Ion-exchange membrane

Abstract

A polymerizable composition for forming an ion-exchange resin precursor, the polymerizable composition containing a monomer component and polyethylene particles in an amount of 50 to 120 parts by mass per 100 parts by mass of the monomer component, wherein the monomer component contains an aromatic monomer for introducing ion-exchange groups and a nitrogen-containing aliphatic monomer, the nitrogen-containing aliphatic monomer being present in an amount of 10 to 35% by mass in said monomer component. An ion-exchange membrane is produced by applying the polymerizable composition onto a polyolefin type filament base material and polymerizing the polymerizable composition to form an ion-exchange resin precursor and, thereafter, introducing ion-exchange groups into the precursor.

Claims

1. An ion-exchange membrane in which an ion exchanger is filled in the voids in the polyolefin type filament base material, wherein: said ion-exchange membrane has a water permeability of not more than 50 ml/(m.sup.2 hour) as measured by using the water under a pressure of 0.1 MPa; said the ion exchanger contains an aromatic ion-exchange resin and a polyethylene as the resin components; and said aromatic ion-exchange resin contains a constituent unit derived from the nitrogen-containing aliphatic monomer, wherein said polyethylene is unmodified polyethylene, wherein said aromatic ion-exchange resin has a sulfonic acid group as a cation-exchange group, and wherein said unmodified polyethylene is contained in an amount of 50 to 120 parts by mass per 100 parts by mass of a monomer component of said aromatic ion-exchange resin.

Description

EXAMPLES

(1) The invention will now be described by the following Experimental Examples.

(2) Properties of the filament base materials and of the ion-exchange membranes were measured by the following methods.

1. Melting Points of the Filament Base Materials and of the Polyethylene Particles

(3) Measured by using the DSC-220C manufactured by Seiko Instruments Inc. The base material was punched into a circular shape 5 mm in diameter. Several circular materials were overlapped one upon the other to be 3 mg while the polyethylene particles were weighed to be 3 mg and were used as a sample for measurement. They were laid on an open sample pan made of aluminum having a diameter of 5 mm, and on which a clamping cover was placed and was fitted in the aluminum pan using a sample sealer. In a nitrogen atmosphere, the temperature was elevated from 30° C. up to 180° C. at a rate of 10° C./min. to take a measurement. The temperature at a maximum point on a melting endothermic curve was regarded to be the melting point of the base material. When there were a plurality of peaks on the melting curve, the temperature of a peak having the largest peak area was regarded to be the melting point of the base material.

2. Opening Area of the Filament Base Material

(4) Calculated from the diameter (μm) of the filament constituting the base material and the mesh count in compliance with the following formula,
Opening area (%)=(opening).sup.2/(opening+filament diameter).sup.2  (1)
wherein,
opening (μm)=25400/mesh count−filament diameter (μm),
mesh count=number of filaments per inch.

3. Water Permeability of the Ion-Exchange Membrane

(5) The ion-exchange membrane was held in a cylindrical cell, 50 ml of water was poured from the upper part thereof, and a pressure of 0.1 MPa was applied from the upper side. In this state, the amount of water W.sub.pw permeating through the ion-exchange membrane in an hour was measured, and the water permeability was calculated in compliance with the following formula. In this case, the effective area of the membrane was 12.6 cm.sup.2.
Water permeability (ml/(m.sup.2×hour))=W.sub.pw/(S×t)  (2)
wherein, S: effective area (m.sup.2) of the membrane, t: testing time (hour).

4. Ion-Exchange Capacity and Water Content of the Ion-Exchange Membrane

(6) The ion-exchange membrane was dipped in a 1 mol/L-HCl aqueous solution for not less than 10 hours.

(7) Thereafter, in the case of the cation-exchange membrane, the counter ions of the ion-exchange groups were substituted for the sodium ions from the hydrogen ions in a 1 mol/L-NaCl aqueous solution, and the amount of the free hydrogen ions (A mol) was determined by a potentiometric titrator (COMTITE-900 manufactured by Hiranuma Sangyo Co., Ltd.) by using a sodium hydroxide aqueous solution.

