JPH10244169A - Porous ion exchanger and production of demineralized water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably produce high purity demineralized water by bonding ion exchange resin particles of a specified particle diameter with a binder made of a thermoplastic polymer contg. a fine powdery ion exchanger of a specified particle diameter and using the resultant porous ion exchanger. SOLUTION: Ion exchange resin particles of 200-1,000μm particle diameter are bonded with a binder made of a thermoplastic polymer or a solvent-soluble polymer contg. a fine powdery ion exchanger of 0.5-150μm particle diameter to obtain the objective porous ion exchanger. The thermoplastic polymer is, e.g. low density PE, linear low density PE or ultrahigh mol.wt. high density PE. The solvent-soluble polymer is, e.g. natural rubber, butyl rubber, polyisoprene, polychloroprene, styrene-butadiene rubber, nitrile rubber or a vinyl chloride-fatty acid vinyl ester copolymer. When the porous ion exchanger is used, high purity demineralized water is stably produced over a long period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid-permeable porous ion exchanger, and more particularly to an ion exchanger for producing deionized water by electrodialysis.

[0002]

2. Description of the Related Art As a method for producing deionized water, generally, a method is used in which water to be treated is flowed through a packed bed of an ion exchange resin, and impurity ions are adsorbed and removed by the ion exchange resin to obtain deionized water. . Here, a method of regenerating an ion-exchange resin having reduced adsorption capacity using an acid or an alkali is employed. However, in this method, there is a problem that an acid or alkali waste liquid used for regeneration is discharged, and thus a method for producing deionized water that does not require regeneration of an ion exchange resin is desired.

[0003] From such a viewpoint, a self-regeneration type electrodialysis deionized water production method using an ion exchange resin and an ion exchange membrane in recent years has attracted attention. In this method, a mixture of an anion exchanger and a cation exchanger is placed in a desalting chamber of an electrodialysis apparatus in which an anion exchange membrane and a cation exchange membrane are alternately arranged, and water to be treated is placed in the desalting chamber. This is a method for producing deionized water by applying voltage while flowing and performing electrodialysis, accompanied by regeneration of the ion exchanger contained in the demineralization chamber.

[0004] Regarding this method, a method for limiting the width and thickness of the desalting chamber (Japanese Patent Application Laid-Open No. 61-107906) and a method using a uniform ion exchange resin filled in the desalting chamber (particularly, Japanese Unexamined Patent Publication (Kokai) No. 3-207487), a method of converting an ion exchange resin to be filled in a portion through which water to be treated first passes into an anion exchange resin (Japanese Patent Laid-Open No. 4-71624). A method of preparing a mixture of ion-exchange fibers (JP-A-5-277344) and the like have been studied.

[0005] However, since the crosslinked ion exchange resin is not fixed as the ion exchanger to be put into the desalting chamber, the ion exchanger of the same sign aggregates during use, or particles or fibers of the ion exchange resin are formed by the water flow. It was crushed, and efficient desalting and regeneration were not performed, and there was a problem in the stability of the purity of the obtained water.

As a method of compensating for these disadvantages, a method of introducing ion-exchange groups by performing radiation grafting on a non-woven fabric such as polyethylene or polypropylene (Japanese Patent Laid-Open No. 5-6472).
6, Japanese Unexamined Patent Publication No. 5-131120), and a sheet formed by combining an ion-exchange polymer and a reinforcing polymer into a sea-island composite fiber (Japanese Unexamined Patent Publication No. 6-79268). In these methods, although the ion exchanger is immobilized, there are drawbacks such as the necessity of using radiation, the complicated process of producing a composite fiber, and the insufficient mechanical strength.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a complicated process such as the use of radiation which is used in a method for producing deionized water by a self-regenerating electrodialysis method combining an ion exchanger and an ion exchange membrane. An object of the present invention is to produce an immobilized ion exchanger and to stably produce high-purity deionized water.

[0008]

According to the present invention, there is provided a method for producing a powder having a particle size of 200.
A porous ion exchanger in which ion-exchange resin particles having a particle size of about 1000 μm are bound using a binder, wherein the binder is a thermoplastic polymer or a solvent-soluble polymer containing ion-exchanger fine powder; Provided is a porous ion exchanger, wherein the powder has a particle size of 0.5 to 150 μm.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The binder used in the present invention is a mixture of a thermoplastic polymer or a solvent-soluble polymer and a fine powder of an ion exchanger from the viewpoint of the mechanical strength of the porous ion exchanger and the ease of molding. used.

