Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J39/00—Cation exchange; Use of material as cation exchangers; Treatment of material for improving the cation exchange properties
  • B01J39/08—Use of material as cation exchangers; Treatment of material for improving the cation exchange properties
  • B01J39/16—Organic material
  • B01J39/18—Macromolecular compounds
  • B01J39/20—Macromolecular compounds obtained by reactions only involving unsaturated carbon-to-carbon bonds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
  • B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
  • B01J31/06—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides containing polymers
  • B01J31/08—Ion-exchange resins
  • B01J31/10—Ion-exchange resins sulfonated
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J39/00—Cation exchange; Use of material as cation exchangers; Treatment of material for improving the cation exchange properties
  • B01J39/26—Cation exchangers for chromatographic processes
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C37/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring
  • C07C37/11—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring by reactions increasing the number of carbon atoms
  • C07C37/20—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring by reactions increasing the number of carbon atoms using aldehydes or ketones
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F8/00—Chemical modification by after-treatment
  • C08F8/34—Introducing sulfur atoms or sulfur-containing groups
  • C08F8/36—Sulfonation; Sulfation
• • C—CHEMISTRY; METALLURGY
  • C13—SUGAR INDUSTRY
  • C13B—PRODUCTION OF SUCROSE; APPARATUS SPECIALLY ADAPTED THEREFOR
  • C13B20/00—Purification of sugar juices
  • C13B20/14—Purification of sugar juices using ion-exchange materials
  • C13B20/148—Purification of sugar juices using ion-exchange materials for fractionating, adsorption or ion exclusion processes combined with elution or desorption of a sugar fraction
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/42—Treatment of water, waste water, or sewage by ion-exchange
  • C02F2001/425—Treatment of water, waste water, or sewage by ion-exchange using cation exchangers

Definitions

• the invention relates to a process for producing strongly acidic cation exchangers with high mechanical, osmotic and oxidation stability by sulfonating bead polymers formed from one or more vinylaromatic monomer(s), one or more crosslinker(s) and one or more ether(s) and/or ester(s) of vinyl alcohol.
• Strongly acidic cation exchangers can be obtained by functionalizing crosslinked styrene bead polymers.
• the functionalization generates covalently bonded sulfonic acid groups through reaction of aromatic units of the polymer skeleton with a sulfonating agent, for example sulfuric acid.
• a further problem of the known strongly acidic cation exchangers is their tendency to release sulfonated, water-soluble fragments from water in use as a result of the action of a wide variety of different oxidizing agents dissolved in water (atmospheric oxygen, hydrogen peroxide, vanadyl salts, chromates).
• This phenomenon known in general to those skilled in the art by the term “leaching” leads to the enrichment of sulfonated organic constituents in the water to be treated, which can lead to various problems in the downstream systems which are reliant on the supply of fully demineralized water.
• the water-soluble fragments lead, for example, to corrosion problems in the cooling circuit of power plants, to defects in the microchips produced in the electronics industry, to the failure of the system owing to excessively high electrical conductivity of the water in eroding machines.
• the mechanical and osmotic stability of strongly acidic cation exchangers can be increased via two-stage structure of the bead polymers, in a so-called seed-feed process.
• Such processes are described, for example, in EP 0 101 943 A2, EP-A 1 000 659 and DE-A 10 122 896.
• the cation exchangers produced in two stages exhibit an outstanding mechanical stability, but release significantly more sulfonated degradation products to the treated water than the resins produced in one stage.
• the oxidation stability of the strongly acidic cation exchangers can be increased by adding antioxidants, as described, for example, in EP-A 0 366 258. These antioxidants are washed slowly out of the resin, which leads to the release of organic constituents to the water treated. Furthermore, they are spent after a relatively short time in use. Thereafter, the resin treated with antioxidants exhibits the same oxidation sensitivity as a conventional strongly acidic cation exchanger.
• the oxidation stability of the strongly acidic cation exchangers can also be improved by increasing the crosslinking density of the bead polymer.
• the incorporation of major amounts of crosslinker makes the polymers more brittle, which leads to a significant reduction in the mechanical stability of the beads.
• the kinetics of the cation exchange decrease significantly with increasing crosslinking density, which leads to insufficient absorption capacities in many applications.
