A process is disclosed for producing polyurethane resins using novel catalysts selected from the group consisting of a process for the production of cellular or non-cellular polyurethane resins comprising reacting:(a) polyisocyanates; with(b) compounds having at least 2 isocyanate reactive hydrogen atoms; in the presence of(c) tertiary amines as catalysts; optionally with the addition of(d) blowing agents, stabilizers and other known additives; characterized in that the substances used as component (c) comprise compounds selected from the group consisting of ##STR1## and mixtures thereof in which formulae: the symbols R may be the same or different and represent straight or branched-chain alkyl groups having from 1 to 4 carbon atoms;the symbols n may be the same or different and represent 2 or 3;the symbols m may be the same or different and represent 2 or 3; andk represents an integer of from 1 to 5.The process may also be carried out in the presence of other tertiary amine catalysts, particularly compounds containing one tertiary nitrogen atom and at least one amide group.The novel catalysts of the invention function as age-resistors and light-protective agents.