Specifically, as the thermoplastic polymer,
Low density polyethylene, linear low density polyethylene, ultra high molecular weight high density polyethylene, polypropylene, polyisobutylene, vinyl acetate, ethylene-vinyl acetate copolymer,
Examples thereof include 1,2-polybutadiene and ethylene-propylene-diene copolymer (EPDM). Examples of the solvent-soluble polymer include natural rubber, butyl rubber, polyisoprene, polychloroprene, styrene-butadiene rubber, nitrile rubber, and vinyl chloride-fatty acid vinyl ester copolymer.

In the present invention, various fine powders of an organic ion exchanger or an inorganic ion exchanger can be used as the fine powder of the ion exchanger.

Examples of the organic ion exchanger include those obtained by introducing a sulfonic acid group as a cation exchange group into a styrene-divinylbenzene copolymer, and those obtained by introducing an amino group or a pyridinium group as an anion exchange group.

Various inorganic ion exchangers are used. For example, an aluminosilicate type inorganic ion exchanger, a hydrated oxide type inorganic ion exchanger, an acidic salt type inorganic ion exchanger, a basic salt type inorganic ion exchanger, a heteropolyacid type inorganic ion exchanger, and the like can be used. Specifically, hydrous zirconium oxide, hydrous titanium oxide, hydrous bismuth, hydrous manganese hydroxide, antimonic acid, zirconium phosphate, titanium phosphate, aluminosilicate, zeolite,
Examples include tobermorite, ammonium molybdophosphate, potassium hexacyanoiron (III) cobalt (II), potassium titanate and the like. As the ion exchanger fine powder, any of a cationic fine powder alone, an anionic fine powder alone, and a mixture thereof can be used.

The ion exchange capacity of these ion exchanger fine powders is preferably 0.5 to 5 meq / g dry resin. If the ion exchange capacity is less than 0.5 meq / g dry resin, the electrical resistance of the binder increases, and the ions adsorbed by the ion exchange resin may not be sufficiently desalted, resulting in reduced purity of deionized water. There is. On the other hand, if it is larger than 5 meq / g dry resin, the mechanical strength of the porous ion exchanger may be reduced. When the ion exchange capacity is 0.8 to 3 meq / g dry resin, a resin having high purity of deionized water can be obtained and performance stability is excellent, which is particularly preferable.

The particle size of the ion-exchanger fine powder is 0.5 to 0.5 from the viewpoint of electric resistance and strength of the mixture with the polymer.
Those having a diameter of 150 μm are used, and those having a diameter of 20 to 100 μm are particularly preferable. If the particle size exceeds 150 μm, the electrical resistance increases, the ions adsorbed by the ion-exchange resin particles are not sufficiently desalted, the purity of deionized water decreases, and the mechanical strength of the ion exchanger also decreases. Particle size is 0.
If it is less than 5 μm, the kneadability with the polymer will decrease as the surface area of the ion exchanger fine powder increases.

The content of the ion exchanger fine powder in the binder mixture is preferably from 10 to 90% by weight. If the content is less than 10% by weight, the electric resistance of the whole binder becomes high, and the ions adsorbed by the ion exchange resin may not be sufficiently desalted, so that the purity of deionized water may be reduced. If the content exceeds 90% by weight, the mechanical strength of the porous ion exchanger becomes small.

The material of the ion exchange resin particles in the present invention is not particularly limited, and various ion exchange resins can be used. Specifically, those obtained by introducing an ion exchange group into a styrene-divinylbenzene copolymer are preferred. As the ion exchange group, from the viewpoint of ion exchangeability and chemical stability, the cation exchange group is preferably a sulfonic acid type which is a strong acid, and the anion exchange group is a quaternary ammonium salt type or a pyridinium salt type which is a strong base. Is preferred.

The ion exchange capacity of the ion exchange resin particles is preferably 0.5 to 7 meq / g dry resin. When the ion exchange capacity is smaller than 0.5 meq / g dry resin, the ion exchange performance is insufficient, and when a porous ion exchanger is disposed in the desalting chamber of the electrodialysis chamber, the adsorption and desalting of ions are performed. Is not sufficiently performed, and the purity of deionized water may be reduced. If the ion exchange capacity is larger than 7 meq / g dry resin, the stability of the ion exchange resin itself may be impaired. When the ion exchange capacity is 1 to 5 meq / g dry resin, a resin having a high purity of deionized water is obtained, and the performance stability is also excellent.

