Polymer Composition and Porous Membrane

Abstract

A polymer composition containing a polymer (B) obtained by polymerizing a monomer composition containing: a methacrylic acid ester macromonomer (b1) represented by the following formula (1); and another monomer (b2). Also, a porous membrane formed from a membrane forming polymer (A) and the aforementioned polymer composition.

##STR00001##

Claims

1. A polymer composition comprising: a membrane forming polymer (A); and a polymer (B) obtained by polymerizing a monomer composition containing a methacrylic acid ester macromonomer (b1) represented by the following Formula (1) ##STR00004## and another monomer (b2), where R and R.sup.1 to R.sup.n of Formula (1) each independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group, Z is a terminal group, and n is an integer from 2 to 10,000.

2. The polymer composition according to claim 1, further comprising a membrane forming polymer (A).

3. The polymer composition according to claim 2, wherein the membrane forming polymer (A) is a fluorine-containing polymer.

4. The polymer composition according to claim 1, wherein the other monomer (b2) is (meth)acrylic acid or a (meth)acrylate.

5. The polymer composition according to claim 1, wherein a contact angle of pure water on an outer surface of a porous membrane formed from the polymer composition is 75 or less.

6.-10. (canceled)

Description

EXAMPLES

[0160] Hereinafter, the invention will be described in detail with reference to Examples. Incidentally, in the following, the composition and structure of the macromonomer (b1) and the polymer, the Mw of the polymer, the Mn and Mw/Mn of the macromonomer (b1) and the polymer were evaluated by the following methods.

[0161] In addition, in the following, the parts and the % indicate the parts by mass and the % by mass, respectively.

[0162] (1) Composition and Structure of Macromonomer (b1) and Polymer

[0163] The composition and structure of the macromonomer (b1) and the polymer were analyzed by .sup.1H-NMR (product name: JNM-EX270 manufactured by JEOL Ltd.).

[0164] (2) Mw of Membrane Forming Polymer (A)

[0165] The Mw of the membrane forming polymer (A) was determined using a GPC (HLC-8020 (trade name) manufactured by TOSOH CORPORATION) under the following conditions.

[0166] Column: TSK GUARD COLUMN a (7.8 mm40 mm) and three TSK-GEL -M (7.8300 mm) are connected in series

[0167] Eluent: DMF 20 mM LiBr solution

[0168] Measuring temperature: 40 C.

[0169] Flow rate: 0.1 mL/minute

[0170] Incidentally, the Mw was determined using a calibration curve created using the polystyrene standards manufactured by TOSOH CORPORATION (nine kinds of Mp (peak top molecular weight) of 76,969,900, 2,110,000, 1,260,000, 775,000, 355,000, 186,000, 19,500, 1,050 and the styrene monomer (M=104) manufactured by NS styrene Monomer Co., Ltd.).

[0171] (3) Mn and Mw/Mn of Macromonomer (b1), Controlled Polymerization Polymer (b1) and Polymer (B)

[0172] The Mn and Mw/Mn of the macromonomer (b1) and the controlled polymerization polymer (b1) were determined using a GPC (HLC-8220 (trade name) manufactured by TOSOH CORPORATION) under the following conditions.

[0173] Column: TSK GUARD COLUMN SUPER HZ-L (4.635 mm) and two TSK-GEL SUPER HZM-N (6.0150 mm) are connected in series

[0174] Eluent: chloroform, DMF, or THF

[0175] Measuring temperature: 40 C.

[0176] Flow rate: 0.6 mL/minute

[0177] Incidentally, the Mw and Mn were determined using a calibration curve created using polymethyl methacrylate manufactured by Polymer Laboratories Ltd. (four kinds of Mp (peak top molecular weight) of 141,500, 55,600, 10,290 and 1,590).

[0178] (4) Contact Angle

[0179] The contact angle of pure water on the porous membrane was measured by the following method.

[0180] The test piece of porous membrane was placed on a sample table of a contact angle measuring device (product name: DSA-10 manufactured by Kruss GmbH). Subsequently, the state of the water droplet in 3 seconds after a drop (10 l) of pure water (for LC/MS manufactured by Wako Pure Chemical Industries, Ltd.) was dropped on the outer surface of the sample for the contact angle measurement was photographed using a CCD camera attached to the device. The contact angle of the water droplet of the photograph thus obtained was determined by an automatic measurement using the image processing program incorporated in the contact angle measuring device.

