JP4810847B2 - Method for producing polyethylene-based hollow fiber porous membrane - Google Patents

Description

  The present invention relates to a method for producing a polyolefin-based porous membrane suitable for use in separators used in capacitors, lithium ion batteries, etc., or in filter applications such as sterilization and turbidity removal in water treatment.

  Porous membranes are used in separators used in electrolytic capacitors, lithium ion batteries, etc., and electrical and electronics related fields in the production of ultrapure water related to semiconductor manufacturing, pharmaceutical food fields for the purpose of enzyme separation and sterilization, etc. In particular, in recent years, development in the water treatment field in which water and industrial water purification and sewage decontamination are carried out by sterilizing and clarifying rivers and lakes has been actively deployed.

  The main method for producing a porous membrane is a method of forming a micropore by stretching a polymer film or the like, a thermoplastic resin after dissolving a thermoplastic resin and an organic liquid and / or an organic solid capable of dissolving the thermoplastic resin, and then thermoplastic resin A method for obtaining a porous membrane by phase-separation with a non-solvent, and a resin-rich phase and an organic matter-rich phase by cooling an organic liquid and / or an organic solid capable of dissolving a thermoplastic resin and a thermoplastic resin at a high temperature and then cooling. And a method for obtaining a porous membrane by phase separation.

  Among these methods, a method for obtaining a porous membrane by dissolving a thermoplastic resin and an organic liquid and / or an organic solid capable of dissolving the thermoplastic resin at a high temperature and then phase-separating into a resin-rich phase and an organic substance-rich phase by cooling is performed at a high temperature. Since the thermoplastic resin and the organic substance are dissolved, not only can a porous film be produced from a crystalline thermoplastic resin, but there is also an advantage that a non-solvent is not required and process control is facilitated.

Examples of the organic liquid and / or organic solid that can dissolve the thermoplastic resin used in such a method include liquid paraffin and phthalates. (For example, see Patent Documents 1, 2, and 3) However, the latter phthalates are not only suspected of so-called environmental hormones, but also use a halogen-based organic solvent as an extraction solvent. There is a problem that it is not preferable in terms of the working environment.
Japanese Patent No. 2131539 JP 2002-338730 A JP 2002-128943

  On the other hand, the porous membrane produced in this way is used in the above-mentioned fields. For example, in the application of a battery separator, it is necessary to reduce the film thickness in response to the demand for an increase in battery capacity. However, there is a problem that the mechanical properties of the membrane are lowered simply by reducing the membrane pressure. In the field of water treatment, operations such as physically shaking the membrane itself by air bubbling to remove foreign matter attached to the membrane surface are performed, but stable water treatment can be achieved without breaking the membrane for a long time. In order to do so, it is required to further improve the mechanical strength of the membrane itself.

  In order to improve the mechanical strength of such porous membranes, especially in the separator field, the molecular weight of the thermoplastic resin used as the raw material for the porous membrane is increased from the viewpoint of improving the fuse effect characteristics. Has been. (For example, see Patent Documents 2 and 3)

  However, when the raw material resin is simply increased in molecular weight, the melt resin or resin solution viscosity increases significantly when melt extruded or formed into a solution, and an unstable phenomenon for so-called melt fracture occurs during extrusion. There arises a problem that the surface of the film is also extremely rough.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for producing a polyolefin-based porous film that has excellent mechanical properties and is environmentally friendly.

  That is, the present invention extrudes a homogeneous solution obtained by dissolving a polyolefin-based resin in an organic substance capable of forming a uniform solution phase at high temperature and capable of two-phase separation by cooling, and in a cooling bath through an air gap. A method for obtaining a polyolefin-based porous film by cooling and solidifying a polyolefin-based resin solution to obtain a polyolefin-based porous precursor and then removing the organic material using an extraction solvent, wherein the organic material is a higher alcohol, A method for producing a polyolefin-based porous membrane, wherein the polyolefin-based resin has an intrinsic viscosity of 5 to 20 dl / g and a concentration of the polyolefin-based resin in the polyolefin-based resin solution is 5 to 35 wt%. The polyolefin resin of the present invention is preferably an α-olefin polymer.

