Filter, process for producing and use thereof

摘要

The proposed filter for retaining and pumping underground water for preparing tap and drinking water, optionally for infiltration of water into soil consists of quartz sand and polyurethane binding agent containing polyol, aliphatic or aromatic polyisocyanate, an organic tin compound with molecular weight higher than 600 functioning as a catalyst and a mixture of a highly disperse silicic acid and/or bentonite with aluminosilicate as a thickening and modification agent, whereby the ratio of the amounts quartz sand : polyurethane binding agent is less than 20 : 1. The manufacturing process of such filter is characterized by mixing quartz sand with a defined fraction of fine dust with a polyurethane binding agent system, the mixture is then filled in molds and hardened at a temperatures above 120 degC, whereupon the hardened product is removed from the molds without cooling.