, there is a possibility that the physical properties do not change or even if it occurs, extremely long heating may be required. The time required for disappearance of the endothermic peak is shortened, it is difficult to control the crystallinity, and the moldability may be significantly deteriorated due to excessive heating. On the other hand, when the heating temperature for heating the polytetrafluoroethylene powder is within the particularly preferable range, it is advantageous in that these time problems can be avoided. The specific numerical values in the case of using other crystalline polymers are not exemplified, but the change is not caused if the heating temperature is too low, and the crystallinity control becomes difficult if the heating temperature is too high. is there.

The heating time for heating the crystalline polymer powder is not particularly limited as long as the ratio (M _X / M ₀ ) is 0.5 to 0.95. However, it is preferably 10 seconds to 10 minutes, more preferably 20 seconds to 5 minutes, and particularly preferably 30 seconds to 3 minutes. When the heating time of the crystalline polymer powder is less than 10 seconds, the time difference of the processing operation becomes remarkable, and it may be difficult to control the crystallinity. Productivity may be significantly impaired due to the amount of the powder of the functional polymer being limited. On the other hand, when the heating time of the crystalline polymer powder is within the particularly preferable range, it is advantageous to prevent these time problems.

  The method for heating the crystalline polymer powder is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a method of heating with a hot air oven.

  There is no restriction | limiting in particular as the method of grind | pulverizing the heat-processed crystalline polymer, and it can select suitably according to the objective, For example, the method of grind | pulverizing with a shaker mill is mentioned.

The average particle size of the heat-treated crystalline polymer is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.1 μm to 0.6 μm, preferably 0.2 μm to 0.5 μm. Particularly preferred.
If the average particle size of the heat-treated crystalline polymer is less than 0.1 μm, the paste viscosity may increase excessively and extrusion may be difficult, and if it exceeds 0.6 μm, the paste becomes very brittle. Therefore, a good extrusion molded product may not be obtained. On the other hand, it is advantageous in terms of moldability that the average particle diameter of the heat-treated crystalline polymer is in the particularly preferable range.

  There is no restriction | limiting in particular as content in the 2nd paste of the said crystalline polymer after heat processing, Although it can select suitably according to the objective, 77 mass%-87 mass% are preferable.

-Other ingredients-
The other components are not particularly limited and can be appropriately selected depending on the purpose. For example, an extrusion aid can be preferably used, and further contains an additive such as a colorant, if necessary. May be. These may be used individually by 1 type and may use 2 or more types together.

  There is no restriction | limiting in particular as said extrusion aid, Although it can select suitably according to the objective, A liquid lubricant is preferable, For example, the thing similar to the extrusion aid in a 1st paste preparation process is mentioned.

  There is no restriction | limiting in particular as content in the said 2nd paste of the said other component, The residual amount remove | excluding the said heat-processed crystalline polymer from the said 2nd paste is made into content of another component. For example, it is preferable to add 15 to 30 parts by mass of the extrusion aid with respect to 100 parts by mass of the heat-treated crystalline polymer.

-Method of preparing the second paste-
The method for preparing the second paste is not particularly limited and can be appropriately selected depending on the purpose. For example, the heat-treated crystalline polymer and the other components are mixed using a kneader. Examples thereof include a method of kneading and preparing, a method of stirring and preparing with a stirrer, and a method of dispersing and preparing with a disperser.

<Laminate preform body manufacturing process>
In this step, the first paste and the second paste are laminated in a mold to produce a laminated preform.

  The method for producing the laminated preform is not particularly limited and may be appropriately selected depending on the purpose. For example, at least the first paste and the second paste are laminated in a mold. And the method of producing a lamination preform by pressing and compressing is mentioned.

  The order of laminating the paste when producing the laminated preform is not particularly limited and can be appropriately selected according to the purpose. For example, the second paste is laminated on the first paste. Alternatively, the first paste may be laminated on the second paste.

  There is no restriction | limiting in particular as a metal mold | die used when producing the said lamination | stacking preforming body, According to the objective, it can select suitably, For example, a metal mold | die for plastics, a press metal mold | die, a die casting metal mold | die, a casting metal mold | die And forging dies.

  The structure of the laminated preform is not particularly limited as long as it is two or more layers, and can be appropriately selected according to the purpose. However, the layer including the first paste having two or more layers and one layer A structure having a layer including a second paste is preferable, and a layer including the two layers of the first paste and a layer of the second paste interposed between the layers including the two layers of the first paste. A three-layer structure having a containing layer is more preferable. When the structure of the laminated preform is the three-layer structure, the second paste having the smallest maximum average pore diameter that most affects the captured particle diameter can be protected from physical destruction factors such as friction and scratching. This is advantageous in that it can stabilize the capture performance and can be stably manufactured.

