Method of making polyurethane powder

Claim 1

The method for preparing polyurethane resins directly in finely divided form from reaction of a first liquid reactant comprising at least one organic polyisocyanate with a second liquid reactant comprising at least one organic compound containing at least two groups having active hydrogen to form a solid reaction product, said first reactant being employed in amount relative to the amount of said second reactant to give a molar ratio of active hydrogen to --NCO in the range of from about 0.85:1 to about 1.5:1, said method comprising emulsifying said reactants with the aid of an organic polymeric surfactant as fine droplets of said first reactant and fine droplets of said second reactant in a continuous phase comprising an organic liquid inert to and less polar than said reactants an in which said reactants and said solid reaction product are substantially insoluble, said surfactant being present in amount of from about 0.1% to about 10% on the weight of emulsified insoluble liquid reactants, reacting said emulsified reactants by reaction between the droplets of said first reactant and droplets of said second reactant emulsified in said inert organic liquid under conditions of vigorous agitation to form fine particles of said polyurethane separable from said inert liquid by settling, and separating said particles from said inert liquid, the molecules of said polymeric surfactant having an average molecular weight of at least about 2,000, and having polar groups which associate with the surface of said droplets of emulsified insoluble reactants and with particles of said solid reaction product and less-polar groups which are solvated by the said inert organic liquid, the quantity and the balance of polar to less-polar groups of said surfactant relative to the polarities of said inert organic liquid, said insoluble emulsified reactants and said reaction product providing that the total association of less polar groups with said inert organic liquid is greater than the total association of the polar groups with said emulsified insoluble reactants and with said solid reaction product by an amount to ensure that said inert liquid will be the external phase, but is less than the amount which would interfere with formation of a fine emulsion of the insoluble liquid reactants in said inert organic liquid, coordinating (a) the intensity of said agitation; (b) the quantity and the balance of polar to less-polar groups of said surfactant in said emulsion and (c) the polarities of said inert liquid organic liquid, said emulsified insoluble liquid reactants and said reaction product to form a fine emulsion in which at least about 95% by weight of the droplets of said emulsified liquid reactants will be in the range of from 1 to 300 microns in diameter so that the particles of reaction product will settle, the association of said surfactant with said reaction product holding said surfactant on the surface of said particles of reaction product to impede agglomeration of said particles.

Claim 2

The method for preparing polyurethane resins directly in finely divided form from reaction of a first liquid reactant comprising at least one organic polyisocyanate with a second liquid reactant comprising at least one organic compound containing at least two groups having active hydrogen to form a solid reaction product, said first reactant being employed in amount relative to the amount of said second reactant to give a molar ratio of active hydrogen to --NCO in the range of from about 0.85:1 to about 1.5:1, said method comprising emulsifying said reactants with the aid of an organic polymeric surfactant as fine droplets of said first reactant and fine droplets of said second reactant in a continuous phase comprising an organic liquid inert to and less polar than said reactants an in which said reactants and said solid reaction product are substantially insoluble, said surfactant being present in amount of from about 0.1% to about 10% on the weight of emulsified insoluble liquid reactants, reacting said emulsified reactants by reaction between the droplets of said first reactant and droplets of said second reactant emulsified in said inert organic liquid under conditions of vigorous agitation to form fine particles of said polyurethane separable from said inert liquid by settling, and separating said particles from said inert liquid, the molecules of said polymeric surfactant having an average molecular weight of at least about 2,000, and having polar groups which associate with the surface of said droplets of emulsified insoluble reactants and with particles of said solid reaction product and less-polar groups which are solvated by the said inert organic liquid, the quantity and the balance of polar to less-polar groups of said surfactant relative to the polarities of said inert organic liquid, said insoluble emulsified reactants and said reaction product providing that the total association of less polar groups with said inert organic liquid is greater than the total association of the polar groups with said emulsified insoluble reactants and with said solid reaction product by an amount to ensure that said inert liquid will be the external phase, but is less than the amount which would interfere with formation of a fine emulsion of the insoluble liquid reactants in said inert organic liquid, coordinating (a) the intensity of said agitation; (b) the quantity and the balance of polar to less-polar groups of said surfactant in said emulsion and (c) the polarities of said inert liquid organic liquid, said emulsified insoluble liquid reactants and said reaction product to form a fine emulsion in which at least about 95% by weight of the droplets of said emulsified liquid reactants will be in the range of from 1 to 300 microns in diameter so that the particles of reaction product will settle, the association of said surfactant with said reaction product holding said surfactant on the surface of said particles of reaction product to impede agglomeration of said particles.