• the problem addressed by the present invention is therefore that of providing a simple, robust and economically viable process for producing cation exchangers with rapid exchange kinetics, high mechanical and osmotic stability, and high oxidation stability.
• the solution to the problem and hence the subject-matter of the present invention is a process for producing strongly acidic cation exchangers by sulfonating crosslinked bead polymers formed from vinylaromatic monomers, wherein the bead polymers comprise from 0.2 to 20% by weight of vinyl ethers and/or vinyl esters as comonomer(s).
• cation exchangers which are obtained by the process according to the invention have a significantly higher oxidation stability as compared with the prior art, coupled with equal or higher mechanical and osmotic stability. It has additionally been found that, surprisingly, the improvement in the oxidation stability of the strongly acidic cation exchangers obtained from the inventive bead polymers is attributable solely to the incorporation of the comonomer in the bead polymer, irrespective of in what manner and at what time the comonomer is added and polymerized in the course of formation of the bead polymer.
• Crosslinked bead polymers suitable in accordance with the invention are copolymers of at least one monoethylenically unsaturated aromatic monomer, at least one crosslinker and at least one vinyl ether or vinyl ester.
• Crosslinkers are added to the monomers.
• Crosslinkers are generally polyethylenically unsaturated compounds, preferably divinylbenzene, divinyltoluene, trivinylbenzene, octadiene or triallyl cyanurate.
• the vinylaromatic crosslinkers are more preferably divinylbenzene and trivinylbenzene. Very particular preference is given to divinylbenzene.
• To prepare the bead polymers it is possible to use technical-grade qualities of divinylbenzene which, as well as the isomers of divinylbenzene, comprise customary by-products such as ethylvinylbenzene. According to the invention, technical-grade qualities with divinylbenzene contents of from 55 to 85% by weight are particularly suitable.
• the crosslinkers can be used alone or as a mixture of different crosslinkers.
• the total amount of crosslinkers for use is generally from 0.1 to 80% by weight, preferably from 0.5 to 60% by weight, more preferably from 1 to 40% by weight, based on the sum of the ethylenically unsaturated compounds.
• the comonomer(s) used are vinyl ethers and/or vinyl esters.
• vinyl ethers are understood to mean the ethers of vinyl alcohol and of isopropenyl alcohol.
• Vinyl ethers in the context of the present invention may contain one or more vinyl or isopropenyl alcohol units. Preference is given to alkyl and hydroxyalkyl ethers having from 1 to 18 carbon atoms, and ethers with condensation products of ethylene glycol.
• Very particular preference is given to using ethylene glycol divinyl ether, diethylene glycol divinyl ether and butanediol divinyl ether.
• vinyl esters are understood to mean the esters of vinyl alcohol and of isopropenyl alcohol.
• Vinyl esters in the context of the present invention may contain one or more vinyl or isopropenyl alcohol units.
• esters of carboxylic acids having from 1 to 18 carbon atoms.
• Particular preference is given to using vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl hexanoate, vinyl octoate, vinyl decanoate, vinyl laurate, vinyl myristate, vinyl oleate, vinyl palmitate, vinyl benzoate, divinyl phthalate or isopropenyl acetate.
• Very particular preference is given to using vinyl acetate and isopropenyl acetate.
• the comonomer is used in amounts of from 0.2 to 20% by weight, based on the sum of vinylaromatic monomers and crosslinkers. Preference is given to using amounts of from 0.5 to 15% by weight, more preferably from 1 to 10% by weight. When mixtures of vinyl ethers and/or vinyl esters are used, the amounts are based on the sum of all comonomers.
• the comonomer can be added to the monomer mixture before the polymerization sets in. However, it can also be metered in in the course of the polymerization, preferably at a polymerization conversion between 10 and 90%, more preferably between 15 and 80%.
• the comonomer is added to the aqueous phase in the course of the polymerization together with a water-soluble initiator.
• Suitable water-soluble initiators in this preferred embodiment are compounds which form free radicals when the temperature is increased.