  The thickness of the laminated preform is set in accordance with an extrusion method or a rolling method described later. In other words, when it is set together with the extrusion method, it is produced according to the size of the paste input part of the extrusion die, and when it is set together with the rolling method, the shape is roughly determined by the inlet shape of the rolling device. Is done. The thickness of the laminated preform is not particularly limited and may be appropriately selected depending on the purpose. If a known example is shown, the laminated preform may be set in accordance with an extrusion method. The thickness is, for example, 5 cm to 10 cm, and the thickness of the laminated preform when it is set in accordance with the rolling method is, for example, 0.5 cm to 5 cm.

  When the laminated preform has a two-layer structure of a layer containing the first paste and a layer containing the second paste, the thickness of the layer containing the first paste, and the second The ratio of the thickness of the layer including the paste (the thickness of the layer including the first paste: the thickness of the layer including the second paste) is not particularly limited and may be appropriately selected depending on the purpose. It is preferably 10,000: 1 to 1.2: 1, more preferably 5,000: 1 to 1.25: 1, and 1,000: 1 to 1.5: 1. Is particularly preferred. If the ratio is more than 10,000: 1, the thickness of the layer containing the second paste may not be precisely controlled, and if it is less than 1.2: 1, the second paste The containing layer may be affected by friction and scratching and may not be able to maintain stable particulate capturing properties. In addition, it is advantageous in terms of thickness control and fine particle capturing property that the ratio is within the particularly preferable range.

When the laminated preform has a three-layer structure including a layer containing the first paste, a layer containing the second paste, and a layer containing the first paste in this order. The ratio between the maximum thickness of the layer including the first paste and the thickness of the layer including the second paste (maximum thickness of the layer including the first paste: thickness of the layer including the second paste) Is not particularly limited and may be appropriately selected according to the purpose, but is preferably 5,000: 1 to 1.2: 1, and 2,500: 1 to 1.25: 1. Is more preferable, and 1,000: 1 to 1.5: 1 is particularly preferable. If the ratio is more than 5,000: 1, the thickness of the layer containing the second paste may not be precisely controlled, and if it is less than 1.2: 1, the first paste The containing layer may be affected by friction and scratching and may not be able to maintain stable particulate capturing properties. On the other hand, when the ratio is within the particularly preferable range, it is advantageous in terms of thickness control and fine particle capturing ability.
The thickness of the other layer (the other layer not having the maximum thickness) including the first paste in the laminated preform is not particularly limited and can be appropriately selected according to the purpose. The thickness of the layer containing the second crystalline polymer is preferably not less than the thickness. If the thickness of the other layer containing the first paste (the other layer not having the maximum thickness) exceeds the thickness of the layer containing the second paste, the flow rate may not be sufficient. On the other hand, when the thickness is within the particularly preferable range, it is advantageous in terms of flow rate.

<Laminated body formation process>
The laminated body forming step is a step of forming a laminated body (unheated film laminated body) from the laminated preform.
The method for forming the laminate is not particularly limited and may be appropriately selected depending on the intended purpose. For example, after extruding and rolling the laminate preform, the extrusion aid is removed by heating to laminate the laminate. The method of forming a body (unheated film laminated body) is mentioned, The matter described in "Polyfuron handbook" (Daikin Kogyo Co., Ltd. issue, 1983 revision) can be employ | adopted suitably.

There is no restriction | limiting in particular as an extrusion method at the time of forming the said laminated body, According to the objective, it can select suitably, For example, the method of using a well-known paste extrusion apparatus is mentioned.
There is no restriction | limiting in particular as a shape of the cylinder part of the paste extrusion apparatus used for extrusion at the time of forming the said laminated body, For example, an axial perpendicular direction cross section is a rectangle of 50 mm x 100 mm. And a shape composed of a nozzle 50 mm × 5 mm in which one of the cylinder portions is narrowed at the outlet portion.
There is no restriction | limiting in particular as extrusion temperature at the time of forming the said laminated body, Although it can select suitably according to the objective, It is preferable to carry out at 19 to 200 degreeC.
There is no restriction | limiting in particular as an extrusion shape at the time of forming the said laminated body, Although it can select suitably according to the objective, A rod shape is preferable and a sheet form is more preferable.

There is no restriction | limiting in particular as a rolling method at the time of forming the said laminated body, According to the objective, it can select suitably, For example, the method of rolling the said extrudate with a calender roll is mentioned.
There is no restriction | limiting in particular as a rolling speed | rate at the time of forming the said laminated body, According to the objective, it can select suitably, For example, calendaring can be performed at a speed | rate of 5 m / min.
There is no restriction | limiting in particular as the temperature which rolls at the time of forming the said laminated body, According to the objective, it can select suitably, For example, calendaring can be performed at the temperature of 19 degreeC-380 degreeC.