[0181] (5) The Average Pore Size

[0182] Five or more arbitrary locations in a range of 500 m500 m were selected from the outer surface of the porous membrane, the pore size of 30 pores which were present at the five locations and randomly selected was measured, and the average value of the pore sizes measured was adopted as the average pore size.

[0183] (6) Measurement of Flux

[0184] The test piece of porous membrane was cut into a circle having a diameter of 4.2 cm and impregnated with ethanol by being immersed in ethanol (manufactured by Wako Pure Chemical Industries, Ltd., special grade reagent) for 20 minutes. Subsequently, the test piece of porous membrane impregnated with ethanol was immersed in deionized water for two hours or longer and inserted into a stainless holder with tank (KST-47 (trade name) manufactured by ADVANTEC Co. Ltd., effective membrane area of 12.5 cm.sup.2). The inside of the stainless holder with tank was filled with about 150 ml of deionized water, the top cap was then sealed with a clamp so that there is no leakage by pressure, and the flux was calculated from the permeable water volume per unit time measured using the air at a measuring pressure of 0.1 MPa using the following Equation. A greater flux value indicates higher water permeating performance.

Flux=L/(StP)

Flux: flux of pure water (m.sup.3/m.sup.2/s/Pa)
L: permeable volume of pure water (m.sup.3)
S: effective membrane area (m.sup.2)
t: permeation time (s)
P: measuring pressure (Pa)

[0185] (7) Fine Particle Rejecting Rate

[0186] The porous membrane used in the flux measurement was inserted into a stainless holder with tank (KST-47 (trade name) manufactured by ADVANTEC Co. Ltd.), an evaluation stock solution prepared by dispersing polystyrene latex particles having an average particle size of 0.132 m manufactured by MAGS FAIR, nominal particle size of 0.132 m) in deionized water so as to have a concentration of 25 ppm was filled in the tank, the evaluation stock solution was filtered through the porous membrane inserted at a measuring pressure of 0.1 MPa, and the fine particle rejecting rate was calculated from the absorbance of the evaluation stock solution and the filtrate measured at a wavelength of 320 nm using the following Equation:

Rjc=[(A1A2)/A1]100

Rjc: fine particle rejecting rate (%)
A1: absorbance of evaluation stock solution (abs)
A2: absorbance of filtrate (abs).

[0187] For the absorbance measurement, a spectrophotometer (LAMBDA850 manufactured by Perkin Elmer Co., Ltd.) was used.

(Synthesis Example 1) Synthesis of Cobalt Chain Transfer Agent CoBF-1

[0188] Into a reactor equipped with a stirrer, 1.00 g of cobalt(II) acetate tetrahydrate (manufactured by Wako Pure Chemical Industries, Ltd., Wako special grade), 1.93 g of diphenyl glyoxime (manufactured by Tokyo Chemical Industry Co., Ltd., EP grade), and 80 ml of diethyl ether (manufactured by KANTO KAGAKU, special grade) that was deoxygenated by nitrogen bubbling in advance were introduced under a nitrogen atmosphere and stirred for 30 minutes at room temperature. Subsequently, 10 ml of boron trifluoride diethyl ether complex (manufactured by Tokyo Chemical Industry Co., Ltd., EP grade) was added thereto, and the mixture was further stirred for 6 hours. The mixture was filtered, and the solid was washed with diethyl ether (manufactured by KANTO KAGAKU, special grade) and vacuum dried for 15 hours, thereby obtaining 2.12 g of the cobalt chain transfer agent CoBF-1 of a red-brown solid.

(Synthesis Example 2) Synthesis of Dispersant 1

[0189] Into a reactor equipped with a stirrer, a cooling tube, and a thermometer, 61.6 parts of 17% aqueous solution of potassium hydroxide, 19.1 parts of methyl methacrylate (trade name: ACRYESTER M manufactured by Mitsubishi Rayon Co., Ltd.), and 19.3 parts of deionized water were introduced. Subsequently, the liquid in the reactor was stirred at room temperature, the exothermic peak thereof was confirmed, and then the liquid was further stirred for 4 hours. Thereafter, the reaction mixture in the reactor was cooled to room temperature, thereby obtaining an aqueous solution of potassium methacrylate.

