JPS582971B2 - Shinkiyo Ion Kokanmaku Oyobi Sonoseizouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel ion exchange membrane in which an insoluble inorganic ion exchanger is contained in a cation exchange membrane, and a method for producing the same.

Ion-exchange membranes are used for desalination of seawater, electrodialysis such as concentration of common salt, electrolysis of various salts, etc., and their industrial applications are remarkable.

However, the permselectivity required for an ion exchange membrane,
It is not easy to have sufficient properties such as mechanical strength, chemical resistance, and low electrical resistance.

Conventional ion-exchange membranes include, for example, divinylbenzene-acrylic acid copolymer, polyethylene, divinylbenzene-styrene copolymer, polyvinylfluorocarbon ether, and other highly crosslinked polymer skeletons, on which well-known sulfones are added as cation exchange groups. Acid, carboxylic acid, phosphoric acid, phosphorous acid, phenolic hydroxyl group, sulfuric acid ester,
Polymerization type membranes and condensation type membranes containing phosphoric acid esters, thiols, etc. are known.

Furthermore, classified according to the manufacturing method, impregnated films, interpolymer films, coating methods, cutting methods, etc. are known.

These membranes each have various properties depending on their purpose, but it is not easy to satisfy all the properties that an ion exchange membrane should have.

In particular, it is not easy to improve the selective permselectivity of ions of the opposite sign, which are lacking in ion exchange membranes.

It is known that one way to increase the selective permeability of anions and cations in a cation exchange membrane is to increase the concentration of fixed anions within the membrane.

However, even if fixed ions are simply introduced, the hydrophilicity of the membrane usually increases accordingly, and it is not easy to increase the substantial fixed ion concentration within the membrane by containing a large amount of water.

In order to improve this water swelling property, efforts have been made to introduce a high degree of cross-linking into the membrane matrix polymer, but this has many problems as the mechanical strength when swollen with water is weak and the electrical resistance is high.

As a result of continuing research on increasing the fixed ion concentration within the membrane, the present inventors have found that by incorporating an insoluble inorganic ion exchanger into the cation exchange membrane, the substantial fixed anion concentration within the membrane can be increased. The present invention has been achieved by increasing the selective permeability (current efficiency) for ions of the opposite sign.

The present invention will be explained in detail below.

The first feature of the present invention is that the concentration of exchange groups is increased without highly cross-linking the cation exchange membrane.

That is, a polybasic acid salt inorganic ion exchanger having a larger exchange capacity than a normal ion exchange membrane that is substantially insoluble in water is introduced inside the cation exchange membrane, and the space of the swellable portion of the cation exchange membrane with respect to water is filled. means to fill.

Second, since the introduced substance is a hydrophilic ion exchanger with a large exchange capacity, the electrical resistance of the introduced membrane does not increase significantly compared to the original one.

Third, when introducing a polybasic acid salt inorganic ion exchanger into a cation exchange membrane, it is difficult to introduce an insoluble dry solidified exchanger, so a polybasic salt gel is created within the membrane and then dried. It is a point.

Examples of materials for the cation exchange membrane used in the present invention include the above-mentioned divinylbenzene-acrylic acid copolymer, polyethylene, divinylbenzene-styrene copolymer, polyvinylfluorocarbon ether copolymer, polyvinylidene fluoride, and vinylidene fluoride-tetrafluoroethylene copolymer. , vinylidene fluoride-tetrafluoroethylene-trifluoromonochloroethylene copolymer, and the like.

These ion exchange membranes generally have acid and alkali resistance, but there are cases where even better acid and alkali resistance is required, and such ion exchange membranes with particularly excellent chemical resistance are used. As E. I. Particularly preferred is the NAFION (perfluorosulfonic acid) membrane manufactured and sold by DuPont.

The membrane consists of a fluorinated copolymer with pendant sulfonic acid groups having cyclic structural units of the formula:

Here, R represents the unit -(OCR4R5-CR6R7)-m, R1, R2, R3, R4, R5, R6 and R7 are fluorine or a perfluoroalkyl group having 1 to 10 carbon atoms, and Y is a carbon number 1 to 10 perfluoroalkylene groups, m=O, 1, 2 or 3, n=o or 1,
p=o or 1, X is fluorine, chlorine, hydrogen or CF3
(CF2)Z, X1 is CF3(CF2)z, and 2 is O or an integer from 1 to 5.

The inorganic ion exchanger contained in the ion exchange membrane, which has a cation exchange group introduced into the skeleton of these homopolymers or copolymers, has chemical resistance, especially that it does not easily dissolve against acids and alkalis. It is preferable.

In this sense, the inorganic ion exchanger introduced is preferably an insoluble polybasic acid salt, such as phosphoric acid, molybdic acid, tungstic acid, etc., and metal salts such as titanium, thorium, cerium, tin, etc.

These salts do not necessarily have stoichiometric compositions, but their structure is thought to be that polybasic acid groups are bonded around a metal oxide polymer skeleton. There is.

The ratio of acid group to metal in the salt used in the present invention is not particularly limited.

Generally, it is difficult to introduce a polybasic acid salt into the surface or inside of a cation exchange membrane using a dry solidified polybasic acid salt, so a method is to create a polybasic acid salt gel in the exchange membrane and dry it. It will be done.

Usually, the exchange membrane is coated or impregnated with a polybasic acid selected from phosphoric acid, molybdic acid, and tungstic acid, and a salt solution of these adhesives, and then a soluble metal selected from titanium, thorium, cerium, and tin is applied. A method of contacting with a salt solution is used.

In some cases, an insoluble polybasic acid salt gel may be prepared in advance and applied to the ion exchange membrane, or the ion exchange membrane may be immersed in the gel.