The method for removing the extrusion aid by heating at the time of forming the laminate is not particularly limited and can be appropriately selected depending on the purpose. For example, the extrusion aid is obtained by passing the film through a hot air drying furnace. The method of removing an agent is mentioned.
There is no restriction | limiting in particular as the temperature of the heating at the time of forming the said laminated body, Although it can select suitably according to the kind of extrusion adjuvant, 40 to 400 degreeC is preferable and 60 to 350 degreeC is more. preferable. For example, when removing solvent naphtha from polytetrafluoroethylene, 150 ° C. to 280 ° C. is preferable, and 180 ° C. to 260 ° C. is more preferable.

  There is no restriction | limiting in particular as thickness of the said laminated body, Although it can adjust suitably according to the objective, 1 micrometer-300 micrometers are preferable, 5 micrometers-200 micrometers are more preferable, and 10 micrometers-100 micrometers are especially preferable.

<Symmetric heating process>
The symmetrical heating step is a step of forming a symmetrical heating film by heating the entire laminate (unheated film laminate) uniformly and evenly.
The symmetrical heating method is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a method of heating with a salt bath, a method of blowing hot air with a hot air heater, a method of heating with a furnace, a heating roll The method of heating by making it contact, The method of heating by irradiating IR, etc. are mentioned. Among these, heating by a salt bath is preferable in that the heating variation can be suppressed when the entire laminate is heated.
There is no restriction | limiting in particular as temperature at the time of the said symmetrical heating, Although it can select suitably according to the objective, It is preferable that it is 343 degreeC-350 degreeC.

<Extension process>
The stretching step is a step of stretching the symmetric heating film.
There is no restriction | limiting in particular as the method of extending | stretching, According to the objective, it can select suitably, It is the method of extending | stretching the said symmetrical heating film laminated body about both the longitudinal direction and the width direction, for example, extending | stretching of a longitudinal direction And a method of performing stretching in the width direction after performing the above, a method of performing biaxial stretching at the same time, and the like.

There is no restriction | limiting in particular as a draw ratio of the longitudinal direction at the time of the said extending | stretching, Although it can select suitably according to the objective, 1.2 times-50 times are preferable, and 1.5 times-40 times are more preferable. 2.0 times to 10 times is particularly preferable.
There is no restriction | limiting in particular as extending | stretching temperature of the longitudinal direction at the time of the said extending | stretching, Although it can select suitably according to the objective, 35 to 330 degreeC is preferable, 45 to 320 degreeC is more preferable, and 55 to 310 ° C. is particularly preferred.

There is no restriction | limiting in particular as the draw ratio of the width direction at the time of the said extending | stretching, Although it can select suitably according to the objective, 1.2 times-50 times are preferable, and 1.5 times-40 times are more preferable. 2.0 times to 30 times is more preferable, and 2.5 times to 10 times is particularly preferable.
There is no restriction | limiting in particular as the extending | stretching temperature of the width direction at the time of the said extending | stretching, Although it can select suitably according to the objective, 35 to 330 degreeC is preferable, 45 to 320 degreeC is more preferable, and 60 to 310 ° C. is particularly preferred.

There is no restriction | limiting in particular as an area draw ratio at the time of extending | stretching, Although it can select suitably according to the objective, 1.5 times-2,500 times are preferable and 2 times-2,000 times are more preferable. 2.5 times to 100 times is particularly preferable. When stretching is performed, the crystalline polymer film may be preheated to a temperature equal to or lower than the stretching temperature in advance.
In addition, after extending | stretching, heat setting can be performed as needed. The heat setting temperature is usually preferably higher than the stretching temperature and lower than the melting point of the crystalline polymer, and when the crystalline polymer is a fluororesin such as PTFE, it is preferable to heat at the melting point or higher.

<Other processes>
There is no restriction | limiting in particular as said other process, According to the objective, it can select suitably, For example, a surface modification process is mentioned.

  The surface modification step is a step of modifying the surface of at least a part of the crystalline polymer microporous membrane. At least a part of the crystalline polymer microporous membrane includes not only the exposed surface of the crystalline polymer microporous membrane but also the periphery of the pore and the inside of the pore.

  The method for modifying the surface is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a method of laser irradiation after impregnation with an aqueous solution of hydrogen peroxide solution or a water-soluble solvent (Japanese Patent Application Laid-Open No. 7-1993). 308888), a method of irradiating with radiation, plasma, etc. (Japanese Patent Laid-Open No. 2003-151571), a chemical etching process (Japanese Patent Laid-Open No. 2007-154153), and a method of coating with a cross-linked material (Japanese Patent Laid-Open No. 8-283447). And a method of coating with a polymer material (Japanese Patent Laid-Open No. 2000-235849).

