JPH085979B2 - Method for producing cation exchanger - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improved method for producing a cation exchanger. That is, in the industrial field where a conventional cation exchanger is used, for example, use as a membrane that binds a cation exchange group such as electrodialysis, electrode reaction or diffusion dialysis, or ion exchange reaction such as an ion exchange resin. It can be used in the field as a substance to be added or as a solid acid catalyst.

[Prior art]

As the cation exchanger, various shapes such as a membrane shape, a spherical shape, a tubular shape, and a fibrous shape are used according to the purpose, and the material and manufacturing method used for the cation exchanger are different depending on the shape. today,
Ion exchange resins and ion exchange membranes are widely used as ion exchangers. Most of these have an ion-exchange group introduced into a skeleton of an ethylene-divinylbenzene copolymer. Although these ion exchange resins and ion exchange membranes are extremely excellent in performance, they have only a limited shape of ion exchanger because they have a three-dimensional crosslinked structure and require a polymerization process. There are problems such as not being able to. In order to impart new and changed characteristics to the ion exchanger and to facilitate moldability, it is necessary to make the ion exchanger based on a completely different idea.

Therefore, an aromatic condensation polymer, which has excellent chemical resistance and heat resistance and is known as engineering plastics, has been attracting attention, and research has been conducted on making an ion exchanger from this. For example, many proposals have been made in which a polysulfone or a polyethersulfone is subjected to a sulfonation treatment to introduce a sulfonic acid group, dissolved in a solvent and cast to form a film.

However, since the aromatic condensation polymer may be a polymer obtained by polycondensation, it is difficult to obtain a polymer having a high molecular weight, and the molecular weight is only about tens of thousands. Moreover,
By bringing the cation exchange group into contact with a cation exchange group-introducing reagent such as a sulfonation reagent and introducing the cation exchange group, the molecular weight of the aromatic condensation polymer is reduced. For this reason,
If a large amount of cation exchange groups is introduced, it becomes a mechanically weak cation exchanger, and further becomes a polymer soluble in a solvent. Therefore, for example, only a cation exchange membrane having an extremely small exchange capacity as shown in JP-A-60-25100 can be produced.

Therefore, a method of adopting a gentle method can be considered as a method of introducing a cation exchange group. For example, it is a method using a complex of triethyl phosphate and SO ₃ .
According to this method, the reduction of the molecular weight of the aromatic condensation polymer is small, and the sulfonic acid group can be introduced to some extent. However, even by this method, it was difficult to introduce a cation exchange group up to a commercially available cation exchange capacity, for example, 1.0 meq / g-dry membrane.

For this reason, there has been a demand for a method of introducing a sufficient amount of cation exchange groups without reducing mechanical strength.

[Means for solving problems]

In view of the above problems, the present inventors have once introduced a halomethyl group into an aromatic condensed polymer, and then converted this into a cation exchange group or a cation exchange group in the presence of a Lewis acid. When contacted with a compound having a cation exchange group, a cation exchange group or a group convertible to a cation exchange group is introduced into the aromatic condensation polymer, and at the same time, the molecular weight of the aromatic condensation polymer is increased. The present invention has been completed and the present invention has been completed. That is, according to the present invention, an aromatic condensed polymer having a haloalkyl group and not having an imide bond, an amide bond and an ester bond can be converted into a cation exchange group or a cation exchange group in the presence of a Lewis acid. After introducing the cation exchange group or a group that can be converted into the cation exchange group into the aromatic condensed polymer by contact with a compound having such a group, it can be converted into the cation exchange group as it is or after the introduction. The method is a method for producing a cation exchanger, which comprises converting such a group into a cation exchange group.

As the aromatic condensation polymer used in the present invention, known polymers having no imide bond, amide bond or ester bond can be used without any limitation. An aromatic condensed polymer having an imide bond, an amide bond and an ester bond is not preferable because it is hydrolyzed by a cation exchange group-introducing reagent described later. The aromatic condensation polymer preferably used in the present invention is generally a phenylene group, directly bonded to each other, or an oxy group, a thio group, a carbonyl group,
Aromatic condensed polymer linked via a sulfonyl group, an alkylidene group or an alkylene group is preferable. A general formula for such an aromatic condensation polymer is as follows.

