GB1585611A

GB1585611A - Anion-exchange resins

Info

Publication number: GB1585611A
Application number: GB2453277A
Authority: GB
Original assignee: Mitsubishi Petrochemical Co Ltd
Current assignee: Mitsubishi Petrochemical Co Ltd
Priority date: 1976-06-12
Filing date: 1977-06-13
Publication date: 1981-03-11
Also published as: DE2725930C2; NL7706386A; DE2725930A1

Description

(54) ANION-EXCHANGE RESINS (71) We, MITSUBISHI PETROCHEMICAL COMPANY LIMITED, a company organized and existing under the Laws of Japan, of 5-2, Marunouchi 2-chome, Chiyoda-ku, Tokyo-to, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates generally to anion exchange resins and more particularly to the production of anion exchange resins having basic ion exchange groups based on imidazoles and the production of anion exchange membranes containing these anion exchange resins in dispersed state.

More specifically, this invention relates to a process for producing strongly basic anion exchangers which, through the avoidance of aliphatic tertiary amines in the formation of their anion-exchange groups, have been improved from the viewpoints of production, environmental health, and heat resistance of the product.

Heretofore, a typical strongly basic ion-exchange resin has contained a quaternary ammonium salt as the ion-exchange group. This quaternary ammonium salt is formed by causing an aliphatic tertiary amine (particularly trimethylamine) to react with a haloalkyl group (particularly a chloromethyl group) introduced onto a cross-linked polymer (e.g., an addition polymer, a poly-addition polymer or a polycondensation polymer).

The methods of producing these strongly basic ion-exchange resins known heretofore have been accompanied by a number of problems as described below.

First, the production process in the known method is, in general, complicated. More specifically, a typical strongly basic ion-exchange resin has been produced by chloromethylating a cross-linked polymer (e.g., a polystyrene cross-linked with divinylbenzene), and converting the resulting product into a quaternary ammonium salt. However, it is necessary to carry out the chloromethylation in the presence of a suitable solvent and a suitable catalyst, and this requirement and the necessity of removing the solvent and the catalyst give rise to complication of the process. Furthermore, trimethylamine is generally used for this conversion into a quaternary ammonium salt, but its use is not desirable for reasons of work environment because this amine is highly malodorous.

Another problem encountered in the practice of a method of this character in which an aliphatic tertiary amine, in particular trimethylamine, is used in the formation of an anionexchange group is the poor heat resistance of the strongly basic ion-exchange resin obtained as the product. In the present state of the art and related industries, in which the use of strongly basic ion-exchange resins at high temperatures is frequently required as the range of applications of these resins expands, inadequate heat resistance not only imposes various restrictions on the uses of these resins but also gives rise to problems in the secondary working processes thereof.

More specifically, the case wherein, as one example of use of an ion-exchange resin, such a resin is used in the form of a membrane may be considered. One method of producing an ion-exchange membrane comprises dispersing a finely particulate ion-exchange resin in a thermoplastic resin matrix in membrane form. In this method, however, since the nembrane is produced by heating and melting (e.g., at a temperature of 180 to 2300C) the thermoplastic resin containing the dispersed ion-exchange resin, if the ion-exchange resin has poor heat resistance, it cannot withstand the heating and melting.

A heterogeneous ion-exchange membrane obtained by dispersing a finely particulate ion-exchange resin in a thermoplastic resin membrane matrix is satisfactory from the viewpoints of production cost, strength of the membrane, and handling characteristics in comparison with a homogeneous ion-exchange membrane (specifically, produced by chloromethylating a cross-linked polymer membrane and converting it into a quaternary ammonium salt with an amine such as trimethylamine), which is a structure obtained by rendering the ion-exchange resin itself into membrane form. Accordingly, it can be said that poor heat resistance of an ion-exchange resin to be dispersed is a great disadvantage.

The inadequate heat resistance of a strongly basic exchange resin having a quaternary ammonium salt based on an aliphatic tertiary amine may be considered to give rise to decomposition of the quaternary ammonium salt due to Hofmann degradation under a high temperature.

It is an object of this invention to overcome the above-described problems by using imidazoles in the formation of the anion-exchange groups and, moreover, by carrying out resinification with the use of epoxy compounds.