The particle size of the ion exchange resin particles is 200 to 10
00 μm, and preferably 300 to 600 μm. If the particle size is less than 200 μm, the pores of the porous ion exchanger may become small and water permeability may be reduced. If the particle size exceeds 1000 μm, the surface area of the ion exchanger becomes insufficient, and the processing efficiency of ion exchange decreases. As the ion exchange resin, a resin synthesized so as to be in the range of 200 to 1000 μm, or a resin crushed so as to be in the above particle size range can be used. The shape of the ion-exchange resin particles is not particularly limited, but a spherical shape is preferable because of excellent water permeability.

As for the porosity of the porous ion exchanger, the porosity of the voids open to the outside involved in the passage of the liquid is preferably 5 to 50% by volume. If the porosity is less than 5% by volume, the flow rate of the liquid decreases and the pressure loss increases. Porosity is 50
When the content is more than% by volume, the mechanical strength of the porous ion exchanger may be reduced and handling may be difficult. Porosity of 10
When it is 40% by volume, water permeability is good, desalination performance is excellent, and high purity deionized water is obtained, which is particularly preferable. At this porosity, voids that do not actually come into contact with the liquid when the porous ion exchanger is arranged in the flow path of the liquid are not regarded as voids open to the outside.

The water permeability of the porous ion exchanger is 10 kg · cm ⁻¹ · h ^{−1 at} a pressure of 0.35 kg · cm ⁻² .
It is preferable that it is above. If the pressure is less than 10 kg · cm ⁻¹ · h ⁻¹ , the flow path resistance when the porous ion exchanger is used in the flow path becomes large, and the amount of treated water decreases or a high pressure is required for operation. Is not preferred. It is particularly preferable that the water permeability is 100 kg · cm ⁻¹ · h ⁻¹ or more. The higher the water permeability is, the more preferable. However, if a material having a large void is formed in order to produce a material having a high water permeability, the ion exchange performance and the mechanical strength may be reduced. Therefore, the substantial upper limit is 10,000 kg · cm ^{−1. -It is} about h ^-1 .

The water permeability is determined by preparing a sample of a columnar body (for example, a prism or a cylinder) having two bottom surfaces parallel to each other, and preventing water from leaking from the side surface to 0.35 kg from one bottom surface. Water is introduced at a pressure of cm ^-2 , and the amount of water flowing out from the other bottom surface is measured and determined. The area of the bottom surface is A (cm ² ), the height of the columnar body, that is, the distance between the bottom surfaces is L (cm), and the amount of permeated water per hour is W (kg ·
h ⁻¹ ), the water permeability is WL / A (kg · cm ^−1).
· H ^-1 ). A and L can be arbitrarily determined.
Is preferably about 1 to 1000 cm ² , and L is preferably about 1 to 100 cm.

As the porous ion exchanger, any of those containing only cation exchange resin particles, those containing only anion exchange resin particles, and those containing a mixture of cation exchange resin particles and anion exchange resin particles can be used. . In the case of those containing a mixture of cation exchange resin particles and anion exchange resin particles, not only those uniformly mixed, but also a part containing only cation exchange resin particles and a part containing only anion exchange resin particles What has a phase separation structure in a sea-island structure or a layered structure can also be used.

When used in the desalting chamber of the electrodialysis apparatus, it is preferable to use a mixture containing cation exchange resin particles and anion exchange resin particles. The ratio of the particles to the anion exchange resin particles is preferably cation exchange resin particles / anion exchange resin particles = 30/70 to 60/40 in total ion exchange capacity ratio. If the total ion exchange capacity ratio is out of this range, the purity of deionized water may decrease.

The porous ion exchanger of the present invention is produced by mixing a thermoplastic polymer and ion exchanger powder, then mixing the resulting mixture with ion exchange resin particles, and subjecting the mixture to heat molding. Specifically, a method of heating and kneading ion-exchange resin particles and a thermoplastic polymer containing an ion-exchanger powder into a sheet by thermoforming such as a flat plate press, etc .; And a method of extracting the pore-forming agent after heat-mixing and molding the pore-forming agent and the ion-exchange resin particles. These methods are preferably used from the viewpoint of moldability.

