JP2012206113A - Crystalline polymer microporous membrane, method for producing the same, and filtration filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide high flow rate and high strength crystalline polymer microporous membrane having easily obtained by a process only consisting of extrusion and rolling without stretching and heating capable of efficiently catching a fine particle of several tens nm size, and to provide an efficient method for producing the crystalline polymer microporous membrane and a filtration filter.SOLUTION: The method for producing a crystalline polymer microporous membrane includes: a preparatory formed body producing step for producing a preparatory formed body using a crystalline polymer; an extrusion step for extruding the preparatory formed body into a sheet shape using an extrusion device having a drawing ratio of at least 50 and comprising a preparatory formed body introduction section that introduces the preparatory formed body, a draw section connected on the downstream side of the preparatory formed body introduction section, and a fan connected on the downstream side of the draw section and having a central angle of 30-80° and an exit width of at least 200 mm; and a rolling step for rolling the sheet comprising the crystalline polymer obtained by the extrusion step.

Description

  The present invention relates to a filter for filtration, a crystalline polymer microporous membrane suitable for the filter for filtration, and a preferred production method thereof.

  Microporous membranes have been known for a long time. However, in recent years, as a filter for filtration used in electronic industrial cleaning water, pharmaceutical water, pharmaceutical manufacturing process water, food water, etc. A highly reliable microporous membrane is drawing attention.

  Examples of the material of such a microporous membrane include cellulose ester (for example, see Patent Document 1), aliphatic polyamide (for example, see Patent Document 2), polyfluorocarbon (for example, see Patent Document 3), polypropylene ( For example, Patent Document 4), polytetrafluoroethylene (hereinafter sometimes referred to as “PTFE”) (see, for example, Patent Documents 5 and 6), and the like are known. Among these, the crystalline polymer microporous membrane using PTFE as a raw material is excellent in heat resistance and chemical resistance, and also has an excellent balance between the pore diameter and the flow rate.

As the crystalline polymer microporous film made of PTFE as a raw material, for example, a preformed body charging part of an extrusion mold used when extruding PTFE paste, and a drawn part connected to the preformed body charging part It has been proposed that by increasing the drawing ratio, the shear strength applied to the PTFE paste is increased and a desired microporous film can be obtained (see, for example, Patent Documents 7 and 8).
In these proposals, a sheet molded product obtained by extrusion and rolling is stretched at a high magnification, and a desired film is obtained by heat treatment as necessary. However, it is assumed that the sheet molded product is thinner and tougher than the sheet molded product. If such a sheet molded product becomes available, it is possible not only to simplify the process such as lowering the draw ratio and to improve the filtration performance, but also to open up applications for various uses other than filtration.
However, the film once stretched and heat-treated is inferior in stretch process suitability and difficult to use, and the reason is not clear, but it is difficult to produce a PTFE film of less than 50 μm only by extrusion and rolling. (For example, refer nonpatent literature 1), and the material technology using the thin film PTFE sheet molding is not yet proposed.

  Therefore, a crystalline polymer molded body of a thin film that can be easily obtained by only the process of extrusion and rolling, an efficient manufacturing method thereof, and a filter for filtration produced using the crystalline polymer molded body of these thin films can be quickly obtained. At present, there is a strong demand for new development.

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 2009-61363 A JP 2009-73051 A

Fluoropolymer Handbook Takaomi Satokawa Edition Nichi Kogyo Shimbun

  An object of the present invention is to solve the above-described problems and achieve the following objects. That is, the present invention can be easily obtained by only the process of extrusion and rolling without stretching and heating, has a fine pore diameter, can efficiently capture fine particles of several tens of nanometers, and has a high flow rate. And it aims at providing the crystalline polymer microporous film | membrane of the thin film which is high intensity | strength, its efficient manufacturing method, and the filter for filtration.

  As a result of intensive studies by the inventor in order to solve the above-mentioned problems, when extruding a preform formed using a crystalline polymer, a preformed body charging portion for charging the preform, and the preform A throttle part connected to the downstream side of the body throwing part, and a fan part connected to the downstream side of the throttle part and having a central angle of 30 ° to less than 80 ° and an exit width of 200 mm or more. Moreover, it has been found that by using an extrusion apparatus having a drawing ratio of 50 or more, a crystalline polymer microporous film having a thickness of 50 μm or less can be produced only by extrusion and rolling, which had been impossible in the past. The present inventor has also found an efficient method for producing the crystalline polymer microporous membrane and a filter for filtration having a micropore diameter using the crystalline polymer microporous membrane.

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> Preliminary body production process for producing a preform using a crystalline polymer, a preform body charging part for charging the preform, and a throttle connected to the downstream side of the preform charging part And a fan part connected to the downstream side of the throttle part, having a central angle of 30 ° to less than 80 °, an outlet width of 200 mm or more, and having a drawing ratio of 50 or more. A crystalline polymer comprising: an extrusion process for extruding the preform into a sheet using an apparatus; and a rolling process for rolling a sheet made of a crystalline polymer obtained by the extrusion process. This is a method for producing a microporous membrane.
<2> The method for producing a crystalline polymer microporous film according to <1>, wherein a 1,000% tensile strength in the width direction in the sheet made of the crystalline polymer obtained by the extrusion step is 6 MPa or more. .
<3> The crystalline polymer microporous property according to any one of <1> to <2>, wherein the average thickness of the crystalline polymer microporous membrane is 50 μm or less by rolling the sheet in the rolling step. It is a manufacturing method of a film | membrane.
<4> The crystalline polymer microporous membrane according to any one of <1> to <3>, including a stretching step of stretching the crystalline polymer microporous membrane obtained by the rolling step in at least one axial direction. It is a manufacturing method.
<5> Production of crystalline polymer microporous membrane according to <4>, including a heating step of heating the crystalline polymer microporous membrane obtained by the stretching step at a temperature equal to or higher than the melting point of the crystalline polymer. Is the method.
<6> The preform is formed by laminating a layer containing a first crystalline polymer and a layer containing a second crystalline polymer, and the melting point of the first crystalline polymer is the second crystal. The method for producing a crystalline polymer microporous membrane according to any one of <1> to <5>, wherein the crystalline polymer has a melting point higher than that of the crystalline polymer.
<7> A crystalline polymer microporous membrane produced by the method for producing a crystalline polymer microporous membrane according to any one of <1> to <6>.
<8> The crystalline polymer microporous membrane according to <7>, wherein the average thickness is 50 μm or less.
<9> A filtering filter using the crystalline polymer microporous membrane according to any one of <7> to <8>.

  According to the present invention, the above-mentioned problems in the prior art can be solved, the object can be achieved, and it can be obtained simply by the process of extrusion and rolling without stretching and heating, and has a fine pore diameter, To provide a crystalline polymer microporous membrane of a thin film having a high flow rate and high strength, capable of efficiently capturing fine particles having a size of several tens of nanometers, an efficient manufacturing method thereof, and a filter for filtration. it can.

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 illustrating an example of a 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 diagram illustrating an example of an extrusion apparatus used in the present invention. FIG. 6 is a schematic view showing an example of a crystalline polymer microporous film having a two-layer structure according to the present invention. FIG. 7 is a schematic view showing an example of a crystalline polymer microporous film having a three-layer structure according to the present invention. FIG. 8 is a diagram showing a structure of a general pleated filter element before being assembled in the housing. FIG. 9 is a view showing the structure of a general filter element before being assembled into the housing of the capsule filter cartridge. FIG. 10 is a view showing the structure of a general capsule filter cartridge integrated with a housing.

