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Process for producing cation exchangers

a technology of cation exchangers and cation exchangers, which is applied in chemical/physical processes, water/sewage treatment by ion exchange, nuclear engineering, etc., can solve the problems of unfavorable cation exchanger function, unsatisfactory stability of cation exchangers, and damage to bead polymers, so as to reduce the throughput of liquid to be purified, the effect of rapid exchange kinetics, high mechanical and osmotic stability

Inactive Publication Date: 2009-06-18
LANXESS DEUTDCHLAND GMBH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention relates to a process for producing strong acidic cation exchangers by sulfonating crosslinked bead polymers formed from vinylaromatic monomers. The invention has discovered that these cation exchangers have significantly higher oxidation stability compared to those produced using other methods. The technical effect of the invention is that the resulting cation exchangers have improved mechanical and osmotic stability. The invention also provides a process for incorporating comonomers in the bead polymers, which further enhances the stability of the cation exchangers. The crosslinked bead polymers used in the invention can be copolymers of vinylaromatic monomers, vinyl ethers, vinyl esters, or mixtures of these monomers. The amount of comonomer used in the polymerization can be from 0.2 to 20% by weight.

Problems solved by technology

One problem with the known strongly acidic cation exchangers is that of their stability under stress, which is not always sufficient.
Moreover, the presence of damaged bead polymers is unfavorable for the functioning of the cation exchangers themselves which are used in column processes.
Splinters lead to an elevated pressure drop of the column system and hence reduce the throughput of the liquid to be purified through the column.
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.
For example, 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.
There has been no lack of attempts to provide strongly acidic cation exchangers which have an improved mechanical stability, osmotic stability and / or an improved oxidation stability.
However, the presence of acrylic acid units in the polymer structure leads to a higher oxidation susceptibility of the resins.
Bachmann et al. describe in EP-A 868 444, a process for producing mechanically and osmotically stable cation exchangers by sulfonating without addition of chlorinated swelling agents at temperatures between 125 and 180° C. However, dispensing with the chlorinated swelling agent in the sulfonation does not improve the oxidation stability of the resins.
Furthermore, they are spent after a relatively short time in use.
However, 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.
Moreover, the kinetics of the cation exchange decrease significantly with increasing crosslinking density, which leads to insufficient absorption capacities in many applications.

Method used

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  • Process for producing cation exchangers

Examples

Experimental program
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Effect test

example 1

Preparation of a Monodisperse Seed Bead Polymer Based on styrene, divinylbenzene and ethylstyrene

[0081]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. With stirring, 1182 g of 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.

[0082]The mixture was polymerized to completion with stirring by increasi...

example 2 (

Inventive)

2a) Preparation of a Bead Polymer with diethylene glycol divinyl ether

[0094]In a 4 l stirred reactor with gate stirrer, condenser, temperature sensor and thermostat and temperature recorder, an aqueous initial charge composed of 1443 g of deionized water and 5.88 g of disodium hydrogenphosphate dodecahydrate was obtained. To this initial charge were added, with stirring at 200 rpm, 864.9 g of seed polymer prepared as in example 1.

[0095]Within 30 min, a mixture of 625.7 g of styrene, 109.5 g of divinylbenzene (81.4%) and 5.88 g of dibenzoyl peroxide was added. To remove atmospheric oxygen, the mixture was then sparged with nitrogen for 15 minutes. Subsequently, the reactor contents were brought to 30° C. within 30 minutes and kept at this temperature for 30 minutes. A solution of 3.2 g of methylhydroxyethylcellulose dissolved in 157 g of water was then added, and the mixture was stirred at 30° C. for another 1 hour. The mixture was heated to 62° C. for 16 hours. Then 30 g o...

example 3 (

Inventive)

3a) Preparation of Bead Polymers with diethylene glycol divinyl ether

[0098]In a 4 l stirred reactor with gate stirrer, condenser, temperature sensor and thermostat and temperature recorder, an aqueous initial charge composed of 1443 g of deionized water, 4.85 g of boric acid and 2.72 g of 50% by weight sodium hydroxide solution was obtained. To this initial charge were added, with stirring at 200 rpm, 864.9 g of seed polymer prepared as in example 1.

[0099]Within 30 min, a mixture of S g of styrene (see table), 109.5 g of divinylbenzene (81.3%), X g of diethylene glycol divinyl ether (DEGDVE, see table) and 2.35 g of tert-butyl peroxy-2-ethylhexanoate was added. To remove atmospheric oxygen, the mixture was then sparged with nitrogen for 15 minutes. Subsequently, the reactor contents were brought to 30° C. within 30 minutes and kept at this temperature for 30 minutes. Then a solution of 3.2 g of methylhydroxyethylcellulose dissolved in 157 g of water was added and the mixtu...

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Abstract

Strongly acidic cation exchangers with high mechanical, osmotic and oxidation stability can be prepared by sulfonating bead polymers formed from one or more vinylaromatic monomer(s), one or more crosslinker(s) and from 0.2 to 20% by weight of one or more vinyl ethers and / or vinyl esters.

Description

[0001]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.BACKGROUND OF THE INVENTION[0002]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.[0003]One problem with the known strongly acidic cation exchangers is that of their stability under stress, which is not always sufficient. For instance, cation exchanger beads can break up as a result of mechanical or osmotic forces. For all applications of cation exchangers, the exchangers present in bead form must maintain their habit and must not be degraded partly...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B01J39/20C02F1/42C07H1/06C13B20/14
CPCB01J31/10B01J39/20B01J39/26C02F2001/425C07C37/20C08F8/36C13B20/148C07C39/16C08F212/08
Inventor VANHOORNE, PIERREWEDEMEYER, HANS-JURGEN
Owner LANXESS DEUTDCHLAND GMBH
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