transition from the liquid or rubber elastic state to the hard elastic or glassy state or vice versa in accordance with the present invention the polymer mass in the reactor is granulated by a cutting or distributing effect comminuting effect of stirrers the monomer continues to undergo polymerization in the resultant granules for carrying out the method of the invention it is preferred to employ twin shaft kneading reactors as shown for example in de 199 40 521 a1 or de 41 18 884 a1 these reactors have the advantage both of a large vapor passage for evaporative cooling and of an optimum renewal of product surface by virtue of the large vapor passage of the kneading reactor it is possible to utilize evaporative cooling to remove the heat of reaction and the kneading energy which is produced until the granulation point is reached the kneading reactor is optimized in respect of self cleaning and the avoidance of dead zones furthermore the form of the kneading bars has been chosen such that mutual engagement of the kneading bars or stirring bars is not accompanied by any compression zones accordingly the homogeneous polymer mass can be granulated without local overheating induced by excessive kneading energy and grinding action the overall method is intended to run continuously the pasty mass is conveyed specifically axially a variety of shaft geometries can be chosen here the conveying angles of the kneading bars are adaptable and serve to convey the mass axially within the reactor another possibility furthermore is that of installing back conveying zones which control the fill level within the reactor particularly.