Ultrafiltration and microfiltration membranes in latex purification by diafiltration with suction

Operation conditions of diafiltration with suction in purification of poly(glycidyl) methacrylate latex from sodium tetraborate and emulsifier were studied in a batch process using ultrafiltration blend polysulfone/poly(vinylpyrrolidone) and microfiltration Synpor(R) membranes. Intensity of permeate suction was controlled by changing the pumping rate at fixed cross-sections of the inlet tubes in both the retentate and permeate lines. An optimum value of flow rate was determined for each membrane type to ensure the best purification efficiency. Operating at this flow rate prevented not only undesirable dilution of the latex with osmotic water but also ensured the highest membrane permeability to solutes without cake formation on the membrane surface. It was shown that 92% degree of latex purification could be obtained by 8-h suction diafiltration with Synpor membrane having the pore entrance sizes close to nanoparticle dimensions. The possibility of complete purification of GMA nanoparticles from impurities using the hybrid membrane process combining dialysis followed by suction diafiltration with microporous membranes, and ultrafiltration with an appropriate membrane is discussed. (C) 2002 Elsevier Science B.V. All rights reserved.