Process for the production of rigid polyurethane foams

摘要

The invention relates to a process for the production of rigid polyurethane foams 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 and optionally f) auxiliaries and/or additives, where the relatively high-molecular-weight compounds (b) containing at least two reactive hydrogen atoms are polyoxypropylene-polyols and/or polyoxyethylene-polyoxypropylene-polyols containing up to 30% by weight, based on the weight of the alkaline oxide units, of oxyethylene units bonded inside the chain, containing secondary hydroxyl groups, having a functionality of from 4.5 to 4.8 and a hydroxyl number of from 430 to 470 mg KOH/g, which can be prepared by anionic polymerisation of 1,2-propylene oxide and optionally ethylene oxide onto a binary initiator molecule mixture comprising sucrose and glycerol.