JP2012172085A - Crystallizable polymer microporous membrane, method for manufacturing the same, and filtration filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crystallizable polymer microporous membrane that has a minute pore diameter, can efficiently catch fine particles of tens of nm size and has a high flux, to provide a method for manufacturing the crystallizable polymer microporous membrane that can consistently withstand stretching at a high magnification and to provide a filtration filter that has high resistance to pleat collapse.SOLUTION: The method for manufacturing a crystallizable polymer microporous membrane includes a preform making step of making a preform by using a crystallizable polymer, an extrusion step of extruding the preform into the form of a sheet by an extrusion apparatus having a preform introduction part, a drawing part connected to the preform introduction part and a sector part connected to the drawing part and having a central angle of not less than 80° to not more than 160°, a rolling step of multistage rolling the sheet formed of the crystallizable polymer produced through the extrusion step, and a stretching step of stretching the sheet formed of the crystallizable polymer produced through the rolling step.

Description

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

  Microporous membranes have been known for a long time, but in recent years, their use and use have been reduced as filtration filters for filtration and sterilization of electronic industrial cleaning water, pharmaceutical water, pharmaceutical manufacturing process water, food water, etc. A highly reliable microporous membrane is drawing attention.

  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, see Patent Document 3), a material using polypropylene as a raw material (see, for example, Patent Document 4), a material using polytetrafluoroethylene (hereinafter sometimes referred to as “PTFE”) (for example, a patent) Documents 5 and 6) are known. Among these, the crystalline polymer microporous membrane using PTFE as a raw material is excellent in heat resistance and chemical resistance, and therefore, the growth in demand is remarkable.

As the crystalline polymer microporous film using PTFE as a raw material, for example, a multilayer film formed by laminating each layer of a homopolytetrafluoroethylene polymer and a modified polytetrafluoroethylene copolymer has been proposed (for example, Patent Documents). 5 and 6). However, in the above proposal, since an extruding apparatus used for producing the multilayer film generates a high shearing force, a high-strength extrudate is formed, and cracking occurs in the stretching direction when stretching is performed at a high magnification. In some cases, it is difficult to form a stable film.
Therefore, in order to solve these problems, as a crystalline polymer microporous film made from the PTFE as a raw material, for example, by uniformizing strength and elongation at the stage of extrudate, PTFE having stable physical properties is obtained. A method of forming a sheet has been proposed (see, for example, Patent Document 7). However, in the above proposal, there is no description of the laminated structure, and there is a problem that it is difficult to stretch at a high magnification and it is difficult to produce a film having a minute pore size.

Therefore, a crystalline polymer microporous film having a fine pore diameter, capable of efficiently capturing fine particles of several tens of nanometers in size, and having a high flow rate, and a crystal that can stably withstand stretching at a high magnification. At present, there is a strong demand for rapid development of a method for producing a porous polymer microporous membrane.
In addition, a filter for filtration using such a crystalline polymer microporous membrane is considered to have high pleat resistance because of its high membrane flexibility and less stress concentration. The current situation is what is required.

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 2002-370279 A

  An object of the present invention is to solve the above-described problems and achieve the following objects. That is, an object of the present invention is to provide a crystalline polymer microporous membrane having a fine pore diameter and capable of efficiently capturing fine particles having a size of several tens of nm and having a high flow rate. Another object of the present invention is to provide a method for producing a crystalline polymer microporous membrane that can stably withstand stretching at a high magnification. And an object of this invention is to provide the filter for filtration with high pleat tolerance.

  As a result of intensive studies by the present inventors in order to solve the above-mentioned problems, a preformed body manufacturing step for manufacturing a preformed body using a crystalline polymer, a preformed body charging section, and the preformed body charging section Obtained by the extruding step of extruding the preform into a sheet by an extruding device having a constricted portion connected to the constricted portion and a fan portion connected to the constricted portion and having a central angle of 80 ° or more. In a production method including a rolling process for multi-rolling a sheet made of a crystalline polymer and a stretching process for stretching a sheet made of a crystalline polymer obtained by the rolling process, the sheet can be stretched at a high magnification. It has been found that a crystalline polymer microporous membrane that can be stably and endured can be produced. Further, it has been found that by using the above production method, a high flow rate crystalline polymer microporous membrane having a fine pore diameter and capable of efficiently capturing fine particles having a size of several tens of nm can be produced. And it discovered that the pleat tolerance of the filter for filtration which uses the said crystalline polymer microporous membrane became high, and came to completion of this invention.