  Here, with reference to FIGS. 1-4, an example of the manufacturing method of the crystalline polymer microporous film | membrane of this invention is demonstrated.

As shown in FIG. 1, the first paste is placed on the lower mold 8 in a layer form in a box-shaped lower mold 8 and pressed in the direction of the arrow using an upper mold (not shown). Thus, the first layer 4 is formed by being compressed.
Next, as shown in FIG. 2, a paste containing fine powder of PTFE for forming the second layer 5 is placed on the first layer 4, and similarly compressed using an upper mold (not shown). .
As described above, a laminated preform 10 in which the second layer 5 is laminated on the first layer 4 as shown in FIG. 3 is obtained.
After the obtained laminated preform 10 is stored in the cylinder part of the paste extrusion apparatus as shown in FIG. 4, it is pressed in the direction of the arrow by a pressing means (not shown). Thus, the 1st layer 4 and the 2nd layer 5 are completely integrated, and the laminated body (unheated film laminated body) 15 in which each layer has uniform thickness is shape | molded. A crystalline polymer microporous film is produced by symmetrically heating and stretching the laminate 15.

(Crystalline polymer microporous membrane)
The crystalline polymer microporous membrane of the present invention is a microporous membrane produced by the method for producing a crystalline polymer microporous membrane.

  The structure of the crystalline polymer microporous film is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the layer containing the first paste and the layer containing the second paste A laminated structure having a boundary between them can be given.

  The method for confirming that the crystalline polymer microporous membrane has a laminated structure is not particularly limited and can be appropriately selected depending on the purpose. For example, the crystalline polymer microporous membrane is arranged in the thickness direction. There is a method of detecting a section cut by freezing by observing it with an optical microscope or a scanning electron microscope (SEM).

The shape of the pores of the crystalline polymer microporous membrane is not particularly limited and may be appropriately selected depending on the purpose.For example, the crystalline polymer microporous membrane penetrates in the thickness direction of the crystalline polymer microporous membrane, Examples of the shape of the plurality of pores in which at least one layer in the crystalline polymer microporous membrane is constant without change in the average pore diameter in at least a part of the crystalline polymer microporous membrane in the thickness direction. By adopting the shape, fine particles can be captured efficiently.
Here, the at least one layer in the crystalline polymer microporous membrane is a plurality of pores whose average pore diameter is constant without change in at least a part in the thickness direction of the crystalline polymer microporous membrane. When the distance t (corresponding to the depth from the front surface) in the thickness direction from the front surface of the crystalline polymer microporous membrane is taken as the axis, and the average pore diameter D of the pores is taken as the vertical axis, (1) A graph from the front surface (d = 0) to the back surface (d = film thickness) is drawn with one continuous line for each crystalline polymer layer (continuous), and the slope of the graph (DD / dt) is substantially 0 (zero). The substantially 0 (zero) includes about ± 10% from the average value and does not include monotonic increase and monotonic decrease.

  There is no restriction | limiting in particular as a method of confirming the shape of the hole part of the said crystalline polymer microporous film | membrane, According to the objective, it can select suitably, For example, observation with an optical microscope or a scanning electron microscope (SEM) The method of confirming by doing is mentioned.

The average pore diameter of the pores of the crystalline polymer microporous membrane is not particularly limited and can be appropriately selected according to the purpose.For example, the average pore diameter of the pores in the layer containing the first paste, The average pore diameter of the holes in the layer containing the second paste has a different average pore diameter.
The average pore diameter of the pores in the layer containing the first paste of the crystalline polymer microporous film is not particularly limited and can be appropriately selected according to the purpose, but is preferably 1 μm or less, More preferably, it is 0.5 μm or less.
There is no restriction | limiting in particular as an average hole diameter of the hole part in the layer containing the 2nd paste of the said crystalline polymer microporous film | membrane, Although it can select suitably according to the objective, 1 nm-200 nm are preferable, and 5 nm- 150 nm is more preferable, and 10 nm to 100 nm is particularly preferable.

  The method for measuring the average pore diameter of the pores in the crystalline polymer microporous membrane is not particularly limited and can be appropriately selected according to the purpose. For example, the surface of the membrane or the cross section of the membrane can be selected with a scanning electron microscope. (SEM photograph, magnification: 1,000 to 100,000 times), and the resulting photograph is an image processing device (main body: Nippon Avionics Co., Ltd., trade name “TV Image Processor TVIP-4100II”, control software : A product name “TV Image Processor Image Command 4198” manufactured by Ratok System Engineering Co., Ltd.), obtaining an image composed only of crystalline polymer fibers, and calculating the average pore diameter by calculating the image. It is done.

