JPH06343880A - High polymer cation exchanger and its production - Google Patents

Abstract

PURPOSE:To obtain a heat resistant high polymer cation exchanger which has high ion exchange capacity and excellent in thin film forming property by providing the exchanger with a structural unit expressed by a specified formula and a specified cation exchange group to its arom. ring. CONSTITUTION:The high polymer cation exchanger is composed of the polymer compd. containing an arom. polymer having a structural unit expressed by formula I (In the formula, X is CH2, O, S, SO2 and CO, n is integer of 2-500.), and has a cation exchange group having the decomposition ability of a neutral salt in the arom. ring and the ion exchange capacity of 0.5-4 milli equivalent/g dry resin. As the cation exchange group, -SO3H, phosphate and -CF3COOH group is exemplyfied. Because the high polymer cation exchanger is good in solubility to an org. solvent, a thin film formation is possible by a casting method, and the film of low resistance is obtained to be appropriately used as the separator of the separating membrane of a fuel cell and an electrolytic diaphragm, etc.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polymeric cation exchanger having a novel structure and a method for producing the same. More specifically, the present invention relates to a low resistance polymer cation exchanger having excellent heat resistance and thin film formability, which is useful for fuel cell membranes and electrolytic membranes, and a method for producing the same.

[0002]

Conventionally, as a cation exchange membrane, a cation exchange membrane obtained by sulfonating a styrene-divinylbenzene copolymer has been generally used for electrodialysis and the like, but it is used in an oxidizing atmosphere at a high temperature. When used as a fuel cell membrane or an electrolytic membrane, the heat resistance and chemical resistance are inferior, so that there is a drawback that cannot be dealt with. On the other hand, for these applications, a fluororesin-based perfluorocarbon sulfonic acid having excellent heat resistance and chemical resistance based on a copolymer of tetrafluoroethylene and a perfluorovinyl ether having a functional group (DuPont Nafion Membrane, etc.) is used. However, these also have drawbacks such as high membrane resistance and extremely high price due to their small ion exchange capacity, difficulty in thinning, and large thickness.

[0003]

SUMMARY OF THE INVENTION The present invention solves the above problems and has excellent heat resistance, high ion exchange capacity, and excellent thin-film formability, such as fuel cell membranes and electrolytic membranes. The purpose of the present invention is to provide a high molecular weight cation exchanger, which can be used as a useful cation exchange membrane, at low cost.

[0004]

The present invention is a high molecular weight cation exchanger having a novel structure, which has been earnestly studied in order to solve the above-mentioned drawbacks of the prior art. General formula (I)

[0005]

[Chemical 3]

(In the formula, X is --CH _2- , --O--, --S
-, - SO ₂ -, - represents a CO-, n is an integer of 2 to 500. ) Consisting of a polymer compound containing an aromatic polymer having a structural unit represented by the formula (1) and having a cation exchange group capable of decomposing a neutral salt in its aromatic ring, and having an ion exchange capacity of 0.5 to 4 mm. The present invention provides a high molecular weight cation exchanger characterized by being an equivalent weight / g dry resin.
Furthermore, the present invention provides the following general formula (II)

[0007]

[Chemical 4]

(In the formula, X is --CH _2- , --O--, --S
-, - SO ₂ -, - represents a CO-, n is an integer of 2 to 500. The present invention provides a method for producing the above-mentioned polymer cation exchanger, which comprises sulfonation of an aromatic ring of the aromatic linear polymer compound represented by (4) and then performing a dehydration cyclization reaction.

The present invention will be described in more detail below. The polymer cation exchanger of the present invention is a cation exchanger comprising an aromatic polymer having a structural unit represented by the general formula (I) and a cation exchange group having a neutral salt decomposing ability. Is. Examples of the cation exchange group having a neutral salt decomposing ability include —SO ₃ H group, phosphoric acid group, and —CF ₃ COOH group, which have ion exchange characteristics in a wide range of pH, and
Considering the convenience of introducing an ion-exchange group, -SO
_{The 3} H group is particularly preferred.

