GB2232987A - Ion exchange resin beads - Google Patents

Abstract

Resin beads having a polymeric matrix and functional groups consist of a) ionic groups being bound to the polymeric matrix and b) exchangeable counter-ions are disclosed wherein a portion of the exchangeable counter-ions b) have oxidative properties. A coating is produced on the resin beads by oxidative polymerisation of aromatic compounds, such as aniline, thiophene and pyrrole, under partial or complete reduction of the exchangeable counter-ions having oxidative properties. The coated beads are a different colour to the uncoated beads and make it easy to distinguish between anion and cation resins when both are present as a mixture, and only one type has been subject to the coating procedure.

Description

ION EXCHANGE RESIN BEADS AND METHOD OF SEPARATING ANION AND CATION EXCHANGE RESIN BEADS The present invention relates to resin beads having a polymeric matrix and functional groups consisting of a) ionic groups being bound to the polymeric matrix and b) exchangeable counter-ions and to a process of preparing them. The present invention further relates to a method of separating different types of resin beads of which a portion has exchangeable anions and a portion has exchangeable cations.

Background of the Invention Resin beads which have a polymeric matrix and functional groups consisting of a) ionic groups which are bound to the polymeric matrix and b) exchangeable counter-ions are well known in the art. They are useful for removing ions from salt solutions and therefore have found many applications, for example for the deionisation of water, for recovering precious metal ions from solutions or for water purification where noxious ions are removed from aqueous solutions.

Thereby ions in the resin beads are exchanged with ions in the solution. Accordingly, the resin beads are commonly called ion exchange resin beads. Those having anionic exchangeable counter-ions such as halogen ions are classified as anion exchange resin beads and those having cationic exchangeable counter-ions such as alkali metal or alkaline earth metal ions are classified as cation exchange resin beads. Fundamental ion exchange technology is published in Ion Exchange by F. Helfferich, published in 1962 by McGraw-Hill Book Company, N.Y. and in Ullmann's Enzyklopadie der Technischen Chemie, 4th Edition, Vol. 13, pages 279 et seq.

In many applications such as water purification, cations and anions are to be removed from liquids. Therefore, cation and anion exchange resin beads are used together for these applications. The cation and anion exchange resin beads can be placed in subsequent separate beds or together in an filter bed.

In the latter case either the filter bed is filled with alternating layers of cation exchange resin beads and anion exchange resin beads or the cation and anion exchange resin beads are mixed before the filter bed is filled. After their use, the exhausted cation and anion exchange resin beads are usually separated for regeneration. It is useful to be able to distinguish the cation and anion exchange resin beads in order to ensure that the separation of the two resins is complete. In the past, the resin beads have been separated according to their inherent colour, however, the difference between the inherent colour of the cation and anion exchange resin beads often is too small to enable the separation of the resin beads in an easy way. Therefore, dyestuffs have been used for eying the resin beads, however, only a very inhomogeneous colouring has been achieved.

Accordingly, it would be desirable to provide a new process for selectively dyeing either cation or anion exchange resin beads whereby the resin beads are dyed in a more homogeneous fashion. Furthermore, it would be desirable to provide such dyed resin beads.

When cation and anion exchange resin beads are used together as described above, the total volume of the beads is larger than the sum of the separated cation and anion exchange resin beads. This fact is well known in the industry and is due to a clumping effect between the cation and anion exchange resin beads. This clumping effect is undesirable because the ion exchange capacity per volume of the resin beads is decreased which renders the use of the resins more expensive.

Accordingly, it would be desirable to provide new cation exchange resin beads which can be used together with known anion exchange resin beads without having to put up with a substantial clumping effect.

Much research efforts have also been spent on influencing the properties of cation exchange resin beads in such a manner that the cation exchange resin beads selectively absorb or at least have a preference for a special kind of cations which are present in the solution contacting the resin beads. Such preference of the cation exchange resin beads for special types of cations can be based on a different size or a different valency of the cations which are present in the solution to be treated. In particular in the case of water purification, generally monovalent and polyvalent cations are present in the aqueous solution to be treated.Accordingly, it would be desirable to influence the properties of known cation exchange resins in such a manner that the cation exchange resin beads have a preference for certain types of cations, based on the different valencies of the individual cations.

Summary of the Invention One aspect of the present invention are resin beads having a polymeric matrix and functional groups consisting of a) ionic groups being bound to the polymeric matrix and b) exchangeable counter-ions, characterised in that a portion of the exchangeable counter-ions b) have oxidating properties in the uncoated state of the resin beads and the resin beads contain a coating produced by oxidative polymerisation of one or more aromatic compounds under partial or complete reduction of the exchangeable counter-ions having oxidative properties.

By the term "a portion of the exchangeable counter-ion b) have oxidative properties" is meant ions which have a redox potential sufficient for oxidative polymerisation of an aromatic compound described below.

Such ions are present in the resin beads only to such an extent that the coated resin beads of the present invention still have an ion exchange capacity.

Accordingly, not all of the exchangeable counter-ions b) may have oxidating properties in the uncoated state of the resin beads.

A further aspect of the present invention is process for producing the resin beads of the present invention, which process is characterised in that in a first step resin beads having a polymeric matrix and functional groups consisting of a) ionic groups being bound to polymeric matrix and c) exchangeable counterions are contacted with a solution containing ions having oxidative properties to effect a partial exchange of the counter-ions and in a second step said resin beads are contacted with an oxidatively polymerisable aromatic compound. The exchangeable counter-ions c) of the resin beads used in the first step do usually not have oxidative properties.

Yet another aspect of the present invention is a process for producing the resin beads of the present invention, which process is characterised in that resin beads having a polymeric matrix and functional groups consisting of a) ionic groups being bound to polymeric matrix and b) exchangeable counter-ions having oxidative properties are contacted with an oxidatively polymerisable aromatic compound.

By the process of the present invention either resin beads having cationic exchangeable counter-ions b) or resin beads having anionic exchangeable counterions b) can be selectively coated and dyed.

When the resin beads are contacted in a first step with a solution containing cations having oxidative properties, such as Fe3+ ions, cation exchange resin beads are selectively coated and dyed. When the resin beads are contacted in a first step with a solution containing anions having oxidative properties, such as S2082- groups, anion exchange resin beads are selectively coated and dyed. Accordingly, in a mixture containing cation and anion exchange resin beads either the cation or the anion exchange resin beads can be selectively dyed according to the process of the present invention. This allows a subsequent separation of cation or anion exchange resin beads. The process of the present invention also allows identification of impurities in ion exchange resin beads and their separation. Traces of cation exchange resin beads which are impurities in anion exchange resin beads and vice versa can be identified and removed.

Accordingly, a further aspect of the present invention is a method of separating different types of resin beads, a portion thereof having exchangeable cations and a portion thereof having exchangeable anions by 1) selectively exchanging either said cations or said anions partially with ions having oxidative properties and 2) effecting oxidative polymerisation of an aromatic compound in the presence of the resin beads whereby the beads containing ions having oxidative properties are selectively coated with the polymerised aromatic compound and change their colour and 3) separating the coated and uncoated resin beads according to their colours.

When the coated resin beads of the present invention which have anionic groups a) being bound to the polymeric matrix and cationic exchangeable counterions c) are used together with standard anion exchange resin beads, the combination of such resin beads does not show the above discussed undesirable clumping effect to a substantial extent.