The present invention is based on the above findings by the present inventors, and means for solving the above problems are as follows. That is,
<1> Preliminary body preparation step of preparing a preform using a crystalline polymer, a preform body input part, a throttle part connected to the preform body input part, and the throttle part, An extrusion process in which the preform is extruded into a sheet shape by an extrusion apparatus having a fan part with a central angle of 80 ° to 160 °, and rolling to perform multi-stage rolling of a sheet made of a crystalline polymer obtained by the extrusion process A method for producing a crystalline polymer microporous membrane, comprising: a step; and a stretching step of stretching a sheet made of the crystalline polymer obtained by the rolling step.
<2> The method for producing a crystalline polymer microporous film according to <1>, wherein the extrusion step is a step of extrusion using an extrusion apparatus having a drawing ratio of 16 or less.
<3> The crystalline polymer microporous film according to any one of <1> to <2>, wherein the rolling step is a step of rolling under a different pressure condition between the final stage rolling and the other rolling. It is a manufacturing method.
<4> The method for producing a crystalline polymer microporous film according to <3>, wherein the pressure in the final stage rolling is higher than the pressure in the other rolling.
<5> The preform is a laminated preform in which a layer containing the first crystalline polymer and a layer containing the second crystalline polymer are laminated, and the melting point of the first crystalline polymer is The method for producing a crystalline polymer microporous film according to any one of <1> to <4>, which is higher than a melting point of the second crystalline polymer.
<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, the above-described problems can be solved, the object can be achieved, fine particles having a minute pore size and several tens of nanometers can be efficiently captured, and a high flow rate crystal. It is an object to provide a porous polymer microporous membrane. Moreover, this invention can provide the manufacturing method of the crystalline polymer microporous film | membrane which can also endure the extending | stretching by high magnification stably. And this invention can provide the filter for filtration with high pleat tolerance.

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 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, a rolling step, and a stretching step, and further includes other steps as necessary.

<Preliminary body manufacturing process>
The preforming step is a step of preparing a preform by spreading and pressing a paste containing a crystalline polymer and other components in a mold.

  Examples of the crystalline polymer include polymers 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. The first crystalline polymer and the second crystalline polymer lower than the melting point of the first crystalline polymer may be used. It is preferable to use it. The first crystalline polymer may be referred to as a “high-melting crystalline polymer”, and the second crystalline polymer may be referred to as a “low-melting crystalline polymer”. 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 crystalline polymer is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include polyalkylene, polyester, polyamide, polyether, liquid crystal polymer, and the like. Polypropylene, polytetrafluoroethylene, polytetrafluoroethylene copolymer, nylon, polyacetal, polybutylene terephthalate, polyethylene terephthalate, syndiotactic polystyrene, polyphenylene sulfide, polyether ether ketone, 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.

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 Examples include 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 include a copolymer containing 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.
The average particle size of the crystalline polymer in the powder form or (or) particulate form is not particularly limited and may be appropriately selected depending on the intended purpose. .4 μm is preferred.

  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.

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 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 heat of crystallization (ΔHc: cal / g) by DSC measurement. 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 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”) That. 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 etc. are 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. Examples of the commercial product of the extrusion aid include hydrocarbon oil (trade name “Isopar” manufactured by Esso Petroleum Corporation), and the addition amount thereof is not particularly limited and is appropriately selected depending on the purpose. However, 15 to 30 parts by mass is preferable with respect to 100 parts by mass of the crystalline polymer.

  There is no restriction | limiting in particular as a method of producing the said preform, According to the objective, it can select suitably, For example, said 1st crystalline polymer (high melting crystalline polymer), and said extrusion aid A method for producing a preform by spreading and pressurizing a paste obtained by kneading with a kneader in a mold, the first crystalline polymer (high melting crystalline polymer), and the second crystal And a method of preparing a laminated preform by placing a pressure-sensitive polymer (low-melting crystalline polymer) and a paste obtained by kneading the extrusion aid in a kneader and pressing the paste.

  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 thickness of the layer containing the first crystalline polymer (high melting crystalline polymer) and the second crystalline polymer (low melting crystalline) when the preform is a two-layer laminated preform. The ratio with the thickness of the layer containing the polymer) 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 crystalline polymer (low melting crystalline polymer) may not be precisely controlled, and less than 1.2: 1 In some cases, the layer containing the second crystalline polymer (crystalline polymer having a low melting point) may be affected by friction and scratching, and may not be able to maintain stable fine particle 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.