(Method for producing crystalline polymer microporous membrane)
The method for producing a crystalline polymer microporous membrane of the present invention includes a preform forming step, an extrusion step, and a rolling step, and further includes other steps as necessary.

<Preliminary body manufacturing process>
The preforming step is a step of preparing a preform using a crystalline polymer. The crystalline polymer is preferably a paste when the preform is produced, and the paste may contain other components.

  The crystalline polymer is not particularly limited and may be appropriately selected depending on the intended purpose.However, the crystalline polymer is regularly aligned with a crystalline region in which long chain molecules are regularly aligned in the molecular structure. A polymer in which non-crystalline regions are mixed is preferable. 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. However, it is preferable to use a crystalline polymer having a different melting point, and the first crystalline polymer (with a high melting crystalline polymer and And a second crystalline polymer (sometimes referred to as a low melting crystalline polymer) that is lower than the melting point of the first crystalline polymer.

There is no restriction | limiting in particular as melting | fusing point of the said crystalline polymer, Although it can select suitably according to the objective, Melting | fusing point of the said 1st crystalline polymer is 1 rather than melting | fusing point of the said 2nd crystalline polymer. It is preferably higher by at least ° C, more preferably by at least 3 ° C.
If the melting point of the first crystalline polymer is lower than the melting point of the second crystalline polymer, a sufficient flow rate cannot be obtained, and the filtration efficiency may be significantly reduced.
The melting point indicates the peak position of the DSC chart obtained by measuring with a differential scanning calorimeter, and when it has two peaks, or when it has one peak and one shoulder, The higher peak intensity is defined as the melting point.

The temperature of the endothermic peak position in the DSC chart corresponding to the melting point of the first crystalline polymer is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 343 ° C to 350 ° C. .
The temperature of the endothermic peak position in the DSC chart corresponding to the melting point of the second crystalline polymer is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 320 ° C to 338 ° C. .

The crystalline polymer is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include polyalkylene, polyester, polyamide, polyether, and crystalline polymer. Specifically, polyethylene, Polypropylene, polytetrafluoroethylene, polytetrafluoroethylene copolymer, nylon, polyacetal, polybutylene terephthalate, polyethylene terephthalate, syndiotactic polystyrene, polyphenylene sulfide, polyetheretherketone, wholly aromatic polyamide, wholly aromatic polyester, A fluororesin, polyether nitrile, etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together.
Among these, polytetrafluoroethylene and polytetrafluoroethylene co-polymers are easy to obtain powdery products having high crystallinity, have high solvent resistance and heat resistance, and can be suitably used for various applications. Polymers are preferred.

As the polytetrafluoroethylene, polytetrafluoroethylene produced by an emulsion polymerization method can usually be used, and a fine powdery polytetrafluoropolymer obtained by coagulating an aqueous dispersion obtained by emulsion polymerization. It is preferred to use ethylene.
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. Examples thereof include a copolymer obtained by copolymerizing at least two kinds.

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 glass transition temperature of the said crystalline polymer, Although it can select suitably according to the objective, -100 to 400 degreeC is preferable and -90 to 350 degreeC is more 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. . The number average molecular weight can be measured by, for example, gel permeation chromatography (GPC). However, since PTFE is insoluble in a solvent, the crystallization heat [ΔHc: cal / g] by DSC measurement is used. It is preferable to perform measurement and calculate using the relational expression: Mn = 2.1 × 10 ¹⁰ × ΔHc ^−5.16 .

  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 and 10,000-10,000,000 are More preferred. The weight average molecular weight can be measured and calculated by the same method as the number average molecular weight.

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, trade name “Polyflon PTFE”, product name “F-106”) is preferable in that it is easy to obtain a molded product having a relatively low molding pressure and excellent strength. Polytetrafluoroethylene (manufactured by Daikin Industries, Ltd., trade name “Polyflon PTFE”, product number “F-205”) is preferable from the viewpoint of refining the pore diameter after stretching.

  There is no restriction | limiting in particular as said other component, According to the objective, it can select suitably, For example, an extrusion aid is mentioned. There is no restriction | limiting in particular as said extrusion aid, Although it can select suitably according to the objective, It is preferable to use liquid lubricants, such as solvent naphtha and white oil. As a commercial item of the said extrusion adjuvant, hydrocarbon oil (The Esso Petroleum Corporation make, brand name "Isopar") etc. are mentioned, for example. There is no restriction | limiting in particular as addition amount of the said extrusion adjuvant, Although it can select suitably according to the objective, 15 mass parts-30 mass parts are preferable with respect to 100 mass parts of said crystalline polymers.

  There is no restriction | limiting in particular as a method of producing the said preforming body, According to the objective, it can select suitably, For example, (1) Kneading | mixing the said 1st crystalline polymer and the said extrusion adjuvant with a kneader. A method for producing a preform by spreading the paste formed in a mold and pressurizing, (2) kneading the first crystalline polymer, the second crystalline polymer, and the extrusion aid Examples include a method of preparing a laminated preform by spreading a paste kneaded by a machine in a mold and pressurizing.

  The mold used for producing the preform is not particularly limited and can be appropriately selected depending on the purpose. For example, a plastic mold, a press mold, a die casting mold, a casting mold, Forging dies are included.

The average thickness of the preform is set according to an extrusion method or a rolling method described later. In other words, when it is set according to the extrusion method, it is produced according to the dimensions of the preformed body input part of the extrusion device, and when it is set according to the rolling method, it is generally shaped according to the inlet shape of the rolling device. Is determined.
The average thickness of the preform is not particularly limited and may be appropriately selected according to the purpose. If a known example is shown, the preform may be set according to the extrusion method. The average thickness is, for example, 5 cm to 10 cm, and the average thickness of the preform in the case of being set in accordance with the rolling method is, for example, 0.5 cm to 5 cm.

<Extrusion process>
The extruding step includes a preformed body charging part for charging the preformed body, a throttle part connected to the downstream side of the preformed body charging part, a downstream part of the throttle part, and a central angle is A step of extruding the preform into a sheet using an extrusion device having a fan portion of 30 ° or more and less than 80 ° and an exit width of 200 mm or more and a drawing ratio of 50 or more. is there. In the extruding step, the items described in “Polyfluorocarbon Handbook” (issued by Daikin Industries, Ltd., revised in 1983) can be appropriately employed.

The drawing ratio is a ratio between the maximum cross-sectional area in the direction orthogonal to the extrusion direction and the minimum cross-sectional area in the direction perpendicular to the extrusion direction in the drawing part (“Reduction Ratio (RR)”, “ Sometimes referred to as “reduction ratio”). Moreover, if the said drawing ratio is shown using FIG. 5, in the cross-sectional area A1 of the preforming body injection | throwing-in part which throws in the preforming body in an extrusion apparatus, and the throttle part connected to the downstream in a preforming body injection | throwing-in part It means the ratio (A1 / A2) to the minimum cross-sectional area A2.
The aperture ratio is not particularly limited as long as it is 50 or more, and can be appropriately selected according to the purpose, but is preferably 50 or more and less than 800, more preferably 60 or more and less than 600, and particularly preferably 100 or more and less than 300. preferable.
When the drawing ratio is within the preferred range, the preform can be extruded while applying high shear to all of the feeding direction, thickness direction, and width direction without excessive press pressure, Since a sheet made of a tough crystalline polymer can be obtained, it becomes possible to produce a crystalline polymer microporous film having an average thickness of 50 μm or less only by extrusion and rolling with a calender roll, which has been considered impossible in the past. Within the particularly preferred range, it is advantageous in that it becomes remarkable.

