Process for the production of foams

A process for the production of poylurethane foam in a closed mold by foaming a reaction mixture which comprises a polyisocyanate component, a reactive hydrogen containing component, and an organic blowing agent, wherein

• 1. the polyisocyanate component is a mixture comprising
• A. at least one organic polyisocyanate which is liquid at room temperature and
• B. a flow improving organic compound which splits off carbon dioxide under the catalytic influence of basic compounds, said flow improving organic compound being of the formula:
• ##STR3## m represents 1 or 2 n represents 0 or 1 when m=1 and 0 when m=2,
• R.sub.1 represents an m-valent aliphatic hydrocarbon group having from 1 to 18 carbon atoms, which may be olefinically unsaturated;
• a cycloaliphatic hydrocarbon group having from 4 to 10 carbon atoms;
• an aromatic hydrocarbon group having from 6 to 10 carbon atoms;
• or an araliphatic hydrocarbon group having from 7 to 10 carbon atoms;
• R.sub.2 represents a monovalent hydrocarbon group which has the meaning defined for R.sub.1, and
• wherein from 0.1 to 5% by weight of said component (B) based on polyisocyanate (A), is used, and
• 2.