(8) On the other hand, in the case of the anion-exchange membrane, the counter ions were substituted for the nitric acid ions from the chloride ions in a 1 mol/L—NaNO.sub.3 aqueous solution, and the amount of the free chloride ions (A mol) was determined by the potentiometric titrator (COMTITE-900 manufactured by Hiranuma Sangyo Co., Ltd.) by using a silver nitrate aqueous solution.

(9) Next, the same ion-exchange membrane was dipped in the 1 mol/L-NaCl aqueous solution for not less than 4 hours, and was washed with the ion-exchanged water to a sufficient degree. Thereafter, the water on the surface was wiped off with a tissue paper, and the mass (Wg) of the membrane was measured while it was wet. Moreover, the ion-exchange membrane was dried at 60° C. for 5 hours under reduced pressure, and was measured for its weight (Dg) while it was dry. Based on the above measured values, the ion-exchange capacity and water content of the ion-exchange membrane were found in compliance with the following formulas,
Ion-exchange capacity [meq/g−dry mass]=A×1000/DWater content [%]=100×(W−D)/D

5. Thickness of the Ion-Exchange Membrane

(10) The ion-exchange membrane was dipped in a 0.5 mol/L-NaCl aqueous solution for not less than 4 hours. Thereafter, the water on the surface of the membrane was wiped off with a tissue paper, and the thickness of the membrane was measured by using a micrometer MED-25PJ (manufactured by Mitsutoyo Co.).

6. Resistance of the Ion-Exchange Membrane

(11) The ion-exchange membrane was held in a 2-compartment cell having platinum black electrodes. The cell was filled with a 0.5 mol/L-NaCl aqueous solution on both sides of the ion-exchange membrane, and the resistance across the electrodes was measured at 25° C. by using an AC bridge circuit (at a frequency of 1,000 cycles per sec.). A membrane resistance (Ω.Math.cm.sup.2) was found from a difference between the resistance across the electrodes in this case and the resistance across the electrodes measured without installing the ion-exchange membrane. The ion-exchange membrane used for the above measurement was the one that had been equilibrated, in advance, in a 0.5 mol/L-NaCl aqueous solution.

7. Viscosity of the Polymerizable Composition

(12) The polymerizable composition was measured for its viscosity at 25° C. by using a single cylindrical rotary viscometer, VISCOTESTER VT-06, (manufactured by RION Co., Ltd.).

8. Current Efficiency of the Ion-Exchange Membrane

(13) In the case of the cation-exchange membrane, there was used a 2-compartment cell having the following constitution.

(14) Anode (Pt plate) (0.5 mol/L-NaOH aqueous solution)/cation-exchange membrane/(3.0 mol/L-NaOH aqueous solution) cathode (Pt plate)

(15) After an electric current was flown at a current density of 10 A/dm.sup.2 for one hour at a liquid temperature of 25° C., the solution on the side of the anode was recovered. Concentrations of the sodium hydroxide in the recovered solution and in the initial solution were determined by a potentiometric titrator (Auto Titrator manufactured by KEM Co.) using a sulfuric acid aqueous solution, and current efficiencies were calculated in compliance with the following formula.

(16) In the case of the anion-exchange membrane, there was used a 2-compartment cell having the following constitution.

(17) Anode (Pt plate) (1.0 mol/L-sulfuric acid aqueous solution)/antion-exchange membrane/(0.25 mol/L-sulfuric

(18) acid aqueous solution) cathode (Pt plate)

(19) After an electric current was flown at a current density of 10 A/dm.sup.2 for one hour at a liquid temperature of 25° C., the solution on the side of the cathode was recovered. Concentrations of the sulfuric acid in the recovered solution and in the initial solution were determined by the potentiometric titrator (Auto Titrator manufactured by KEM Co.) using a sodium hydroxide aqueous solution, and current efficiencies were calculated in compliance with the following formula.
Current efficiency (%)=(C.sub.B−C.sub.s)/(I×t/F)×100
wherein, C.sub.B: concentration of the initial solution, C.sub.s: concentration of the solution recovered after the current has been flown, I: current value (A), t: current-flowing time (sec), F: Faraday's constant (96500 C/mol).