If the center angle of the fan part is shown using FIG. 5, the angle formed by the extrusion direction (indicated by the white arrow in FIG. 5) and one end part 3A inclined from the extrusion direction and the other end part 3B. Say.
The central angle of the fan part is not particularly limited as long as it is 30 ° or more and less than 80 °, and can be appropriately selected according to the purpose, but is preferably 30 ° or more and 75 ° or less, and 40 ° or more and 60 °. The following is more preferable. If the center angle is excessively wide, the sheet is liable to be torn, and if it is excessively narrow, a long mold is required to give the lateral deformation necessary to give shear, and the extrusion pressure is increased. In some cases, the extrusion pressure cannot be used.

The outlet width of the fan part refers to the outlet opening length or width 7 of the fan part, as shown in FIG. 5, and refers to the width in which the width direction of the downstream outlet in the fan part has a constant value.
The exit width of the fan part is not particularly limited as long as it is 200 mm or more, and can be appropriately selected according to the purpose, but is preferably 200 mm or more and 600 mm or less, and particularly preferably 250 mm or more and 400 mm or less. If the outlet width is insufficient, sufficient shearing cannot be applied, and if the outlet width is excessively wide, the sheet may be torn or the extrusion pressure may be excessive to cause proper extrusion.
When the center angle and the exit width of the fan part are within the preferred range, it becomes possible to apply a higher shearing force in the width direction to the preformed body in addition to the shearing effect of the drawing ratio, Since a sheet made of a tough crystalline polymer can be obtained, it becomes possible to produce a crystalline polymer microporous film having an average thickness of 50 μm or less only by extrusion and rolling with a calender roll, which has been considered impossible in the past. Within the particularly preferred range, it is advantageous in that it becomes remarkable.

If the average thickness of the downstream exit in the said fan part is shown using FIG. The thickness of the sheet-like molded body obtained by extrusion can be defined by the average thickness of the lower portion of the outlet of the extrusion apparatus. By appropriately setting the thickness of the sheet-like molded body, the extrusion process and the rolling process can be further performed. It can be done smoothly.
There is no restriction | limiting in particular as average thickness of the downstream exit in the said fan part, Although it can select suitably according to the objective, 0.5 mm or more and 3.0 mm or less are preferable, and 1.0 mm or more and 2.5 mm or less are more. preferable.
If the average thickness of the downstream outlet in the fan portion is within the preferred range, the preform can be extruded with high shear and smoothly, and a sheet made of a tough crystalline polymer can be obtained. A crystalline polymer microporous film having an average thickness of 50 μm or less can be produced only by extrusion and calender roll, which has been considered impossible in the past. Is advantageous.

The extrusion speed of the preform in the extrusion apparatus is defined by the average value of the components in the extrusion axial direction of the speed of the paste passing through the squeezing portion, and is not particularly limited and can be appropriately selected according to the purpose. However, 0.5 m / min to 10.0 m / min is preferable, 0.6 m / min to 8.0 m / min is more preferable, and 0.7 m / min to 5.0 m / min is particularly preferable.
If the extrusion speed is within the preferable range, the preform can be extruded with high shear and smoothness, and a sheet made of a tough crystalline polymer can be obtained. Further, it is possible to produce a crystalline polymer microporous membrane having an average thickness of 50 μm or less only by extrusion and calender roll rolling, and it is advantageous in that it is remarkable if it is within the particularly preferred range.

There is no restriction | limiting in particular as extrusion temperature in the said extrusion process, Although it can carry out according to the well-known extrusion method and it can select suitably according to the objective, From the point of shape stability, 30 degreeC or more and 60 ° C or lower is preferable, and 35 ° C or higher and 60 ° C or lower is more preferable.
When the temperature is within the preferred range, the preform can be extruded with high shear and smoothness, and a sheet made of a tough crystalline polymer can be obtained. A crystalline polymer microporous membrane having an average thickness of 50 μm or less can be produced only by extrusion and rolling with a calender roll, and if it is within the particularly preferred range, it is advantageous in that it becomes remarkable.

There is no restriction | limiting in particular as average thickness of the sheet | seat which consists of a crystalline polymer obtained by the said extrusion process, Although it can select suitably according to the objective, 0.5 mm or more and 3.0 mm or less are preferable, and 1. 0 mm to 2.5 mm is more preferable.
If the average thickness is within the preferred range, the preform can be extruded with high shear and smoothness, and a sheet made of a tough crystalline polymer can be obtained. Further, it is possible to produce a crystalline polymer microporous membrane having an average thickness of 50 μm or less only by extrusion and calender roll rolling, and it is advantageous in that it is remarkable if it is within the particularly preferred range.

The sheet made of the crystalline polymer obtained by the extrusion process is applied with high shear in all directions of the feeding direction, the width direction, and the thickness direction, and becomes a sheet made of a tough crystalline polymer, and the toughness is It can be expressed by strength at a specified tensile magnification.
The 1,000% tensile strength in the width direction of the sheet made of the crystalline polymer obtained by the extrusion process is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 6 MPa or more, preferably 8 MPa or more. Is more preferable.

<Rolling process>
The rolling step is a step of rolling a sheet made of a crystalline polymer obtained by the extrusion step. Since the crystalline polymer sheet is tough, a crystalline polymer microporous film having an average thickness of 50 μm or less can be produced only by extrusion and rolling with a calender roll, which have been considered impossible in the past.

  There is no restriction | limiting in particular as the method of rolling, According to the objective, it can select suitably, For example, the method of rolling by applying a pressure with a pair of upper and lower calendar rolls and carrying out calendaring is mentioned. By the rolling method, a crystalline polymer microporous film having an average thickness of 50 μm or less can be preferably produced.

The sheet temperature at the time of rolling is not particularly limited and may be appropriately selected depending on the purpose. However, the lower limit is mainly the maintenance of sheet flexibility, and the upper limit is a range in which the molding aid used is less volatile. 30 ° C to 100 ° C is preferable, 40 ° C to 80 ° C is more preferable, and 50 ° C to 70 ° C is particularly preferable.
The calendering speed at the time of rolling is not particularly limited and may be appropriately selected depending on the intended purpose. The feed speed of the upper and lower calender rolls is preferably 0.5 m / min to 40 m / min, and 1 m / M to 20 m / min is more preferable, and 2 m / min to 10 m / min is particularly preferable.
There is no restriction | limiting in particular as an average pressure concerning the sheet | seat which consists of the said crystalline polymer at the time of the said rolling, According to the apparatus to be used, it can select suitably, For example, 30 MPa-150 MPa are mentioned.
By setting these temperature, rolling speed, and average pressure, a crystalline polymer microporous film having an average thickness of 50 μm or less can be preferably produced.

<Other processes>
There is no restriction | limiting in particular as said other process, According to the objective, it can select suitably, For example, an extending process and a heating process are mentioned suitably, Furthermore, an extrusion auxiliary agent removal process, surface modification are further needed as needed. Quality process and the like.

-Stretching process-
The stretching step is a step of stretching the crystalline polymer microporous film obtained by the rolling step in at least a uniaxial direction. By the stretching, a dense pore structure and a high porosity suitable as a microporous membrane can be imparted to the membrane.
There is no restriction | limiting in particular as the said extending | stretching method, Although it can select suitably according to the objective, The method of extending | stretching about both a longitudinal direction and the width direction is preferable, and performing each extending | stretching sequentially about a longitudinal direction and the width direction, respectively. In such a case, a method in which stretching in the longitudinal direction is performed first and then stretching in the width direction is more preferable. The stretching may be performed sequentially in the longitudinal direction and the width direction, or may be performed biaxially at the same time.