[0190] Subsequently, 900 parts of deionized water, 70 parts of a 42% aqueous solution of sodium 2-sulfoethyl methacrylate (trade name: ACRYESTER SEM-Na manufactured by Mitsubishi Rayon Co., Ltd.), 16 parts of the above aqueous solution of potassium methacrylate, and 7 parts of methyl methacrylate (trade name: ACRYESTER M manufactured by Mitsubishi Rayon Co., Ltd.) were introduced into a polymerization apparatus equipped with a stirrer, a cooling tube, and a thermometer and stirred, the temperature thereof was raised to 50 C. while purging the inside of the polymerization apparatus with nitrogen. Thereto, 0.053 part of 2,2-azobis(2-methyl propionamidine) dihydrochloride (trade name: V-50 manufactured by Wako Pure Chemical Industries, Ltd.) was added as the polymerization initiator and the temperature thereof was further raised to 60 C. After the polymerization initiator was introduced, 1.4 parts of methyl methacrylate (trade name: ACRYESTER M manufactured by Mitsubishi Rayon Co., Ltd.) was added thereto every 15 minutes five times in total in a divided manner. Thereafter, the liquid in the polymerization apparatus was held for six hours at 60 C. while stirring, then cooled to room temperature, thereby obtaining the dispersant 1 that was a clear aqueous solution and contained the solid matter at 8%.

(Synthesis Example 3) Synthesis of Macromonomer (b1-1)

[0191] Into a flask with a cooling tube, 100 parts of methyl methacrylate (trade name: ACRYESTER M manufactured by Mitsubishi Rayon Co., Ltd.), 150 parts of deionized water, 1.39 parts of sodium sulfate, 1.53 parts of the dispersant 1, and 0.00075 part of CoBF-1 were introduced. The CoBF-1 was dissolved in a state in which the liquid in the flask was warmed to 70, and the inside of the flask was purged with nitrogen by nitrogen bubbling. Subsequently, 1 part by mass of AlBN was added thereto, and the mixture was held for 6 hours in a state in which the internal temperature was maintained at 70 C., thereby completing the polymerization. Thereafter, the polymerization reaction mixture was cooled to room temperature and further filtered to recover the polymer. The polymer thus obtained was washed with water and vacuum dried for the night at 50 C., thereby obtaining the macromonomer (b1-1). The Mn of the macromonomer (b1-1) was 11,000, the Mw/Mn was 2.0, and the average degree of polymerization was (110). The introduction rate of the terminal double bond into the macromonomer (b1-1) was almost 100%. In the case of the macromonomer (b1-1), R in Formula (1) above was a methyl group.

(Synthesis Example 4) Synthesis of Controlled Polymerization Polymer (b1-1)

[0192] In to a flask with a cooling tube, 100 parts of MMA, 0.221 part of 2-cyano-2-propyl benzothionate (manufactured by Sigma-Aldrich Co., LLC., purity of 97%>HPLC), and 100 parts of toluene (manufactured by Wako Pure Chemical Industries, Ltd., special grade reagent) as the solvent (C1) were introduced, the inside of the flask was purged with nitrogen by nitrogen bubbling. Subsequently, 0.1 part of AIBN (manufactured by Wako Pure Chemical Co., Wako special grade) was added thereto as the radical polymerization initiator in a state in which the liquid in the flask was heated and the internal temperature was maintained at 70 C., and the mixture was then held for four hours, the temperature thereof was subsequently raised to 80 C., and the mixture was held for 30 minutes, thereby completing the polymerization. Thereafter, the polymerization reaction mixture was cooled to room temperature and reprecipitated with a great amount of methanol (manufactured by Wako Pure Chemical Industries, Ltd., special grade reagent). The polymer precipitated by the reprecipitation was recovered and vacuum dried for the night under the conditions of 50 C. and 50 mmHg (6.67 kPa), thereby obtaining the controlled polymerization polymer (b1-1). The Mn of the controlled polymerization polymer (b1-1) was 11,000, and the Mw/Mn was 1.1.