Accordingly, the process for producing anion exchange resins according to this invention is characterised in that a compound (a) having a halomethyl group and an oxirane ring in the molecule thereof is caused to react with an imidazole (b), and the modified imidazole (A) thus obtained is caused to react with a polyepoxide compound (B) thereby to produce a resin.

Furthermore, the process for producing anion exchange membranes according to this invention comprises the steps of causing a compound (a) having a halomethyl group and an oxirane ring in the molecule thereof to react with an imidazole (b), causing the modified imidazole (A) thus obtained to react with a polyepoxide compound (B), pulverizing the resin thus obtained thereby to prepare an anion-exchange resin powder, forming this anionexchange resin powder together with a thermoplastic resin at a temperature at which this thermoplastic resin is plastic into a membrane form, and treating the membrane thus formed with heated water.

According to this invention, furthermore, there is provided an anion-exchange resin comprising a resinous reaction product of (A) an imidazole compound (2) modified with a compound (1) having a halomethyl group and an oxirane ring and (B) a polyepoxide compound, said anion-exchange resin having an imidazole content of at least 0.9 mole per 1,000 g of the resin and containing an amino group as an anion-exchange resin, the amino group having been derived from the addition product of the imidazole and an epoxy group and comprising quaternary nitrogen.

Various features of this invention are as follows.

Since an aliphatic tertiary amine is not used, there are no problems from the viewpoints of environmental health during production and of heat stability of the product. Furthermore, the number of production process steps is small, and, moreover, each step can be readily carried out.

An essential characteristic of a strongly basic ion-exchange resin produced by the process of this invention is its good heat resistance. More specifically, for example. when heat weight reduction was measured by means of a thermobalance, no reduction in weight whatsoever was observable up to a temperature of 260"C. Because of this heat resistance, a strongly basic ion-exchange resin of this invention is capable of withstanding not only its use at high temperatures (for example, in ion-exchange in water at a high temperature) but also the thermal conditions encountered when it is dispersed in a thermoplastic resin matrix in membrane form to produce an anion exchange membrane.

Another feature of this invention is that an anion exchange membrane produced according thereto retains the inherent ion-exchange characteristics of the strongly basic ion-exchange resin contained in dispersed state in the membrane and, moreover, possesses properties which are characteristic of this kind of heterogeneous ion-exchange membrane, whereby the mechanical strength and pliability of the membrane are good. For this reason, the membrane can be easily handled and maintained.

Further advantageous features of the ion-exchange membrane of this invention are its good acid resistance and alkali resistance, and the fact that its selectivity does not decrease over a broad pH range. Furthermore, by putting these characteristics to practical use, this membrane can be advantageously utilized, e.g., for desalting in the alkaline region and for the electrodialytic concentration of acidic solutions.

The anion exchange resin according to this invention has a quaternary ammonium group and a tertiary amino group. Furthermore, the anion exchange resin according to this invention is characterised by its rclatively high imidazole content, which is at least 0.9 mole/ 1 ,000g resin, usually from 0.9 to 7.0 moles/1.000g resin, and is preferably from 1.1 to 4.1 moles/1.000 g resin.

The nature, and further features of this invention will be more clearly apparent from the following detailed description beginning with a consideration of the general aspects and features of this invention and concluding with specific examples of practice illustrating preferred embodiments of this invention.

1. Strongly Basic lon-Exchange Resin A strongly basic ion-exchange resin in accordance with one embodiment of this invention is prepared by causing a compound having. intramolecularly, a halomethyl group and an oxirane ring to react with an imidazole so as to form a modified imidazole, and resinifying this latter product with a polyepoxide compound.

l-1. Halomethyl - Oxirane compound The above mentioned compound having intramolecularly a halomethyl group and an oxirane ring is represented by the following formula:

where: X is a halogen. particularly chlorine. bromine. or iodine; and R is a hydrogen atom or a methyl group.

Specific examples of compounds (I) of this character are epichlorohydrin and p-methylepichlorohydrin. These compounds can be used in various combinations thereof.

1-2. Imidazole.

The above-mentioned imidazole is represented by the following formula:

where: R' is a hydrogen atom. a cyanolalkyl group. a triazinoalkyl group. an arylalkyl group or an aryl group; R is a hydrogen atom. a C, to C,7 alkyl group. a cycloalkyl group or an aryl group; and each of R4 and R is a hydrogen atom or a C, to C3 alkyl group.

