Solid‐state polymerization of poly(ethylene terephthalate)

Abstract

Solid-state low molecular temperature. Synopsispolymerization of poly(ethy1ene terephthalate) (PET) is carried out by heating the weight prepolymer at temperatures below its melting point but above its glass transition Postcondensation occurs and the condensation byproducts can be removed by applying vacuum or inert gas. Polymers obtained usually have high molecular weight, low carboxyl and acetaldehyde content, and can be used for beverage bottle or industrial yarns. Polyesters for textile purposes are manufactured by a melt process. Chemical reactions involved in the solid state polymerization are transesterification, esterification, as well as the diffusion of byproducts. Overall reaction rate was governed by the molecular weight, carboxyl content of prepolymer, crystallinity, particle size, reaction temperature, and time. Prepolymer for solid state polymerization should have intrinsic viscosity 0.4 dL/g or more, density 1.38 g/mL, and minimum dimension 3 mm or less. The reaction temperature could be 200-250OC. When textile grade PET is used as prepolymer, crystallization at 180-190°C for 1-2 b increases the density to 1.38 g/mL. Polymerization at 240-245°C for 3-5 h can raise the intrinsic viscosity to 0.72 dL/g and carboxyl content less than 20 meqkg. Appropriate reaction conditions are subject to the properties of prepolymers and the'design of reactors. Reactor used for solid state polymerization could be vacuum dryer type or stationary bed. The former is suitable for a small capacity and is run batchwise. The latter is a continuous process and is economically feasible for large-scale production.

The chemistry, manufacture and tensile behaviour of polyester fibers

“…Since the reaction temperature is below the melting point (SPP), the chips do not fully sinter together and the lower reaction temperature constrains degradation reactions. The polymerization rates are here higher due to the shorter diffusion path in smaller particles [31,32]. It was found that the rate of SSP increases with increase of catalyst concentration within the range 0-100 ppm Sb in starting chips [18].…”

Diffusion of Ethylene Glycol in Solid State Poly(ethylene terephthalate)

“…It was reported SSP is controlled by diffusion when the PET particle size is greater than 100 mesh and the temperature is higher than 210°C whilst at a lower temperature (l 60°C) the reaction becomes the rate-controlling step. 2 In the temperature range of 160-210°C, SSP is controlled by both diffusion and reaction. However, it is clear that even above 210°C the reactions can not be totally neglected since 220 reversible condensation reactions are not at equilibrium at any instance due to the deficiency of byproducts.…”

Response Surface Analysis for Competition between Thermooxidation and Polycondensation Reactions of PET Flakes. Part 1: Low Vacuum Atmosphere

“…These effects could be emphasized the higher polymer diffusivity inside the polymer matrix, i.e., the higher the process temperature for the same geometry (thickness=radius) of the reacting particles and the same initial ratio of hydroxyl to carboxyl end groups of PET flakes [12,[18][19][20][21][22] . Additionally, the reduced rate of increase in [g] at 230 C should be related to side reactions effects [23] and to the thermal behavior of the samples utilized, which exhibited a large range of crystals fusion temperature (Fig.…”