Hydroxyethyl Cellulose Grafted Acrylic Latex

An emulsion polymerization method to graft hydroxyethyl cellulose (HEC) to acrylic polymer comprising the steps of

• providing and neutralizing acrylic monomers in an emulsion container to form a monomer pre-emulsion;
• polymerizing the acrylic monomers at a first feeding rate;
• controlling the first feeding speed so that an average size (mV) of an acrylic core is above about 160 nm;
• adding the HEC to water to form an HEC solution;
• mixing about 10% to about 40% of the monomer pre-emulsion with the HEC solution after the acrylic polymer conversion reaches about 90% to about 60%;
• feeding the HEC/monomer mixture to the reactor at a second feeding rate;
• wherein the average particle size (mV) of acrylic core is controlled between about 160 nm and about 280 nm at the end of about 90% to about 60% acrylic polymer conversion before the HEC solution is added;
• and
• wherein the HEC-grafted acrylic polymer contains less than about 700 ppm of gels.

An emulsion polymerization method to graft hydroxyethyl cellulose (HEC) to acrylic polymer comprising the steps of

• providing the HEC in a reactor water phase to form an HEC solution;
• providing and neutralizing acrylic monomers in an emulsion container;
• adding part of the acrylic monomer emulsion to HEC solution to form seeds;
• feeding the remaining acrylic monomers at a first speed;
• controlling the first feeding speed so that less than 28% monomer conversion in the first hour, and less than 68% monomer conversion after two hours;
• feeding the acrylic monomers at a second speed, wherein the second feeding rate is higher than the first feeding rate;
• and
• wherein the HEC-grafted acrylic polymer contains less than about 700 ppm of gels.

An emulsion polymerization method to graft hydroxyethyl cellulose (HEC) to acrylic polymer comprising the steps of

• providing the HEC in a reactor water phase to form an HEC solution;
• providing a seed monomer emulsion to the HEC solution;
• feeding the acrylic monomers to the HEC solution;
• controlling the solid content to be less than about 30% solids and controlling the particle size distribution to be uni-modal distribution;
• cooling the monomer emulsion;
• reducing the residual monomers;
• adjusting the pH of the emulsion to between about 8.0 and about 8.8;
• adding surfactants and initiator to the emulsion;
• adding additional monomer emulsions;
• wherein the average particle size (mV) of acrylic core is controlled between about 160 nm and about 280 nm;
• and
• wherein the HEC-grafted acrylic polymer contains less than about 700 ppm of gels.