  Further, the present invention provides a polyolefin based porous membrane characterized in that a lubricant component is added to the polyolefin based resin solution in an amount of 0.10 parts by weight to 6.00 parts by weight with respect to 100 parts by weight of the polyolefin based resin. It is a manufacturing method.

  Furthermore, the present invention is preferably a method for producing a polyolefin-based porous membrane, wherein the higher alcohol is a higher alcohol having 10 to 20 carbon atoms.

  More specifically, the present invention is a method for producing a polyolefin-based porous membrane based on the above-described method, wherein the porous membrane is in the form of a film, sheet or hollow fiber. is there.

  The present invention is useful as a method for producing a polyolefin-based porous membrane having excellent extrusion stability, excellent mechanical properties, and environmental considerations.

  The polyolefin used in the present invention includes α-polyolefins such as low density polyethylene, medium density polyethylene, high density polyethylene, polypropylene, polybutene, polymethylpentene, polymethylbutene, and copolymers and blends thereof. Among them, polyethylene-based resins are inexpensive, do not contain halogen elements that cause problems during disposal, and do not contain tertiary carbon with high chemical reactivity. For example, when used in a membrane for water purification, deterioration due to chemical cleaning It can be expected that it can be used stably for a long period of time. Furthermore, by increasing the molecular weight of the polyethylene-based resin to be used, it is possible to maintain the mechanical strength even if the film thickness is thin, and to meet the demand for an increase in battery capacity, if it is used for battery separators. .

  The organic resin that can form a uniform solution phase at a high temperature and has the ability to separate into two phases by cooling is used in the present invention to have a uniform phase at a temperature higher than the melting point of the polyolefin resin and the polyolefin resin. It is an organic substance that can be formed and has the ability to separate a liquid-liquid phase into a polyolefin-based resin rich phase and the organic substance rich phase by cooling. The lower limit temperature at which a homogeneous solution is formed and the temperature at which liquid-liquid phase separation occurs are determined by the combination of the polyolefin resin and the organic substance. These higher alcohols, liquid paraffin, phthalates and the like can be mentioned. However, the latter phthalates are not only suspected as so-called environmental hormones, but also have a problem that they are not preferable in terms of environmental problems and working environments because halogen-based organic solvents are used as extraction solvents. . From this point of view, higher alcohols are preferable as organic substances that can form a uniform solution phase at high temperatures with the above polyolefin resin and have the ability to separate into two phases by cooling.

  The higher alcohol is preferably a higher alcohol having 10 to 20 carbon atoms. Higher alcohols with less than 10 carbons have a low boiling point, and the higher alcohol component tends to volatilize from the surface of the extrudate before it enters the cooling bath through the air gap after extrusion from the mold. As the concentration of the polyolefin resin increases, the surface of the obtained porous membrane may have a very dense structure. Therefore, the carbon number of the higher alcohol is more preferably 11 or more, and further preferably 12 or more. On the other hand, when the polyolefin resin solution is cooled in a higher alcohol having more than 20 carbon atoms, a temperature range between a temperature at which liquid-liquid phase separation into a polyolefin rich phase and a higher alcohol rich phase and a temperature at which the polyolefin rich phase coagulates. May become extremely small, and it may be difficult to control the porous structure. Therefore, the carbon number of the higher alcohol is more preferably 19 or less, and further preferably 18 or less.

  As examples of these higher alcohols, compounds having an even number of carbon atoms are suitable from the viewpoint of being commercially available at a low cost, and 1-decanol, 1-dodecanol, 1-tetradecanol, 1-hexadecanol are suitable. And linear higher alcohols such as 1-octadecanol and 1-eicosanol. These may be used alone or a mixture thereof. Furthermore, the higher alcohol is not limited to a linear structure, and may be a compound having a double bond or a functional group in a side chain in the molecular structure.