(Synthesis Example 5) Synthesis of Polymer (B-1)

[0193] Into a flask with a cooling tube, a monomer composition containing 50 parts of the macromonomer (b1-1), 50 parts of PME-400 (trade name: BLEMMER PME-400 manufactured by NOF CORPORATION) as the other monomer (b2), and 150 parts of toluene (manufactured by Wako Pure Chemical Industries, Ltd., special grade reagent) as the solvent (C2) was introduced, and the inside of the flask was purged with nitrogen by nitrogen bubbling. Subsequently, 0.1 part of AlBN (manufactured by Wako Pure Chemical Industries, Ltd., Wako special grade) as the radical polymerization initiator was added to the monomer composition in a state in which the monomer composition was warmed and the internal temperature thereof was maintained at 70 C., and the mixture was held for 4 hours, the temperature thereof was subsequently raised to 80 C., and the mixture was held for 30 minutes, thereby completing the polymerization. Thereafter, the polymerization reaction mixture was cooled to room temperature and reprecipitated with a great amount of hexane (manufactured by Wako Pure Chemical Co., special grade reagent). The polymer precipitated by the reprecipitation was recovered and vacuum dried for the night under the conditions of 50 C. and 50 mmHg (6.67 kPa), thereby obtaining the polymer (B-1).

[0194] The yield of the polymer (B-1) thus obtained was about 100%. For the GPC measurement, chloroform was used as the eluent. The Mn of the polymer (B-1) was 14,000, and the Mw/Mn was 2.1. The content of the macromonomer (b1-1) unit in the polymer (B-1) determined by .sup.1H-NMR was 50%. The evaluation results are presented in Table 1.

TABLE-US-00001 TABLE 1 Syn- Syn- Syn- Syn- Syn- Syn- Syn- Syn- Syn- Syn- Syn- thesis thesis thesis thesis thesis thesis thesis thesis thesis thesis thesis Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- ple 5 ple 6 ple 7 ple 8 ple 9 ple 10 ple 11 ple 12 ple 13 ple 14 ple 15 Polymer (B) or polymer (B) B-1 B-2 B-3 B-4 B-5 B-6 B-7 B-8 B-1 B-2 B-3 Mono- Macromonomer (b1-1) 50 70 70 70 70 70 50 40 mer Controlled polymerization 50 compo- polymer (b1-1) sition Another MMA 20 30 50 70 (parts) monomer (b-2) PME-100 30 PME-400 50 30 50 30 HEMA 30 HEA 30 30 30 50 MAA 30 Solvent (C2) TOL 150 150 150 150 150 150 DMF 150 150 DMAc 150 150 150 Eval- Compo- Macromonomer 50 69 70 71 67 75 75 76 uation sition of (b1-1) unit results polymer Controlled 77 (B) or polymerization polymer polymer (B) (b1-1) unit Another MMA 50 70 monomer PME-100 50 31 30 (b-2) unit PME-400 50 30 HEMA 29 HEA 25 25 24 23 MAA 33 Molecular weight Mn 14,000 12,000 9,000 10,000 11,000 19,000 21.000 28,000 70,000 50,000 18,800 and molecular Mw/Mn 2.1 2.5 2.5 2.3 2.4 1.9 1.9 1.9 1.4 1.3 1.3 weight distribution

[0195] The abbreviations in Table 1 indicate the following compounds, respectively.

MMA: methyl methacrylate (trade name: ACRYESTER M manufactured by Mitsubishi Rayon Co., Ltd.)
PME-100: (BLEMMER PME-100 (trade name) manufactured by NOF CORPORATION)
PME-400: (BLEMMER PME-400 (trade name) manufactured by NOF CORPORATION)
HEMA: 2-hydroxyethyl methacrylate (ACRYESTER HOMA manufactured by Mitsubishi Rayon Co., Ltd.)
HEA: 2-hydroxyethyl acrylate (manufactured by Wako Pure Chemical Industries, Ltd., Wako first grade)
MAA: methacrylic acid (trade name: methacrylic acid manufactured by Mitsubishi Rayon Co., Ltd.)
TOL: toluene (manufactured by Wako Pure Chemical Industries, Ltd., special grade reagent)
THF: tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd., special grade reagent)
DMF: N,N-dimethylformamide (manufactured by Wako Pure Chemical Industries, Ltd., special grade reagent)
DMAc: N,N-dimethylacetamide (manufactured by Wako Pure Chemical Industries, Ltd., Wako first grade)