9. Testing after Having Repeated the Treatment with the Hot Water of 80° C.

(20) A treatment consisted of dipping the ion-exchange membrane in pure water of 80° C. for one hour and then dipping the ion-exchange membrane in pure water of 25° C. for not less than one hour. The treatment was repeated 10 times and, thereafter, the ion-exchange membrane was measured for its water permeability and current efficiency.

Example 1

(21) A mixture of the following recipe was prepared.

(22) TABLE-US-00001 Styrene (St) 39.7 parts by mass Divinylbenzene (DVB) 5.2 parts by mass Chloromethylstyrene (CMS) 40.6 parts by mass Acrylonitrile (AN) 14.5 parts by mass Acetyltributyl citrate (ATBC) 13.0 parts by mass Tert-butylperoxy-2-ethyl hexanoate (PBO) 7.3 parts by mass (Perbutyl O produced by NOF Co.)

(23) To the above mixture was added 87.0 parts by mass of unmodulated spherical low-density polyethylene particles PE1 (Flow Beads LE-1080 produced by Sumitomo Seika Chemicals Co., Ltd. particle size; 6 μm, melting point; 105° C.), and the mixture thereof was stirred for 5 hours to obtain a homogeneous polymerizable composition which possessed a viscosity of 2.2 (dPa.Math.sec).

(24) Next, there was provided the following high-density polyethylene monofilament woven fabric (PE120). High-density polyethylene monofilament woven fabric (PE120); Nip powerful network produced by NBC Meshtec Inc.) Warp: 96 mesh—filament diameter of 106 μm (62 denier) Weft: 76 mesh—filament diameter of 122 μm (71 denier) Thickness: 260 μm Opening area: 38% Melting point: 130° C.

(25) The polymerizable composition obtained above was applied onto the above high-density polyethylene monofilament woven fabric (PE120). The woven fabric was then covered on its both surfaces with a polyester film that was removable, and was polymerized at 95° C. for 5 hours.

(26) The obtained membrane-like high molecular body was sulfonated with the chlorosulfonic acid at 40° C. for 2 hours to obtain a cation-exchange membrane. Properties of the obtained cation-exchange membrane were as follows: Membrane thickness: 285 μm Ion-exchange capacity: 1.4 meq/g—dry mass Water content: 30% Membrane resistance: 12.2 Ω.Math.cm.sup.2 Water permeability: 0 ml/(m.sup.2.Math.hour) Current efficiency: 72%

(27) Next, the cation-exchange membrane was subjected to the recurring test conducted at 80° C., and was measured for its water permeability and current efficiency to be 0 ml/(m.sup.2.Math.hour) and 68%, respectively. These properties had not been almost deteriorated.

Examples 2 to 6

(28) By using the components shown in Table 1, there were prepared polymerizable compositions in the same manner as in Example 1. Table 1 also shows viscosities of the obtained polymerizable compositions.

(29) In Table 1, 40E and PHC are abbreviations of the following compounds. 40E: ethylene glycol diglycidyl ether (Epolight 40E, produced by Kyoeisha Chemical Co., Ltd.) PHC: 1,1-di-tert-butylperoxycyclohexane (Perhexa C, produced by NOF Co.)

(30) The cation-exchange membranes of the invention were then obtained in the same manner as in Example 1 but changing the polymerization temperature to 100° C. Table 2 shows the properties of the obtained cation-exchange membranes and the results of the recurring test conducted at 80° C.

Example 7

(31) There were provided the following unmodified spherical low-density polyethylene particles (PE2). Unmodified spherical low-density polyethylene particles (PE2); Flow Beads LE-2080 produced by Sumitomo Seika Chemicals Co., Ltd. Particle size: 11 μm Melting point: 105° C.

(32) By using the above unmodified spherical low-density polyethylene particles (PE2), a polymerizable composition of components shown in Table 1 was prepared.