  The molecular weight of the polyolefin resin used in the present invention is preferably 5 to 20 dl / g in terms of intrinsic viscosity. If the intrinsic viscosity is less than 5 dl / g, the expected mechanical properties may not be obtained. Therefore, the intrinsic viscosity of the polyolefin resin is more preferably 6 dl / g or more, and further preferably 7 dl / g or more. On the other hand, when the intrinsic viscosity is higher than 20 dl / g, although depending on the concentration of the solution, the solution viscosity increases, and even with the present invention, it may be difficult to extrude stably. Therefore, the intrinsic viscosity is more preferably 19 dl / g or less, more preferably 18 dl / g or less, still more preferably 17 dl / g or less.

  The concentration of the polyolefin resin in the polyolefin resin solution used in the present invention is preferably 5 to 35 wt%. When the resin concentration is less than 5 wt%, when used as a separation membrane, the pore size of the membrane increases and the permeation amount increases, but sufficient separation ability may not be obtained. Further, the mechanical strength is also lowered, which is not preferable. Therefore, the concentration of the polyolefin resin is more preferably 6% by weight or more, and further preferably 7% by weight or more. On the other hand, when the solution concentration is increased, particularly when a polyolefin resin having a large intrinsic viscosity is used, the mechanical properties can be improved, but the viscosity of the solution is remarkably increased, so that the extrusion can be stably performed. There may not be. Accordingly, the concentration of the polyolefin resin is more preferably 33% by weight or less, and further preferably 30% by weight or less.

  In the present invention, it is important to add 0.10 parts by weight or more and 6.00 parts by weight or less of the lubricant component to 100 parts by weight of the polyolefin resin. If the amount added is less than 0.10 parts by weight, the effect of stable extrusion may not be recognized. Therefore, the addition amount of the lubricant component is more preferably 0.20 parts by weight or more, and further preferably 0.50 parts by weight or more. Moreover, when it exceeds 6.00 weight part, although the effect with respect to stable extrusion is recognized, it may lead to the fall of a mechanical physical property. Therefore, the addition amount of the lubricant component is more preferably 5.80 parts by weight or less, and further preferably 5.50 parts by weight or less.

  The term “lubricant component” as used herein refers to an additive that facilitates processing during extrusion molding, and reduces friction between the polyolefin resin solution and the metal wall surface in the die or extruder and particularly in the spinning nozzle, An additive that has the effect of suppressing the unstable discharge phenomenon. The mechanism of action is not clear, but it is estimated that the friction component between the polyolefin resin solution and the metal wall surface is reduced by forming a layer in which the lubricant component is concentrated on the metal wall surface of the die or nozzle in the flow field due to shear deformation, etc. To do.

  Specific examples of such lubricant components include saturated fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid and esters thereof, unsaturated fatty acids such as oleic acid and erucic acid, and esters thereof, behenine Organic lubricants such as acid amides, stearic acid amides, palmitic acid amides, saturated fatty acid amides such as lauric acid amide, unsaturated fatty acid amides such as erucic acid amide, oleic acid amide, etc., calcium stearate, aluminum stearate, Examples thereof include fatty acid metal salts typified by zinc stearate and the like, and inorganic fine particles such as silica and calcium carbonate.

  Of these lubricant components, an additive having a melting point of polyolefin solution preparation temperature and extrusion molding temperature of about −50 ° C. or more is more preferable in the present invention. When a lubricant component whose melting point is significantly lower than the solution preparation temperature or the extrusion molding temperature is used, a sufficient effect cannot be expected from the viewpoint of heat resistance and thermal stability. Furthermore, in addition to the viewpoints of heat resistance and thermal stability in the above-mentioned polyolefin resin solution, the polyolefin resin solution is extruded to obtain a polyolefin porous membrane precursor, which has a uniform solution phase at high temperatures with the polyolefin resin. An organic substance that can be formed and has the ability to separate into two phases by cooling is extracted to finally obtain a polyolefin-based porous membrane, but the lubricant component that is difficult to remain and bleed out in this polyolefin-based porous membrane Is preferred. From these viewpoints, a fatty acid metal is preferable as the lubricant component used in the present invention.

