PROCESS FOR MAKING PARTICULATE COMPOSITIONS

摘要

There is described a process for producing a particulate composition comprising the steps of: (a) forming a first dispersion comprising first particles stabilised in a first fluid by first species; (b) optionally the step of forming a second dispersion comprising second particles stabilised in a second fluid, miscible with the first fluid, by second species; (c) after (or simultaneously with) the optional step of mixing the first and second dispersions together if the second dispersion was formed from step b); inducing association between the dispersed particles to form clusters; and (d) binding together the particles within the clusters; characterised in that the first and/or second particles comprise at least one polar functional group to facilitate the binding of the particles in step (d). Preferably the polar group is other than an acid group, more preferably comprises at least one hydroxy group, non-acidic polar group and/or non-basic polar group, most preferably comprises one or more hydroxy and/or ether groups (e.g. an optionally polymeric alkylene glycol alkyl ether). A preferred embodiment of the process comprises mixing together two aqueous dispersions of particles (e.g. pigment particles and particles of hydroxy functional latex polymer). The dispersions are stabilised with surfactants. Association of the particles into clusters is induced by known means (e.g. heating and stirring) and the clusters are grown by aggregation into loose matrices which are more fused together to form particles which can be used in electroreprographic toners.