Accordingly, a further aspect of the present invention is a container wherein A) resin beads having a polymeric matrix and functional groups consisting of cat ionic groups being bound to the polymeric matrix and exchangeable anions and B) resin beads of the present invention having anionic groups a) being bound to the polymeric matrix and exchangeable cations are arranged in a mixed or a layered fashion.

By "layered fashion" is meant that the container may contain one or more layers of standard anion exchange resin beads and one or more layers of the coated cation exchange resin beads of the present invention which are alternately arranged.

Furthermore, it has found that the coated resin beads of the present invention having cat ionic exchangeable counter-ions c) have a preference for absorbing mono-valent cations over polyvalent cations.

Accordingly, yet another aspect of the present invention is the use of the resin beads of the present invention having anionic groups a) and cationic exchangeable counter-ions c) for at least partially separating monovalent and polyvalent cations.

Detailed Description of the Invention The resin beads of the present invention contain a coating which is produced by oxidative polymerisation of one or more aromatic compounds such as pyrrole. It is well known that polypyrrole can be synthesized through oxidative polymerisation of pyrrole, for example with potassium peroxydisulphate, potassium permanganate, sodium perborate, potassium bichromate, FeC13 or quinones (K.C. Khulbe and R.S.

Mann, Journal of Polymer Science, Vol. 20, pages 1089 et seq, 1982 and DE-A-3325892). It is also known to produce polypyrrole by electrochemical oxidative polymerisation of pyrrole (A.F. Diarz et al., J.C.S., Chem. Comm., 1979, pages 635 and 636, DE-A-3318856 and DE-A-3402133.

According to these teachings black polypyrrole is obtained in the form of a powder or film or may be deposited as a coating on an electrode.

Others have suggested preparing composite films of polypyrrole and PVC, polyimides, polystyrenes and polymethacrylates Co. Niwa et al., J. Chem. Soc., Chem.

Commun., 1984, pages 817 and 818; M.-A. De Paoli et al., J. Chem. Soc., Chem. Commun., 1984, pages 1015 and 1016 and EP-A-191726). The polystyrenes, polymethacrylates or PVC may contain redoxactive groups which have in the oxidised or reduced state an active potential which is sufficient for oxidation of polypyrrole (DE-A-3419788).

P. Aldebert et al., J. Chem. Soc., Chem.

Commun., 1986, pages 1636 to 1638 disclose polymer alloys with mixed electronic and ionic conductivity which have been synthesised from perfluorosulphonated ionomer membranes and monomer precursors of electronically conducting polypyrrole or polyaniline. A commercially available solid acidic Nafion (Trademark) film is soaked in an aqueous solution containing 2M Fe(C104)3 and 0.5 M HC104. The proton sites of the nafion film are exchanged by iron(III) ions. The Nafion film is produced from an ionomeric polymer containing -S03 group. Polymerisation of aniline inside the ionic membrane is obtained by soaking the Fe3+ exchanged Nafion in a 1M aqueous solution of aniline acidified with H2S04 or HC104.

The ion exchange properties of polypyrrole salt films by treatment with an aqueous sodium hydroxide solution and sulphuric acid have been studied by H. Münstedt, Polymer, 1986, Vol. 27, June, pages 899 to 904.

R.M. Penner et al., J. Electrochem. Soc., Electrochem. Sci. and Techn., Vol. 133, No. 2, Feb.

1986, pages 310 to 315 describe electronically conductive composite membranes prepared by electropolymerising pyrrole or thiophene within a ionically conductive NIGT membrane. The NIGT membrane is prepared by impregnating a polytetrafluoroethylene membrane, "Gore-tex" (Trademark) with a perfluorosulfonate ionomer, "cation". The NIGT membrane has a thickness of 25 micrometers.

A variety of applications has been suggested for electrically conductive polypyrrole, such as batteries, electrical semi-conductors or electromagnetic shielding. DE-A-3314817 discloses the use of electrochemically produced pyrrole polymers as ion exchange membranes. These membranes are selectively permeable to protons and small anions, in particular monovalent anions, such as chloride but they are substantially impermeable to cations and large anions.

In particular, they are impermeable to multivalent ions, such as sulphate, Fe2+, Fe3+ or Ti3+. The electrically conductive polypyrrole is produced by oxidative polymerisation whereby the polymers are deposited as a film on an anode. The produced film has a thickness of 0.01 to 1 mm, preferably of 0.05 to 0.2 mm.

Although it has been suggested to use electrochemically polymerised pyrrole as an ion exchange membrane and it has further been suggested to deposit polyaniline on a host membrane, such as a Nafion film, by oxidative polymerisation, it is highly surprising that an aromatic compound, such as pyrrole, can be polymerised on and/or into resin beads having a polymeric matrix. Usually, resin beads are modified by chemical treatment; their mechanical strength often is significantly decreased when modifying the resin beads which renders the beads less valuable for future applications. Furthermore, ion exchange resin beads contain a concentration of functional groups, per weight of the beads, which is about 4 to 7 times as high a the concentration of functional groups in membranes or films, such as a Nafion film (per weight of the film or membrane).Furthermore, in the prior art it has been suggested to deposit polypyrrole on thin films having a thickness of up to 1 mm. The resin beads have a substantially spherical shape and usually a diameter of 0.25 to 1.20 mm, preferably of 0.35 to 0.80 mm.

Furthermore, it is highly surprising that ion exchange resin beads can be provided with a dark colour according to the process of the present invention without affecting the ion exchange capacities to a substantial extent. The beads of the present invention usually have a brown to grey-black, green to brown, green to black or a deep black colour. After the treatment according to the process of the present invention the resin beads retain their original mechanical properties and their physical properties, such as the ion exchange kinetics to a substantial extent. Cation exchange resin beads retain up to 98 percent of their original sodium capacity.

The ion exchange resin beads of the present invention may be prepared from known resin beads having a polymeric matrix and functional groups consisting of a) ionic groups being bound to the polymeric matrix and b) exchangeable counter-ions.

Various cross-linked polymers are useful as a matrix for the resin beads. One known type of matrix is based on phenol/formaldehyde condensation polymers which are cross-linked with an aldehyde, a chlorinated hydrocarbon or an epoxy compound. Other known types of matrixes are cross-linked polymers of vinylbenzyl chloride, of acrylic acid or of acrylamide or a polyacrylate. The preferred matrixes are cross-linked polystyrene or poly(alpha-methylstyrene) or crosslinked polymer of styrene or alpha-methylstyrene which is substituted at the benzene ring with Cl-6-alkyl, for example methyl, ethyl, tert. butyl, isopropyl, or a halogeno C1-6-alkyl, e.g. chloromethyl, or aminomethyl.

The cross-linking agent preferably is an alkyl acrylate or a di- or polyvinyl compound such as trivinyl cyclohexane, ethylene glycol dimethacrylate or trimethylolpropane triacrylate, most preferably divinylbenzene or trivinylbenzene. Divinylbenzene is typically copolymerised with the substituted or unsubstituted styrene or with acrylic acid.

Unless otherwise mentioned, the following description of the resin beads relates to beads which have such a preferred cross-linked styrenedivinylbenzene copolymer matrix, although the scope of the present invention is not restricted thereto.

The resin beads can have a macroporous or gel type (microporous) structure. The macroporous resin beads preferably have an average pore diameter of more than 10 nm. The microporous resin beads preferably have an average pore diameter of 0.5 to 5 nm. These resin beads may be prepared according to conventional suspension polymerisation techniques such as those taught in US patents 4,564,644, 4,297,220 and 4,382,124.