(Synthesis Examples 6, 7, 13 and 14) Synthesis of Polymers (B-2), (B-3), (B-1), and (B-2)

[0196] The polymers (B-2), (B-3), (B-1), and (B-2) were obtained in the same manner as Synthesis Example 5 except that the monomer compositions having the compositions presented in Table 1 were used. The yield of the polymers (B-2), (B-3), (B-1), and (B-2) thus obtained was almost 100%. For the GPC measurement, chloroform was used as the eluent. The evaluation results of the polymers (B-2), (B-3), (B-1), and (B-2) are presented in Table 1.

(Synthesis Example 8) Synthesis of Polymer (B-4)

[0197] The polymer (B-4) was obtained in the same manner as Synthesis Example 5 except that the monomer composition having the composition presented in Table 1 and the solvent (C2) were used and deionized water was used instead of hexane for reprecipitation of the polymer. The yield of the polymer (B-4) thus obtained was almost 100%. For the GPC measurement, DMF was used as the eluent. The evaluation results of the polymer (B-4) are presented in Table 1.

(Synthesis Example 9) Synthesis of Polymer (B-5)

[0198] The polymer (B-5) was obtained in the same manner as Synthesis Example 7 except that the monomer composition having the composition presented in Table 1 was used. The yield of the polymer (B-5) thus obtained was almost 100%. For the GPC measurement, chloroform was used as the eluent. The evaluation results of the polymer (B-5) are presented in Table 1.

(Synthesis Examples 10, 11, and 12) Synthesis of Polymers (B-6), (B-7), and (B-8)

[0199] The polymers (B-6), (B-7), and (B-8) were obtained in the same manner as Synthesis Example 5 except that the monomer compositions having the compositions presented in Table 1 and the solvent (C2) were used and deionized water was used instead of hexane for reprecipitation of the polymers. The yield of the polymers (B-6), (B-7), and (B-8) thus obtained was almost 100%. For the GPC measurement, THF was used as the eluent. The evaluation results of the polymers (B-6), (B-7), and (B-8) are presented in Table 1.

(Synthesis Example 15) Synthesis of Polymer (B-3)

[0200] The polymer (B-3) was obtained in the same manner as Synthesis Example 4 except that the monomer composition having the composition presented in Table 1 was used. The yield of the polymer (B-3) thus obtained was almost 100%. For the GPC measurement, DMF was used as the eluent. The evaluation results of the polymer (B-3) are presented in Table 1.

Example 1

[0201] In a glass container, 16 parts of Kynar 761A (manufactured by Arkema Inc., PVDF homopolymer, trade names, Mw=550,000) as the membrane forming polymer (A), 12 parts of the polymer (B-1) as the polymer (B), and 72 parts of NMP (manufactured by Wako Pure Chemical Industries, Ltd., Wako special grade) as the solvent (C3) were blended and stirred for 10 hours at 50 C. using a stirrer, thereby preparing the membrane forming solution.

[0202] The membrane forming solution thus obtained was allowed to stand for one day at room temperature, subsequently coated on a glass substrate using a bar coater so as to have a thickness of 125 m, thereby obtaining a coating film layered body. The coating film layered body was immersed in a coagulating bath containing 70 parts of deionized water and 30 parts of NMP as the coagulating bath solvent at room temperature.

[0203] The coating film layered body was allowed to stand in the coagulating bath for 5 minutes, and the coagulated product of coating film was then peeled off from the glass substrate and washed with hot water at 80 C. for 5 minutes to remove NMP, thereby fabricating the porous membrane having a flat membrane shape. The porous membrane having a flat membrane shape thus obtained was dried for 20 hours at 70 C., thereby obtaining a test piece of porous membrane having a thickness of 95 m. The contact angle of water on the outer surface of the test piece of porous membrane was 60, and the average pore size was 60 nm. The evaluation results are presented in Table 2.

