WO2011027878A1 - Membrane poreuse en résine de fluorure de vinylidène et son procédé de production - Google Patents

Membrane poreuse en résine de fluorure de vinylidène et son procédé de production Download PDF

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Publication number
WO2011027878A1
WO2011027878A1 PCT/JP2010/065205 JP2010065205W WO2011027878A1 WO 2011027878 A1 WO2011027878 A1 WO 2011027878A1 JP 2010065205 W JP2010065205 W JP 2010065205W WO 2011027878 A1 WO2011027878 A1 WO 2011027878A1
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Prior art keywords
vinylidene fluoride
fluoride resin
porous membrane
plasticizer
hollow fiber
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PCT/JP2010/065205
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English (en)
Japanese (ja)
Inventor
靖浩 多田
健夫 高橋
Original Assignee
株式会社クレハ
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Priority claimed from JP2009237025A external-priority patent/JP5620665B2/ja
Priority claimed from JP2009237026A external-priority patent/JP5552289B2/ja
Application filed by 株式会社クレハ filed Critical 株式会社クレハ
Priority to KR1020127005700A priority Critical patent/KR101372056B1/ko
Priority to CN201080039112.8A priority patent/CN102548647B/zh
Priority to US13/393,628 priority patent/US20120160764A1/en
Publication of WO2011027878A1 publication Critical patent/WO2011027878A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/30—Polyalkenyl halides
    • B01D71/32—Polyalkenyl halides containing fluorine atoms
    • B01D71/34—Polyvinylidene fluoride
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/07—Flat, e.g. panels
    • B29C48/08—Flat, e.g. panels flexible, e.g. films
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/88—Thermal treatment of the stream of extruded material, e.g. cooling
    • B29C48/885—External treatment, e.g. by using air rings for cooling tubular films
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/02—Details relating to pores or porosity of the membranes
    • B01D2325/022—Asymmetric membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2027/00—Use of polyvinylhalogenides or derivatives thereof as moulding material
    • B29K2027/12—Use of polyvinylhalogenides or derivatives thereof as moulding material containing fluorine
    • B29K2027/16—PVDF, i.e. polyvinylidene fluoride
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/755—Membranes, diaphragms

Definitions

  • the present invention relates to a porous membrane made of vinylidene fluoride resin having performance suitable as a separation porous membrane, particularly a (filter) water treatment membrane, and a method for producing the same.
  • the present inventors also melt-extruded a vinylidene fluoride resin having a specific molecular weight characteristic into a hollow fiber shape together with a plasticizer and a good solvent of the vinylidene fluoride resin, and then perform extraction removal and stretching of the plasticizer.
  • a plasticizer and a good solvent of the vinylidene fluoride resin
  • Patent Documents 7 to 11 and others there is a strong demand for further improvement with respect to the overall performance including the filtration performance and mechanical performance required when the porous membrane is used as a filtration permeation membrane.
  • MF microfiltration
  • the average pore size is 0.25 ⁇ m or less, and there is little contamination (clogging) with organic substances during continuous filtration operation of turbid water, and a high water permeability is maintained. It is desirable.
  • the porous membrane disclosed in the following Patent Document 6 has an excessive average pore diameter
  • the hollow fiber porous membrane disclosed in the following Patent Document 8 has a problem in maintaining the amount of water permeation in the continuous filtration operation of muddy water. Remain.
  • JP-A 63-296939 JP-A 63-296940 Japanese Patent Laid-Open No. 3-215535 JP 7-173323 A WO01 / 28667 Publication WO02 / 070115A WO2005 / 099879A WO2007 / 010932A WO2008 / 117740A WO2010 / 082437A Specification of PCT / JP2010 / 051425
  • the present invention provides a porous vinylidene fluoride resin that has a surface pore size, water permeability and mechanical strength suitable for separation applications, particularly (filtered) water treatment, and exhibits good water permeability maintenance performance even during continuous filtration of muddy water.
  • An object of the present invention is to provide a film and a method for producing the same.
  • the ratio between the converted value Q to% (m / day) and the fourth power value P1 4 ( ⁇ m 4 ) of the surface pore diameter P1 of the one surface, Q / P1 4 is 5 ⁇ 10 4 (m / day ⁇ ⁇ m 4 )more than.
  • the present inventors have made continuous filtration performance of muddy water on various vinylidene fluoride resin hollow fiber porous membranes including those disclosed in Patent Documents 7 to 11 above.
  • continuous filtration test (details will be described later) by the MBR method (membrane separation activated sludge method) is performed, and the differential pressure increase in the 2-hour membrane filtration treatment is 0.133 kPa or less
  • the critical filtration flux determined as the filtration flux (flux) is evaluated as a practical evaluation standard for the ability to maintain water permeability, and the evaluation is correlated with the outer surface and internal pore size distribution, porosity, etc. of the porous membrane. I investigated.
  • porous membrane of vinylidene fluoride resin according to the Patent Document 11 the dense layer is relatively thick, therefore, heading is difficulty Q / P1 4 showing the permeability ability in terms of maintaining the fine particle removal performance is degraded (Comparative Examples 1 to 3 described later).
  • the present invention is, while maintaining the characteristics of the film in Patent Document 11 described above, to prevent the thickening of the dense layer, in which succeeded in achieving an improvement in Q / P1 4.
  • a film-like product formed by melting and kneading with a high molecular weight vinylidene fluoride resin using a relatively large amount of a polyester plasticizer that gives a crystallization temperature Tc ′ (° C.) is cooled and solidified from one side, and then the plasticizer is added. It was considered that it is preferable to form an asymmetric reticulated resin porous membrane by extraction. Moreover, in order to promote uniform mixing of the film raw material resin and the plasticizer, a large amount of a good solvent of vinylidene fluoride resin used in Patent Documents 7 to 10 and the like and compatible with the cooling liquid is melted.
  • Tc ′ of the melt-kneaded material almost equivalent to Tc maintains a high difference Tc′ ⁇ Tq from the coolant temperature Tq, and a relatively large amount of plasticizer is densely placed near the membrane surface by phase separation during cooling.
  • Tc′ the melt-kneaded material
  • Tq the coolant temperature
  • plasticizer is densely placed near the membrane surface by phase separation during cooling.
  • This is based on the idea of forming a dense solidified layer of vinylidene fluoride resin dispersed in the resin.
  • the cooling effect from the outer surface reaches the inside of the film at the same time, leading to thickening of the dense solidified layer.
  • the plasticizer is preferably one that gives a lower Tc 'than Tc. According to further studies by the present inventors, even a melt-kneaded product having a Tc ′ lower than Tc gives the solidified product a large crystal melting enthalpy on the basis of the mass of the vinylidene fluoride resin. Then, it has been found that it is possible to form a dense solidified layer (dense layer) of vinylidene fluoride resin in which a relatively large amount of plasticizer is densely dispersed in the vicinity of the above-described film surface.
  • the plasticizer further has a porosity of the dense layer finally formed by extruding the plasticizer once dispersed in the dense solidified layer by phase separation to the adjacent inner layer that has not been sufficiently solidified. It has also been found that it is preferable to have a certain degree of viscosity so as not to cause a decrease in the viscosity.
  • the method for producing a vinylidene fluoride resin porous membrane of the present invention is based on such knowledge, and more specifically, a melt-kneaded product of a vinylidene fluoride resin and a plasticizer is extruded from a die into a film shape,
  • a method of producing a porous film comprising a step of forming a film to be cooled and solidified, and a step of extracting a plasticizer, wherein the plasticizer is compatible with the vinylidene fluoride resin at the formation temperature of the melt-kneaded product, and further It is characterized by satisfying the following conditions (i) to (iii): (I) A crystallization temperature Tc ′ (° C.) lower by 6 ° C.
  • a polyester plasticizer in which the end of a (poly) ester composed of an aliphatic dibasic acid and glycol is sealed with a monovalent aromatic carboxylic acid is used.
  • the schematic explanatory drawing of the apparatus used in order to evaluate the water permeability of the hollow fiber porous membrane obtained by the Example and the comparative example The schematic explanatory drawing of the apparatus used in order to evaluate the critical filtration flux by the MBR method of the hollow fiber porous membrane obtained by the Example and the comparative example.
  • the porous membrane of the present invention can be formed on either a flat membrane or a hollow fiber membrane, but it can be formed as a hollow fiber membrane that can easily increase the membrane area per filtration device, particularly in the case of filtered water treatment. preferable.
  • the vinylidene fluoride resin as the main film raw material is a homopolymer of vinylidene fluoride, that is, polyvinylidene fluoride, a copolymer with other monomers copolymerizable with vinylidene fluoride, or a mixture thereof. And those having a weight average molecular weight of 600,000 to 1,200,000, more preferably 650,000 to 1,000,000, particularly preferably 700,000 to 900,000 are preferably used.
  • the monomer copolymerizable with vinylidene fluoride one or more of ethylene tetrafluoride, hexafluoropropylene, ethylene trifluoride, ethylene trifluoride chloride, vinyl fluoride and the like can be used.
  • the vinylidene fluoride resin preferably contains 70 mol% or more of vinylidene fluoride as a structural unit. Among these, it is preferable to use a homopolymer composed of 100 mol% of vinylidene fluoride because of its high chemical resistance and mechanical strength.
  • the relatively high molecular weight vinylidene fluoride resin as described above can be obtained by emulsion polymerization or suspension polymerization, particularly preferably suspension polymerization.
  • the vinylidene fluoride resin has a relatively large molecular weight of 600,000 or more as well as the resin's original melting point Tm2 (° C) and crystallization temperature Tc (° C) by DSC measurement.
  • the difference Tm2 ⁇ Tc is preferably 32 ° C. or less, more preferably 30 ° C. or less, still more preferably 28 ° C. or less, and most preferably less than 25 ° C.
  • the original melting point Tm2 (° C.) of the resin is distinguished from the melting point Tm1 (° C.) measured by subjecting the obtained sample resin or the resin forming the porous film to the temperature rising process by DSC as it is. It is. That is, generally-available vinylidene fluoride resins exhibit a melting point Tm1 (° C.) different from the original melting point Tm2 (° C.) due to the heat and mechanical history received during the manufacturing process or thermoforming process.
  • the original melting point Tm2 (° C.) of the resin is found again in the DSC temperature raising process after the obtained sample resin is once subjected to a predetermined heating and cooling cycle to remove heat and mechanical history. It is defined as the melting point (endothermic peak temperature accompanying crystal melting), and the details of the measurement method will be described prior to the description of Examples described later.