The porous ion exchanger of the present invention is produced by mixing a solvent-soluble polymer and an ion exchanger powder, then mixing the resulting mixture with ion-exchange resin particles, and removing the solvent. You. Specifically, there is a method in which a solution of a solvent-soluble polymer in which a pore-forming agent and an ion-exchanger powder are dispersed is applied to the surface of the ion-exchange resin particles and cured, and then the pore-forming agent is extracted.

When a pore-forming agent is used, it is preferable to add 5 to 40% by weight based on the weight of the binder. The type of pore-forming agent is not particularly limited, and any pore-forming agent can be used as long as it can be extracted with a solvent after molding of the ion exchanger. However, polymer powders such as polyvinyl alcohol and polyester are particularly preferable.

The porous ion exchanger of the present invention can be used in various apparatuses for performing ion exchange by being disposed in a liquid flow path. In particular, the porous ion exchanger is provided by alternately disposing cation exchange membranes and anion exchange membranes. It can be preferably used for a method for continuously producing deionized water by filling a deionization chamber of an electrodialysis apparatus with a porous ion exchanger.

Specifically, the following is preferred as a method for producing deionized water. That is, a plurality of cation exchange membranes and anion exchange membranes are alternately arranged between an anode chamber having an anode and a cathode chamber having a cathode, and the anode side is partitioned by an anion exchange membrane and the cathode side is positive. A desalination chamber partitioned by an ion exchange membrane, and a concentration chamber partitioned by a cation exchange membrane on the anode side and a cathode side partitioned by an anion exchange membrane alternately,
Approximately 2 to 300 sets are arranged in parallel. Desalination can be performed by flowing current while flowing water to be treated into the desalting chamber and flowing water for discharging concentrated salts into the concentration chamber.
In each unit cell, water dissociation occurs in the desalination chamber.
It is preferable to apply a voltage of about V.

When the porous ion exchanger of the present invention is disposed in the above-mentioned deionization chamber, it is possible to produce deionized water by a so-called self-regeneration type electrodialysis method. By forming the porous ion exchanger according to the size of the desalting chamber, it is possible to easily assemble a device in which the ion exchanger is filled in the desalting chamber. In the case of a normal electrodialysis device, the direction of the current flows perpendicular to the membrane surface, that is, in the thickness direction of the plate-like ion exchanger,
The water stream flows perpendicular to it.

The thickness of the porous ion exchanger is 1 to 30 mm
Is preferred. If the thickness is less than 1 mm, the water in the desalting chamber may not flow easily, and the amount of treated water may be reduced.
Above that, the electrical resistance may increase. More preferably, the thickness of the porous ion exchanger is 3 to 12 mm.

Since the ion exchange resin particles may swell when immersed in water, it is necessary to form a porous ion exchanger in consideration of the swelling ratio when incorporating the particles into an electrodialyzer or the like. Conversely, by using the swelling to bring the porous ion exchanger into close contact with the flow channel, it is possible to prevent the occurrence of unnecessary side flow. Using a material similar to the binder, the porous ion exchanger can be tightly joined in the flow channel.

The porous ion exchanger of the present invention can also be used in such a manner that current is not passed when ion exchange is performed while being placed in a flow path, and current is passed when adsorbed ions are desorbed. At the time of regeneration, a porous ion exchanger is arranged between the anode and the cathode, and a diaphragm is arranged between the porous ion exchanger and the anode and between the porous ion exchanger and the cathode to flow current. . The diaphragm need not be an ion exchange membrane,
For efficient regeneration, it is preferable to arrange an anion exchange membrane on the anode side and a cation exchange membrane on the cathode side of the porous ion exchanger.

[0034]

【Example】

[Example] Sulfonic acid type cation exchange resin (Rohm and Haas product name: Amberlite 201CT) having a particle diameter of 400 to 550 μm and an ion exchange capacity of 4.2 meq / g dry resin, and a particle diameter of 400 to 530 μm, After drying a quaternary ammonium salt type anion exchange resin having an ion exchange capacity of 3.7 meq / g dry resin (trade name: Amberlite IRA400 manufactured by Rohm and Haas Co.), 50/5
After mixing at a weight ratio of 0, the mixture was pulverized to obtain an ion exchanger powder having a particle size of 90% by weight or more and a particle size of 20 to 100 µm.

30% by weight of the above-mentioned ion exchanger powder and 70% by weight of low-density polyethylene were kneaded at 150 ° C. for 30 minutes in a kneader (Toyo Seiki Co., Ltd. product name: Labo Plast Mill).
A mixture of low-density polyethylene and ion exchanger powder was obtained (hereinafter, the mixture is referred to as pellet P).