The most preferred resin beads are cross-linked spheroido gel-type copolymer beads which have a core/shell morphology. By the term "core/shell morphology" it is meant that the polymeric structure of the copolymer beads changes from the inside to the outside of the bead. Such changes in polymeric structure may be somewhat gradual yielding a bead having a gradient of polymeric structure along-the radius. Alternatively, said changes in polymeric structure may be relatively abrupt as one moves along a radius of the bead outward from the center. The effect in any case is that these gel-type resin beads have a relatively distinct core having one polymeric structure and a relatively distinct shell having another polymeric structure.The core/shell morphology of the copolymer beads is detectable using known analytical techniques such as those mentioned in European patent application 0 101 943. The core/shell copolymer beads preferably have a shell containing a lower proportion of cross-linking monomers than the core. In this way, beads of this type will have a shell which is softer (less friable and more elastic) than the core of the bead. This permits the bead to distribute energy throughout its structure when subjected to external stresses and pressures while retaining its shape and integrity. It is believed that this improves the crush strength and resistance to osmotic shock of such core/shell copolymer beads. In addition to the difference in cross-link densities of the core and shell, the polymer in the shell can advantageously have a higher molecular weight than the polymers of the core.This also can impart mechanical strength to the bead and increase its resistance to osmotic shock.

Accordingly, the breakage of the beads is reduced. The core/shell copolymer beads which are useful for preparing the resin beads of the present invention are described in detail in European patent application 0 101 943.

The resin beads of the present invention generally have an average diameter of from 0.20 to 1.50 mm, preferably of from 0.25 to 1.20 mm, more preferably of from 0.35 to 0.80 mm.

The functional groups can be directly or indirectly bound to the polymeric matrix. For example the functional groups can be bound to the polymeric matrix via alkylene groups such as C1-3-alkylene groups, preferably ethylene or methylene with methylene being the most preferred group.

Functional groups of cation exchange resins are typically -SO3Rl, -COOR1 or -P03R1R2 groups wherein R1 is a cation, preferably the proton, an alkali metal cation, such as lithium, sodium or potassium, or an alkaline earth metal ion such as barium, magnesium or calcium or a transition metal ion such as Fe2+, Ni2+, Co2+, Zn2+, Pb2+, Cu+ or Ce3+ and R2 is a C1-6-alkyl, such as a methyl, ethyl, n-propyl, isopropyl or n-butyl, a C3-6-cycloalkyl, such as cyclohexyl, aryl, such as phenyl or benzyl or has the meaning of R1.

The term "cation" as used herein includes the proton.

Functional groups of anion exchange resins typically are -NR3R4Rs X- groups wherein R3 and R4 independently in each occurrence are hydrogen or C1-6-alkyl such as hexyl, preferably C1-3-alkyl, such as methyl, ethyl or propyl, Rs has the meaning of R3 or R4 or is hydroxy-Cl-3-alkyl, such as hydroxyethylene or a mono- or di-C1,5-alkylaminoethylene group and X is an anion, preferably a halogen ion, such as chloride, bromine or iodide; or the hydroxy, nitrate or sulfate ion.

Instead of cation exchange resins having one of the above-mentioned matrices and functional groups, cation exchange resins of the following type are also useful: crosslinked polyvinylpyridines or polyvinylimidazols, which are for example crosslinked with trimethylolpropanetriacrylate or methylenebisacrylamide, such as those commercially available from the Riedel-de Haen company, crosslinked terpolymers of vinylpyridine, styrene and the crosslinking agent; these resins have to be converted into a salt form before using them for producing the resin beads of the present invention, for example by reacting them with an organic or inorganic acid whereby the nitrogen group is protonated and the resin beads are provided with exchangeable anions such as Cl-, Br-, J-, SO42-, BF4-, PO42- or CH3COO-.Useful are also quaternized polyvinylpyridine--and polyvinylimidazoletype resin beads such as poly(methylvinylpyridiniumchloride) or crosslinked quaternized poly(dimethylaminoethylmethacrylate) or poly(3acrylamido-3-methyl-butyl trimethylammonium chloride).

Resin beads having an above mentioned matrix and above mentioned functional groups are known and for example described in European patent application 0 101 943 or in "Ullmann's Enzyklopadie der Technischen Chemie", 4th Edition, Vol. 13, pages 279 et seq. These resin beads are used for preparing the resin beads of the present invention as described below.

In the functional groups of the cation exchange resin beads a portion of the protons or cations, such as the above mentioned alkali metal, alkaline earth metal or transition metal ions are exchanged with ions which have oxidative properties.

Most preferably the resin beads are contacted in their acidic form with the solution containing ions having oxidative properties, that is the exchangeable counter-ions in the resin beads are protons.

By the term "ions having oxidative properties" is meant ions which have a redox potential sufficient for enabling oxidative polymerisation of one or more aromatic compounds described below. The required redox potential naturally depends on the type of aromatic compound for which an oxidative polymerisation is desired. Useful cations which have oxidative properties are for example Fe3+, Ce4+, Cu2+, Cr6+ or Ag+.

Preferably, Fe3+ ions are exchanged with protons or the cations in the resin beads which do not have oxidative properties. Such an exchange can be carried out by contacting the resin beads with a solution containing the ions having oxidative properties. Aqueous solutions of the ions are preferred. In the practice of the present invention such solutions preferably contain from 10 ppm to 20,000 ppm, more preferably from 50 ppm to 10,000 ppm and most preferably from 100 ppm to 5,000 ppm (by weight) of the cations having oxidative properties. The preferred concentration mainly depends on the desired end-use of the resin beads to the coated according to the process of the present invention.If it is just desired to provide the cation exchange resin beads with a dark colour, it is usually sufficient to contact them with solutions containing from 50 ppm, preferably from 100 ppm to 800 ppm, preferably to 500 ppm (by weight) of the cations having oxidative properties.

If the cation exchange resin beads should be provided with anti-clumping properties as discussed above, the resin beads are usually contacted with solutions containing from 1,000 ppm, preferably from 1,500 ppm to 5,000 ppm, preferably to 4,000 ppm (by weight) of the cations having oxidative properties.

If the cation exchange properties of the resin beads are to be substantially influenced, the resin beads are typically contacted with solutions containing from 5,000 ppm, preferably from 7,500 to 20,000 ppm, preferably to 15,000 ppm (by weight) of the cations having oxidative properties.

Typically the iron ions are added to an aqueous solvent, such as water in the form of the FeC13 salt.

In order to increase the solubility of the FeC13 salt in the aqueous solvent inorganic acids can be added to the aqueous solution. Hydrogen chloride and sulfuric acid in concentrations of up to 20 weight percent, more preferably from 5 to 10 weight percent, are preferred.

The exchangeable counter-ions in the resin beads may also be alkaline metal ions, such as lithium, sodium or potassium or alkaline earth metal ions, such as magnesium or calcium. Instead of FeC13 other iron salts may be dissolved in an aqueous solvent, for example Fe(ClO4)3 or Fe2(SO4)3. Cerium salts, such as Ce(SO4)2, copper salts, such as CuC12, silver salts, such as AgNO3, chromium salts, such as Crow, molybdenium salts such as H3PO4x12MoO3, tungsten salts such as H3P04x12W03 or other salts having oxidative properties are also useful. FeC13 is the most useful salt providing cations having oxidative properties.

