BASF patents color effect polymer dispersion

February 11, 2011

Patent No. U.S. 7,776,237 B2
BASF has been granted a patent for a process which is comprised of forming a film from an aqueous emulsion of a polymer with core/shell structure, and then removing water from the aqueous film, thereby forming a polymeric film, wherein the polymeric film produces a visual effect upon reflection of electromagnetic radiation, and wherein the emulsion polymer is obtained by polymerizing monomers in at least one first stage (core monomers), then polymerizing mon­omers in at least one further, second stage (transition stage), and finally polymerizing monomers in a third stage which form a filmable shell (shell monomers), where, based on the percentage constitution of the monomer mixtures of the three stages, at most 30% by weight of the monomers of the first stage are identical with those of the third stage, and at least 5% by weight of the monomers of the second stage are identical with, respectively, those of the first and those of the third stage, and not more than 60% by weight of the monomers of the second stage are monomers absent in the first stage and also absent in the third stage, wherein the polymeric film is comprised of a matrix and discrete polymer particles distributed in the matrix, wherein the shells form the matrix and the cores form the discrete polymer particles.