The average flow pore size in the crystalline polymer microporous membrane refers to the pore size determined from the intersection of 1/2 in the dry state and the air flow rate in the wet state.
The average flow pore size of the pores in the layer containing the first paste of the crystalline polymer microporous membrane is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 1 μm or less. More preferably, it is 0.5 μm or less.
The average flow pore size of the pores in the layer containing the second paste of the crystalline polymer microporous membrane is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 1 nm to 200 nm, preferably 5 nm. -150 nm is more preferable, and 10 nm to 100 nm is particularly preferable.

  There is no restriction | limiting in particular as a method of measuring the average flow volume diameter of the hole part of the said crystalline polymer microporous film | membrane, According to the objective, it can select suitably, For example, by a half dry method (ASTM E1294-89) The method of measuring is mentioned. Specifically, up to 15 nm can be measured with a 500 psi high pressure palm porometer (manufactured by PMI), and 15 nm or less can be measured with a nano palm porometer (manufactured by PMI).

  There is no restriction | limiting in particular as thickness of the said crystalline polymer microporous film | membrane, Although it can select suitably according to the objective, 1 micrometer-300 micrometers are preferable, 5 micrometers-200 micrometers are more preferable, 10 micrometers-100 micrometers are especially preferable.

When the maximum thickness of the layer containing the first paste in the crystalline polymer microporous film is made larger than the maximum thickness of the layer containing the second paste, the flow rate of the crystalline polymer microporous film can be improved. it can.
When the thickness of the layer containing the second paste in the crystalline polymer microporous film is reduced, the flow rate characteristics are improved while the fine particle capturing rate is reduced. On the contrary, when the thickness of the layer containing the second paste in the crystalline polymer microporous film is increased, the flow rate characteristic is lowered, but the fine particle capturing rate is improved.
Here, the maximum thickness means the maximum value of the thickness of each layer. For example, in the case of a stacked body including a layer including a first paste having a thickness of 20 μm, a layer including a first paste having a thickness of 15 μm, and a layer including a first paste having a thickness of 10 μm, the first The maximum thickness of the layer including the paste is 20 μm, the layer including the second paste having a thickness of 20 μm, the layer including the second paste having a thickness of 15 μm, and the layer including the second paste having a thickness of 10 μm. In the case of the laminate having the above, the maximum thickness of the layer containing the second paste is 20 μm.

  The method for measuring the thickness of the crystalline polymer microporous film is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the crystalline polymer microporous film is frozen and cleaved, and scanning electron The method of measuring the thickness of each layer is mentioned by observing the cross section of each layer with a microscope (SEM).

  Here, an example of the crystalline polymer microporous membrane of the present invention will be described with reference to FIGS.

  As shown in FIG. 5, the hole 101b in the crystalline polymer microporous membrane of the present invention having a two-layer structure in which a layer 101 containing a first crystalline polymer and a layer 102 containing a second crystalline polymer are laminated, The average pore diameter of 102b is constant without any change in the thickness direction of the laminate, and the average pore diameter of the entire crystalline polymer microporous film changes (decreases in steps) in the thickness direction.

  As shown in FIG. 6, the average pore diameters of the holes 101b, 102b, 103b in the crystalline polymer microporous membrane of the present invention having a three-layer structure in which the layers 101, 102, 103 containing the crystalline polymer are laminated are all There is no change in the thickness direction of the laminate, and the entire crystalline polymer microporous film has a portion where the average pore diameter changes stepwise in the thickness direction. The layer 102 containing the second crystalline polymer having the largest average pore diameter Lm2 of the smallest pores among the largest average pore diameters Lm1, Lm2, and Lm3 of the pores is a crystalline polymer microporous membrane (laminate). Exists inside.

  The crystalline polymer microporous membrane of the present invention has a fine pore size, can efficiently capture fine particles of several tens of nanometers in size, and has a high flow rate, so it can be used in various applications that require filtration. Although it can be used, it can be particularly suitably used as a filter for filtration described below.

(Filter for filtration)
The filtration filter of the present invention is characterized by using the crystalline polymer microporous membrane.
Further, in the filter for filtration of the present invention, since the specific surface area of the crystalline polymer microporous membrane is large, the fine particles introduced from the surface are removed by adsorption or adhesion before reaching the minimum pore diameter portion. Therefore, clogging is unlikely to occur and high filtration efficiency can be maintained over a long period of time.

  There is no restriction | limiting in particular as a shape of the said filter for filtration, Although it can select suitably according to the objective, It is preferable to process and shape in a pleat shape. When the shape of the filter for filtration is the pleated shape, it is advantageous in that the effective surface area used for filtering the filter per cartridge can be increased.