Specific examples of the aromatic condensation polymer that can be preferably used in the present invention include polyphenylene, polyphenylene oxide, polysulfone, polyether sulfone,
Examples thereof include resins such as polyphenylene sulfide and polyether ether ketone, and copolymers and blends of these resins. In particular, the aromatic condensation polymer preferably used in the present invention is polysulfone, polyether sulfone and polyphenylene oxide.
The molecular weight is not particularly limited and can be adopted from a wide range of 5,000 to 100,000.

A haloalkyl group is introduced into the above aromatic condensed polymer, but the introduction of the haloalkyl group is not particularly limited, and a conventionally known means is used. Specifically, it is introduced by contacting a haloalkyl ether such as chloromethyl methyl ether, chloromethyl ethyl ether or chloromethyl propyl ether with a Lewis acid such as SnCl ₄ , TiCl ₄ , AlCl ₃ , ZnO ₂ or ZnCl ₂ . For this, a conventionally known method for introducing a haloalkyl group can be used without any limitation. That is, the aromatic condensation polymer is dissolved in a halogen-based organic solvent, and a haloalkyl ether and a Lewis acid as a catalyst are added thereto. At this time, the polymer solution is too concentrated, and when the haloalkyl ether and the catalyst are rapidly added, the gelation of the polymer may occur. Therefore, the concentration of the halogen-containing solvent of the polymer, such as carbon tetrachloride, ethylene dichloride, 1,1,2-trichlorotrifluoroethane, is preferably 40% or less. The amount of the haloalkyl ether is in the range of 1/10 to 5 times the equivalent amount when 1 equivalent of one repeating unit of the aromatic condensation polymer is used, and the catalyst amount is the equivalent to 5 times the equivalent amount of the haloalkyl ether. The following is preferable. Generally, when the temperature is raised, the reaction proceeds rapidly and the aromatic condensation polymer may gel, so it is preferable to carry out the reaction at less than 60 ° C. Generally, 1/2 to 1/1000 in the aromatic ring into which the haloalkyl ether of the aromatic condensed polymer can be introduced.
It is preferable that the haloalkyl group is introduced at a ratio of. The haloalkyl group referred to here is CH _{2 n} X (n is 1
The above integer, X is a halogen), n = 1 to 12,
Further, it is preferable that n = 1 and X is chlorine. When the haloalkyl group-containing aromatic condensation polymer obtained here is reacted with a cation exchange group-introducing reagent to introduce a cation exchange group, the haloalkyl group-containing aromatic condensation polymer is present. If so, an aromatic condensed polymer having no other haloalkyl group may be present at the same time, and particularly when the aromatic condensed polymer having a haloalkyl group contains many haloalkyl groups, Specifically, when a haloalkyl group of 1/10 or more is introduced into the aromatic ring to which the haloalkyl ether of the aromatic condensed polymer can be introduced, it is desirable that another aromatic condensed polymer coexists. In this case, if the aromatic condensation polymer to be coexisted is stable to the cation exchange group-introducing reagent, it may be of the same type or the same molecular weight as the aromatic condensation polymer in which the haloalkyl group is introduced. It is desirable that they are present, but they may be different types having good compatibility, or may be the same type but different in molecular weight.

Now, the method for introducing the cation exchanger is to bring the aromatic condensation polymer having a haloalkyl group into contact with a compound having a cation exchange group in the presence of a Lewis acid, or After contacting with a compound having a group capable of converting into a cation exchange group in the presence of a Lewis acid, the group capable of converting into the cation exchange group is converted into a cation exchange group. Here, the Lewis acid is not particularly limited as long as it acts on the aromatic condensed polymer having a haloalkyl group to increase the molecular weight of the polymer, and is used when introducing a cation exchange group or the like. It is a concept including not only the Lewis acid catalyst described above but also the compound itself having a cation exchange group exhibiting Lewis acidity.