  Mixing and dissolving the polyolefin resin and the organic substance capable of dissolving the polyolefin resin can be carried out in the following manner. That is, a predetermined amount of each of the polyolefin-based resin, the organic substance, and the lubricant component are weighed and heated and stirred by a heatable mixer. At this time, the heating temperature is preferably +10 to + 100 ° C. of the resin melting point. If the temperature is higher than this, there is a risk of decomposition of the polyolefin or organic matter. Accordingly, the heating temperature is more preferably the resin melting point + 80 ° C. or less, and further preferably the resin melting point + 70 ° C. or less. If the temperature is lower than this, depending on the ability of the organic resin to dissolve, there is a possibility that the dissolution takes a long time, or the viscosity of the resin or mixture becomes high and uniform dissolution cannot be obtained. Therefore, the heating temperature is more preferably a resin melting point + 20 ° C. or more, and further preferably a resin melting point + 30 ° C. or more. For example, when polyethylene is used as the polyolefin-based resin and higher alcohol is used as the organic substance, the dissolution temperature is about 145 ° C to 235 ° C.

  As another method for preparing the polyolefin resin solution, there is a method using an extruder having a single-screw or a twin-screw as described above. When the organic substance that dissolves the polyolefin resin is solid at room temperature, it is preferable that the polyolefin resin and the organic substance are preliminarily chip-blended into a predetermined amount and put into an extruder.

  It should be noted that there is no problem in adding an additive such as an antioxidant to the polyolefin resin solution as required. Examples of the antioxidant include known hindered phenol-based, sulfur-based, and phosphorus-based antioxidants as additives, and among them, hindered phenol-based antioxidants are preferable from the viewpoint of safety. And pentaerythrityl tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate.

  The polyolefin resin solution thus prepared is quantitatively extruded and molded into a desired shape. When forming into a film or sheet, a T die or a circular die is used. In addition, when forming a hollow fiber membrane, a double tube nozzle can be used, but a C-type or three-point bridge type nozzle that does not use an internal solution can also be used. The temperature at the time of molding is the melting point of the polyolefin resin +10 to + 100 ° C. or less, and a range higher than the phase separation temperature of the polyolefin resin solution is desirable. When the molding temperature is higher than the above temperature range, problems such as degradation of the polyolefin-based resin and volatilization of organic substances in the air gap may increase the resin concentration in the molded body and make the film structure dense. Therefore, the molding temperature is more preferably the melting point of the polyolefin-based resin + 20 ° C. or higher, and more preferably + 30 ° C. or higher. On the other hand, when the molding temperature is lower than the above temperature range, there arises a problem that not only the molding becomes difficult as the solution viscosity increases, but also the control of the porous structure becomes difficult. Therefore, the molding temperature is more preferably the melting point of the polyolefin resin + 80 ° C. or less, and more preferably + 70 ° C. or less.

  The molded body thus extruded passes through the air gap and is led to the cooling bath with a draft ratio in the range of 1.0 to 10.0. If the draft ratio is less than 1, the winding tension tends to fluctuate due to buoyancy in the cooling bath, and a hollow fiber membrane may cause thick and thin threads. Therefore, the draft ratio is more preferably 1.2 or more, and further preferably 1.5 or more. On the other hand, if the draft ratio is greater than 10, the compacted article becomes thinner under the constant discharge rate condition, so that it is necessary to use a large diameter nozzle or a die having a wide lip. Therefore, the draft ratio is more preferably 9.0 or less, and even more preferably 8.0 or less. Further, if the discharge amount is increased in order to keep the size of the molded body constant, a melt fracture-like extrusion unstable phenomenon may occur.

