Stable nanoparticle-containing polyisocyanates

Producing nanoparticle modified polyisocyanate having free isocyanate groups comprises reacting a nanoparticle with an average particle size of less than 200 nm, determined by dynamic light scattering, with alkoxysilyl- and isocyanate-group containing adducts (I) and subsequently mixing with polyisocyanates having free isocyanate groups. Producing nanoparticle modified polyisocyanate having free isocyanate groups comprises reacting a nanoparticle with an average particle size of less than 200 nm, determined by dynamic light scattering, with alkoxysilyl- and isocyanate-group containing adducts of formula (OCN-R1-NHCO-QR2Z-SiX aY1 3 - a) (I) and subsequently mixing with polyisocyanates having free isocyanate groups. R1 : 1-14C-linear- or 3-14C-cyclic-aliphatic group or 6-14C-araliphatic or aromatic groups; R2 : H, 1-12C-alkyl or 6-20C-aryl- or -aralkyl or aspartic acid ester-residue (where R2 is present when Q is N); Q : O, S or N; X : hydrolyzable group; Y1 : alkyl; and Z : 1-12C-alkylene group; and a : 1-3 (preferably 1 or 2). Independent claims are included for: (1) the nanoparticle modified polyisocyanate, having free isocyanate groups, obtained by the above process; and (2) coated or bonded substrates that are obtained by using the nanoparticle modified polyisocyanates having free isocyanate groups. Die vorliegende Erfindung betrifft unblockierte nanopartikelmodifizierte Polyisocyanate, die sich durch eine erhöhte Stabilität im NCO-Gehalt auszeichnen.