The stretching ratio in the longitudinal direction in the stretching step is not particularly limited and may be appropriately selected depending on the purpose, but is preferably 1.2 times to 50 times, more preferably 1.5 times to 40 times, 2 to 10 times is particularly preferable.
There is no restriction | limiting in particular as the extending | stretching temperature of the longitudinal direction in the said extending process, Although it can select suitably according to the objective, 35 to 330 degreeC is preferable, 45 to 320 degreeC is more preferable, 55 to 310 degreeC. ° C is particularly preferred.

There is no restriction | limiting in particular as the draw ratio of the width direction in the said extending process, Although it can select suitably according to the objective, 1.2 times-50 times are preferable, 1.5 times-40 times are more preferable, 2 to 30 times are more preferable, and 2.5 to 10 times are particularly preferable.
There is no restriction | limiting in particular as the extending | stretching temperature of the width direction in the said extending process, Although it can select suitably according to the objective, 35 to 330 degreeC is preferable, 45 to 320 degreeC is more preferable, 60 to 310 degreeC. ° C is particularly preferred.

  The area stretching ratio in the stretching step is not particularly limited and can be appropriately selected according to the purpose, but is preferably 1.5 to 2,500 times, more preferably 2 to 2,000 times, 2.5 to 100 times is particularly preferable. When the stretching is performed, the crystalline polymer microporous membrane may be preheated to a temperature equal to or lower than the stretching temperature. In addition, after the said extending | stretching, heat setting can be performed as needed. The temperature for heat setting is not particularly limited and may be appropriately selected depending on the intended purpose. However, it is preferably performed at a temperature equal to or higher than the stretching temperature and lower than the melting point of the crystalline polymer. The crystalline polymer is a fluorine such as PTFE. In the case of a resin, it is preferably carried out at a melting point or higher.

-Heating process-
The heating step is a step of heating the crystalline polymer microporous film obtained by the stretching step at a temperature equal to or higher than the melting point of the crystalline polymer. By heating, a microporous membrane having a fine structure containing short fibrils having an average major axis length of 1 μm or less is obtained, the pore size of the microporous membrane is reduced, and smaller particles can be captured efficiently. A crystalline polymer microporous membrane can be obtained.

  The heating method is not particularly limited as long as the layer containing the crystalline polymer can be uniformly and uniformly heated, and can be appropriately selected according to the purpose. For example, a salt bath, a hot air heater, a furnace, a roll, an infrared ray (IR) The method of heating with a heating apparatus etc. is mentioned. Among these, the method of heating with a salt bath is preferable in that it is possible to suppress variation in heating when the entire laminate is heated.

  There is no restriction | limiting in particular as said heating temperature, Although it can select suitably according to the objective, The temperature below melting | fusing point of said 1st crystalline polymer (high melting crystalline polymer) is the point of high flow volume. Is preferred. The temperature of the endothermic peak position in the DSC chart corresponding to the melting point of the high-melting crystalline polymer is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 343 ° C to 350 ° C. .

-Extrusion aid removal process-
The extrusion auxiliary agent removing step is a step of removing the extrusion auxiliary agent by heating the crystalline polymer microporous film obtained by the rolling step.
There is no restriction | limiting in particular as heating temperature in the said extrusion adjuvant removal process, Although it can select suitably according to the kind of extrusion adjuvant to be used, 40 to 400 degreeC is preferable and 60 to 350 degreeC is more preferable. In the case where polytetrafluoroethylene is used as the crystalline polymer and solvent naphtha is used as the extrusion aid, the heating temperature in the extrusion aid removal step is preferably 150 ° C. to 280 ° C., preferably 180 ° C. to 260 ° C. More preferred.
Examples of the heating method in the extruding auxiliary agent removing step include a method of heating the sheet made of the crystalline polymer by passing it through a hot air drying furnace.

-Surface modification process-
The surface modification step is a step of surface modifying at least a part of the crystalline polymer microporous film obtained by the stretching step. In addition to the exposed surface of the crystalline polymer microporous membrane, at least a part of the crystalline polymer microporous membrane includes 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, the surface modification may be performed by irradiating with a laser after impregnation with an aqueous solution of hydrogen peroxide or an aqueous solvent. (See JP-A-7-304888, etc.), method for surface modification by irradiation with radiation, plasma, etc. (see JP-A-2003-201571 etc.), method for surface modification by chemical etching treatment (See Japanese Patent Application Laid-Open No. 2007-154153, etc.), a method of modifying the surface by coating with a crosslinking material (see Japanese Patent Application Laid-Open No. 8-283447, etc.), a method of modifying the surface by coating with a polymerization material. (See JP 2000-235849 A).

  Here, with reference to FIGS. 1-5, an example of the manufacturing method of the crystalline polymer microporous film | membrane of this invention is demonstrated. As shown in FIG. 1, the 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). Thereby, the first layer 4 is formed by being compressed. Next, as shown in FIG. 2, a paste 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. And after storing the obtained lamination | stacking preforming body 10 in the cylinder part of an extrusion apparatus as shown in FIG. 4, this is pressed to an arrow direction with a pressurization means (not shown). Further, the extrusion apparatus has a structure as shown in FIG. 5, and includes a preformed body charging unit 1, a throttle unit 2 connected to the preformed unit charging unit 1, and a fan unit connected to the throttle unit 2. 3. By such an extrusion apparatus, the first layer 4 and the second layer 5 are completely integrated, and the laminate 15 having a uniform thickness for each layer is formed. By rolling the laminate 15, the crystalline polymer microporous film of the present invention is produced.

(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 membrane is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the single-layer structure including a layer containing the first crystalline polymer, the first And a laminated structure including a layer containing the crystalline polymer and a layer containing the second crystalline polymer. In addition, there is no restriction | limiting in particular as a method to confirm that the said crystalline polymer microporous film | membrane is either a single layer structure or a laminated structure, According to the objective, it can select suitably, for example, crystallinity There is a method of confirming the cut surface obtained by freezing and cutting the polymer microporous film in the thickness direction with an optical microscope or a scanning electron microscope (SEM).

The structure of the crystalline polymer microporous film is not particularly limited and may be appropriately selected depending on the intended purpose. However, the structure includes two or more layers containing the first crystalline polymer and one layer of the second layer. A layered structure with a layer containing a crystalline polymer is preferable, and a first layer of a first layer interposed between two layers containing a first crystalline polymer and a layer containing the two first crystalline polymers. A three-layer structure having two layers containing a crystalline polymer is more preferable.
By making the structure of the crystalline polymer microporous film into the three-layer structure, the second crystalline polymer can be protected from physical destruction factors such as friction and scratching, and the capture performance is stabilized. This is advantageous in that it can be achieved. In addition, when the thickness of the layer containing the first crystalline polymer in the crystalline polymer microporous film is equal to or greater than the thickness of the layer containing the second crystalline polymer, the flow rate characteristics are improved. The fine particle capture rate is reduced, and the thickness of the layer containing the first crystalline polymer in the crystalline polymer microporous film is less than the thickness of the layer containing the second crystalline polymer, Although the flow rate characteristic is lowered, the fine particle capture rate is improved.

