|Recent Status of PVA Protective Colloid in Polymer Latices
Department of Materials Science, School of Engineering, The University of Shiga Prefecture, Japan
Nippon Gomu Kyokaishi,(2006),79(2),67-72 General Review in Japanese
Equal quantities (300 thousand tons) of vinyl emulsions and diene latices are produced in Japan. Main application fields are paints and pressure sensitive adhesives for acrylics, adhesives for vinyl acetate (VAc) and its copolymers, and clay-coating binders and rubber in ABS resin for dienes. As stabilizers, PVA for VAc and its copolymers, and emulsifiers for acrylics and rubber for ABS are utilized.
PVA affords mechanical stability and low-thixotropy to the emulsions and strengthening effect and poor water resistance to the emulsion films. These effects are arisen from the canal-like morphology of PVA in the films. PVA has not been utilized in emulsions other than those of VAc and its copolymers. This has been attributed to the weak ability in grafting of acrylic and diene monomers onto PVA. In the model experiment using a very low concentration of MMA, which corresponds to the initial stage of emulsion polymerization of the PVA systems, it was clarified that grafting onto PVA takes place significantly yielding new polymer particles, and that there are almost no difference between VAc and MMA systems. Problem seems to exist after the consumption of PVA freely soluble in water. Recently,
noticeable studies were reported: in the emulsion polymerizations of acrylics and styrene/butadiene in the presence of ethanol, continuous addition of monomers emulsified with PVA afforded successfully the stable emulsions.
Polyvinyl alcohol (PVA), Protective colloid, Grafting, Emulsion, Latex, Poly (vinyl acetate) (PVAc)