  The maximum thickness of the layer containing the first crystalline polymer (high-melting crystalline polymer) and the second crystalline polymer (low-melting crystal) when the preform is a three-layer laminated preform. The ratio with the thickness of the layer containing the conductive polymer) is preferably 5,000: 1 to 1.2: 1, more preferably 2,500: 1 to 1.25: 1, and 1,000: 1 to 1 .5: 1 is particularly preferred. If the ratio is more than 5,000: 1, the thickness of the layer containing the second crystalline polymer (crystalline polymer having a low melting point) may not be precisely controlled. In some cases, the layer containing the second crystalline polymer (crystalline polymer having a low melting point) may be affected by friction and scratching, and may not be able to maintain stable fine particle 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.

  The thickness of the preform is set in accordance with an extrusion method or a rolling method described later. In other words, when it is set in accordance with the extrusion method, it is produced in accordance with the dimensions of the preformed body input part of the extrusion device, and when it is set in accordance with the rolling method, it is generally shaped according to the inlet shape of the rolling device. Is determined. The thickness of the preform is not particularly limited and can be appropriately selected depending on the purpose. If a known example is shown, the thickness of the preform in the case of being set in accordance with the extrusion method For example, the thickness is 5 cm to 20 cm, and the thickness of the preform is set to 0.5 cm to 10 cm, for example.

<Extrusion process>
The extruding step is performed by an extruding apparatus having a preformed body charging unit, a throttle unit connected to the preformed unit charging unit, and a fan unit connected to the throttle unit and having a central angle of 80 ° or more. This is a step of extruding the preform into a sheet.

  The ratio between the cross-sectional area of the preformed body input portion and the minimum cross-sectional area of the drawn portion in the extrusion apparatus used in the extrusion process may be referred to as a drawing ratio (“Reduction Ratio (RR)” or “reduction ratio”). ). The drawing ratio is represented by 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. By reducing the drawing ratio of the extrusion device used in the extrusion step, the preform can be extruded with low shear, and a flexible extrudate (a sheet made of a crystalline polymer) can be obtained.

  There is no restriction | limiting in particular as drawing ratio in the extrusion apparatus used at the said extrusion process, Although it can select suitably according to the objective, 16 or less are preferable, 2-16 are more preferable, and 8-14 are especially preferable. If the drawing ratio exceeds 16, the preform will be extruded at high shear, the flexibility of the extrudate will not be obtained, and it will not be possible to stretch at a high magnification, so a crystalline polymer having a fine pore size May not be available. On the other hand, when the drawing ratio is within the particularly preferable range, the preform can be extruded with low shear, and the flexibility of the extrudate can be obtained. A crystalline polymer having a pore size can be produced.

  The central angle of the fan part in the extrusion apparatus used in the extrusion step refers to the angle formed by the fan part 3 in the extrusion apparatus shown in FIG. By setting the central angle of the fan part to 80 ° or more and 160 ° or less, the preform can be extruded with low shear, and has a flexible extrudate (consisting of a crystalline polymer obtained by an extrusion process). Sheet).

  The central angle of the fan portion in the extrusion apparatus used in the extrusion step is not particularly limited as long as it is 80 ° or more and 160 ° or less, and can be appropriately selected according to the purpose, but is 85 ° or more and 150 ° or less. Preferably, 90 degrees or more and 140 degrees or less are more preferable. If the center angle is less than 80 °, the distance to the extrusion port is increased to ensure the required sample width, and the extrudate is sheared, so the flexibility of the extrudate cannot be obtained. Since it cannot be stretched, it may not be possible to produce a crystalline polymer having a minute pore size. When the angle exceeds 160 °, uniform extrusion in the width direction may be difficult. On the other hand, when the central angle is within the more preferable range, the distance from the uppermost part of the fan part to the outlet width of the fan part is appropriate, so the preform can be extruded with low shear, and the extrudate Therefore, it is possible to stretch at a high magnification, and it is possible to produce a crystalline polymer having a minute pore size.

  The exit width of the fan part in the extrusion apparatus used in the extrusion step refers to the width indicated by reference numeral 7 in the extrusion apparatus shown in FIG. 5 and the width in which the width direction of the lower part of the fan part is a constant value. By setting the outlet width of the fan part to 150 mm to 500 mm, the preform can be extruded with low shear, and a flexible extrudate (sheet made of a crystalline polymer) can be obtained.

  There is no restriction | limiting in particular as an exit width | variety of the fan part in the extrusion apparatus used at the said extrusion process, Although it can select suitably according to the objective, 150 mm-500 mm are preferable, 180 mm-450 mm are more preferable, 200 mm-400 mm are preferable. Particularly preferred. If the outlet width of the fan part is less than 150 mm, the stretching may become unstable. If it exceeds 500 mm, the distance from the uppermost part of the fan part to the outlet width of the fan part becomes long. Since the body is extruded at high shear, the extrudate is not flexible and cannot be stretched at a high magnification, so that a crystalline polymer having a minute pore size may not be produced. On the other hand, if the outlet width of the fan part is within the particularly preferable range, the distance from the uppermost part of the fan part to the outlet width of the fan part becomes appropriate, so that the preform can be extruded with low shear. Since the flexibility of the extrudate is obtained, stretching at a high magnification becomes possible, and a crystalline polymer having a fine pore diameter can be produced.