  When the crystalline polymer microporous film has a two-layer structure, the ratio of the thickness of the layer containing the first crystalline polymer to the thickness of the layer containing the second crystalline polymer (the first crystalline polymer The thickness of the layer containing: the thickness of the layer containing the second crystalline polymer) is preferably 10,000: 1 to 1.2: 1, and 5,000: 1 to 1.25: 1. It is more preferable that the ratio is 1,000: 1 to 1.5: 1. If the ratio is more than 10,000: 1, the thickness of the layer containing the second crystalline polymer may not be precisely controlled, and if it is less than 1.2: 1, the second crystallinity The layer containing the polymer may be affected by friction and scratching, and may not be able to maintain a stable particulate capturing property. 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 crystalline polymer microporous membrane has a three-layer structure (two layers including a first crystalline polymer layer and one layer of a second layer interposed between the two layers including the first crystalline polymer layer). In the case of a three-layer structure having a layer containing a crystalline polymer of the first), the ratio of the maximum thickness of the layer containing the first crystalline polymer to the thickness of the layer containing the second crystalline polymer (first The maximum thickness of the layer containing the crystalline polymer: the thickness of the layer containing the second crystalline polymer) 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 crystalline polymer may not be precisely controlled, and if it is less than 1.2: 1, the second crystallinity The polymer-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 average thickness of the crystalline polymer microporous membrane is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 50 μm or less, more preferably 1 μm to 50 μm, still more preferably 5 μm to 50 μm, 10 μm to 50 μm is particularly preferable. The method for measuring the average thickness is not particularly limited and can be appropriately selected depending on the purpose. For example, the crystalline polymer microporous membrane is frozen and cut by a scanning electron microscope (SEM). By performing cross-sectional observation of each layer, the average thickness of each layer can be measured.

The layer containing the first crystalline polymer in the crystalline polymer microporous membrane is not particularly limited as long as it contains the first crystalline polymer, and can be appropriately selected according to the purpose.
The maximum thickness of the layer containing the first crystalline polymer in the crystalline polymer microporous membrane is thicker than the maximum thickness of the layer containing the second crystalline polymer. Thereby, the flow rate of the crystalline polymer microporous membrane can be improved. Here, the “maximum thickness” means the maximum value of the thickness of each layer. For example, a laminate having a layer containing a first crystalline polymer having a thickness of 20 μm, a layer containing a first crystalline polymer having a thickness of 15 μm, and a layer containing a first crystalline polymer having a thickness of 10 μm In this case, the maximum thickness of the layer containing the first crystalline polymer is 20 μm, the layer containing the second crystalline polymer having a thickness of 20 μm, and the layer containing the second crystalline polymer having a thickness of 15 μm, In the case of a laminate having a second crystalline polymer-containing layer having a thickness of 10 μm, the maximum thickness of the layer containing the second crystalline polymer is 20 μm.

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, in the case of a laminated structure, the first crystalline polymer is included. The average pore diameter of the pores in the layer and the average pore diameter of the pores in the layer containing the second crystalline polymer have different average pore diameters.
There is no restriction | limiting in particular as an average hole diameter of the hole part in the layer containing the 1st crystalline polymer of the said crystalline polymer microporous film | membrane, Although it can select suitably according to the objective, It is 1 micrometer or less. Preferably, it is 0.5 μm or less.
The average pore diameter of the pores in the layer containing the second crystalline polymer of the crystalline polymer microporous membrane is not particularly limited and can be appropriately selected according to the purpose, but is preferably 1 nm to 200 nm, 5 nm to 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 : Ratok System Engineering Co., Ltd., trade name “TV Image Processor Image Command 4198”) to obtain an image consisting only of crystalline polymer fibers, and processing the image to calculate the average pore diameter. 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.
There is no restriction | limiting in particular as an average flow volume diameter of the hole part in the layer containing the 1st crystalline polymer of the said crystalline polymer microporous film | membrane, Although it can select suitably according to the objective, It is 1 micrometer or less. Is preferable, and it is more preferable that it is 0.5 micrometer or less.
The average flow pore size of the pores in the layer containing the second crystalline polymer 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. 5 nm to 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, when the average flow pore diameter exceeds 15 nm, it can be measured with a 500 psi high-pressure palm porometer (manufactured by PMI). When the average flow pore diameter is 15 nm or less, the nano palm porometer (Manufactured by PMI).

  Here, an example of the crystalline polymer microporous membrane of the present invention will be described with reference to FIGS. As shown in FIG. 6, 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. 7, the average pore diameters of the holes 101b, 102b, and 103b in the crystalline polymer microporous membrane of the present invention having a three-layer structure in which the layers 101, 102, and 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. Further, a layer 102 containing a second crystalline polymer having the smallest maximum average pore diameter Lm2 among the maximum average pore diameters Lm1, Lm2 and Lm3 of the pores is formed inside the crystalline polymer microporous film (laminate). Existing. It is preferable to have a layer containing a crystalline polymer having a low melting point in which the maximum average pore diameter of the pores is the smallest in a laminate formed by laminating three or more layers containing a crystalline polymer. As a result, the layer containing the crystalline polymer having the smallest average pore diameter that most affects the trapped particle diameter can be protected from physical destruction factors such as friction and scratching, and the trapping performance can be stabilized. It can be manufactured stably.

  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. It can be used, and can be used particularly suitably as a filter for filtration described below.

(Filter for filtration)
The filtering filter of the present invention uses the crystalline polymer microporous membrane. And since the specific surface area of the said crystalline polymer microporous film | membrane is large, the fine particle introduce | transduced from the surface is removed by adsorb | sucking or adhering before reaching | attaining a minimum pore diameter part. 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. 8-10, an example of the filter for filtration of this invention is demonstrated.
8 to 10 are specific examples of the microfiltration filter cartridge, and the present invention is not limited to these drawings.

  FIG. 8 is a development view showing the structure of an element exchange type pleated filter cartridge element. The microfiltration membrane 113 is folded in a state of being sandwiched by two membrane supports 112 and 114, and is wound around a core 115 having a large number of liquid collection ports. 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. 9 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 and folded around a filter element core 27 having a large number of liquid collection ports while being sandwiched between two primary supports 21 and secondary supports 23. Outside the filter element cover 26 is protecting the microfiltration membrane. A microfiltration membrane is sealed at both ends of the cylinder by an upper end plate 24 and a lower end plate 25. FIG. 9 shows an example in which the lower end plate 25 and the housing base are sealed through 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. 10 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, 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
<Manufacture of crystalline polymer microporous membrane (single layer)>
-Preliminary body manufacturing process-
Polytetrafluoroethylene fine powder as a crystalline polymer (trade name “Polyflon PTFE”, product name “F-106”, manufactured by Daikin Industries, Ltd.) 100 parts by mass, and hydrocarbon oil (Esso Oil Co., Ltd.) as an extrusion aid Product, trade name “Isopar H”) 23 parts by mass, and left in a room kept at 30 ° C. for 12 hours to obtain paste 1. Next, the paste 1 was spread in a mold having the shape shown in FIG. 1 and pressed with a pressure of 0.5 MPa to produce a sheet-like preform.

-Extrusion process-
The preform was extruded into a sheet using a hard iron extrusion device having the shape shown in FIG. 5 to produce a sheet made of a crystalline polymer. In the extrusion apparatus, the drawing ratio was 50, the center angle was 60 °, and the outlet width of the fan part was 200 mm. The drawing ratio refers to the ratio (A1 / A2) between the cross-sectional area A1 of the preformed body input portion and the minimum cross-sectional area A2 of the drawn portion in the extrusion apparatus shown in FIG. 5 refers to the angle formed by one end 3A and the other end 3B in the extrusion apparatus shown in FIG. 5, and the outlet width of the fan section refers to the width indicated by reference numeral 7 in the extrusion apparatus shown in FIG.