(Manufacturing Method) As a method for manufacturing the polymer cation exchanger of the present invention, there is, for example, the following method. That is, first, an aromatic linear polymer compound represented by the following general formula (II) is reacted with an excess amount of a sulfonation reagent to be sulfonated to give a compound of the general formula (III), and then a dehydration ring (IV) which is a functional component of the polymer cation exchanger of the present invention can be produced by a chemical reaction.

[0011]

[Chemical 5]

(In the formula, X is --CH _2- , --O--, --S
-, - SO ₂ -, - represents a CO-, n is an integer of 2 to 500. ) Specific examples of the polymer compound represented by the general formula (II) include poly [diphenylmethane-4,4′-diyl (parabanic acid)] (Poly [diphenylmethane-4,4′-diyl (parabanic
cid)]), poly [diphenylether-4,4'-diyl (parabanic acid)] (Poly [diphenylether-4,4'-diyl (paraban
ic acid)]), Poly [diphenylsulfide-4,4'-diyl (parabanic acid)] (Poly [diphenylsulfide-4,4'-diy
l (parabanic acid)]), poly [diphenyl sulfone-4,
4'-diyl (parabanic acid)] (Poly [diphenylsulfone-4,
4'-diyl (parabanic acid)]) Poly [diphenylketone-4,4'-diyl (parabanic acid)]
(Poly [diphenylketone-4,4'-diyl (parabanic acid)]
) And the like.

As a method for introducing a sulfone group into the above-mentioned aromatic linear polymer compound (II), a generally known sulfonation reagent such as fuming sulfuric acid, sulfuric acid anhydride, concentrated sulfuric acid or chlorosulfonic acid is used. The aromatic ring can be sulfonated. At this time, the substitution position of the sulfonic acid group in the benzene nucleus may be either the ortho position or the meta position when the α position is ortho and the β position is meta with reference to the N-position bonding position of the parabanic acid skeleton. It is considered that the sulfonic acid group introduced at the ortho position remains as an ion-exchange group without undergoing a cyclization reaction, and the sulfonic acid group introduced at the meta position immediately contributes to dehydration and cyclization reaction.

As the reaction solvent, a solvent capable of dissolving the above-mentioned polymer compound (II) can be used. As such a solvent, for example, the above-mentioned sulfonation reagents can be used alone or in combination, but an organic solvent such as sulfolane or dimethylsulfolane which is stable against a strong acid can also be used. Among these, fuming sulfuric acid or a mixed solvent with fuming sulfuric acid is particularly preferably used for the purpose of obtaining a polymer cation exchanger having an excellent ion exchange capacity.

As the reaction procedure, the polymer compound represented by the general formula (II) and the sulfonation reagent are simultaneously mixed and charged, but the polymer compound represented by the general formula (II) is added to the sulfonation reagent. It may be a method. Further, the sulfonation reaction and the dehydration cyclization reaction may be continuously carried out in the same reactor, or the polymer compound represented by the general formula (II) and the sulfonation reagent may be previously reacted. General formula (II
A method in which a polymer sulfonate having a repeating unit represented by I) is produced, and this is isolated and then subjected to a dehydration cyclization reaction may be used.

The dehydration cyclization reaction after sulfonation is easily caused by the sulfonic acid group introduced at the meta position of the benzene nucleus with respect to the parabanic acid skeleton in the structural unit represented by the general formula (II). Was confirmed by ¹³ C-nuclear magnetic resonance spectrum analysis of the present polymer compound (I). In the two-step reaction, the polymer containing the aromatic polymer (I) of the present invention is continuously produced in the same reactor without once isolating the polymer compound (III). The compound can be prepared.