The residence time of the cation exchange resin beads in the solution of cations having oxidative properties usually is from 0.1 to 5 hours, preferably from 0.5 to 3 hours.

In the case of anion exchange resin beads exchangeable anionic counter-ions b), such as halogen ions, preferably bromide or iodide, most preferably chloride or the hydroxy, nitrate or sulfate ion are partially exchanged with anions having oxidative properties. Preferably, anions of the type S2082-, Cr2O72-, MnO4~, [Fe(CN)]3 or [Ce(NO)j2 ]2- are used as anions having oxidative properties. The resin beads are contacted with a solution containing these anions.

Preferably, the resin beads are added to aqueous solutions to which salts having the above mentioned ions have been added, for example to aqueous solutions of an alkali metal or ammonium salt having S2082anions, such as Na2S2Og, K2S2O8, (NH4)2S2Og or other useful salts, such as K3Fe(CN)6 or (NH4)2Ce(N03)6. The resin beads are preferably contacted with aqueous solutions containing such salts in an amount of from 0.5 to 25 weight percent, more preferably from 1 to 10 weight percent.

Typically, the ion exchange in the functional groups of the cation or anion exchange resin beads is carried out at a temperature between 10 C and 60 C, preferably at about ambient temperature.

Resin beads which have been subjected to the above mentioned treatment have functional groups consisting of a) ionic groups being bound to the polymeric matrix and b) exchangeable counter-ions which have oxidative properties. These resin beads are contacted with an oxidatively polymerisable aromatic compound. An oxidative polymerisation of the aromatic compounds takes place whereby the counter-ions having oxidative properties are partially or completely reduced. The resin beads are coated with the produced polymer. The terms "coated" and "coating" as used herein do not mean that the entire amount of the polymer is located at the surface of the resin beads. A portion of the polymer can also be located in the cores of the resin beads.

Monomeric compounds which are useful for producing the polymer beads of the present invention are mainly phenolic, furane, aniline, pyrrole and/or thiophene compounds, such as substituted or unsubstituted pyrrole, a substituted or unsubstituted thiophene or a substituted or unsubstituted aniline.

Preferred pyrroles which can be polymerised according to oxidative polymerisation are represented by formula I

wherein R16 is alkyl, cycloalkyl, aryl, aralkyl, or alkaryl, which groups are optionally substituted by -COR20, -COOR20, -S02R20, -SO3R20, -PO3R20R21, -P02R20, -NR20R21, -OR20, -SR20, -CN or -SiR20R23R24, or R16 is hydrogen, -CN, -SO2R20, -So3R20, -COR20, -P02R20 or -Si(R22)3; R20 and R21 independently represent hydrogen, alkyl, aryl or aralkyl; R22, R23 and R24 independently represent alkyl or phenyl; R17 and R18 independently represent hydrogen, alkyl, cycloalkyl, aryl, aralkyl, -C0R19, -CN or halogen;; R19 is hydrogen, alkyl or aryl.

Among the alkyl radicals, C1-Cpg-alkyl are preferred, such as methyl, ethyl, propyl, butyl, cetyl, lauryl or staeryl groups. C1-Cs-alkyl is more preferred.

Methyl is the most preferred alkyl radical.

Among the cycloalkyl radicals, Cs-C7-cycloalkyl are preferred, that is cyclopentyl, cyclohexyl or cycloheptyl, of which cyclohexyl is the most preferred group.

Preferred halogen radicals are bromine and chlorine.

Aryl radicals preferably represent phenyl or naphthyl, most preferably phenyl.

Aralkyl preferably represents a C7-Cl4-aralkyl, most preferably benzyl.

Substituted groups are preferably mono- or disubstituted, most preferably mono-substituted.

Pyrroles which are substituted at the aromatic ring are preferably substituted in the 3- and/or 4-position.

Preferred pyrroles are the unsubstituted pyrrole, the N-alkylpyrroles, in particular the N-methylpyrrole, or the N-arylpyrroles, in particular the N-phenylpyrrole as well as the pyrroles which are substituted at the aromatic ring with one or two Cl-C4-alkyl groups, preferably methyl groups or one or two halogen radicals, preferably bromine or chlorine.

The optionally substituted pyrroles can be copolymerised with other heteroaromatic compounds, preferably with furane, thiophene, 2-bromo-thiophene, thiazole, oxazole, thiadiazole, imidazole, pyridine, 3,5-dimethylpyridine, pyrazine, pyridazine, 3,5-dimethylpyrazine, carbazole or phenothiazine.

The most preferred pyrrole copolymers are produced on the resin beads from unsubstituted pyrrole and N-methylpyrrole and copolymers produced from unsubstituted pyrrole or N-methylpyrrole and furane or thiophene. These pyrrole copolymers preferably contain from 0.1 to 10 mol percent of the aforementioned other heteroaromatic compounds, based on the amount of pyrrole. The most preferred polypyrrole is a homopolymer of unsubstituted pyrrole. The expression polypyrrole used hereafter means homo- or copolymers of pyrrole and/or substituted pyrrole or copolymers of pyrrole and heteroaromatic compounds having rings of 5 or 6 members.

It is also useful to coat the resin beads with polyaniline according to the process of the present invention.

"Polyaniline" includes homo- or copolymers of aniline and/or substituted aniline or copolymers of aniline and/or substituted aniline with heteroaromatic compounds having five or six members in the aromatic ring. Preferred monomers for producing a polyaniline are unsubstituted aniline, N-methylaniline, 2-methylaniline, and N-phenyl-1,4-diaminobenzene. A homopolymer of unsubstituted aniline is preferred.

It is evident that different aromatic compounds require different minimal redox potential for their oxidative polymerisation. Due to their high redox potential, cation exchange resin beads preferably contain Fe3+ ions and anion exchange resin beads preferably contain S2082' groups. Accordingly, a wide variety of aromatic compounds can be subjected to oxidative polymerisation in their presence. In the following description Fe3+ ions are used as representatives for cations having oxidative properties and S2082 ions are used as representatives for anions having oxidative properties although the scope of the invention is not limited thereto.

In the practice of producing the resin beads of the present invention, resin beads having Fe3+ ions or S2082' ions are contacted with a solution containing one or more of the above mentioned types of aromatic compounds. A preferred solvent for the aromatic compounds is water which is optionally mixed with water-miscible organic solvents, such as methanol, ethanol, acetonitrile or propylene carbonate. A known emulsifier can be added in order to increase the solubility of the heteroaromatic compounds in water.

The useful concentration of the aromatic compound in the solvent mainly depends on the intended end-use of the resin beads to be coated according to the process of the present invention and on the amount of Fe3+ ions in the cation exchange resin beads or of S2082- groups in the anion exchange resin beads. The amount of Fe3+ ions or S2082- groups in the resin beads can be influenced as described before and is a limiting factor for the subsequent polymerisation of pyrrole to polypyrrole.When the ion exchange capacities of resin beads should not be substantially influenced and the main aim of the coating is to provide the resins with a dark colour, an above mentioned solvent contains the aromatic compound generally at a concentration of from 10 ppm to 8,000 ppm, preferably from 50 to 5,000 ppm and more preferably from 100 to 1,000 ppm by weight.

When it is intended to make use of the anti-clumping properties of the cation exchange resin beads bf the present invention, or when cation exchange resin beads of the present invention should be used for at least partial separation of monovalent and multivalent cations the concentration of the aromatic compound in the solvent is usually from 100 to 20,000 ppm, preferably from 1,000 to 10,000 ppm, more preferably from 5,000 to 8,000 ppm by weight.

