Preparation of polyurethaneurea (PUU) uniform spheres by SPG membrane emulsification technique

Uniform polyurethaneurea (PUU) spheres were prepared from 20-40 wt % uretha ne prepolymer (UP) solution of xylene. Uniform droplets were formed with th e Shirasu porous glass (SPG) membranes of 1.42, 5.25, and 9.5 mu m pore siz e, dispersed in an aqueous phase with dissolved stabilizers, and allowed to stand for the chain extension at the room temperature with diamines that w ere added after the emulsification. The reaction progressed rapidly by an a ddition of ethyl acetate to the aqueous phase, promoting the diffusion of d iamines into the droplets. The reaction of -NCO groups with water did not h amper the emulsification process, which normally occurred in 1 to 2 h, yiel ding stable droplets with the coefficient of variation around 10%. No insta bility or coagulation occurred, while standing for the chain extension, and solid, spherical PW particles of 5-20 mu m were obtained after removal of the solvent. (C) 2000 John Wiley & Sons, Inc.