• peroxodisulfates particular preference to potassium peroxodisulfate, sodium peroxodisulfate and ammonium peroxodisulfate, water-soluble azo compounds, more preferably 2,2′-azobis(2-amidinopropane)hydrochloride, 2,2′-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]tetrahydrate, 2,2′-azobis[N,N′-dimethyleneisobutyramidine], 4,4′-azobis(4-cyanovaleric acid), and also hydroperoxides, more preferably t-butyl hydroperoxide and cumyl hydroperoxide.
• the comonomer can also be added after the polymerization of the bead polymer has ended and can be polymerized in a separate polymerization step.
• porogens serve for the formation of a pore structure in the nonfunctional bead polymer.
• the porogens used are preferably organic diluents. Particular preference is given to using those organic diluents which dissolve in water to an extent of less than 10% by weight, preferably less than 1% by weight.
• porogens are toluene, ethylbenzene, xylene, cyclohexane, octane, isooctane, decane, dodecane, isododecane, methyl isobutyl ketone, ethyl acetate, butyl acetate, dibutyl phthalate, n-butanol, 4-methyl-2-pentanol or n-octanol.
• the porogens used may also be uncrosslinked, linear or branched polymers, for example polystyrene and polymethyl methacrylate. Also suitable are mixtures of different porogens.
• the porogen is used typically in amounts of from 10 to 70% by weight, preferably from 25 to 65% by weight, based in each case on the sum of the ethylenically unsaturated compounds.
• the abovementioned monomers are polymerized in the presence of a dispersing assistant using an initiator in aqueous suspension.
• the dispersing assistants used are preferably natural and synthetic water-soluble polymers. Particular preference is given to using gelatin, starch, cellulose derivatives, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, polymethacrylic acid or copolymers of (meth)acrylic acid and (meth)acrylic esters. Very particular preference is given to using gelatins or cellulose derivatives, especially cellulose esters and cellulose ethers, such as carboxymethylcellulose, methylcellulose, hydroxyethylcellulose or methylhydroxyethylcellulose.
• the amount of the dispersing assistants used is generally from 0.05 to 1%, preferably from 0.1 to 0.5%, based on the water phase.
• initiators are used in the monomer mixture.
• the monomer mixture refers to the mixture of vinylaromatic monomers, crosslinker(s), comonomer(s) and if appropriate porogen(s).
• Suitable initiators are compounds which form free radicals when the temperature is increased and dissolve in the monomer mixture.
• peroxy compounds particular preference to dibenzoyl peroxide, dilauryl peroxide, bis(p-chlorobenzoyl) peroxide, dicyclohexyl peroxydicarbonate or tert-amylperoxy-2-ethylhexane, and also to azo compounds, particular preference to 2,2′-azobis(isobutyronitrile) or 2,2′-azobis(2-methylisobutytonitrile), or else aliphatic peroxy esters, preferably tert-butyl peroxyacetate, tert-butyl peroxyisobutyrate, tert-butyl peroxypivalate, tert-butyl peroxyoctoate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxyneodecanoate, tert-amyl peroxypivalate, tert-amyl peroxyoctoate,
• the initiators which are soluble in the monomer mixture are employed generally in amounts of from 0.05 to 6.0% by weight, preferably from 0.1 to 5.0% by weight, more preferably from 0.2 to 2% by weight, based on the sum of the ethylenically unsaturated compounds.
• the water phase may comprise a buffer system which adjusts the pH of the water phase to a value between 12 and 3, preferably between 10 and 4.
• buffer systems contain phosphate, acetate, citrate or borate salts.
• an inhibitor dissolved in the aqueous phase may be advantageous to use an inhibitor dissolved in the aqueous phase.
• Useful inhibitors include both inorganic and organic substances.
• inorganic inhibitors are nitrogen compounds such as hydroxylamine, hydrazine, sodium nitrite or potassium nitrite.
• organic inhibitors are phenolic compounds such as hydroquinone, hydroquinone monomethyl ether, resorcinol, pyrocatechol, tert-butylpyrocatechol, condensation products of phenols with aldehydes.
• Further organic inhibitors are nitrogen-containing compounds, for example diethylhydroxylamine and isopropylhydroxylamine.
• Resorcinol is preferred as an inhibitor.
• the concentration of the inhibitor is 5-1000 ppm, preferably 10-500 ppm, more preferably 20-250 ppm, based on the aqueous phase.
