Process for producing coarse-particle anion-exchanger gels

1. Process for producing monodisperse anion-exchanger gels with high stability and purity and grain size greater than 800 μm, comprising:

a.) forming a suspension of a seed polymer composed of a crosslinked polymer with a swelling index of from 2.5 to 7.5 and with less than 1% by weight of non-vapourizable, extractable fractions in a continuous aqueous phase,

b.) swelling the suspended seed polymer in a monomer mixture made from vinyl monomer, crosslinker and free-radical initiator,

c.) polymerizing the monomer mixture in the seed polymer,

d.) swelling the resultant polymer in a second monomer mixture made from vinyl monomer, crosslinker and free-radical initiator,

e.) polymerizing the second monomer mixture in the first seed-feed polymer and

f.) functionalizing the resultant copolymer with swelling index from 1.5 to 3 and average diameter greater than 520 μm by chloromethylation and then amination to give the anion exchanger.

2. Process according to claim 1 , wherein the seed polymer is a crosslinked polymer prepared from

i) from 96.5 to 99.0% by weight of monomer

ii) from 0.8 to 2.5% by weight of crosslinker and

iii) from 0.2 to 1.0% by weight of aliphatic peroxyester as polymerization initiator.

3. Process according to claim 2 , wherein the aliphatic peroxyester has the formulae (I), (II) or (III),

where

R 1 is an alkyl radical having from 2 to 20 carbon atoms or a cycloalkyl radical having up to 20 carbon atoms,

R 2 is a branched alkyl radical having from 4 to 12 carbon atoms and

L is an alkylene radical having from 2 to 20 carbon atoms or a cycloalkylene radical having up to 20 carbon atoms.

4. Process according to claim 2 , wherein the seed polymer is prepared by spraying and microencapsulation, and is monodisperse and has a swelling index of from 2.5 to 7.5.

5. Process according to claim 1 , wherein the feed polymerization is carried out in at least two or more steps.

6. Process according to claim 5 , wherein the feed polymerizations take place in succession without any solid-liquid phase separation.

7. Process according to claim 5 , wherein the free-radical initiator for the feed polymerization is an aliphatic peroxyester or an aromatic diperoxide.

8. Process according to claim 5 , wherein the feed steps comprise use of a protective colloid which is a reversible methylhydroxyethylcellulose or type A gelatine.

9. Process according to claim 5 , wherein the feed steps 1 and 2 provide swelling indices of from 2.5 to 3.5 and from 1.75 to 2.5 and grain size ranges of from 380 to 420 μm and 560 to 600 μm.

10. Process according to claim 1 , wherein chloromethylation is from 80 to 90% and the amination takes place in the presence of less than 5% by weight, based on the total amount of water, of an inorganic salt.