  The length of the air gap is preferably 5 to 100 mm. If the air gap becomes extremely short, it is difficult to control the temperature of the surface of the die such as the die surface or the nozzle surface, which may lead to uneven physical properties of the molded body. Therefore, the length of the air gap is more preferably 7 mm or more, and further preferably 10 mm or more. On the other hand, when the air gap length exceeds 100 mm, the volatilization of organic substances proceeds in the air gap, the molded body surface is concentrated with resin, and the structure of the molded body surface may be densified. Therefore, the length of the air gap is more preferably 90 mm or less, and further preferably 80 mm or less.

  A porous precursor can be obtained by the above. A porous film can be obtained by removing the organic component from the porous precursor thus formed. The extraction solvent is not limited, but when using higher alcohols as organic liquids or organic solids that can dissolve polyolefin-based resins, general-purpose organic solvents represented by methanol, ethanol, hexane can be used, There is a secondary effect that it is not necessary to use a solvent related to environmental problems such as a halogen-based organic solvent.

  The porous film thus obtained may be subjected to stretching or heat treatment from the viewpoint of mechanical properties and film characteristics. You may implement these extending | stretching and heat processing in the state of the porous precursor before organic substance extraction.

  Hereinafter, the contents and effects of the present invention will be described with reference to examples, but the present invention is not limited to the following examples.

(Measurement of intrinsic viscosity)
The specific viscosity of various dilute solutions was measured with an Ubbelohde capillary viscosity tube at 135 ° C decalin, and the value obtained by dividing the specific viscosity by the concentration to the origin of the straight line obtained by the least square approximation of the plot. The intrinsic viscosity was determined from the extrapolation point. A 1 wt% antioxidant (trade name “Yoshinox BHT” manufactured by Yoshitomi Pharmaceutical Co., Ltd.) was added to the polyolefin resin, and the mixture was stirred and dissolved at 135 ° C. for 4 hours to prepare a measurement solution.

(Surface observation of porous hollow fiber membrane)
The outer film surface of the platinum-deposited sample was observed with a scanning electron microscope (Hitachi S-2500 type). The observed field of view was photographed with a polaroid camera. Ten hole diameters were arbitrarily measured from the obtained photograph with a ruler to obtain an approximate hole diameter.

(Example 1)
It corresponds to 1.20 kg of polyethylene resin (Hi-Zex Million 145M (extreme viscosity 9.3 dl / g) manufactured by Mitsui Chemicals), 6.80 kg of 1-dodecanol (manufactured by Nacalai Tesque), and 0.2 wt% of the resin as an antioxidant. Irganox 1010 (Nagase Sangyo) was heated and mixed at 170 ° C. to prepare a polyethylene resin solution. The concentration of the polyolefin resin in the polyolefin resin solution was 15 wt%. The obtained solution was extruded at a discharge rate of 3.0 g / min per hole from a C-type nozzle having an outer diameter of 3.0 mm, an inner diameter of 2.0 mm, and a slit width of 0.5 mm under an extrusion temperature of 170 ° C. The hollow molded body extruded from the nozzle was wound up at a draft ratio of 2.5 through a 30 ° C. water tank through a 30 mm air gap. The discharge state from the nozzle was somewhat rough, but the melt fracture-like discharge instability phenomenon was not observed in a good discharge state.

  1-dodecanol was extracted by immersing the porous hollow fiber membrane precursor soaked in an ethanol bath heated to 30 ° C. for 1 hour. When the surface structure of the hollow fiber membrane thus obtained was observed by SEM, it was a porous hollow fiber membrane having pores of about 0.5 μm.

(Example 2)
A porous hollow fiber membrane was obtained in the same manner as in Example 1 except that calcium stearate (manufactured by Nacalai Tesque) corresponding to 1 wt% of the resin was added. The discharge state from the nozzle was a good discharge state with no surface roughness observed.