The reaction molar ratio of the polymer compound represented by the general formula (II) and the sulfonating reagent is 1.1 mol or more, preferably 2 mol or more, of the sulfonating agent to 1 mol of the polymer compound. Used in proportion. When the amount of the sulfonating agent is less than 1 mol, the introduced sulfonic acid group disappears by the dehydration cyclization reaction, resulting in a small ion exchange capacity, which is not preferable.

The reaction temperature is 10 to 200 ° C., preferably 20 ° C. or higher and 200 ° C. or lower. If the temperature is lower than 10 ° C, it becomes difficult to uniformly react due to coagulation of the sulfonating agent and the sulfonation reaction and dehydration cyclization reaction do not proceed sufficiently, which is not preferable. When the temperature is 200 ° C. or higher, the sulfonic acid group and the like are decomposed, which is not preferable. The reaction time is 0.5-10
0 hours is preferable, and particularly 2 hours or more is preferable in order to sufficiently carry out the cyclization reaction.

It is considered that the maximum amount of sulfonic acid groups introduced is 2 per unit unit of the cyclized formula (I), and in the case of 1, the amount is 2.4 meq / g dry resin, 2 In the case of individual pieces, it becomes 4 meq / g dry resin. Therefore, the upper limit of the polymer cation exchange capacity of the present invention is 4 meq /
g dry resin. In addition, the lower limit is 0.0 in terms of membrane resistance.
It is 1 meq / g dry resin or more, preferably 0.5 meq / g dry resin or more.

[0020]

EXAMPLES The present invention will be described in more detail below with reference to examples. These examples do not limit the scope of the invention. In the examples, the properties of the polymer cation exchanger and the membrane were measured by the following methods. Ion exchange capacity : This is the exchange capacity indicated by the neutral salt decomposing ability. About 1 to 3 g of the polymer cation exchange resin or membrane is taken, immersed in 100 ml of 1N-HC1 solution for 5 hours, and then washed with water until it becomes neutral. Next, after drying under reduced pressure at 50 ° C. for 8 hours, 0.5 to 1 g of the dried resin or film was precisely weighed (this weight is referred to as Ag), and 0.5 N-NaCl
100 ml of the solution is added, and the mixture is stirred for 4 hours and then left overnight. After performing suction filtration, the filtrate was washed with 0.1N-NaOH.
Titrate with solution (0.1N-N required for titration at this time)
The amount of aOH solution is Bml). The ion exchange capacity is calculated by the following formula. Ion exchange capacity (milliequivalent / g) = B × (potency of NaOH solution) / 10A

Moisture content : 1 to 3 g of high molecular cation exchange resin or membrane is immersed in pure water for 24 hours, suction filtration is performed on the powdery resin on a funnel, and the water content on the membrane is wiped off with a filter paper. The weight (Wa) of the water-containing resin or film is measured.
Next, the weight (Wb) of the resin or film after vacuum drying at 50 ° C. for 8 hours was measured, and the water content (%) was calculated from the following formula. Moisture content (%) = [(Wa-Wb) / Wa] × 100

Example 1 Poly [diphenylmethane-4,
4'-diyl (parabanic acid)] (Poly [diphenylmethane-4,4 '
-diyl (parabanic acid)]) (hereinafter abbreviated as polyparabanic acid resin. Weight average molecular weight 60,000) of 10 g (0.0
(36 mol) was uniformly dissolved in 250 g (0.78 mol) of 25% fuming sulfuric acid, and the mixture was heated and stirred at 60 ° C. for about 6 hours. Then, the reaction solution was poured into about 2 L of pure water to precipitate a polymer compound. After this was separated by filtration, washing with pure water was repeated in the same manner, and dried under reduced pressure to obtain 12 g of a target light brown powdery polymer cation exchanger. The obtained polymer cation exchanger was analyzed and the following results were obtained.

