TAGS: Biobased Solutions
The recent development of new polymerization methods that allow the economical production of polylactic acid (PLA) with a higher molecular weight have effectively removed many of the limiting factors on its use, opening-up a greatly expanded application base for the plant-based bioplastic.
New Method Allows Economical Production of PLA
Sulzer has developed a turnkey process with partners to produce PLA from sugars via lactic acid followed by a downstream dimerization and ring opening polymerization process that has already been installed and is operating in six distinct production facilities worldwide.
In the past, the usage of PLA, or plant-based bioplastic was limited by its mechanical properties in production (technically its viscosity in the melt), and by the thermo-mechanical properties of the finished product. The new processes solve both these issues and as a result extend its economic use to a much wider spread of consumer goods and packaging applications.
Benefits such as its low toxicity, along with better sustainability as a result of using renewable resources as raw materials make the new grades of PLA an ideal material for the food packaging and consumer product industries. Due to a high level of robustness, biocompatibility and sterilization options they are also suitable for a number of medical applications such as implant devices, tissue scaffolds and internal sutures, plus a wide variety of other pharmaceutical devices and packaging applications.
Torsten Wintergerste, division president from Sulzer Chemtech comments, “The latest grades of PLA are highly flexible and have a much wider scope of useable properties, making them ideal for all these plastics production methods.”
How the New Grades of PLA are Produced
PLA can be produced starting with hydrolyzed starch or sucrose transformed to lactic acid (2-hydroxy propionic acid) building blocks, which exist in optically active D- or L-enantiomers. Depending on the proportion of the enantiomers, PLA with different properties can be produced.
This enables the development of multiple processing methods to produce a wide range of PLA grades with properties suitable to differing applications. The differences are based on molecular weight and content of D-lactic acid units. The molecular weight affects the rheological properties (viscosity in the melt), whereas the content of D-lactic acid units affects thermo-mechanical properties.
PLA with a high molecular weight is one of the main drivers for the economical production and consequent expanded use of this polymer. There are two methods to prepare PLA: the condensation of lactic acid and the ring opening polymerization of lactide, however the latter is the one preferred by Sulzer engineers as it provides improved control over quality and more flexibility in terms of the material properties of the end product.
Sulzer can design and execute whole projects, from the first concept to an industrial scale plant using in house engineering, equipment, assembly, commissioning, and start-up capabilities. This allows PLA producers to enter into the biopolymer market with the capacity to produce the new formulations at a customizable scale.
Source: Sulzer