  • the above-mentioned vinylidene fluoride resins satisfying the condition of Tm2-Tc ⁇ 32 ° C. preferably have a weight average molecular weight of 450,000 to 1,000,000, preferably selected from the above-mentioned vinylidene fluoride resin species as a raw material, 490,000 to 900,000, more preferably 600,000 to 800,000 medium high molecular weight vinylidene fluoride resin for matrix (PVDF-I) 25 to 98% by weight, preferably 50 to 95% by weight, more preferably 60 Crystal characteristic modification with ultra high molecular weight of ⁇ 90% by weight and a weight average molecular weight of 1.4 times or more of PVDF-I and less than 1.5 million, preferably less than 1.4 million, more preferably less than 1.3 million Vinylidene fluoride resin (PVDF-II) for use as a mixture with 2 to 75% by weight, preferably 5 to 50% by weight, more preferably 10 to 40% by weight It is.
  • PVDF-II
  • the medium high molecular weight component functions as a matrix resin component, which keeps the molecular weight level of the entire vinylidene fluoride resin high and gives a hollow fiber porous membrane excellent in strength and water permeability.
  • the ultrahigh molecular weight component is combined with the medium high molecular weight component to increase the crystallization temperature Tc of the raw material resin (generally about 140 ° C. for vinylidene fluoride homopolymer) and has a high plasticizer content. Nevertheless, by increasing the viscosity of the melt-kneaded composition and reinforcing it, stable extrusion in the form of a hollow fiber becomes possible.
  • a gradient pore size distribution in the film thickness direction is formed by a cooling rate gradient in which the cooling surface is rapidly cooled and the opposite surface from the inside is gradually cooled. It will be.
  • the use of a plasticizer that lowers the Tc ′ of the melt-kneaded product maintains the cooling temperature necessary for obtaining the desired surface pore diameter on the small pore diameter surface side (without change) while maintaining the film thickness. Thickening of the dense layer is prevented by delaying crystallization in most of the directions.
  • spherulites of vinylidene fluoride resin are formed on the opposite surface from the inside of the film that is gradually cooled, which may cause a decrease in mechanical strength, a decrease in water permeability, and a decrease in stretchability. Even under such slow cooling conditions, the formation of spherulites can be effectively suppressed by the addition of the ultrahigh molecular weight component.
  • the ultrahigh molecular weight component is considered to act as a crystal nucleating agent, and the characteristics as the crystal nucleating agent appear as an increase in the crystallization temperature Tc of the vinylidene fluoride resin alone, but the relative relationship between the cooling surface and the inside of the film This is not inconsistent with the use of a plasticizer that lowers the Tc ′ of the melt-kneaded product for the purpose of extending the crystallization delay range.
  • Tc is preferably 143 ° C. or higher, more preferably 145 ° C. or higher and most preferably higher than 148 ° C.
  • the Tc of the vinylidene fluoride resin used does not substantially change during the production process of the hollow fiber membrane. Therefore, the obtained hollow fiber porous membrane can be measured as a sample by the DSC method described later.
  • the Mw of the ultra high molecular weight vinylidene fluoride resin (PVDF-II) is less than 1.4 times the Mw of the medium high molecular weight resin (PVDF-I), it is difficult to sufficiently suppress the formation of spherulites. If it is 10,000 or more, it is difficult to uniformly disperse it in the matrix resin.
  • any of the above-mentioned medium and ultra high molecular weight vinylidene fluoride resins can be obtained by emulsion polymerization or suspension polymerization, particularly preferably suspension polymerization.
  • the amount of the ultra high molecular weight vinylidene fluoride resin is less than 2% by weight, the effect of suppressing spherulite and the effect of thickening and reinforcing the melt-kneaded composition are not sufficient, while if it exceeds 75% by weight, the vinylidene fluoride is added. There is a tendency that the phase separation structure of the base resin and the plasticizer becomes excessively fine, and the water permeability of the resulting porous membrane decreases, and further, stable film formation becomes difficult due to the occurrence of melt fracture during processing. .
  • a plasticizer is added to the above-mentioned vinylidene fluoride resin to form a raw material composition for film formation.
  • the hollow fiber porous membrane of the present invention is mainly formed from the above-mentioned vinylidene fluoride resin, but in addition to the above-mentioned vinylidene fluoride resin, at least the plasticizer is used as a pore-forming agent for the production. It is preferable.
  • the plasticizer in the present invention those having compatibility with the vinylidene fluoride resin at the melt kneading temperature and the following characteristics (i) to (iii) are preferably used:
  • the melt-kneaded product with the vinylidene fluoride resin is 6 ° C. or more lower than the crystallization temperature Tc (° C.) of the vinylidene fluoride resin alone, preferably 9 ° C. or more, more preferably 12 ° C. or more lower. Giving a crystallization temperature Tc ′ (° C.), (Ii) As the crystal melting enthalpy ⁇ H ′ (J / g) based on the vinylidene fluoride resin mass standard when measured with a differential scanning calorimeter (DSC), the molded product obtained by cooling and solidifying the melt-kneaded product, Plasticity measured at a temperature of 25 ° C.
  • DSC differential scanning calorimeter
  • the viscosity of the agent alone is 200 mPa ⁇ s to 1000 Pa ⁇ s, preferably 400 mPa ⁇ s to 100 Pa ⁇ s, more preferably 500 mPa ⁇ s to 10 Pa ⁇ s or less.
  • plasticizers having the above-described properties include (poly) esters composed of aliphatic dibasic acids and glycols, that is, polyesters or esters (mono- or diglycol esters of aliphatic dibasic acids, preferably A polyester plasticizer having both ends sealed with a monovalent aromatic carboxylic acid is used.
  • the aliphatic dibasic acid component constituting the (poly) ester at the center of the polyester plasticizer is preferably an aliphatic dibasic acid having 4 to 12 carbon atoms.
  • Examples of such an aliphatic dibasic acid component include succinic acid, maleic acid, fumaric acid, glutamic acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid.
  • aliphatic dibasic acids having 6 to 10 carbon atoms are preferable in terms of obtaining a polyester plasticizer having good compatibility with vinylidene fluoride resins, and adipic acid is particularly preferable from the viewpoint of industrial availability. .
  • These aliphatic dibasic acids may be used alone or in combination of two or more.
  • the glycol component constituting the (poly) ester at the center of the polyester plasticizer is preferably a glycol having 2 to 18 carbon atoms, such as ethylene glycol, 1,2-propylene glycol, and 1,2-butanediol. 1,3-butanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 2,2-diethyl-1, 3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 1,9-nonanediol, 1,10-decanediol, 2-butyl-2 -Aliphatic dihydric alcohols such as ethyl-1,5-propanediol, 1,12-octadecane
  • the above-mentioned polyester plasticizer is preferably sealed at its molecular chain end with an aromatic monovalent carboxylic acid.
  • aromatic monovalent carboxylic acids include benzoic acid, toluic acid, dimethyl aromatic monocarboxylic acid, ethyl aromatic monocarboxylic acid, cumic acid, tetramethyl aromatic monocarboxylic acid, naphthoic acid, biphenyl carboxylic acid, and furic acid.
  • monocyclic or bicyclic aromatic monovalent carboxylic acids are used, and these may be used alone or in combination of two or more.
  • benzoic acid is preferable because of industrial availability.
  • a monomeric resin as long as the plasticizer (components other than the vinylidene fluoride resin in the melt-kneaded product) satisfies the above characteristics (i) to (iii).
  • a plasticizer or a water-insoluble solvent can be used in combination.
  • a preferred example of such a monomeric plasticizer is a dibenzoate monomeric plasticizer comprising glycol and an aromatic monovalent carboxylic acid. As the glycol and aromatic monovalent carboxylic acid contained, those similar to those contained in the above-mentioned polyester plasticizer are used.
  • water-insoluble solvent for example, a solvent that is immiscible with water such as propylene carbonate and has a solubility of, for example, 0.1 g / ml or more at 200 ° C. with respect to vinylidene fluoride resin.
  • the degree of polymerization of the polyester plasticizer is preferably 10,000 or less, more preferably 5000 or less, and most preferably 2000 or less as the number average molecular weight. If the number average molecular weight is more than 10,000, when the molten mixture is cooled and solidified, crystallization of the vinylidene fluoride resin is hindered and ⁇ H ′ is lowered, and the phase separation property at low temperature may be lowered.
  • a viscosity measured at a temperature of 25 ° C. in accordance with JIS K7117-2 (cone-flat plate viscometer used) is often used, preferably 1000 Pa. ⁇ S or less, more preferably 100 Pa ⁇ s or less, and most preferably 10 Pa ⁇ s or less.
  • plasticizer By selecting such a preferable plasticizer, it becomes possible to add a large amount of the plasticizer to the vinylidene fluoride resin having the preferable molecular weight characteristics as described above, and the molded product solidified by cooling after melt extrusion is fluorinated. After separating the vinylidene resin phase and the plasticizer phase and removing the plasticizer phase in the subsequent extraction step, a high dense layer porosity is obtained.
  • the polyester plasticizer used in the present invention is such that a melted mixture can be obtained by melting and kneading with a vinylidene fluoride resin in an extruder so as to obtain a clear (that is, without leaving a dispersion that can be visually recognized with the naked eye).
  • a clear that is, without leaving a dispersion that can be visually recognized with the naked eye.
  • it is compatible with the vinylidene fluoride resin.
  • the formation of the melt-kneaded product in the extruder includes factors other than the properties derived from the raw materials, such as mechanical conditions, and in the sense of eliminating these factors, the compatibility determination method described later in the present invention. To determine compatibility.
  • the plasticizer is 50 to 80% by weight, preferably 60 to 75% by weight relative to 20 to 50% by weight, preferably 25 to 40% by weight, of the vinylidene fluoride resin. % Is good to mix.
  • the monomeric ester plasticizer, water-insoluble solvent, and the like added as necessary are used in such a manner that a part of the plasticizer is replaced in consideration of the melt viscosity of the raw material composition under melt kneading.
  • plasticizer or the like the whole of the components other than the vinylidene fluoride resin constituting the melt mixture including these optional components may be referred to as “plasticizer or the like” hereinafter.
  • the amount of the plasticizer is too small, it is difficult to obtain an increase in the porosity of the dense layer that is the object of the present invention. If the amount is too large, the melt viscosity is excessively reduced, and in the case of hollow fibers, the yarn tends to be crushed. Moreover, there exists a possibility that the mechanical strength of the porous film obtained may fall.
