Alkaline Hydrolysis Kinetics and Physico-Chemical Properties of Acrylic Copolymers Based on Acrylic Acid, Its Esters and Vinyl Acetate
Kinetic regularities of the alkaline hydrolysis of copolymers of methyl acrylate, butyl acrylate, vinyl acetate and acrylic acid of several chemical compositions under various conditions were studied by IR spectrometry. The initial rate of alkaline hydrolysis and the limiting conversion degree were shown to increase with increasing concentrations of the components of the reaction mass and temperature. The methyl acrylate units in the copolymer macromolecules hydrolyze at a higher rate than the butyl acrylate ones, while the vinyl acetate units do not participate in the alkaline hydrolysis reaction in aqueous medium. Alkaline hydrolysis of acrylic copolymers taking place, the -COO - groups, along with the retarding effect, accelerate the reaction of neighboring units by the anchimeric assistance mechanism, thereby partially compensating for the general effect of slowing down the reaction. During the reaction of alkaline hydrolysis, the relatively low-polar initial copolymers convert into polyelectrolytes with a change in the macromolecular composition and with a significant increase in the viscosity of the system. During alkaline hydrolysis, the dynamic viscosity reaches up to 120 mPa∙s at a polymer concentration of about 2 wt.%. In an aqueous-alcoholic medium, due to the reactional availability of all functional groups, hydrolysis rate of the copolymer with vinyl acetate units increases because of alcoholysis of these vinyl acetate units.