  There is no restriction | limiting in particular as the method of extrusion in the said extrusion process, Although it can carry out according to the well-known extrusion method and can be suitably selected according to the objective, It is 19 to 200 degreeC with the said extrusion apparatus. A method of extruding the preform at a temperature of is preferable. There is no restriction | limiting in particular as a shape at the time of the said extrusion, Although it can select suitably according to the objective, A rod form is preferable and a sheet form is more preferable. In the extruding step, the items described in “Polyfluorocarbon Handbook” (issued by Daikin Industries, Ltd., revised in 1983) can be appropriately employed.

  There is no restriction | limiting in particular as thickness of the sheet | seat consisting of the crystalline polymer obtained by the said extrusion process, Although it can select suitably according to the objective, 50 micrometers-250 micrometers are preferable, 60 micrometers-220 micrometers are more preferable, 80 micrometers- 200 μm is particularly preferable. When the thickness is less than 50 μm, the film may be broken during film formation, and when it exceeds 250 μm, a load on the rolling mill may be excessively applied. In addition, when the thickness is within the particularly preferable range, it is advantageous in terms of suitability for multi-stage rolling.

<Rolling process>
The rolling step is a step of multi-stage rolling a sheet made of a crystalline polymer obtained by the extrusion step. By rolling the sheet made of the crystalline polymer in a plurality of times, a highly flexible sheet can be produced, and stretching at a high magnification becomes possible.

  The rolling step is not particularly limited and may be appropriately selected depending on the purpose, but it is preferable to perform rolling under different pressure conditions between the final stage rolling and the other rolling, and the pressure in the final stage rolling. However, it is more preferable that it is higher than the pressure in other rolling. In the other rolling, it is possible to suppress shearing in the longitudinal direction during rolling by performing rolling at a constant pressure and a low pressure. In the final stage rolling, a desired pressure can be achieved by performing rolling at a high pressure. The film thickness is adjusted to enable stretching at a high magnification.

  There is no restriction | limiting in particular as rolling frequency | count of the multistage rolling in the said rolling process, Although it can select suitably according to the objective, 2 times-10 times are preferable, 3 times-8 times are more preferable, 3 times-6 times Times are particularly preferred. If the number is less than 2, it may be difficult to adjust to a desired film thickness, and if it exceeds 10, the shear in the longitudinal direction may be excessively applied. In addition, it is advantageous in that the number of times is within the particularly preferable range in that shearing in the longitudinal direction can be suppressed and a desired film thickness can be adjusted.

  The average pressure applied to the sheet made of the crystalline polymer at the time of rolling other than the final stage rolling in the rolling step is not particularly limited and can be appropriately selected according to the purpose, but is preferably 1 MPa to 10 MPa, 2 MPa to 9 MPa is more preferable, and 3 MPa to 8 MPa is particularly preferable. When the average pressure is less than 1 MPa, there is almost no rolling effect, and the load may be excessively applied to the adjustment of the film thickness by rolling in the final stage. When the average pressure exceeds 10 MPa, shearing in the longitudinal direction may be excessively applied. is there. In addition, it is advantageous at the point which can suppress the shear of a longitudinal direction as the said average pressure is in the said especially preferable range.

  There is no restriction | limiting in particular as a pressure concerning the sheet | seat which consists of the said crystalline polymer at the time of the last stage rolling in the said rolling process, Although it can select suitably according to the objective, 10 MPa-30 MPa are preferable, and 12 MPa-28 MPa More preferably, 15 MPa to 25 MPa is particularly preferable. If the pressure is less than 10 MPa, the desired film thickness may not be adjusted, and if it exceeds 30 MPa, shear in the longitudinal direction may be excessively applied. In addition, it is advantageous at the point which can suppress the shear of a longitudinal direction and can adjust to a desired film thickness in the said pressure within the said especially preferable range.

  There is no restriction | limiting in particular as the said rolling method, According to the objective, it can select suitably, For example, the method of rolling by calendaring at a speed | rate of 5 m / min with a calender roll etc. is mentioned. There is no restriction | limiting in particular as temperature at the time of the said rolling, According to the objective, it can select suitably, For example, it can set to 19 degreeC-380 degreeC normally.