  • the addition amount of the plasticizer is adjusted within the above range so that the Tc ′ of the melt-kneaded product with the vinylidene fluoride resin is 120 to 140 ° C., more preferably 125 to 139 ° C., and further preferably 130 to 138 ° C. Is done. If it is less than 120 ° C., the crystal melting enthalpy ⁇ H ′ of the melt-kneaded product is lowered, and the porosity A1 of the dense layer is lowered, or in the case of a hollow fiber, solidification in the cooling bath is insufficient and the yarn is crushed. May occur. If it exceeds 140 ° C., the thickening prevention effect of the dense layer is insufficient.
  • a biaxial kneading extruder is used, and the vinylidene fluoride resin (preferably comprising a mixture of a main resin and a crystal characteristic modifying resin) is The plasticizer and the like are supplied from the upstream side of the extruder, supplied downstream, and made into a homogeneous mixture before being discharged through the extruder.
  • This twin-screw extruder can be controlled independently by dividing it into a plurality of blocks along its longitudinal axis direction, and appropriate temperature adjustment is made according to the contents of the passing material at each site.
  • the melt-extruded hollow fiber membrane is converted into a vinylidene fluoride resin having a temperature Tq of 50 to 140 ° C., more preferably 55 to 130 ° C., and even more preferably 60 to 110 ° C., lower than the crystallization temperature Tc ′.
  • the cooling bath which consists of a liquid (preferably water) which is inactive (namely, non-solvent and non-reactive), preferentially cools from the outer surface, and solidifies into a film.
  • Tc′ ⁇ Tq When Tc′ ⁇ Tq is less than 50 ° C., it is difficult to form a porous film having a small pore size distribution with a small pore size on the surface of the water to be treated, which is the object of the present invention.
  • the cooling bath temperature Tq is preferably 0 to 90 ° C., more preferably 5 to 80 ° C., and further preferably 25 to 70 ° C.
  • a hollow fiber membrane having an enlarged diameter is obtained by cooling while injecting an inert gas such as air or nitrogen into the hollow portion.
  • an inert gas such as air or nitrogen
  • This is advantageous for obtaining a hollow fiber porous membrane having a small decrease in the amount of water per area (WO 2005 / 03700A).
  • cooling from one side by a chill roll is also used in addition to a cooling bath shower.
  • the elapsed time from the melt extrusion until entering the cooling bath Is generally in the range of 0.3 to 10.0 seconds, particularly 0.5 to 5.0 seconds.
  • the cooled and solidified film-like material is then introduced into an extraction liquid bath and subjected to extraction and removal of a plasticizer and the like.
  • the extraction liquid is not particularly limited as long as it does not dissolve the polyvinylidene fluoride resin and can dissolve the plasticizer and the like.
  • a solvent having a boiling point of about 30 to 100 ° C. is suitable for alcohols such as methanol and isopropyl alcohol, and for a halogen-based solvent such as dichloromethane and 1,1,1-trichloroethane.
  • the halogen-based solvent is swellable with respect to the vinylidene fluoride resin and has a large plasticizer extraction effect. However, due to its swelling property, when the extracted film-like material is transferred to the drying process as it is, the pores formed by the extraction of the plasticizer tend to shrink. Therefore, for the solidified film after melt extrusion and cooling, after extracting the plasticizer with a halogen-based solvent, the halogen-based solvent is removed by immersing in a solvent that does not swell with respect to the vinylidene fluoride resin. It is preferable to dry after substitution. Whether the solvent is swellable with respect to the vinylidene fluoride resin can be evaluated as follows. Examples of non-swellable solvents include, for example, isopropyl alcohol, ethanol, hexane and the like, but are not limited thereto as long as the following evaluation criteria are satisfied.
  • Extraction rinse method that is, the vinylidene fluoride resin film-like molded article containing a halogen-based solvent in the pores is once immersed in a solvent that does not swell with respect to the vinylidene fluoride resin.
  • a method of substituting (rinsing) a halogen-based solvent with, for example, and then drying is performed by, for example, a thermally induced phase separation method using a halogenated solvent as an extraction solvent or a non-solvent using a halogenated solvent as a non-solvent
  • a film-like molded body (b) of vinylidene fluoride resin containing a halogenated solvent is formed in its pores by induced phase separation, it can be applied to both the formation of flat membranes and hollow fiber membranes. Is possible.
  • a film-shaped molded article (b) containing a halogenated solvent is formed by a thermally induced phase separation method that requires the use of a halogenated solvent in order to efficiently extract an organic liquid.
  • a thermally induced phase separation method that requires the use of a halogenated solvent in order to efficiently extract an organic liquid.
  • it is preferably used for forming a hollow fiber membrane in which the membrane area per filtration device can be easily increased.
  • the stretching is generally performed after extraction of the organic liquid with a halogenated solvent, but can also be performed before extraction of the organic liquid with a halogenated solvent.
  • the draw ratio is preferably 1.4 to 5.0 times, more preferably 1.6 to 4.0 times, and most preferably about 1.8 to 3.0 times.
  • the stretching temperature is the same as in the case of stretching after extraction.
  • the method for producing a vinylidene fluoride resin porous membrane including the generalized “extraction rinsing method” is characterized by the following (1) to (8).
  • a film-like molded body (a) of a mixture of a vinylidene fluoride resin and an organic liquid is immersed in a halogenated solvent to extract and remove the organic liquid, and the halogenated solvent is left in the voids of the trace.
  • the said film-shaped molded object (a) has 5 J / g or more as a crystal-melting enthalpy on the basis of vinylidene fluoride resin mass measured by differential operation calorimetry (DSC), as described in (2) above Production method.
  • the mixing ratio of the organic liquid in the mixture of the vinylidene fluoride resin and the organic liquid forming the film-shaped molded body (a) is 200 parts by volume or more with respect to 100 parts by volume of the vinylidene fluoride resin.
  • the extracted film-like material is then subjected to stretching to increase the porosity and pore diameter and improve the strength.
  • stretching it is possible to selectively wet from the outer surface of the film-like material after extraction (porous membrane) to a certain depth and stretch in this state (hereinafter referred to as “partial wet stretching”). It is preferable for obtaining a high dense layer porosity A1. More specifically, prior to stretching, 5 ⁇ m or more from the outer surface of the porous membrane, preferably 7 ⁇ m or more, more preferably 10 ⁇ m or more, and 1 ⁇ 2 or less, preferably 1 / or less, more preferably 1 / 1 / of the film thickness.
  • a depth of 4 or less is selectively wetted.
  • the wet depth is less than 5 ⁇ m, the increase in the dense layer porosity A1 is not sufficient, and when it exceeds 1/2, when the dry heat is relaxed after stretching, the drying of the wetting liquid becomes uneven, and the heat treatment or relaxation Processing may be uneven.
  • Partial wet stretching method basically has a main feature of a stretching step applied to a resin porous membrane that has already been formed in a dry state. Is not subject to essential constraints.
  • the porous membrane is applicable regardless of whether it is a flat membrane or a hollow fiber membrane.
  • the resin forming the porous film can be either a hydrophilic resin or a hydrophobic resin, and either a natural resin or a synthetic resin can be used. However, considering durability such as when the liquid to be treated when used as a separation membrane is an aqueous liquid, it is preferable that the resin be insoluble in water.
  • polyolefin resins eg JP46-40119B, JP50-2176B
  • polyvinylidene fluoride resins eg JP63-296940A, JP03-215535A, WO99 / 47593A, WO03 / 031038A, WO2004 / 081109A, WO2005 / 099879A, JP2001-179062A, JP2003-210954A
  • polytetrafluoroethylene resin polysulfone resin, polyethersulfone resin (WO02 / 058828A1)
  • polyvinyl chloride resin polyarylene sulfide system Resin
  • polyacrylonitrile-based resin cellulose acetate resin (JP2003-31133A), etc.
  • a vinylidene fluoride resin porous membrane is obtained by cooling a mixture of (A) a vinylidene fluoride resin and an organic liquid material that is compatible at least at an elevated temperature, and thereby fluorinating the organic liquid material.
  • a method of obtaining a porous film by causing phase separation from vinylidene resin and removing the organic liquid from the film-like molded body of vinylidene fluoride resin containing the organic liquid separated by phase extraction (thermally induced phase separation method) WO99 / 47593A, WO03 / 031038A, WO2004 / 081109A, WO2005 / 099879A, JP2001-179062A), or (B) a film-like molded body of a mixture of the vinylidene fluoride resin and the organic liquid, and the phase of the organic liquid Contact with a non-solvent of the soluble vinylidene fluoride resin, and replace the organic liquid with the non-solvent.
  • a method of forming a film-like molded body of a vinylidene fluoride resin containing a non-solvent by causing phase separation between the organic liquid and the vinylidene fluoride resin (non-solvent induced phase separation method; JP63-296940A and JP2003) 210954A) or (C) a vinylidene fluoride resin, an organic liquid incompatible with the resin, and a mechanical kneaded product of the inorganic fine powder into a film, and then the organic liquid from the film
  • it is manufactured by a method (JP03-215535A) for extracting a body and inorganic fine powder to obtain a porous membrane, but the method of the present invention can be applied to a porous membrane obtained through any of the above methods. is there.
  • the partial wet stretching method can be formed on either a flat membrane or a hollow fiber membrane.
  • the method for producing a stretched resin porous membrane including the generalized “partial wet stretching method” is characterized by the following (1) to (14): (1) A stretched resin porous membrane, wherein the resin porous membrane is stretched in a state of being selectively wetted with a wetting liquid to a depth of 5 ⁇ m or more and 1/2 or less of the film thickness from the outer surface. Manufacturing method.
  • a solvent for wetting vinylidene fluoride resin such as methanol or ethanol or its aqueous solution
  • a wettability improving liquid having a surface tension of 25 to 45 mN / m (including the case of immersion). If the surface tension is less than 25 mN / m, it may be difficult to selectively apply the wettability improving liquid to the outer surface because the penetration rate into the PVDF porous membrane is too fast.
  • a surfactant solution obtained by adding a surfactant to water that is, an aqueous solution or an aqueous homogeneous dispersion of a surfactant
  • the type of the surfactant is not particularly limited.