• the organic phase can be dispersed into the aqueous phase as droplets by stirring or by jetting.
• the organic phase is understood to mean the mixture of monomer(s) and crosslinker(s), and also, if appropriate, additionally porogen(s) and/or initiator(s).
• the organic droplets are generated by stirring. On the 4 liter scale, stirrer speeds of from 250 to 400 rpm are typically used.
• stirrer speeds of from 250 to 400 rpm are typically used.
• it is advisable to maintain the homogeneous droplet diameter by encapsulating the organic droplets. Processes for microencapsulating jetted organic droplets are described, for example, in EP 0 046 535, whose contents in relation to microencapsulation are encompassed by the present application.
• the mean particle size of the unencapsulated or encapsulated monomer droplets is 10-1000 ⁇ m, preferably 100-1000 ⁇ m.
• the ratio of the organic phase to the aqueous phase is generally from 1:20 to 1:0.6, preferably from 1:10 to 1:1, more preferably from 1:5 to 1:1.2.
• the organic phase can also, according to EP-A 0 617 714 whose teaching is encompassed by the present application, be added in the so-called seed-feed process to a suspension of seed polymers which absorb the organic phase.
• the mean particle size of the seed polymers swollen with the organic phase is 5-1200 ⁇ m, preferably 20-1000 ⁇ m.
• the ratio of the sum of organic phase +seed polymer relative to the aqueous phase is generally 1:20 to 1:0.6, preferably 1:10 to 1:1, more preferably 1:5 to 1:1.2.
• the polymerization of the monomers and comonomers is performed at elevated temperature.
• the polymerization temperature is guided by the decomposition temperature of the initiator and is typically in the range from 50 to 150° C., preferably from 60 to 130° C.
• the polymerization time is from 30 minutes to 24 hours, preferably from 2 to 15 hours.
• the crosslinked bead polymers are removed from the aqueous phase, preferably on a suction filter, and optionally dried.
• the crosslinked bead polymers are converted to cation exchangers by sulfonation.
• Useful sulfonating agents include sulfuric acid, chlorosulfonic acid and sulfur trioxide. Preference is given to using sulfuric acid.
• the sulfuric acid is used preferably in a concentration of from 80 to 120%, more preferably from 85 to 105%, most preferably from 88 to 99%.
• concentration figures more than 100% mean solutions of sulfur trioxide (SO 3 ) in 100% sulfuric acid.
• SO 3 sulfur trioxide
• a sulfuric acid concentration of 120% is understood to mean a 20% solution of SO 3 in 100% sulfuric acid.
• the ratio of sulfuric acid to bead polymer is from 2.0 to 6 ml/g, preferably from 2.5 to 5 ml/g, more preferably from 2.6 to 4.2 ml/g.
• a swelling agent preferably chlorobenzene, dichloroethane, dichloropropane or methylene chloride, can be employed in the sulfonation.
• the swelling agent is used preferably in amounts of from 0.1 to 1 ml per gram of dry bead polymer, more preferably from 0.2 to 0.5 ml per gram of dry bead polymer.
• the swelling agent is preferably added to the bead polymer initially charged in sulfuric acid before the onset of the sulfonation reaction.
• the temperature in the sulfonation is generally 50-200° C., preferably 80-160° C., more preferably 90-140° C. It may be advantageous to employ a temperature program in the sulfonation, in which the sulfonation is commenced at a first temperature in a first reaction step and continued at a higher temperature in a second reaction step.
• the reaction mixture is stirred. It is possible to use different stirrer types, such as paddle stirrers, anchor stirrers, gate stirrers or turbine stirrers.
• the duration of the sulfonation reaction is generally several hours, preferably between 1 and 24 h, more preferably between 2 and 16 h, most preferably between 3 and 12 h.
• reaction mixture composed of sulfonation product and residual acid is cooled to room temperature and diluted first with sulfuric acids of decreasing concentrations and then with water.
• the cation exchanger obtained in accordance with the invention can be treated in the H form, for purification, with deionized water at temperatures of 70-180° C., preferably of 105-130° C.
• the cationic exchanger from the acidic form to the sodium form.