<Extension process>
The said extending process is a process of extending | stretching the sheet | seat which consists of a crystalline polymer obtained by the said rolling process. Since the sheet made of the crystalline polymer obtained by the rolling process has flexibility, it can be stretched at a high magnification, and can be stretched at a high magnification. Polymer microporous membranes can be produced.

  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 35 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-400 times are preferable, 1.5 times-350 times are more preferable, It is more preferably 2 to 300 times, and particularly preferably 2.5 to 250 times.
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 1,000 times is particularly preferable. When the stretching is performed, the sheet made of the crystalline polymer may be preheated to a temperature equal to or lower than the stretching temperature in advance. 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.

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

-Extrusion aid removal process-
The extrusion aid removing step is a step of removing the extrusion aid by heating the sheet made of the crystalline polymer obtained by the rolling step, and may be performed during the stretching 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 obtained in the rolling step by passing it through a hot air drying furnace. The thickness of the sheet made of the crystalline polymer thus produced can be appropriately adjusted according to the thickness of the crystalline polymer microporous film to be finally produced, It is necessary to adjust in consideration of the decrease.

-Symmetric heating process-
The symmetrical heating step is a step of symmetrically heating the sheet made of the crystalline polymer obtained by the rolling step or the extrusion auxiliary agent removing step before the stretching step. By performing the symmetrical heating, in the subsequent stretching step, a microporous membrane having a fine structure including short fibrils having an average major axis length of 1 μm or less is obtained, and the pore diameter of the microporous membrane is reduced, resulting in smaller fine particles. Can be obtained efficiently. On the other hand, when the symmetrical heating step is not performed, as described above, nodelessness and fibril miniaturization can be performed by stretching.
The method of symmetrical heating 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 The method of heating by IR etc. is mentioned. Among these, the method of heating with a salt bath is preferable in that variation in heating when heating the entire laminate can be suppressed.
The heating temperature for the symmetrical heating is not particularly limited and may be appropriately selected depending on the purpose. However, the melting point of the first crystalline polymer (high melting crystalline polymer) is high in terms of increasing the flow rate. The following temperatures are preferred. There is no restriction | limiting in particular as the temperature of the endothermic peak position in the DSC chart corresponding to melting | fusing point of the said high melting crystalline polymer, Although it can select suitably according to the objective, 343 to 350 degreeC is preferable.

-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). Thus, 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. The laminated body 15 is subjected to multistage rolling and stretched at a high magnification to produce the crystalline polymer microporous film of the present invention.

  The method for producing a crystalline polymer microporous membrane of the present invention uses an extrusion apparatus having a preformed body charging part, a throttle part, and a fan part having a central angle of 80 ° or more in this order. Can be extruded with low shear, and a sheet having flexibility can be obtained by multi-rolling the obtained extrudate, so that it can stably withstand stretching at a high magnification. Therefore, it can be suitably used as a method for producing a microporous membrane that needs to be stretched at a high magnification.

(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 having a boundary between the layer containing the crystalline polymer and the layer containing the second crystalline polymer. The method for confirming that the crystalline polymer microporous film has a single-layer structure or a laminated structure is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include a method of detecting a cut surface obtained by freezing the porous membrane in the thickness direction and 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 include a shape in which at least one layer in the crystalline polymer microporous membrane has a plurality of pores in which the average pore diameter is constant without change in at least a part of the crystalline polymer microporous membrane in the thickness direction. By adopting the shape of the hole, 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 (t = 0) to the back surface (t = 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. In addition, 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, an optical microscope or a scanning electron microscope (SEM) The method of confirming the shape of a hole part by observing by is mentioned.

The average pore diameter of the pores of the crystalline polymer microporous membrane is not particularly limited and can be appropriately selected depending on the purpose. For example, the average pore size in the layer containing the first crystalline polymer The pore diameter and the average pore diameter of the pores in the layer containing the second crystalline polymer have different average pore diameters.
The average pore diameter of the pores in the layer containing the first 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 μm or less, 0 More preferably, it is 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 size. Can be mentioned.

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 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 μm or less, 0.5 μm or less is more preferable.
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).

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

When the maximum thickness of the layer containing the first crystalline polymer in the crystalline polymer microporous membrane is made larger than the maximum thickness of the layer containing the second crystalline polymer, the flow rate of the crystalline polymer microporous membrane is increased. Can be improved.
When the thickness of the layer containing the second crystalline polymer in the crystalline polymer microporous film is reduced, the flow rate characteristics are improved, while the fine particle capture rate is reduced. On the contrary, when the thickness of the layer containing the second crystalline polymer in the crystalline polymer microporous film is increased, the flow rate characteristic is lowered, but the particulate capturing rate is improved.

