Abstract: Storage stable polymer-oligomer particles with a high swelling capacity are produced by means of two-stage seed polymerisation in which the mole ratio between initiator and monomer is in the range from 0.07:1 to 0.01:1. These particles are used to produce polymer particles with a narrow size distribution by seed polymerisation.

Abstract: The present invention concerns large spherical polymer particles with a narrow size distribution and a procedure for producing such particles. The procedure is characterized in that a seed polymerization is performed in which the start particles have a very high ability to absorb new monomer so that finished particles are obtained after only one stage of polymerization even if the finished particles are to be as large as in the range 10 to 100 ?m. The procedure is also characterized in that, when porous particles are produced, a porous structure can be formed in which the fraction of micropores is insignificant. Another characteristic feature of the procedure is that the size distribution of the finished particles is narrow and in some cases narrower than in the start particles.