Process for preparing aqueous dispersions of hybrid polyurethane particles
AssigneeDow Global Technologies LLC
InventorsBedri Erdem, Debkumar Bhattacharjee, Alan K. Schrock
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Abstract
Dispersions of hybrid polyurethane particles are made using miniemulsion techniques. An isocyanate-terminated prepolymer and a monomer are mixed and dispersed in an aqueous phase to form a dispersion of droplets. All droplets are polymerized and chain-extended in one step to form hybrid particles containing a polyurethane and a polymer of the monomer. This process provides a simple method of making hybrid particles, in which particle size and the number of particles is controlled in the mixing step. The hybrid particles often have a core-shell morphology, with the polyurethane being concentrated in the shell and the polymer being concentrated in the center of the particle.
Claims22
A process for making a polymer dispersion, comprising
- (a) forming a mixture of an isocyanate-terminated prepolymer substantially devoid of acid or ionic groups and at least one monomer having at least one site of polymerizable carbon-carbon unsaturation and which is liquid or solid at room temperature, the prepolymer being soluble in the monomer(s) at the relative proportions that are present;
- (b) dispersing the mixture into an aqueous phase under conditions sufficient to form an aqueous dispersion of a plurality of stabilized droplets that have an average diameter of no greater than about 1000 nm and contain both the prepolymer and the monomer(s), and
- (c) subjecting the dispersion from step (b) to conditions sufficient to polymerize the monomer(s) and chain-extend said prepolymer in a single step to form a plurality of hybrid polymer/polyurethane particles having an average diameter of no greater than about 1000 nm dispersed in said aqueous phase.
A dispersion of polymer particles in a continuous aqueous phase, wherein the polymer particles are hybrid particles of a polyurethane and a polymer of a monomer having at least one site of polymerizable carbon-carbon unsaturation, further characterized in that the polymer particles have an average diameter of less than about 1000 nm and exhibit a core-shell morphology on transmission electron spectroscopy, in which the particles have a core portion rich in the polymer and a shell portion that is rich in the polyurethane.
Dependencies are inferred from the claim text.