[Filtration of solutions with high viscosity: from laboratory experiments to production].

The Zinc Hyaluronate complex has several advantages from the point of view of woundhealing. The author's task was the elaboration of the sterile filtration technology of the 0.2% Zinc Hyaluronate solution. In the first step 0.2 micron pore diameter filters were used. During the scale up process we found that the filter boards are not suitable. The filtration time extremely increased and sometimes the whole process stopped because of the relatively small filtration area. For larger batches polypropylene capsule filters have been applied. The mean pore diameter of the filter was 0.2 micron but the unregular pore size distribution did not make the filtrate microbe free. In the next experience inlet pore diameter was 0.65 micron--the outlet pore diameter 0.45 micron. This filtration process resulted in a sterile filtrate with reduced active content. This means that the solution has been ultrafiltrated. Applying too high pressure and form a compact layer on the filter's surface which is functioning as a secondary filter layer. The filtration should begin with low pressure and it has to increase it gradually from 0 to 2 bar in 0.5 bar steps. It was supposed that at high temperature filtration could be easier and faster. On the contrary we found that depending on the concentration above 35-45 degrees C the active content of the filtrate is decreasing. In the case of the filtration of the fraction with a lower temperature the fractions with high molecular weight can be filtrated because of the anisometric distribution of the molecules. The filtration of these products is very difficult even at laboratory scale.