Continuous Reactions
LensContinuous Reactions in the Concentrated Phase
Figure 1: The conventional process for making HMM requires a large excess of formaldehyde. A new process based on the LIST KneaderReactor, in contrast, is almost stoichiometric.

Hexamethylol melamine (HMM) is produced from melamine (C3N3(NH2)3) and formaldehyde (CH2O). The conventional process requires 7 – 10 mol of formaldehyde per mol of melamine, compared to the stoichiometric ratio of 6:1. The reaction product is a paste containing 40 – 70 wt% water and unreacted formaldehyde.

Raw HMM from the conventional process has poor flow properties and tends to harden, making further processing difficult. The presence of free formaldehyde also creates an environmental and safety hazard. As a result, drying of the raw HMM is difficult, expensive, and creates formaldehyde vapor that must be collected and disposed of safely.

LIST KneaderReactor technology has been used to develop a new continuous process for the combined synthesis and vacuum drying of HMM (Figure 3). This reaction is nearly stoichiometric, so much less formaldehyde needs to be handled and recovered. Most importantly, the final product discharged from the drying stage is a free-flowing powder that is easy to handle and contains very low levels of formaldehyde and water.

Process intensification in practice:

LIST KneaderReactor Technology is smaller, simpler, flexible, economical, efficient, and safe.