here specifically in the first process polyol or isocyanate is situated in the mixing chamber of a high speed mixer under vacuum messrs grieser maschinenbau und service gmbh chemiestra u03b2e 19 lampertheim the microspheres coated with caco 3 are drawn in below the liquid level via the vacuum applied in the mixing chamber care should be taken to ensure that the particles of the invention are drawn in directly in the region of maximum angular speed of the stirrer operating at a high speed the high shearing energy leads to homogeneous dispersion the air drawn in by this process is removed from the mixture by the vacuum along with the action of constant stirring in the second tested process the reaction component to be enriched with the microspheres is situated in an open tank and is pumped around by means of a dissolver negative pressure with which the pulverulent particles are drawn into the reaction component is produced in the dissolver disc messrs ystral ballrechten dottingen maximum wetting with correspondingly low air charging is thus guaranteed the incorporated air is removed by applying a vacuum while stirring the reaction component treated with microspheres the stirring mechanism is switched on or off at three minute intervals the rising air additionally collects below the blade surfaces due to the slow rotation of the blade mixer so that larger air bubbles are formed when the mixer is at a standstill the large air bubbles rise in an accelerated manner which considerably accelerates their evacuation the reaction component charged with the microspheres is advantageously added to the daily service tank of a 2 k machine for further processing to avoid separation of the specifically light hollow spheres the dispersion.