JPH02245035A - Cation exchanger - Google Patents

Abstract

PURPOSE:To obtain a cation exchanger excellent in mechanical properties, moldability and ion exchanging characteristics comprising a sulfonated polymer of a polysulfone polymer having haloalkyl groups. CONSTITUTION:A cation exchanger prepared from a sulfonated polymer of a polysulfone polymer having at least one haloalkyl group in the molecule or its cured product and having an ion exchange capacity of 0.5-3.5 milliequivalents/g dry resin. As the haloalkyl group, a chloromethyl group (-CH2Cl) is particularly desirable. As the polysulfone polymer, an aromatic polysulfone block copolymer of formula I is desirable. In formula I, Ar is formula II or III; Y is a single bond, -O or formula IV; Z is -O-, -S- or -SO2-; R1-R9 are the same or different from each other and are each a 1-8C hydrocarbon group; a-d are each 0-4; e is 0-3; (f+g) is 0-7; (h+i) is 0-5; R10 and R11 are each a hydrogen atom or a 1-6C hydrocarbon group; and m/n=100/1-1/10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ion exchanger that adsorbs or permeates and separates specific components from a mixed fluid.

More specifically, we will introduce cation exchange thin membranes with low resistance useful for electrodialysis such as seawater concentration and battery separators, hollow fiber cation exchange membranes useful for dialysis, and porous cation exchange membranes with high permeability for polymer cations. It relates to cation exchangers with excellent processability, such as membranes.

[Prior Art] Many documents and patents have been reported as cation exchangers, but styrene is the most practical and useful one.
There are sulfonated cation exchangers of divinylbenzene copolymers. In addition to their chemical resistance and heat resistance, by changing the content of divinylbenzene, a crosslinking agent,
Since ion exchange properties and permselectivity can be controlled, a wide variety of products have been synthesized and developed for various uses.

However, the conventional styrene-divinylbenzene system cannot meet the needs of ultra-low resistance cation exchange membranes for new applications, such as seawater concentration to produce salt as inexpensive as industrial salt, and separators for redox flow batteries and methanol batteries. There is. In other words, to lower the resistance,
It is necessary to reduce the film thickness, but styrene-divinylbenzene resin has mechanical strength, especially brittleness, so
An ion exchange membrane with a diameter of 00 μm or less cannot be obtained. Furthermore, in addition to mechanical properties, styrene-divinylbenpene resins have
Processability is poor, and processed membranes such as hollow fiber type and porous cation exchange membranes cannot be obtained.

On the other hand, polysulfone membranes with excellent mechanical strength and processability are used in ultrafiltration membranes and reverse osmosis membranes, and sulfonated polysulfone membranes are being considered to improve their permeability.

For example, sulfonated polysulfones consisting of repeating units are USP 37
09841, and JP-A-509997.
3, JP-A-51-1.46379. JP-A-61-450
No. 5, etc., describes a semipermeable membrane in which such a sulfonated polysulfone is laminated on an anisotropic ultrafiltration membrane.

However, these sulfonated polysulfone membranes
Since it is non-crosslinked, the ion exchange capacity is 2.0 meq/
If the resin is more than g, it becomes water soluble, and even if the ion exchange capacity is low, the water absorption rate is high, so the ion selective permeability is low, and it cannot be used as a substitute for the conventional styrene-divinylbenzene-based cation exchange membrane.

[Problems to be Solved by the Invention] The present invention aims to solve the above-mentioned drawbacks of the prior art, and provides a novel cation exchanger with excellent processability and high ion permselectivity. The purpose is to provide

The purpose of the present invention is to provide a cation exchange membrane that can be used in energy-saving electrodialysis methods, battery separators, compact and easy-to-maintain porrow fiber dialysis modules, etc., which cannot be achieved with conventional technology. .

[Means for Solving the Problems] The above object of the present invention is to provide a sulfonated polymer of a polysulfone type polymer containing at least one haloalkyl group in one molecule or a cured product thereof, which has an ion exchange capacity. This is achieved by an ion exchanger characterized in that the amount is 0.5 to 3.5 milliequivalents/g resin.

The cation exchanger of the present invention basically consists of a sulfonated polymer of the above-mentioned specific polysulfone polymer or a cured product thereof, but this has significantly superior properties compared to conventional cation exchangers. It is possible to provide a cation exchanger having:

That is, as described in JP-A-61-4505, conventional sulfonated polysulfone polymers become water-soluble polymers due to non-crosslinking when their ion exchange capacity exceeds 2.0 meq/g resin. Therefore, it cannot be used as an ion exchanger.

