| abstract |
An aqueous coating composition is produced from a polyurethane dispersion having an ionic hydrophilic group containing no solvent. I) Solvent-free polyurethane dispersion has 1) polyisocyanate, Mn 500-6000 polyol, Mn 62-500 polyol and ionic or potentially ionic groups in the first step. Preparing an NCO prepolymer solution in a solvent which is a reaction product with the compound and has a boiling point of less than 100 ° C. under atmospheric pressure, 2) in the second step, NCO prepolymer I.1) is dispersed in water; Neutralize potential ionic groups to form ionic groups, 3) In the third step, NCO prepolymer I.1) is chain extended with a polyamine of less than 500 Mn, 4) In the fourth step, An aqueous coating composition is prepared by completely removing the solvent and then II) adding 1-7% by weight of ethylene or propylene glycol ether to the polyurethane dispersion I). [Selection figure] None |