As an example of the method for introducing a cation exchange group suitably used in the present invention, for example, in order to introduce a sulfonic acid group, 90% or more of sulfuric acid; halosulfonic acid such as chlorosulfonic acid; SO ₃ ; dioxane -SO ₃ ; A method using a sulfonic acid group-introducing reagent such as a complex of a tertiary amine such as trialkylamine or pyridine and SO ₃ is adopted. Also, a phosphate group,
In order to introduce a phosphite group, PCl ₃ , POCl ₃ , PCl _5, etc. and a Lewis acid catalyst such as AlCl ₃ , SnCl ₄ , TiCl ₄ are used, and the cation exchange group is introduced by post-treatment. The method of doing is adopted. Further, in order to introduce a carboxyl group, X—R—COR ′, X—R—CN [X is a halogen, R is a chain or branched alkylene group, a cyclic alkylene group or an aryl group, and R 'Is a halogen atom, -OR "(R" is an alkyl group having 1 to 12 carbon atoms) or -OM (M is a hydrogen ion, a metal ion or an organic amine.)], AlCl ₃ , FeCl Examples include a method in which the Friedel-Crafts reaction is carried out in the presence of a catalyst such as ₃ , SnCl _{4 and the} like, and a COOH group is introduced by post-treatment.

In the method of the present invention, by the action of a Lewis acid, a cation exchange group or a group convertible to a cation exchange group is introduced into an aromatic condensed polymer having a haloalkyl group, and at the same time, the aromatic An increase in the molecular weight of the condensation polymer occurs. The rate of increase of the molecular weight at this time is not particularly limited, but considering the strength after shaping such as film formation, the molecular weight of the polymer used as a raw material is preferably 3 to several hundred times, and more preferably 3 times. ~ It is several tens of times. In the method of the present invention, the rate of increase of the molecular weight, the introduction ratio of the haloalkyl group into the aromatic condensation polymer, the amount of the solvent used, the type and amount of the cation exchange group introduction reagent and Lewis acid catalyst used, etc. Therefore, it is preferable to control each of these conditions so that the molecular weight increase rate falls within the above range.

Now, the introduction ratio of the cation exchange group to the aromatic condensation polymer is not particularly limited, as long as it is a range that effectively acts as a cation exchanger, and also depends on the purpose of use, Usually, even if it is introduced in a range of from 0.3 to 3.0 meq / g dry resin, one having excellent mechanical strength can be obtained as long as the production method of the present invention is followed.

[Action]

The reason why the mechanical strength of the cation exchanger manufactured by the method of the present invention does not decrease is that the cation-exchange group-introducing reagent acts as a Lewis acid at the same time as the cation-exchange group-introducing agent and the haloalkyl group introduced in advance is a polymer It seems that the condensation reaction and cross-linking reaction occur in the polymer during the period. Therefore, the cation exchange group-introducing reaction causes the aromatic polycondensation polymer to react with the ion-exchanger in spite of the introduction of a high ion-exchange capacity, as the molecular-weight increasing reaction proceeds in parallel with the molecular-weight decreasing reaction by molecular cleavage. When this is done, the water content will be low and it will be a mechanically strong membrane. Specifically, it depends on the introduction ratio of the halomethyl group to the polymer, the reaction conditions of the cation-exchange group-introducing reagent, etc., and it is difficult to determine the exact molecular weight of the polymer when the cation-exchange group is introduced. The molecular weight is 3 to several tens times the molecular weight of the polymer used, and in some cases several hundred times. On the other hand, when a conventional aromatic condensation polymer is directly reacted with a sulfonation reagent, the molecular weight of the sulfonated polymer is the same as or lower than that of the raw material polymer, and a clear difference is recognized.