• This conversion is effected with sodium hydroxide solution of a concentration of 2-60% by weight, preferably 4-10% by weight, or with aqueous sodium chloride solutions which are 1-25% by weight, preferably 4-10% by weight, in sodium chloride.
• the cation exchangers can be purified further by treating with deionized water or aqueous salt solutions, for example with sodium chloride or sodium sulfate solutions. It has been found that the treatment at 70-150° C., preferably 120-135° C., is particularly effective and does not bring about any reduction in the capacity of the cation exchanger.
• inventive, strongly acidic cation exchangers may contain pores.
• Porous inventive strongly acidic cation exchangers may be microporous, mesoporous and/or macroporous.
• gel-form for polymers, reference is made to Pure Appl. Chem., Vol. 76, No. 4, p. 889-906, 2004 (IUPAC recommendations 2003), more particularly to p. 900 ⁇ 3.9 and p. 902-903 ⁇ 3.23.
• the inventive, strongly acidic cation exchangers have a mean particle size D between 30 ⁇ m and 1000 ⁇ m, preferably between 100 and 800 ⁇ m.
• the mean particle size D is understood in the context of the present invention to mean 50% value ( ⁇ (50)) of the volume distribution.
• the 50% value ( ⁇ (50)) of the volume distribution indicates the diameter which is above that of 50% by volume of the particles.
• monodisperse strongly acidic cation exchangers are produced.
• Monodisperse particle size distributions in the context of the present invention have a proportion by volume of particles between 0.9 D and 1.1 D of at least 75% by volume, preferably at least 85% by volume, more preferably at least 90% by volume.
• the present invention also relates to a process for producing strongly acidic cation exchangers, characterized in that:
• the strongly acidic cation exchangers obtained by the process according to the invention are notable for a particularly high mechanical stability, osmotic stability and oxidation stability. Even after prolonged use and multiple regeneration, they exhibit barely any defects in the ion exchanger spheres.
• the inventive strongly acidic cation exchangers there is a multitude of different applications. For example, they can be used in drinking water treatment, in the production of power plant water and ultrapure water (needed in microchip production for the computer industry), for chromatographic separation of glucose and fructose and as catalysts for various chemical reactions (for example bisphenol A preparation from phenol and acetone).
• the total capacity of the cation exchanger is calculated as follows:
• 100 beads are viewed under a microscope. The number of beads which bear cracks or exhibit splintering-off is determined. The number of perfect beads is calculated from the difference between the number of damaged beads and 100.
• the resin is rinsed back with demineralized water for 5 minutes.
• the rate of back-rinsing is regulated such that the resin is distributed over the entire filter tube length.
• One working operation comprises 4 cycles of 10 minutes each of loading and regeneration and 2 ⁇ 5 minutes each of back-rinsing. Acid and alkali run through the exchangers at 500 ml per cycle through capillaries.
• the exchanger is flushed out of the filter tube, and the water is sucked in with the screen tube and mixed thoroughly.
• the exchanger is then counted under the microscope for the percentage of whole beads, of cracked beads and splinters as in the determination of the original stability.
• 750 ml of resin are shaken in and washed in cocurrent with UPW water at a rate of 15 l/h for 4 hours.
• UPW water is defined as water having a conductivity of ⁇ 17.8 MOhm cm and a content of organic material (TOC) ⁇ 2.00 ppb.
• TOC organic material
• the 750 ml of resin are subjected to suction on a glass suction filter for 5 minutes.
• the washed and suctioned cation exchanger are transferred into a glass bottle.
• the closed glass bottle is stored in daylight at room temperature for 4 weeks.
• the resin is admixed with 100 g of UPW water and shaken at 100 rpm for 10 minutes. Subsequently, the sample is filtered off and the eluate is tested by the following methods: pH, absorbance at 225 nm (1 cm cuvette) and visual assessment of reddening, the mark 0 indicating a completely colorless eluate and the mark 4 a deep red eluate.
• Demineralized water in the context of the present invention is characterized in that it possesses a conductivity of from 0.1 to 10 ⁇ S, the content of dissolved or undissolved metal ions being not greater than 1 ppm, preferably not greater than 0.5 ppm for Fe, Co, Ni, Mo, Cr, Cu as individual components, and being not greater than 10 ppm, preferably not greater than 1 ppm, for the total of the metals mentioned.