  • a carboxylate type such as an aliphatic monocarboxylate, a sulfonate type such as an alkylbenzene sulfonate, a sulfate ester type such as an alkyl sulfate, Phosphate ester type such as alkyl phosphate salt; amine salt type such as alkylamine salt for cationic surfactant, quaternary ammonium salt type such as alkyltrimethylammonium salt; glycerin fatty acid for nonionic surfactant Ester type such as ester, ether type such as polyoxyethylene alkylphenyl ether, ester ether type such as polyethylene glycol fatty acid ester; for amphoteric surfactant, carboxybetaine type such as N, N-dimethyl-N-alkylaminoacetic acid betaine 2-alkyl-1-hydroxyl Le - such as glycine type and the like, such as carboxymethyl imidazo
  • the surfactant preferably has an HLB (hydrophilic / lipophilic balance) of 8 or more. When the HLB is less than 8, the surfactant is not finely dispersed in water, and as a result, uniform wettability improvement becomes difficult.
  • Particularly preferably used surfactants include nonionic surfactants having an HLB of 8 to 20, and further 10 to 18, or ionic (anionic, cationic and amphoteric) surfactants. A surfactant is preferred.
  • the wettability improving liquid to the outer surface of the porous membrane by batch or continuous immersion of the porous membrane.
  • This dipping process is a double-sided coating process for flat membranes and a single-sided coating process for hollow fiber membranes.
  • the flat membrane batch dipping treatment is carried out by dipping the hollow fiber membranes bundled by bobbin winding or casserole winding by dipping the layers cut into appropriate sizes.
  • the continuous treatment is performed by continuously immersing a long porous membrane in the treatment liquid.
  • a surfactant having a relatively high HLB within the above range more specifically 8-20, more preferably 10-18, may be used to form relatively small emulsion particles. preferable.
  • the penetration speed can be lowered moderately by increasing the wettability improving liquid to a high viscosity, or penetrating with a low viscosity. It is possible to increase the speed.
  • the permeation rate can be moderately slowed by lowering the wettability improving liquid or the permeation at a high temperature. It is possible to increase the speed.
  • the viscosity and temperature of the wettability improving liquid act in opposite directions, and can be complementarily controlled for adjusting the penetration rate of the wettability improving liquid.
  • the stretching of the hollow fiber membrane is generally preferably performed as uniaxial stretching in the longitudinal direction of the hollow fiber membrane by a pair of rollers having different peripheral speeds. This is because, in order to harmonize the porosity and the strength and elongation of the vinylidene fluoride resin hollow fiber porous membrane of the present invention, the stretched fibril (fiber) portion and the unstretched node (node) portion are arranged along the stretching direction. This is because it has been found that a microstructure that appears alternately is preferable.
  • the draw ratio is about 1.1 to 4.0 times, particularly about 1.2 to 3.0 times, and most preferably about 1.4 to 2.5 times. When the draw ratio is excessive, the tendency of the hollow fiber membrane to break becomes large.
  • the stretching temperature is preferably 25 to 90 ° C, particularly 45 to 80 ° C. If the stretching temperature is too low, the stretching becomes non-uniform and the hollow fiber membrane is easily broken. On the other hand, if the stretching temperature is too high, it is difficult to increase the porosity even if the stretching ratio is increased. In the case of a flat membrane, sequential or simultaneous biaxial stretching is also possible.
  • the crystallinity is increased by heat treatment in advance at a temperature in the range of 80 to 160 ° C., preferably 100 to 140 ° C. for 1 second to 18000 seconds, preferably 3 seconds to 3600 seconds. It is also preferable.
  • the hollow fiber porous membrane of vinylidene fluoride resin obtained as described above is subjected to at least one stage, more preferably at least two stages of relaxation or constant length heat treatment in a non-wetting atmosphere (or medium).
  • the non-wetting atmosphere is a non-wetting liquid having a surface tension (JIS K6768) larger than the wetting tension of vinylidene fluoride resin near room temperature, typically water or air. Gas is used.
  • the relaxation treatment of the uniaxially stretched porous membrane such as the hollow fiber is carried out by first performing the above-described non-wetting, preferably heated atmosphere, disposed between the upstream roller and the downstream roller, where the peripheral speed gradually decreases. It is obtained by passing the obtained stretched porous membrane.
  • the relaxation rate determined by (1 ⁇ (downstream roller peripheral speed / upstream roller peripheral speed)) ⁇ 100 (%) is preferably in the range of 0% (constant length heat treatment) to 50%, particularly 1 to 20 % Relaxation heat treatment is preferable.
  • a relaxation rate exceeding 20% depends on the stretching ratio in the previous step, but is not preferable because it is difficult to achieve or even if realized, the effect of improving the water permeability is saturated or decreases.
  • the first-stage constant length or relaxation heat treatment temperature is preferably 0 to 100 ° C., particularly 50 to 100 ° C.
  • the treatment time may be short or long as long as the desired heat setting effect and relaxation rate are obtained. Generally, it is about 5 seconds to 1 minute, but it is not necessary to be within this range.
  • the post-stage constant length or relaxation heat treatment temperature is preferably 80 to 170 ° C., more preferably 120 to 160 ° C., so that a relaxation rate of 1 to 20% can be obtained.
  • the effect of the relaxation treatment described above is a remarkable effect that the substantial membrane fractionation performance is maintained in a sharp state and the water permeability of the obtained porous membrane is increased. Moreover, performing the above-mentioned one-stage and two-stage treatment under a constant length is a heat setting operation after stretching.
  • the porous membrane of the present invention obtained through the above series of steps is substantially a single layer membrane of vinylidene fluoride resin, but has a dense layer that has a small pore size and governs separation performance on one surface side thereof.
  • the porosity A1 (%) is 60% or more, preferably 65% or more, more preferably 70% or more (the upper limit is not particularly limited, but generally it is difficult to exceed 85%),
  • the surface pore diameter P1 of the one surface is 0.30 ⁇ m or less, preferably 0.25 ⁇ m or less, more preferably 0.20 ⁇ m or less, most preferably 0.15 ⁇ m or less (the lower limit is not particularly limited, but less than 0.01 ⁇ m)
  • the converted value Q (m) of the water permeability at the test length L 200 mm measured under the conditions of the differential pressure of 100 kPa and the water temperature of 25 ° C.
  • Q / P1 4 is 5 ⁇ 10 4 (m / day ⁇ ⁇ m 4 ) or more, preferably 7 ⁇ 10 4 (m / day ⁇ ⁇ m 4 ) or more, more preferably 1 ⁇ 10 5 (m / day ⁇ ⁇ m 4 ) or more (the upper limit is not particularly limited, but it exceeds 5 ⁇ 10 5 (m / day ⁇ ⁇ m 4 )) Difficult) More preferably, (d) the ratio A1 / P1 with the surface pore diameter P1 ( ⁇ m) of the treated water is 400 or more, preferably 550 or more, more preferably 500 or more (the upper limit is not particularly limited).
  • the ratio A1 / A2 between A1 and the total layer porosity A2 is 0.80 or more, preferably 0.85 or more, more preferably 0.90 or more (the upper limit is generally difficult to exceed 1.0) )
  • the dense layer thickness is generally 7 ⁇ m or more, but 40 ⁇ m or less, preferably 30 ⁇ m or less, more preferably 20 ⁇ m or less, most preferably 15 ⁇ m or less
  • the ratio P2 / P1 of the surface pore diameter P1 ( ⁇ m) on the one surface and the surface pore diameter P2 ( ⁇ m) on the opposite surface is preferably 2.0 to 10. It is represented by being 0.
  • the porosity A1 of the dense layer is 60% or more means that the dense layer that governs the separation performance of the porous membrane of the present invention has a high porosity
  • the average pore diameter Pm is generally 0.25 ⁇ m or less, preferably 0.20 to 0.01 ⁇ m, more preferably 0.15 to 0.05 ⁇ m, and the maximum pore diameter Pmax is generally 0.70 to 0.03 ⁇ m, preferably 0 .40 to 0.06 ⁇ m; Properties with a tensile strength of 7 MPa or more, preferably 8 MPa or more, and a breaking elongation of 70% or more, preferably 100% or more can be obtained.
  • the thickness is usually in the range of about 50 to 800 ⁇ m, preferably 50 to 600 ⁇ m, particularly preferably 150 to 500 ⁇ m.
  • the outer diameter of the hollow fiber is about 0.3 to 3 mm, particularly about 1 to 3 mm.
  • the pure water permeation amount at a test length of 200 mm, a water temperature of 25 ° C., and a differential pressure of 100 kPa is 20 m / day or more, preferably 30 m / day or more, more preferably 40 m / day or more, and the total layer porosity is 80%.
  • the converted water permeability Q is 20 m / day or more, preferably 30 m / day or more, and more preferably 40 m / day or more.
  • Crystal melting point Tm1, Tm2 and crystallization temperature Tc, Tc ′ Using a differential scanning calorimeter “DSC7” manufactured by PerkinElmer Co., Ltd., 10 mg of the sample resin was set in the measurement cell, and the temperature was increased from 30 ° C. to 250 ° C. at a rate of 10 ° C./min in a nitrogen gas atmosphere. Then, after holding at 250 ° C. for 1 minute, the temperature was lowered from 250 ° C. to 30 ° C. at a temperature lowering rate of 10 ° C./min to obtain a DSC curve.
  • DSC7 differential scanning calorimeter
  • the endothermic peak speed in the temperature rising process was the melting point Tm1 (° C.), and the exothermic peak temperature in the temperature lowering process was the crystallization temperature Tc (° C.).
  • the temperature was raised again from 30 ° C. to 250 ° C. at a rate of 10 ° C./min, and the DSC curve was measured.
  • the endothermic peak temperature in this reheated DSC curve was the original resin melting point Tm2 (° C.) that defines the crystal characteristics of the vinylidene fluoride resin of the present invention.
  • the crystallization temperature Tc ′ (° C.) of the mixture of vinylidene fluoride resin as a film raw material and a plasticizer is 10% of the cooled and solidified product of the melt-kneaded product and subjected to the same heating and cooling cycle as described above. An exothermic peak temperature detected during the temperature lowering process after obtaining a curve.
  • the crystallization temperature Tc of the vinylidene fluoride-based resin does not substantially change throughout the manufacturing process of the porous film according to the method of the present invention, but in the present specification, typically, the film after film formation, that is, the extraction process, If necessary, the DSC curve is obtained by subjecting 10 mg of the film finally obtained through the stretching process and the relaxation process to the same heating and cooling cycle as described above, and the measured value of the exothermic peak temperature detected in the cooling process is obtained. It is described.
