Modeling and simulation of urethane acrylates synthesis. II. Kinetics of uncatalyzed reaction of toluene diisocyanate with a polyether diol

Abstract

Toluene diisocyanate reacts with poly(propylene glycol) during the synthesis of some urethane acrylate oligomers. The present work deals with kinetic studies and molecular characterization of the uncatalyzed bulk reaction of these two difunctional monomers. Back titration and H 1 -NMR are used to follow the reaction of the different isocyanate groups with an alcohol group belonging to poly(propylene glycol) and to allow a good description of the urethane groups evolution. The global reaction rate as well as that of each individual isocyanate group are well described by a second-order equation. Kinetic constants were calculated by using the software SIMUL-BATCH ® . The reaction of two difunctional monomers leads to the formation of oligomers of different polymerization degrees, opposite to the reaction of TDI with a monoalcohol. Thus, another approach was developed to characterize the oligomers by size exclusion chromatography and to calculate the molecular weight distribution by using a combination of kinetic and probabilistic arguments.

New insight into the kinetics of diisocyanate‐alcohol reactions by high‐performance liquid chromatography and mass spectrometry

“…The facts that the para-isocyanate goup is more reactive than the ortho one, and after carbamate formation the reactivity of the second isocyanate group decreases, are in concert with findings of previous investigations. 24,26,27 These observations can be rationalized as follows: the methyl group, due to its electronic and steric effect, deactivates the isocyanate group in the ortho-position more effectively than the one in the para-position. On the other hand, a replacement of an isocyanate group by a carbamate one decreases the reactivity of the other isocyanate group since the carbamate group less is electron-pulling substituent than the isocyanate group.…”

Structural investigations of toluene diisocyanate (TDI) and trimethylolpropane (TMP)-based polyurethane prepolymer

“…These reactions affect the molar mass distribution and final product properties such as curing dynamics and mechanical properties of segmented polyurethane in various ways [17,18]. The chemical structure of polyurethane prepolymer has been extensively studied by several techniques such as gel permeation chromatography (GPC) [19][20][21][22][23], nuclear magnetic resonance (NMR) spectroscopy [14,24,25] and mass spectrometry (MS) [26][27][28]. It is essential to thoroughly investigate the mechanism of urethane reactions and other side reactions to control the properties of the resulting polyurethane products, and most importantly, to obtain polyurethane prepolymer which could be purified through the thin film evaporator.…”

Uncatalyzed reactions of 4,4′-diphenylmethane-diisocyanate with polymer polyols as revealed by matrix-assisted laser desorption/ionization mass spectrometry

“…Proper selection of the isocyanate and the polyol components allows one to tailor the properties of the resulting PUs for various applications. [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] In most of these investigations the reaction was monitored using, e.g., titration method, 21,22 FT-IR spectroscopy, [23][24][25][26][27][28][29][30] rheological measurements 29,31 and sizeexclusion chromatography (SEC). Thus, due to the practical importance of PUs, the catalyzed and uncatalyzed reactions of different isocyanates with alcohols under various experimental conditions have been extensively studied from the early ages of the polyurethane industry.…”