Figure1: "WO2004/018541 - Continuous Process for Solid State Polymerization of Polyesters"

For the treatment of even small sized granules of low IV-precursor which are additionally abrasion sensitive and brittle the same inventor suggested in WO 2004058852 a reactor containing a serial of fluid beds which is providing with its limited bed heights a gentle treatment together with intensive gas exchange [1]. Figure 2 is showing the schematic principle.

Figure 2: "WO2004058852 Reactor and process for Solid State Polymerization of Polyethylene Terephthalate"

Unlike other inventions which need a lot of time between publication and technical realization the interested professional could read in public papers [2], that M&G head of technology Giudo Ghisolfi talked during Nova-Pack -January 2005 (Bal Harbour, Miami, USA) about the new kiln reactor type SSP of a capacity above 1000 t/d . And he already announced this technology named "EasyUp" as proprietary to M&G. Meanwhile an industrial sized Horizontal (kiln type) SSP has already been successfully started-up in one of M&G PET production sites since June 2005 [3]

• Further developed state of the art SSP

One hurdle of the common SSP technology is dust generation especially during second crystallization. Mainly the mechanically moved horizontal crystallizers are not able to treat the polymer pellets as gentle as desired and especially at the peripheral rim and near the stirrer mechanical forces are high. To overcome this problem a new kind vertical second crystallizer is described in WO 03046045 [1]. The improved process exists of a first fluid bed crystallizer which is about state of the art and a second crystallizer which is vertical and the top part of the crystallizer is gently moved by a specially shaped stirrer. By an optimal L:D selection of the crystallizer tube diameter vertical flow movement and horizontal agitation complementing each other which guides to a minimum of mechanical forces. Another feature is the spitted gas movement in the crystallizer tube by introducing the gas into the agitated area and split the flow in an up and downwards portion. The new process should generate less dust and provides further advantage to use the second crystallizer volume as additional SSP space. In figure 3 the crystallizer is demonstrated.