An alkyl group or an alkyl group moiety without designation of the number of carbon atoms ordinarily has approximately I to 6 carbon atoms. Furthermore. the aryl group is ordinarily phenyl. tolyl or a xylyl group.

Specific examples of such imidazoles are: imidazole. 2-methylimidazole. 2-ethylimidazole.

2-isopropylimidazole. '-undecylimidazole. '-heptadecylimidazole. '-phenvlimidazole.

w.4-dimethylimidazole. 2-ethyl-4-methylimidazole. 7-phenyl-4-methylimidazole. l-benzql- 2-methylimidazole. I -cyanoethyl-2-methylimidazole. I -cyanoethyl-2 .4-dimethyl -imidazole.

l-cyanoethyl-'-isopropylimidazole. l-cyanoethyl-2-phenyl-imidazole. 1-(3.5-diamino- triazinoethyl)-2-methyl-imidazole and l-(3.5-diamino-triazinoethyl) -2-ethyl-4-methylimidazole. These imidazoles can be used in combinations thereof.

1-3. Preparation of modified imidazole.

In general. when an imidazole is caused to react with a compound having. intramolecularly.

a chloromethyl group and an oxirane ring. such as epichlorohydrin. a ring opened addition product is formed.

Reaction is carried out with a suitable quantity above 0.5 mole of the halomethyl - oxirane compound d for each I mole of the imidazole.

For carrying out this reaction smoothlv. an organic hydroxyl compound is generally added in a quantity in a range of 10 to 200 percent by weight. preferably from 30 to 150 percent by weight. with respect to the quantity of the imadazole. In addition to its function as a solvent of the imidazole. the hvdroxyl compound serves also as a catalyst for the reaction for forming the modified imidazole. Furthermore, we have found that the hydroxy compound used in this process step is highly effective also as a diluent in the resinification reaction with the use of the polyepoxide compound of the succeeding process step.

Examples of hydroxyl compounds exhibiting this effectiveness are: saturated monohydric alcohols having 1 to 6 carbon atoms, particularly primary alcohols, such as methanol, ethanol, propanols, and butanols; polyhydric alcohols having 2 to 5 carbon atoms such as ethylene glycol, propylene glycols, butylene glycols, glycerol, diethylene glycol, ethylene glycol monomethylether; and phenols such as phenol, cresols, xylenols, catechol and resorcinol.

These hydroxy compounds can be used in various combinations thereof.

1-4. Polyepoxide compound.

The term "polyepoxide" is herein used to designate an epoxy compound containing two or more oxirane rings.

One group of such epoxy compounds suitable for use in this invention comprises those known as so-called epoxy resins with an epoxy equivalent in the range of from 100 to 600.

Specific examples of these compounds are bisphenol epoxy resins (e.g., bisphenol A diglycidylether), novolak epoxy resins (e.g., phenol novolak glycidylether), polyphenol epoxy resins (e.g., tetrahydroxyphenylethane tetraglycidylether), polyglycol epoxy resins (e.g., glycerol triglycidylether), carboxylic acid epoxy resins (e.g., diclycidyl phthalate), amine epoxy resins (e.g.. glycidylaniline) and alicyclic epoxy resins (e.g., vinylcyclohexenediepoxide). These epoxy compounds can be used in various combinations thereof.

Another group of epoxy compounds suitable for use in this invention comprises homopolymers of, and copolymers with, e.g. styrene, of an ethylenically unsaturated monomer containing a glycidyl group such as, for example, unsaturated carboxylic acid glycidyl esters, e.g. glycidyl methacrylate.

1-5. Resinification with the polyepoxide compound.

The heating and hardening reaction of the modified imidazole prepared as described in section 1-3. above and the polyepoxide compound is carried out by uniformly mixing these two ingredients in a specific quantitative ratio and thereafter heating the mixture.

In general, the polyepoxide compound is used in a quantity of from 20 to 70 percent by weight, preferably from 30 to 60 percent by weight of the total weight of its mixture with the modified imidazole. The heating is carried out at from 60 to 1900C, preferably from 70 to 1800C. The heating time is of the order of 3 to 15 hours. The hardening by heating can be carried out in the presence of a diluent. A specific example of a suitable diluent is any one of the aforedescribed hydroxy compounds.

