Fine particle, high concentration, polyisocyanate polyaddition/polyurethane-urea polyols

A method of producing a polymer polyol dispersion, the method comprising:

• forming a first composition by providing at least one polyol and providing isocyanate-reactive seed particles in an amount less than about 5% by weight of the at least one polyol, the suspended seed particles exhibiting a chemical reaction when combined with an isocyanate and having maximum particle diameters of less than 5 μm;
• adding to the at least one polyol at least one co-reactant that has an equivalent weight of up to 400 and at least one active hydrogen attached to a nitrogen or oxygen atom, the at least one co-reactant being added to the at least one polyol in a concentration between 5% to 15% by weight, the at least one polyol, the isocyanate-reactive seed particles, and the at least one co-reactant forming a second composition;
• and
• adding at least one polyisocyanate to the second composition to form the polymer polyol dispersion having a solids content of at least 15% of the weight of the polymer polyol dispersion, the at least one polyisocyanate reacting to form at least one of a polyurea, polyurethane, and polyurethane-urea particle population in the at least one polyol without the addition of any catalysts comprising tin.