Furthermore, as polysulfone resins having crosslinking sites, those containing -OH groups or -CmiCH groups at the terminals are known, but these crosslinking sites have low reactivity,
It requires high-temperature heat treatment at 320 to 400°C, which exceeds the thermal decomposition temperature of sulfonic acid groups, and is not suitable as a material for producing crosslinked polysulfone-based ion exchange membranes.

The present inventor conducted intensive research on cured products of sulfonated polysulfone polymers, and found that by using polysulfone polymers containing haloalkyl groups in the molecule, the cured products had excellent mechanical properties, moldability, and ion exchange properties. The inventors discovered that a cation exchanger can be produced and completed the present invention.

The present invention will be described in detail below. As the cation exchanger of the present invention, any polysulfone polymer containing at least one haloalkyl group in one molecule can be used without any restrictions.

The polysulfone polymer containing a haloalkyl group has a general formula of a different single bond, -o-, -s-, -so□=IO or a different hydrocarbon group having 1 to 8 carbon atoms, a - d is O
~4, e is 0-3, (f+g) is 0-7, (h+i,)
is 0 to 5, R3°, R represents hydrogen or a hydrocarbon group having 1 to 6 carbon atoms, and m/n = lOO10 to 1/100. ) is obtained by haloalkylation of a polymer containing an aromatic polysulfone. As a haloalkyl group -
(CH□). CL, -((:R2),,Br.

(CH,)nF, and -((:R2), I are exemplified, but -CH2Cl-CHJr is preferred from the viewpoint of reactivity, and -GHzC1 is particularly preferably adopted from the viewpoint of mass productivity. As a method for introducing such a chloromethyl group, is a nucleophilic chloromethylating agent such as chloromethyl methyl ether, 1,4-bis(chloromethoxy)butane, 1-chloromethotoxy-4-chlorobutane and formalin hydrogen chloride, paraformaldehyde, hydrogen chloride in the presence of a catalyst. It can be obtained by contacting with a polysulfone polymer.Such polysulfone polymers include polysulfone polymers such as <)so, @o@o+ (c), and polysulfone units different from the above polysulfone units. Unit, for example (Oki2oOya
A block copolymer with (d) ()o2@S) (e) ()0□0SO□arrow (f) +2@Oも (g) s)0arrow (h) is exemplified.

According to the present invention, a cation exchanger with unprecedented high performance can be obtained by using the polysulfone (a) which is easily available as a general-purpose polysulfone, but it is preferable that the ion exchange capacity can be easily controlled. A polysulfone block copolymer is used from the viewpoint of the mechanical properties of the resulting sulfonated polymer.

In the present invention, it is not necessarily clear why the block copolymer is superior in terms of mechanical properties, but it is explained as follows.

In the present invention, the presence of the chloromethyl group is necessary for crosslinking the polymer, thereby lowering the water absorption rate of the ion exchanger and increasing the permselectivity. However, crosslinking suppresses the swelling properties of the polymer due to molecular movement and water absorption, resulting in large internal strains in the polymer. When polysulfone-based homopolymers are used, such effects act on the entire molecule, making them hard and brittle. (However, in the block copolymer, the ion exchange group and the crosslinked zyte are 1CH,C1
It is explained that since no group is present or a very small number of units are present, the excellent mechanical properties inherent to the polysulfone polymer are not impaired.

Such preferable polysulfone polymers include hydrocarbon groups having 1 to 8 carbon atoms having the same or different general formulas, a
~d is O~4, e is 0~3, (f+g) is O~7, (h
+i) represents 0 to 5, R3°R11 represents hydrogen, a hydrocarbon group having 1 to 6 carbon atoms, and m/n = 1.00/1 to 1/10. ) is exemplified, and in particular, an aromatic polysulfone/boridioether copolymer in which Z in the general formula is represented by -3- can yield a high molecular weight copolymer, and the copolymer composition can be The aromatic polysulfone/polythioethersulfone copolymer is preferably used from the viewpoints of ease of control (and moldability, mechanical strength, and chemical resistance).
2020. JP-A-61-76523 and JP-A-61-
168629.

As a method for introducing -CH, one group into the polysulfone-based polymer mentioned above, a method of bringing the chloromethylating agent mentioned above into contact with a granular polymer or a film-like molded product can also be used, but the uniformity of the reaction and the formation In order to obtain a polymer with good processability, it is preferable to dissolve it in a solvent that is stable to a chloromethylating agent and dissolves a polysulfone polymer, and to react in a liquid state. As such solvents, halogenated hydrocarbons such as trichloroethane, tetrachloroethane, etc. are used. By adding a chloromethylating agent and a catalyst such as tin chloride to the polysulfone polymer solution and appropriately selecting the reaction site and reaction time, a chloromethylated polysulfone polymer having a desired chloromethyl group content can be obtained. can get.