  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 present invention has a three-layer structure in which a layer 101 containing a first crystalline polymer, a layer 102 containing a second crystalline polymer, and a layer 103 containing a first crystalline polymer are stacked. The average pore diameters of the pores 101b, 102b, and 103b in the crystalline polymer microporous film are all constant in the thickness direction of the laminate, and the average pore diameter of the crystalline polymer microporous film as a whole is in the thickness direction. There are parts that change in stages. 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.

  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. Since the filtration filter uses a crystalline polymer microporous membrane produced by stretching a sheet made of a crystalline polymer having flexibility at a high magnification, it has high pleat resistance. 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, sandwiched by a primary support 21 and a secondary support 23 which are two supports. There is a filter element cover 26 on the outside to protect 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
<Production of crystalline polymer microporous membrane having a single layer structure>
-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 Manufactured, trade name “Isopar H”) 23 parts by mass was added to make a paste 1. Next, the paste 1 was spread in a mold having the shape shown in FIG. 1 and pressed with a pressure of 6 MPa to produce a sheet-shaped 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 9, the center angle was 120 °, 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 the fan part 3 in the extrusion apparatus shown in FIG. 5, and the outlet width of the fan part refers to the width indicated by reference numeral 7 in the extrusion apparatus shown in FIG.

-Rolling process-
The sheet obtained in the extrusion process was rolled 3 times (first to third rolling) with a calender roll heated to 60 ° C. The first stage rolling to the third stage rolling were performed at an average pressure (average pressure applied to the sheet in each stage) of 20 MPa to produce a sheet having an average thickness of 40 μm and an average width of 180 mm.

-Stretching process-
The sheet obtained in the rolling step was stretched three times in the width direction at room temperature, wound once on a winding roll, and passed through a hot air drying furnace at 250 ° C. to remove the extrusion aid. Next, after extending | stretching between rolls 8 times in the longitudinal direction at 340 degreeC, both ends were pinched with the clip and it extended | stretched 102 times in the width direction at 320 degreeC. Thereafter, heat setting was performed at 320 ° C., and the crystalline polymer microporous membrane of Example 1 was produced.

(Example 2)
<Production of crystalline polymer microporous membrane having a single layer structure>
In the rolling process of Example 1, the first stage rolling to the second stage rolling were performed at an average pressure of 5 MPa, and the final stage rolling was performed at a pressure of 20 MPa to produce a sheet having an average thickness of 45 μm and an average width of 180 mm. In the same manner as in Example 1, the crystalline polymer microporous membrane of Example 2 was produced.

(Example 3)
<Production of crystalline polymer microporous membrane having a single layer structure>
In the extrusion process of Example 1, the same procedure as in Example 1 was conducted, except that a sheet made of a crystalline polymer was produced using an extrusion apparatus having a drawing ratio of 9, a central angle of 80 °, and an outlet width of the fan part of 200 mm. A sheet having an average thickness of 43 μm and an average width of 175 mm was prepared, and the crystalline polymer microporous film of Example 3 was manufactured.

Example 4
<Production of crystalline polymer microporous membrane having a single layer structure>
In the extrusion process of Example 1, the same procedure as in Example 1 was conducted, except that a sheet made of a crystalline polymer was produced using an extrusion apparatus having a drawing ratio of 9, a central angle of 160 °, and an outlet width of the fan part of 200 mm. A sheet having an average thickness of 38 μm and an average width of 165 mm was produced, and the crystalline polymer microporous membrane of Example 4 was produced.

(Example 5)
<Production of crystalline polymer microporous membrane having a single layer structure>
In the extrusion process of Example 1, the same procedure as in Example 1 was conducted, except that a sheet made of a crystalline polymer was produced using an extrusion device having a drawing ratio of 16, a central angle of 120 °, and a fan part outlet width of 200 mm. A sheet having an average thickness of 46 μm and an average width of 195 mm was produced, and the crystalline polymer microporous membrane of Example 5 was produced.

(Example 6)
<Production of crystalline polymer microporous membrane having a single layer structure>
In the extrusion process of Example 1, the same procedure as in Example 1 was conducted, except that a sheet made of a crystalline polymer was produced using an extrusion apparatus having a drawing ratio of 17, a central angle of 120 °, and a fan part outlet width of 200 mm. A sheet having an average thickness of 47 μm and an average width of 194 mm was produced, and the crystalline polymer microporous membrane of Example 6 was produced.

(Comparative Example 1)
<Production of crystalline polymer microporous membrane having a single layer structure>
In the extrusion process of Example 1, the same procedure as in Example 1 was conducted, except that a sheet made of a crystalline polymer was produced using an extrusion device having a drawing ratio of 9, a central angle of 75 °, and an outlet width of the fan part of 200 mm. A sheet having an average thickness of 42 μm and an average width of 185 mm was prepared, and the crystalline polymer microporous film of Comparative Example 1 was manufactured.

