Reactant ratio, viscosity change

Figure 9. Effect of the initial reactant ratio on the viscosity change during reaction between styrene-hydroxyethyl methacrylate copolymer (2.2 mole % HEM A) and hexamethylene diisocyanate in toluene at 80°C. Polymer concentration 0.134% (gram/dl.) [NCO]0 [OH]0 = 0.5, 1.1, 4.0, 18.4, 115, and 4000 for Curves IS, respectively...

Quantitative analysis has shown that when there are major increases in viscosity from the initial reactants to the final products, the main characteristics of the flow pattern are determined by the ratio of these viscosities,205 and this effect dominates when there are large changes in viscosity at relatively low degrees of conversion. 

The effects of reaction time and initial ratio of reactant concentrations are illustrated in Figures 9-11. In all cases increasing the isocyanate concentration over a wide range increased the change in viscosity. Comparison of Curve 5 (copolymer 2.2 moles % HEMA) in Figure 10 with... 

These observations can be explained by the influence of the liquid flow density and viscosity on the turbulence level, defined in the first approximation by the Reynolds Number (Re). In particular, an increase of the density value for the reactant flow in motion, leads to an increase of the Re values, i.e., the hydrodynamic similarity of the system changes. In order to form the quasi-plug flow mode in the reactor after a change in the reactant density, it is necessary to reach the previous Re values, which may be possible due to a decrease in the linear rate of the liquid motion V, or due to a decrease of the reactor diameter D, and increase of the system viscosity. The hydrodynamic similarity of the system and the quasi-plug flow mode are reached due to the decrease of the V1/V2 ratio (a decrease of the axial flow rate). In much the same way, it is possible to explain the influence of viscosity on the conditions of plane front formation. 

The change of potassium chloride aqueous solution concentration has a similar influence on the granulometric composition of the antiagglomerator (Figure 4.20). However, in this case, the dependencies are smoother, without any prominent bends, and the particle diameter decreases with the growth of the initial reactant concentration. This is obviously related to the increased viscosity of potassium stearate, which also explains the extremely low value of the reactant concentration of no more than 15 wt%. At a fixed ratio of the initial reactant concentration, an increase of the solid-phase content of the obtained calcium stearate suspension, results in the growth of the particle size. In all cases, particles of minimal experimental diameter can be obtained in the reaction within a tubular turbulent reactor of diffuser-confusor design. 

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