Development of industrial sugar structures for application in the packaging industry

Plastics and polymers are part of several products, applications and processes in our modern every day life. Decreasing availability of fossil resources providing the basis for the production of plastics and polymers will eventually lead to a process of rethinking and investigating new feedstocks and resources for keeping up with the increasing demand for functional products. Additionally, an industry working with more and more sustainable, renewable and biodegradable educts is necessary to tackle the increasing environmental pollution by mishandled wastes, CO₂ emissions and thus resulting global warming. The development of utilizing such sustainable, renewable feedstocks lays the foundation for the research done in this PhD work. By valorizing the residue depectinized apple pomace from food producing industry a third generation utilization path is developed to have value adding products from this feedstock as far as possible. Using an eco friendly water based percolation extraction process at subcritical conditions elutes the desired biopolymers hemicellulose and partially cellulose from the depectinized apple pomace leaving an uncontaminated residual for further use. About 30% of the input biomass was dissolved in the process containing 5-7% precipitable hemicellulose (≈50% of total extractable content by hot-water extraction) and by-products like carboxylic acids, polyphenols, protein, fat, waxes and fibers. The most suitable conditions for extracting hemicellulose at high purity with a satisfying yield were found at 145 °C for 90 min followed by ethanolic precipitation at 70% (v/v) ethanol concentration resulting in ≥ 90% purity. The aim, a product comparable to chemical pulp regarding purity, was reached within this development. To tailor extracted hemicellulose for specific requirements in different applications a depolymerization step as well as a chemical modification was developed. Depolymerization was carried out using sulfuric acid as catalyst in a homogeneous reaction system. While depolymerizing hemicellulose different kinetics were observed and investigated by analyzing the decrease of molar mass depending on the reaction time. It was found, that initially a fast reduction of chain length occurred following k₁ succeeded by a slower hydrolyzation into low-molar mass oligomers (k₂). The total depolymerization kinetics were found to be second order for this homogenous reaction system. By depolymerization the water-solubility and requirements for applicability of depolymerizate in following functionalization for coating, lacquer and ink applications was reached and sulfate contamination was removed by precipitation of BaSO₄ during the neutralization step with Ba(OH)₂ instead of NaOH. The etherification with a tertiary amine was conducted with hemicellulose to introduce a solubility enhancing functional group to the polymer. By the formation of tertiary and tertiary quaternary tandem groups a cationic charge was introduced resulting in a product similar to cationic starch. The study investigated reaction parameters for etherification resulting in a large saving potential regarding input amine, reaction time and temperature (energy equivalents), while the incorporation of the modified hemicellulose will be investigated in following projects.