(Comparative Example 2)
<Production of crystalline polymer microporous membrane having a single layer structure>
In the rolling process of Example 1, the rolling was performed once, the first stage rolling was performed at a pressure of 60 MPa, and a sheet having an average thickness of 38 μm and an average width of 190 mm was produced. However, it broke during stretching in the longitudinal direction.

(Comparative Example 3)
<Production of crystalline polymer microporous membrane having a single layer structure>
In the extrusion process of Example 1, the same procedure as in Example 1 was conducted, except that a sheet made of a crystalline polymer was produced using an extrusion device having a drawing ratio of 9, a center angle of 50 °, and a fan part outlet width of 200 mm. The film was stretched but broke during stretching.

(Comparative Example 4)
<Production of crystalline polymer microporous membrane having a single layer structure>
In the extrusion process of Example 1, the same procedure as in Example 1 was conducted, except that a sheet made of a crystalline polymer was produced using an extrusion apparatus having a drawing ratio of 9, a central angle of 165 °, and an outlet width of the fan part of 200 mm. Although extrusion was performed, the film formation was stopped because the uniformity in the width direction deteriorated.

(Example 7)
<Manufacture of crystalline polymer microporous membrane having a laminated structure>
-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”) 23 parts by mass was added 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 to obtain a paste 2.
Next, paste 1 and paste 2 are laid and pressed in a mold having the shape shown in FIG. 1 so that the thickness ratio (paste 1 / paste 2 / paste 1) is 3/1/1. (Pressure: 6 MPa) to produce a sheet-like laminated preform.

-Extrusion process-
The laminated preform is inserted into a square cylinder of an extrusion device having a drawing ratio of 9, a central angle of 120 ° and a fan outlet width of 200 mm, and extruded into a sheet to produce a laminated sheet made of a crystalline polymer. did.

-Rolling process-
The laminated sheet obtained in the extrusion process was rolled three times (first stage rolling to three stage rolling) with a calender roll heated to 60 ° C. The first stage rolling to the third stage rolling were performed at an average pressure (average pressure applied to the laminated sheet in each stage) of 15 MPa to produce a laminated sheet made of a crystalline polymer having an average thickness of 50 μm and an average width of 180 mm.

-Stretching process-
The laminated sheet obtained in the rolling step was stretched three times in the width direction at room temperature, once taken up by a take-up roll, and passed through a hot air drying furnace at 250 ° C. to remove and remove the extrusion aid. Next, after extending | stretching between rolls 8 times in the longitudinal direction at 340 degreeC, both ends were pinched with the clip and it extended | stretched 102 times in the width direction at 320 degreeC. Thereafter, heat setting was performed at 320 ° C., and the crystalline polymer microporous film of Example 7 was produced.

(Example 8)
<Manufacture of crystalline polymer microporous membrane having a laminated structure>
In the rolling process of Example 7, the first-stage rolling to the second-stage rolling were performed at an average pressure of 3 MPa, the final-stage rolling was performed at a pressure of 25 MPa, and a laminated sheet having an average thickness of 55 μm and an average width of 185 mm was produced. Produced the crystalline polymer microporous membrane of Example 8 in the same manner as in Example 7.

(Comparative Example 5)
<Manufacture of crystalline polymer microporous membrane having a laminated structure>
In the extrusion process of Example 7, the same procedure as in Example 3 was performed except that a laminated sheet made of a crystalline polymer was produced using an extrusion apparatus having a drawing ratio of 9, a central angle of 60 °, and a fan part outlet width of 200 mm. Then, rolling was performed to prepare a laminated sheet having an average thickness of 53 μm and an average width of 175 mm, and a crystalline polymer microporous film of Comparative Example 5 was manufactured.

(Comparative Example 6)
<Manufacture of crystalline polymer microporous membrane having a laminated structure>
In the rolling process of Example 7, the rolling was performed once, the first stage rolling was performed at a pressure of 50 MPa, and a laminated sheet having an average thickness of 45 μm and an average width of 190 mm was produced. However, it broke during stretching in the longitudinal direction.

(Evaluation)
<Average pore size>
About the crystalline polymer microporous film | membrane of Examples 1-8 and Comparative Examples 1 and 5, the pore meter measurement was performed using the palm porometer (made by PMI). The results are shown in Table 1.

