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Thesis for the Degree of Master of Science

 

Year 1998
Mila Nieminen-Suuronen

The Dynamic Model of Resin Process


The aim of the thesis was to create a kinetic model for a phenol-formaldehyde resin process to quantify the behaviour of the reactor temperature and the molecular weight distribution of the phenol-formaldehyde resin as a function of time. In this study the kinetic model is being developed and it is going to be used for estimating the stopping time of the batch.

Energy and material balances are the basis of the model. The material balances were formulated for formaldehyde, different size molecules and for methylolgroups in different size molecules. There were six parameters to be quantified: the reaction rate constants for methylolation and condensation at the reference temperature, both the activation energies and the reaction enthalpies for methylolation and condensation. Matlab was used for solving the model equations. The parameters were estimated by comparing the measured temperature with the calculated temperature of the reactor and by using the results of gel permeation chromatography.

It was assumed that there are neither ortho-ortho-bridges nor ether-bridges and that the condensation happens between two methylolphenols by freeing water and formaldehyde. It was hypothesized that methylolation obeys first order of reaction and condensation second. It was also hypothesized that the reactor is well mixed, which is a reasonable assumption according to previous mixing studies. Density, viscosity, specific heat and reaction heats were assumed to be constant during the batch.

The results show that the reactor temperature of the model compares well with that of the real process. The temperature rise at the end of the batch can be explained by the condensation mechanism. According to the model there is too much formaldehyde left at the end of the batch. This residual free formaldehyde makes the model temperature go up. Thus, it appears that condensation can happen without freeing formaldehyde. The calculated molecular weight distribution agrees well with measurements from the real process. The estimated reactor temperature as a function of time can be affected by changing the values of the model parameters. The changes made in the parameters make the estimated reactor temperature act as expected. Thus, the kinetic model is a good starting point for modelling the stopping time of the phenol-formaldehyde resin batch.


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