-Rolling process-
The sheet made of the crystalline polymer obtained in the extrusion step is calendered once in the longitudinal direction by a calender roll heated to 60 ° C., and the obtained sheet is passed through a hot air drying furnace at 250 ° C. to provide an extrusion aid. Was removed by drying. Thus, a crystalline polymer microporous membrane having an average thickness of 40 μm, an average width of 200 mm, and a specific gravity of 1.45 was produced. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Example 2)
<Manufacture of crystalline polymer microporous membrane (single layer)>
A crystalline polymer microporous membrane having an average thickness of 40 μm, an average width of 200 mm, and a specific gravity of 1.45 was prepared in the same manner as in Example 1 except that the central angle of the extrusion apparatus in the extrusion process of Example 1 was set to 75 °. did. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Example 3)
<Manufacture of crystalline polymer microporous membrane (single layer)>
A crystalline polymer microporous membrane having an average thickness of 40 μm, an average width of 200 mm, and a specific gravity of 1.45 is prepared in the same manner as in Example 1 except that the central angle of the extrusion apparatus in the extrusion process of Example 1 is 32 °. did. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

Example 4
<Manufacture of crystalline polymer microporous membrane (single layer)>
A crystalline polymer microporous membrane having an average thickness of 40 μm, an average width of 200 mm, and a specific gravity of 1.45 was prepared in the same manner as in Example 1 except that the drawing ratio of the extrusion apparatus in the extrusion process of Example 1 was set to 100. . The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Example 5)
<Manufacture of crystalline polymer microporous membrane (single layer)>
Crystalline polymer micropores with an average thickness of 60 μm, an average width of 200 mm, and a specific gravity of 1.45, except that the conditions of the rolling process of Example 1 were adjusted to make the film thickness 60 μm. A conductive film was prepared. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Example 6)
<Manufacture of crystalline polymer microporous membrane (single layer / uniaxial stretching)>
The crystalline polymer microporous membrane obtained in Example 1 was stretched 3 times in the longitudinal direction using a roll stretching machine to obtain a uniaxially stretched crystalline polymer microporous membrane. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Example 7)
<Manufacture of crystalline polymer microporous membrane (single layer, biaxial stretching)>
The crystalline polymer microporous membrane obtained in Example 1 was stretched 3 times in the longitudinal direction using a roll stretching machine, and then stretched 3 times in the width direction using a pantograph stretching machine. A crystalline polymer microporous membrane stretched about the axis was obtained. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Example 8)
<Production of crystalline polymer microporous membrane (single layer, uniaxial stretching, heat setting)>
The uniaxially stretched crystalline polymer microporous membrane obtained in Example 6 was heated in a 320 ° C. oven with the clip fixed to a metal frame, and stretched and heat-treated. A crystalline polymer microporous membrane was obtained. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

Example 9
<Production of crystalline polymer microporous membrane (single layer, biaxial stretching, heat setting)>
The biaxially stretched crystalline polymer microporous membrane obtained in Example 7 was put into a 320 ° C. oven in a state of being fixed to a metal frame with a clip and heat-treated, and stretched / heat-treated. A crystalline polymer microporous membrane was obtained. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Example 10)
<Manufacture (lamination) of crystalline polymer microporous membrane>
-Preliminary body manufacturing process-
Polytetrafluoroethylene fine powder (Daikin Kogyo Co., Ltd., trade name “Polyflon PTFE”, product name “F106”) 100 parts by mass as a highly crystalline polymer, and hydrocarbon oil (Esso Oil Co., Ltd.) as an extrusion aid , Trade name “Isopar H”) was added 23 parts by mass, and the mixture was allowed to stand in a room kept at 30 ° C. for 12 hours to obtain paste 1. Polytetrafluoroethylene fine powder (trade name “Polyflon PTFE”, product name “F205”, manufactured by Daikin Industries, Ltd.) 100 parts by mass as a low crystalline polymer, hydrocarbon oil (Esso Oil Co., Ltd.) as an extrusion aid 20 parts by mass (product name “Isopar H”) was added, and the mixture was allowed to stand in a room kept at 30 ° C. for 12 hours to obtain paste 2. Next, paste 1 and paste 2 are spread in a mold having the shape shown in FIG. 1 so that the thickness ratio (paste 1 / paste 2 / paste 1) is 8/1/1. Pressurization was performed at a pressure of 5 MPa to prepare a sheet-like laminated preform.

-Extrusion process-
Using the extruder, the preform was extruded into a sheet shape to produce a sheet made of a crystalline polymer. In the extrusion apparatus, the drawing ratio was 50, the central angle was 60 °, and the outlet width of the fan part was 200 mm.

-Rolling process-
The sheet made of the crystalline polymer obtained in the extrusion step is calendered once in the longitudinal direction by a calender roll heated to 60 ° C., and the obtained sheet is passed through a hot air drying furnace at 250 ° C. to provide an extrusion aid. Was removed by drying. Thus, a crystalline polymer microporous membrane having an average thickness of 40 μm, an average width of 200 mm, and a specific gravity of 1.45 was produced. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Example 11)
<Manufacture of crystalline polymer microporous membrane (lamination, biaxial stretching, heat setting)>
The crystalline polymer microporous film obtained in Example 10 was subjected to the stretching process of Example 7 and the heating process of Example 9 in order, and the crystallinity of the laminated structure that was biaxially stretched and then heat-treated. A polymer microporous membrane was obtained. The crystalline polymer microporous membrane contained a PTFE copolymer and had an extremely smooth and uniform color appearance. The manufacturing conditions are shown in Table 1.

(Example 12)
<Production of crystalline polymer microporous membrane (single layer, biaxial stretching, heat setting)>
The crystalline polymer microporous membrane obtained in Example 5 was subjected to the stretching process described in Example 7 and the heating process described in Example 9 in order, and the film was processed biaxially and then heat-treated. A crystalline polymer microporous membrane having a layer structure was obtained. The crystalline polymer microporous membrane contained a PTFE copolymer and had an extremely smooth and uniform color appearance. The manufacturing conditions are shown in Table 1.

