'High Viscosity Polyester - New Solid and Melt Phase Process Approaches'

The production processes for high viscosity polyester are driven by two fast growing market segments the packaging materials especially the polyester bottles and the technical yarn production. Both areas are fortunately excluded from Chinese polyester fiber predominance yet and growing round the World between 6 and 12%/a. Not to forget PET-foam this is growing fast but from a lower level. It is interestingly to observe in this development area the antagonism between plain process economy and complex process comfort which is finally and also part of the overall economy for the consumer. And it is becoming more complicated when IV lift up and removal of acetaldehyde are depending each other which is the case especially in all packaging applications. If we are asking for the eligible innovations in high IV PET production processes we can easily count a hand full. The most important are;

• Reduction of conversion cost, mainly labor and energy consumption
• Increase of single line unit capacities safely above 1000 t/d
• Increase of line flexibility
• Reduction of undesired side products like AA or dust
• Improvement of quality like reduced IV fluctuation and lower crystallinity

The problem of this whish list is that some topics are ostensible controversy. But main target of innovation is to solve such extremes applying innovative new technical approaches.

The new developments we can classify in the following categories:

1)       New SSP processes and further developments

• The new horizontal SSP process
• Further developed state of the art SSP (disadvantage of existing technology and new approaches)

2)       High viscosity resin without SSP and its further treatment

• Technology status of different vendor companies
• Direct crystallization and AA removal

3)       Direct converting of melt to preform or yarn

• Advertised direct performing processes of Uhde-Inventa-Fischer and ZIMMER-AG
• AA-scavenger - the still existing hurdle
• Direct spinning of tire cord

 

4)       What public is able to distill from limited available information base about IntegRex?

1. New SSP processes and further developments

• The new horizontal SSP process

Until last year capacity increase of SSP above 1000 t/d in one single line was still a dream because tube reactor diameter and reactor height are inherently at a capacity of 700 t/d at the physical limits. Especially plug flow conditions and even gas distribution are becoming in such a huge vertical tube reactor an increasing problem not to mention the time until the process is running under steady state conditions which is connected to inflexibility regarding throughput and IV-change. A new invention in this field came with the patent publication

WO 2004/018541[1] where a completely new way of material flow is suggested. When state of the art continuous SSP exists of a vertical tube reactor where the polymer chips are moved by gravity flow from top to the bottom under counter current nitrogen flow the new process is suggesting the principle of inclined rotary kiln which is mechanically a matured technology of the cement industry. The polymer particles are gently moved by gravity differences triggered by slow rotation of the reaction tube whereat the reaction gas is flowing over the steadily renewing granulate bed surface and removing the split off products like water and glycol. It is to prescind that in difference to the vertical tube reactor the plug flow conditions of a kiln type reactor is comparable to a series of large numbered equal sized back-mix tanks. The principle is demonstrated in figure 1.