KraussMaffei’s Innovative Lignin-PLA Blend

Together with the Polish member of the Cypriot Synergy Horizon Group, KraussMaffei Extrusion GmbH, Laatzen, Germany, has now developed a process for producing a 100% bio-based reinforced thermoplastic: lignin-reinforced PLA.

Lars Darnedde, process engineering development and project manager at KraussMaffei Extrusion, commented:
“With our compounding expertise and our project partner’s unique knowledge of lignin preparation, we have succeeded in incorporating up to 30% lignin into the PLA matrix and producing a compound with natural antioxidant capacity/activity, enhanced mechanical properties, and controlled biodegradability,”

With a focus on hydrolysis lignin valorisation, the Synergy Horizon group of companies transforms lignin, a biopolymer often discarded as a by-product of the bioethanol industry, into valuable products for various applications. Their strong competencies involve lignin purification, its chemical modification and functionalisation. They offer lignin-derived products for various applications, such as oil and gas extraction, battery production, water treatment, animal feed, etc.

From Waste Product to Filler

The group member, Synergy Horizon Poland Sp. z o.o. has also recently developed a process at its Polish site in Poznan to produce free-flowing lignin powder that can be metered into the extruder as a filler. Lignin is a 100% natural substance that is second to cellulose, the most abundant organic material on Earth. Lignin can be extracted from lignocellulosic biomass by various methods.

One of these methods is biomass hydrolysis for bioethanol production, which generates hydrolysis lignin as a byproduct. Hydrolysis lignins have unique properties that make them stand out from other types of lignin. Around 50 million tons of lignin, including hydrolysis lignin, are produced annually worldwide as a waste product from wood processing in the paper and bioethanol industries, 98% of which is incinerated. Various research projects have already dealt with the valuable renewable bioresource, but its use as a filler in a biopolymer matrix is so far unique.

“However, processing hydrolysis lignin is not an easy task,” knows Alexander Gonchar, the head of research and development at Synergy Horizon, and is proud of the fact that, thanks to intensive development work, his company now operates a commercial production line for manufacturing lignin powder.

Successful Process Optimisation: KraussMaffei Integrates up to 30% Lignin into PLA Matrix

KraussMaffei has demonstrated incorporating natural raw material into the PLA matrix in its newly established technical centre at the Laatzen site. The laboratory extruder, a ZE Blue Power 28, and the small ZE Blue Power 42 production compounder incorporated up to 30% lignin.

Lars Darnedde gives an insight into the process configuration.
“We have specially adapted the screw configuration to the lignin with heavy-sensitive mixing elements, operate at a low temperature of 160°C maximum, and use both a 6 D-long filling zone and side degassing,” 

The ZE BluePower generation, with its optimum Da/di of 1.65, offers all these possibilities “out of the box”. It is thus ideally suited for processing these shear- and temperature-sensitive polymers.

The fact that the process arrangement of the compounding extruder and the preparation of the lignin at Synergy Horizon is perfect has also been confirmed by extensive mechanical tests. Compared to pure PLA, the lignin reinforcement increases flexural and tensile modulus by around 30%. It could be helpful in packaging applications where the material needs to be stiff enough to hold its shape under load. Another advantage is that lignin adds sufficient antioxidant capacity that can help, particularly in food packaging applications, to prevent oxidation of the food and maintain its quality and safety by inhibiting the radical oxidation and preventing the formation of off-flavours, odours or toxic compounds. Moreover, the biocompound with lignin has no odor unlike other lignin, making it more suitable for food packaging.

A novel bicompound that exhibits antioxidant properties could be applied to biodegradable plastics such as mulch films for agricultural purposes to protect them from oxidative degradation.

Unlike pure PLA, which has limited biodegradability due to its dependence on specific enzymes and industrial conditions, PLA biocompounds containing lignin exhibit enhanced biodegradation properties with a more than 90% biodegradation rate in 99 days.

Read more news from KraussMaffei here.

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