Solid Polymerization of Nylon 66 -Study on the Polymerization of Nylon. II.-

Abstract

Superhigh-molecular-weight Nylon is required for extrusion of film, rod, etc., which can not be produced through melt polymerization. Solid polymerization of Nylon 66 pellet has been studied under the condition of heating temperatures of 210-460°C in vacuum from the view points of production of such superhigh-molecular-weight polymer and of the possible heterogenuity of molecular weight caused by solid phase reaction.
Relative viscosity of the polymer increases linearly with heating time (Fig.3) and apparent activation energy of 26 kcal/mol is calculated. Polymer with relative viscosity of 500 or more (mol. wt. of 100000 or more) can be produced without difficulty. By remelting the polymer which is obtained at higher temperatures (≥200°C) shows decrease of relative viscosity, while relative viscosity increases in the polymer yielded at lower temperature (Table 2). Polycondensation equilibrium constant drops as temperature increases, i. e., relative viscosity of the polymer in equilibrium of solid polymerization shall decrease by remelting. Experimental result shows that the polycondensation reaction is behind the speedy drying of the pellet at lower temperature and becomes to follow the drying at higher temperature.
Relative viscosity distribution in the radius direction of pellet, test rod with 15 mm diameter and commercial extruded rods has been measured. All of the commercial rods have higher relative viscosity in the central part than the surface (Table 4). The test rod after solid polymerization of 170°C, 60 h shows similar viscosity distribution.
However, the test rods polymerized at 210°C show higher value both in central part and outer surface (Fig.5). These distribution may be caused by slow heat transfer at the beginning of heat-up and at cool-down. Such viscosity distribution cannot be observed in the industrial pellet (Table 3).