1-6. Granulation of the strongly basic ion-exchange resin formed.

By the above-described reaction. lumps of a strongly basic ion exchange resin are produced, and these are granulated into particles of a suitable size, which is in the range of 20 to 60 mesh, preferably 20 to 48 mesh, (Tyler). In the case where a heterogeneous ion-exchange memberane is to be produced, this particle size is preferably below 325 mesh.

The granulation can be carried out by means of a ball mill or other suitable pulverizing apparatus.

Still another method of pulverization utilizes a unique characteristic of the ion-exchange resin according to this invention, and comprises hydrating the resin lumps in a large quantity of an aqueous medium so as to cause the lumps to undergo self-disintegration. Examples of aqueous mcdia other than water are methanol and ethanol. The hydration temperature is in the range of from 20 to 1000C.

After granulation. the resin is washed successively with a dilute acid (for example. an inorganic acid, e.g.. hydrochloric acid. sulphuric acid or nitric acid, of a concentration in the range of 0.05 to 2 normal) and a dilute alkali (for example. an alkali hydroxide. e.g., sodium hydroxide. potassium hydroxide or ammonium hydroxide, at a concentration in the range of 0.05 to 2 normal). the washing sequence being immaterial. so as to remove soluble unreacted substances. Finally. the resin is washed thoroughly with pure water, whcreupon a strongly basic ion-exchange resin of this invention is obtained in particulate state.

2. Membrane Fabrication In accordance with one feature of this invention the strongly basic ion-exchange resin in powdery state obtained in the above-described manner is mixed with a thermoplastic resin.

and the resulting mixture is heated to a temperature at which the thermoplastic resin plasticizes and is thus formed into a membrane structure. After forming. the membrane is processed with heated water.

First. for the thermoplastic resin to form the matrix. any thermoplastic resin which plasticizes at a temperature at which decomposition of the strongly basic ion-exchange resin of the invention does not occur can be used. As mentioned hereinbefore. in general. no thermal decomposition of the strongly basic ion-exchange resins of the invention can be observed at temperatures up to approximately 260C.

Specific examples of suitable thermoplastic resins are: polyolefins. for example.

homopolymers and mutual copolymers of olefins such as ethylene, propylene and butene- 1; copolymers of these olefins with other ethylenically unsaturated monomers such as vinyl acetate; homopolymers and copolymers of vinyl aromatics such as a styrene; homopolymers and copolymers of methacrylic acid esters such as methyl methacrylate; homopolymers and copolymers of fluoromonomers such as tetrafluoroethylene, monochlorotrifluoroethylene, vinyl fluoride and vinylidene fluoride; polyamides; and polyoxymethylene. These resins may be used in various combinations thereof and, furthermore, may contain a suitable filler, foaming or blowing agent, stabilizer, plasticizer, colouring matter or other auxiliary material(s).

The weight ratio of the thermoplastic resin to the ion-exchange resin is generally in the range of from 75:25 to 25:75, preferably in the range of 70:30 to 30:70.

The membrane is formed by kneading a mixture of the thermoplastic resin in a state ranging from powder to particles and the ion-exchange resin in a powdery state at a temperature at which the former resin plasticizes, preferably at which it melts, for example, a temperature above 1600C in the case of a polyolefin, and forming the resulting resin into a membrane by a process such as extrusion through a T-die, extrusion by means of mixing rolls, pressurizing in a female-male mould, and casting. The membrane can be thus formed to any thickness, but the thickness is generally in the range of 0.10 to 1.0 mm.

The article of membrane form thus produced is rendered by an after-treatment into a product exhibiting the properties of an anion-exchange membrane according to this invention. The after-treatment comprises treatment of the membrane in hot water at a temperature of or above 70"C, preferably of or above 80"C. This hot water may contain an acid, an alkali, a salt, and other additives, For example, this after-treatment can be carried out by holding the membrane in an aqueous solution (at a temperature in the range of 70 to 1 100C) of an alkali metal salt or an ammonium salt, for example, at a concentration higher than 5 percent by weight, preferably higher than 7 percent by weight, for more than 20 minutes, preferably 30 to 60 minutes.

