MANUFACTURE OF COMPOSITE BODY COMPRISING 1 MOL OF DIMERIZED OR LOW OLIGOMERIZED 4,4'- DIISOCYANATEDIPHENYLMETHANE AND 2 OR 3 MOLS OF 4,4'-DIISOCYANATEDIPHENYL METHANE, CORRESPONDING COMPLEX AND USE FOR MANUFACTURE OF POLYURETHANE

The present invention relates to a process for the dimerization of 4,4'-diisocyanatodiphenylmethane from emulsion in apolar solvents with the formation of complexes and to the complexes obtainable for the first time by this process. The complexes consist of one mol of low molecular weight 4,4'-diisocyanato-diphenylmethane-uretdione or its low oligomers corresponding to the idealized formula (I) (I) (n=0 to 0.5, where n is the average degree of oligomerization of the dimer) and 2 to 3 mol of 4,4'-diisocyanatodiphenylmethane (MDI) (II) In the process according to the invention, 4,4'-diisocyanatodiphenylmethane (II) in the molten form is emulsified in apolar solvents. Dimerization is started in the presence of conventional dimerization catalysts at temperatures above the melting point of MDI, preferably up to an upper temperature limit of 50 DEG to 60 DEG C. The temperature is then lowered to