Room temperature curable silane-terminated polyurethane dispersions

A method of making a silyl-terminated polyurethane in an aqueous dispersion comprising the steps of

• (a) reacting a mixture comprising:
• (i) a polyol component comprising a compound having two isocyanate reactive functional groups and optionally a compound having greater than two isocyanate reactive functional groups, each isocyanate reactive functional group having at least one active hydrogen;
• (ii) a water-solubilizing compound, wherein the water solubilizing compound possesses at least one water solubilizing group and at least one isocyanate reactive functional group, each isocyanate reactive functional group containing at least one active hydrogen;
• (iii) a polyisocyanate component comprising a compound having two isocyanate groups and optionally further comprising a compound having greater than two isocyanate groups;
• (iv) optional polar organic coalescing solvent;
• and
• (v) optional catalyst;
• at a sufficient temperature in order to facilitate reaction of the mixture to form an isocyanate-terminated polyurethane prepolymer;
• wherein the ratio of the isocyanate groups of the polyisocyanate component to the water solubilizing groups of the water solubilizing compound is such that the prepolymer can provide a stable dispersion upon combination with a water phase;
• and
• (b) preparing a stable silyl-terminated polyurethane dispersion by combining, under sufficient agitation and at a sufficient temperature and pH, the isocyanate terminated polyurethane prepolymer prepared according to the step of element (a) with elements comprising:
• (i) deionized water;
• (ii) an isocyanate reactive silane compound having at least one active hydrogen;
• and
• (iii) a salt forming compound selected from the group consisting of basic salt forming compounds and acidic salt forming compounds, wherein the salt forming compound is selected such that the salt forming compound is reactive with the water solubilizing group in the water solubilizing compound;
• wherein some or all of the salt forming compound is alternatively added to the mixture of step (a) prior to or during reaction, or to the isocyanate terminated polyurethane prepolymer prior to the combination of the isocyanate terminated polyurethane prepolymer with the water;
• further comprising a chain extender component as at least one of component (a)(vi) or (b)(iv), wherein the chain extender component comprises a difunctional chain extender having two isocyanate reactive functional groups and optionally a polyfunctional chain extender having at least three isocyanate reactive functional groups, each isocyanate reactive functional group having at least one active hydrogen;
• wherein sufficient polyisocyanate component is included in step (a) to provide an excess, on an isocyanate equivalent basis, of about 1.4 to about 4 times the combined active hydrogen equivalent of the isocyanate reactive functional groups of the polyol component, the water-solubilizing compound, and the chain extender component, if present as component (a)(vi);
• and
• wherein a sufficient amount of the chain extender component and the isocyanate reactive silane is present relative to excess polyisocyanate component such that the active hydrogen to isocyanate group ratio is about 0.85:1 to about 1:1;
• and wherein the optional polar organic coalescing solvent of element (a) (iv) can optionally be added to the water prior to the formation of the dispersion.