Depolymerization of poly(ethylene naphthalate) in fused silica capillary reactor and autoclave reactor from 240 to 280°C in subcritical water

Abstract

Depolymerization of poly(ethylene naphthalate) (PEN) in subcritical water was performed in a fused silica capillary reactor (FSCR) and an autoclave reactor. The phase behaviors of PEN in water during the heating-cooling process in the FSCR were observed under microscope and images were captured by digital camera. Reaction conditions for PEN hydrolysis in the autoclave reactor were chosen based on the experimental results obtained from the FSCR. Under autogenous pressures in the autoclave reactor, the effects of the water/PEN mass ratio (8.0 g/1.0 g to 16.0 g/1.0 g), reaction temperature (240-2808C) and reaction time (5-60 min) on the depolymerization yield and products yields were investigated. The main products of depolymerization were identified and quantified as 2,6naphthalene dicarboxylic acid (2,6-NDA) and ethylene glycol (EG). PEN was completely depolymerized at 2608C in 60 min with an optimal water/PEN mass ratio of 12.0 g/1.0 g (12:1). The yields of 2,6-NDA and EG were optimized to 83.1% and 79.7%, respectively. Reaction kinetics analysis showed that the PEN depolymerization in subcritical water was first-order and the activation energy was 95 kJ mol 21 . Additionally, a reaction pathway was proposed based on the experimental results. POLYM. ENG. SCI.,

Preparation of High‐Purity 2,6‐Naphthalenedicarboxylic Acid from Coal Tar Distillate

“…2,6‐Naphthalenedicarboxylic acid (2,6‐NDA) and its dimethyl ester dimethyl‐2,6‐naphthalenedicarboxylate (2,6‐NDC) are recognized as significant monomers for preparing a variety of high‐performance polyesters, polyurethanes and liquid crystal polymers , especially polyethylene naphthalate (PEN) . Since the two condensed aromatic rings of PEN have a stronger conjugation effect than the benzene ring, due to their larger planar structure, PEN features more remarkable performance with regard to physical characteristics, mechanical properties, heat resistance, and gas barrier properties, with stronger molecular chain rigidity, compared with polyethylene terephthalate (PET) . Thus, PEN can be widely applied to the production of packaging, airbags and fibers and in the engineering plastics industry, and it is highly expected to be the next industrial material to replace PET for its dramatically increasing demand , .…”