(Example 13)
<Manufacture of crystalline polymer microporous membrane (single layer / multistage rolling)>
In the rolling process of Example 1, the average thickness of the sheet made of the crystalline polymer was rolled in order of 1,000 μm, 700 μm, and 40 μm in order by a calendar of 3 times, in the same manner as in Example 1, A crystalline polymer microporous membrane having a thickness of 40 μm, an average width of 200 mm, and a specific gravity of 1.45 was prepared. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Example 14)
<Manufacture of crystalline polymer microporous membrane (single layer / single rolling)>
In the rolling process of Example 1, an average thickness of 25 μm and an average width of 200 mm were obtained in the same manner as in Example 1 except that rolling was performed so that the average thickness of the crystalline polymer sheet was 25 μm by one calendaring. A crystalline polymer microporous membrane having a specific gravity of 1.45 was prepared. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Example 15)
<Manufacture of crystalline polymer microporous membrane (single layer, symmetrical heating, heat setting)>
The microporous membrane of Example 1 was heated by a salt bath kept at 341 ° C. for 50 seconds to symmetrically heat the laminate. Furthermore, after extending | stretching between rolls 3 times in a longitudinal direction at 300 degreeC, after winding up to a winding roll once, both ends were pinched | interposed with the clip and it extended | stretched 3 times in the width direction at 300 degreeC. Thereafter, heat setting was performed at 320 ° C. to produce a crystalline polymer microporous membrane having an average thickness of 21 μm, an average width of 450 mm, and a specific gravity of 0.70. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Example 16)
<Manufacture of crystalline polymer microporous membrane (single layer, multi-stage rolling, symmetrical heating, heat setting)>
The microporous membrane of Example 13 is subjected to symmetrical heating, stretching, and heat setting in the same manner as in Example 15 to produce a crystalline polymer microporous membrane having an average thickness of 25 μm, an average width of 450 mm, and a specific gravity of 0.70. did. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Example 17)
<Manufacture of crystalline polymer microporous membrane (single layer, one-step rolling, symmetrical heating, heat setting)>
The microporous membrane of Example 14 was subjected to symmetrical heating, stretching, and heat setting in the same manner as in Example 15 to produce a crystalline polymer microporous membrane having an average thickness of 15 μm, an average width of 450 mm, and a specific gravity of 0.70. did. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Example 18)
<Manufacture of crystalline polymer microporous membrane (lamination, symmetrical heating, heat setting)>
The microporous membrane of Example 10 is subjected to symmetrical heating, stretching, and heat setting in the same manner as in Example 15 to produce a crystalline polymer microporous membrane having an average thickness of 23 μm, an average width of 450 mm, and a specific gravity of 0.70. did. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Comparative Example 1)
<Manufacture of crystalline polymer microporous membrane (single layer)>
A crystalline polymer microporous membrane having an average thickness of 40 μm, an average width of 200 mm, and a specific gravity of 1.45 is prepared in the same manner as in Example 1 except that the central angle of the extrusion apparatus in the extrusion process of Example 1 is 82 °. Attempts were made to tear in parallel with the web feed direction during rolling, but a uniform microporous film could not be obtained. The manufacturing conditions are shown in Table 1.

(Comparative Example 2)
<Manufacture of crystalline polymer microporous membrane (single layer)>
A crystalline polymer microporous membrane having an average thickness of 40 μm, an average width of 200 mm, and a specific gravity of 1.45 is prepared in the same manner as in Example 1 except that the central angle of the extrusion apparatus in the extrusion process of Example 1 is 25 °. However, the web obtained by the extrusion process was distorted in a wavy shape, and a uniform microporous film could not be obtained. The manufacturing conditions are shown in Table 1.

(Comparative Example 3)
<Manufacture of crystalline polymer microporous membrane (single layer, different drawing ratio)>
A crystalline polymer microporous membrane having an average thickness of 40 μm, an average width of 200 mm, and a specific gravity of 1.45 is prepared in the same manner as in Example 1 except that the drawing ratio of the extrusion apparatus in the extrusion process of Example 1 is 45. However, the web was broken during rolling, and rolling could not be performed, so that a microporous film could not be obtained. The manufacturing conditions are shown in Table 1.

(Comparative Example 4)
<Manufacture of crystalline polymer microporous membrane (single layer, different drawing ratio)>
A crystalline polymer microporous membrane having an average thickness of 40 μm, an average width of 200 mm, and a specific gravity of 1.45 is prepared in the same manner as in Example 1 except that the drawing ratio of the extrusion apparatus in the extrusion process of Example 1 is set to 10. However, the web was broken during rolling, and rolling could not be performed, so that a microporous film could not be obtained. The manufacturing conditions are shown in Table 1.

(Comparative Example 5)
<Production of crystalline polymer microporous membrane (single layer, different exit width)>
A crystalline polymer microporous membrane having an average thickness of 40 μm, an average width of 150 mm, and a specific gravity of 1.45 will be produced in the same manner as in Example 1 except that the exit width of the extrusion apparatus in the extrusion process of Example 1 is 150 mm. However, during the rolling, tearing occurred in parallel with the web feeding direction, and a uniform microporous film could not be obtained. The manufacturing conditions are shown in Table 1.

(Comparative Example 6)
<Production of crystalline polymer microporous membrane (single layer, different exit width)>
A crystalline polymer microporous membrane having an average thickness of 40 μm, an average width of 180 mm, and a specific gravity of 1.45 will be produced in the same manner as in Example 1 except that the exit width of the extrusion apparatus in the extrusion process of Example 1 is 180 mm. However, during the rolling, tearing occurred in parallel with the web feeding direction, and a uniform microporous film could not be obtained. The manufacturing conditions are shown in Table 1.

(Comparative Example 7)
<Manufacture of crystalline polymer microporous membrane (single layer, no rolling)>
A crystalline polymer film having an average thickness of 2.5 mm, an average width of 200 mm, and a specific gravity of 1.45 was produced in the same manner as in Example 1 except that the rolling step of Example 1 was omitted. The appearance of the crystalline polymer film was extremely smooth and had a uniform color. The manufacturing conditions are shown in Table 1.

(Comparative Example 8)
<Manufacture of crystalline polymer microporous membrane (single layer, different central angle)>
The conditions of the rolling process of Comparative Example 1 were adjusted to produce a crystalline polymer microporous film having an average thickness of 55 μm, an average width of 200 mm, and a specific gravity of 1.45. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Comparative Example 9)
<Manufacture of crystalline polymer microporous membrane (single layer, uniaxial stretching, center angle difference)>
The crystalline polymer microporous membrane obtained in Comparative Example 8 was obtained in the same manner as in Example 6 to obtain a uniaxially stretched crystalline polymer microporous membrane. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Comparative Example 10)
<Production of crystalline polymer microporous membrane (single layer, biaxial stretching, center angle difference)>
The crystalline polymer microporous membrane obtained in Comparative Example 8 was obtained in the same manner as in Example 7 to obtain a biaxially stretched crystalline polymer microporous membrane. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Comparative Example 11)
<Manufacture of crystalline polymer microporous membrane (single layer, uniaxial stretching, heat setting, center angle difference)>
In the same manner as in Example 8, the crystalline polymer microporous membrane obtained in Comparative Example 8 was uniaxially stretched and then subjected to heat treatment to obtain a crystalline polymer microporous membrane. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Comparative Example 12)
<Manufacture of crystalline polymer microporous membrane (single layer, biaxial stretching, heat setting, center angle difference)>
In the same manner as in Example 9, the crystalline polymer microporous membrane obtained in Comparative Example 8 was biaxially stretched and then subjected to heat treatment to obtain a crystalline polymer microporous membrane. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Comparative Example 13)
<Manufacture of crystalline polymer microporous membrane (single layer, different drawing ratio, different central angle)>
In the extruding process of Example 1, a sheet made of the crystalline polymer by a single calendaring in the rolling process of Example 1 using an extruding device having a drawing ratio of 10, a center angle of 82 °, and a fan outlet width of 200 mm. A crystalline polymer microporous film having an average thickness of 100 μm, an average width of 200 mm, and a specific gravity of 1.45 was prepared in the same manner as in Example 1 except that the film was rolled so that the average thickness of the film became 100 μm. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Comparative Example 14)
<Manufacture of crystalline polymer microporous membrane (single layer, different drawing ratio, different central angle)>
In the extrusion process of Example 1, the same procedure as in Example 1 was conducted except that a laminated sheet made of a crystalline polymer was produced using an extrusion device having a drawing ratio of 10, a central angle of 82 °, and a fan part outlet width of 200 mm. Rolling with a calender roll resulted in innumerable cracking during calendering, and a crystalline polymer microporous film could not be produced. The manufacturing conditions are shown in Table 1.

(Comparative Example 15)
<Manufacture of crystalline polymer microporous membrane (single layer, multi-stage rolling, drawing ratio difference, center angle difference)>
Except for using the extrusion apparatus of Comparative Example 13, rolling was performed with a calender roll in the same manner as in Example 13, but innumerable cracks occurred during the third calendering, resulting in crystalline polymer micropores. A functional film could not be produced. The manufacturing conditions are shown in Table 1.

