Novel two‐stage phenol–formaldehyde resol resin synthesis

Abstract

The synthesis of phenol-formaldehyde resol resins was carried out in two stages to facilitate the start of a conventional batch process. In the first stage, the starting material solution was preprocessed in a continuous-flow stirredtank reactor with a 5-min residence time. In the second stage, synthesis was continued in a batch reactor. Samples were analyzed by titrimetric methods, gas chromatography, nuclear magnetic resonance spectroscopy, and differential scanning calorimetry. Most of the starting materials were consumed in the preprocessing reactor, which allowed better control of the reactivity of the prepolymer solution in the second stage. The methylolation and condensation reactions proceeded steadily during the production process in the batch reactor. The results of the study indicated that dividing a conventional one-stage batch process into two stages could facilitate the control of the initial stages of resol production.

Microwave-assisted synthesis and characterization of resole-type phenolic resins

“…The formed monomethylol derivatives (products A and B in Figure 1) might continue to react with formaldehyde forming two dimethylol and one trimethylol derivatives as shown in Figure 1. The formation of dimethylol and trimethylol derivatives were also seen by various workers in the past 11,[13][14][15][16][17][18][19] in their studies on phenolic resoles and their by-products.…”

“…The reaction between phenol and formaldehyde under alkaline conditions might proceed through the mechanism suggested by Zorba et al 10 According to them, the base-catalyzed hydration reaction of formaldehyde, in an aqueous medium, might form ethylene glycol. This concept of Zorba was, later on, considered by several workers [10][11][12][13][14][15][16] while synthesizing resoles under different sets of conditions. The reaction may be depicted as shown in Figure 1.…”

Novel Protocol for Resole Phenol Formaldehyde Resins Synthesis with Tubular Reactor and Characterization

“…The physical properties of the resole resin such as viscosity, solid content, pH, water dilutability (cloud point), and free formaldehyde were determined as per the standard method mentioned in the literature. [ 17,18 ] In the present work, the viscosity of the resin sample was determined by using a Brookfield AMETEK RV viscometer. The temperature of resole was kept at 25 °C and the readings were taken using a spindle number of 2 and 3.…”

“…This is a convenient measure to check the extent of reaction during lab scale synthesis as attested by earlier reports. [ 18 ] Hence, refractive index technique was used for tracking the PF reaction in the present work. However, the final viscosity was measured with a Brookfield viscometer.…”

Kinetics of hydroxymethyl phenols formation by in‐line FTIR spectroscopy

“…Temperature and pH conditions under which reactions of phenols with formaldehyde are carried out have a profound effect on the characteristics of the resulting products. [4][5][6] In this step of formaldehyde addition to phenol, where different hydroxymethyl phenols are formed, the molar ratio between phenol and formaldehyde is of crucial importance. [7][8][9] Mono-, di-, or tri-hydroxymethyl phenols are synthesized with a molar excess of formaldehyde (1 < F/P < 3) under alkaline conditions at low temperatures (below 608C) and they are stable at room temperatures, but are transformed into three-dimensional, crosslinked, insoluble, and infusible polymers by the application of heat.…”