The oxidative polymerisation of the aromatic compound in the presence of the resin beads having Fe3+ ions or S2082 groups takes place within a relatively short time by simply contacting the resin beads with the solution of the aromatic compound. Generally the oxidative polymerisation takes less than one hour,in most of the cases less than 30 minutes and in many cases the polymerisation is completed within 10 to 15 minutes. The proceeding of the reaction is visible since the resin beads change their colour. Usually the reaction temperature is from about 0 C to 600C, preferably from 50C to 400C, most preferably about ambient temperature.

Even if a solution containing ions having oxidative properties, such as Fe3+ ions, in a concentration as low as 100 ppm by weight is used in the first step of the process of the present invention and a solution containing an aromatic compound, such as pyrrole, in a concentration as low as 100 ppm by weight is used in the second step of the process of the present invention, the resin beads obtain a dark colour within 10 to 15 minutes already. Furthermore, it is surprising that the beads which have been provided with a colour in such a way substantially retain their mechanical and physical properties.Since either cation or anion exchange resin beads are selectively provided with a colour, depending on the employed type of ions which have oxidative properties, the process of the present invention is very useful for detecting traces of cation exchange resin beads in anion exchange resin beads and vice-versa.

When using higher concentrations of cations having oxidative properties and of aromatic compounds in the process of the present invention, for example at least 5,000 weight ppm Fe3+ ions in the solution employed in the first step and at least 8,000 weight ppm pyrrole in the solution employed in the second step of the process of the present invention, the produced cation exchange resins of the present invention are useful for at least partial separation of monovalent from multivalent ions. The resin beads have a preference for monovalent ions. Accordingly, when contacting such cationic resin beads with a solution containing monovalent and multivalent ions, the monovalent ions are removed from the solution to a greater extent than the multivalent ions.The cationic resin beads of the present invention mainly have a preference for H+ or alkaline metal ions, such as lithium, sodium, potassium, rubidium or caesium ions, over alkaline earth metal ions, such as beryllium, magnesium, calcium, strontium, barium or radium ions or over transition metal ions, such as cobalt, nickel, Cu2+, zinc, Hg2+, lead, ruthenium, rhodium, palladium, platinum, titanium or lanthanum ions. For example, the resin beads of the present invention may be useful for at least partial separation of radio-active ions having different valencies, such as Cs+/Ra2+ or for other ions having different valencies, such as Cs+/Cu2+ or H+/Cu2+.

For carrying out such a separation, cation exchange resin beads of the present invention can be contacted with aqueous solutions containing the mentioned cations in a known way.

The present invention is further illustrated by the following examples which should not be construed to limit the scope of the invention. All parts and percentages are by weight unless otherwise mentioned.

The hydrogen capacity of the cation exchange resin beads of the present invention is determined by converting the resin beads completely to their hydrogen form with hydrochloric acid, liberating the acid from the resin beads with sodium chloride and titrating the liberated acid with sodium hydroxide. Phenolphthaleine is used as an indicator. The total hydrogen wet volume capacity of the resin beads is expressed in milli equivalents per ml of wet resin beads in their hydrogen form. It can also be expressed in milli equivalent per ml of wet resin beads in their sodium form. The sodium form of the resin beads can be easily prepared from the hydrogen form by exhaustive treatment with a sodium chloride solution.

The total copper wet volume capacity of the sodium form of the cation exchange resin beads is determined by contacting the resin beads with a solution of 60 g of CuSO4 5H2O and 120 ml of concentrated ammonium hydroxide in 600 ml of water, washing the beads with water to remove excess zipper and then with 2N sulphuric acid to remove the copper ions bound to the functional groups. The amount of copper removed from the beads with 2N sulfuric acid is determined using a potassium iodine/sodium thiosulfate oxidation/reduction titration.

The total copper wet volume capacity is expressed in milli equivalent per ml of wet resin beads. By drying a wet resin sample having a determined volume and determining its weight, the total copper dry weight capacity can be calculated.

The chloride wet volume capacity of the anion exchange resin beads of the present invention is determined as follows: The resin is exhaustively treated with 5 weight percent hydochloric acid, washed with water until the effluent is chloride free, and a determined volume of the resin in the chloride form is quantitatively transferred in a flask, digested with a 20 percent aqueous solution of sulfuric acid of 80"C for five minutes and then titrated with AgN03 according to known methods.

The water retention capacity of the resin beads of the present invention is determined from the loss of weight of the resin beads which have been pretreated as described below. The weight loss is measured on a moisture balance at 80"C. The percent water retention capacity is defined as (weight loss)/(wet resin weight) x 100. In the pretreatment step, the cationic resin beads have been converted to the hydrogen form, the anionic resin beads to the chloride form, by treatment with 5 weight percent hydrochloric acid; then the resin beads have been washed with water until the pH of the effluent was above 3.5 and then the resin beads have been centrifuged at 2000 rpm for five minutes.

In Example 1 to 3 and 6 to 10 cationic gel type (microporous) resin beads are used having a polymeric, cross-linked matrix of styrene/divinylbenzene (DVB) and sulfonate groups. Their dry weight capacity is 5.13 meq/g. The resin beads are commercially available as DOWEX-HGR-W2 ion exchange resin from The Dow Chemical Company.

InExample 4 cationic gel type (microporous) resin beads are used which have a polymeric, crosslinked matrix of acrylic acid/DVB. Their total hydrogen wet volume capacity is 4.2 meq/ml. The resin beads are commercially available as DOWEX CCR-2 ion exchange resin from The Dow Chemical Company.

In Example 5 cat ionic macroporous resin beads are used which have a matrix of polymeric, cross-linked styrene/DVB and sulfonate groups. Their wet volume capacity (H-form) is 1.7 meq/ml. The resin beads are commercially available as Dowex MSC-1 ion exchange resins from The Dow Chemical Company.

In the Examples 1 to 11 and 13 the measured ion exchange capacities of the coated resin beads of the present invention are compared with the ion exchange capacities which are measured in parallel trials for the known uncoated resin beads.

Example 1 50 ml of Dowex-HGR-W2 ion exchange resin beads are stirred in a solution of 5 mg of FeC13 in 50 ml of water (100 ppm) for 2 hours. The solution is sucked off with a fritted tube and the resin beads are thoroughly washed with 400 ml of water. After removal of the wash water, the resin beads are stirred in 250 ml of water containing 100 ppm pyrrole. After about 10 - 15 minutes the colour of the beads changes from transparent yellow-brown to green-brown. The colour still remains green-brown after the resin beads have been stirred for 2 hours in the aqueous solution of pyrrole. The beads are thoroughly washed twice with 400 ml of water. The resin beads are regenerated by washing the non-reacted iron ions with 100 ml of an 8 percent aqueous HC1 solution.

The total copper wet volume capacity of the resin beads is 1.90 meq/ml and the total wet volume capacity (Na form) is 2.20 meq/ml.

The total copper wet volume capacity of the coated resin beads of Example 1 is 97 percent of the total copper wet volume capacity of the uncoated Dowex HGR-W2 ion exchange resin beads.

The total wet volume capacity (Na form) of the coated resin beads of Example 1 is also 97 percent of the total wet volume capacity of the uncoated Dowex HGR-W2 ion exchange resin beads.

Further physical properties of A) the cation exchange resin beads which have been coated with polypyrrole as described in Example 1 above and of B) uncoated Dowex-HGR-W2 cation exchange resin beads are listed below.