Ion exchange capacity: 1.4 meq / g dry resin, water content: 37%, ¹³ C-nuclear magnetic resonance spectrum characteristic absorption position (solvent: sulfolane, unit: ppm) in the following structural formula (V) ): (A) 138.8, (b) 130.5, (c) 130.5, (d) 129.1, (e) 12
0.6, (f) 137.1, (j) 150.8, (k) 154.7, (l) 154.7 infrared absorption spectrum characteristic absorption position (unit: cm ^-1 ):
1000, 1130, 1300, 1480

[0024]

[Chemical 6]

Elemental analysis: Elemental measured value (% by weight) C 48.17 H 2.40 N 6.93 S 10.54 From the above results, the polymer cation exchanger obtained in this Example was General formula (VI)

[0026]

[Chemical 7]

It can be seen that the compound has a thioxanthene structure. (Example 2) Polyparabanic acid resin (weight average molecular weight 6
10 million (0.036 mol) of 25% of 1% of 25% fuming sulfuric acid
It was uniformly dissolved in a mixed solvent of 00 g (0.31 mol) and 150 g of concentrated sulfuric acid, and heated and stirred at 80 ° C. for about 6 hours. Then, the reaction solution was poured into about 2 L of pure water to precipitate a polymer compound. After this was filtered off, washing with pure water was repeated in the same manner and drying under reduced pressure to obtain 11.7 g of the desired light brown powdery polymer cation exchanger. Next, 1.2 g of the polymer cation exchanger was added to 18.8 of a sulfolane solvent.
After being uniformly dissolved in g, 20 g of the above-prepared solution is cast onto a glass plate for chromatography provided with a gap of 1 mm in thickness and an effective area of 12 × 12 cm. Next, the cast solution was placed on a shelf in a vacuum dryer kept horizontally and dried under reduced pressure at 80 ° C. for 2 days to obtain a target light brown transparent polymer cation exchange membrane having a thickness of 40 μm. Obtained. The obtained polymer cation exchange membrane was analyzed and the following results were obtained.

Ion exchange capacity: 1.3 meq / g · dry resin, water content: 38%, ¹³ C-nuclear magnetic resonance spectrum characteristic absorption position (solvent: sulfolane, unit: in the above structural formula (V) ppm): (a) 138.7, (b) 130.2, (c) 130.2, (d) 129.1, (e) 12
0.5, (f) 137.0, (j) 150.1, (k) 154.7, (l) 154.7 Infrared absorption spectrum characteristic absorption position (unit: cm ^-1 ) 1000, 1130, 1300, 1480

Elemental analysis: Elemental measured value (% by weight) C 49.64 H 2.50 N 7.19 S 10.40 From the above results, the polymer cation exchange membrane obtained in this example was as follows. General formula (VI)

[0030]

[Chemical 8]

It can be seen that it has a thioxanthene structure.

[0032]

The polymer cation exchanger of the present invention is a heat-resistant polymer cation exchanger having a high ion exchange capacity and excellent thermal stability. Since the exchanger has good solubility in organic solvents such as sulfolane, dimethylsulfolane, dimethylformamide, dimethylsulfoxide, and N-methylpyrrolidone, it can be formed into a thin film by a casting method, and a low resistance film can be obtained. It can be suitably used as a separator for fuel cell membranes, electrolytic membranes and the like.

Claims (2)

[Claims] 1. The following general formula (I): (In the formula, X is —CH ₂ —, —O—, —S—, —SO ₂ —,
Represents -CO-, and n represents an integer of 2 to 500. ), Which comprises a polymer compound containing an aromatic polymer having a structural unit represented by the formula (1), has a cation exchange group having a neutral salt decomposing ability in its aromatic ring, and has an ion exchange capacity of 0.5 to 4
A polymer cation exchanger, characterized in that it is a milliequivalent / g dry resin. 2. The following general formula (II): (In the formula, X is —CH ₂ —, —O—, —S—, —SO ₂ —,
Represents -CO-, and n represents an integer of 2 to 500. The method for producing a polymeric cation exchanger according to claim 1, wherein the aromatic ring of the aromatic linear polymer compound represented by the formula (1) is sulfonated and then dehydrated and cyclized.