On‐line acoustic attenuation spectroscopy of emulsions stabilized by vinyl alcohol–vinyl acetate copolymers: a model system for the suspension polymerization of vinyl chloride

Abstract

BACKGROUND: Poly[(vinyl alcohol)‐co‐(vinyl acetate)] (PVA) copolymers obtained by partial hydrolysis of poly(vinyl acetate) are currently used as industrial stabilizers in the suspension polymerization of vinyl chloride monomer (VCM). Their molecular characteristics, mainly the average degree of hydrolysis (DH) and average degree of polymerization (DPw), have a major influence on the monomer droplet size and the properties of the final poly(vinyl chloride) resin. RESULTS: The average droplet size and size distribution of chlorobutane/water emulsions, as a model system for VCM/water emulsions, were studied using acoustic attenuation spectroscopy on‐line with an agitated laboratory reactor. The emulsions were stabilized by PVA with DH values between 73 and 88 mol% and DPw values between 450 and 2500. The effects of agitation speed, stirring time and concentration of the PVA copolymers were investigated. An attempt was made to correlate the interfacial tension and the droplet size. CONCLUSION: On‐line acoustic spectroscopy appears to be a suitable technique for the real‐time control of the droplet size of monomer suspensions. The advantages and limitations of the technique are outlined. The validity and the application limits of the commonly cited correlation between the droplet size and the Weber number are established for polymeric surfactant‐stabilized emulsions. Copyright © 2009 Society of Chemical Industry

Effect of poly(vinyl alcohol-co-vinyl acetate) copolymer blockiness on the dynamic interfacial tension and dilational viscoelasticity of polymer–anionic surfactant complex at the water–1-chlorobutane interface

“…[11][12][13] As the interfacial characteristics of a system are directly correlated to the conformation of the adsorbed emulsier at the interface, in the following, the interfacial tension was determined for all samples in the absence and in the presence of SDS.…”

Turbulent liquid–liquid dispersion in SMV static mixer at high dispersed phase concentration

“…Turbiscan on-Line (Buron et al, 2004;Pizzino et al, 2009) -Measurement of the backscattered intensity percentage -No dilution -High dispersed phase ratio -Non intrusive -Only the d 32 -Knowing the dispersed phase volume fraction to obtain the d 32 (and inversely) Acoustic attenuation spectroscopy (Boscher et al, 2009) -Based on frequency -dependent extinction of ultrasonic waves arising from particles -Droplet from 1mm to 3mm -Concentrated systems -On-line information: droplet characteristics and volume fraction of dispersed phase -Difficulty to calibrate the system Organics, Tween80 from Panreac, Glycerol and Toluene from Gaches Chimie and PVA from Nippon Gohsei. Properties of the different fluids are summed up in Table 2, where are also reported the density and viscosity ratio (respectively, r d /r d and m d /m c ), and the equivalent density of each system for a 0.25 dispersed phase concentration in volume.…”

Thermal Cloud Point Fractionation of Poly(vinyl alcohol-co-vinyl acetate): Partition of Nanogels in the Fractions

“…The molecular characteristics of PVA's, mainly their polymerization degrees DPn , DPw and the average degree of hydrolysis DH , in general in the range of 70 to 90 mol%, have a major influence on the monomer droplet size, the dispersion stability and on the properties of the final PVC resins [3,4].…”

“…The evolution of the size average (Dv) of different fractions of samples PVA-73-650 and PVA-73-685 at a SDS concentration of 1 and 5 wt% respectively with respect to PVA. PVA-73-685 1% SDS 5% SDS 1% SDS 5% SDS F 1 19.3 ± 0.9 7.6 ± 0.7 16.6 ± 0.3 7.1 ± 0.5 F 2 16.2 ± 0.7 7.4 ± 0.5 13.8 ± 0.7 6.9 ± 0.6 F 3 14.7 ± 0.4 6.9 ± 0.3 14.1 ± 0.7 7.7 ± 0.3 F 4 8.3 ± 0.3 7.8 ± 0.3 9.3 ± 0.2 7.6 ± 0.3…”