(Example 3)
A porous hollow fiber membrane was produced in the same manner as in Example 2 except that polyethylene resin (Hi-Z Million 145M manufactured by Mitsui Chemicals) was used in an amount corresponding to 1.60 kg, 1-dodecanol 6.40 kg, and calcium stearate corresponding to 2 wt% of the resin. Got. The concentration of the polyolefin resin in the polyolefin resin solution was 20 wt%. The discharge state from the nozzle was a good discharge state with no surface roughness observed. Moreover, as a result of surface observation by SEM of the porous hollow fiber membrane, a porous structure having pores of about 0.1 to 0.5 μm was observed on the outer surface of the membrane.

Example 4
Porous hollow fiber in the same manner as in Example 2 except that polyethylene resin (Hiex Million 145M manufactured by Mitsui Chemicals) was changed to 1.92 kg, 1-dodecanol was changed to 6.08 kg, and calcium stearate was equivalent to 3 wt% of the resin. A membrane was obtained. The concentration of the polyolefin resin in the polyolefin resin solution was 24 wt%. The discharge state from the nozzle was a good discharge state with no surface roughness observed. As a result of observation of the outer surface of the porous hollow fiber membrane by SEM, a porous structure of about 0.1 μm was observed on the outer surface of the membrane.

(Example 5)
A porous hollow fiber membrane was obtained in the same manner as in Example 1 except that 2.24 kg of polyethylene resin (Hi-Zex Million 030S (extreme viscosity 5.1 dl / g) manufactured by Mitsui Chemicals) and 5.76 kg of 1-dodecanol were used. It was. The concentration of the polyolefin resin in the polyolefin resin solution was 28 wt%. The discharge state from the nozzle was good. Moreover, as a result of surface observation by SEM of the porous hollow fiber membrane, pores of 0.05 to 0.1 μm were observed on the outer surface of the hollow fiber membrane.

(Example 6)
Example 2 except that 0.96 kg of polyethylene resin (Hi-Zex Million 240M (extreme viscosity 16.0 dl / g) manufactured by Mitsui Chemicals), 7.04 kg of 1-dodecanol, and calcium stearate corresponding to 4 wt% of the resin were added. A porous hollow fiber membrane was obtained in the same manner. The concentration of the polyolefin resin in the polyolefin resin solution was 12 wt%. The discharge state from the nozzle was good, with some roughness observed on the surface. Further, in SEM observation of the porous hollow fiber membrane, a porous structure having pores of about 0.5 μm on the outer surface of the hollow fiber membrane was observed.

(Example 7)
Example 2 except that 0.56 kg of polyethylene resin (Hi-Zex Million 320M (extreme viscosity 18.4 dl / g) manufactured by Mitsui Chemicals), 7.44 kg of 1-dodecanol, and calcium stearate corresponding to 5 wt% of the resin were added. A porous hollow fiber membrane was obtained in the same manner. The concentration of the polyolefin resin in the polyolefin resin solution was 7 wt%. The discharge state from the nozzle was good, with some roughness observed on the surface. Further, in the SEM observation of the porous hollow fiber membrane, a porous structure having pores of about 0.8 μm on the outer surface of the hollow fiber membrane was observed.

(Comparative Example 1)
Porous hollow in the same manner as in Example 1 except that 3.20 kg of polyethylene resin (Tosoh Nipolon Hard 5700 (Intrinsic Viscosity 1.5 dl / g)), 4.80 kg of 1-dodecanol, and 160 ° C. extrusion temperature were used. A yarn membrane was obtained. The concentration of the polyolefin resin in the polyolefin resin solution was 40 wt%. The discharge state from the nozzle was good. However, as a result of observing the obtained hollow fiber membrane surface with SEM, the outer surface of the membrane was a dense structure and a porous structure was not observed.

(Comparative Example 2)
Hollow fiber membrane spinning was carried out in the same manner as in Example 1, except that 0.32 kg of polyethylene resin (Nipolon Hard 5700 manufactured by Tosoh Corporation), 7.68 kg of 1-dodecanol, and an extrusion temperature of 150 ° C. were used. The concentration of the polyolefin resin in the polyolefin resin solution was 4 wt%. However, the resin solution has a low viscosity and could not be wound stably.

