Patent ID: 8398191

Claim:
A continuous ink jet printer aqueous ink composition comprising pigment particles dispersed with a dispersant or self dispersing pigment particles without the need for a dispersant, from 0.5 to 8% by weight of humectant, and a polymer additive distinct from any dispersant used to disperse the pigment particles, wherein the polymer additive comprises a water soluble copolymer, having block or random segments comprised of styrene and acrylic monomers, where the average molecular weight of the polymer additive is greater than 1000 and the polymer additive is present in an amount effective to stabilize the ink composition against shear induced agglomeration caused by pumping the ink composition through a continuous ink jet printing fluid system wherein the dispersed pigment particles are present at from 1 to 10 wt %, the styrene-acrylic copolymer is present at from 0.1 to 3 wt %, and the polymer additive is present at a weight ratio of from 1:10 to 1:3 relative to the dispersed pigment.