Bio-Adipic Acid for Manufacturing PA 66
Researchers at the University of the Saarland are working on how to obtain adipic acid from lignin by means of biotechnological methods. Together with 1,6-diaminohexane, adipic acid is an important starting material for producing PA 66. Production of adipic acid from fossil resources reportedly requires a great deal of energy. For this reason, the research group would hopes to use plant-derived lignin instead of petrochemical resources as the starting material.
Lignins are biopolymers based on aromatic molecular building blocks linked together in many different ways. They are stored in the cell wall of plants and increase the strength of the plant tissue. Evergreens have a lignin content of about 30%. Large quantities of lignin occur as a by-product in the course of producing paper and cellulose.
The objective is to convert this residual lignin into a precursor of adipic acid with the aid of bacteria. The product of the bacteria's metabolism would then be converted into adipic acid via hydration. In the coming years, the yield of the process and the purity of the resultant product would then be optimized to a point permitting industrial use of the method.
Polyamides based on renewable resources have been available on the market for quite some time. Polymerization of these semi-bio-based polyamides, e.g. PA 410 or PA 610, uses sebacinic acid, which can be obtained from castor oil. An important starting point is to use omega-aminolauric acid (ALS) from biological sources as a replacement for the petroleum-based laurin lactam in the production of PA 12.
Bioplastics still represent a relatively small fraction of the overall plastics market. According to one recently published market analysis, global consumption of bioplastics could grow at an annual rate of approx. 19% in coming years. By the year 2021, sales of bioplastics worldwide are expected to reach almost 6 billion USD. The study points to the increased competitiveness of bioplastics versus conventional plastics as the result of improved technical properties and a significant increase in production capacities.
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