On the other hand, a sulfonic acid type cation exchange resin having a particle diameter of 400 to 550 μm and an ion exchange capacity of 4.2 meq / g (Rohm and Haas Co., Ltd. product name: Amberlite 201CT), and a particle diameter of 400 to 530 μm After drying the quaternary ammonium salt type anion exchange resin (Rohm and Haas product name: Amberlite IRA400) having an ion exchange capacity of 3.7 meq / g dry resin, the cation exchange resin and the anion exchange resin are separated. 50/50 (volume ratio in dry state) at a ratio of 6
0/40 mixture.

The mixture was mixed with 3% by weight of pellets P and kneaded at 120 to 130 ° C. The obtained kneaded material was molded by heating at 130 ° C. by a flat plate press to obtain a sheet-like porous ion exchanger having a thickness of 8 mm.

The tensile strength of the sheet-like porous ion exchanger was 0.3 kg / cm ² , and the porosity of continuous voids was 23% by volume. When the value of the specific resistance in water of 10 μS / cm was measured in a cell, it was 300 Ω · cm at a current density of 0.005 A / cm ² .

A cation exchange membrane (Asahi Glass Co., Ltd. product name: Selemion CMT) and an anion exchange membrane (Asahi Glass Co., Ltd. product name: Selemion AMP) are alternately arranged between the anode and the cathode. A desalination chamber partitioned by a membrane and a cathode side partitioned by a cation exchange membrane, and a concentrating chamber partitioned by a cation exchange membrane on the anode side and partitioned by an anion exchange membrane on the cathode side were alternately arranged in five pairs. The effective area of the film is 500c
m ² . The above porous sheet was assembled in a desalting chamber, and a deionized water test was conducted by using water having an electric conductivity of 5 μS / cm as raw water and applying a voltage of 4 V per unit cell to obtain an electric conductivity of 0.07 μS / cm. cm of deionized water was obtained stably.

Comparative Example A sheet-like porous ion exchanger having a thickness of 8 mm was obtained in the same manner as in Example except that the pellet P was changed to low density polyethylene. The tensile strength of the sheet-like porous ion exchanger was 0.35 kg / cm ² , and the porosity of continuous voids was 23% by volume. When the value of the specific resistance in water of 10 μS / cm was measured in a cell, it was 500 Ω · cm at a current density of 0.005 A / cm ² .

[0041]

The porous ion exchanger of the present invention has high mechanical strength and excellent ion exchange performance, so that deionized water having a stable purity can be obtained. The ion exchanger obtained by this method is in the form of a sheet, so that it is easy to handle, and since it does not require a complicated process for production, a stable performance can be easily obtained.

According to the method for producing deionized water of the present invention, high-purity deionized water can be continuously produced stably for a long period of time. In addition, since a porous ion exchanger is used, the electrodialysis apparatus can be easily assembled.

Claims (5)

[Claims] 1. A porous ion exchanger in which ion exchange resin particles having a particle size of 200 to 1000 μm are bound using a binder, wherein the binder is a thermoplastic polymer containing fine powder of the ion exchanger. A porous ion exchanger, wherein the particle size of the ion exchanger fine powder is 0.5 to 150 μm. 2. A porous ion exchanger in which ion exchange resin particles having a particle size of 200 to 1000 μm are bound using a binder, wherein the binder is a solvent-soluble polymer containing fine powder of the ion exchanger. A porous ion exchanger, wherein the particle size of the ion exchanger fine powder is 0.5 to 150 μm. 3. The porous ion exchanger according to claim 1, wherein the thermoplastic polymer and the ion exchanger fine powder are mixed, the resulting mixture is mixed with the ion exchange resin particles, and the mixture is heated and molded. Method. 4. The porous ion exchanger according to claim 2, wherein the solvent-soluble polymer solution and the ion-exchanger fine powder are mixed, and then the resulting mixture and the ion-exchange resin particles are mixed, and the solvent is removed. How to manufacture. 5. A deionized water producing apparatus in which an ion exchanger is accommodated in a desalting chamber of an electrodialysis apparatus in which a cation exchange membrane and an anion exchange membrane are alternately arranged between a cathode and an anode. 3. A method for producing deionized water by supplying electricity while flowing water to be treated through a salt chamber, wherein the porous ion exchanger according to claim 1 or 2 is used as the ion exchanger.