  • Crystal melting enthalpy ⁇ H ′ of the cooled and solidified product of the melt-kneaded product The crystal melting enthalpy ⁇ H ′ of a mixture of vinylidene fluoride resin as a film raw material and a plasticizer was measured as follows: A DSC curve is obtained by subjecting 10 mg of the cooled and solidified product of the melt-kneaded product to the same temperature raising and lowering cycle as the measurement of the crystallization temperature Tc ′, and the total mass of the cooled and solidified product of the melt-kneaded product from the endothermic peak area at the first temperature increase. The reference crystal melting enthalpy ⁇ H0 (J / g) was determined.
  • ⁇ H ′ ⁇ H0 / (W / W0)
  • ⁇ H ′ ⁇ H0 / (W / W0)
  • the compatibility of the plasticizer (etc.) with the vinylidene fluoride resin was determined by the following method: A slurry-like mixture is obtained by mixing 23.73 g of vinylidene fluoride resin and 46.27 g of a plasticizer at room temperature. Next, the barrel of “Lab Plast Mill” (mixer type: “R-60”) manufactured by Toyo Seiki Co., Ltd. is 10 ° C. higher than the melting point of the vinylidene fluoride resin (for example, about 17 to 37 ° C. higher). The temperature is adjusted, and the slurry mixture is charged and preheated for 3 minutes, and then melt-kneaded at a mixer rotation speed of 50 rpm.
  • the plasticizer is based on vinylidene fluoride resin. Determined to be compatible.
  • the viscosity of the melt-kneaded material is high, it may appear cloudy due to entrapment of bubbles, and in that case, it is determined by deaeration appropriately by a method such as hot pressing. Once it has cooled and solidified, it is heated again to be in a molten state, and then it is determined whether or not it is clarified.
  • the porosity A0 (%) of the whole layer of the unstretched film measured by the same method for the film after extraction and before stretching, and the ratio RB (% by weight) of the plasticizer (and solvent) mixture B in the melt extrusion mixture
  • the approximate number of the ratio A0 / RB is considered to indicate the pore formation efficiency of the mixture B.
  • the hole formation efficiency was determined by the ratio A0 / RL between the total layer porosity A0 and RL.
  • the first intermediate formed body before extraction in the examples and comparative examples described later is cut out to a length of about 300 mm, the pre-extraction yarn length L0 (mm), the pre-extraction outer diameter OD0 (mm), the pre-extraction inner diameter ID0 (mm), and the extraction
  • the previous film thickness T0 (mm) was measured.
  • predetermined operations of extraction, replacement, and drying are performed, and the thread length L1 (mm) after drying, the outer diameter OD1 (mm) after drying, the inner diameter ID1 (mm) after drying, and the film thickness T1 (mm) after drying are obtained. It was measured.
  • Average pore size Based on ASTM F316-86 and ASTM E1294-89, average pore size Pm ( ⁇ m) was measured by a half dry method using “Palm Porometer CFP-200AEX” manufactured by Porous Materials, Inc. Perfluoropolyester (trade name “Galwick”) was used as a test solution.
  • the average pore diameter P1 of the treated water side surface (outer surface in hollow fiber) and the average pore diameter P2 of the permeated water side surface (inner surface in hollow fiber) were determined by SEM method. Measured (SEM average pore diameter).
  • SEM average pore diameter the measurement method will be described by taking a hollow fiber porous membrane sample as an example. SEM photography is performed on the outer surface and inner surface of the hollow fiber membrane sample at an observation magnification of 15,000 times, respectively. Next, for each SEM photograph, the hole diameter is measured for everything that can be recognized as a hole.
  • the arithmetic average of the measured pore diameters is obtained and set as the outer surface average pore diameter P1 and the inner surface average pore diameter P2.
  • the photograph image may be divided into four equal parts, and the above-mentioned hole diameter measurement may be performed for one area (1 ⁇ 4 screen). .
  • the number of measurement holes is approximately 200 to 300.
  • the thickness of the dense and continuous layer having a substantially uniform pore diameter from the surface to be treated is measured by cross-sectional observation using an SEM.
  • the measurement method will be described by taking a hollow fiber porous membrane sample as an example.
  • the hollow fiber porous membrane material is immersed in isopropyl alcohol (IPA), the pores are impregnated with IPA, then immediately immersed in liquid nitrogen and frozen, and while being frozen, the hollow fiber membrane is folded and broken, A cross section perpendicular to the longitudinal direction is exposed.
  • IPA isopropyl alcohol
  • the hole diameter is measured for all the 3 ⁇ m ⁇ 3 ⁇ m square regions centered on a point of 1.5 ⁇ m from the outer surface that can be recognized as holes.
  • the arithmetic average of the measured pore diameter is obtained, and this is defined as the sectional pore diameter X 1.5 ( ⁇ m) at a depth of 1.5 ⁇ m.
  • the arithmetic average pore diameter is obtained in the same manner as described above for the 3 ⁇ m ⁇ 3 ⁇ m square region centered on the point shifted to the inner surface side sequentially at an interval of about 3 ⁇ m.
  • the cross-sectional hole diameter X d ( ⁇ m) at an arbitrary depth d ( ⁇ m) is obtained from the outer surface. If the condition of X d / X 1.5 ⁇ 1.2 is satisfied, the hole diameter is assumed to be uniform, and the dense layer thickness having a uniform hole diameter is defined as the maximum depth d ( ⁇ m) that satisfies the condition.
  • a flat membrane or hollow fiber-like porous membrane sample is impregnated with a porosity A1 (%) (hereinafter referred to as “dense layer porosity A1”) of a portion having a thickness of 5 ⁇ m in contact with the surface to be treated of the dense layer. Measure by the method.
  • VL (W ⁇ W0) / ( ⁇ s ⁇ 1000)
  • ⁇ s is the specific gravity of the test solution and is 1.261 (g / ml).
  • the dense layer porosity A1 (%) is calculated by the following formula.
  • A1 VL / V ⁇ 100.
  • the mini module is formed by vertically fixing two hollow fiber porous membrane samples between the upper header and the lower header so that the effective filtration length per one becomes 500 mm.
  • the upper header is an upper insertion port to be fixed with the upper end of the hollow fiber membrane being opened on the lower side, an internal space (flow path) for filtrate water communicating with the upper insertion port, and suction on the upper side. It has a filtrate outlet for discharging filtrate to the pump.
  • the lower header has a lower insertion port for fixing the hollow fiber membrane on its upper side with its lower end closed, and an aeration nozzle that does not communicate with the lower insertion port (diameter 1 mm ⁇ 10) And an internal space (supply path) for supplying air to the aeration nozzle and an air supply port for supplying air from the air pump to the internal space.
  • the upper and lower ends of the two hollow fiber membrane samples are each inserted and fixed to the upper insertion port by epoxy resin so that the upper header is liquid-tightly connected, and the lower header is inserted so that the lower header is closed. It is inserted into the mouth and fixed.
  • This modularized hollow fiber membrane sample was dipped in ethanol for 15 minutes and then wetted by replacement with pure water. Then, the bottom area was approximately 30 cm 2 and the height of the water surface was approximately 600 mm. Soak the hollow fiber vertically.
  • MLSS floating substance concentration
  • DOC total organic concentration after filtration through a 1 ⁇ m glass filter
  • 7 to 9 mg / L of activated sludge water is supplied at a rate of 0.2 L / min by a pump, and the overflow is circulated to the raw water tank. Further, air is supplied from the lower header at a rate of 5 L / min, and is constantly bubbled into the activated sludge water in the test water tank.
  • the suction filtration operation is performed for 13 minutes with a constant amount of filtrate, and the filtration is stopped for 2 minutes. While repeating the cycle, the suction filtration is performed for 2 hours, and the change with time of the differential pressure inside and outside the hollow fiber porous membrane is measured.
  • the constant amount of filtered water is initially 0.3 m / day as the filtration flux (m / day) and increases by 0.1 m / day every 2 hours, and the differential pressure increase rate becomes higher than 0.133 kPa / 2 hours.
  • polyester plasticizer polymer of dibasic acid and glycol whose ends are sealed with benzoic acid; “W-83” manufactured by DIC Corporation, number average molecular weight of about 500, JIS K7117-2 (cone-flat plate) The viscosity measured at 25 ° C. with a mold rotational viscometer (750 mPa ⁇ s) was used.
  • the mixture A is supplied from the powder supply unit, and the barrel temperature is 220 ° C.
  • the mixture was fed and kneaded at a barrel temperature of 220 ° C., and the mixture was extruded into a hollow fiber shape from a nozzle (190 ° C.) having a circular slit having an outer diameter of 6 mm and an inner diameter of 4 mm. At this time, the inner diameter was adjusted by injecting air into the hollow portion of the hollow fiber from the vent provided in the center of the nozzle.
  • the extruded mixture is kept in a molten state, is maintained at a temperature of 50 ° C., and has a water surface at a position 280 mm away from the nozzle (that is, an air gap of 280 mm). (Retention time in cooling bath: about 6 seconds) After taking up at a take-up speed of 3.8 m / min, this was wound around a bobbin to obtain a first intermediate molded body.
  • the plasticizer was extracted by immersing this first intermediate molded body in dichloromethane at room temperature for 30 minutes. At this time, the extraction was performed while rotating the bobbin so that the dichloromethane was evenly distributed over the yarn. Next, the operation of replacing the dichloromethane with a new one and extracting again under the same conditions was repeated, and extraction was performed three times in total.
  • the first intermediate molded body containing dichloromethane is immersed in isopropyl alcohol (IPA) at room temperature for 30 minutes without being substantially dried (that is, in a state where no whitening is visually recognized in the first intermediate molded body). Then, the dichloromethane impregnated in the first intermediate molded body was replaced with IPA. At this time, the replacement was performed while rotating the bobbin so that the IPA was evenly distributed over the yarn. Subsequently, the operation of replacing the IPA with a new one and replacing the same under the same conditions was repeated, and the replacement was performed twice in total.
  • IPA isopropyl alcohol
  • IPA was removed by air drying at room temperature for 24 hours, followed by heating in an oven at a temperature of 120 ° C. for 1 hour to remove IPA and heat treatment to obtain a second intermediate molded body. At this time, the shrinkage stress of the yarn was relaxed so that the diameter of the bobbin was freely contracted.
  • the second intermediate molded body is pulled out while rotating the bobbin, the first roll speed is set to 20.0 m / min, and the second roll is passed through a 60 ° C. water bath.
  • the film was stretched 1.75 times in the longitudinal direction by setting the speed to 35.0 m / min.