(Comparative Example 16)
<Manufacture of crystalline polymer microporous membrane (single layer, uniaxial stretching, drawing ratio difference, center angle difference)>
The microporous membrane of Comparative Example 13 was stretched between rolls three times in the longitudinal direction at 300 ° C., and then the crystalline polymer fine material having an average thickness of 42 μm, an average width of 200 mm, and a specific gravity of 0.70 without performing heat fixation A porous membrane was produced. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Comparative Example 17)
<Manufacture of crystalline polymer microporous membrane (single layer, multi-stage rolling, uniaxial stretching, drawing ratio difference, center angle difference)>
The microporous membrane of Comparative Example 16 was tried to produce a microporous membrane in the same manner as in Example 15. However, the membrane could not be produced due to breakage during transverse stretching. The manufacturing conditions are shown in Table 1.

(Comparative Example 18)
<Manufacture of crystalline polymer microporous membrane (single layer, uniaxial stretching, heat setting, drawing ratio difference, center angle difference)>
The microporous membrane of Comparative Example 16 was heat-set at 320 ° C. to produce a crystalline polymer microporous membrane. The appearance of the crystalline polymer microporous film had a very smooth and uniform color. The manufacturing conditions are shown in Table 1.

(Evaluation)
<Tensile strength>
For the crystalline polymer sheets before and after rolling in Examples 1 to 18 and Comparative Examples 1 and 3 to 18, using a tensile strength tester (manufactured by Shimadzu Corporation, Autograph AGS-J) in the width direction. The relationship between deformation and stress when the film was deformed was measured, and the stress in the 1,000% deformed state was calculated as the tensile strength. The results are shown in Table 2.

<Average pore size>
About the crystalline polymer microporous film | membrane of Examples 1-18 and Comparative Examples 7-13, 16 and 18, the average pore diameter was measured using the palm porometer (made by PMI). The results are shown in Table 3. In addition, the measurement lower limit of a palm porometer is 41 nm, and when the pore diameter could not be observed within the measurement range, “<41” was set. The results are shown in Table 2.

<Shape stability evaluation>
The crystalline polymer microporous membranes of Examples 1 to 18 and Comparative Examples 7 to 13, 16 and 18 were placed in a 200 ° C. blast heating furnace without restraining the shape, taken out after 1 hour and measured. The ratio of the dimensional change after the heat treatment to the original dimension was calculated as the heat shrinkage rate. The results are shown in Table 2.

<Breathability evaluation>
For the crystalline polymer microporous membranes of Examples 1 to 18 and Comparative Examples 7 to 13, 16 and 18, the dry membrane aeration rate was measured with a palm porometer (manufactured by PMI), and the microporosity of Example 1 was measured. On the basis of the membrane, the microporous membrane of Example 1 having a flow rate equal to or greater than the dry membrane aeration rate was marked with ◯, below that it was observed to be aerated, Δ, and a sample having no aeration itself marked with ×. The results are shown in Table 2.

Examples 1 to 18 of the present invention used an extrusion apparatus having a drawing ratio of 50 or more, a central angle of 30 ° or more and less than 80 °, and an exit width of 200 mm, so that the preform can be extruded with high shear, An extrudate having the desired strength could be obtained. The extrudate has high strength, and even when rolled to an average thickness of 50 μm or less, a uniform film can be obtained without breaking, and a crystalline polymer microporous film having useful air permeability is produced. I was able to. In addition, the crystalline polymer microporous membranes of Examples 1 to 18 had fine pores and a low heat shrinkage rate as compared with the conventional production method manufactured through the same process. Furthermore, a film having finer pores than the single layer structure could be obtained by using a laminated structure containing a low crystalline polymer as in Example 11.
On the other hand, in Comparative Examples 1 to 6, since an extrusion apparatus having a drawing ratio of less than 50, a central angle of 80 degrees or more, or an exit width of less than 200 mm was used, the preform was extruded with low shear, The desired strength was not obtained. For this reason, when it rolled so that average thickness might be 50 micrometers or less, the said extrudate broke. Moreover, the thick film | membrane which does not pass the rolling of the comparative example 7 was inferior to air permeability. Comparative Examples 8 to 12 are microporous films obtained by stretching or heat treatment using a microporous film obtained in the range of the rolling thickness at which the extrudate of Comparative Example 1 can be rolled, but with the same rolling thickness. The pore diameter is far inferior to the case of using the microporous membrane of Example 5 using an extrusion apparatus having a drawing ratio of 50 or more, a central angle of 30 ° or more and less than 80 °, and an exit width of 200 mm. Met.

  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.

DESCRIPTION OF SYMBOLS 1 Preliminary body injection | throwing-in part 2 Diaphragm | restriction part 3 Fan part 3A edge part 3B edge part 4 1st layer 5 2nd layer 6 Average thickness of the exit lower part of a fan part 7 Fan part exit width 8 Lower mold 10 Laminated preform DESCRIPTION OF SYMBOLS 15 Laminate body 21 Primary side support 22 Microfiltration membrane 23 Secondary side 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 first crystalline polymer 102 Layer containing second crystalline polymer 103 Layer containing first crystalline polymer 101b Hole portion 102b Hole portion 103b Hole portion 111 Outer peripheral cover 112 Membrane support 113 Microfiltration membrane 14 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 Maximum average hole diameter of the hole A1 Cross-sectional area of the preformed body input part A2 In the throttle part Minimum cross-sectional area

Claims (9)

A preform forming step of preparing a preform using a crystalline polymer;
A preformed body charging part for charging the preformed body, a throttle part connected to the downstream side of the preformed body charging part, a downstream part of the throttle part, and a center angle of 30 ° or more and 80 ° And an extrusion step of extruding the preform into a sheet using an extrusion device having a fan portion having an outlet width of 200 mm or more and a drawing ratio of 50 or more,
A rolling step of rolling a sheet made of a crystalline polymer obtained by the extrusion step;
A method for producing a crystalline polymer microporous membrane, comprising:   2. The method for producing a crystalline polymer microporous membrane according to claim 1, wherein a 1,000% tensile strength in the width direction of the sheet made of the crystalline polymer obtained by the extrusion step is 6 MPa or more.   The method for producing a crystalline polymer microporous membrane according to any one of claims 1 to 2, wherein the average thickness of the crystalline polymer microporous membrane is 50 µm or less by rolling the sheet in the rolling step.   The method for producing a crystalline polymer microporous membrane according to any one of claims 1 to 3, further comprising a stretching step of stretching the crystalline polymer microporous membrane obtained by the rolling step in at least one axial direction.   The method for producing a crystalline polymer microporous membrane according to claim 4, further comprising a heating step of heating the crystalline polymer microporous membrane obtained by the stretching step at a temperature equal to or higher than the melting point of the crystalline polymer.   The preform is formed by laminating a layer containing a first crystalline polymer and a layer containing a second crystalline polymer, and the melting point of the first crystalline polymer is that of the second crystalline polymer. The method for producing a crystalline polymer microporous membrane according to any one of claims 1 to 5, which is higher than the melting point.   A crystalline polymer microporous membrane produced by the method for producing a crystalline polymer microporous membrane according to any one of claims 1 to 6.   The crystalline polymer microporous membrane according to claim 7, having an average thickness of 50 μm or less.   A filter for filtration, comprising the crystalline polymer microporous membrane according to any one of claims 7 to 8.