Polymerisation Reuse

This involves subjecting a polymer, such as PMMA, in solid, gel, partially molten or molten form to microwave heating for a time and at a temperature sufficient to decompose the polymer to produce a monomer or monomers in gaseous, liquid or solid form, without substantial decomposition of the monomer or monomers, and recovering at least one of the monomer or monomers. The monomer or monomers may then be reused for polymerisation. 

Examples of aqueous-organic catalyzed reactions include oxidations,8 polymerisations,9 hydrogenations,10 hydroformylations,11 C—C coupling,12 and olefin metathesis.13,14 The use of water as a solvent for conducting biphasic catalysis has many advantages it is cheap, easily purified, readily obtained, and disposed. The main drawback is that trace amounts of organic compounds dissolved in water are difficult to remove, although this does not tend to be a problem when the aqueous-catalyst phase is reused repeatedly for the same reaction. 

A complete process chain for moulded parts made of PA6 is shown in Fig. 1.2. PA6 is synthesized in a polymerisation step from the monomers caprolactam and water. The production of caprolactam itself can be traced back to benzene which is isolated from crude oil or formed from crude oil in a cracking process. The polymer melt is degassed from unreacted monomers and then further processed to condition it for the manufacturing of semi-finished products and of moulded parts. The poljmier material in the moulded parts may be eventually recycled and reused in the polymerisation after a polymer degradation reaction has been carried out. 

In order to facilitate the separation of the enzyme and the polyester after polymerisation, Loeker and co-workers placed the enzyme beads in a small wire filter pot at the bottom of the autoclave (Loeker et al, 2004). After removal of PCL, the filter pot was transferred to a second 60 ml autoclave mid attached to the shaft of the motor driven stirrer blade. The autoclave was then pressurised at 4,000 psi at 35 °C and the pot was spun at 4,500 rpm for 1 h in order to remove any residual polyester from the filter pot and to reuse it. The yield of the second polymerisation run can, however, decrease after cleaning due to partial leaching of enzyme. This phenomenon is not observed after the first polymerisation/ cleaning cycle, the enzymatic activity remaining basically constant for the following cycles. 

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