Flocculation of Polystyrene Latex by Polyacrylamide-Copolyethylene Glycol

Comb copolymers with long polyacrylamide (PAM) backbones and short polyethylene glycol (PEG) pendant chains were used to flocculate aqueous latex in conjunction with a phenol-formaldehyde resin. Flocculation efficiency was determined as a function of molecular weight (MW), PEG content, and PEG pendant chain length. The results indicated that high copolymer MW was crucial. More than 70% of latex removal was achieved by copolymers with MW higher than 3 million. Moreover, only 0.3 to 0.8% (mol) of PEG acrylate and methacrylate esters were required to be incorporated in the high-MW copolymers. The minimum PEG pendant chain length for successful removal of the latex was as low as 9 ether repeat units. An empirical equation to relate the flocculation efficiency and the copolymer structures has been derived. The copolymers exhibited flocculation performance similar to that of polyethylene oxide (MW > 4 million). However, the copolymers did not exhibit a loss of flocculation ability with time.