Aqueous polyurethane dispersions
AssigneeE. I. Du Pont de Nemours and Company
InventorHarry W. Wolfe, Jr.
Life of this patent
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Abstract
A water-based polyurethane dispersion is prepared by mixing an aliphatic diisocyanate with three critical active hydrogen compounds, to form a prepolymer containing carboxyl groups and free isocyanate groups, then dispersing the prepolymer in an aqueous medium containing a tertiary amine, which converts the carboxyl groups to carboxylate ions, and a diamine, which chain-extends the prepolymer through its --NCO groups. These aqueous dispersions are storage-stable for at least several months and are useful in many coating applications, among others, for coating textile materials.
Claims7
A composition obtained by mixing an isocyanate-terminated, carboxyl group-containing prepolymer made by reaction of (A) 1 equivalent of an aliphatic diisocyanate with (B) total 0.6-0.8 equivalent of the following active hydrogen compounds:
- (a) .alpha.,.alpha.-dimethylolacetic acid or a homologue thereof,
- (b) a polymeric glycol selected from poly(alkyleneoxy) glycols and polyester glycols having a weight average molecular weight of about 400-3000, and
- (c) N,N'-dicyanoethylpoly(propyleneoxy)diamine having a number average molecular weight of about 200-2000;
- the amount of component (a) being about 0.08-0.25 hydroxyl equivalent per 100 g of total weight of all the reactants A and B, and the relative mole proportions of compounds (b) and (c) being about 30:70 to 70:30,
- with an aqueous solution of a sufficient amount of a tertiary amine free of substituents reactive with isocyanate groups to convert substantially all the carboxyl groups of the prepolymer to carboxylate ions, then chain-extending the prepolymer with about stoichiometric amount, based on free isocyanate groups, of a diamine having at least one hydrogen attached to each nitrogen atom.
Dependencies are inferred from the claim text.