(33) The obtained polymerizable composition possessed a viscosity of 4.2 (dPa.Math.sec).

(34) Next, as a polyolefin type monofilament base material, there was provided the following polypropylene woven fabric (PP).

(35) Polypropylene woven fabric (PP);

(36) Mesh count: 100 Filament diameter: 68 μm (30 denier) Thickness: 128 μm Opening area: 53% Melting point: 168° C.

(37) A cation-exchange membrane of the invention was obtained in the same manner as in Example 1 but using the above polypropylene woven fabric (PP). Table 2 shows the properties of the obtained cation-exchange membrane and the results of the recurring test conducted at 80° C.

Example 8

(38) There were provided the following spherical ethylene-acrylic acid copolymer particles (PE3). Spherical ethylene-acrylic acid copolymer particles (PE3); Flow Beads LE-209 Particle size: 10 μm Melting point: 101° C. Content of acrylic acid unit: 10%

(39) By using the above spherical ethylene-acrylic acid copolymer particles (PE3), a polymerizable composition of components shown in Table 1 was prepared. The polymerizable composition possessed a viscosity of 20.0 (dPa.Math.sec).

(40) Next, a cation-exchange membrane of the invention was obtained in the same manner as in Example 1. Table 2 shows the properties of the obtained cation-exchange membrane and the results of the recurring test conducted at 80° C.

Example 9

(41) A polyvinyl chloride (PVC) was added as the thickener, and a polymerizable composition shown in Table 1 was prepared. The polymerizable composition possessed a viscosity of 1.5 (dPa.Math.sec).

(42) Next, a cation-exchange membrane of the invention was obtained in the same manner as in Example 2. Table 2 shows the properties of the obtained cation-exchange membrane and the results of the recurring test conducted at 80° C.

Example 10

(43) A mixture of the following recipe was prepared. Chloromethylstyrene (CMS) 54.0 parts by mass Divinylbenzene (DVB) 4.0 parts by mass Styrene (St) 30.0 parts by mass Acrylonitrile (AN) 12.0 parts by mass Ethylene glycol diglycidyl ether (40E) (Epolight 40E, produced by Kyoeisha Chemical Co., Ltd.)
2.0 parts by mass 1,1-di-tert-butylperoxycyclohexane (PBO) (Perhexa C, produced by NOF Co.) 7.3 parts by mass

(44) To the above mixture was added 87.0 parts by mass of unmodulated spherical low-density polyethylene particles (PE1), and the mixture thereof was stirred for 5 hours to obtain a homogeneous polymerizable composition which possessed a viscosity of 2.0 (dPa.Math.sec).

(45) Next, there was provided the following high-density polyethylene monofilament woven fabric (PE200).

(46) High-density polyethylene monofilament woven fabric (PE200); Nip powerful network produced by NBC Meshtec Inc.)

(47) Warp: 156 mesh—filament diameter of 86 μm (50 denier) Weft: 100 mesh—filament diameter of 86 μm (50 denier) Thickness: 185 μm Opening area: 32% Melting point: 130° C.

(48) The composition obtained above was applied onto the above high-density polyethylene monofilament woven fabric (PE200). The woven fabric was then covered on its both surfaces with a polyester film that was removable, and was polymerized at 100° C. for 5 hours. The obtained membrane-like high molecular body was dipped in a mixture of 15 parts by mass of an aqueous solution containing 30% of trimethylamine, 52.5 parts by mass of water and 22.5 parts by mass of acetone maintaining a temperature of 30° C. for 16 hours, and there was obtained a quaternary ammonium type anion-exchange membrane.

(49) Table 2 shows the properties of the obtained anion-exchange membrane and the results of the recurring test conducted at 80° C.

Example 11

(50) The polymerizable composition of Example 1 was applied onto the high-density polyethylene monofilament woven fabric (PE200). The woven fabric was then covered on its both surfaces with a polyester film that was removable, and was polymerized at 95° C. for 5 hours. The obtained membrane-like high molecular body was sulfonated with the chlorosulfonic acid at 40° C. for 2 hours to obtain a cation-exchange membrane.