However, a method in which a gel is generated on or inside the cation exchange membrane is preferable because the gel is contained uniformly.

The insoluble polybasic acid salt gel thus introduced into the ion exchange membrane is dried.

Normally, the higher the drying temperature, the more stable the salt is against chemicals and mechanical strength, but the exchange capacity as an ion exchanger tends to decrease.

Therefore, the appropriate drying temperature is usually about 30°C to 200°C.

The amount of the polybasic acid salt inorganic ion exchanger introduced into the cation exchange membrane is usually 0.01 to 20 parts by weight, preferably 0.01 to 20 parts by weight, per 100 parts by weight of the cation exchange membrane, in metal units.
1 to 5 parts by weight are used.

If it is less than 0.01 parts by weight, it is impossible to increase the exchange capacity, which is the purpose of introduction.

Moreover, if the amount is 20 parts by weight or more, depending on the type of ion exchange membrane used, not only will the membrane have weak mechanical strength, but also the electrical resistance will increase, making it unsuitable for practical use.

The cation exchange membrane of the present invention, in which a polybasic acid salt inorganic ion exchanger is introduced into the interior or surface of the cation exchange membrane by the above method, has a lower cation exchange membrane than the cation exchange membrane before introduction of the exchanger.
It is an extremely useful membrane that not only has a reduced water content, but also an increased exchange capacity per gram of water contained, that is, the concentration of fixed ions within the membrane, and does not have a particularly large increase in electrical resistance.

Hereinafter, the present invention will be explained by examples.

Example I A NAFION 315 membrane manufactured by DuPont was immersed in a 24% titanium sulfate aqueous solution and boiled for 10 minutes.The membrane was then placed in 85% phosphoric acid at 120°C and kept for 30 minutes. After washing with water, it was dried at 110°C for 6 hours.

The amount of titanium phosphate introduced was approximately 2% by weight as a result of weighing.

0.5 as titanium per 100 parts by weight of ion exchange membrane
This corresponds to 6 parts by weight.

Salt electrolysis was performed using this membrane.

The results are shown in Table 1. As a comparative example, when a NAFION 315 membrane without titanium phosphate treatment was energized under the same electrolytic conditions, the current efficiency at 6N NaOH was 8.
It was 4%.

It can be seen that the titanium phosphate treated film maintains high current efficiency.

Example 2 E. I, DuPont cation exchange membrane NAFION11
0 as ceric sulfate Ce(SO4)2.4H2010
g was immersed in an aqueous solution of 100 cc of deionized water and boiled for 30 minutes.

NAFION 110 containing this ceric sulfate was immersed in a 30% sodium molybdate aqueous solution at 100° C. for 30 minutes to introduce cerium molybdate.

It can be seen that white cerium molybutate is deposited within the film.

This membrane was washed with water and then dried at 110°C for 2 hours.

The amount of cerium molybutate introduced was 1.8% as a result of weighing.

This corresponds to 0.56 parts by weight of cerium per 100 parts by weight of the ion exchange membrane.

In addition, the fixed ion concentration (CR) in the membrane is 2.9 meq/gH.
20 and NA without cerium molybdate treatment
It was increased by about 13% compared to the FION110 untreated membrane.

Note that the water content at the time of CR measurement was the value after hot water treatment at 100° C. for 1 hour.

Example 3 Smooth glass plates and Teflon mesh as a reinforcing agent were alternately placed in a sandwich shape in a styrene polymerization container.
65 parts by weight of styrene, 35 parts by weight of divinylbenzene, and a mixture of 1 to 113 monomers of 1 part by weight of penzoyl peroxide as a polymerization initiator were placed between glass plates, and after the atmosphere was replaced with nitrogen, polymerization was carried out at 60° C. for 16 hours.

The temperature was further raised to 80°C and maintained for 3 hours, and then the taken out styrene-divinylbenzene membrane was immersed in ethylene dichloride at room temperature for 3 hours, allowed to swell, and then immersed in 98% concentrated sulfuric acid at 40°C for 60 hours. Then, sulfonation was performed to obtain a cation exchange membrane.

The fixed ion concentration (CR) of this membrane at 60°C is 3. It was 2 meq/gH20.

This membrane was placed in a 30% sodium molybutate aqueous solution for 30 minutes.
After boiling for a minute, it was immersed for 30 minutes in an aqueous solution of stannic chloride (SnCl4.5H20) saturated with IN hydrochloric acid at 100°C, and tin molybdate was introduced.

As a result of weighing, the introduced tin molybdate was approximately 0.9%.
Met.

This is 0 parts per 100 parts by weight of the ion exchange membrane as tin.
．． It can be seen that tin molybdate corresponding to 14 parts by weight was deposited in the film in a pale yellow color.

The fixed ion concentration within the membrane at 60°C is 3.6
It is understood that meq/gH20 has increased compared to before the introduction of tin molybdate.

Claims (1)

[Claims] 1. A polybasic acid salt inorganic ion exchanger consisting of phosphoric acid, molybdic acid, or tungstic acid of a metal selected from titanium, thorium, cerium, and tin is provided on the surface or inside of the cation exchange membrane. , for 100 parts by weight of the cation exchange membrane,
An ion exchange membrane containing 0.01 to 20 parts by weight of metal units. 2. In manufacturing the above ion exchange membrane, the cation exchange membrane is coated or impregnated with a polybasic acid selected from phosphoric acid, molybdic acid, and tungstic acid, and a soluble salt solution thereof, and then titanium, thorium, cerium, and tin are added. An ion exchange membrane characterized in that it is brought into contact with a solution of a soluble metal salt selected from the above, or, conversely, it is first applied or impregnated with the metal salt solution and then brought into contact with a solution of the polybasic acid and a soluble salt thereof. manufacturing method.