SYNTHESIS AND CHARACTERIZATION OF NEW STRUCTURED LATICES FOR IMPROVEDADHESION TO POLYESTER FILMS

The paper describes the synthesis, in an emulsion polymerisation proce ss, of an acrylic copolymer, poly(methyl methacrylate-co-ethyl acrylat e), in the presence of a hydrophilic polyester. This polyester has a s tructure close to that of poly(ethylene terephthalate) (PET) but is ma de hydrophilic by sulphonate-bearing moieties. It was specially design ed to promote the adhesion of latex films to PET. In water, it forms a ggregates with a mean diameter of 20 nm. These aggregates act as seed particles and the synthesis proceeds like an inverted core-shell emuls ion polymerisation. The hydrophilic polyester forms the main component of the shell of the final latex particles. The acrylic copolymer is l ocated mainly in the core. Despite the strong incompatibility between the two polymers, they mix to a certain extent, as clearly shown by th e analysis of the mechanical properties of the latex films. This unexp ected mixing is due to the synthesis procedure. The acrylic monomers a re added slowly and polymerise as soon as they reach the seed particle s, before having time to completely phase-separate from the polyester. Knowledge of the particle and latex film structure is used to interpr et adhesive properties of the latex films.