Entwicklung eines reaktiven Extrusionsprozesses zur kontinuierlichen Herstellung von Polyesteramiden

The material class of biopolymers attracts increasing attention and is considered as a promising development in the plastics industry. In particular, the degradable polymers play an important role due to their environmentally friendly properties and the wide range of applications for which they can be deployed for. These range from biodegradable packaging to biomedical devices. Polyesteramides belong to the class of biopolymers and combine the different properties of amides and esters. The ester and amide amount in the polyesteramides as well as their properties can be influenced and controlled chemically during their synthesis. Especially for biomedical applications polyesteramides are considered to be an important material. As they are surface eroding polymers, they are not causing a local in vivo acidity during their degradation and hence are, compared to other polymers which are used for such devices, avoiding inflammatory responses of the body. In this work the synthesis of a polyesteramides with good thermal, mechanical and processing properties, by using reactive extrusion, is being developed. The focus thereby lies on the synthesis of thermoplastic polyesteramides. These are mainly produced by batch synthesis and could not achieve an importance on the market up to now. In literature examples for the preparation of polyesteramides on a twin-screw extruder using the monomers epsilon-caprolactam and epsilon-caprolactone were reported, but this process has not achieved any industrial relevance so far. In this work a new synthesis approach for the continuous synthesis of polyesteramides is presented, which is based on the anionic ring opening polymerization of epsilon-caprolactam in the melt of commercially available polyester-polycaprolactone. The amide fragments are incorporated into the polyester via a chain transfer reaction during polymerization, which leads to polyesteramides with blocky nature. As the melt viscosity before and after the polymerization reaction, is comparable, the process design can easily be simplified, which allows an easier scale-up. The first part of this work is focused on the chemical development of the reaction and its evaluation. Furthermore, the requirements for the synthesis on a twin-screw extruder as well as the required properties of the extrudate and the polymer for such a processing are defined. To assess and optimize the synthesis the reaction was performed on a twin-screw microcompounder in batches. The influence of the chemicals and how to conduct the process, especially regarding temperature and reaction progress are studied. The characterization of the resulting polymers allowed their subsequent evaluation, and thus the assessment and evaluation of the chemical reaction and the process. At reaction temperatures of 180 °C and residence times of ten minutes polyesteramides with blocky structure were synthesized at high conversion rates. For one of the studied mixtures the synthesis was carried out continuously on a laboratory extruder with a screw diameter of 16 mm and a L/D=25. The focus lay on the development of the process control as well as the screw design. Calculations to determine the residence time of the polymer using a simulation program were performed in order to avoid time-consuming experiments with „trial-and-error“ principle. After optimization and configuration of the screw it was possible to transfer the synthesis of the mixture synthesized in the microcompounder to a laboratory extruder process resulting in comparable analytical results. The work contributes to the continuous synthesis of polyesteramides by reactive extrusion. Furthermore it points out that the material class of biopolymers and in particular of polyesteramides still offers a great research potential.