CPC C08G 18/64 (2013.01) [C08G 18/73 (2013.01); C08J 3/05 (2013.01); C09D 175/04 (2013.01)] | 7 Claims |
1. A self-crosslinking aqueous polyurethane dispersion, including the following components:
20-40% by weight of a hydroxyl-containing polyurethane with blocked NCO groups;
60-80% by weight of deionized water;
0-8% by weight of an organic solvent; and
a pH regulator;
wherein, the hydroxyl-containing polyurethane with blocked NCO has a blocked NCO content of 1.8-5.0% and a hydroxyl content of 0.5-2.0% based on the dry solid portion;
wherein, the hydroxyl-containing polyurethane with blocked NCO is prepared by the following components:
30-50 parts by weight of a polymer polyol;
0.5-3 parts by weight of trimethylolpropane or trimethylolethane;
30-50 parts by weight of a isocyanate monomer;
3.0-6.0 parts by weight of 2,2-dimethylol propionic acid or 2,2-bis(hydroxymethyl)butyric acid;
5.0-15.0 parts by weight of a NCO blocking agent;
4.0-10.0 parts by weight of a hydroxyalkyl ethylenediamine chain extender;
0.01-0.05 parts by weight of a catalyst;
and wherein the self-crosslinking aqueous polyurethane dispersion is prepared by a method comprising:
(a) adding the polymer polyol, trimethylolpropane or trimethylolethane, isocyanate monomer, 2,2-dimethylol propionic acid or 2,2-bis(hydroxymethyl)butyric acid, catalyst and organic solvent to a reactor and reacting at 50-90° C. until the NCO content reaches or becomes less than a theoretical value to obtain a prepolymer, in which the isocyanate monomer is excessive;
(b) adding the NCO blocking agent to the prepolymer obtained in step (a) to partially block the NCO, and reacting at 50-90° C. until the NCO content reaches or becomes less than the theoretical value to obtain a polymer;
(c) cooling the polymers obtained in step (b) to 20-40° C., adding a pH regulator into the polymer, and then dispersing the polymer into the deionized water;
(d) then adding the hydroxyalkyl ethylenediamine chain extender, and reacting at 10-40° C. for 30 minutes; and
(e) in step (a), if the organic solvent added N-methyl-pyrrolidone, the solvent does not require to be separated; if the solvent added is acetone or butanone, the solvent needs to be separated by heating;
wherein a molar ratio of the blocked NCO to the hydroxyl groups introduced from the chain extender is 1:1 to 1.5:1.
|