〔effect〕

According to the method for producing an ion exchanger of the present invention, a cation exchanger having a large ion exchange capacity, a small water content and excellent mechanical strength could be produced. This is a film,
When used as various cation exchangers such as tubular materials, spheres, fibrous materials, etc., or when used as a diaphragm for electrodialysis and electrode reaction, the electrical resistance of the membrane is reduced, and the selectivity between different-sign ions improves. When the ions were permeated by a concentration gradient, the permeation amount was increased. Furthermore, the mechanical strength has made it possible to continue the operation in an extremely stable manner in industrial equipment.

Example 1 Polyether sulfone consisting of the repeating unit represented by the formula (1) was dissolved in ethylene dichloride so as to be 10%.
After adding 50 parts by weight of ClCH ₂ OCH ₃ to 1000 parts by weight of this solution and homogenizing it, 18 parts by weight of anhydrous SnCl ₄ was added thereto.
Was added and the mixture was kept at 30 ° C. for 5 hours. Then, this was poured into a large amount of methyl alcohol to take out a rubbery polymer. After thoroughly washing with ethanol and then with water, drying under reduced pressure and elemental analysis and infrared absorption spectrum were measured, and it was found that one chloromethyl group was introduced per three units of the above repeating unit. Next, 10 parts by weight of this polymer was dissolved in 90 parts by weight of ethylene dichloride, cooled to 4 ° C., and chlorosulfonic acid having a purity of about 90% was added dropwise. After adding 3 times the amount of chlorosulfonic acid per unit equivalent number of the polymer, the mixture was allowed to stand for 3 hours, the rubbery polymer precipitated below was taken out, and put in ice-cooled water to remove excess chlorosulfonic acid.

The obtained polymer having both sulfonic acid group and chlorosulfonic acid group was dissolved in N-methylpyrrolidone to give a 30% viscous solution. This was coated on a horizontal glass plate to a thickness of 0.2 mm by a thin layer chromatography apparatus, left in the air for 10 minutes, and then put into water. After exchanging water sufficiently, peel off the film from the glass plate and immerse it in 0.5N NaOH for 5 hours to obtain 0.5N NaCl and 1N H
Properties were measured after conditioning with Cl. 0.5NN
The electrical resistance measured in aCl for 1000 cycles of alternating current is 0.5 Ω −
It was cm ² , and the amount of water permeation when a water pressure of 2 m was applied to one side of the membrane could not be measured. Electrodialysis concentration of seawater using this (Anion exchange membrane is NEOS manufactured by Tokuyama Soda Co., Ltd.)
EPTA ACS), 3A / dm ² current density, 25 ° C, 3.5
The specified concentrate was obtained with a current efficiency of 92%. The exchange capacity of this membrane was 1.20 meq / g dry membrane.

On the other hand, 10 parts by weight of the same polymer was dissolved in 90 parts by weight of ethylene dichloride as it was without chloromethylation reaction, and chlorosulfonic acid was added dropwise under cooling in the same manner, and the polymer was similarly prepared. Take out the
A film was formed from an N-methylpyrrolidone solution by a casting method. The exchange capacity of the resulting membrane was 1.18 meq / gram dry membrane. The electric resistance of the film was measured in the same way and was 0.5 Ω-c.
Although it was m ² , there was a water permeability of 5 cc / min under a water pressure of 2 m. When seawater was concentrated in the same way using this, 2.
A 6N concentrated solution was obtained with a current efficiency of 70%, but the film was mechanically very weak. When the film of the present invention was measured with a burst strength measuring device, it was 2 kg / cm ² , but the film made for comparison was 0.5 kg / cm ² or less.

Example 2 100 parts by weight of polysulfone consisting of the repeating unit of was dissolved in 1000 parts by weight of ethylene dichloride. Then, about 20 parts by weight of ClCH ₂ OCH ₃ was added thereto, and about 7.4 parts by weight of ZnO was further added to homogenize the mixture, and the mixture was reacted at 30 ° C. for 6 hours with stirring. The viscosity gradually increased during the reaction, and this was poured into a large amount of methanol to obtain a rubber-like polymer, which was separated and further thoroughly washed with methanol and water. This polymer was dried under reduced pressure, subjected to elemental analysis, and further measured by infrared absorption spectrum. As a result, one chloromethyl group was introduced in every 3.5 repeating units of the above formula.