The Table illustrates that the resin beads substantially retain their hydrogen capacity and their crush strength after being coated according to the process of Example 1.

Coated resin Uncoated beads A) resin beads B) Hydrogen wet volume capacity 2.08 meq/ml 2.12 meq/ml Hydrogen dry weight capacity 4.97 meq/g 5.13 meq/g Water retention capacity 39.0 /0 47.3% Density 0.732 glml 0.689 glml Spericity 1) 97.5% 99% Crush 2) 650.8 g 672.8 g > 200g3) 100% 100% Colour dark brown-black amber 1) percentage of uncrushed resin beads 2) "Crush" means the average weight which is required to crush one single bead.The crush strength of the washed resin beads in their H±form has been measured using a commercially available crush tester (sold by Erichson).

3) " > 200g" means percentage of beads which withstand a weight of 200 g.

Example 2a 50 ml of Dowex-HGR-W2 ion exchange resin beads are stirred in a solution of 50 mg of FeC13 in 50 ml of water (1,000 ppm) for 2 hours. The resin beads are then treated as in Example 1. When the resin beads are stirred in 250 ml of water containing 100 ppm pyrrole for 3 to 5 minutes, the resin beads obtain a dark, green colour. After stirring for 2 hours, their colour changes to green-black. The resin beads are washed with water and treated with an 8 percent aqueous HC1 solution as described in Example 1.

Their total copper wet volume capacity is 1.86 meq/ml. This corresponds to 95 percent of the total copper wet volume capacity of the uncoated Dowex-HGR-W2 ion exchange resin beads.

Example 2b 50 ml of Dowex-HGR-W2 ion exchange resin beads are stirred in a solution of 500 mg of FeC13 in 50 ml of water (10,000 ppm) for 2 hours. The solution is sucked off with a fritted tube and the resin beads are thoroughly washed with 400 ml of water.

In Table 1 the amounts of iron ions which are absorbed by the resin beads in Examples 1, 2a and 2b are listed.

The amount of absorbed Fe3+ ions is measured as follows: Between 6.2 and 7.1 ml of resin beads are used of which the volume is exactly measured. The Fe3+ ions are regenerated by contacting the beads with 150 ml of a 16 percent aqueous HC1 solution. The contact time is 2 hours. The solution is diluted with water to an exact volume of 200 ml. The content of Fe3+ ions is measured by atomic adsorption using standards.

Amount Amount FeCl3 of Fe3+ of Fe3+ Absorpion Example concen- in absorbed Absorpion tration 50 ml by 50 ml of Fe3+ tration 50 ml by 50 ml ions solution resin 1 100 ppm 1.7 mg 1.6 mg 94 percent 2a 1,000 ppm 17.2 mg 15.7 mg 92 percent 2b 10,000 ppm 172.1 mg 159 mg 92 percent Table 1 Example 3 50 ml of Dowex-HGR-W2 ion exchange resin beads are stirred in a solution of 250 mg of FeC13 in 50 ml of water (5,000 ppm FeC13) for 2 hours. After washing with 400 ml of water as described in Example 1, the resin beads are stirred in 250 ml of water containing 8,000 ppm pyrrole. The resin beads become deep black within 30 seconds. After the resin beads have been washed with water and regenerated with HC1 as described in Example 1, its total copper wet volume capacity is 1.65 meq/ml which corresponds to 84 percent of the total copper wet volume capacity of the uncoated Dowex HRG-W2 ion exchange resin beads.

Example 4 The procedure is the same as in Example 1, however instead of Dowex-HGR-W2 ion exchange resin beads, Dowex CCR-2 ion exchange resin beads are used.

The resin beads are stirred in an aqueous solution containing 1,000 ppm FeC13, washed with water as described in Example 1 and stirred in 250 ml of an aqueous solution containing 1,000 ppm pyrrole. The resin beads become green-brown after about 15 minutes and brown-black after 2 hours. The resin beads are thoroughly washed twice with 400 ml of water and then treated with 100 ml of an 8 percent aqueous HC1 solution. The total copper wet volume of the coated resin beads is 3.8 meq/ml which corresponds to 95 percent of the total copper wet volume capacity of the uncoated Dowex CCR-2 ion exchange resin beads.

Example 5 Instead of Dowex-HGR-W2 ion exchange resin beads, Dowex MSC-1 ion exchange resin beads are used.

50 ml of the wet resin beads are stirred in an aqueous solution containing 1,000 ppm FeC13 for 2 hours.

Afterwards the solution is sucked off and the resin beads are thoroughly washed with 400 ml of water for 0.5 hours. The resin beads are then stirred in an aqueous solution containing 1,000 ppm pyrrole. A first colour change is observed after 3 minutes. After 2 hours the resin beads become grey-black.

The total copper wet volume capacity is 1.36 meq/ml which corresponds to 92 percent of the total copper wet volume capacity of the uncoated Dowex MSC-1 ion exchange resin beads.

Example 6 50 ml of wet Dowex-HGR-W2 ion exchange resin beads are stirred in an aqueous solution containing 1i000 ppm of CuC12 for 2 hours. Afterwards the solution is removed from the beads. The resin beads are washed with water and are then stirred in 250 ml of an aqueous solution containing 1,000 ppm pyrrole. After 2 hours the resin beads have a deep, brown colour. After the resin beads have been washed and regenerated with an 8 percent aqueous solution of HCl, the beads are brought into their sodium form.

The total copper wet volume capacity is 1.76 meq/ml which corresponds to 96 percent of the total copper wet volume capacity of the uncoated Dowex-HGR-W2 ion exchange resin beads.

Example 7 100 mg of FeC13 are dissolved in 100 ml of water (1,000 ppm FeCl3). 100 ml of wet Dowex-HGR-W2 ion exchange resin beads are added and the mixture is stirred for 2 hours. The liquid is sucked off and the resin beads are then stirred in 800 ml of water for 0.5 hours. After having removed the wash water, the resin beads are stirred in 500 ml of water containing 8,000 ppm pyrrole. The colour of the beads changes from yellow-brown to green after 30 seconds and the resin beads become deep black after about one minute. 2 hours later, the resin beads are thoroughly washed with 1,600 ml of water and treated with 200 ml of an 8 percent aqueous solution of HC1 for 8 hours.

The total copper wet volume capacity of the resin beads is 1.64 meq/ml which corresponds to 91 percent of the total copper wet volume capacity of the uncoated Dowex-HGR-W2 ion exchange resin beads.

In order to evaluate the anti-clumping properties of the coated cation exchange resin beads of the present invention compared with known, uncoated cation exchange resin beads, the cation exchange resin beads are mixed with anion exchange resin beads which are commercially available as Dowex-SBR ion exchange resin beads. These anion exchange resin beads are geltype polystyrene resin beads, crosslinked with DVB.

They contain 1.52 meq/ml active trimethylammonium chloride groups.

40 ml of the cation exchange resin beads and 40 ml of the anion exchange resin beads are stirred together in 100 ml of water for 10 minutes. After the beads have settled, the total volume of the beads is measured.

When stirring 40 ml of the coated cation exchange resin beads produced according to Example 7 together with 40 ml of Dowex-SBR anion exchange resin beads, the total volume of the beads is 80 ml.

As a Comparative Example, when stirring 40 ml of the uncoated Dowex-HGR-W2 cation exchange resin beads together with 40 ml of Dowex-SBR anion exchange resin beads, the total volume of the beads is 94 ml.