Specific examples of alkali metal salts and ammonium salts are: halides such as lithium chloride, sodium chloride. potassium chloride. rubidium chloride, cesium chloride, lithium bromide, sodium bromide, potassium bromide, rubidium bromide, cesium bromide, lithium iodide, sodium iodide, potassium iodide, rubidium iodide, cesium iodide; sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, rubidium sulfate, cesium sulfate; nitrates such as lithium nitrate, sodium nitrate, potassium nitrate, rubidium nitrate, cesium nitrate; phosphates such as lithium phosphate, sodium phosphate, potassium phosphate, rubidium phosphate, cesium phosphate; acetates such as lithium acetate, sodium acetate, potassium acetate, rubidium acetate, cesium acetate; and ammonium salts such as ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium phosphate and ammonium acetate.

These salts can be used in combinations thereof.

Upon completion of the reaction, the materials obtained are separated by filtration and suitably washed, whereupon the product of this invention is obtained.

In order to indicate more fully the nature and features of this invention, the following examples of practice constituting preferred embodiments of the invention and a comparative example are set forth, it being understood that these examples are presented as illustrative only and are not intended to limit the scope of the invention. Parts and percentages are by weight.

Example I Into a four-necked flask equipped with a reflux condenser, a thermometer and a mechanical stirrer are placed 25 grams (g) of imidazole, and 25 ml. of ethanol and 5 ml. of ethylene glycol are added to produce a homogeneous mixture.

At a constant temperature of 55 to 60"C, 30 g of epichlorohydrin are added dropwise over about 30 minutes under stirring. and the stirring is continued for a further 5 hours.

Sixty (60) parts of the thus produced modified imidazole and 40 parts of an epoxy resin "Epikote 828" (trade mark) of WPE (weight per epoxy equivalent) 180 produced by Shell Chemical, which is a bifunctional epoxy compound. are mixed, and the resulting homogeneous mixture is then subjected to a hardening processing which is similar to a conventional one, and which comprises heating at 70"C for 1 hour and at 1500C for 4 hours. The resulting hardened mass is allowed to cool. and the mass is then left standing in water. whereby it is easily degraded into particulate form of 20 to 60 mesh size. The time required for the degradation can be materially shortened if the degradation is carried out at an elevated temperature such as 80"C under agitation.

The resulting particulate mass is washed with 3% hydrochloric acid solution and then with 3% caustic soda solution thereby to remove any soluble unreacted materials. Finally. the mass is washed amply with pure water.

In actual practice. the particulate resin was found to have a salt splitting capacity of 2.0 meq/g. an imidazole content of 3.1 mol/ 1 ,000g, and a total exchange capacity of 3.9 meq/g, all on dry basis.

In order to test the heat stability of the resin thus produced, the resin conditioned to be in a Cl-form was subjected to a determination of weight loss upon heating at a temperature raised at the rate of 100C/min. by means of a differential thermal balance which was a constanttemperature type differential thermal balance manufactured by Rigaku Denki, Model 8002H. No weight-loss was found before the temperature reached 260"C. Weight loss under the same conditions of a commercially available strong-base ion-exchange resin which was based on a trimethylammonium styrene-divinylbenzene copolymer with a degree of crosslinking of 8%, Cl-form, was 13% at 2000C and 25% at 2600C.

after being treated in hot water at 900C in air for 200 hours, the resin in accordance with the present invention conditioned to be in the Cl-form was found to have a salt splitting capacity of 1.9 meq./g, and a total exchange capacity of 3.8 meq/g, all on dry basis. The resin thus produced had high heat stability.

Example 2 Forty (40) parts of the modified imidazole produced in Example 1 and 60 parts of "Epikote 828" (trade mark) of WPE 180 are homogeneously mixed. The homogeneous mixture thus obtained is then subjected to heat-hardening processing by the same procedure as in Example 1. After being cooled, the resulting hardened mass is ground into powder by a crusher to produce a resin in granular form. The resulting granular resin is washed with 3 % hydrochloric acid solution and then with 3 % caustic soda solution. Finally, the resin is washed amply with pure water. In an instance of actual practice, the resin thus obtained was found to have a neutral salt decomposition capacity of 1.5 meq./g, animidazole content of 2.3 mol/1,000g and a total ion-exchange capacity of 2.6 meq/g, all on dry basis.

