Water purifying latex binder

In a process for the manufacture of felts from slurries of fibers containing water-soluble metal salts, the steps consisting essentially of:

• (a) forming an aqueous slurry of said fibers containing metal ions in solution;
• (b) forming a substantially surfactant-free polymer latex by copolymerizing styrene and a diene monomer, optionally substituted with methyl, in the presence of a persulfate catalyst at a strongly acid pH;
• (c) adding to said latex an unsaturated carboxylic acid, maintaining said strongly acid pH and polymerizing said carboxylic acid on the surface of said latex in an amount of at least about 0.5% by weight of said polymer;
• (d) adding the acidic, carboxylated latex of step (c) to said slurry with agitation in an amount sufficient to bind said metal ions by ion exchange;
• (e) mixing the slurry of step (d) for a period sufficient to effect ion exchange between the carboxylated latex and the metal ions in said slurry to demetalize the water of said slurry;
• (f) removing water from said fibers and said latex in said slurry to form a felt and
• (g) recycling said demetalized water to step (a) to provide the dilution required for slurry formation in a closed-process water system.