When stirring 40 ml of the coated cation exchange resin beads produced according to Example 9 (see below, 20,000 ppm FeC13, 8,000 ppm pyrrole) together with 40 ml of Dowex-SBR anion exchange resin beads, the total volume of the beads is 80 ml.

This comparison illustrates the anti-clumping effect of the coated resin beads of the present invention.

In order to maximise the anti-clumping effect of the coated cation exchange resin beads of the present invention it is advisable to use a higher concentration of pyrrole than what is just necessary for providing the resin beads with a dark colour.

Preferred concentrations of pyrrole are stated above.

When stirring 40 ml of the coated cation exchange resin beads produced according to Example 2a (1,000 ppm FeCl3, 100 ppm pyrrole) together with 40 ml of Dowex-SBR anion exchange resin beads, the total volume of the beads is 92 ml.

The following Comparative Example illustrates that the anti-clumping properties of the cation exchange resin beads are highly unexpected and could not be predicted by the skilled artisan: When stirring 40 ml of the uncoated Dowex-HGR W2 ion exchange resin beads together with 40 ml of coated Dowex-SBR anion exchange resin beads which have been produced according to Example 13 (2% Na2S208 5000 ppm pyrrole), the total volume of the beads is 145 ml (the total volume of the uncoated cation and anion exchange resin beads is 94 ml, see above). Accordingly, no anti-clumping effect is reached when mixing the coated anion exchange resin beads produced according to Example 13 with uncoated Dowex-HGR-W2 cation exchange resin beads.

Example 8 Deep black polypyrrole coated Dowex-HGR-W2 cation exchange resin beads are produced as described in Example 7, but using an aqueous solution containing 10,000 ppm FeC13 and an aqueous solution containing 8,000 ppm pyrrole.

Total copper wet volume capacity: 1.08 meq/ml which corresponds to 64 percent of the non-coated Dowex-HGR-W2 ion exchange resin beads, (1.7 meq/ml).

Wet volume capacity (Na form): 2.13 meq/ml which corresponds to 92 percent of the wet volume capacity (Na form) of the non-coated Dowex-HGR-W2 ion exchange resin beads (2.31 meq/ml).

Hydrogen capacity: 1.97 meq/ml which corresponds to 91 percent of the hydrogen capacity of the non-coated Dowex-HGR-W2 ion exchange resin beads (2.16 meq/ml).

Example 9 Deep black polypyrrole coated Dowex-HGR-W2 cation exchange resin beads are produced according to the procedure described in Examples 1 and 7, however, using an aqueous solution containing 20,000 ppm FeC13 and an aqueous solution containing 8,000 ppm pyrrole.

Total copper wet volume capacity: 0.4 meq/ml, which corresponds to 18 percent of the total copper wet volume capacity of the non-coated Dowex-HGR-W2 ion exchange resin beads (2.2 meq/ml).

Wet volume capacity (Na-form): 1.84 meq/ml which corresponds to 81 percent of the wet volume capacity (Na-form) of the non-coated Dowex-HGR-W2 ion exchange resin beads (2.27 meq/ml).

Hydrogen capacity: 1.76 meq/ml which corresponds to 84 percent of the hydrogen capacity of the non-coated Dowex-HGR-W2 ion exchange resin beads (2.10 meq/ml).

In Table 2 the total capacities of the resin beads produced according to Examples 3, 7, 8 and 9 for some cations are listed. In all Examples 3, 7, 8 and 9 an aqueous solution containing 8,000 ppm pyrrole is used). The FeC13 concentration in the aqueous solution varies from 1,000 ppm to 20,000 ppm.

The total capacities are given as percentages of the corresponding total capacities of the non-coated Dowex-HGR-W2 cation exchange resin beads. In each measurement the ion exchange capacities of a sample of the non-coated resin beads are measured and used as a standard.

Wet Volume Wet Volume FeCl3 Caesium Capacity Cu2+ Capacity Capacity Example concen- Capacity Capacity Capacity (%) (%) tration (%) (%) (%) (H±form) (Na-form) 7 1,000 ppm 97 96 - - 91 3 5,000 ppm - - 93 88 84 8 10,000 ppm 92 91 - - 63 9 20,000 pm 84 81 88 76 18

Table 2 Table 2 illustrates that the ion exchange capacities of the resin beads of the present invention decrease with an increasing FeC13 concentration. An increased FeC13 concentration evidently increases the level of the pyrrole coating. The comparison between the hydrogen capacity and the copper capacity illustrates that the decrease of ion exchange capacity depends on the type of cations, mainly on their charge.

The decrease of the ion exchange capacity is more significant for multivalent cations than for monovalent cations.

Ion exchange capacities of the resin beads produced according to Examples 3 and 9 are measured for other ions as follows: About 5 ml of the resin beads of which the volume is exactly measured are brought in their sodium form by contacting them with 150 ml of a 5 weight percent NaOH solution. The resin beads are washed with 60 ml of distilled water until neutral. The washing step takes 30 minutes.

Different samples of the resin beads are contacted with 300 ml of various solutions containing A) 0.05 M CsCl and 0.05 M CuSO4 B) 0.25 M CsCl and 0.25 M CuSO4 C) 0.05 M CsCl and 0.05 M BaC12 and D) 0.05 M CaC12 and 0.05 M CuSO4 (Comparison) for 2 hours. The resin beads are then regenerated with 150 ml of 2N H2SO4, the effluent containing the cations is diluted with distilled water to an exact volume of 200 ml and the metal concentrations are measured by atomic absorption in ppm.

The dynamic cation exchange capacities in meq/ml are calculated therefrom.

Solution A Solution B Solution C Solution D Capacity meq/ml Capacity meq/ml Capacity meq/ml Capacity meq/ml Sample Cs+ Cu+ Cs+ Cu+ Cs+ Ba+ Ca+ Cu2+ Dowex HGR-W2 0.35 0.20 0.50 0.34 0.36 0.22 0.22 0.16 ion (1160 ppm) (640 ppm) (1670 ppm) (1090 ppm) exchange resin Produced according 0.34 0.20 0.54 0.32 0.36 0.22 0.21 0.15 Example 3 (1160 ppm) (640 ppm) (1820 ppm) (1040 ppm) Produced according to 0.46 0.14 0.73 0.21 0.38 0.14 0.20 0.13 Example 9 (1520 ppm) (460 ppm) (2420 ppm) (660 ppm) Table 3 As is evident from Table 3, the caesium capacity of the ion exchange resin beads increases when higher concentrations of cations having oxidative properties, such as Fe3+ ions are used for preparing the resins. The capacity for divalent ions, such as Cu2+, Ba2+ or Ca2+ decreases with increasing Fe3+ concentration.

The ability of selectively influencing the cation exchange capacities of the ion resin beads of the present invention renders them useful for many applications.

Pyrrole Example concentration Copper capacity 2) (ppm) (%) 2a 100 95 10 1) 1,000 93 11 1) 5,000 91.6 7 7 8,000 91 Table 4 1) The coated resin beads of Examples 10 and 11 are produced in the same way as in Example 2a, however, in step 2) the aqueous solution contains 1,000 ppm pyrrole in Example 10 and 5,000 ppm pyrrole in Example 11 respectively. The FeC13 concentration in water is 1,000 ppm in Examples 2a, 10, 11 and 7.

2) The total copper wet volume capacity is expressed as percentage of the total copper wet volume capacity of non-coated Dowex-HGR-W2 ion exchange resin beads.

