SynopsisBatch production of urea-formaldehyde resins at temperatures up to 100°C takes several hours for completion. Reduction of the batch time may be possible with the higher reaction rates obtained at higher temperatures and increased pressures. In order to investigate this possibility, an experimental technique to obtain the necessary kinetic data, without loss of formaldehyde by evaporation, was developed. The results are compared with earlier low-temperature data extrapolated to the present range of interest. The results were interpreted on the basis of the successive reaction of two or three molecules of formaldehyde with a molecule of urea. Rate EquationsIn order to carry out the chemical engineering design procedure for a reactor producing UF (urea-formaldehyde) resins, appropriate rate equations would be required of the formwhere r = rate of appearance or disappearance of a chemical, c = concentration of that chemical, and t = time elapsed from start of reaction.It has been established1 that the combination of urea and formaldehyde begins with a series of addition reactions2 followed by condensation reactions3; that the speed and extent of reaction are dependent on temperature, pH, and U:F ratio, although the reaction rate is essentially constant in the pH range 4-9 at constant temperature4 and that UF3 is produced in significant quantities only at low U:F ratio^.^ Therefore, since the commercial process usually involves U:F molar ratios between 1:1.33 and 1:2.2, within the pH range 4-9, it is reasonable to assume initially that the reactions taking place are UF1+F+UF2so that the rate equations become