Example 3 Seven (7) parts of "Epikote 1031" (trade mark) of WPE 220 produced by Shell Chemical and 38 parts of "Epikote 828" (trade mark) of WPE 180 are heated to produce a homogeneous mixture. To the resulting homogeneous mixture are added 55 parts of modified imidazole produced in Example 1. The resulting mixture is then subjected to the same heat-hardening processing and after-treatment as in Example 1.

In actual practice, the resin thus produced and finally washed with pure water was found to have a salt splitting capacity of 1.5 meq/g, an imidazole content of 2.4 mol/ 1,000 g. and a total ion-exchange capacity of 2.9 meq/g, all on dry basis.

Example 4 Sixty (60) parts of the modified imidazole produced in Example 1 and 40 parts of a glycidyl methacrylate-styrene copolymer (50: 50 by weight ratio) which is produced by a suspension polymerization method, and which is in granular form of 20 to 60 mesh size are mixed, and the resulting mixture is then subjected to a hardening processing at 70"C for 2 hours and at 1500C for 5 hours. The resulting hardened mass is allowed to cool, and the mass is then ground into granules by a crusher. The resulting granular resin is washed with 3 Ojo hydroch- loric acid solution and then with 3% caustic soda solution. Finally, the resin is washed with pure water.

The resin thus produced in an instance of actual practice was found to have a salt splitting capacity of 0.8 meq/g, an imidazole content of 1.9 mol/ 1.000 g, and a total exchange capacity of 1.9 meq/g, all on a dry basis.

Example 5 Into a homogeneous mixture consisting of 29 g of 2-methyl imidazole, 25 ml. of ethanol and 5 ml. of glycerol are added dropwise 10 g of epichlorohydrin in the same way as in Example 1 to produce a modified methylimidazole.

Sixty (60) parts of the thus produced modified imidazole and 40 parts of "Epikote 828" (trade mark) are homogeneously mixed and then subjected to the same heat-hardening processing and after-treatment as in Example 1.

In actual practice. the resulting resin thus produced and finally washed with pure water was found to have a salt splitting capacity of 1.8 meq/g. an imidazole content of 2.3 mol/ 1,000 g and a total ion-exchange capacity of 3.4 meq/g, all on a dry basis.

Example 6 Into a homogeneous mixture consisting of 39 g of 2-ethyl-4-methylimidazole. 25 ml. of isopropyl-alcohol and 5 ml. of ethyleneglycol are added dropwise 30 g of epichlorohydrin in the same way as in Example 1 to produce modified 2-ethyl-4-methylimidazole.

Fifty-five (55) parts of the thus produced modified imidazole and 45 parts of "Epikote 828" (trade mark) are homogeneously mixed, and then subjected to the same heat-hardening processing and after-treatment as in Example 1.

The resulting resin thus produced and finally washed with pure water in actual practice was found to have a salt splitting capacity of 1.3 meq/g. an imidazole content of 2. 1 mol/ 1.000 g.

and a total ion-exchange capacity of 1.9 meq/g. all an dry basis.

Example 7 Into a homogeneous mixture consisting of 48 g of 1-cyanoethyl-2-methylimidazole, 25 ml.

of ethanol and 5 ml. of ethylenglycol are added dropwise 30 g of epichlorohydrin in the same way as in Example 1 to produce a modified 1-cyanoethyl-2-methylimidazole.

Sixty (60) parts of the thus produced modified compound and 40 parts of "Epikote 828" (trade marks) are homogeneously mixed, and then subjected to the same heat-hardening processing and after-treatment as in Example 1.

The resulting resin thus produced and finally washed with pure water in one instance of practice was found to have a neutral salt decomposition capacity of 1.0 meq/g, an imidale content of 2.1 mol/ 1,000 g, and a total ion-exchange capacity of 2.0 meq / g, all on drv basis.

Example 8 a) An example of production of ion-exchange resin Into a four-necked flask equipped with a reflux condenser, a thermometer and a mechanical stirrer are placed 25 g of imidazole, and 25 ml. of ethanol and 5 ml. of ethyleneglycol are added to produce a homogeneous mixture.