(51) Table 2 shows the properties of the obtained cation-exchange membrane and the results of the recurring test conducted at 80° C.

Example 12

(52) By using the polymerizable composition of Example 1, a cation-exchange membrane of the present invention was obtained in the same manner as in Example 7.

(53) Table 2 shows the properties of the obtained cation-exchange membrane and the results of the recurring test conducted at 80° C.

Comparative Example 1

(54) A polymerizable composition shown in Table 1 was prepared without, however, adding the nitrogen-containing aliphatic monomer, and a cation-exchange membrane was obtained in the same manner as in Example 1.

(55) Table 2 shows the properties of the obtained cation-exchange membrane and the results of the recurring test conducted at 80° C. As compared to Example 1, the water permeability and the current efficiency had been deteriorated. After the recurring test conducted at 80° C., these properties had been deteriorated further strikingly.

Comparative Examples 2 to 5

(56) Polymerizable compositions of components shown in Table 1 were prepared by using the nitrogen-containing aliphatic monomer and the polyethylene particles in amounts very different from the amounts of Example 1. The obtained polymerizable compositions possessed viscosities as shown in Table 1.

(57) By using the obtained polymerizable compositions, cation-exchange membranes were prepared in the same manner as in Example 2. In Comparative Example 5, the viscosity of the polymerizable composition was so high that a homogeneous membrane-like product could not be obtained.

(58) Table 2 shows the properties of the cation-exchange membranes obtained in Comparative Examples 2 to 5 and the results of the recurring test conducted at 80° C.

Comparative Example 6

(59) A polymerizable composition was prepared in the same manner as in Example 9 but without adding the nitrogen-containing aliphatic monomer, and a cation-exchange membrane was obtained in the same manner as in Example 9. Table 2 shows the properties of the obtained cation-exchange membrane and the results of the recurring test conducted at 80° C.

Comparative Example 7

(60) A polymerizable composition was prepared in the same manner as in Example 10 but without adding the nitrogen-containing aliphatic monomer, and an anion-exchange membrane was obtained in the same manner as in Example 10. Table 2 shows the properties of the obtained anion-exchange membrane and the results of the recurring test conducted at 80° C.

(61) TABLE-US-00002 TABLE 1 Components of polymerizable composition (parts by mass) Aromatic monomer for Crosslinking Nitrogen-containing Other introducing exchange group monomer aliphatic monomer monomer Example Kind Amount Kind Amount Kind Amount Kind Amount 1 St 39.7 DVB 5.2 AN 14.5 CMS 40.6 2 St 39.7 DVB 5.2 AN 10.5 CMS 44.6 3 St 39.7 DVB 5.2 AN 29.0 CMS 26.1 4 St 39.7 DVB 5.2 AN 14.5 CMS 40.6 5 St 39.7 DVB 5.2 AN 14.5 CMS 40.6 6 St 39.7 DVB 5.2 DMAA 14.5 CMS 40.6 7 St 39.7 DVB 5.2 AN 14.5 CMS 40.6 8 St 39.7 DVB 5.2 AN 14.5 CMS 40.6 9 St 39.7 DVB 5.2 AN 14.5 CMS 40.6 10 CMS 54.0 DVB 4.0 AN 12.0 St 30.0 Comp. Ex. 1 St 39.7 DVB 5.2 — — CMS 55.1 Comp. Ex. 2 St 39.7 DVB 5.2 AN  5.0 CMS 50.1 Comp. Ex. 3 St 39.7 DVB 5.2 AN 38.0 CMS 17.1 Comp. Ex. 4 St 39.7 DVB 5.2 AN 14.5 CMS 40.6 Comp. Ex. 5 St 39.7 DVB 5.2 AN 14.5 CMS 40.6 Comp. Ex. 6 St 39.7 DVB 5.2 — — CMS 55.1 Comp. Ex. 7 CMS 54.0 DVB 4.0 — — St 42.0 Components of polymerizable composition (parts by mass) Viscosity of Polyethylene Other blending Polymerization polymerizable powder agent initiator composition Example Kind Amount Kind Amount Kind Amount (dPa .Math. sec) 1 PE1 87.0 ATBC 13.0 PBO 7.3 2.2 2 PE1 87.0 ATBC 13.0 PHC 7.3 1.9 3 PE1 87.0 ATBC 13.0 PHC 7.3 4.3 4 PE1 70.0 ATBC 11.0 PHC 7.3 1.5 40E 2.0 5 PE1 104.0 ATBC 11.0 PHC 7.3 4.7 40E 2.0 6 PE1 87.0 ATBC 13.0 PHC 7.3 1.2 7 PE2 87.0 ATBC 13.0 PBO 7.3 4.2 8 PE3 87.0 ATBC 13.0 PBO 7.3 20.0 9 PE1 60.0 ATBC 13.0 PHC 7.3 1.5 PVC 30.0 10 PE1 87.0 40E 2.0 PHC 7.3 2.0 Comp. Ex. 1 PE1 87.0 ATBC 13.0 PBO 7.3 1.2 Comp. Ex. 2 PE1 87.0 ATBC 13.0 PHC 7.3 1.4 Comp. Ex. 3 PE1 87.0 ATBC 13.0 PHC 7.3 5.3 Comp. Ex. 4 PE1 40.0 ATBC 13.0 PHC 7.3 0.3 Comp. Ex. 5 PE1 130.0 ATBC 13.0 PHC 7.3 40.0 Comp. Ex. 6 PE3 87.0 ATBC 13.0 PHC 7.3 18.0 Comp. Ex. 7 PE1 87.0 40E 2.0 PHC 7.3 1.8

