The present invention relates to a process for preparing a polyisocyanate, namely an isocyanate group-terminated polyol polyanthranilic acid ester. The process comprises the step of reacting an anthranilic acid derivative selected from anthranilic acid halide (in particular anthranilic acid chloride), isatoic anhydride or a mixture thereof with a first polyol of a number-average molar mass of at least 200 g/mol and a functionality in the range of 2 to 8, and obtaining, as a result, a polyamine (namely a polyol polyanthranilic acid ester with amine terminal groups) and reacting the polyamine with phosgene and obtaining, as a result, a polyisocyanate (namely an isocyanate group-terminated polyol polyanthranilic acid ester). The invention further relates to the polyisocyanates obtained in this way, their use in polyaddition reactions, and polyaddition products obtainable by these reactions.