Here, with reference to FIGS. 7-9, an example of the filter for filtration of this invention is demonstrated.
7 to 9 are specific examples of the microfiltration filter cartridge, and the present invention is not limited to these drawings.

  FIG. 7 is a development view showing the structure of an element exchange type pleated filter cartridge element. The microfiltration membrane 113 is folded and folded around a core 115 having a large number of liquid collection ports while being sandwiched by two membrane supports 112 and 114. On the outside, there is an outer cover 111 that protects the microfiltration membrane. Microfiltration membranes are sealed at both ends of the cylinder by end plates 116a and 116b. The end plate is in contact with a seal portion of a filter housing (not shown) through a gasket 117. The filtered liquid is collected from the core collection port and discharged from the fluid outlet 118.

FIG. 8 is a development view of the entire structure of the microfiltration membrane filter element before being assembled into the housing of the capsule filter cartridge. The microfiltration membrane 22 is folded in a state of being sandwiched by two supports, a primary support 21 and a secondary support 23, and is wound around a filter element core 27 having a large number of liquid collection ports. . There is a filter element cover 26 on the outside to protect the microfiltration membrane. Microfiltration membranes are sealed at both ends of the cylinder by an upper end plate 24 and a lower end plate 25.
FIG. 8 shows an example in which the lower end plate 25 and the housing base are sealed via the O-ring 28. The lower end plate 25 and the housing base are sealed by heat fusion or an adhesive. Sometimes. Alternatively, the seal between the housing base and the housing cover can be made by using an adhesive in addition to heat sealing.

  FIG. 9 is a view showing the structure of a capsule pleated filter cartridge in which a filter element is integrated in a housing. The filter element 30 is incorporated in a housing composed of a housing base 32 and a housing cover 31. The lower end plate is sealed by a water collecting pipe (not shown) at the center of the housing base 32 through an O-ring. The liquid enters the housing from the liquid inlet nozzle 33, passes through the filter medium 29, is collected from the liquid collection port of the filter element core 27, and is discharged from the liquid outlet nozzle 34. The housing base 32 and the housing cover 31 are usually heat-sealed in a liquid-tight manner at the welding portion 37.

  Since the filter for filtration using the crystalline polymer microporous membrane of the present invention has such a high filtration function and a long life, the filtration device can be made compact. In the conventional filtration apparatus, a large number of filtration units are used in series to cope with the short filtration life. However, if the filtration filter of the present invention is used, the number of filtration units used in series is greatly increased. Can be reduced. Moreover, since the replacement period of the filter for filtration can be extended significantly, the cost and time required for maintenance can be reduced.

  The filtration filter of the present invention is suitably used for microfiltration of gases, liquids, etc., for example, filtration of corrosive gas, various gases used in the semiconductor industry, washing water for electronics industry, pharmaceutical water, pharmaceutical manufacture Widely used in process water, food water filtration, sterilization, high temperature filtration, reactive chemical filtration, wire coating materials, catheters, artificial blood vessels, anti-adhesion membranes, cell culture scaffolds, insulating membranes, fuel cell separators, etc. it can.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
<Preparation of crystalline polymer microporous membrane>
-First paste preparation step-
As an unheated crystalline polymer, polytetrafluoroethylene fine powder (manufactured by Daikin Industries, Ltd., trade name “Polyflon PTFE”, product number “F-106”) 100 parts by mass, as an extrusion aid, hydrocarbon oil 23 parts by mass (trade name “Isopar H” manufactured by Esso Oil Co., Ltd.) was added to prepare a first paste.

-Second paste preparation step-
As a crystalline polymer, polytetrafluoroethylene fine powder (trade name “Polyflon PTFE”, product name “F-106”, manufactured by Daikin Industries, Ltd.) is leveled on a metal bat so that the thickness is 2 mm. The fine powder was allowed to stand for 30 seconds after the temperature of the fine powder reached 340 ° C. by a thermocouple installed in the bat, and then the bat was taken out and air-cooled in the air. The fine powder heat-treated product in the form of a fragile plate was divided into portions that passed through the mouth of the container, sealed in the container, and pulverized by shaking the container to obtain a granular heat-treated crystalline polymer 1 . 100 parts by mass of the heat-treated crystalline polymer 1 and 25 parts by mass of hydrocarbon oil (trade name “Isopar H” manufactured by Esso Petroleum Corporation) were added as an extrusion aid to prepare a second paste.

-Laminated preform fabrication process-
Lamination and pressurization were performed so that the thickness ratio (paste 1 / paste 2 / paste 1) between the first paste and the second paste was 3/1/1 to produce a laminated preform.

