Patent ID: 7342068
Filing Date: 2008-03-11
Classification: C08G,C09J

Abstract:
1. A process for forming an aqueous polyurethane dispersion, the process comprising: providing an isocyanate terminated prepolymer by reacting (i) at least one diisocyanate comprising about 50% by weight or greater of α,α,α,α-tetramethylxylene diisocyanate, (ii) at least one difunctional polyol comprising poly(propylene oxide) diol, and (iii) at least one isocyanate reactive compound comprising an acid functional group and at least two isocyanate reactive groups selected from the group consisting of a hydroxy, a primary amino, a secondary amino, and combinations thereof; neutralizing the isocyanate reactive compound (iii) with a neutralizing agent comprising an amine group; reacting the isocyanate terminated prepolymer with at least one chain terminating agent; dispersing the isocyanate terminated prepolymer in water; and reacting the isocyanate terminated prepolymer with at least one chain extending agent comprising an organic diamine selected from the group consisting of: ethylene diamine, 1,6-hexamethylene diamine, and 1,5-diamino-1-methyl-pentane, wherein the polyurethane polymer has a weight average molecular weight ranging from 40,000 to 60,000 g/mol, wherein the particle size of the polyurethane polymer molecules in the aqueous dispersion is less than about 2 microns, wherein the polyurethane polymer is non-crystalline, and wherein the aforementioned steps are conducted sequentially.