The polymer was then dissolved in ethylene dichloride. On the other hand, when (C ₂ H ₅ ) ₃ P = 0 is dissolved in ethylene dichloride, SO ₃ is blown into it to form a complex of (C ₂ H ₅ ) ₃ P = 0 and SO ₃ , and this is dissolved in a chloromethyl group. Was dissolved in a double amount with respect to one repeating unit of the introduced polymer. The polymer solution prepared previously and the complex solution were mixed to carry out a sulfonation reaction. The mixed solution was allowed to stand for 8 hours, and the precipitated rubbery polymer was taken out. The polymer was thoroughly washed with water, washed with methanol, and washed with water to remove excess SO _3, and then dried under reduced pressure to obtain a polymer having a sulfonic acid group.

Next, this polymer was dissolved in N-methylpyrrolidone to prepare a 30% solution, which was then processed into a film having a thickness of 0.2 mm in the same manner as in Example 1. The electric resistance of this was measured and found to be 0.6 Ω-cm ² , and no water permeation was observed under a water pressure of 2 m. The concentration of the concentrated liquid obtained by conducting a seawater concentration experiment at 25 ° C using this membrane is 3.6 N,
The current efficiency was 92%. At this time, NEOSEPTA ACS manufactured by Tokuyama Soda Co., Ltd. was used as the anion exchange membrane. The obtained film had a dense layer in the surface layer and had a porous inside. The exchange capacity of the cation exchange membrane was 1.35 meq / g dry membrane. The burst strength of the membrane of the present invention was 3.5 kg / cm ² .

On the other hand, the above polysulfone was directly dissolved in ethylene dichloride without chloromethylation, and (C
H ₃ ) ₃ P = 0 and SO ₃ were subjected to sulfonation under the same conditions, and the resulting polymer was dissolved in N-methylpyrrolidone to form a film in the same manner. The exchange capacity was 1.35 meq /
Gram dry film, the electrical resistance of the membrane is 0.6 ohm-cm ^2, 2m
The water permeation rate under water pressure was 3 cc / mm, and when seawater was concentrated, a 2.7 N concentrated liquid was obtained with a current efficiency of 65%.
Further, it was significantly mechanically weaker than the membrane of the present invention and had a mechanical strength of 0.3 kg / cm ² . Incidentally, in concentrating seawater, the obtained membrane had an asymmetric structure, and was electrodialyzed and concentrated with the dense layer of the surface layer facing the seawater.

Example 3 The polymer obtained by introducing the sulfonic acid group in Example 2 was used.
It was dissolved in 40% N-methylpyrrolidone and dropped into water through a glass tube having an inner diameter of 3 mm to obtain spherical porous particles. The cation exchange capacity of this is 1.35 meq / g-
It is a dry resin and can be used for ordinary cation exchange resins,
Moreover, the specific gravity was lighter than that of sulfonated styrene-divinylbenzene copolymer.

Example 4 The chloromethyl group-introduced polyethersulfone obtained in Example 1 was dissolved in ethylene dichloride in an amount of 20 parts by weight. On the other hand, 20 parts by weight of PCl ₃ was dissolved in 100 parts by weight of ethylene dichloride, and further 5 parts by weight of anhydrous aluminum chloride was dissolved. The reaction was carried out by uniformly mixing both solutions. The reaction was carried out at 30 ° C for 5 hours. After the reaction proceeded and the precipitated polymer was taken out, it was thoroughly washed with ethylene dichloride. The obtained polymer was dried under reduced pressure to obtain a lump polymer. Elemental analysis of this and phosphorus analysis showed that one per four aromatic rings had -PC
l ₂ was introduced.