  • it is passed through a hot water bath controlled at a temperature of 90 ° C., the first stage relaxation rate is relaxed at 8%, and further passed through a dry heat tank controlled at a spatial temperature of 140 ° C., and the second stage relaxation rate is 1.5%. And relaxed.
  • Example 2 A polyvinylidene fluoride hollow fiber porous membrane of the present invention was obtained in the same manner as in Example 1 except that the cooling water bath temperature Tq after melt extrusion was changed to 70 ° C.
  • Example 2 A polyvinylidene fluoride hollow fiber porous membrane was obtained essentially by the method of Example 7 of Patent Document 11.
  • a polyvinylidene fluoride hollow fiber porous membrane of the present invention was obtained in the same manner as in Comparative Example 1 except that 8% relaxation was performed in a water bath and then 2% relaxation treatment was performed in air at 140 ° C.
  • Example 3 A polyvinylidene fluoride-based hollow fiber porous membrane was obtained essentially by the method of Example 8 of Patent Document 11.
  • a polyvinylidene fluoride hollow fiber porous membrane of the present invention was obtained in the same manner as in Comparative Example 2 except that the cooling water bath temperature Tq after melt extrusion was changed to 85 ° C.
  • PVDF-I PVDF mixture A in which PVDF-I and PVDF-II were mixed at a ratio of 95% by weight and 5% by weight using polyvinylidene fluoride having Mw of 4.1 ⁇ 10 5 was used.
  • Adipic acid polyester plasticizer as a plasticizer polyester of adipic acid and 1,2-propylene glycol whose ends are sealed with octyl alcohol; “PN150” manufactured by ADEKA Corporation, number average molecular weight of about 1000, viscosity of 500 mPa ⁇ s) And N-methylpyrrolidone (NMP) in a proportion of 82.5 wt% / 17.5 wt% with stirring and mixing at room temperature; used plasticizer / solvent mixture B; Supply at a ratio of 4% by weight / 61.6% by weight; water cooling bath temperature at 40 ° C .; no extraction rinse with IPA Except that the draw ratio was 1.85 times; as the heat treatment after stretching, 8% relaxation was performed in a 90 ° C. water bath, and then 3% relaxation treatment was performed in air at 140 ° C .; A polyvinylidene fluoride porous membrane was obtained in the same manner as in Example 1.
  • PVDF-I PVDF mixture A in which PVDF-I and PVDF-II were mixed at a ratio of 75% by weight and 25% by weight using polyvinylidene fluoride having Mw of 4.1 ⁇ 10 5 was used.
  • a plasticizer / solvent mixture B mixed at a ratio of 0.6 wt% and the solvent N-methylpyrrolidone (NMP) 31.4 wt% was used.
  • the mixture was fed at a ratio of 2 (weight) and kneaded at a barrel temperature of 220 ° C., and the kneaded product was extruded into a hollow fiber form from a nozzle (temperature 150 ° C.) having a circular slit having an outer diameter of 6 mm and an inner diameter of 4 mm. At this time, air was injected into the air-conditioning section of the hollow fiber from the vent hole provided in the center of the nozzle to adjust the inner diameter.
  • the extruded molten mixture is cooled at a cooling water bath temperature of 15 ° C., extracted by dichloromethane and then stretched 1.1 times, and further passed through a hot water bath at 90 ° C. and a dry heat bath controlled at a space temperature of 140 ° C.
  • a polyvinylidene fluoride hollow fiber porous membrane was obtained.
  • PVDF-I a mixture containing PVDF-I and PVDF-II of 95% by weight and 5% by weight using polyvinylidene fluoride having an Mw of 4.1 ⁇ 10 5 was used.
  • an adipic acid-based polyester plasticizer as a plasticizer, polyester of adipic acid and 1,2-butanediol whose ends are sealed with isononyl alcohol; “D620N” manufactured by J.
  • Mixture A is supplied from the powder supply section, and mixture B is heated to 160 ° C. from the liquid supply section provided at a position 480 mm from the most upstream part of the cylinder.
  • Mixture A / mixture B 38.4 / 61.
  • the mixture was fed at a ratio of 6 (weight) and kneaded at a barrel temperature of 220 ° C., and the kneaded product was extruded into a hollow fiber shape from a nozzle having a circular slit having an outer diameter of 7 mm and an inner diameter of 5 mm. At this time, air was injected into the air-conditioning section of the hollow fiber from the vent hole provided in the center of the nozzle to adjust the inner diameter.
  • the extruded molten mixture is cooled at a cooling water bath temperature of 70 ° C.
  • the mixture B is extracted with dichloromethane, dried at 50 ° C. for 1 hour, stretched 2.4 times at 85 ° C., and further heated at a 90 ° C. hot water bath.
  • the polyvinylidene fluoride hollow fiber porous membrane was obtained by relaxing 1% in the solution and further relaxing 1% in a dry heat bath controlled at a space temperature of 140 ° C.
  • Example 7 Extrusion was performed in the same manner as in Example 1 except that polyvinylidene fluoride having a Mw of 4.1 ⁇ 10 5 was used as PVDF-I. However, the yarn could not be formed because the yarn was crushed in the cooling water bath after melt extrusion.
  • Example 8 Extrusion was carried out in the same manner as in Example 1 except that the cooling water bath temperature Tq after melt extrusion was changed to 85 ° C. However, the yarn could not be formed because the yarn was crushed in the cooling water bath after melt extrusion.
  • Example 9 A dibenzoate-type monomeric plasticizer (“PB-10” manufactured by DIC Corporation, number average molecular weight of about 300, viscosity of 81 mPa ⁇ s) was used as the plasticizer; 26.9 wt% / 73 of the mixture A and the mixture B A polyvinylidene fluoride hollow fiber porous membrane was obtained in the same manner as in Example 1 except that the cooling water bath temperature Tq after melt extrusion was changed to 60 ° C.
  • PB-10 dibenzoate-type monomeric plasticizer manufactured by DIC Corporation, number average molecular weight of about 300, viscosity of 81 mPa ⁇ s
  • PVDF-I Polyvinylidene fluoride
  • Mw weight average molecular weight
  • PVDF-II polyvinylidene fluoride for modifying crystal properties having a Mw of 9.7 ⁇ 10 5 (PVDF-II) ) (Powder) at a ratio of 75 wt% and 25 wt%, respectively, was mixed using a Henschel mixer to obtain a PVDF mixture having an Mw of 6.1 ⁇ 10 5 .
  • a polyester plasticizer polymer of adipic acid and 1,2-butanediol whose ends are sealed with isononyl alcohol; “D623N” manufactured by J Plus Co., Ltd., number average molecular weight of about 1800, JIS K7117- 2 (cone-flat-plate rotational viscometer) measured viscosity at 25 ° C. 3000 mPa ⁇ s, specific gravity 1.090 g / ml) and monoisonic ester plasticizer diisononyl adipate (“DINA” manufactured by J. Plus) And a plasticizer mixture obtained by stirring and mixing at a normal temperature of 88% / 12% by weight.
  • the mixture was fed and kneaded at a barrel temperature of 220 ° C., and the mixture was extruded into a hollow fiber shape from a nozzle (190 ° C.) having a circular slit having an outer diameter of 6 mm and an inner diameter of 4 mm. At this time, the inner diameter was adjusted by injecting air into the hollow portion of the hollow fiber from the vent provided in the center of the nozzle.
  • the plasticizer was extracted by immersing the first intermediate molded body in dichloromethane at room temperature for 30 minutes. At this time, the extraction was performed while rotating the bobbin so that the dichloromethane was evenly distributed over the yarn. Next, the operation of replacing the dichloromethane with a new one and extracting again under the same conditions was repeated, and extraction was performed three times in total.
  • the first intermediate molded body containing dichloromethane is immersed in isopropyl alcohol (IPA) at room temperature for 30 minutes without substantially drying (that is, no whitening is visually recognized in the first intermediate molded body).
  • IPA isopropyl alcohol
  • the dichloromethane impregnated in the first intermediate molded body was replaced with IPA.
  • the replacement was performed while rotating the bobbin so that the IPA was evenly distributed over the yarn.
  • the operation of replacing the IPA with a new one and replacing the same under the same conditions was repeated, and the replacement was performed twice in total.
  • IPA was removed by air drying at room temperature for 24 hours, followed by heating in an oven at a temperature of 120 ° C. for 1 hour to remove IPA and heat treatment to obtain a second intermediate molded body.
  • the bobbin diameter was freely contracted, and drying and heat treatment were performed without restricting the contraction of the yarn.
  • the second intermediate formed body is pulled out while rotating the bobbin, the first roll speed is set to 20.0 m / min, and the second roll is passed through the 60 ° C. water bath.
  • the film was stretched 1.75 times in the longitudinal direction by setting the speed to 35.0 m / min.
  • it is passed through a hot water bath controlled at a temperature of 90 ° C., the first stage relaxation rate is relaxed at 8%, and further passed through a dry heat tank controlled at a spatial temperature of 140 ° C., and the second stage relaxation rate is 1.5%. And relaxed. This was wound up to obtain a vinylidene fluoride resin hollow fiber porous membrane.
  • Example A2 A vinylidene fluoride resin porous membrane was obtained in the same manner as in Example A1, except that the cooling water bath temperature Tq after melt extrusion was changed to 30 ° C .; the draw ratio was changed to 1.85 times.
  • W-83 manufactured by DIC Corporation, number average molecular weight of about 500, JIS K7117-2 (cone- A viscosity measured at 25 ° C. by a flat plate type viscometer (750 mPa ⁇ s, specific gravity 1.155 g
  • PB-10 monomeric ester plasticizer
  • an unstretched vinylidene fluoride resin porous membrane was obtained according to the method disclosed in Patent Document 4, and then the unstretched yarn was partially wetted and then stretched. That is, hydrophobic silica (“Aerosil R-972” manufactured by Nippon Aerosil Co., Ltd., primary particle average diameter 16 nanometer, specific surface area 110 m 2 / g) 14.8% by volume, dioctyl phthalate (DOP) 48.5% by volume %, Dibutyl phthalate (DBP) 4.4% by volume is mixed with a Henschel mixer, and 32.3% by volume of polyvinylidene fluoride (powder) having a weight average molecular weight (Mw) of 2.4 ⁇ 10 5 is mixed therewith. Added and mixed again with a Henschel mixer.
