Carbonyl Bis l-caprolactam

During this reaction, some caprolactam is also liberated. The reaction is largely completed within the processing time (typically 3-5 min). The increase in intrinsic viscosity of PET can be adjusted by the amount of CBC. In practice, about 0.5 wt% of CBC is typically used. CBC is commercially available under the trade-name ALLINCO (DSM, Geleen, The Netherlands). ALLINCO is one of the most effective chain extender systems available for PET [21, 22], CBC is often used in combination with PBO for an enhanced chain extension effect. Typically, the relative viscosity of PET is increased from 1.6 to 2.0 with a stoichiometric amount of CBC + PBO (ca. 1.2 wt%) in a single-screw extruder at 300 °C. 

PET is a material that finds widespread use for soft drink and beverage bottle applications. For injection or blow moulding applications, high-molecular-weight 

Solid-state polycondensation (SSP) is thus a technique applied to thermoplastic polyesters to raise their molecular weight or IV. During solid-state polycondensation, the polymer is heated above the glass transition temperature and below the melt temperature of the polymer either under an inert gas or under vacuum. Increasing the intrinsic viscosity requires a residence time of up to 12 h under vacuum or under inert gas, at temperatures from 180 to 240 °C. 

PET is a material that finds widespread use for soft drink and beverage bottle applications. For injection or blow moulding applications, high-molecular-weight PET Mn 30000 is required. While PET with of 15 000 — 25 000 can be achieved by a standard melt-polymerization process, the high-molecular-weight PET grades require a solid-state polymerization process. Commercial solid-state polymerization process systems are usually composed of a crystallizer and a polymerization reactor. First, melt-polymerized chips are fed into the crystallizer unit and crystallized to the extent of about 40 %. In a second step, tlie crystallized chips are fed into a polymerization reactor vessel and then polymerized in the solid state at a temperature of around 220 °C. 

Typically, an IV enhancement of O.lOdL/g requires lOh of solid-stating. In the presence of an SSP accelerator, diis time is reduced to just 5 h. Irgamod 1425 also contributes to reduced yellowing of die PET resin. For instance, 0.1 wt% can lead to a chop ill b value (yellowness) from 1.1. to —2.9. Such SSP accelerators are based on sterically hindered hydroxyphenylalkylphosphonates such as calcium bis-ethyl-3,5-ch-r-butyl-4-hychoxyphosphonate. Pfaendner et al. [24] details the use of Irgaiiox 1425 (CAS 65140-91-2) to accelerate the solid-stating of PET. 

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