This polymer was dissolved in N-methylpyrrolidone to a concentration of 30%, and a film having a thickness of 0.2 mm was prepared in the same manner as in Example 1. The obtained film was dipped in a 1: 1 mixed solution of 1.0 N NaOH water and methanol for 5 hours to add -PCl _2- (O
H) hydrolyzed to ₂ and then in 1N nitric acid for 16 hours And The electrical resistance of this film is 1.2 measured in 0.5N NaCl.
The transport number calculated from the membrane potential measured between Ω-cm ² , 0.5 normal and 2.5 normal saline was 0.86.

On the other hand, when an attempt was made to introduce a phosphate group by the same method using the same polyether sulfone having no chloromethyl group introduced, the obtained polymer became water-soluble.
The cation exchange membrane of the present invention had a mechanical strength of 2.5 kg / cm ² .

Example 5 Polyparaphenylene oxide, Was dissolved in a solvent to a concentration of 10%, and then chloromethyl methyl ether and anhydrous tin tetrachloride were added thereto by a conventional method to carry out a chloromethylation reaction. Then, this was poured into a large amount of methyl alcohol, the precipitated rubber-like polymer was taken out, thoroughly washed with water and dried under reduced pressure to measure elemental analysis and infrared absorption spectrum, and the chloromethyl group was converted to a phenylene group. It was found that 1 in 20 was introduced. Next, this polymer was dissolved in a solvent, cast on a glass plate in the same manner as in Example 1, and after 10 minutes, immersed in water. The film stripped from the glass plate is 0.
It was a porous film having a dense structure only on the surface at 2 mm. This was immersed in a solution of 2 parts of chlorosulfonic acid and 1 part of carbon tetrachloride for 10 hours at 4 ° C. and then immersed in a 10% aqueous sodium hydroxide solution to hydrolyze the sulfonyl chloride group. It became a cation exchange membrane of a milliequivalent / gram dry membrane, and the transport number calculated from the membrane potential was 0.88 with the membrane electrical resistance of 0.3 Ω-cm ² (0.5 normal saline, 25.0 ° C.). The mechanical strength was 4.2k when the burst strength was calculated.
It was g / cm ² .

On the other hand, when the film having no chloromethyl group introduced was subjected to sulfonation treatment in the same manner and the ion exchange capacity was increased to 1.9 meq / g dry film, the film was dissolved.

Example 6 The polysulfone having a chloromethyl group introduced therein obtained in Example 2 was dissolved in ethylene dichloride to a concentration of 10%, while 100 parts of ethylene dichloride was dissolved. Was dissolved in 10 parts, and 1 part of anhydrous ZnCl ₂ was dissolved in
Both solutions were mixed. The mixture was allowed to stand at 40 ° C. for 6 hours, and it was confirmed by infrared absorption spectrum that a nitrile group was introduced into the polymer. The obtained polymer was dried for a while to take out a solid polymer, which was then dissolved in N-methylpyrrolidone to prepare a 0.2 mm film in the same manner as in Example 2. This was immersed in concentrated hydrochloric acid and boiled for 24 hours to hydrolyze the nitrile group to convert it into a carboxylic acid group. The electrical resistance of this film is 2.3Ω-cm ² in 0.5N HCl, and 0.5N NaOH and 2.5N NaOH are used.
The transport number calculated from the membrane potential generated during the period was 0.88.
The mechanical strength of this film was 4.3 kg / cm ² .

On the other hand, a polysulfone having no chloromethyl group introduced therein was subjected to the same reaction, and then similarly formed into a film and subjected to a hydrolysis treatment. As a result, the mechanical strength was 1.1 kg / cm ² .

Claims (1)

[Claims] 1. A haloalkyl group having an imide bond,
An aromatic condensed polymer having no amide bond or ester bond is brought into contact with a compound having a cation exchange group or a group capable of being converted into a cation exchange group in the presence of a Lewis acid to give the aromatic condensed system high polymer. After introducing the cation exchange group or a group convertible to the cation exchange group into the molecule, as it is, or
A method for producing a cation exchanger, which comprises converting a group capable of being converted into a cation exchange group into a cation exchange group.