  • hydrophobic silica (“Aerosil R-972” manufactured by Nippon Aerosil Co., Ltd., primary particle average diameter 16 nanometer, specific surface area 110 m 2
  • a hollow fiber was extruded from a nozzle (temperature 240 ° C.) having a circular slit with a diameter of 6 mm and an inner diameter of 4 mm. At this time, the inner diameter was adjusted by injecting air into the hollow portion of the hollow fiber from the vent provided in the center of the nozzle.
  • the extruded mixture is kept in a molten state, maintained at a temperature of 70 ° C., and has a water surface at a position 140 mm away from the nozzle (ie, the air gap is 140 mm). (Residence time in the cooling bath: about 9 seconds) was taken at a take-up speed of 2.5 m / min to obtain a first intermediate molded body having an outer diameter of 2.87 mm and an inner diameter of 1.90 mm.
  • the plasticizer was extracted by immersing this first intermediate molded body in dichloromethane at room temperature for 30 minutes. Next, the operation of replacing the dichloromethane with a new one and extracting again under the same conditions was repeated, and extraction was performed four times in total. Next, it was dried in a vacuum dryer at a temperature of 30 ° C. for 24 hours to remove dichloromethane.
  • the hollow fiber was wetted by immersing in 50% ethanol aqueous solution for 30 minutes and further immersing in pure water for 30 minutes. Further, after removing the hydrophobic silica by immersing in a 20% aqueous sodium hydroxide solution at 70 ° C. for 1 hour, it is washed with water to remove the sodium hydroxide, and then dried in a vacuum dryer at a temperature of 30 ° C. for 24 hours. A molded body was obtained. In addition, during a series of operations from extraction to drying, both ends of the hollow fiber were not contracted and were freely contracted.
  • Example A1 A vinylidene fluoride resin hollow fiber porous membrane was obtained in the same manner as in Example A1, except that partial wetting was not performed prior to stretching.
  • Example A2 A vinylidene fluoride resin hollow fiber porous membrane was obtained in the same manner as in Example A2 except that partial wetting was not performed prior to stretching.
  • Example A4 A vinylidene fluoride resin hollow fiber porous membrane was obtained in the same manner as in Example A3 except that partial wetting was not performed prior to stretching.
  • Example A5 A vinylidene fluoride resin hollow fiber porous membrane was obtained in the same manner as in Example A4 except that partial wetting was not performed prior to stretching.
  • Example A6 A vinylidene fluoride resin hollow fiber porous membrane was obtained in the same manner as in Example A5 except that partial wetting was not performed prior to stretching.
  • Example B1 Polyvinylidene fluoride (PVDF-I) for matrix having a weight average molecular weight (Mw) of 4.9 ⁇ 10 5 (powder) and polyvinylidene fluoride for modifying crystal properties having a Mw of 9.7 ⁇ 10 5 (PVDF-II) ) (Powder) at a ratio of 75 wt% and 25 wt%, respectively, was mixed using a Henschel mixer to obtain a PVDF mixture having an Mw of 6.1 ⁇ 10 5 .
  • a polyester plasticizer polymer of dibasic acid and glycol whose ends are sealed with a monohydric alcohol; “W-4010” manufactured by DIC Corporation, number average molecular weight of about 4000, JIS K7117-2 (cone -Viscosity measured at 25 ° C by a flat plate type viscometer), specific gravity 1.113 g / ml), and diisononyl adipate, a monomeric ester plasticizer ("DINA” manufactured by Jay Plus Co., Ltd.) K7117-2 (cone-flat plate viscometer) measured at 25 ° C.
  • DINA monomeric ester plasticizer manufactured by Jay Plus Co., Ltd.
  • the mixture A is supplied from the powder supply unit, and the barrel temperature is 220 ° C.
  • the mixture was fed at a ratio and kneaded at a barrel temperature of 220 ° C., and the mixture was extruded into a hollow fiber shape from a nozzle (190 ° C.) having a circular slit having an outer diameter of 6 mm and an inner diameter of 4 mm.
  • the inner diameter was adjusted by injecting air into the hollow portion of the hollow fiber from the vent provided in the center of the nozzle.
  • the extruded mixture is kept in a molten state, maintained at a temperature of 12 ° C., and has a water surface at a position 280 mm away from the nozzle (that is, an air gap of 280 mm). (Retention time in the cooling bath: about 6 seconds) After being taken up at a take-up speed of 3.8 m / min, this was wound up on a bobbin (core diameter: 220 mm) to a length of 500 m to obtain an outer diameter of 1.80 mm, A first intermediate molded body having an inner diameter of 1.20 mm (vinylidene fluoride resin hollow fiber porous membrane containing an organic liquid) was obtained.
  • this first intermediate molded body was cut out to a length of 300 mm, and the organic liquid was extracted by immersing in dichloromethane as an extraction solvent at room temperature for 30 minutes without fixing both ends. At this time, extraction was carried out while stirring the dichloromethane so that the dichloromethane was evenly distributed over the yarn. Next, the operation of replacing the dichloromethane with a new one and extracting again under the same conditions was repeated, and extraction was performed three times in total.
  • the first intermediate molded body containing dichloromethane is rinsed without substantially drying (that is, in a state where no whitening is observed in the first intermediate molded body by visual observation) and without fixing both ends.
  • Dichloromethane impregnated in the first intermediate molded body by being immersed in ethanol (swelling ratio of 0.5% relative to the raw material vinylidene fluoride resin) at room temperature for 30 minutes was replaced with ethanol as a rinsing liquid. At this time, the substitution was performed while stirring the ethanol so that the ethanol was evenly distributed over the yarn. Subsequently, the operation of replacing the ethanol with a new one and substituting again under the same conditions was repeated, and the replacement was performed twice in total.
  • the ethanol was removed by air drying at room temperature for 24 hours, followed by heating in an oven at a temperature of 120 ° C. for 1 hour to remove the ethanol and a heat treatment, followed by fluorination.
  • a vinylidene resin hollow fiber porous membrane was obtained.
  • Example B2 A vinylidene fluoride resin hollow fiber porous membrane was obtained in the same manner as B1, except that isopropyl alcohol (swelling rate 0.2% with respect to the raw material vinylidene fluoride resin) was used as the rinse liquid.
  • Example B3 A vinylidene fluoride resin hollow fiber porous membrane was obtained in the same manner as in Example B1, except that hexane (swelling ratio of 0.0% relative to the raw material vinylidene fluoride resin) was used as the rinse liquid.
  • Example B4 After substituting with ethanol as the rinsing liquid, the second rinsing liquid, water (swelling ratio 0.0% of the raw material vinylidene fluoride resin) is further obtained without substantially drying the hollow fiber porous membrane containing ethanol.
  • the vinylidene fluoride resin hollow fiber porous membrane was obtained in the same manner as in Example B1 except that it was replaced with a).
  • Example B1 A vinylidene fluoride resin hollow fiber porous membrane was obtained in the same manner as in Example B1 except that dichloromethane (swelling ratio of 5.7% with respect to the raw material vinylidene fluoride resin) was used as the rinse liquid.
  • Example B2 A vinylidene fluoride resin hollow fiber porous membrane was obtained in the same manner as in Example B1, except that methanol (swelling ratio of 1.8% relative to the raw material vinylidene fluoride resin) was used as the rinse liquid.
  • Example B3 A vinylidene fluoride resin hollow fiber porous membrane was obtained in the same manner as in Example B1 except that acetone (swelling ratio of 5.0% with respect to the raw material vinylidene fluoride resin) was used as the rinse liquid.
  • Example B4 A vinylidene fluoride system was used in the same manner as in Example B1 except that a heptafluorocyclopentane-based solvent (“Zeorolla HTA” manufactured by Nippon Zeon Co., Ltd., a swelling ratio of 3.4% with respect to the raw material vinylidene fluoride resin) was used as the rinse liquid.
  • a resin hollow fiber porous membrane was obtained.
  • Example B5 As an organic liquid, a polyester plasticizer (polyester of adipic acid and 1,2-butanediol whose ends are sealed with isononyl alcohol; “D623N” manufactured by J Plus Co., Ltd., number average molecular weight of about 1800, JIS K7117- 2 (cone-flat-plate rotational viscometer) measured viscosity at 25 ° C. 3000 mPa ⁇ s, specific gravity 1.090 g / ml) and monoisonic ester plasticizer diisononyl adipate (“DINA” manufactured by J.
  • D623N polyisonic ester plasticizer diisononyl adipate
  • Example B2 except that the cooling water bath temperature Tq after melt extrusion was changed to 45 ° C. In the same manner, a vinylidene fluoride resin hollow fiber porous membrane was obtained.
  • Example B5 A vinylidene fluoride resin hollow fiber porous membrane was obtained in the same manner as in Example B5, except that dichloromethane (swelling ratio of 5.7% relative to the raw material vinylidene fluoride resin) was used as the rinse liquid.
  • Example B6 Polyvinylidene fluoride resin as a matrix polyvinylidene fluoride (PVDF-I) (powder) with a weight average molecular weight (Mw) of 6.6 ⁇ 10 5 and crystal property modification with Mw of 9.7 ⁇ 10 5
  • PVDF-II polyvinylidene fluoride
  • Example B6 A vinylidene fluoride resin hollow fiber porous membrane was obtained in the same manner as in Example B6 except that dichloromethane (swelling ratio of 5.7% with respect to the raw material vinylidene fluoride resin) was used as the rinse liquid.
  • Example B7 As an organic liquid, alkylene glycol dibenzoate, a monomeric ester plasticizer (“PB-10” manufactured by DIC Corporation, number average molecular weight of about 300, JIS K7117-2 (cone-flat plate viscometer) at 25 ° C.) A measured viscosity of 81 mPa ⁇ s and a specific gravity of 1.147 g / ml); a vinylidene fluoride resin porous membrane in the same manner as in Example B6 except that the cooling water bath temperature Tq after melt extrusion was changed to 60 ° C. Got.
  • PB-10 monomeric ester plasticizer
  • Example B7 A vinylidene fluoride resin hollow fiber porous membrane was obtained in the same manner as in Example B7, except that dichloromethane (swelling ratio of 5.7% relative to the raw material vinylidene fluoride resin) was used as the rinse liquid.
  • Example B and Comparative Example B described above extraction (and subsequent rinsing) was performed on the separated single-filamentary first intermediate molded body (vinylidene fluoride hollow fiber membrane containing an organic liquid after phase separation).
  • first intermediate molded body vinylene fluoride hollow fiber membrane containing an organic liquid after phase separation.
  • bobbin extraction is performed by reducing the dimensional shrinkage rate according to the method of the present invention. And the film characteristics by subsequent stretching were evaluated.
