Formaldehyde-free binder compositions for simultaneous warp sizing and coloration of filament yarns

An aqueous dispersion has an addition polymer (B) formed in situ on a sulfopolyester (A). The sulfopolyester (A) is formed as a polycondensation product of first and second reaction mixtures. The first reaction mixture includes at least about 70 mol. % of terephthalic acid or an ester thereof, and about 4-20 mol. % of a difunctional ester forming sulfomonomer containing at least one metal sulfonate group attached to an aromatic nucleus, wherein the functional groups are selected from the group consisting of hydroxyls, carboxyls and alkyl esters. The second reaction mixture includes at least two different glycols, at least about 20 mol. % of the second reaction mixture being ethylene glycol. The addition polymer (B) is formed in situ on the sulfopolyester (B) by polymerizing styrene monomer.