TABLE-US-00002 TABLE 2 Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- ple 1 ple 2 ple 3 ple 4 ple 5 ple 6 ple 7 ple 8 Membrane Polymer Kind Kyner Kyner Kyner Kyner Kyner Kyner Kyner Kyner forming (A) 761A 761A 301F 761A 761A 761A 761A 761A solution Content 16 17 16 16 16 16 16 16 (parts) Polymer Kind B-1 B-1 B-1 B-1 B-1 B-2 B-3 B-4 (B) Content 12 6 12 12 12 12 12 12 (parts) Solvent Kind NMP NMP NMP DMF DMAc NMP NMP DMF (C3) Content 72 77 72 72 72 72 72 72 (parts) Coag- Coagulating Kind NMP NMP NMP DMF DMAc NMP NMP DMF ulating bath Content 30 30 30 30 30 30 30 30 bath solvent (parts) Deionized Content 70 70 70 70 70 70 70 70 water (parts) Evaluation Contact 60 61 60 60 62 63 60 45 results of angle porous () membrane Pore 60 68 77 55 57 90 53 32 size (nm) Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- ple 9 ple 10 ple 11 ple 12 ple 13 ple 13 ple 14 ple 15 Membrane Polymer Kind Kyner Kyner Kyner Kyner Kyner Kyner Kyner Kyner forming (A) 761A 761A 761A 761A 761A 761A 761A 762A Content 16 16 17 16 17 16 17 12 (parts) Polymer Kind B-5 B-6 B-6 B-7 B-8 B-8 B-8 B-6 (B) Content 12 12 6 12 6 12 6 4 (parts) Solvent Kind DMAc DMAc DMAc DMAc DMAc DMAc DMAc DMAc (C3) Content 72 72 77 72 77 72 77 84 (parts) Coag- Coagulating Kind DMAc DMAc DMAc DMAc DMAc DMAc DMAc DMAc ulating bath Content 30 30 30 30 30 30 30 0 bath solvent (parts) Deionized Content 70 70 70 70 70 70 70 100 water (parts) Evaluation Contact 51 48 45 52 50 53 46 73 results of angle porous () membrane Pore 48 30 50 36 68 31 49 45 size (nm)

[0204] The abbreviations in Table 2 indicate the following compounds, respectively.

Kynar 761A: PVDF homopolymer (manufactured by Arkema Inc., trade name, Mw=550,000)
Kynar 301F: PVDF homopolymer (manufactured by Arkema Inc., trade name, Mw=600,000)
NMP: N-methylpyrrolidone (manufactured by Wako Pure Chemical Industries, Ltd., Wako special grade)
DMF: N,N-dimethylformamide (manufactured by Wako Pure Chemical Industries, Ltd., special grade reagent)
DMAc: N,N-dimethylacetamide (manufactured by Wako Pure Chemical Industries, Ltd., Wako first grade)

Examples 2 to 15

[0205] The test pieces of porous membrane were obtained in the same manner as in Example 1 except that those presented in Table 2 were used as the membrane forming solution and the coagulating bath. The evaluation results thereof are presented in Table 2.

Example 16

[0206] The flux was measured using the test piece of porous membrane obtained in Example 15, and it was 2.2110.sup.9 (m.sup.3/m.sup.2/s/Pa). In addition, the rejecting rate of the same test piece of porous membrane with respect to polystyrene fine particles of 0.132 m was 99.9%.

Comparative Examples 1 to 6

[0207] The test pieces of porous membrane were obtained in the same manner as in Example 1 except that those presented in Table 3 were used as the membrane forming solution and the coagulating bath. The evaluation results thereof are presented in Table 3.

Comparative Example 7

[0208] The flux was measured using the test piece of porous membrane obtained in Comparative Example 6 in the same manner as in Example 16, and it was 1.4310.sup.9 (m.sup.3/m.sup.2/s/Pa).

[0209] In addition, the rejecting rate of the same test piece of porous membrane with respect to polystyrene fine particles of 0.132 m was 99.0%.

