u2032 1 with r 1 u2550 h or ch 3 n 1 4 and n u2032 1 14 vinyl acetate styrene versatic esters acrylic acid methacrylic acid acrylamide ethylene glycol dimethacrylate and the like the cationic dispersions of the invention have a solids content of between 20 and 50 preferably between 40 and 50 and a particle size of between 50 nm and 300 nm with a mean particle size preferably of less than 100 nm they have very good compatibility with the starches liable to be used in the size press even at high temperature whether these are native starches weakly anionic starches or cationic starches they have a low viscosity preferably of less than 100 mpa s for a solids content of 41 they have very good stability over time very good mechanical stability and very good resistance to the freezing thawing cycle they confer very good hydrophobicity on the papers treated at treatment levels far below those of an equivalent anionic emulsion in particular they make possible the surface treatment of papers of test liner type intended for board packing where the papers are required to have very good hydrophobicity they also make it possible to use inter alia a starch and pigments which are cationic during the surface treatment of the paper and to obtain very good ink jet printability this is because the particles present in the printing inks are generally anionic and will attach more easily to the surface of the paper if cationic components are present processes for the treatment of paper by external or internal sizing are described in the applicational examples this example describes the process for the synthesis of an imide derivative of a styrene maleic anhydride copolymer denoted by sma dimethylpropylenediamine dmapa and.