  • Example B8 The first intermediate molded body (length: 500 m) wound on the bobbin (core diameter: 220 mm) in Example B5 was immersed in dichloromethane for 30 minutes at room temperature while being wound on the bobbin, and the plasticizer was extracted. At this time, the extraction was performed while rotating the bobbin so that the dichloromethane was evenly distributed over the yarn. Next, the operation of replacing the dichloromethane with a new one and extracting again under the same conditions was repeated, and extraction was performed three times in total.
  • IPA isopropyl alcohol
  • IPA was removed by air drying at room temperature for 24 hours, followed by heating in an oven at a temperature of 120 ° C. for 1 hour to remove IPA and heat treatment to obtain a second intermediate molded body.
  • the bobbin diameter was freely contracted, and drying and heat treatment were performed without restricting the contraction of the yarn.
  • the second intermediate formed body is pulled out while rotating the bobbin, the first roll speed is set to 20.0 m / min, and the second roll is passed through the 60 ° C. water bath.
  • the film was stretched 1.75 times in the longitudinal direction by setting the speed to 35.0 m / min.
  • it is passed through a hot water bath controlled at a temperature of 90 ° C., the first stage relaxation rate is relaxed at 8%, and further passed through a dry heat tank controlled at a spatial temperature of 140 ° C., and the second stage relaxation rate is 1.5%. And relaxed. This was wound up to obtain a vinylidene fluoride resin hollow fiber porous membrane.
  • Example B9 A vinylidene fluoride resin hollow fiber porous membrane was obtained in the same manner as in Example B8, except that the first intermediate molded body (length: 500 m) wound on a bobbin in Example B6 was used.
  • Example B10 A vinylidene fluoride resin hollow fiber porous membrane was obtained in the same manner as in Example B8, except that the first intermediate molded body (length: 500 m) wound around the bobbin in Example B7 was used.
  • Example B8 Bobbin extraction was performed in the same manner as in Example B8, except that dichloromethane (swelling ratio of 5.7% with respect to the raw material vinylidene fluoride resin) was used as the rinsing liquid, followed by drying and heat treatment. However, due to the tightness of the yarn, the yarns bite and the yarn was crimped, and could not be used for drawing.
  • dichloromethane swelling ratio of 5.7% with respect to the raw material vinylidene fluoride resin
  • Example B9 Bobbin extraction was performed in the same manner as in Example B9, except that dichloromethane (swelling ratio of 5.7% with respect to the raw material vinylidene fluoride resin) was used as the rinsing liquid, followed by drying and heat treatment. However, due to the tightness of the yarn, the yarns bite and the yarn was crimped, and could not be used for drawing.
  • dichloromethane swelling ratio of 5.7% with respect to the raw material vinylidene fluoride resin
  • Example B10 Bobbin extraction was performed in the same manner as in Example B10, except that dichloromethane (swelling ratio of 5.7% with respect to the raw material vinylidene fluoride resin) was used as the rinsing liquid, followed by drying and heat treatment. However, due to the tightness of the yarn, the yarns bite and the yarn was crimped, and could not be used for drawing.
  • dichloromethane swelling ratio of 5.7% with respect to the raw material vinylidene fluoride resin
  • Example B11 The first intermediate molded body (length: 500 m) wound up in Example B6 was pulled out from the bobbin, passed through a 60 ° C. water bath at a first roll speed of 20.0 m / min, and a second roll speed. The film was stretched 2.5 times in the longitudinal direction at a speed of 50 m / min. Next, it is passed through a hot water bath controlled at a temperature of 90 ° C., the first stage relaxation rate is relaxed at 8%, and further passed through a dry heat tank controlled at a spatial temperature of 140 ° C., and the second stage relaxation rate is 1.5%. Was relaxed and wound on a bobbin to obtain a drawn yarn.
  • the drawn liquid was wound around a bobbin and immersed in dichloromethane at room temperature for 30 minutes to extract an organic liquid.
  • the extraction was performed while rotating the bobbin so that the dichloromethane was evenly distributed over the yarn.
  • the operation of replacing the dichloromethane with a new one and extracting again under the same conditions was repeated, and extraction was performed three times in total.
  • the drawn yarn is immersed in isopropyl alcohol (IPA), which is a rinse solution, at room temperature for 30 minutes for drawing.
  • IPA isopropyl alcohol
  • Dichloromethane impregnated in the yarn was replaced with IPA.
  • the replacement was performed while rotating the bobbin so that the IPA was evenly distributed over the yarn.
  • the operation of replacing the IPA with a new one and replacing the same under the same conditions was repeated, and the replacement was performed twice in total.
  • IPA was removed by air drying at room temperature for 24 hours, followed by heating in an oven at 120 ° C. for 1 hour to remove IPA and heat treatment to obtain a vinylidene fluoride resin hollow fiber porous membrane.
  • the bobbin diameter was freely contracted, and drying and heat treatment were performed without restricting the contraction of the yarn.
  • Example B11 Bobbin extraction was performed in the same manner as in Example B11, except that dichloromethane (swelling ratio of 5.7% with respect to the raw vinylidene fluoride resin) was used as the rinsing liquid, followed by drying and heat treatment. However, the yarn was bitten and the yarn was crimped due to the tightening of the yarn, and could not be recovered as a hollow fiber porous membrane having a uniform shape.
  • dichloromethane swelling ratio of 5.7% with respect to the raw vinylidene fluoride resin
  • Example B12 After using the first intermediate molded body (length: 500 m) wound around the bobbin in Example B1 and substituting with ethanol as the rinsing liquid, the hollow fiber porous membrane containing ethanol is substantially dried.
  • a vinylidene fluoride resin hollow fiber porous membrane was prepared in the same manner as in Example B8, except that substitution was used for water (the swelling rate of 0.0% relative to the raw material vinylidene fluoride resin) as the second rinse liquid. Obtained.
  • Example B12 Bobbin extraction was performed in the same manner as in Example B12 except that dichloromethane (swelling ratio of 5.7% with respect to the raw material vinylidene fluoride resin) was used as the rinsing liquid, followed by drying and heat treatment. However, due to the tightness of the yarn, the yarns bite and the yarn was crimped, and could not be used for drawing.
  • dichloromethane swelling ratio of 5.7% with respect to the raw material vinylidene fluoride resin
  • the results in Table 6 are obtained by bobbing a long hollow fiber membrane-like vinylidene fluoride resin porous membrane for effective extraction, and then substituting with a non-swelling solvent after extraction with a halogenated solvent.
  • the deformation of the hollow fiber membrane due to tightening is suppressed, the removal of the hollow fiber membrane is facilitated, and the vinylidene fluoride resin hollow fiber porous membrane having good water permeability despite the small pore diameter is formed.
  • the highly permeable vinylidene fluoride resin porous membrane formed by the method of the present invention is not only suitable for drainage treatment, but also for concentrating bacteria and proteins, and collecting chemically aggregated particles of heavy metals.
  • the vinylidene fluoride resin porous membrane obtained by the thermally induced phase separation method has a pore diameter continuously expanding in the film thickness direction, and a porosity is uniformly distributed in the film thickness direction.
  • the dense layer that contributes to separation characteristics or selective permeation characteristics it has excellent separation characteristics or selective permeation characteristics while maintaining fluid separation or movement of ions, etc. The characteristic that there is little resistance is given. Such characteristics are particularly suitable for the separation applications described above in general.
  • (filtration) has a surface pore diameter, water permeability and mechanical strength suitable for water treatment, and is represented by a large critical filtration flux.
  • a vinylidene fluoride resin porous membrane that exhibits good water permeability maintaining performance even during continuous filtration of turbid water and has a large water permeability despite the small surface pore diameter of the water to be treated.
  • the vinylidene fluoride resin porous membrane of the present invention is suitable for (filtered) water treatment as described above, but the pore diameter is continuously increased in the film thickness direction and the porosity is the film thickness. It has a characteristic of being uniformly distributed in the vertical direction.
  • the porous membrane of the present invention is not limited to (filtered) water treatment, but can be used for concentration of bacteria, proteins, etc., recovery of chemically aggregated particles of heavy metals, separation membrane for oil-water separation and gas-liquid separation Also, it can be suitably used as a battery diaphragm such as a lithium ion secondary battery and a solid electrolyte support.

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Abstract

La présente invention concerne une membrane poreuse en résine de fluorure de vinylidène caractérisée en ce qu'elle possède deux surfaces principales, entre lesquelles une certaine épaisseur est prise en sandwich, et en ce qu'elle possède, sur son côté qui fait face à l'une des surfaces principales, une couche dense qui a un petit diamètre de pores et qui régit les performances de filtration, ayant une structure asymétrique de réseau à gradient dans laquelle le diamètre de pores augmente continuellement de la surface vers l'autre surface, et satisfaisant aux exigences (a) à (c) suivantes : (a) la partie de la couche dense qui possède une épaisseur de 5 µm et s'étend continuellement de la surface a une porosité (A1) de 60 % ou plus ; (b) la surface a un diamètre de pores de surface (P1) de 0,30 µm ou moins ; et (c) le rapport de la quantité d'eau qui a traversé une longueur de test (L) de 200 mm dans les conditions d'une pression différentielle de 100 kPa et d'une température de l'eau de 25°C, la quantité d'eau étant une valeur convertie (Q (m/jour)) calculée pour une porosité globale (A2) de 80 %, à la puissance quatre du diamètre de pores de surface (P1) de la surface (P14 (µm4)), Q/P14, est 5×104 (m/jour∙µm4) ou plus.
PCT/JP2010/065205 2009-09-04 2010-09-06 Membrane poreuse en résine de fluorure de vinylidène et son procédé de production WO2011027878A1 (fr)

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CN201080039112.8A CN102548647B (zh) 2009-09-04 2010-09-06 1,1-二氟乙烯系树脂多孔膜及其制造方法
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CN110416470A (zh) * 2019-08-07 2019-11-05 江苏厚生新能源科技有限公司 电池隔膜及其制备工艺、降低二氯甲烷消耗量的改进方法
CN110416470B (zh) * 2019-08-07 2022-03-11 江苏厚生新能源科技有限公司 电池隔膜及其制备工艺、降低二氯甲烷消耗量的改进方法
CN114269458A (zh) * 2019-08-29 2022-04-01 东丽株式会社 聚偏二氟乙烯系多孔质分离膜的亲水化方法
CN114269458B (zh) * 2019-08-29 2024-02-27 东丽株式会社 聚偏二氟乙烯系多孔质分离膜的亲水化方法

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