TABLE-US-00003 TABLE 3 Comparative Comparative Comparative Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Membrane Polymer (A) Kind Kyner 761A Kyner 761A Kyner 301F Kyner 761A Kyner 761A Kyner 762A forming Content 16 17 16 16 16 12 solution (parts) Polymer (B) Kind B-1 B-1 B-1 B-1 B-2 B-3 Content 12 6 12 12 12 4 (Parts) Solvent (C3) Kind NMP NMP NMP DMF NMP DMAc Content 72 77 72 72 72 84 (parts) Coagulating Coagulating Kind NMP NMP NMP DMF NMP DMAc bath bath Content 30 30 30 30 30 0 solvent (parts) Deionized Content 70 70 70 70 70 100 water (parts) Evaluation results of Contact 75 78 76 76 82 83 porous membrane angle () Pore size 750 700 720 690 590 50 (nm)

[0210] The abbreviations in Table 3 indicate the following compounds, respectively.

Kynar 761A: PVDF homopolymer (manufactured by Arkema Inc., trade name, Mw=550,000)
Kynar 301F: PVDF homopolymer (manufactured by Arkema Inc., trade name, Mw=600,000)
NMP: N-methylpyrrolidone (manufactured by Wako Pure Chemical Industries, Ltd., Wako special grade)
DMF: N,N-dimethylformamide (manufactured by Wako Pure Chemical Industries, Ltd., special grade reagent)
DMAc: N,N-dimethylacetamide (manufactured by Wako Pure Chemical Industries, Ltd., Wako first grade)

[0211] In Comparative Example 1, the polymer (B-1) using MMA instead of the macromonomer (b1-1) was used, thus the average pore size of the porous membrane thus obtained was 750 nm to be great, and it was not possible to obtain a porous membrane suitable for obtaining a membrane exhibiting favorable fractionation performance and high water permeability.

[0212] In Comparative Example 2, the polymer (B-1) using MMA instead of the macromonomer (b1-1) was used, thus the average pore size of the porous membrane thus obtained was 750 nm to be great and the contact angle of pure water thereon was 78 to be great, and it was not possible to obtain a porous membrane suitable for obtaining a membrane exhibiting favorable fractionation performance and high water permeability.

[0213] In Comparative Example 3, the polymer (B-1) using MMA instead of the macromonomer (b1-1) was used and the kind of the polymer (A) was changed, but the average pore size of the porous membrane thus obtained was 700 nm to be great and the contact angle of pure water thereon was 76 to be great, and thus it was not possible to obtain a porous membrane suitable for obtaining a membrane exhibiting favorable fractionation performance and high water permeability.

[0214] In Comparative Example 4, the polymer (B-1) using MMA instead of the macromonomer (b1-1) was used and the kind of the solvent (C3) of the membrane forming solution and the kind of the coagulating bath solvent were changed, but the average pore size of the porous membrane thus obtained was 690 nm to be great and the contact angle of pure water thereon was 76 to be great, and thus it was not possible to obtain a porous membrane suitable for obtaining a membrane exhibiting favorable fractionation performance and high water permeability.

[0215] In Comparative Example 5, the polymer (B-2) using MMA instead of the macromonomer (b1-1) was used, but the average pore size of the porous membrane thus obtained was 590 nm to be great and the contact angle of pure water thereon was 82 to be great, and thus it was not possible to obtain a porous membrane suitable for obtaining a membrane exhibiting favorable fractionation performance and high water permeability.

[0216] In Comparative Example 6, the polymer (B-3) using the controlled polymerization polymer (b1-1) instead of the macromonomer (b1-1) was used, and the average pore size of the porous membrane thus obtained was 60 nm to be favorable but the contact angle of pure water thereon was 83 to be great, and thus it was not possible to obtain a porous membrane suitable for obtaining a membrane exhibiting favorable fractionation performance and high water permeability.

[0217] In addition, in Comparative Example 7, a test piece of porous membrane exhibiting a great contact angle of pure water of 83 was used, and thus the rejecting rate of the test piece of porous membrane with respect to polystyrene fine particles of 0.132 m was 99.0% to be high but the flux of the test piece of porous membrane was 1.4310.sup.9 (m.sup.3/m.sup.2/s/Pa) to be lower as compared to Example 15, and thus it was not possible to obtain a porous membrane for obtaining a membrane exhibiting high water permeability.

INDUSTRIAL APPLICABILITY

[0218] According to the invention, it is possible to obtain a polymer composition and a porous membrane suitable for obtaining a membrane exhibiting favorable fractionation performance and high water permeability by using a polymer easily obtained by a usual radical polymerization.