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AssigneeImperial Chemical Industries PLC
InventorNeal St. John Williams
Estimating the term…
A process for making poly(urethane-urea)/addition polymer composite particles which avoids the need to use a highly viscous solution of a prepolymer for the poly(urethane-urea). The process comprises dissolving diol and di-isocyanate in addition polymerisable monomers and allowing them to co-react but for only long enough to form a precursor for the prepolymer which is of a lower molecular weight than the prepolymer so that the precursor forms a solution of much lower viscosity. This lower viscosity solution is then dispersed in water to give droplets in which the co-reaction continues and completes the formation of the prepolymer whilst water diffuses into the droplets and causes chain extension to create the poly(urethane-urea) particles. The addition polymerisable monomers in the dispersed droplets spontaneously diffuse into the poly(urethane-urea) particles where they are subjected to a conventional free radical addition polymerisation process whereupon composite the poly(urethane-urea)/addition polymer particles are formed. The composite particles can be obtained as stable aqueous dispersions optionally containing less than 3 wt % organic solvent and over 40 wt % of the composite particles.
A process for making poly(urethane-urea)/addition polymer composite particles which may optionally carry some ionic carboxylate groups, which process involves
A process according to any one of the preceding claims wherein the hydrophobic monomer solution is dispersed in the water under conditions of shear so high as to create nanosized droplets of monomer solution having a number average diameter of from 40 to 400 nm.
A process according to any one of the preceding claims wherein the diol is dissolved in the hydrophobic solvent before the di-isocyanate.
A process according to any one of the preceding claims wherein the di-isocyanate is an aromatic di-isocyanate.
A process according to any one of the preceding claims wherein up to 5 mol % of the addition polymerisable monomer is hydroxyalkyl(meth)acrylate monomer.
A process according to any one of the preceding claims wherein up to 2.5 mol % addition polymerisable monomer is crosslinkable monomer.
Dependencies are inferred from the claim text.