-Laminate formation process-
The laminated preform was inserted into a square cylinder of a paste extrusion mold, and a multilayer paste was extruded into a sheet shape. This was calendered with a calender roll heated to 60 ° C. to produce a polytetrafluoroethylene film having a laminated structure. The resulting polytetrafluoroethylene film was passed through a hot air drying oven at 250 ° C. to dry and remove the extrusion aid, and a laminate having an average thickness of 140 μm, an average width of 150 mm, and a specific gravity of 1.45 was obtained. Heated film laminate) was formed.

-Symmetric heating process-
The laminate was heated in a salt bath kept at 344 ° C. for 50 seconds to produce a symmetrical heating film.

-Stretching process-
The symmetrical heating film was stretched between rolls in the longitudinal direction by 3 times at 300 ° C., and then wound up on a winding roll. Thereafter, both ends were sandwiched between clips, stretched three times in the width direction at 300 ° C., and heat fixed at 320 ° C.
Thus, the crystalline polymer microporous membrane of Example 1 was produced.

(Example 2)
<Preparation of crystalline polymer microporous membrane>
In the second paste preparation step of Example 1, the ultimate temperature of the fine powder of polytetrafluoroethylene was set to 330 ° C., except that the heat-treated crystalline polymer 2 was obtained. The crystalline polymer microporous membrane of Example 2 was prepared.

(Comparative Example 1)
<Preparation of crystalline polymer microporous membrane>
In the second paste preparation process of Example 1, the ultimate temperature of the fine powder of polytetrafluoroethylene was set to 320 ° C., except that the heat-treated crystalline polymer 3 was obtained. A crystalline polymer microporous membrane of Comparative Example 1 was prepared. In addition, since the heat-treated crystalline polymer 3 was already granular, it was not pulverized by shaking in the second paste preparation step, and the heat-treated crystalline polymer 3 and did.

(Comparative Example 2)
<Preparation of crystalline polymer microporous membrane>
In the second paste preparation step of Example 1, the ultimate temperature of the fine powder of polytetrafluoroethylene was set to 360 ° C., except that the heat-treated crystalline polymer 4 was obtained. A crystalline polymer microporous membrane of Comparative Example 2 was prepared.

(Comparative Example 3)
<Preparation of crystalline polymer microporous membrane>
The crystallinity of Comparative Example 3 is the same as that of Example 1 except that a preform is produced using only the first paste of Example 1 without using the second paste of Example 1. A polymer microporous membrane was prepared.

(Comparative Example 4)
<Preparation of crystalline polymer microporous membrane>
The crystallinity of Comparative Example 4 is the same as Example 1 except that the first paste of Example 1 is not used and only the second paste of Example 1 is used to prepare a preform. An attempt was made to produce a polymer microporous membrane, but the sheet-like molded product obtained during extrusion was very brittle and could not be calendared.

(Evaluation)
<Ratio of endothermic peak in DSC chart (M _X / M ₀ )>
First, using a differential scanning calorimeter (trade name “DSC7200” manufactured by Seiko Instruments Inc.), the unheated crystalline polymer used in the first paste preparation steps of Examples 1 and 2 and Comparative Examples 1 to 3, Measurement was carried out at a rate of temperature increase of 10 ° C./min, and the endothermic peak height (h ₀ ) in the DSC chart was specified.
Further, the heat-treated crystalline polymer used in the first paste preparation steps of Examples 1 and 2 and Comparative Examples 1, 2, and 4 was subjected to an endothermic peak in a DSC chart using the differential scanning calorimeter. The height (h _x ) was identified.
Next, a fine powder of polytetrafluoroethylene, which is a crystalline polymer used in the first paste preparation step and the second paste preparation step (made by Daikin Industries, Ltd., trade name “Polyflon PTFE”, product number “F” -106 ") was heated at a temperature equal to or higher than the melting point (360 ° C) for 10 minutes and then cooled to obtain a fully baked crystalline polymer.
Using the differential scanning calorimeter, the DSC chart is prepared for the crystalline polymer of all firing, and the endothermic peak height is determined by using a line connecting each 300 ° C. value and 380 ° C. value as a baseline. The maximum values (M ₀ and M _X ) were determined based on (h ₀ and h _x ), and the ratio of endothermic peaks (M _X / M ₀ ) was calculated. The results are shown in Table 1.

<Average flow pore size>
Using the crystalline polymer microporous membranes prepared in Examples 1 and 2 and Comparative Examples 1 to 3, the average flow pore size was measured with a high-pressure palm porometer (manufactured by PMI). In Comparative Example 4, since the crystalline polymer microporous membrane could not be produced, the average flow pore size was not measured. The results are shown in Table 1.