The chloromethyl group content varies depending on the desired ion exchange capacity by the next sulfonation treatment, but is 0.01
It is preferred that a chloromethylated polysulfone polymer of ~3.5 meq/g resin is used and contains chloromethyl groups corresponding to 1 to 100% equivalents, especially 5 to 50% equivalents of the ion exchange capacity.

The thus obtained chloromethylated polysulfone polymer was prepared using a single solvent of trichloroethane, tetrachloroethane, dimethylacetamide, dimethylformide, dimethyl sulfoxide, triethyl phosphate, and N-methylpyrrolidone, as well as a water-acetone mixture, methanol-tetra After dissolving in a hydrafuran mixture or the like, it is cast and dried into a desired shape and molded, but it is preferable to contact it with an acid before or after the molding.

The above acids include A1. C1-, 5bC1s, FeC
:lx, Te(:12゜5nC14, TiC1<, Te
Lewis acids such as C1<, B1C15, ZnC1+ and H
Examples include protic acids such as F, H, SO4, P2O, H, PO4, etc., and at least one of the acids mentioned above is made to coexist with a solution of the chloromethylated polysulfone polymer, and then cast and dried, or the chloromethylated polysulfone polymer is The molded product can be brought into contact with the above acid.

After such a polymer solution is cast into a convenient shape, the solvent is removed to obtain a molded article such as a flat membrane, a hollow fiber, or a composite membrane with a porous substrate.

Also, when the solvent is removed by heat treatment,
On the other hand, a molded article with a dense structure can be made porous by immersing it in a solution that extracts the solvent, particularly preferably a solution using a non-solvent or a poor solvent for the polymer, while the solvent remains. It is possible to produce structural molded products.

The thus obtained molded product is heated at 25 to 300°C, preferably 50 to 200°C, and when an acid is present, a crosslinked molded product can be obtained.

If no acid is coexisting, the product is contacted with the above-mentioned acid to obtain a crosslinked molded product before introducing the sulfonic group using a known sulfonating agent, but as another preferred method, concentrated sulfuric acid may be used as the acid. By using this, sulfonation and crosslinking reactions can occur simultaneously, and a crosslinked cation exchanger can be obtained.

As the sulfonating agent, concentrated sulfuric acid, fuming sulfuric acid, chlorosulfonic acid, sulfuric anhydride, sulfuric anhydride triethyl phosphate complex, etc. can be used without limitation.

Thus, by contacting the polysulfone molded article of the present invention with a sulfonating agent and appropriately selecting the reaction temperature and reaction time, a sulfonated polysulfone polymer having a desired ion exchange capacity can be obtained. However, if the ion exchange capacity is less than 0.5 meq/g resin, the membrane resistance is extremely high, and if it is more than 3.5 meq/g resin, a large amount of chloromethyl groups, which are crosslinking sites, are required, and as a result, Since this leads to a decrease in the ion exchange capacity of the cured membrane and also decreases the mechanical strength, especially the toughness, of the resulting membrane, the ion exchange capacity is preferably 0.5 to 3.5 milliequivalents/g resin, 0.8 to 3.5 milliequivalents/g resin. React to give 3.0 milliequivalents/g resin.

The cation exchanger thus obtained can be used as a separation membrane such as a diaphragm for electrodialysis, a diaphragm for battery Separake-1 diffusion dialysis, etc. after being replaced with a convenient solution such as a saline solution. EXAMPLES Next, the present invention will be explained with reference to examples, but the present invention is not limited to these examples.

[Example] Example 1 JP-A-61. -168629, 4,4'-diphenol and dihalodiphenylsulfone are reacted to synthesize a precursor consisting of an aromatic polysulfone unit, and then the precursor and dihalodiphenylsulfone are reacted. Sulfone and sodium sulfide were reacted to obtain an aromatic polysulfone-polythioethersulfone copolymer A represented by the following formula.

m/n=1/1 Intrinsic viscosity 0.65 Next, the copolymer A has 1,1,2,2. After dissolving in tetrachloroethane, chloromethyl methyl ether and anhydrous tin chloride were added and reacted at 110°C for 4 hours, followed by precipitation and washing with methyl alcohol to obtain chloromethylated copolymer B.
I got it. The amount of active chlorine in chloromethylated copolymer B is 0.
, 5 meq/g resin.

Copolymer B thus obtained was dissolved in tetrachloroethane to obtain a 10% by weight solution. Next, the polymer solution was cast onto a glass plate, and then heated and dried at 150° C. for 2 hours to obtain a cast film with a thickness of 25 μm.