(62) TABLE-US-00003 TABLE 2 Properties of ion-exchange membrane Ion-exchange Polyolefin type Polymerization Membrane capacity filament base temperature thickness Resistance [meq/g - Example material [° C.] [μm] [Ω .Math. cm.sup.2] dry mass] 1 PE120 95 285 12.2 1.4 2 PE120 100 281 15.0 1.2 3 PE120 100 295 14.0 1.4 4 PE120 100 299 11.0 1.6 5 PE120 100 295 18.3 1.3 6 PE120 100 283 13.3 1.4 7 PP 95 163 6.8 1.4 8 PE120 95 317 8.7 1.8 9 PE120 100 279 12.8 1.4 10 PE200 100 208 12.0 1.4 11 PE200 95 214 12.0 1.5 12 PP 95 157 7.6 1.4 Comp. Ex. 1 PE120 95 276 17.0 1.1 Comp. Ex. 2 PE120 100 278 16.0 1.2 Comp. Ex. 3 PE120 100 314 9.0 1.6 Comp. Ex. 4 PE120 100 305 7.7 1.8 Comp. Ex. 5 PE120 100 membrane could not be formed Comp. Ex. 6 PE120 100 306 11.7 1.4 Comp. Ex. 7 PE200 100 215 9.7 1.5 Properties of ion- Properties after treated with exchange membrane hot water of 80° C. for 10 times Water Water Current Water Current content permeability efficiency permeability efficiency Example [%] [ml/m.sup.2 .Math. Hr] [%] [ml/m.sup.2 .Math. Hr] [%] 1 30 0 72 0 68 2 24 8 67 32 61 3 34 0 70 8 65 4 34 0 71 0 67 5 29 0 71 0 67 6 28 0 71 8 66 7 29 16 64 32 59 8 33 0 71 8 66 9 27 0 74 0 71 10 29 0 46 0 42 11 32 0 70 0 67 12 28 16 63 48 58 Comp. Ex. 1 22 80 62 250 55 Comp. Ex. 2 23 56 64 128 56 Comp. Ex. 3 34 64 63 208 55 Comp. Ex. 4 36 350 50 >1000 41 Comp. Ex. 5 membrane could not be formed Comp. Ex. 6 25 56 67 136 56 Comp. Ex. 7 32 56 43 148 37