No abstract

No abstract

SynopsisIn the present article the kinetics of polymerization of vinyl acetate in suspension up to high conversion was studied. The molecular weight distribution and the side chain branching of polyvinyl acetate produced were examined with respect to micro and macro mixing as well as to reactor type. The following results were achieved: the time-activity curves of the polymerization can be described up to high conversions considering the exponential increase in viscosity of the polymerizing system and combining the viscosity with rate constants of the polymerization. The change of volume of the polymerizing system has no significant influence on kinetics. The narrowest molecular weight distribution of the poly(viny1 acetate) produced was achieved when polymerizing in the homogeneous continuous stirred tank reactor while the broadest molecular weight distribution was observed in the segregated continuous stirred tank reactor. The batch reactor and the flow tube reactor produce polymers with molecular weight distributions lying in between. Considering the side chain branching, another order was found. The batch reactor and the tube reactor show the lowest side chain branching, the homogeneous continuous stirred tank reactor shows a larger one and the segregated continuous stirred tank reactor shows the largest. Possible reasons for the different behavior of the different reactors are discussed. The degree of segregation was determined by experiments. EXPERIMENTALVinyl acetate (Hoechst AG, polymerization grade) used for the polymerization was rectified in a large column and stored at low temperature. Dicyclohexyl peroxidicarbonate (P1652, Peroxid Chemie) was used as initiator and 2,2-diphenyl-l-pikryl-hydrazyl (DPPH) (Fa. Fluka) was used for stopping the reaction after sampling. The dispersion agent utilized was partly saponified poly(viny1 acetate) (Mowioll8-88, Hoechst AG). Tertiary butanol (Bayer AG) was used as solvent for the polymerization in solution because this solvent has the smallest transfer constant of a poly(viny1 acetate) radical to a solvent molecule.Unless mentioned otherwise, the volume fraction of vinyl acetate to water was 0.12 to 0.25, and the initiator concentration was 0.5 wt % related to the monomer. For the polymerization in solution, 15 wt % monomer was solved in tertiary butanol and the same monomer to initiator ratio was chosen.For polymerization, a 1.5 1 thermostatic stirred tank reactor (ratio height/ diameter = 2.5) with a blade stirrer (stirrer diameter to reactor diameter 1:3, centrosymmetrically arranged one-third away from the bottom of the vessel) of 600 rpm for the polymerization in suspension was used. During the continuous process, feeding was put in through an injector at the bottom of the vessel. Outlet and sampling took place in the upper part of the reactor. All experiments were

SynopsisThe free radical copolymerization of acrylamide with three of the most commonly used cationic comonomers diallyldimethylammonium chloride, dimethylaminoethylmethacrylate, and dimethylaminoethylacrylate, the latter two quatemized with methyl chloride, was investigated. The polymerizations were carried out with azocyanovaleric acid and potassium persulfate over the temperature range ,45-60°C. The copolymer reactivity ratios were determined with the errorin-variables method Using residual monomer concentrations, measured by a Nalco HPLC method.This combination of estimation procedure and analytical technique has been found to be superior to any methods used previously for the estimation of reactivity ratios for cationic-acrylamide copolymers.

No abstract