| 摘要 |
The invention relates to a process for the preparation of CFC-free, soft and elastic, semi-rigid or rigid mouldings containing urethane groups and having a cellular core and a compacted peripheral zone with an essentially pore-free, smooth surface, by reacting a) organic and/or modified organic polyisocyanates with b) at least one relatively high-molecular-weight compound containing at least two reactive hydrogen atoms and optionally c) low-molecular-weight chain extenders and/or crosslinking agents, in the presence of d) blowing agents, e) catalysts, f) at least one amorphous, microporous silica gel which preferably has a mean pore diameter with more than 40 % in range from 0.1 to 10 nm, a pore volume of from 0.15 to 1.8 ml/g and a BET surface area of from 200 to 900 m<2>/g, and optionally further additives, and g) assistants, in a closed mould with compaction. t |
