FEATURES OF MECHANISM OF GAS-LIQUID POLYAMIDATION IN FOAMY HYDRODYNAMIC MODE

The brief characteristics of the reaction system of pilot production of fatty-aromatic polyamides based on aliphatic diamines (acylated monomers) and dicarboxylic acid dichloroanhydrides (acylating monomers) by the method of gas-liquid polycondensation in a highly turbulized foamy hydrodynamic mode are described. Technological scheme and rational instrumentation of the technology of polyterephthalamides, the reactor unit (reactor-fibridator), which includes a two-stage reaction chamber and a gas phase generating chamber coaxially located under it, chemistry and operating principle of the facility are shown. The method combines the chemical processes of polyamidation with the physical processes of the reaction molding of polyamide fibrids or gas-structural elements used in the technology of gas-filled plastics. The reaction system of the method includes three structural units: a liquid phase (aqueous alkaline solution of aliphatic, cycloaliphatic and fatty-aromatic diamines), a gas phase (superheated vapours of aromatic and aliphatic dicarboxylic acid dichloroanhydrides, dispersed in a dynamic airflow or inert gas) and an interface (gas-liquid interface). Gas-liquid polyamidation is accompanied by phase formation: the reaction system during the process becomes three-phase system – the swollen polymer forms a solid mobile phase (target product), which acts as a foamy mode stabilizer, which allows technological process to proceed at optimal linear gas phase rates of 30–35 m/s (unlike classical two-phase foamy mode – 4 m/s). A polyamidation mechanism at the liquid-gas interface is proposed, which includes two versions of the process (adsorption and condensation) depending on the ratio of the temperature characteristics of the acylated monomer and the liquid phase carrying the acylating monomer. Analysis of the proposed versions of the mechanism allows you to make an engineering decision on the expediency of organizing a cycle in the liquid phase. Possible criteria for predicting the versions of the mechanism and examples of reaction systems with condensation and absorption versions of polyamidation are given.