At a constant temperature of 55 to 60"C, 30 g of epichlorohydrin are added dropwise over about 30 minutes under

Comparative Example 1 a) Production ofheterngeneous anion-exchange membrane from commercially available strong-base exchange resin Sixty (60) parts of powdery anion-exchange resin which were produced by comminuting into 325 mesh size or below by a vibrating mill, a commercially available styrene-based, strongly basic ion-exchange resin "Dia Ion PA 316" (trade mark) produced by Mitsubishi Kasei K.K.K. whose salt splitting capacity was 1.45 meq/g, on dry basis, and 40 parts of polypropylene resin of MI 6 were mixed, and the resulting mixture was then subjected to the same forming and after-treatment processing as in Example 8.

b) Characteristics of the thus formed exchange membrane The salt splitting capacity, thickness, ion transport number and specific resistance of the anion-exchange membrane thus produced were 0.2 meq/g, on a dry basis, 0.5 mm, 0.93 and 1200 fl-cm, respectively. This showed that the above exchange membrane did not have good electrical characteristics.

Example 9 Fifty (50) parts of the powdery anion-exchange resin (A) produced in Example 8 and 50 parts of high density polyethylene of M15 were mixed, and the resulting mixture was then subjected to the same forming processing as in Example 8 to produce a membrane.

The thus produced membrane was then dipped in hot water at 950C for 30 minutes tO produce a heterogeneous anion-exchange membrane.

The salt splitting capacity, thickness, ion transport number and specific resistance of the anion-exchange membrane thus produced were 1.0 meq/g, on a dry basis, 0.55 mm, 0.85 and 90hl-cm, respectively.

Examples 10 to 13 The membrane (B) produced in Example 8 was dipped in 20% alkali metallic salt aqueous solutions and 20% ammonium salt aqueous solution as hereinafter shown in Table 1 at 100 0C for 30 minutes to produce a heterogeneous anion-exchange membrane.

The thickness, ion transport number and specific resistance of the heterogeneous anionexchange membrane thus produced were respectively as set forth in Table 1.

Table 1

Example Example 10 1 Example 11 | Example 12 Example 13 Alkali me tal salt and ammonium Potassium Sodium Sodium Ammonium salt chloride carbonate sulfate sulfate Thickness (mm) 0.50 0.50 0.50 0.50 Ion trans port number 0.93 0.94 0.91 0.91 Specific resistance (Q-cm) l 125 190 170 l 150 Example 14 a) Production of ion-exchange resin Into a homogeneous solution consisting of 29 g of 2-methylimidazole, 25 ml. of ethanol and 5 mol. of glycerol are added dropwise 30 g of epichlorohydrin in the same way as in Example 8 to produce a modified imidazole.

Sixty (60) parts of the thus produced modified imidazole and 40 parts of "Epikote 828" (trade mark) are mixed. and the resulting homogeneous mixture is then subjected to heathardening and after-treatment processings in the same way as in Example 8.

The resin thus produced and finally washed with pure water is dried, and then comminuted into 325 mesh or below by a vibrating mill.

The thus comminuted resin was found in actual practice to have a salt splitting capacity of 1.8 meq/g, an imidazole content of 2.3 mol/ 1,000 g, and a total ion-exchange capacity of 3.4 meq/g, all on dry basis. This comminuted resin is designated hereinafter as powder resin (C).

b) Production of heterogeneous anion-exchange membrane Sixty (60) parts of the above powdery anion resin (C) and 40 parts of polypropylene resin powder of MI 6 are mixed, and the resulting mixture is then subjected to forming processing and after-treatment processing in the same way as in Example 8.

In actual practice, the anion-exchange membrane thus produced was found to have a salt splitting capacity of 1.1 meq/g, on a dry basis, a thickness of 0.54 mm, an ion transport number of 0.92, and a specific resistance of 195 fl-cm.

WHAT WE CLAIM IS: 1. A process for producing an anion-exchange resin which comprises reacting a compound (1) having a halomethyl group and an oxirane ring in the molecule thereof with an imidazole compound (2), and reacting the modified imidazole thus obtained with a polyepoxide compound (3) thereby to produce a resin which has an imidazole content of at least 0.9 mole per 1,000 g of the resin.

2. A process as claimed in claim 1 in which the compound (1) has the formula:

where X is a halogen, and R is hydrogen or methyl.

