Process for preparing filters based on crushed polyurethane material

摘要

The invented process is intended for the preparation of active filters based on a polyurethane system formed by polyurethane crushed material and supplemented with other components exhibiting absorption activity such as oxides and binding agents based for instance on cellulose, in particular of filters intended for removing cigarette smoke, filters for removing microscopic contaminants of engine lubricating systems, filters for removing harmful substances from engine exhaust gases, filters for removing microscopic contaminants of engine air suction tracts, filters for filtering engine fuel feeding systems, optionally other filter types. Hard polyurethane foam is crushed in a suitable crushing device at a temperature ranging from -60 degC to -20 degC to particles of average particle size ranging from 1 micron to 100 micron, these polyurethane particles are then mixed together either with powder alumina, SiOi2, MgO or Fei2Oi3 of particle size ranging from 1 to 20 micron, or with a mixture of all specified oxides, and further with hydroxyethyl cellulose and/or carboxymethyl cellulose, and/or oxycellulose with average molar weight in the range of 5x10e3 to 5x10e5 Da in weight ratio polyurethane : oxides : cellulose derivative = 1 : 0.1 - 0.3 : 0.01 - 0.2 with a small addition of water so that a pasty mass is obtained. The pasty mass is the subjected to homogenization within a worm mixer wherefrom it is then extruded in the form of fibrils through a nozzle with hole diameter of 0.2 mm into an anhydrous ethanol at simultaneous cutting so as to form cylindrical particles being 1 mm long. These particles are subsequently separated from the alcohol base and subjected to additional heat treatment to remove residual water and ethanol.