Entwicklung eines reaktiven Extrusionsprozesses zur ...
Entwicklung eines reaktiven Extrusionsprozesses zur ...
Entwicklung eines reaktiven Extrusionsprozesses zur ...
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8 Zusammenfassung/Summary 127<br />
and combine the different properties of amides and esters. The ester and amide amount<br />
in the polyesteramides as well as their properties can be influenced and controlled<br />
chemically during their synthesis. Especially for biomedical applications polyesteramides<br />
are considered to be an important material. As they are surface eroding polymers, they<br />
are not causing a local in vivo acidity during their degradation and hence are, compared<br />
to other polymers which are used for such devices, avoiding inflammatory responses of<br />
the body.<br />
In this work the synthesis of a polyesteramides with good thermal, mechanical and<br />
processing properties, by using reactive extrusion, is being developed. The focus thereby<br />
lies on the synthesis of thermoplastic polyesteramides. These are mainly produced by<br />
batch synthesis and could not achieve an importance on the market up to now. In<br />
literature examples for the preparation of polyesteramides on a twin-screw extruder using<br />
the monomers ε-caprolactam and ε-caprolactone were reported, but this process has not<br />
achieved any industrial relevance so far. In this work a new synthesis approach for the<br />
continuous synthesis of polyesteramides is presented, which is based on the anionic ring<br />
opening polymerization of ε-caprolactam in the melt of commercially available polyester<br />
- polycaprolactone. The amide fragments are incorporated into the polyester via a chain<br />
transfer reaction during polymerization, which leads to polyesteramides with blocky<br />
nature. As the melt viscosity before and after the polymerization reaction, is comparable,<br />
the process design can easily be simplified, which allows an easier scale-up.<br />
The first part of this work is focused on the chemical development of the reaction and<br />
its evaluation. Furthermore, the requirements for the synthesis on a twin-screw extruder<br />
as well as the required properties of the extrudate and the polymer for such a processing<br />
are defined. To assess and optimize the synthesis the reaction was performed on a<br />
twin-screw microcompounder in batches. The influence of the chemicals and how to<br />
conduct the process, especially regarding temperature and reaction progress are studied.<br />
The characterization of the resulting polymers allowed their subsequent evaluation, and<br />
thus the assessment and evaluation of the chemical reaction and the process. At reaction<br />
temperatures of 180 °C and residence times of ten minutes polyesteramides with blocky<br />
structure were synthesized at high conversion rates. For one of the studied mixtures the<br />
synthesis was carried out continuously on a laboratory extruder with a screw diameter of<br />
16 mm and a L/D=25. The focus lay on the development of the process control as well<br />
as the screw design. Calculations to determine the residence time of the polymer using<br />
a simulation program were performed in order to avoid time-consuming experiments