• a 4 l glass reactor was initially charged with 1020 g of demineralized water, and a solution of 3.2 g of gelatin, 4.8 g of disodium hydrogenphosphate dodecahydrate and 0.24 g of resorcinol in 86 g of demineralized water was added and mixed. The temperature of the mixture was adjusted to 25° C.
• microencapsulated monomer droplets which had been obtained by jetting and had a narrow particle size distribution, containing 4.5% by weight of divinylbenzene, 1.12% by weight of ethylstyrene, 0.36% by weight of tert-butyl peroxy-2-ethylhexanoate and 94.02% by weight of styrene, were added with stirring, the microcapsules having consisted of a formaldehyde-hardened complex coacervate of gelatin and a copolymer of acrylamide and acrylic acid, and 1182 g of aqueous phase with a pH of 12 were added.
• the mixture was polymerized to completion with stirring by increasing the temperature according to a temperature program beginning at 25° C. and ending at 95° C.
• the mixture was cooled, washed over a 315 ⁇ m screen and then dried at 80° C. under reduced pressure. 1152 g of a seed bead polymer having a mean particle size of 365 ⁇ m, and narrow particle size distribution and a smooth surface were obtained.
• a 4 l stirred reactor with gate stirrer, temperature sensor, distillation system and thermostat and temperature recorder was initially charged with 741 ml of 87.8% by weight sulfuric acid at room temperature.
• 350 g of bead polymer from C1a) and 88 ml of 1,2-dichloroethane were introduced with stirring.
• the reactor contents were stirred at 40° C. for 30 minutes.
• 159 ml of oleum 65% by weight SO 3 in 100% by weight sulfuric acid
• a 4 l stirred reactor with gate stirrer, temperature sensor, distillation system and thermostat and temperature recorder was initially charged with 1400 ml of 98% by weight sulfuric acid and heated to 100° C. Within 30 minutes, 350 g of bead polymer from C2a) were introduced in 10 portions with stirring. Subsequently, the mixture was stirred at 100° C. for 30 minutes and at 115° C. for 5 hours. After cooling, the suspension was transferred into a glass column. Sulfuric acid of decreasing concentration, beginning with 90% by weight and ending with pure water, was applied to the column from the top.
• a 4 l stirred reactor with gate stirrer, temperature sensor, distillation system and thermostat and temperature recorder was initially charged with 1200 ml of 98% by weight sulfuric acid and heated to 100° C. Within 30 minutes, 300 g of bead polymer from 4a) were introduced in 10 portions with stirring. Subsequently, the mixture was stirred at 115° C. for 5 hours and at 135° C. for 2 hours. After cooling, the suspension was transferred into a glass column. Sulfuric acid of decreasing concentration, beginning with 90% by weight and ending with pure water, was applied to the column from the top.
• Example 2a was repeated. 1570 g of a monodisperse bead polymer were obtained.
• the pH gives information as to how much soluble acid (principally polystyrenesulfonic acid, so-called leaching, combined with small amounts of sulfuric acid from the hydrolysis of the sulfonic acid groups of the resin) has been formed under air after a given storage time; the absorption at 225 nm is a measure for the water-soluble aromatic compounds released, in this case oligomeric and polymeric styrenesulfonic acids.
• Tab. 2 shows that the inventive strongly acidic cation exchangers possess total capacities which are in no way inferior to the total capacity of the comparative examples.
• inventive strongly acidic cation exchangers have very high original and swelling stability values which are comparable to or higher than the values of the comparative examples corresponding to the state of the art.
• Tab. 2 also shows that the improvement in the profile of properties of the inventive strongly acidic cation exchangers is particularly marked for the divinyl ether compounds (examples 2, 3, 4, 7).
• Comparison of examples 2, 3 and 4 shows that the effect of adding vinyl ether and/or vinyl ester in the polymerization is independent of the type and of the time of comonomer incorporation.
• Example 9 compared with comparative example 4 reveals that the improvement in the oxidation stability of the strongly acidic cation exchangers as a result of the inventive incorporation of vinyl ether(s) and/or vinyl ester(s) also occurs in the case of macroporous resins.

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