<Capture test>
Using the crystalline polymer microporous membranes of Examples 1 to 8 and Comparative Examples 1 and 5, 0.01% polystyrene latex (average particle size 0.05 μm) at a differential pressure of 0.1 kg / cm ² was obtained. The aqueous solution contained was filtered, the particle concentration in the aqueous solution before and after filtration was measured to calculate the capture rate, and the capture test was performed. The results are shown in Table 1.

<Flow test>
For the crystalline polymer microporous membranes of Examples 1 to 8 and Comparative Examples 1 and 5, the time required for 500 mL of IPA to permeate was measured under a pressure of 0.1 MPa, and a flow rate test was performed. The results are shown in Table 1.

From the results in Table 1, it was found that the crystalline polymer microporous membrane of the present invention can be stretched at a high magnification, and can achieve both a high capture rate and a high flow rate. Then, the crystalline polymer microporous membrane having the laminated structure of Examples 7 and 8 has a smaller pore diameter and a higher capture rate than the crystalline polymer microporous membrane having the single-layer structure of Examples 1 to 6. And a high flow rate.
On the other hand, since Comparative Examples 1 and 5 had a center angle of less than 80 °, the flexibility of the sheet obtained by the extrusion process was not obtained, and it was found that the hole diameter was large and the capture rate was low. Also in Comparative Example 3, the center angle was less than 80 °, and high shearing was applied to the sheet in the extrusion process and the flexibility was lost. Therefore, stretching was performed, but the film broke during stretching. In Comparative Examples 2 and 6, since multi-stage rolling was not performed, when stretched at a high magnification, the sheet was broken in the stretching direction, and a crystalline polymer microporous film could not be produced. In Comparative Example 4, since the center angle exceeded 160 ° and uniform extrusion was not possible in the width direction, extrusion was performed, but the uniformity in the width direction was deteriorated.

<Pleated resistance of filter for filtration>
Between the two polypropylene non-woven fabrics, the crystalline polymer microporous membranes of Examples 1 and 7 and Comparative Examples 1 and 5 were sandwiched and pleated to a pleat width of 10.5 mm, and 138 folds were taken. It was rolled into a cylindrical shape and the seam was welded with an impulse sealer. Both ends of the cylinder were cut off by 2 mm, and the cut surfaces were heat-welded to a polypropylene end plate to finish an element exchange type filter cartridge (filter for filtration).
In the filter cartridge (filter for filtration) using the crystalline polymer microporous membrane of Examples 1 and 7, it was possible to produce the cartridge without any problem in the normal process. On the other hand, the filter cartridges (filters for filtration) using the crystalline polymer microporous membranes of Comparative Examples 1 and 5 were found to have tears during pleating and low processability.

  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 Restriction part 3 Fan part 4 1st layer 5 2nd layer 7 Exit width of fan part 8 Lower mold 10 Laminated preform 15 Laminated 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 Welded portion 101 First crystalline polymer Layer 102 containing the second crystalline polymer 103 layer containing the first crystalline polymer 101b hole 102b hole 103b hole 111 outer peripheral cover 112 membrane support 113 microfiltration membrane 114 membrane support 115 core 116a end plate Minimum cross-sectional area at over preparative 116b end plate 117 Gasket 118 liquid outlet Lm1 holes maximum average pore diameter of the maximum average pore diameter of the maximum average pore diameter of the cross-sectional area A2 constricted portion of the A1 preform insertion portion of Lm3 hole of Lm2 hole of

Claims (7)

A preform forming step of preparing a preform using a crystalline polymer;
The preformed body is formed by an extrusion apparatus having a preformed body charging part, a throttle part connected to the preformed body charging part, and a fan part connected to the throttle part and having a central angle of 80 ° to 160 °. An extrusion process for extruding the sheet into a sheet,
A rolling step of multi-stage rolling a sheet made of a crystalline polymer obtained by the extrusion step;
A stretching step of stretching a sheet made of a crystalline polymer obtained by the rolling step;
A method for producing a crystalline polymer microporous membrane, comprising:   The method for producing a crystalline polymer microporous membrane according to claim 1, wherein the extrusion step is a step of extrusion using an extrusion apparatus having a drawing ratio of 16 or less.   The method for producing a crystalline polymer microporous film according to any one of claims 1 to 2, wherein the rolling step is a step of performing rolling under different pressure conditions between final stage rolling and other rolling.   The method for producing a crystalline polymer microporous membrane according to claim 3, wherein the pressure in the final stage rolling is higher than the pressure in the other rolling.   The preform is a laminated preform in which a layer containing a first crystalline polymer and a layer containing a second crystalline polymer are laminated, and the melting point of the first crystalline polymer is the second melting point. The method for producing a crystalline polymer microporous membrane according to any one of claims 1 to 4, which has a melting point higher than that of the crystalline polymer.   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.