Example 12 200 ml of Dowex-HGR-W2 cation exchange resin beads are brought into their sodium form by stirring them for 4 hours in 1,200 ml of 8 percent aqueous NaOH.

The resin beads are separated from the liquid by filtration and are washed with 1 1 of water. Then the resin beads are stirred in 1 1 of water for 30 minutes.

The resin beads are separated from the liquid by filtration and are washed neutral with 100 ml of water at a pH of 7.5.

100 ml of the resin beads thus converted into their sodium form are stirred in a solution of 100 mg of FeC13 in 100 ml of water for 2 hours. The solution is sucked off and the resin beads are stirred twice in 400 ml of water for 30 minutes. Then the resin beads are separated from the liquid by filtration and stirred in a solution of 500 ml of water containing 8,000 ppm pyrrole for 2 hours. The resin beads become black after a few seconds. The resin beads are washed twice with 800 ml of water under stirring for an hour. Then they are stirred in 300 ml of an aqueous solution of 8 percent HC1 and additionally washed with 800 ml of water.

The total copper wet volume capacity of the resin beads is 1.67 meq/ml.

Example 13 50 ml of anion exchange resin beads which have 1.54 meq/ml active trimethylammoniumchloride groups, a dry weight chloride capacity of 4.19 meq/g and a polymeric cross-linked styrene/DVB matrix are stirred in a solution of 1 g of Na2S208 in 50 ml of water for 2 hours. Then the resin beads are separated from the liquid by filtration and washed in 200 ml of water for 30 minutes while stirring. The resin beads are then stirred in 200 ml of an aqueous solution containing 5,000 ppm pyrrole. After 30 minutes the colour of the beads turns grey, after about 2 hours the colour changes to grey-green. The resin beads are stirred twice in 400 ml of water. Then the resin beads are treated with 500 ml of 3 percent aqueous HCl and washed again with 500 ml of water.

Chloride wet volume capacity: 1.53 meq/ml (versus 1.54 meq/ml for the non-coated resin beads).

Chloride dry weight capacity: 4.18 meq/g (versus 4.19 meq/g for the non-coated resin beads).

Water retention capacity: 43.8 percent (versus 43.9 percent for the non-coated resin beads).

Density: 0.647 g/ml (versus 0.657 g/ml for the non-coated resin beads).

Colour: grey-green (the colour of the noncoated resin beads is white-yellow).

Example 14 Ion exchange resin beads are coated with polypyrrole as described in Example 13, but 50 ml of the anion exchange resin beads are stirred for 2 hours in a more concentrated solution of sodium peroxodisulfate (10 g in 50 ml of water). After having treated the resin beads with a solution containing 5,000 ppm pyrrole the colour of the resin beads turns grey-green after 3 minutes, dark-green after 5 minutes and finally black after about 8 minutes. The resin beads are washed and treated with aqueous HC1 as described in Example 13.

Chloride wet volume capacity: 1.48 meq/ml Chloride dry weight capacity: 4.05 meq/g Water retention capacity: 42.7 percent Density: 0.639 g/ml.

Example 15 Ion exchange resin beads are coated with polypyrrole as described in Example 13, but 50 ml of the anion exchange resin beads are stirred for 2 hours in a more concentrated solution of sodium peroxodisulfate (5 g in 50 ml of water). After having treated the resin beads with a solution containing 5,000 ppm pyrrole the colour of the resin beads turns grey-green after 3 minutes and finally black after about 19 minutes. The resin beads are washed and treated with aqueous HC1 as described in Example 13.

Chloride dry weight capacity: 4.06 meq/g Water retention capacity: 42.5 percent.

Example 16 50 ml of the anion exchange resin beads described in Example 13 are stirred for 2 hours in a solution of 1 g Na2S208 in 50 ml of water. The resin beads are washed with 200 ml of distilled water under stirring for 30 minutes and are then stirred in 200 ml of an aqueous solution containing 5,000 ppm aniline.

The resin beads change their colour from amber to orange within 5 minutes, become brown after about 20 minutes and are deep black after about 1 hour. The resin beads are washed with water, HC1 and again with water as described in Examples 13.

Chloride wet volume capacity: 1.48 meq/ml Chloride dry weight capacity: 4.09 meq/g Water retention capacity: 44 percent Density: 0.643 g/ml.

Claims (11)

1. Resin beads comprising a polymeric matrix and having a coating produced by oxidative polymerisation of at least one aromatic compound wherein the polymeric matrix comprises functional groups consisting of a) ionic groups bound to the polymeric matrix and b) exchangeable counter-ions, wherein the oxidative polymerisation of the said at least one aromatic compound has been carried out by the reduction of at least some of the said counter-ions.

2. The resin beads of Claim 1, characterised in that the coating is an oxidatively produced homo- or copolymer of substituted or unsubstituted pyrrole, substituted or unsubstituted thiophene and/or substituted or unsubstituted aniline.

3. The resin beads of Claim 1 or 2, characterised in that the ionic groups a) are anionic groups and the exchangeable counter-ions b) are cat ions.

4. The resin beads of Claim 3, characterised in that the anionic groups a) are a -S03-, -COO-, -PO32 or -P03R2 group wherein R2 is a C1-6-alkylr a C3,6-cyclo- alkyl, aryl or a cation and that the exchangeable counter-ions which are reduced during the oxidative polymerisation are Fe3+, Ce4+, Cu2+, Cr6+ or Ag+.

5. The resin beads of Claim 1 or 2, characterised in that the ionic groups a) are cationic groups and the exchangeable counter-ions b) are anions.

6. The resin beads of Claim 5, characterised in that the cationic groups a) are groups of the formula -NR3R4Rs groups wherein R3 and R4 independently in each occurrence are hydrogen or a C1-6-alkyl group and R5 is hydrogen, a C1-6-alkyl group, a hydroxy-C13-alkyl group, a C1-6-alkylaminoethylene group or a di-C16-alkylaminoethylene group and that the exchangeable counter-ions which are reduced during the oxidative polymerisation are S2082-, (Fe(CN)6)3, (Ce(N03)6)2~, MnOg- or Cr2O72-.

7. A process for producing the resin beads of any of Claims 1 to 6, characterised in that resin beads having a polymeric matrix and functional groups consisting of a) ionic groups being bound to the polymeric matrix and b) exchangeable counter-ions having oxidative properties are contacted with an oxidatively polymerisable aromatic compound.

8. A process as claimed in Claim 7, including the step of contacting a solution containing ions having oxidative properties with resin beads containing exchangeable counter-ions to effect a partial exchange of the counter-ions before contacting the beads with the oxidatively polymerisable aromatic compound.

9. The use of the resin beads of Claim 3 or Claim 4 for at least partially separating monovalent and polyvalent cations.

10. A container wherein A) resin beads having a polymeric matrix and functional groups consisting of cationic groups being bound to the polymeric matrix and exchangeable anions and B) the resin beads of Claim 3 or 4 are arranged in a mixed or layered fashion.

11. A method of separating different types of resin beads, a portion thereof having exchangeable cations and a portion thereof having exchangeable anions by 1) selectively exchanging either said cations or said anions partially with ions having oxidative properties and 2) effecting oxidative polymerisation of an aromatic compound in the presence of the resin beads whereby the beads containing ions having oxidative properties are selectively coated with the polymerised aromatic compound and change their colour and 3) separating the coated and uncoated resin beads according to their colours.