<Flow test>
Using the crystalline polymer microporous membranes prepared in Examples 1 and 2 and Comparative Examples 1 to 3, unit area (m ² ) and unit time when isopropyl alcohol (IPA) was allowed to flow at a differential pressure of 100 kPa The permeation amount per (min) was measured as a flow rate (L · m ⁻² · min ⁻¹ ), and a flow rate test was performed. In Comparative Example 4, since the crystalline polymer microporous film could not be produced, a flow rate test was not performed. The results are shown in Table 1.

In Examples 1 and 2, since the ratio (M _X / M ₀ ) is 0.5 to 0.95, the heating condition in the second paste preparation step becomes an appropriate condition without impairing the moldability. A crystalline polymer microporous membrane having a fine pore diameter and a high flow rate could be produced.
On the other hand, in Comparative Examples 1 and 2, since the ratio (M _X / M ₀ ) is in a range out of 0.5 to 0.95, the heating condition in the second paste preparation step becomes an inappropriate condition, The intended crystalline polymer microporous membrane could not be produced. In Comparative Example 3, since the crystalline polymer microporous film was produced without using the second paste, the average pore diameter was large. In Comparative Example 4, since the crystalline polymer microporous membrane was produced without using the first paste, the sheet-like molded body obtained at the time of extrusion was very brittle and could not be calendered. It was not possible to produce a porous polymer microporous membrane.

  The crystalline polymer microporous membrane of the present invention and a filter for filtration using the same can be used in various situations where filtration is required, and is suitably used for microfiltration of gases, liquids, etc. Filtration of corrosive gases, various gases used in the semiconductor industry, electronic industry cleaning water, pharmaceutical water, pharmaceutical manufacturing process water, food water filtration, sterilization, high temperature filtration, reactive chemical filtration, wire coating It can be widely used for materials, catheters, artificial blood vessels, adhesion prevention membranes, cell culture scaffolds, insulating membranes, fuel cell separators, and the like.

4 1st layer 5 2nd layer 8 Lower mold 10 Laminated preform 15 Laminated body (unheated film laminated body)
21 Primary support 22 Microfiltration membrane 23 Secondary support 24 Upper end plate 25 Lower end plate 26 Filter element cover 27 Filter element core 28 O-ring 29 Filter media 30 Filter element 31 Housing cover 32 Housing base 33 Liquid inlet nozzle 34 Liquid Outlet nozzle 37 Welding portion 101 Layer containing crystalline polymer 102 Layer containing crystalline polymer 103 Layer containing crystalline polymer 101b Hole portion 102b Hole portion 103b Hole portion 111 Outer peripheral cover 112 Membrane support 113 Microfiltration membrane 114 Membrane support 115 Core 116a End plate 116b End plate 117 Gasket 118 Liquid outlet Lm1 Maximum average hole diameter of the hole Lm2 Maximum average hole diameter of the hole Lm3 Large average pore size

Claims (7)

A first paste preparation step of preparing a first paste comprising an unheated crystalline polymer;
The maximum value (M ₀ ) of the endothermic peak in the DSC chart obtained by the measurement using the differential scanning calorimeter of the unheated crystalline polymer and the measurement using the differential scanning calorimeter of the crystalline polymer after heat treatment A second paste containing a crystalline polymer heated under heating conditions in which the ratio (M _X / M ₀ ) to the maximum value (M _X ) of the endothermic peak in the obtained DSC chart is 0.5 to 0.95 A second paste preparation step to be prepared;
A laminated preform forming step for producing a laminated preform by laminating the first paste and the second paste in a mold;
A laminated body forming step of extruding and rolling the laminated preform to form a laminated body;
A symmetrical heating step of symmetrically heating the laminate;
A stretching step of stretching the laminate;
In this order, a method for producing a crystalline polymer microporous membrane.   The method for producing a crystalline polymer microporous film according to claim 1, wherein the heating temperature under the heating conditions in the second paste preparation step is 320 ° C or higher and 350 ° C or lower.   The method for producing a crystalline polymer microporous film according to any one of claims 1 to 2, wherein an average particle size of the crystalline polymer subjected to the heat treatment in the second paste preparation step is 0.1 µm to 0.6 µm. .   The method for producing a crystalline polymer microporous membrane according to any one of claims 1 to 3, wherein the crystalline polymer is at least one of polytetrafluoroethylene and a polytetrafluoroethylene copolymer.   The crystalline polymer microporous membrane according to claim 4, wherein the polytetrafluoroethylene copolymer comprises at least two selected from tetrafluoroethylene, perfluoroalkyl vinyl ether, hexafluoropropylene, and chlorotrifluoroethylene. Production method.   A crystalline polymer microporous membrane produced by the method for producing a crystalline polymer microporous membrane according to any one of claims 1 to 5.   A filter for filtration, wherein the crystalline polymer microporous membrane according to claim 6 is used.