(Comparative Example 3)
According to the method of Example 2 except that 0.4 kg of polyethylene resin (Hi-Zex Million 340M (Mitsubishi Chemical Co., Ltd., intrinsic viscosity 21.0 dl / g)) 1-dodecanol 7.6 kg and calcium stearate corresponding to 5 wt% of the resin were added. Hollow fiber membrane spinning was performed. The concentration of the polyolefin resin in the polyolefin resin solution was 5 wt%. However, a melt fracture-like instability phenomenon was observed during ejection from the nozzle, and the ejected material could not be wound up.

(Comparative Example 4)
Hollow fiber membrane spinning was carried out in the same manner as in Example 1, except that 0.32 kg of polyethylene resin (Hi-Zex Million 320M (extreme viscosity 18.4 dl / g) manufactured by Mitsui Chemicals) and 7.68 kg of 1-dodecanol were used. . The concentration of the polyolefin resin in the polyolefin resin solution was 4 wt%. However, an unstable phenomenon like melt fracture at the time of discharge from the nozzle was observed, and the discharged material could not be wound up.

(Comparative Example 5)
A porous hollow fiber membrane was obtained in the same manner as in Example 7 except that 3.04 kg of polyethylene resin (Hi-Zex Million 030S (extreme viscosity 5.1 dl / g) manufactured by Mitsui Chemicals) and 4.96 kg of 1-dodecanol were used. It was. The concentration of the polyolefin resin in the polyolefin resin solution was 38 wt%. The discharge state from the nozzle was a good discharge state although roughness on the surface was slightly observed. However, as a result of observing the obtained hollow fiber membrane surface with SEM, the outer surface of the membrane was a dense structure and a porous structure was not observed.

  In the present invention, a polyolefin resin having an intrinsic viscosity of 5 to 20 dl / g is dissolved in a higher alcohol so that the concentration of the polyolefin resin is 5 to 30 wt%, and the polyolefin resin solution is extruded to form an air gap. The polyolefin resin solution is cooled and solidified in a cooling bath to obtain a polyolefin porous precursor, and then the manufacturing method of extracting the organic substance using an extraction solvent is adopted, so that the mechanical properties are excellent and the environment is improved. It is possible to obtain a polyolefin-based porous membrane in consideration of the influence of the above. In addition, the polyolefin-based porous membrane thus obtained should be suitably used for separators used for capacitors, lithium ion batteries, etc., or for filtering filters such as sterilization and turbidity in water treatment. Can contribute to the development of industry.

Claims (4)

A polyethylene resin is dissolved in an organic substance capable of forming a uniform solution phase at a high temperature and capable of two-phase separation by cooling. the homogeneous solution containing 10 parts by weight or more 6.00 parts by weight, and extruded using a double-tube nozzle or C nozzle, polyethylene hollow polyethylene resin solution was cooled and solidified by the cooling bath through an air gap A method of obtaining a polyethylene hollow fiber porous membrane by obtaining a yarn porous membrane precursor and then removing the organic material using an extraction solvent, wherein the organic material is a higher alcohol, and the intrinsic viscosity of the polyethylene resin polyethylene hollow but, wherein 5~20dl / g, and the concentration of the polyethylene resin of the polyethylene resin solution is 5～35Wt% Method for producing a porous membrane. The method for producing a polyethylene-based hollow fiber porous membrane according to claim 1, wherein the length of the air gap is 5 to 100 mm. The manufacturing method of the polyethylene-type hollow fiber porous membrane of Claim 1 or 2 which adds antioxidant further to a polyethylene-type resin solution. The method for producing a polyethylene-based hollow fiber porous membrane according to any one of claims 1 to 3, wherein the higher alcohol is a higher alcohol having 10 to 20 carbon atoms.