Next, the cast film of copolymer B was sulfonated with 98 wt % concentrated sulfuric acid at 90° C. for 6 hours. The cation exchange membrane thus obtained had an ion exchange capacity of 1.5 milliequivalents/g resin, and after being immersed in a 0.5 N-NaCl solution, the transport number of Na ions was determined by AC resistance and membrane potential methods. When I calculated it, I found that the AC resistance (0.5N-NaC11000
Hz)=0.3 Ω·can2Na'' transference number (from 0.5M Na11/LM Na11 membrane potential): 0.90.

Comparative Example 1 A cast film of copolymer A was obtained in exactly the same manner as in Example 1 except that copolymer A before the chloromethylation reaction was used. Next, when the cast membrane was sulfonated with 98% by weight concentrated sulfuric acid, it dissolved and a cation exchange membrane could not be obtained.

Example 2 Copolymer A was chloromethylated in the same manner as in Example 1, but the reaction temperature and reaction time were changed to obtain copolymers C, D, E, and F with different chloromethyl group contents. .

The four copolymers obtained in the above manner were dissolved in tetrachloroethane, cast on a glass plate, and dried by heating at 110° C. for 4 hours to obtain a cast film with a thickness of 25 μm.

Next, the cast film was soaked in 96% concentrated sulfuric acid at 90°C.
It was soaked for 6 hours to effect sulfonation. The ion exchange capacity, resistance, and transfer number of Na" ions of the obtained cation exchange membrane were measured in the same manner as in Example 1. The results are shown in Table 1.

Example 3 Bisphenol A and dihalodiphenylsulfone were reacted to obtain aromatic polysulfone polymer G.

Table 1 Intrinsic viscosity 0.56 The thus obtained polymer G was chloromethylated in the same manner as in Example 1, but the reaction temperature and reaction time were changed to produce polymers H, I, and J with different chloromethyl group contents. I got it.

The three types of polymers obtained were formed into membranes in the same manner as in Example 2, and then sulfonated. The results of the obtained cation exchange membranes are shown in Table 1.

Comparative Example 2 A cast film of Polymer G was obtained in exactly the same manner as in Example 3, except that Polymer G before the chloromethylation reaction was used. When the cast membrane was then sulfonated in 96% by weight concentrated sulfuric acid, it dissolved and a cation exchange membrane could not be obtained.

[Effects of the Invention] The cation exchanger of the present invention is characterized by being composed of sulfonated polysulfone that can be crosslinked. Therefore, by controlling the type of curing agent, the amount of curing agent, and the curing conditions, it is possible to control the fixed ion concentration. Improved resistance to solvents.

In particular, when an aromatic polysulfone and polythioethersulfone copolymer is used, a cation exchange membrane with good moldability and mechanical strength can be obtained. In addition, during sulfonation, sulfonic acid groups are introduced into specific sites due to differences in reactivity, resulting in hydrophilic segments with ion exchange groups introduced,
A block copolymer consisting of hydrophobic segments without ion exchange groups introduced therein can be obtained, and even if the ion exchange capacity is high, a strong membrane with high mechanical strength can be obtained.

Furthermore, since it can be cast from a solution containing a sulfonated copolymer and a curing agent, a thin ion exchange membrane can be obtained, and it can also be coated and dried on porous substrates or other polymer membranes. This method has the feature that a multilayer ion exchange membrane can be easily obtained.

Claims (4)

[Claims] (1) Consists of a sulfonated polysulfone polymer having at least one haloalkyl group in one molecule or a cured product thereof, and has an ion exchange capacity of 0.5 to 3.5
A cation exchanger of a polysulfone polymer, characterized in that it is milliequivalent/g dry resin. (2) Polysulfone polymers have a general formula ▲ mathematical formula, chemical formula, table, etc. ▼ (However, Ar in the formula ▲ has a mathematical formula, chemical formula, table, etc. ▼
, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, Y is a single bond, -
O- or ▲There are mathematical formulas, chemical formulas, tables, etc.▼. Z is -O-, -S
- or -SO_2-, R^1 to R^9 are the same or different hydrocarbon groups having 1 to 8 carbon atoms, a to d are 0 to 4, e is 0 to 3, (f+g) is 0 to 7, (h+i) is 0 to 5, R_1_0 and R_1_1 are hydrogen or a hydrocarbon group having 1 to 6 carbon atoms, m/n=100/1 to 1/10. )
The cation exchanger according to claim (1), which is an aromatic polysulfone block copolymer represented by: (3) The cation exchanger is a sulfonated cation exchange membrane having a thickness of 100 μm or less that is cast from a solution containing a haloalkylated polysulfone polymer and heat treated. Claims (1)
Or the cation exchanger of (2). (4) Haloalkyl group is chloromethyl group (-CH_2C
Claims (1) to (l) characterized in that:
3) any of the cation exchangers.