This blocked polyisocyanate composition contains a block polyisocyanate derived from one or more diisocyanates, an active hydrogen compound, and a blocking agent containing a malonic acid ester. The active hydrogen compound has a number-average molecular weight of 60 to 5,000 and an average of 1.6 to 2.4 functional groups.

The present invention relates to a process for preparing at least one blocked polyisocyanate, comprising the following steps: (A) reacting at least one polyisocyanate with at least one thermally cleavable blocking agent selected from the group consisting of primary, monofunctional alcohols and mixtures thereof to obtain at least one partially blocked polyisocyanate, (B) reacting the at least one partially blocked polyisocyanate from step (A) with at least one non-ionic hydrophilizing agent to obtain an intermediate product, and (C) reacting the intermediate product obtained in step (C) with at least one thermally cleavable blocking agent selected from the group consisting of primary, monofunctional alcohols and mixtures thereof, to obtain the at least one blocked polyisocyanate. The invention further relates to a correspondingly obtained blocked polyisocyanate, to the use of the blocked polyisocyanate for producing coating agents, adhesives, sealants or elastomers, to corresponding coating agents, adhesives, sealants or elastomers, and to substrates that are provided with coatings obtained using the at least one blocked polyisocyanate according to the invention.

A modified blocked polyisocyanate, which is a blocked polyisocyanate modified with a hydroxyl group-containing quaternary ammonium salt (I) represented by the following formula (I).

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