Process of making a vinyl ester based polymer latex composition

An emulsion polymerization process for producing a vinyl ester based polymer latex in an aqueous medium, said polymer comprising polymerized units of:

• (a) 40-95.3 wt. % vinyl ester monomer
• (b) 5-30 wt. % ethylene monomer
• (c) 1-10 wt. % post-crosslinking monomer,
• (d) 0.2-2 wt. % vinyl sulfonate monomer, and
• (e) 0.5-2 wt. % unsaturated carboxylic acid monomer,
• based on the total weight of monomers,
• wherein the process is carried out substantially in the absence of any added protective colloid and in the presence of from 0 to 1.0 wt. % of surfactant, based on the total weight of the monomers,
• wherein the process comprises
• (i) a first stage of providing an initial reactor charge comprising an aqueous phase comprising
• a) 10-30 wt. % of the vinyl ester monomer, based on total weight of vinyl ester monomer,
• b) at least 50 wt. % of the ethylene monomer, based on total weight of ethylene monomer,
• c) 5-25 wt. % of the post-crosslinking monomer, based on the total weight of post-crosslinking monomer, and
• d) 50-100 wt. % of the vinyl sulfonate monomer, based on total weight of vinyl sulfonate monomer, and
• (ii) a second stage of feeding any remaining monomers and optionally a polymerization initiator system in one or more feeds to the initial charge,
• wherein the vinyl ester polymer latex has a solids content of at least 20 wt. %.