Polymerizable liquid compositions of the polyurethane type, consisting of two components (A) and (B), wherein component (A) contains at least one cyclo-aliphatic diisocyanate monomer or a mixture of one cyclo-aliphatic diisocyanate monomer and a pre-polymer obtained by reaction, in the presence of an acid phosphate ester catalyst, between said cyclo-aliphatic diisocyanate monomer and one or more polyols having two or more hydroxy 1 groups per molecule and a molecular weight ranging from 50 to 2,000 g/mole; the second component (B) contains one or more polyols having a molecular weight ranging from 50 to 2,000 g/mole and a functionality between 2 and 5; in the absence of polyalkoxylated tertiary diamines and organometallic catalysts, said components (A) and (B) being present in a weight ratio which varies from 1:1 to 2:1 and the process for the production of organic glass starting from polymerizable liquid compositions of the polyurethane type.