3. A process as claimed in claim 1 or 2, in which the compound (1) is epichlorohydrin.

4. A process as claimed in any of claims 1 to 3, in which the compound (2) has the formula:

wherein Rl is hydrogen, cyanoalkyl, triazinoalkyl, arylalkyl or aryl, R2 is hydrogen, C1 - C17 alkyl, cycloalkyl or aryl, and R4 and R5, which may be the same or different, are respectively hydrogen or C, - C3 alkyl.

5. A process as claimed in claim 4, in which, in R' and R2, the alkyl group or alkyl moiety has from 1 to 6 carbon atoms and the aryl group is phenyl, tolyl or xylyl.

6. A process as claimed in any of claims 1 to 5, in which the compound (2) is imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole or 1-cyanoethyl-2-methylimidazole.

7. A process as claimed in any of claims 1 - 6, in which the polyepoxide compound (3) is an epoxy resin which has at least two oxirane rings and which has an epoxy equivalent of from 100 to 600.

8. A process as claimed in claim 7, in which the epoxy resin is a reaction product of bisphenol A and an epihalohydrin.

9. A process as claimed in any of claims 1 to 8 in which the reaction of the compound (1) and the imidazole compound (2) is effected in the presence of an organic hydroxyl compound.

10. A process as claimed in claim 9, in which the organic hydroxyl compound is a saturated monohydric alcohol of 1 to 6 carbon atoms, a polyhydric alcohol of 2 to 5 carbon atoms. or a phenol.

I 1. A process as claimed in any of claims 1 to 10, in which the resin obtained is hydrated in an aqueous medium so as to be self-disintegrated into a granular form.

12. A process as claimed in any of claims 1 to Il, in which the resin obtained is washed with a dilute acid. a dilute alkali and water.

13. A process as claimed in Claim I for producing an anion-exchange resin substantially as hereinbefore described with reference to any of the specific examples.

14. A process for producing an anion-exchange membrane which comprises providing a powder of an anion-exchange resin produced by a process as claimed in any of claims I to 13, forming a mixture of the powder of an anion-exchange resin with a thermoplastic resin, at a temperature at which the thermoplastic resin is plasticised, into a membrane. and treating the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. 1.8 meq/g, an imidazole content of 2.3 mol/ 1,000 g, and a total ion-exchange capacity of 3.4 meq/g, all on dry basis. This comminuted resin is designated hereinafter as powder resin (C). b) Production of heterogeneous anion-exchange membrane Sixty (60) parts of the above powdery anion resin (C) and 40 parts of polypropylene resin powder of MI 6 are mixed, and the resulting mixture is then subjected to forming processing and after-treatment processing in the same way as in Example 8. In actual practice, the anion-exchange membrane thus produced was found to have a salt splitting capacity of 1.1 meq/g, on a dry basis, a thickness of 0.54 mm, an ion transport number of 0.92, and a specific resistance of 195 fl-cm. WHAT WE CLAIM IS:

1. A process for producing an anion-exchange resin which comprises reacting a compound (1) having a halomethyl group and an oxirane ring in the molecule thereof with an imidazole compound (2), and reacting the modified imidazole thus obtained with a polyepoxide compound (3) thereby to produce a resin which has an imidazole content of at least 0.9 mole per 1,000 g of the resin.

2. A process as claimed in claim 1 in which the compound (1) has the formula:

where X is a halogen, and R is hydrogen or methyl.

membrane thus obtained with water under heat.

15. A process as claimed in claim 14, in which the thermoplastic resin is a homopolymer or copolymer of an olefin.

16. A process as claimed in claim 15, in which the homopolymer or copolymer of an olefin is polyethylene or polypropylene.

17. An anion-exchange resin comprising a resinous reaction product of (A) an imidazole compound (2) modified with a compound (1) having a halomethyl group and an oxirane ring and (B) a polyepoxide compound, said anion-exchange resin having an imidazole content of at least 0.9 mole per 1,000 g of the resin and containing an amino group as an anion-exchange resin, the amino group having been derived from the addition product of the imidazole and an epoxy group and comprising quaternary nitrogen.

18. An anion-exchange resin as claimed in claim 17, substantially as herein described with reference to any of the specific examples.